Yemen Highway Design Standards (1986)

1-

YEMEN ARAB REPUBLIC

DEVELOPMENT OF NATIONAL HIGHWAY lv1ASTER PLAN

DESIGN STANDARDS

Dar Al-Handasah Consultants (Shair & Partners ) Sana'a AVa3)

Beirut London Cairo FEBRUARV 1986

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Table of Contents

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T ABLE OF CONTENTS

INTRODUCTION

SECTION 1: BASIC GEOMETRIC DESIGN STANDARDS 1-1

1.1 General 1-1

1.2 Classification of Road Categories

and Terrain 1-1

1.2.1 Road Categories 1-1

1.2.2 Terrain 1-2

1.3 Design Speed 1-3

1.4 Roadway Capacity 1-3

SECTION 2 : GEOMETRIC CROSS-SECTION 2-1

2.1 Cross-Sectional Elements 2-1 c

2.1.1 Travel Lanes 2-1

2.1.2 Shoulders 2-1

2.1.3 Median 2-1

2.1.4 Cross-Slopes 2-4

2.1.5 Sidewalks 2-4 1" 2.1. 6 Side-Slopes 2-4

2.1. 7 Slope Benches 2-4 l' 2.1.8 Side Ditches 2-5

2.2 Clearances 2-5

'f 2.2.1 Right-of-Way 2-5

2.2.2 Structural Clearances 2-6

f SECTION 3 : GEOMETRIC DESIGN STANDARDS 3-1

T 3.1 Sight Distance 3-1

3.1.1 General 3-1

T 3.1.2 Stopping Sight Distance 3-1

3.1.3 Passing (Overtaking) Sight -~ Distance 3-2

3.1.4 Sight Distances on Horizontal

;f Curves 3-3

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3.1.5 Sight Distances on Crest Vertical I Curves 3-3

3.1.6 Sight Distance on Sag Vertical I Curves 3-5

3.2 Superelevation 3-7 I 3.2.1 General 3-7

3.2.2 Superelevation Rates 3-7 I 3.2.3 Curvature 3-8

3.2.4 Development of Superelevation 3-8 I 3.3 Horizontal Alignment 3-9

3.3.1 General Controls 3-9

I 3.3.2 Standards for Curvature 3-12

3.3.3 Consistency of Alignment 3-12

3.3.4 Alignment at Bridges 3-12 il 3.3.5 Transition Curves 3-13

3.3.6 Widening on Curves 3-13 I 3.4 Vertical Alignment 3-14

3.4.1 General Controls 3-14 I 3.4.2 Grade Standards 3-15

3.4.3 Position of Grade Line 3-16 I 3.4.4 Critical Grade Length and

Clim bing Lanes 3-16

I SECTION 4: FLEXIBLE PAVEMENT DESIGN 4-1

I 4.1 General 4-1

4.2 Traffic 4-1 )1 4.3 Pavement Design Methods 4-2

4.3.1 Shell Method 4-2 I 4.3.2 AASHTO Method 4-4

4.4 Bituminous Concrete Mix Properties 4-6

I 4.4.1 AsphaltS 4-6

4.4.2 Gradation 4-6

4.4.3 Job-Mix 4-7 I I I I

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SECTION 5: HYDROLOGY AND HYDRAULICS OF DRAINAGE

STRUCTURES 5-1

5.1 Hydrology of a Drainage Basin 5-1

5.2 By drological Determinations 5-1

5.2.1 General 5-1

5.2.2 Method of Judgement 5-1

5.2.3 Method of Formulae 5-2

5.2.4 Method of Direct Otservation 5-2

5.2.5 Method of Correlation Analysis 5-2

5.2.6 Method of Hydrograph Synthesis 5-2

5.3 Recommended Hydrological Methods 5-3

5.3.1 Rational Method 5-3

5.3.2 Modified Talbot Method 5-10

5.3.3 Slope Area Method 5-13 .--,

5.4 Basic Criteria for the Hydraulic Design of

Bridges 5-13

5.4.1 Location 5-14

5.4.2 Design Higp Water Level and

Bridge Height 5-14

5.4.3 Free Board 5-14

< 5.4.4 Length of ,Bridgeworks 5-15

5.4.5 River Type and Characteristics 5-16

5.4.6 Basic Data 5-16 ,-5.4.1 Bridge Scour 5-16

5.4.8 Guide Banks 5-18 ,-

5.5 Basic Criteria for the Hydraulic Design

of Culverts 5-19

f" 5.6 Basic Criteria for the Hydraulics of the

Roadside Drainage Channels 5-26

r 5.7 Irish Crossings 5-28

5.8 Spillways 5-30

r SECTION 6: ROAD MARKINGS AND FURNITURE 6-1

r 6.1 Road Markings 6-1

6.1.1 General 6-1

6.1.2 Colour 6-1

6.1.3 Road Marking Materials 6-2

f 6.1.4 Road Markings 6-2

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6.2 Traffic Signs 6-10 6.2.1 Regulatory Signs 6-10 6.2.2 Warning Signs 6-10 6.2.3 Informatory Signs 6-13 6.2.4 Siting, Orientation and [

Foundations 6-13 6.3 Guard Rails and Crash Barriers 6-14 [ 6.4 Hazard Markers 6-20

SECTION 7: STRUCTURES 7-1

7.1 Introduction 7-1 7.2 Concept 7-1 - 7.3 Loading 7-1 7.4 Bridge Location 7-2 - 7.5 Bridge Superstructures 7-4 7.6 Bridge Substructures 7-10 - 7.7 B ridge Articulation 7-10 7.8 Other Bridge Components 7-14 7.9 Width of Carriageway on Bridges 7-19 7.10 Retaining Walls 7-20 7.11 Drainage Culverts 7-20 -

SECTION 8: GEOTECHNICAL CONSIDERATIONS 8-1 -8.1 General 8-1

J - 8.2 Site Investigation 8-1 8.2.1 Structures 8-1

- 8.2.2 Pavements 8-1 J 8.2.3 Materials 8-2

8.3 Embankments 8-4 J - 8.4 Retaining Structures 8-4

8.5 Cuts 8-5

I .-8.5.1 General 8-5 8.5.2 Slope Stability 8-5

8.6 Sand Dune Areas 8-10 I 8.6.1 General 8-10 8.6.2 Road Alignment 8-11 8.6.3 Sand Accumulation 8-12 8.6.4 Construction and Protection 8-13

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INDEX OF TABLES

TABLE NO.

1.1

1.2

3.1

3.2

3.3

3.4

3.5

3.6

Minimum Design Sp~4!9S (kph)

Flow Levels

Sight Distance Standards

K Values for Crest and Sag

Vertical Curves

lVIinimum Radii forJd~um Superelevation Rate.«

Superelevation Runoff Slopes

Relative Values of 'A1 with Design Speed <,; ..

:' .... '.

Travelled Way Widening Values

3. '1 . ,Road Gradients

4.1

4.2

5.1

5.2

5.3

5.4

Gradings of Minerai;4\ggregates

Bituminous Mixture Bequirements <I,'

Storm Design F1"eq~~~c1es Coefficients of Modifi~d Talbot Formula

(Years)

T,Manning'sRoughn~~·$.7Coefficient 'n' -.-'; .,

Permissible Velociti~!f·~;for . .'," ,'·,'c""

,"Channels with .. Ero~b,~e . Linings,

'Based on Uniform .• mijt·in Continuously Set, .A:~d Channels

8.1 .. Requirements forB~rlng Layout

8 . 2 'Requirements for Boring Depths

PAGE

1-3

1-4

3-3

3-6

3-8

3-9

3-13

3-14

3-15

4-6

4-7

5-10

5-12

5-35

5-36

8-2

8-3

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INDEX OF FIGURES

Figure No.

2.1

2.2

3.1

3.2a

3.2b

3.3

3.4

4.1

5.1

5.2

5.3

5.4

5.5

5.6

Cross-Sections - Dual Carriageway Roads

Road Cross-Sectional Elements

Horizontal Clearance for Stopping Sight Distance

Superelevation Details

Superelevation Details

Climbing Lanes

Truck Operation on Ascending and Decending

Grades

Relationship Between Pavement Damage and

Axle Load

Runoff Coefficient for Use in Rational Method

Isohyetals for Average Annual Rainfall (mm)

Rainfall Intensity - Duration - Frequency Curves

Rainfall Intensity Duration Frequency Curves

Rainfall Intensity - Duration - Frequency Curves

Nomograph for the Time of Concentration

2-2

2-3

3-4

3-10

3-11

3-1S

3-19

4-3

5-5

5-6

5-7

5-S

5-9

5-11

5.7 Headwater Depth for Concrete Pipe Culverts with

5.S

5.9

5.10

.. 5.11

Inlet Control 5-22

Head for Concrete Pipe Culverts Flowing Full

n = 0.011 5-23

Headwater Depth for Box Culverts with Inlet Control 5-24

Head for Concrete Box Culvert Flowing Full

n = 0.011 5-25

Nomograph for Solution of Manning's Equation for

Open Channel Flow 5-27

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5.12

5.13

5.14

5.15

6.la

6.1b

6.1c

6.1d

6.1e

6.2a

6.2b

6.2c

6.2d

6.2e

6.2f

602g

6.3a

603b

S.3c

6.3d

603e

6.3f

7.1

7.2a

7.2b

7.2c

7.2d

7.2e

7.3a

703b

704

7.5a

7.5b

Grouted Riprap Lined Ditch

Typical Detail of Irish Crossing

Irish Grossing Guide Bank

Typical Arrangement for Reinforced Concrete

Culvert Spillway

Road Marking Details





Regulatory and Informatory Traffic Signs

Warning Traffic Signs

Sign Face Details

Sign Post Location and Assembly Details



Details of Hazard Marker and Kilometre Post

Location of Guard Rails

Details of Guard Rail

Detail of Crash Barrier

Typical Deta1ls of Crash Barriers

Location of Crash Barriers

Location of Crash Barriers

Proposed B ridge Loading

Bridge Deck Types

B ridge Deck Types

Bridge Deck Types

Bridge Deck Types

Bridge Deck Types

Bridge Pier Types

Bridge Pier Types

Types of Bridge Abutment

Bridge Parapet Types

Bridge Parapet Types

5-29

5-31

5-32

5-34

6-3

6-4

6-5

6-8

6-9

6-11

6-12

6-15

6-16

6-17

6-18

6-19

6-21

6-22

6-23

6-24

6-25

6-26

7-3

7-5

7-6

7-7 7-8

7-9

7-11

7-12

7-13

7-15

7-16

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7.5c Bridge Parapet Types

7.6 Section Through Typical Elastomeric Expansion

Joint

7.7a Types of Retaining Wall

7.7b Types of Retaining Wall

7.8a Pipe Culvert Details

7.8b Pipe Culvert Details

7.8c Pipe Culvert Details

7.8d Pipe Culvert Details

7.8e Pipe Culvert Details

7.8f Pipe Culvert Details

7.8g Pipe Culvert Details

7.8h Box Culvert Details

7.8i Box Culvert Details

7.8j Box Culvert Details

7.8k Box Culvert Details

7.81 Box Culvert Details

7.8m Box Culvert Details

8.1 Gabion and Masonry Walls

8.2 Gabion Walls - Surcharged

8.3 Gabion Walls - Unsurcharged

8.4 Details of Side Slopes in Cut

8.5 Typical Roadway Section - Sand Dune Areas

7-17

7-18

7-21

7-22

7-23

7-24

7-25

7-26

7-27

7-28

7-29

7-30

7-31 ./

7-32

7-33

7-34

7-35

8-6

8-7

8-8

8-9

8-14

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Introduction

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INTRODUCTION

These standards outline recommended design criteria and procedures

for the design of roads and bridges in the Yemen Arab Republic

(YAR). It was prepared as part of the 'Highway Master Plan Study',

undertaken from 1984 to 1985. Its aims are to define and set design

standards, procedures, methods of details reJated to the different

categories of roads found in the Y AR.

The Standards wilJ serve as an Interim Guide to help achieve

uniformity in designs prepared for the Highway Authority. The

criteria, procedures. methods and details, outlined herewith, shall be

used in the absence of more detailed studies for specific conditions.

However, it shal1 not absolve designers of their responsibility to make

such additional studies as may be required in the preparation of any

specific design.

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. SECTION 1': Basic Geometric Desig,n Standards

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SECTION 1: BASIC GEOMETRIC DESIGN STANDARDS

1.1 GENERAL

This section deels specifically with the major details and classifications

relating to basic design standards and is intended to establish policies

for the design of highways. The overall objective of these policies is

to allow· the movement of the greatest number of vehicles possible,

with maximum efficiency, minimum hazard and at the same time remain

cost-effective.

As most of these policies and standards may be subject to amendment,

due to changes in conditions and terrain encountered at various

locations throughout the YAR, they should not be used as a

substitute for sound engineering judgement and experience.

1.2 CLASSIFICATION OF ROAD CATEGORIES AND TERRAIN

In the establishment of basic standards for future road improvement

construction, or upgrading, two main factors have been considered:

1.2.1

The categories of roads in the study network (classified by

function)

The different types of terrain, prevalent in the YAR.

Road Categories

There are three categories of road used in the study network, these

are:

Category A (Primary Roads)

Main transnational routes connecting governorate capitals, these

are asphalt surfaced.

Category B(Secondary Roads)

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1. 2. 2

Secondary links, connecting major population centres with

governorate capitals, these are asphalt or gravel surfaced.

Category C (Tertiary Roads)

Tertiary links, connecting district centres to primary or

secondary roads, these are generally earth surfaced.

Terrain

The types of terrain which the highway alignment traverses will

impose certain geometric design criteria pertaining to the nature of

that terrain.

To provide a general basis of reference between terrain and geometric

design, four classifications of terrain have been established in the

YAR:

Flat: level to moderately rolling topography offering few or no

obstacles to the construction of a highway and having

continuously unrestricted horizontal and vertical alignment.

Rol1ing: hiJJs and foothi11s, the slopes rise and fall gent1y with

occasional steep slopes offering some restriction to horizontal and

vertical alignments.

Mountainous: rugged foothills, high steep drainage divides, and

mountain ranges offering continuous restrictions to horizontal

and vertical alignment.

Escarpment: very steep and rugged slopes of the natural

ground, resulting in the adoption of minimum design standards.

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1.3 DESIGN SPEED

Design speed is the maximum safe speed that can be maintained over

any specified section of highway. Geometric design elements should

be consistent with a design speed selected as appropriate for

environmental and terrain conditions. Low design speeds are

generally applicable to highways with winding alignments in

mountainous terrain and escarpments. High design speeds are

generally applicable to highways on level terrain. Table 1. 1 shows

minimum design speeds in kilometres per hour for the different types

of terrain and road category.

TABLE 1.1: MINIMUM DESIGN SPEEDS (KPH)

Road Category

Type of Terrain A B C

Flat 110 100 50 Rolling 90 80 40 Mountainous 50 40 30 Escarpment 30 20 20

1.4 ROADWAY CAPACITY

The capacity of a particular roadway is the av~~~~g~r,~1!.mum tfoa~fic volume in passenger cars per hour (PCUs) expected to eeeulL

A-..

frequently under ideal conditions.

The capacity of the roadway is also affected by a number of factors

such as; lane width. shoulders. surface conditions. alignments.

grade, volume of commercial vehicles. variation in traffic flow and

traffic interruption.

TabJe 1. 2 shows recommended flow levels for the various roadway

elements and is based on a composition of 15 per cent of heavy

vehicles in the traffic. Where heavy vehicles form more than

1 - 3 ID738A/B

15 per cent of the traffic lane flows, standard and maximum working

hourly level should be reduced by the following factors:

Heavy Vehicle Traffic Composition Reduction Factor for Heavy

Traffic Flow

15-20%

20-25%

TABLE 1.2: FLOW LEVELS

125 PCU/Hr/Lane

185 PCU/Hr/Lane

Road Type Peak Hourly Flows 16* Hour Average Daily Flow PCU/Hour/Both Directions PCU/Hour/Both Directions Standard Max. l-lorking Min. Max. Within

Normal PDR Range

All-Pu!:Eose Dual C'way Road

Dual 2-Lane 2 940 3 920 20 830' 41 280 - 55 130 Dual 3-Lane 4 410 5 880 42 886 61 860 - 73 500

All-Pu!:Eose Single C'way Roads

10 m wide 2 330 2 820 14 700 21 680 - 29 100 7.3 m wide 1 470 1 960 - 2 450 15 070 - 18 380

* For 24 hour Average Daily flows multiply the above values by 1.1

Equivalent Value in Passenger Car Units: Private Cars and light goods vehicles - 1 PCU Goods Vehicles over 30 cwt unladen, buses and coaches - 2.5 PCUs

o· Commensurate with exceptionally low values of the Peak Hourly to Daily Flow Ratio (PDR) only

1 - 4

Absolute Max. 0

55 130-73 500

30 630 20 830

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SECTION 2 : Geometric Cross-Sections

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SECTION 2: GEOMETRIC CROSS-SECTION

2.1 CROSS-SECTIONAL ELEMENTS

2.1.1 Travel Lanes

The number of lanes to be used is a direct function of the volume of

traffic and the capacity of the roadway to allow the facility to operate

at a required and acceptable level of service.

Lane widths of 3.65 m wide are desirable in the interest of safety.

efficiency and ease of operation. However, when severe topographic

limitations such as in mountainous and escarpment areas or where the

right of way becomes a stringent control. then narrower lane widths

may be adopted.

Figures 2.1 and 2.2 show recommended cross-sections depicting the

essential elements of the different road categories.

2.::".2 Shoulders

Shoulders are necessary to provide structural support for pavement

edges, emergency parking space for stopped vehicles and side

clearance between moving vehicles and stationary objects on the road.

Table (C) Figure 2.2 shows recommended shoulder widths for the

different road categories and terrain.

2.1.3 Median

The median is that portion of a divided highway separating the

travelled way for traffic moving in opposing directions.

Under restraining circumstances that arise due to economical,

topographical and environmental factors, such as those in the YAR,

the median width may be reduced to a minimum of 6 m in flat or

rolling terrain and 2 m in mountainous or escarpment terrain with the

provision of a crash barrier.

2 - 1 ID738A/B

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10·00 MIN.

0.50::-1 1'50-300 VERGE~lt

CARRIAGEWAY

7·00 -7-60 ( 2 -LANE)

600

I-50

1 MEDIAN

3~ 1·50

CARRIAGEWAY

7-00 - 7·60 (2-LANE)

10·00 MIN.

1'50-300 [0'50 I I YERGE

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VARIES

~__ 0 I 0 :l

401 ~ -- -- 2-0% - 2'5% ~ ~ 2-0% - 2-5% ~ 40' 10 (/) .... -- _...- ~ (/) 10 ...... %_-01 .- " 4 IL- --ll 4/0 ~

I~I '............ 6 6 I --............. • ~VARIES

L.MIN~o-25 BELOW ROAD SUBGRADE LEVEL

-------t- -------------------

VARIES~ I

FLAT I ROLLING TERRAIN

1 0·50 1'50- 2·00 600-7'00

(2 LANE)

1 2'00 6,00-7,00

(2 LANE) VERGE

"""'-11 4

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4% I 20°1 ~ . 10-2,5%

MEDIAN

2'0%-2'5%

~ -MAX.0·25 BELOW ROAD SUBGRADE LEVEL

DOUBLE FACE CONCRETE BARRIER

MOUNTAINOUS I ESCARPMENT TERRftlN ' ..... .1 '" r"".1

1'50-2-00 0·50

0: W Q

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4%

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VERGE

I

'JVARIES

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NOTES-

I. ALL DIMENSIONS ARE IN METRES 2. FOR SIDE SlDPE SEE TABLE (A)

FIG. 2.2

........... __ ....... .- ....... - ~ ........... Mwl ...., ......

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q, q2 q2 q, ...- .. • -~ -::::::::::""1 - t"--,

L MAX. 0'~5 BELOW ROAD I

I H SUBGRADE LEVEL

RURAL TWO - LANE CROSS SECTION

x Y Z

HARD ROCK WEATHERED R. SOFT ROCK H=0·1·5 H= \·5·3·0 H> 3·0

4* 5 2 I 4 3 1·5

*3 FOR CATEGORY C ROADS

TABLE (A) SIDE SLOPES

TYPE OF SURFACE ql (%) q2 (%)

ASPHALT PAVEMENT 4 2·0 • 2·5

GRAVEL - 3·0

EARTH - 3·0

TABLE (B) CROSS SLOPES

CROSS SECTION VARIABLES (metres) ROAD

CATEGORY FLAT / ROLLING MOUNTAINOUS/ESCARPMENT

0 b Q b

A 1·50· 3·00 7·00·7·60 \·50 ·3-00 7{)0·7·6O

... B (PAVED) \·50· 2·00 600·7,00 1·50 • 2·00 600·7,00

B (GRAVEL) - 7·00 ·I(}OO - 7{)o .I(}OO

C - 5·00·6·00 - 500·600

TABLE (C) CROSS SECTION DIMENSIONS

ROAD CROSS SECTIONAL ELEMENTS Figure 2.2

2 - 3

2.1.4 Cross-slopes

Two lane roadways on tangents or on flat curves have a crown in the

middle of the carriageway and slope downwards towards both edges.

On divided highways, each one way pavement should have a

unidirectional slope across the entire width of the travelled way,

falling to the outer edge of each pavement.

The rate of cross-slope varies according to the type of surfacing

material used. Earth or gravel surfaces require steeper cross-slopes

on tangents than those with asphaltic surfaces. This is to prevent

the absorption of water into the surface.

Table (B) Figure 2.2 shows normal cross-slope rates for the different

types of road surface.

2.1.5 Sidewalks

Sidewalks are usually placed outside of a curb section in urban areas.

On rural roads sidewalks are usually not required except along

sections where there is intensive residential or commercial

development. Sidewalks should be of bituminous or concrete tile

surface. The minimum sidewalk cross-slope should be 1.5 per cent.

The absolute minimum sidewalk width should be 1 m.

2.1.6 Side-Slopes

Table (A) Figure 2.2 gives recommended values of cut and fill side

slopes.

It is strongly recommended that adequate geotechnical investigations

are made to de ~ermine required side-slopes in order to ensure that

the stability of the local soils is adequate. The minimum side-slope

for embankments should not be less than 1.5 to 1.0.

2.1. 7 Slope Benches

Where the material in a cut slope is sufficiently unstable to warrant

flatter than average slopes, then the provision of benches may be

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necessary in the case of deep cuts. The necessity for providing

benchc:" ~n unstabJe material, their width and vertical spacing should

be determined only after adequate material investigation.

The tops of alJ cut slopes should be rounded where the material is

other than solid rock. The amount of rounding depends on the

material, depth of rock and the natural contours of the ground (refer

to Section 8, Figure 8.4).

2.1. 8 Side Ditches

Side ditches should have an adequate hydraulic capacity to

accommodate drainage from the pavement and slope in the case of the

roadway being in cut. The depth of the ditch in cut sections,

normally, should not be deeper than 0.25 m beJow the sub grade for

safety and maintenance, however deeper ditches may be required for

short sections to drain flat gradient ditches to a c"lvert inlet or to a

section of highway th8.t is in embankment. Should hydraulic needs

dictate flitches of greatp.r capacity than that catered for by normal

depth 'VY ditches, th-s cesigner should design a flat-bottomed ditch of

sufficient width instead of depeening the 'V' ditch.

2.2 CLEARAN CES

2.2.1 Right-of-Way

Since thE right-of-way is one of the most major items in the cost of

the roadway, economic as we]] as engineering factors should be

anaJysed in order to achieve savings

(this m:-ty be possible to achieve by

alignment) •

in the cost of the right-of-way

making slight alterations to the . ." ~

-. The minimum requirement for the right-of-way boundary should be

40 metres in mountainous and escarpment terrain and 60 metres in flat

t and rolling terrain. -.

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2.2.2 Structural Clearances

(a) Lateral Clearance

A minimum lateral clearance of 1 m from the outer edge of the

shoulder to the nearest face of structures or obstructions should be

provided.

Bridge piers on a central reserve should be protected by safety

barriers placed at least 1.2 metres from the edge of the carriageway.

(b) Vertical Clearance

The minimum vertical clearance (headroom) for bridges over the

carriageway should be at least five metres with an additional allowance

of 0.1 metres given to resurfacing.

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SECTION 3 : Geometric Design Standards

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SECTION 3: GEOMETRIC DESIGN STANDARDS

3.1 SIGHT DISTANCE

3.1.1 General.

Sight distance is the distance at which a driver of a vehicJe can see

an object of a specified height on the road ahead assuming a specified

driver height, standard visual acuity and clear atmospheric

con di tions.

Two basic types of sight distances must be considered for safe and

efficient operation: stopping sight distance and passing (overtaking)

Sight distance.

3.1.2 Stopping Sight Distance

Stopping sight distance is the minimum distance required by an

average driver of a vehicle travel1ing at a given speed to react and

stop before reaching an object in its path. It is measured from the

driver's eyes which are assumed to be 1. 05 m above the pavement

surface to an object 0.15 m high on the road.

Stopping sight distance depends on the initial speed of the vehicle,

the perception and reaction time of the driver and the coefficient of

friction between the tyres and the road surface.

L'vIinimum stopping sight distance is computed using the fo]]owing

equation:

where Ss = Minimum stopping sight distance in metres

V = Vehicle running speed in kilometres per hour

t = Combined perception and reaction time in seconds

f = Coefficient of friction

3 - 1 JD738A/B

Table 3.1 shows stopping sight distance values for various design and

running speeds. These values are based on stopping on level

grades, on a perception plus reaction time of 2.5 seconds and a

coefficient of friction for wet pavement. Stopping sight distance on

grade can be computed using the following equation:

V2 Vt s -

s 252 (f:tO.Ol G) -\- -3"G

where V

f

G

=

= =

Vehicle running speed in kilometres per hour

Coefficient of friction

Longitudinal grade %

I (The stopping sight distance is measured from the driver's eyes which I

_ (, \'(.::t'~ are assumed to be 1.05 m above the pavement surface to an object

. 0 .15 m high on the road.)

3.1.3 Passing (Overtaking) Sight Distance

The provision of passing sight distance on crests is usually costly.

However, the requirements are included in these standards for

application where it is economically feasible and where the combination

of alignment and profile do not require the use of crest vertical

curves.

Passing sight distance is the minimum sight distance that must be

available to enable the driver of one vehicle to pass another vehicle

safely and comfortably, without interfering with the speed of any

oncoming vehicle travelling at the design speed. should it come into

view after the passing manoeuvre is started.

The sight distance is measured from the drivers' eyes, assumed to be

1.05 m above the pavement surface to an object 1.3 metres high on

the road.

Minimum values for passing sight distance are shown in Table 3.1.

3 - 2 ID738A/B

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TABLE 3.1: SIGHT DISTANCE STANDARDS

Desi2n Coeff. of Min. StoEE:ing Min. Passing Speed Friction Sight Distance Sight Distance (kph) (m) (m) - -

20 0.42 18 -30 0.40 30 -40 0.38 45 280 50 0.36 65 340 60 0.34 85 420 70 0.31 110 480 80 0.30 140 560 90 0.30 170 620

100 0.30 200 680 110 0.29 240 740

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3.1.4 Sight Distances on Horizontal Curves

Where an object off the pavement such as a bridge, pier, building,

cut slope or natural ~"'owth, restricts sight distance, the minimum

radius of curvaturs is determined by the stopping sight distance.

Figure 3.1 Sh0''':-: sig!1 t distances for various curve radii and the

offset distance from lane centreline to the obstruction. The line of

sight is assumed to intersect the obstruction at the midpoint of the

line of sight. The intersection point would then be 0.76 m above the

centreline of the inside lane.

Allowance _ for differences in braking distances on grade should be

made for sight determination on horizontal curves.

3.1.5 Sight Distances on Crest Vertical Curves

The minimum length of a crest vertical curve is based either on the

minimum stopping sight distance or on the minimum passing sight

distance, if passing is a design requirement. Adopting the passing

sight distance criteria. will result in having long curves requiring

extensive earthwork in many places which may not be justified for

secondary and tertiary roads. The minimum vertical curve length is

expressed by the following equation:

3 - 3 ID738A/B

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30 40 50

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Stopping sight distance (s.)

t. Highway

t. Inside lane

-~

Line of sight

'-- Sight obstruction

DESIGN SPEED ( K. P. H.) 60 70 80 90 100

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J / V V V ,v / V [77 /V7[0 ~v / / / / /VjV V V /r~ ~v:,~t:/

40 60 80 100 120 140 160 180 200 220

S. : STOPPING SIGHT DISTANCE ALONG ~ CURVE ( METRES)

5 s : 2 R Arc Cos ( R ~C )

Arc Cos Expressed in Radians

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- HORIZONTAL CLEARANCE FOR STOPPING SIGHT DISTANCE Figure 3.1 "I

3 - 4 -

L = KA

where L = Length of vertical curve in metres

J{ = Constant of vertical curvature

A = Algebraic difference in per cent of gradient

K values for stopping sight distance are computed by:

S 2 S

Ks --405

where Ss = Minimum stopping sight distance

K values for passing sight distance are computed by:

2 Sp

where Sp = minimum passing sight distance.

r.:inLnum values for K for various design speeds are shown in

Table 3.2.

3.1. 6 Sight Distance on Sag Vertical Curves

The minimum length of a sag vertical curve is based on t:, '~linimum

stopping sight distance which is controHed by the vehicle headlight

sight distance. It assumes a headlight height of 0.6 m and a 10

upward divergence of the Jight beam from the longitudinal axis of the

vehicle. For overall safety. sag vertical curves should be long

enough so that the light beam illuminates the roadway ahead for a

distance of at least the stopping sight distance.

The minimum length of a verticaJ curve is expressed by the equation:

L = KA

3 - 5 ID738A/B

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------

where K for sag vertical curves is expressed by:

K = s

S 2 S

122+3.5 Ss

and where K = s

=

Constant for stopping sight distance at

vertical sags

Stopping sight distance.

Values for K for various design speeds are shown in Table 3.2.

TABLE 3.2: K VALUES FOR CREST AND SAG VERTICAL CURVES

'K' Values Crest Vertical Curves

~es1gn Speed Stopping Passing Sag Vertical Curve (kph) Conditions Conditions

20 1 - 2 30 2 - 4 40 5 83 8 50 11 123 12 60 18 188 18 70 30 244 24 80 49 333 32 90 72 408 41

100 99 490 49 110 143 581 60

Note: The minimum length of curves should be rounded up to an even

10 m.

3 - 6 ID738A/B

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3.2 SUPERELEVATION

3.2.1 Gener.al

As a vehicle traverses a horizontal curve. the centrifugal force

working on the vehicle is opposed by the roadway superelevation and

by the side friction between the tyres and the roadway surface.

Curves should be superelevated to balance the effect of the

centrifugal force. The rate of superelevation will depend on the

vehicle speed. the curve radius and pavement surface characteristics.

The minimum alJowable radius for any design speed can be computed

using the following equation:

R = V2 127 (e+f)

where R = Minimum radius of circular curve in metres

v = Vehicle speed in kilometres per hour

e = Maximum superelevation rate in metres per metre

f = Side friction factor

3.2.2 Superelevation Rates

Side friction factors for wet pavements are used in highway design.

The maximum safe side friction factors for the maximum superelevation

rate of 0.08 m/m ya!'y linearly from 0.17 for V=20 kph to 0.12 for

V=110 kph.

The maximum superelevation rate will be dependent on the type and

characteristics of the surfacing material and generally should not

exceed 0.08 m/m.

Lower superelevation rates may be necessary in urban areas where

restricted speed zones or at-grade intersections are the controlling

factors. In addition. established street grades. curbs or drainage

3 - 7 ID738A/B

may impose limitations on design. A supereJevation rate of not more

than 0.06 m/m shouJd be used for urban roads.

3.2.3 Curvature

The minimum radii for superelevated curves for bitumen surfaces for

various design speeds are shown in Table 3.3. The radii have been

rounded to the nearest 5 metres.

TABLE 3.3: MINIMUM RADII FOR MAXIMUM SUPERELEVATION RATE

v (kph) e f R (m/m) (m)

20 0.08 0.17 15 30 0.08 0.16 30 40 0.08 0.16 50 50 0.08 0.15 85 60 0.08 0.15 125 70 0.08 0.14 175 80 0.08 0.14 230 90 0.08 0.13 305

100 0.08 0.13 375 110 0.08 0.12 475

3.2.4 Development of Superelevation

The length required to develop the required supereJevation should be

adequate to ensure both a good appearance and satisfactory riding

qUality. The length of runoff should be long enough so that the

runoff slope meets the criteria shown in Table 3.4. The runoff slope

is the longitudinal gradient between the edge of the travel1ed-way

profile and the of the profile grade line of the carriageway.

3 - 8 ID738A/B

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TABLE 3.4: SUPERELEVATION RUNOFF SLOPES

Design Speed (kph) Maximum Relative Slope (%)

20 0.91 30 0.B2 40 0.74 50 0.66 60 0.59 70 0.54 BO 0.50 90 0.47

100 0.44 110 0.41

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The absolute minimum length of supereJevation runoff used shouJd be

30 metres, however in special restrictive situations where the

standard supereJevation rate is not feasible or the desirable runoff

length is not attainable, the highest possible rate and the longest

length respectively should be used.

Figures 3. 2a and 3. 2b illustrate desirabJe methods for developing

supereJevation.

3.3 HORIZONTAL ALIGNMENT

3.3.1 General Controls

The most important consideration in determining the horizontal

alignment of a road is the provision of a safe and continuous

operation at a uniform design speed for substantial lengths of

highway. The major aspects controJling horizontal alignment are:

type or category of facility, safety, design speed, topography,

vertical alignment and construction cost. All these factors must be

balanced to produce an alignment that is safe, economical and in

harmony with the natural elements of the land.

3 - 9 ID73BA/B

METHOD OF ATTAINING SUPERELEVATION FOR PAVEMENT REVOLVED ABOUT THE CENTRE LINE OF

A SINGLE CARRIAGEWAY ROAD OR INNER EDGES OF EACH CARRIAGEWAY OF A DUAL CARRIAGEWAY ROAD

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CARRIAGEWAY MEDIAN CARRIAGEWAY CARRIAGEWAY

~ PROFILE GRADE

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DUAL CARRIAGEWAY SINGLE CARRIAGEWAY

DIAGRAMMATIC CROSS SECTION

~ ~ I~ENGTH OF v.c. (SEE NOTE ),1 ;. - V

SLOPE RELATIVE TO PROFILE GRADE: YN

,!-ENGTH OF V~. (SEE NOTE ) .. ,

~.... E!,.. _ FI EDGE OF -=:;::::::;:;;~..=...:---t'i CAR R I AG E WAY

iii Ao Bo ,CO:CI Eo F ~ ---T~-------T~-----=~+E~--~--~~----------------~~-----w~PROFILE

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ILENGTH OF v.e. (SEE NOTE)

GRADE

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: 'Q' V/2 ~ANGENT R~OJP LENGTH OF c6>RUNOFF LR 1/2 B N V/2

NORMAL V/2 TR: 1/2 8· QQ. N TRI: 1/2 8·QO-N:TR LAI : 1/28' (q-Qo)'N V/2 FULLY

CROWN V/2 LENGTH OF SUPERELEVATION LA=I/2B'(Q+QO)'N I

V/2 ~~~Q~ELEVATEO

TOTAL LENGTH OF APPLICATION

DIAGRMMMATIC PROFILE

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;; CARRIAGEWAY ;:..N CI~~;;;:::::::~~~:-----F~~:.!..---I g.

AI 11.2: 02J. • EDGE OF

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!--!CARRIAGEWAY qo: NORMAL CROSSFALL

ON STRAIGHT (m/m) I"

q : CARRIAGEWAY CROSSFALL (m/m)

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DIAGRAMMATIC SECTION

NOTE-

I. LENGTH OF SUPERELEVATION ROUNDING VERTICAL CURVES SHALL BE:-V : 20m FOR LA > 60m

V : 1/3 LA FOR LA ~ 60m

SUPERELEVATION DETAILS

3 - 10

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Figure 3.2a

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TOTAL LENGTH OF APPLICATION

1~~U~ ~~~IA~~~;'T/iJf~~ (SINGLE CARRIAGEWAY) t -£OG£ OF CARRIAG£WAY - -:~. - ---- - - - _ .

EDGE OF HARD SHOULDER

CONTROL LI N£ I ~ (DUAL CARRIAGEWAY) ----·;:·-:-".;·-:t;·-1

.. STRAIJtiT CLdTHOl6 kS IRC.

CURVE

APPLICATION OF SUPERELEV ATiON

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CURV

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APPLICATION OF SUPERELEV ATiON

METHOD OF ATTAINING SUPERELEVATION FOR HARD SHOULDERS

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ROLLOVER (MAX.O.07)1 Note 2-3 . PROFILE

GRADE

DIAGRAMMATIC CROSS-SECTION

52

. ~--=~::.:-s---- EDGE OF CARRIAGEWAY

~;;--~-- : EDGE OF HARD SHOULDER

; •• ~-:; ~o::O:~£eARRIAG£WAY __ :: _ EDGE OF HARD SHOULDER

DIAGRAMMATIC PROFILE 1 (ROLLOVER ~O.07) I r NOTES

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Length of $uperelevaf!on rounding vertical curves shall be:-V : 20m FOR LA > GOm; V : 1/3 LA FOR LA ~ Gam.

2 • Rollover' is defined as the algebraic difference between the cross falls of the hard shoulder and the adjacent carriageway Maximum Ral/over : 0.07 m/m

3 High side shoulder crossfaU ~- Norrr.al shoulder crossfall applies until the maximum rolloller is obtained. then the shoulder cross foil is rotated to maintain the rollover at 0.07m/m

4 Low side shoulder crossfall: - Normal shoulder crossfal/ applies until the carriageway superelevation rate reaches the normal shoulder crossfall. For carriageway superelevation rates above this, the shoulder crossfal! equals the carriageway superelevation rate.

r SUPERELEVATION DETAILS Figure 3.2b ,I':;

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3.3.2 Standards for Curvature

The minimum radii of superelevated curves are given in Table 3.3.

Radii larrrer than the minimum radii curves should be used wherever

possible. this will increase the safety resulting from improved sight

distance and vehicle operating conditions.

3.3.3 Consistency of Alignment

Horizontal alignment should be as directional as possible and should

be compatible with the topography.

Compound circular curves consisting of two or more contiguous

unidirectional curves should be avoided and a single curve adopted if

economically or physically possible. If this is unavoidable, the radius

of the flatter curve should not be more than 50 per cent greater than

the radius of the sharper curve.

Broken back curve combinations composed of a short tangent between

two curves in the same direction should be avoided. Under such

conditions the use of transition curves is preferable. Abrupt

reversals in alignment should be avoided. A reversal in alignment is

suitably designed by including transition curves of sufficient lengths

between two reversing circular curves to allow for superelevation

runoff.

Sharp curves should not be introduced on sections of high fill as

drivers may have difficulty in estimating the severity of the curve.

3.3.4 Alignment at Bridges

Horizontal alignment at bridges should be designed to avoid having

superelevation transitions 011 a bridge since this usually results in an

unsightly appearance of the bridge and its railing. It is therefore

recommended, if at all possible, that the entire bridge should be

located on a tangent or a circular curve. Tapers and flare ends

should also be located clear of structures. The radii across the

bridge should be as large as possible.

3 - 12 ID738A/B

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3.3.5 Transition Curves

Transition eurves are required to reduce the rate of change of

centrifugal force. The curve to be used is the c]othoid, where the

length of the particular clothoid is defined by:

where L = Length of clothoid

A = A constant and a function of the design speed (V)

R = The rac.::us of the curve

Table 3. 5 below give minimum values of A corresponding to design

speeds.

TABLE 3.5: RELATIVE VALUES OF 'A' WITH DESIGN SPEED

Design Sreed V (kph) Minimum Values of A

20 30 30 40 40 55 50 70 60 80 70 100 80 110 90 130

100 140 110 150

Provision of transition curves where the design speed is less than

50 kph is not essential.

3.3.6 Widening on Curves

Pavement widening on curves is required on sections with sharp

horizontal curvature in order that vehicles or trucks continue to

remain within the lane which they are occupying and can fol1ow the

centreline of the road while negotiating the curve.

3 - 13 ID738A/B

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Travelled way widening values are given in Table 3.6. Widening is to

be applied uniformly to the inside of the curve and should be

transitioned throughout the length of the superelevation runoff.

TABLE 3.6: TRAVELLED WAY WIDENING VALUES

Total Amount of Widening for Pavement Width (Metres)

Radius (m) 5.0 5.5 6.0 6.5 7.0 7.3

Less than SO 2.30 2.05 1.80 1.55 1.3 1.0

SO - 100 1.90 1.65 1.40 1.15 0.90 0.80

100 - 200 1.50 1.25 1.0 0.8 0.60 0.60 200 - 500 1.20 0.90 0.60 - - -500 - 1 000 0.60 - - - - -Over 1 000 - - - - - -

For curves of a radius of 30 m or less t the actual tracldng paths of

articulated vehicles should be checked using templates to see that

adequate widening has been provided.

3.4 VERTICAL ALIGNMENT

3.4.1 General Controls

Vertical alignment is control1ed by a variety of factors such as

safety t topography, type or category of facility, design speed,

horizontal alignment, construction cost, drainage, vehicular

characteristics and aesthetics.

For aesthetic reasons the length of vertical curves should be

substantially longer than the length required for stopping sight

distance. A broken back grade line (two vertical curves in the same

direction separated by a short length of tangent grade) is not

desirable, particularly in sags.

A ro]]er coaster type of profile grade should also be avoided.

3 - 14 ID738A/B

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The gradient of the main highway should be reduced as much as

possible at the 10('[1t::::'1 of an at-grade intersection.

Superelevation runoff occuring on a vertical curve requires special

attention in order to ensure that the required minimum vertical

curvature is maintained across the pavement. Both edge profiJes

should be checked and adjusted where necessary in order to maintain

the desired minimum vertical curvature.

3.4.2 Grade Standards

Maximum gradients for the different road categories and design

speeds are shown in Table 3.7.

TABLE 3. 7: ROAD GRADIENTS

Maximum Grade (%) Design Speed Road Category

(kph) A B* C*

20 - 11.0 12 30 10.0 11.0 12 40 10.0 10.0 12 50 9.0 9.0 11 60 8.0 9.9 -70 7.0 8.0 -80 6.0 7.0 -90 5.0 6.5 -

100 5.0 5.0 -110 4.5 - -

* Values given are for paved sections of roads.

For unpaved roads the maximum permissible grades should be

seven per cent. However, in difficult mountainous terrain where the

total cost of construction can be decreased by the use of paved road

sections at steeper gradients, such proviSion is acceptable providing

that resulting gradients do not exceed the values shown in Table 3.7.

Minimum longitudinal gradients for highways should not be flatter

than 0.3 per cent.

3 - 15 ID738A/B

, -3.4.3 Position of Grade Line

For two lane undivided roads, the profile grade line should coincide

with the pavement centreline. For divided roads with narrow

traversable medians (less than 6 m) the profile grade line should

coincide with either the centre line or the inner edge of pavement.

3.4.4 Critical Grade Length and Climbing Lanes

Critical grade length is determined from the reduction in speed which

is the difference between the average running speed and the tolerable

minimum speed on grade.

In some instances the terrain may preclude shortening or flattening

grades to meet these controls. Where a speed reduction greater than

the suggested design guide cannot be avoided, undesirable types of

operation may result on roads with numerous trucks, particularly on

two-lane roads with volume approaching capacity and in some

instances on multi-lane highways. Where the critical length is

exceeded, considerations should be given to providing an added uphill

lane for slow moving vehicles, particularly where volume is at or near

capacity and the truck volume is high. Truck climbing lanes of

widths equal to the adjacent through lane, but not less than 3.1 m,

may be pr9vided in hilly and mountainous terrain. These lanes will

increase capacity, decrease delays, and reduce accidents.

Justifications for providing climbing lanes are based on the relative

speeds of trucks and motor cars, traffic volume limits and the length

of the climbing lane.

(i) Speed

To justify a climbing lane the length and grade under consideration

must be long enough to cause a decrease in truck speed by at least

20 kph. For example if the initial speed of the truck is taken to be

60 kph and the speed of the truck does not fall below 40 kph,

climbing lanes would not be justified on that grade irrespective of the

traffic volumes.

3 - 16 ID738A/B

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(ii) Traffic Volume

A climbing lane is considered necessary when the Design Hour Volume

equals or exceeds the design capacity of the highway on the grade.

(iii) Total Length of Climbing Lanes

The minimum length of a climbing lane should be 250 m excluding

tapers. Sight distances should be checked and where necessary the

climbing lane should be extended. Climbing lanes should end at the

point where the truck regains a speed equivalent to f or higher than t

the speed for which the climbing lane was initiated. It is desirable to

end the climbing lane At a point beyond the crest of a vertical curve.

Figure 3.3 shows a typical plan and profile for the location of

climbing lanes.

Figure 3.4 shows the operating characteristics of a 250 mass/power

ratio to be used for design purposes.

3 - 17 ID738A/B

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EXAMPLE SHOWING CLIMBING LANES FROM OPPOSING DIRECTIONS OVERLAPPING AT HILLCREST

LENGTH OF FULL WIDTH CLIMBING LANE 790

TAPER 60 "1" TRUCK SPEED BELOW 40 .1 30 I. TAPER liN 20 700 .... _-

V=60 , V 40 V,20 ASSUMED APPROACH SPEED OF TRUCKS 60kph ... 1+--150 '" 100

GRADE 0%

W: C'WAY WIDTH

I- 260 .1 50

VI40 VI40

,TAPER IIN50 30 I TRUCK SPEED BELOW 40 I 60 1 .... _.. 1 ... 690 ..... .... - ..

LENGTH OF FULL WIDTH CLIMBING LANE

PROFILE

CENTRELINE MARKING INDEPENDENT OF CREST SIGHT DISTANCE

TAPER .. I_ 30 IIN50

780

LINEMARKING FOR CLIMBING LANE

60 TAPER liN 20

VI60

GRADE 1,5°,..

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lAPE~I" 60 I IN 20

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Deceleration Curves

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0~0----2~0-0---4-0~0----60~0----8~0-0----10~00----12~0-0--~1400

80

60

40

20

Distance (m)

Speed vs distance chart on uniform ascending grades for trucks with mass: power ratio = 250

Acceleration Curves

200 400 600 000 1000 1200 1400

Distance (m)

Speed vs distance chart on uni form descending and ascending grades for trucks with moss: power ratio = 250

TRUCK OPERATION ON ASCENDING AND DESCENDING GRADES

3 - 19

Figure 3.4

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SECTION4: .. . Flexible Pavement· DeSign

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4.1 GENERAL

Pavement design for bituminous roads in the YAR will be carried out

by means of two well-accepted methods: the Shell and AASHTO

methods of pavement design.

In determining the thickness of pavement, the two major factors to be

considered are traffic loads and the strength of the soil sub grade .

Other factors which need also to be considered in the pavement

design are: environmental and climatic conditions, the serviceability

index, the ambient temperature and properties of the paving material.

Pavement layer thicknesses will be obtained by both the Shell and

AASHTO methods and based on these results, as well as the

availabirty of construction materials, the designers will make their

own recommendations for the pavement design of the particular road.

4.2 TRAFFIC

The loads imposed by light vehicles do not contribute significantly to

the structural damage caused to road pavement by traffic. For

pavement design purposes only the number of buses and trucks and

their axle loadings need be considered.

A traffic analysis for each road will be made. Such an analysis

should be based upon information of the following:

Total traffic counts carried out over a suitable period of time ./

Truck and commercial traffic counts classified in terms of vehicle .

type t number of axles , axle configuration

Truck loading policy being used, and if possible the degree of ,.-

overloading that is actually taking place.

In order to obtain an average traffic over the design life of the road,

it is necessary to predict an annual growth of the commercial traffic.

4 - 1 ID738A/D

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-'---

-

Such a prediction wi]] be dependent upon the potential economic

growth of the area, and other factors that may influence the traffic

growth. If such information is Jacking, the national growth factor

may be used. t

Both AASHTO and Shel1 methods of pavement design express the

traffic in terms of the cumulative number of standard axle repetitions

on the road pavement during its design life. I The conversion of

conventional axle to the standard (80 kN) axJe may be made through

tabJes available in the I AASHTO Interim Guide for Design of Pavement

Structures' (1972) or in multiplying the cumulative number of

commercial traffic by the pavement damage factor given on

Figure 4.1.

A design life of 10 to 15 years shall be considered. /

4.3 PAVEMENT DESIGN METHODS

The fonowing is a brief description of the design methods' to be

adopted for pavement design.

4.3.1 Shel1 Method

The Shell method of pavement design. as presented in the Shell

'Pavement Design Manual I (1978), is based on the elastic layer theory,

measured material properties and rational performance criteria. The

method incorporates all relevant major design parameters. In

particular it takes into consideration the effects of temperature, which

makes the design appropriate for different climates. and enables the

use of different types of asphalt mixes. However, only the Mean

Average Annual temperature is used and large fluctuations in

temperature during shorter periods cannot be accounted for.

The SheJ] Pavement Design Manual primarily takes the form of a large

number of charts and data tables. The user. on the basis of his own

data. can read off the thicknesses required directly from the

thickness charts. The procedure is based on a series of worksheets

on which the user records his findings stage by stage. The use of

these charts requires data on the following design factors:

4 - 2 ID738A/D

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1

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Proposed Leoal Altle Load

~

~ ~ ~ ~ ,

~

,~

1\ ,

~

~

=

2

trI

.. G)

CD c: c: ~

.E t- -

~ g

.9 CD c ..

ct

'"

V

ttl

I N

I

Pavement OamaOe

RELATIONSHIP BETWEEN PAVEMENT DAMAGE AND AXLE LOAD Figure 4.1

4 - 3

4.3.2

Traffic: expressed as the cumulative equivalent number of 80 kN

standard axles per lane

Temperature: expressed as the mean annual temperature in the

road area. For pavement design purposes the 'weighted' mean

annual air temperature (w-MAAT) win be computed

Subgrade: expressed as the subgrade modulus (N/mZ) which is

converted from the design CBR

Bituminous materials: expressed in terms of stiffness and fatigue

characteristics. The selected mix code wi]] be dependent on the

penetration grade of the bitumen used as we]] as the design of

the mix.

AASHTO Method

The flexible pavement design procedure presented in the 'AASHTO

Interim Guide for Design of Pavement Structures' (1972) is based on

the results of the AASHTO Road Test, supplemented by existing

design procedures and available theory.

The design procedure uses two simplified charts and the one to be

used wiJJ depend upon the level of serviceability required in the form

of nomographs which have been developed from the AASHTO Road

Test data. The use of these charts requires data on the fol1owing

design factors:

Subgrade strength: expressed as the soU support value which

incorporates an empirical correlation with the design CBR value

of the sub grade

Projected traffic: the cumulative volume of traffic during the

design life expressed in equivalent 80 kN standard axles

Environmental and climatic conditions calJed a Regional Factor

based on rainfall and frost conditions in the project area, and

the expected condition of the pavement structure in terms of

saturation flooding

4 - 4 ID738A/D

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T

"

Structural ,properties of the materials: expressed as a umtless

coeffieientfor the different pavement layers

Serviceability index: the type and quality of service expected

from the pavement structure during the anticipated life.

The combined effect of the above-mentioned factors enables the user

to work out the required structural number which is converted into

the required thickness of each pavement layer. by using pavement

layer coefficients.

The following coefficients are generally used in the pavement

structure in order to convert structural numbers to actual

thicknesses:

Asphaltic concrete wearing course 0.44 (Marshall

stability)

~ 900 kg,

Asphaltic concrete binder course 0.40 (Marshall

stability)

~ 800 kg

Asphaltic concrete base course 0.35 (Marshall

stability

~ 800 kg

Crusher run base course 0.14 (CBR > 80%)

Granular subbase course 0.11 (CBR > 30%)

Considerable care is needed to uSe the correct coefficients in terms of

the materials being used. The coefficients given above are those to

be used t assuming the materials are the same as those used in the

AASHTQ..testroad,e. g.', the granular base would be fully crushed , ,

stone.. non-rounded, non-weathered, having a minimum CBR of

80 per cent.

4 - 5 ID738A/D

If other materials are to be used because of their availability. other

coefficients should be used. Guidelines are shown in Table 4.1.

In YAR the use of the crusher run base course should be preferred

over the bituminous base course for the following reasons:

Good quality crushed stone and gravel is readily available.

therefore, its use is more economical.

Crusher run base course is less sensitive to variations in mixing

and compaction than the bituminous base; therefore. it is easier

to control.

4.4 BITUMINOUS CONCRETE MIX PROPERTIES

4.4.1 Asphalts

Asphalt for bituminous concrete should be petroleum asphalt cement.

grade 60-70 penetration. A lower penetration asphalt should be

considered when road gradients are in excess of 10 per cent.

4.4.2 Gradation

The combined mineral aggregate for the bituminous mixes should

conform to the gradings in Table 4.1.

TABLE 4.1: GRADINGS OF MINERAL AGGREGATES

Per cent Passin Base Binder Wearing

AASHTO Sieves Course Course Course

l~ inch 100 100 100 1 inch 80-100 100 100 3/4 inch 70-90 80-100 100 ~ inch - - 80-95 3/8 inch 55-75 60-80 -No. 4 44-62 45-65 48-62 No. 10 33-48 30-50 32-45 No. 40 16-27 15-32 16-26 No. 80 - - 8-18 No. 200 3-10 3-10 4-8

4 - 6 ID738A/D

r I

I I

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4.4.3 Job-Mix

When tested according to the Marshall Method, the bituminous

mixtures should conform to the requirements in Table 4.2.

TABLE 4.2: BITUMINOUS MIXTURE REQUIREMENTS

Wearing Base Course Binder Course Course

Asphalt Binder (%) 4-7 4-7 4-7

Stability (kgs) 800 800 900

Flow (mm) 2.4-5.0 2.4-5.0 2.4-4.0

Voids in Total Mix (%) 4-7 4-6 4-5

Voids filled with Asphalt (%) 60-75 60-75 70-80

4 - 7 ID738A/D

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SECTION 5 :':. >'.- ~,',' .,' Hydrology ··ari4 Hydraulics ·of:_':',>.;,,·.,,:' .'. Drainage-:Structures

.', -': ::. .'

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SECTION 5: HYDROLOGY AND HYDRAULICS OF DRAINAGE

STRUCTURES

5.1 HYDROLOGY OF A DRAINAGE BASIN

For the design of small drainage structures, the peak discharges

under consideration are those of rt:noff from small drainage basins.

There is a significant difference between small and Jarge drainage

basins. For conditions in the YAR a limit of 10 km 2 is adopted as

the criterion of a smal] drainage basins for practical purposes.

From a hydrological point of view, the runoff from a drainage basin is

influenced by climatic and physiographic factors. The climatic factors

include the rainfaJl. and evapotranspiration. Physiographic factors

include the draina ~t;' area, its shape, slope J land use, surface

infiltration condition, soil type, permeability, topography and channel

characteristics.

5.2 HYDROLOGICAL DETERMINATIONS

5.2.1 General

The existing methods of hydrological determination of waterway areas

may be classified into a variety of categories.

5.2.2 Method of Judgement

By this method the hydrological determinations are dependent on

practical experience and individual judgement. The judgement

developed by the engineer is invariably guided by personal

-observation and general informatio[l coJJected on the ground such as

the flood height. the size of channel, and drainage structures in the

vicinity of the stream, this may be satisfactory if the judgement is

sound. However. the method has disadvantages since no judgement is

perfect and because conditions vary greatly from problem to problem.

5 - 1 ID738A/C

5.2.3 Method of Formulae

By this method a formula is developed to determine the waterway

area. The formulae range from simple to complex ones; many like the

Rational and Talbot Formulae are still very popular in engineering

practice. The greatest merit of formulae is their function as a guide

to quickly determining the general range of the probable minimum,

maximum and average values. The method can also be considered as

practicable and serviceable for rough calculations. However, the

disadvantage of this method is the uncertainty involved in the

selection of the proper coefficient for most formulae to meet closely

the conditions of the problem under consideration.

5.2.4 Method of Direct Observation

This method involves making careful field surveys of drainage area

and stream characteristics and then making a precise hydrologic

analysis and hydraulic study. This is used to arrive at the required

size and shape of the waterway which wiU carry off the water

quickly.

5.2.5 Method of Correlation Analyses

This method can be used in ungauged catchments and involves the

correlation of important hydrological factors by relating them to

gauged catchments. These factors may include catchment area, slope

and shape of catchment, type of soil, land-use, stream frequency,

percentage urbanisation, average annual rainfall, soil moisture de fecit

etc. The peak discharge is found by using an appropriate formula

relating these hydrolOgical factors or by a nomograph for practical

applications.

5.2.6 Method of Hydrograph Synthesis

For this method, flow records and the corresponding· rainfall records

are required. Isolated rainfall events that produce single-peaked

hydrographs are selected. The base flow is subtracted from each

hydrograph and the volume of the storm runoff measured. The

rainfall infiltration is then estimated by standard methods and the

effective rainfall calculated. The catchment area is measured and the

5 - 2 ID738A/C

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-

volume of effective rainfall found. This volume is compared to the

actual volume of runoff from the hydrograph to check for any

discrepancies. The hydrograph obtained is defined as the unit

hydrograph i.e. - the runoff p!"oduced bya known intensity and

duration of rainfall. This process is repeated and a number of unit

hydrographs are obtained from which the average is found. The

return period and profile of the design storm is chosen and by using

the wet hydrograph, the design hydrograph can be found by the

principle of superposition.

5.3 RECOMMENDED HYDROLOGICAL METHODS

The merits and demerits of each method should be carefully

considered by the designer as appropriate to specific con<.litions and

available hydrometeorological data atrailable in the country. However

it is recommended that the hydrological determinations for small

drainage basins shall be made hy the Rational Method and for large

drainage basins by the modified Talbot Formula. Wherever conditions

allow. these determinations should be checked by the method of direct

observation, I.e .• Slope-Area Method.

5.3.1 Rational Method

The Rational Formula for the determination of runoff is as follows:

Q = 0.278 CIA

where Q = Discharge in m 3/ sec

C = Runoff coefficient

I = Rainfall intensity in mm/hour for a duration equal

to time of concentration

A = Drainage area in km!.

The coefficient of runoff C is the variable of the Rational Method

least sUsceptible to precise determination. Its use ih the formula

implies a IlXed ratio for any given drainage area, whereas in reality,

the coefficient accounts for abstraction or losses between rainfall and

5 - 3 ID738A/C

--

-

-

runoff which may vary for a given drainage area as influenced by

differing climatological and seasonal conditions. The range of

coefficients for different characters of tributary areas are shown in

Figure 5.1. The runoff factor selected should reflect the character

of the area after the development.

Determination of rainfall intensity for hydraulic design involves

consideration of the fo11owing factors:

Average frequency of occurrence

Intensity duration characteristics of rainfall for selected

average frequencies of occurrence

Time of concentration.

The three factors are brought together in an Intensity-Duration

Frequency Curve (IDF).

The rainfall distribution in the Y AR is dispJayed in isohyetals and is

shown in Figure 5.2. This shows that the mean annual rainfall in the

country varies from less than 100 mm to more than 700 mm. Because

of this large variation in the annual rainfall, three sets of Intensity -

Duration - Frequency Curves for three ranges of rainfall i.e. less

than 200 mm t 200-400 mm and more than 400 mm t have been presented

in Figures 5.3, 5.4 and 5.5 for use in the hydraulic deSign of

structures depending on their location.

The time of concentration at any point in a hydraulic design is the

time required for runoff from the most remote portion of the drainage

area to reach that pOint. The time of concentration is estimated from

the Kirpich formula:

tc

where

L 1-15 -

= 52 X HO'38

tc =

L =

The time of concentration in minutes

Horizontally projected length of drainage area in

metres

5 - 4 ID738A/C

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AO~--~~--------~~~----------------~

..... ..... o z ::>

0-8

e::: 0-6

..... o

IZ !::! 0-4 (.) c;: ..... L.a.J o (.)

0-2

BAND 3

0-0 L-_______ ..L...-______ ..L...-_____ "-_____ ----'

o

BAND 1

BAt;lD 2

BAND 3

BAND 4

50 100

RAINF' ALL INTENSITY I

ROWNO BARREN IN UPPER SAND VALUES, FLAT IIARR£N

ISO

mm/hr.

IN LOWER BAHO. I1tEI' FORESTED • STEEP GlASS WEADOWS

Tlt.lBER lAHDS OF MODERATE TO STEEP SLOPES. WOUNTAINOUS. FAIIMING

FLAT PElMOUS SURFACES, FLAT F'NtIotl»IDS WOODED IJtU. AND Wu.oows

200

r RUNOFF COEFFICIENT FOR USE IN RATIONAL METHOD

- 5 - S

LIMIT USED FOR DETERMINING Ie'

Figure 5.1

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YEMEN ARAB REPUBLIC

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ISOHYETALS FOR AVERAGE ANNUAL RAINFALL (mm) Figure 5.2 I 5 - 6 ,-

1

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ISO

150

140

130

120

a: 110 ;:) o ::c a: ~ 100

f3 a: ~ 90 ~ ::::i ...I

i 80 z

:: 70 -~ l-e;; 60 z &&J ... Z -

30

20

10

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" '" ~'\ ~~ ~ -.. ~ I' '-."" ~ ~ , ..... , ~ "" ~ ~ "' ~ "- "-.....

, ~ , t: "'I11III , ....... ~ ~ " f'" ~ r-.. ~

< \ 2 3 4 5 10 15 20 30 60

TIME OF CONCENTRATION (Te) IN MINUTES

CURVE J : LESS THAN 200m .m. ANNUAL RAINFALL

, RAINFALL INTENSITY - DURATION - FREQUENCY CURVES

~

~ ""II1II

~ ~ ~ 110..

~ ~ r--.. ~ .... ~

120

Figure 5.3

180

170

1 -- 160

1\ , ~~ ,",_

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'tb ~ '~ ~ ~~

" "', ISO

140

130

a:: ;:)

~ 120 a:: LIJ ~

ff} 110

a:: I-LIJ

! 100 -' ::! 2

3: 90

-:: >-I- 80 u; Z LIJ I-3e 70

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......... ..... ~ ~ ~ ~ .... .

10

2 3 4 5 10 15 20 30 60 TIME OF CONCENTRATION (Tel IN MINUTES

CURVE 2: FROM 200m.m. - 400m.m. ANNUAL RAINFALL

RAINFALL INTENSITY - DURATION - FREQUENCY CURVES

5 - 8

~ ~ --.. .....

I

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, ~ ~ ~ ~ ~ ~

120

I I

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Figure 5.4 I ,

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a: ;:) o %

200

190

180

170

160

150

a: 140 IIJ Q.

en ~ 130 tIIJ ~

:j 120 ~

~ ;:::; 110 -->!:: en z 100 IIJ

~ ..J 90 ..J

it z ~ 80

70

60

50

40

30

20

[ I , ~l'

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'~ 1\ " ~

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Y1>1S\

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2 :5 4 5 10 15 20 30 . , 60

TIME OF CON :ENTRATION (Tc) iN MINUTES

CURVE 3 : MORE THAN 400m.m. ANNUAL RAINFALL

i RAINFALL INTENSITY - DURATION - FREQUENCY CURVES

5 - 9

~ ~ ~ ~

~ ~ l1li... ~ ~ ~ ~ ~ ....

120

Figure 5.5

H = The difference ill elevation between discharge

point and farthest point on drainage area in

metres

The time of concentration for the corresponding values of L and H

can be directly read from the nomograph given in Figure 5.6.

The degree and cost of repairing damage caused by exceeding the

capacity of a drainage structure combined with hazards and

inconvenience to the public and the classification of the highway,

control the determination of the design frequency and therefore the

design discharge. Frequency with regard to hydraulic design. is the

average interval between discharges equal to or greater than a given

discharge. or the probability that such a discharge will occur in any

one year. For example a 10-year peak discharge is a flow that may

be expected to be equalled or exceeded on an average of once every

10 years or 10 times in 100 years.

The design frequency for the determination of design discharge shall

be selected for the indicated structures shown on Table 5.1.

TABLE 5.1: STORM DESIGN FREQUENCIES (YEARS)

Type of Structure Road Category

A B & C

Bridges 100 50 Culverts 50 25 Roadside ditches 10 10 Stormwater channels 10 10 Stormwater Inlets 10 10 Gutters 10 10 Irish Crossings 50 50

5 .3 .2 Modified Talbot Method

The modified Talbot Formula is defined as

Q = A i

5 - 10 ID738A/C

[

I

, [

KIRPICH'S FORMULA L 1.1 ~ I

tc -'B2 X H 0.38

tc • TIME OF CONCENTRATION

L : HORIZONTALLY PROJECTED LENGTH OF DRAINAGE AREA

H : DIFFERENCE IN ELEVATION BETWEEN DISCHARGE POINT 2

AND FARTHEST POINT ON DRAINAGE AREA.

3

4

%0000 1000 !S 300 800 TOO 6

600 1 500 8 400 9

10000 300 10

tOOO 8000

1000 200 ,fJ)

6000 I!SO LLJ '" ~ GI "-

!SOOO ::l 20 a:;

100 Z E ~ 4000 80

::I: 60 u 30 Z -3000 '" 50 - 0 GI Z ~ "-a:; 40 0 40 ~ E ~ LLJ

I ~O .J 1000 c:: 50 LLJ -J ~ Z ~

::I: 20 LLJ 10 ~ U LLJ C) Z TO U Z 0

80 Z U LLJ LLJ

90 c:: -J 10 u.. LLJ

1000 0 100 u.. u.. 900 8 LLJ 0 800 ::E TOO 6

5 i=

600 4 !SOO ZOO

3

400 Z

300 300

400

ZOO 500

600

TOO 800 900

100 1000

NOMOGRAPH FOR THE TIME OF CONCENTRATION Figure 5.6

- 11

-------

where Q = Discharge in m 31 sec

K = Equivalent rainfall intensity in mmlhour given in

Table 5.a.

C1 = Coefficient for vegetation cover

C2 = Coefficient for slope of drainage area

Ca = Coefficient for shape of drainage area

A = Drainage area in km I

The values of K, C1 ,C2 and C3 are given in Table 5.2.

TABLE 5.2: COEFFICIENTS OF MODIFIED TALBOT FORMULA

Table 5.2.1 Value of 'K'

Size of Drainage Area (1cm2 )

0 - 50 50 - 75 75 - 500

500 - 1000 over 1000 .

Table 5.2.2 Value of 'c ' 1

Vegetative Cover

Desert or mountain, no vegetative Pastured grass or scattered brush

. Scattered trees or dense brush Heavy stand of trees

.

cover

Value of (mm)

30 25

22.5 20

15.2

Value of

0.20 0.17 0.13 0.10

'K'

'c ' 1

ID738A/C

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Table 5.2.3 Value of 'ez'

Slope of Drainage Area Value of 'e2 ' (%)

Above 15 0.50 5 to 15 0.37 1 to 5 0.23 Below 1 0.10

Table 5.2.4 Value of 'e3 '

Shape of Drainage Area Value of 'e3 '

Length equal to width 0.30 Length equal to 2~ times width 0.20 Length equal to 5 times width 0.10

5.3.3 Slope Area Method

This method shall be used for checking the discharges obtained by

Rational and Modified Talbot Methods, whenever sufficient data is

available to carry out determinations using Mannings' formula:

Q = AR 2/3 S 1/2

n

Where Q = Discharge in m3 /sec

R = Hydraulic radius of the river channel in metres

S = Slope of the channel in m/m

n = Roughness coefficient of the channel bed

A = Cross-sectional area of the channel in m 2

5.4 BASIC CRITERIA FOR THE HYDRAULJC DESIGN OF

BRIDGES,

The following basic hydraulic requirements should be met by a bridge

crossing a river. 5 - 13

ID738A/ C

5.4.1 Location

The site selected should enable construction of a safe, economical and

easily maintained crossing, having l'egard to the nature of the

waterway and to the use of such training works as may be appropriate

to deal with adverse natural features.

5.4.2 Design High Water Level and Bridge Height

For the purpose of selecting a minimum height for the bridge

superstructure. the design high water level should normally be

selected after giving due consideration to the fo1lowing:

5.4.3

The maximum historical water levels as observed or recorded or

obtained from local people or as inferred from observed or

recorded levels at another point on the river or waterway from

which levels can reasonably be transferred to the site in

question

The water level derived from frequency analysis and

corresponding to flood of a frequency appropriate to the

importance and value of the structure.

Free Board

An appropriate clearance should be allowed between the design high

water level and the lowest part of the superstructure. The fonowing

items should be taken into account in determining the free board:

The maximum expected height of waves, where not allowed for in

determining the design high-water level

The projection of floating debris.

The liability of the superstructure to damage by water.

A free board of 1.5 metres minimum should be provided over the

maximum expected flood level to the lowest point of the underside of

deck.

5 - 14 ID738A/C

r I

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5.4.4 Length of Bridgeworks

General

The length of bridgeworks should be such that the water way opening

is able to pass the maximum flows without endangering the bridge or

adjacent structures by scour, without creating major maintenance

problems and without causing unacceptable backwater effects

up-stream.

Trial Waterway Gpening Width

Where no other guidance regarding a suitable width of waterway opening

is avaiJable t a first trial width may be selected from the empirical

regime formula for stable alluvial channels

=

Where =

Q ::

C =

CQ i

The waterway surface width in metres at design

discharge

Design discharge in cum I sec

Co-efficient

The suggested range of C is from 3.26 to 4.89. The upper end of the

range should be used for shifting channels in sandy materials, but

for relatively stable channels in more scour-resistant materials the

lower value may be used.

Waterway opening width and cross-sectional area should always be

calculated normal to. the principle direction of flow as it enters the

bridge in major floods.

'The scour, backwater, velocities, etc., should be estimated under

design flow conditions for various widths and then the optimum

arrangement should be selected to satisfy design criteria and minimise

total costs of approaches, foundations, superstructure and training

works.

5 - 15 ID 38A/C

5.4.5 River Type and Characteristics

The physical characteristics of the river should be determined from

geographic, hydrologic, hydraulic and geotecbnical considerations.

Careful site investigations and interpretations of the characteristics

from aerial photographs should be carried out in order to determine

the type of river and water crossing.

5.4.6 Basic Data

The basic data to be col1ected should include maps, charts, airphotos,

data on existing bridges and other structures for evaluation of their

adequacy and performance, water level sand discharge, hydraulic

geometry and channel capacity, geotechnical data, engineering and

control works, and meteorological data.

5.4.7 Bridge Scour

(i) Categories of Scour

The general scour across a controJJed waterway opening is associated

with the construction of flood flows through the opening. The local

scour take place around piers, abutments and noses of guide banks

and is associated with vortex systems induced by obstruction to the

flow. Natural scour in alluvial channels' is associated with variation

in flow conditions and associated channel processes may also take

place. The scour to be expected at the bridge may represent a

combination of these categories of scour.

(ii) General Scour

Lacey's Formula may be used to determine the general depth of scour

at the bridge:

R =

5 - 16 ID738A/C

J

J

1 I I 1 )

J

]

]

:1 ]

J }l

I I I I I J 1

where R = Depth of scour in metres

Q = Discharge intensity in cu.m/sec/m

f = Lacey's silt factor

f = 1. 76 (d )t m where

and

= mean diameter of silt particles in millimetres

(iii) Loca] Scour

The general scour as estimated from the above formula should be

visualised as occurring under a single span bridge without piers in the

channel. Piers placed in the waterway opening tend to produce

additional local scour even where they do not produce any significant

reduction in the net waterway width. In general, the local depth of

scour depends on; the pier width, length, shape, alignment, footing

detai:s, on velocities and depth of flow. on the type and size of bed

material and on the rnte of bed transport. In practice these factors

cannot all be taken into account and it is necessary to use simplified

relationShips derived from model tests, which give an indication of

the worst scour that might occur.

The local scour depth allowance for piers aligned parallel to flow

depending on the shape may vary between 1. OW and 2. OW where W is

the width of the pier. These values should be used as a multiplying

factor to the general scour value (R) obtained by Lacy's Formula.

The local depth of scour may be very much greater in the case of a

skewed pier. The multiplying factors for local scour at skewed piers

to be applied to the above local scour allowances may vary between

unity and 4.5 depending upon the angle of attack and the

length-to-width ratio of the pier. Angles ofa.ttack greater than 5 to

100 should therefore be avoided whenever practicable.

5 - 17 ID738A/C

5.4.8 Guide Banks

Guide banks should be included in the hydraulic design of the

bridge. They should be provided at the bridge abutments on both

banks in order to protect the bridge against outflanking and impart

uniformity and eveness of stream or wadi flows through the bridge.

In the design of guide banks, the depth of scour computed from

Lacey's formula should be modified by the class of scour that is likely

to be met at different places along the guide bank. The following

values shall be used as a guide for the depth of scour for the design

of aprons.

Locality

Nose of guide bank

Transition from nose

to straight

Straight reach of

guide bank

Downstream of bridge

floor

Range

2.00R-2.S0R

1.25R-1.75R

1. OOR-1.50R

1. 75R-2 .25R

Mean

2.2SR

1.50R

1.25R

2.00R

The depth of scour below the apron level would then be XR minus the

depth of water above the apron level at high flood level (where X is

the multiplier h~ the above tables and R is the depth of scour given

by Lacey's formula>.

The layout of the guide banks should be like a bellmouth i.e. the

upstream and downstream parts should take a diverging course. The

length of the upstream part of the guide banks may be made equal to

the bridge, and downstream part may be a tenth to a fifth of the

length of the bridge. The freeboard shall be a minimum of 1.5

metres.

5 - 18 ID738A/C

(

I

J ]

I I J

5.5 BASIC CRITERIA FOR THE HYDRAULIC DESIGN OF

Ct:JLVERTS

The design of highway culverts involves the determination of flow,

hydraulic performance. economy and the type of structure and

its Jc~ntion.

Two major types of culvert flows may be expected: flows with inlet

control and flows with outlet control. For each type of control ,

different factors and formulae are used to compute the hydraulic

capacity of a culvert. Under inlet control, the cross-sectional area of

the culvert barrel. the inlet geometry and the amount of headwater or

pounding at the entrance are 0f primary importance. Outlet control

f involves the additi 'JnaI consideration of the elevation of the tail water , in the outlet channel and the slope, roughness and lengths of the

, culvert barrel.

r

f

I

If normal depth in the culvert is less than the barrel height with the

inlet submerged and outlet free. then this culvert is said to be

flowi~g under inlet control. i. e.. the entrance will not admit water

fast enough to fiJ] the barrel and the discharge is determined by

the entrance conditions. The inlet functions like an orifice for which

Q = Cd A~h

where Q = Discharge in Cli. m / sec.

h = Head on centre line of orifice in metres

A = Area of orifice in sq. metres

g = Acceleration due to gravity in m/sec2

Cd = Orifice coefficient of discharge.

The head required for a given flow Q is therefore

h

5 - 19 ID738A/C

The value of Cd for a sharp-edged entrance without suppression of

the contraction is 0.62 while for a well-rounded entrance Cd

approaches unit.

When the normal depth of design flow is greater than the barrel

height and the inlet is submerged the culvert will flow full. also when

the inlet and outlet of a culvert are submerged the culvert in each

case wiJJ be operating with outlet control. The discharge capacity of

such a culvert wi]] depend on the total head loss (hL ) in the culvert.

=

where

=

=

hv =

=

Where:

Ke =

n =

L =

v =

g =

h + h f + h e v

Entrance loss = K V2 e-

2g

Friction loss in the barrel

Velocity head in the barrel

(Ke + 1 + 29 n 2 L) where V2

2g

Coefficient of culvert entrance

=

=

Manning's roughness coefficient

Length of culvert barrel in metres

V2

2g

V2

2g

Mean velocity of flow in culvert barrel (m/sec)

Acceleration due to gravity (9. Slm / sec 2 )

5 - 20 ID73SA/C

)

r I

I I I I J I

r r

r

f

I

I ~

1

1

I

R = Hydraulic radius (A) in metres where:

(p)

A = Area of flow for fun cross-section (m!)

P = Wetted perimeter (m)

The hydraulic design of the culvert should be based on the selection

of a design lrequency, determination of the

setting up the allowable headwater elevation.

used for the culvert shall be estimated on the

recurrence interval.

design discharge and

The design discharge

basis of a preselected

To facilitate the computati:>ns for the size of drainage culvert,

headwater and discharge capacity, the inlet and outlet control

nomographs for concrete pipe culverts . and concrete box culverts are . given on Figures 5.7 to 5.10.

The culvert should be placed on the same alignment as the natural

stream bed to maintain the natural drainage system. However, pipes

should have a straight alignment and straight entrance and outlet

channels. When natural conditions would require skewed alignment,

the skew mny be reduced or eliminated if necessary and the culvert

shortened by using channel changes.

Generally the culverts wi]] be placed on the stream grade. This

avoids creating unnatural ponding at the inlet or drops at the outlet.

Concrete and steel pipe may be used on all grades up to and

including 20 per cent. However, on grades ranging from 10 per cent

to 21 percent concrete pipe anchors are required to hold pipe in

;osition.

The minimum diameter of pipe culverts across a main roadway shall be

450 mm. Culvert pipes'"~~ated inlets or catch basins in the

roadways shall have a minimum diameter of 300 mm.

5 - 21 ID738A/C

-

4500 300

~200 200 E.ample

3900 0 1050 mm (1.05 m) 0 3.4 cumecs

3600 HW

3300 100 0 H ...... (m)

(1) 25 ;:,6

3000 (2) 2.1 2.2 (3) 2.2 2.3

50 Dinm 2ioo

40

2400 30

20 ~100 /

/" on ./ III ;800 ...

dY' t;

~ ;.po.""

>' 'E I 1500 ./

0 / en 1350 I-a:

W

......... ~ > ..J 1200 ;:) ......... E u :::J 2

......... u I 0

IIJ

~scale (,!) Entrance type a: 900 ex 0

~ U

(1) Square edge with headwall ..J 825 en ex 25 (2) Groove end with headwall Z 0.5 (3) Groove end projecting a: 150 W 0.4 I-~ To use scale (2) or (3)

615 0.3 prOlect horizontally to scale (1). then use straight inclined

600 0.2 line through 0 and Q scales, or reverse as illustrated.

525

0.1

4~0

0.05

3iS

0.03

300

HEADWATER DEPTH FOR CONCRETE PIPE CULVERTS WITH INLET CONTROL

5 - 22

(1) (2) (3)

6 6

5 5

[ 6

4 i 5 4

I 4 " , 3

3

3 1 I

2 2

2

1.5 1.5 , • . 1

1.5

i , .l

Z

~ 1.0 1.0

ti: IIJ 1.0 Q

f .9 .9

.9

.8

J .8

.8

.7 .7 I .7

)

J .6 .6

6

J J .5 .5

.5

I I J

Figure 5.7

I

I ..,-

, .~

r

r

r

r

r " ,

I

I

I

I

• I

I

..

::'0 JOOO

2700

2400

2100 10

1800

1650

!l 1!l00 ~

4

J

'" Co) CU e a I ..... 0

W· c,:) a:: 4 :c u CJ)

E

,:;

,4

,J

:1

1350

1200

/' ,/ 1050

900

825

i~

6i5 1/1 ... ... Gi 600 .§

'E I 5:>5

'0

ffi 4,50

ti ~ 4 E Ji5

..l 4, Z a: IIJ

~L JOO

~ L 40

0 1200 kc

HEAD FOR CONCRETE PIPE CULVERTS FLOWING FULL n=0.011

f) - 23

0,5

o .j

o ...

:: ... .. e

.4

5

1.0

I 2 ..... :r: o 4 III :c 3

.:

Figure 5.8

.. 36 ~ 34 Gi E 32 I -Q 3.0 Example

E "-u QI E

X 2.8 0 CD

o SOOmm

0/8 1.40 cumecs 1m

:::l U

~ 26 en "-0

I- 24 :I: (!)

W :I: 2.~

.;:1 2.0

Z a:: W I-

1.8 ~

HW HW(m)

0

(I) 1.75 1.0 (2) 1.90 1.1 (3) 2.04 1.2

:I:

5 ;: ~ W (!) a:: « :I: (.) CJ)

0 16 u.

0

0

1.4 fi a::

1.2

1.0

.9 /

.8 /

6

3

50

40

30

20

10

5

4

5

.1

angle of wingwall lIart

/

~scale o W.ngwall lIare

(1) 30' to 75' (2) 90' and 15' (3) 0' (extensions of sides)

-Q

"-~ ~ (!)

W :I:

~ CJ)

~ a:: w I-

~

~ o a:: w

/~

~ « w :I:

TO use scalp. (2) or (3) prOlect hortzontally 10 scale (1). then usc str;lIght ."cl.np.d line through o "nd a scales. or reverse as .lIustrated.

HEADWATER DEPTH FOR BOX CULVERTS WITH INLET CONTROL

5 - 24

(1) (2) (3)

8 9 10

I 8 9 8

6 7 6

5 6

I 5

4 5

4

4

I 3 f 3

3

2

2

1.5 1.5

1.0

.9 1.0 1.0

.9 .9 I

.8 .8

.8

7 .7 J

.7

.6 .6 J .6

.5 .5

.5 ] .4

J .4

.35 .3 .3 I

I J

Figure 5.9 J

r

r

r

.,

r '. r

I

r

I

I

to U CI)

E a I

200

100

50

40

JO

20

10

o s

2

Q... 11 -

12

10

5 E tT 4 ."

.3

(!) Z IJJ Z z a: ::J ::::> I-

I HEAD FOR CONCRETE BOX CULVERT FLOWING FULL n=0.011

5 - 25

2

.3

4

.s

1ft CI) .. W E I -:::t:

'l.<:F 0 < IJJ :::t:

-2 ~:P 't H 2.25

3

(.;ln1P~ _IC __ _

----- -4

5'

10

Figure 5.10

5.6 BASIC CRITERIA FOR THE HYDRAULICS OF THE

ROADSIDE DRAINAGE CHANNELS

Stormwater drainage channels alongside the roads are generally

designed as open channel flow. The hydraulics of a storm water

channel design is based on Manning's Formula:

Q =

where:

Q = Design flow in cubic metres/per sec

n = Manning's coefficient of roughness

A = Area of channel in square metres

R = Hydraulic radius in metres

S = Slope of channel in metres per metre

The values of Manning's coefficient 'n' for some types· of channels in

common use are given in Table C. The design of the channel is

facilitate by using the nomograph for the solution of Manning's

formula shown in Figure 5.11.

Roadside ditches shall be designed for a 10-year storm frequency,

however small channels and stream alignments shall be designed for a

50-year frequency.

In providing for erosion protection the actual velocity should be

checked against the maximum safe values for the unprotected earth.

When the velocity exceeds the maximum permissible, means of

reducing velocity to safe levels or for protecting the channel should

be used. TabJe 5.4 lists maximum permissible velocities for various

erodible linings.

Where channel erosion is expected then a stable form of channel lining

should be provided. The channel bed and side-slope shall be lined

5 - 26 ID738A/C

I I

, j

']

J JJ

J J I I J J

S R R ;?/J 5 t/2 V V

~ n

4

.06 15

.2 .08 10

.1 8

1 In 10

DB 6

.06

.2

.04 4

W ll.. 0 ..J en

.02 lit .~

e 2 ~ u E • I&J ~

1 ttl 100 .01 ,

Z E ~ .6 :::;

I ooB 0 C) >-<[ ~ a: ... .006 .8 Z U

u a: 9 ;:) ::::i l- I&J .004

;:) > <[ a: .8 c >-::z:

.6 .002

2 .. \1/\ 1000 001

.0008

0006 4

. 0004 .2 .

6

.0002

S R V n

I In 10000 0001

KEY

NOMOGRAPH FOR SOLUTION OF MANNING'S EQUATION FOR OPEN CHANNEL FLOW

5 - 27

n .004

.006

.OOB

010

.02

.03

C .04 en

-C) Z Z z .06 <[

:i

.08

.1

.2

.3

.4

Figure 5.11

with either rock riprap or concrete for permanent protection and

stabilisation. Fig. 5.12 illustrates the use of rock riprap in roadside

ditches for protection against erosion.

Abrupt changes in the alignment or in grade should be avoided. The

drainage channel should have a grade that produces velocities that

neither erode nor cause deposition in the channel. This optimum

velocity will depend on the size, the shape of the channel, the

quantity of water flowing, the material used to line the channel and

upon the nature of the soil and type of sediment being transported.

The point of discharge of a drainage channel (outfall) into the natural

water course should be given particular attention. The alignment of

the drainage channel should not cause eddies with attendant scour in

the natural water course or near the outfall structure. In erodible

soils, if the flow line of the drainage channel is appreciably higher

than that of the watercourse at the outfall, a spillway or chute should

be provided to discharge the water into the watercourse in order to

prevent erosion in the drainage channel.

The approximate grade of the channel is computed from a topographic

map. To prevent deposition of sediment the minimum gradient for

earth channels should be 0.5 per cent.

For roadside ditches a free board to top of ditch of 0.20 metres and

for small channels a free board of 0.30 metres shall be provided.

5.7 IRISH CROSSINGS

An Irish Crossing is formed by lowering the highway grade to the

streambed level from bank to bank. These crossings are commonly

used across dry drainages or where the day-to-day stream flow is

low.

The Irish Crossing may be vented or it may have culverts, formed by

. partially lowering the highway grade for floods and providing culverts

to handle the day-to-day flow.

5 - 28 ID738A/C

r (

, f

SHOULDER OR C:DGE OF PAVEMENT

O'31l "-... ---- ... --... - " " " /

" /

, ,,'> ,

2cm EXPANSION JOINT EVERY 8m TO BE FILLED WITH IMPREGNATED FIBRE BOARD

H4_-- STUBS----~

-1 0.30~ -! 0.30 t-

I. STUBS 10m. MAXIMUM SPACING ~

SECTION A - A

NOTE - ALL DIMENSIONS ARE IN METRES.

GROUTED RIPRAP UNED DITCH

5 - ?Q

Figure 5.12

The design storm frequency for hydraulic design are as given in

Table 5.1 according to the classification of the road.

The Irish Crossing shall be protected against scour and damage by

undermining, on the upstream and downstream by aprons made from

rock rap or loose riprap gabions. The dimensions of the downstream

apron shall be determined from the depth of scour computed from

Lacey's formula for scour depth. The apron should be carried far

enough along the downstream edge of the crossing to protect against

high water.

The Irish Crossing shall be provided with upstream and downstream

guide banks in order to protect it against outflanking and keep the

wadi channel within the crossing. Guide banks will not be required

when the wadi banks are composed of sound non-erodable rock. The

guide banks shall be protected against scour by covering them with

gabions or stone pitching on the embankment slope and an apron at

the base. The design of the apron shall be based on the depth of

scour as worked out by the Lacey's formula. A minimum free board

of 1.0 metres above the highest flood level shall be provided in the

design of guide banks.

Typical details of Irish Crossing, including details of guide banks are

shown in Figures 5.13 and 5.14.

5.8 SPILLWAYS

A stepped spillway in reinforced concrete at the downstream end of

the culvert for steep side slopes shall be provided as shown on

Figure 5.15. The spillway is a stepped channel with two side walls

and bottom formed in steps, which is required to carry the discharge

from the culvert to the natural water course and for dissipating the

excessive energy before reaching the end of spillway. The width of

spillway is governed by the distance between the wing walls of the

culvert. The minimum width shall however be computed from the

relationship:

Y . = 1.293Q

Z3/2

5 - 30 ID738A/C

1

'1 i J . ,

)

]

]

]

]

) ~ • I I I I I J I

lnl

wi

-I -< "0 -0 ~ r C m -I ~ -r 0 "11

:0 en ::t:

0 :0 0 en ~ z C>

"11 cO c ... (I)

<.n . ..... W

"I "~-J --. ".""""

L J I. DOWNSTREAM APRON ./ UPSTREAM APRON

r -I

2·50 2·00 "301 VARIES (2·00 MIN) 2·50

PROFILE GRADE +12mm. STEEL

t3 FLOW @ O·GOm. c/c. 0·5 THICK ROCK GABIONS 0'50m" ROCK GABIONS tFLOOD POST06 FLOOD POST ANCHOR FOR GABIONS

E:) I ~ -:J 'WAW4': V "::1 K=( J W r H 'q 1(""" ") x ::i:7 1 ~ v= H_ ~n yo;;;> v v 7f, ye;( V D ir:J < i 1: A\iY/X'

o

0 10

REINFORCED CONCRETE CLASS 210/20

RUBBER ASPHALT OF ELASTIC TYPE

~ FLOOD POST .

OPEN MACADAM

10.301

NOTE- ALL DIMENSIONS ARE IN MILLIMETRES UNlESS OTHERWISE INDICATED .

+16mm. BARS

IOmm • STIRRUPS AT O·20mm.c/c.

COVER

REINFORCED CONCRETE CLASS 210/20

SECTION A-A

BANK TO BE PROVIDED UNLESS THE WADI BANKS ARE OF SOUND NON- ERODABLE ROCK

ROCK GABIONS

DUMPED RIPRAP JFLOW ~ D/S

CARRIAGEWAY CONSTRUCTION AT IRISH CROSSING PLAN

HiO

DUMPED RIPRAP

JOINTS

V11

W N

:0 en :t: 0 :0 0 en en -z G')

G') C -c m OJ » Z

"

:!! CO C

"" CD

U1 . -'" ~

ERODABLE ,,~

SOFT BANK /

"

~ WADI BED

'?': ~

~ RIPRAP OR ROCK U/S FLOW

I I

I / ROCK BANK

I 0·50m. THICK LOOSE f

I P-<:-f)~,\\ GAB IONS II DUMPED RIPRAP 0·50m.ROCK GABIONS

I I , TOE WALL .~]' 7a.50~U: :~S~-{R~RAP

ROCK BANK

" ,,"

-t~ j.~.. i . --nUIDEJ~~~ ~~gIEB~~Et& _ . I UNLE E OF SOUND NON ---+-_...... Fe : A. ~:OOABLE ROCK

~ ii /~,

"

, I ,

I I

I I

WADI BANK

PLAN

'.,,11'

OR ROCK GABIONS

SECTION A-A

SECTION B-B

h N.( 0·5

• _________ .... __ .. ,. .. __ t'f""'r.,c·

---

---

where y &; Z = The width and depth of the spillway in metres

Q = The discha.rge in cu. m I sec.

The lower end of the spillway shall be provided with a stilling basin

in the form of a cistern as shown on F1gure 5.15 for dissipating the

surplus energy of the water. The length of the cistern wi)) depend

on the discharge while the depth shall be between 15 and 30 cm below

the bed level of the natural water course. For general guidance the

length of the cistern may be equal to the width of the spillway

channel. A stone apron in the form of a rock gabion 50 cm in

thickness shall be provided at the downstream end of the cistern for

the safety of the whole spilJway structure in keeping the scour away

from it.

The length of the apron will depend on the discharge and sha.]] be

calculated from Lacey's formula:

R = 1.35 [r] ~ Where:

R = The scour depth in metres

q = The discharge intensity in cu.m/sec

f = The Lacey's silt factor

The length of apron shall be equal to 2.23 R, assuming that the

apron wiJ) settle in the scour hole at a 1: 1 side slope.

Special care is required in the excavation and construction of the

spi1Jway, to ensure its placement on well-compacted material so as to

minimise settlement. The spillway should preferably be constructed

as late as possible fo)]owing construction of the embankment.

5 - 33 ID738A/C

--

-

L 'ROCK GASION

• • MAKE UP LEN TH X TO SUIT

TO SUIT 'a VALUE MIN. ONE STEP MAX. 5/7 STEPS

0·10 BLINDING

0·20 CLASS ·C· CONCRETE

6·00 6'00

~ z 5 ..,

SECTION A-A

'y' (F.~M STAN~RD WINGWALL AND APRON DETAILS)

(X + 2W or X + W + W )

20mm 45° CHAMFER

~----..,....-

~i:~ 'Z' •• ! .~." .

SECTION B-B

AREA OF INCREASE TO STD. WINGWALL

:"':'=---CONSTRUCTION JOINTS

f2mm "DOWEL BARS f2mm , DOWEL BARS Q 0·25 CIC AND 0·38 LONG a 0'25c/c AND 0·38 LONG

A

-++-+-> ---t--t--t---+

PLAN NOTES - ALL DIMENSIONS ARE IN METRES UNLESS OTHERWISE INDICATED

- REINFORCEMENT OF SPILLWAY AND APRON STRUCTURE NOT SHOWN.

TYPICAL ARRANGEMENT FOR REINFORCED CONCRETE CULVERT SPILLWAY

5 - 34

Figure 5.15

[

(~

,

I J I I I 1 I

f

,-

-

TABLE 5.3: MANNING'S ROUGHNESS COEFFICIENTS 'n'

A

1. 2.

3.

4.

B.

1.

Open Channels, lined (straight alignment, uniform section)

Concrete formed no finish Concrete bottom with side slopes in rip rap Concrete bottom with side slopes of random stone in mortar Brick masonry

Open Channels, excavated (straight alignment)

Earth Channel, clean recently completed Earth Channel, clean after weathering Earth Channel, with short grass and few ~eeds Earth Channel. in gravelly soil, clean Earth Channel. dragline excavated or dredged clean Earth Channel, dragline excavated light brush on banks Earth Channel, dense weeds high as flood depth Earth Channel, clean bottom. brush on sides Natural Stream Channel. some grass and weeds little or no brush Natural Stream Channel, dense growth of weeds Natural Stream Channel. some weeds light brush on banks Natural Stream Channel, some weeds heavy brush on banks

5 - 35

Mannings' 'n' range

0.013-0.017

0.023-0.033

0.017-0.020 0.014-0.017

0.016-0.01B 0.017-0.020 0.022-0.027 0.022-0.025

0.027-0.033

0.035-0.050 0.08-0.12 0.05-0.0B

0.03-0.035 0.035-0.05

0.035-0.05

0.05-0.07

ID73BA/C

TABLE 5.4: PERMISSIBLE VELOCITIES FOR CHANNELS WITH ERODIBLE LININGS, BASED ON UNIFORM FLOW IN CONTINUOUSLY SET, AGED CHANNELS

Maximum Permissible Velocities (m/sec) for

Water Soil Type or Lining Water Carrying (Earth, No Vegetation) Clear Carrying Sand and

Water Fine Silts Gravel

Fine sand (noncolloidal) 0.45 0.75 0.45 Sandy loam (noncolloidal) 0.5 0.75 0.6 Silt loam (noncolloidal) 0.6 0.9 0.6 Ordinary firm loam 0.75 1.0 0.67 Volcanic ash 0.75 1.0 0.6

Fine gravel 0.75 1.5 1.1 Stiff clay (very colloidal) 1.1 1.5 0.9 Graded, loam to cobbles (colloidal) 1.1 1.5 1.5 Graded, silt to cobbles (colloidal) 1.2 1.7 1.5 Alluvial silts (noncolloidal) 0.6 1.0 0.6

Alluvial silts (colloidal) 1.1 1.5 0.9 Coarse gravel (noncoilloidal) 1.2 1.8 2.0 Cobbles and shingles 1.5 1.7 2.0 Shales and hard pans 1.8 1.8 1.5

5 - 36 ID738A/C

1 )

--1

1 ..

J ;

j

J , J

J J ]

]

J I I J J ~1

r r L· ~

r L·

I .--

. ·.-',:~'r· '.~.:~ .

.... ::t"' • . ;~:t.

", '0;"'

. :'

. ~- ,,': ,"

. ~ ... . "

)

'"!:."

....•.

SECTION6: RoaclMarkings and Furniture

"'.'

...... ;~ ..

"

,_-.'.-

-; ': .

" .

SECTION 6: ROAD MApTnNGS ft1'!'!) FURNITURE

6.1 ROAD MARKINGS

6.1.1 General

Road markings may be defined as markings on the surface of the road

for the control, warning t guidance or information of road users.

They may be used to supplement the regulations or warnings of other

traffic control devices such as traffic signals or signs. Alternatively

they are used alone to produce results that cannot be obtained by the

use of other devices.

Road marking practices adopted in various countries have been

reviewed to produce a set of recommendations to be used for roads in

the Yemen Arab Republic.

6.1.2 Colour

Review of current marking procedures adopted in various countries

indicates that there are mainly two major colour systems. a

single-colour system and a two-colour system. White is used for the

single-colour system. while white and· ye]]ow are used for the

two-colour system.

Single-colour system countries include England (England uses solid

yellow on curbs for parking restrictions but this is not considered a

main colour) Nigeria, the Netherlands, Sweden and Germany.

Two-colour system countries are divided into two groups. The first

uses ye]Jow for restrictions and includes Finland, Japan, USA and

Switzerland. The second uses yeUow for delineating the edges of the

carriageway and inc1udesSaudi Arabia, Italy and Canada.

A two-colour system is recommended for use in the Y A R with the use

of ~Tellow to delineate the edges of the carriageway and white for all

other markings.

6.1.3 Road Marking Materials

The various types of road marking materials currently used include

paints, thermoplastics, adhesive sheet materials, inset mastic asphalt,

hot sprayed plastic, etc. J with paint and thermo-plastics being the

most common.

r,,~Paint is recommended for the YAR with the material being applied to a . ,l! I thickness of 1.5 mm. Where pedestrian crossings, stop lines J special

l')'" \. I letters, arrow~- or symbols are required, the thickness of application ( ~ should be 3 mm.

6.1..4 Road Markings

Road markings are classified into three types, longitudinal (parallel to

the centre line of the carriageway), transverse (perpendicular to the

centre line) and misce]]aneous.

(a) Longitudinal Markings

Four types of longitudinal markings are required, namely:

Warning lines .

Lane lines ~.

Centre of carriageway lines .

Edge of carriageway lines. ,

The recommended types, dimensions and applications of these are

given in TabJe 6.1 and on Figures 6.1a to 6. lc.

(b) Transverse Markings

These include the stop line and give way line.

6 - 2 ID738/D

1 -I

I '1

) j

]

J:' .-

]

]

1 )]

1 1 I I J ]

·T~ JUNCTION AHEAD SIGN*

" 3OOmm. WHITE STOP LINE

1.20mm. WHITE WARNING LINE (6m.lile x 3m. gop)

150mm. x 30m. CONTINUOUS WHITE LINE

150mm. YELLOW EDGE CONTINUATION LINE (O.5m.tine x O.5m. gop)

INTERSECTION WITH NON PRIORITY ROAD SIGN*

~I

r==::::=======::;:1.2:m:·s(min) -- - - - - - -:,..=--====-======-====--""",,

,.", INTERSECTION WITH NON / PRIORITY ROAD SIGN*

150mm. YELLOW EDGE LINE

" TURN LEFT SIGN

T - JUNCTION (DUAL CARRIAGEWAY)

~ ~ I5Omm. YELLOW CONTINUATIOO ~ (Im.I~' "m . .,,)

LINE

120mm. WHITE WARNING LINE (6m. line x 3m. gap)

*DISTANCES FOR POSITIONING OF WARNING SIGNS SHALL BE DETERMINED BY DESIGN SPEED.

ROAD MARKING DETAILS Figure 6.1a

6 - 3

·X"ROAD JUNCTION AHEAD SIGN~

300 mm. WHITE STOP LINE

120 mm. WHITE WARNING LINE (6m.line x 3m. gap)

120 mm. x 30m. CONTINUOUS WHITE LINE

120mm. WHITE WARNING LINE (6m.line x 3m. gap)

INTERSECTION WITH NON ~ PRIORITY ROAD SIGN*

R= 15m. (min)

1.2"m.( min.) ~=-==============~~-----------

I~ R= 15m.(min)

INTERSECTION WITH N:lN PRIORITY ROAD SIGN*

/ ...:.

150mm. YELLOW CDNTINLIATION SIGN LINE (1m. line x 1m. gap)

R = 15m. (min)

ISO mm. YELLOW EDGE CONTINUATION LINE (O'Sm,lin,e x O·Sm. gap)

·X· ROAD JUNCTIClII AHEAD SIGN*

CROSSROAD JUNCTION (DUAL CARRIAGEWAY)

* DISTANCES FOR POSITIONING OF WARNING SIGNS SHALL BE DETERMINED BY DESIGN SPEED.

ROAD MARKING DETAILS Figure 6.1b

6 - 4

I 1

I J

J I I J 1 ,

il

\

1

GIVE WAY SIGN

(O'5m

l20mm. WHITE WARNNG LlNE/ (6m. line x 3m. gop)

120mm. WHITE WARNING LINE ( 6m.line x 3m. gap)

120mm. x 30m. CONTINUOUS WHITE LINE (Minimum)

ISOnvn. YELLOW EDGE CONTINUATION LINE ( 0·5 m. line x 0·5m. gap)

/150 mm. YECLDW EDGE LINE

I ~.~· ________ ~50~Om~.~ _____ ~

T - JUNCTION (SINGLE CARRIAGEWAY)

·1 120nm. WHITE LANE LINE (3m. line x Sm. gap - <SOkph.) (Sm. line x 12m. gop -> SOkph.)

25m. TAPER 3Om.(LAY-BY) 45m. TAPER

l20mm. WHITE LANE LINE (3m. line x Sm. gap - <SOkph) (6m. lite x 12m. gap - >SOkph)

] 15Omm. YEJ EDGE COtmMJATION (O·5m. line I O·Sm. gap)

LAY - BY I BUS STOP

ROAD MARKING DETAILS

6 - 5

LINE

. Figure 6.1c

-----------'-:-

----

The stop line should be placed at locations where it is important to

indicate the point behind which vehicles are required to stop in

compliance with a stop sign or traffic signals. The recommendation

for stop lines are as fonows:

Colour: White·

Width: 0.3 m·

The stop line should be placed 0.3 m behind the edge continuation

Une at junctions. At signalised locations the stop line should be

positioned 2 m prior to the pedestrian crossing and/or 1. 0 m prior to

traffic signals.

The give way line is used in conjunction with, and conveys the

requirements of, the give way (yield) sign. The line is placed 0.3 m

behind the edge continuation line.

Colour: White

Width: 0.15 m Mark: 0.5 m Gap: 0.5 m

Applications of the above are shown on Figures 6.la to 6.lc.

(c) Misce])aneous Markings

This category covers the fol1owing types of marking:

Road Arrows

These should be used to give advance indication of the correct

lane for through or turning traffic at multi-lane intersections

and to give advance warning of a manoeuvre required ahead.

6 - 6 ID738/D

-1

I I

i t'

~

~ t , f

t i

.. 1 J l I I J J J

-";-

Chevron Markings

These are used to deflect drivers from the nose of a

channelising island where a traffic stream divides. The

chevrons are angled to deflect traffic in either stream.

Similarly. chevron markings may be used to extend the nose of a

ehannelising island where two traffic streams merge.

Hatched Markings

These are diagonal and appropriate on the approaches to a

central median island and in certain circumstances, to an island

refuge on a two-way carriageway, with the angle of the hatching

arranged to deflect drivers.

Pedestrian Crossings

These markings are used to delineate the part of a carriageway

which should be used by pedestrians to cross the road. Whilst

regulating pedestrian movements, it acts as a warning to drivers

that pedestrians will be crossing at that point.

For pedestrian crossings, the fol1owing are recommended:

The crossing should consist of alternate black and white

strips having equal widths of 0.5 m Jaid across the full

width of the carriageway, and the stripes immediately

adjacent to the sides of the carriageway being black having

a width ranging from 0.5 m to 1. 3 m

The recommended longitudinal length of the stripes is

2.5 m. However, longer stripes (up to 4.5 m) should be

used where the speed limit exceeds 60 kph. In these

situations, the crossing should be controlled by a set of

traffic lights.

Examples of the applications of the suggested road markings are given

on Figures 6.ld to 6.le.

6 - 7 ID738/D

1000

+-750

L 4000

TYPE A

(FOR SPEEDS < 60 kph)

T 575

~l 1860

j

1500

t 1200

1 6000

300 ~~

,T 570 .L

I 2400

l~ -.-525 ..L

TYPE B

(FOR SPEEDS ) 60 kph)

LANE INDICATION ARROWS

T 860

~ 2800

J

500 150 YELLOW EDGE LINE BLACK STRIPE

WHITE STRIPE

PEDESTRIAN CROSSING

NOTE: ALL DIMENSIONS ARE IN MILLIMETRES

ROAD MARKING DETAILS Rgure 6.1d

6 - 8

I I I I I I I I I I I I I I I I I I I I

f .. i

I

-. I

J

I -,

~ DIRECTION OF TRAFFIC

~~===~,,~~~~~-::-~~e~_J450min

~~~~~~~~~'~ DIRECTION ~ OF TRAFFIC

150

WHITE HATCHING

HATCHING DETAIL

DIRECiJON 300

YELLOW EDGE LINE

_ Or: TRAFr:/~ y~OO

==--=--=~~ f'/ ~YELLOW EDGE LINE

~l, ~ ~90o< < d. L !600 ~ \ ISO (1::45=om::in==-1---lsOT

DIRECTION ~ LWHITE CHEVRON OF TRAFFIC

CHEVRON MARKING DETAIL AT INTERS ECTIONS

~ 150f

(CHEVRONS TO BE REVERSED WHEN TRAFFIC FLOW OCCURS IN OPPOSITE DIRECTIONS)

NOTE: ALL D1MENSICNS ARE IN MILLIMETRES

I ROAD MARKING DETAILS Figur~ 6.1e

6 - 9

6.2 TRAFFIC SIGNS

There are three basic types of traffic signs, namely, regulatory ,

warning and informative.

6.2.1 ReguJatory Signs

These are intended to give notice of requirements, prohibitions or

restrictions with which the driver must compJy. They are genera1ly

circular in shape. There are three types of regulatory signs,

nameJy:

Priority signs

Prohibitory signs

Mandatory signs.

Figure 6. 2a shows the internationally accepted regulatory signs, The

recommmended dimensions for these signs are as fol1ows:

Diameter of stop signs: 900 mm

Height of give way triangle: 900 mm

Diameter of prohibitory and mandatory signs: 900 mm.

Regulatory signs are erected at locations where action is to be taken

or where restrictions apply.

6.2.2 Warning Signs

Warning or danger signs are used to give adequate warning to traffic

and pedestrians of hazardous conditions on or adjacent to the highway

system. Most warning signs are triangular in shape with the 8.pex of

the !iiangle uppermost. The recommended height of the triangle of

the warning signs is 900 mm.

distance of 45 m - 150 m from

visibility distance of 60 m - 75

These signs should be placed at a

the hazard and should have a clear

m. Figure 6. 2b shows some of the

more commonly used warning signs.

6 - 10 ID738/D

r t

f

i I I I I

i f J '\

If

1 I(

I •

REGULATORY SIGNS PR IORITY

STOP

NO "u" TURN

HEIGHT LIMIT

CUSTOMS

T UR'N LEp:'T

PARKING

GIVEWAY

NO ENT RY TO AL L

VEHICLES

SPEED LIMIT

ROUNDABOUT

't,· , .

A HEAD ONLY

HOS PITAL

PROHIBITORY SIGNS

NO ENTRY NO LEFT TURN NO RIGHT TURN

NO ENTRY FOR NO OVERTAKING WIDTH LI MIT TRUCKS EXCEEDING

WEIGHT SHOWN

AXLE LOAD LIMIT OVERALL VEHICLE OVERALL VEHICLE LENGTH LIMIT WEIGHT LIMIT

KEEP LEFT KEEP RIGHT

INFORMATo'RY SIGNS

TELEPHONE FILLING STATION

COUNTDOWN MARKERS

TURN RIGHT

BREAKDOWN SERVICE

200

ISO 100 ISO 100 ISO

'NOTE- ALL DIMENSIONS ARE IN MILLIMETRES

REGULATORY AND INFORMATORY TRAFFIC SIGNS Figure 6.2a

I

LEFT BEND RIGHT BEND DOUBLE BEN!) DOUBLE BEND STEEP ASCENT (FIRST TO THE LEFT) (FIRST TO THE RIGHT)

STEEP DESCENT ROAD NARROWS UNEVEN ROAD SURFACE SEVERE DIP /

LOOSE CHIPPINGS

ROAD WORKS

INTERSECTION WITH NON

PRIORITY ROAD

ROUNDABOUT

OTHER DANGER

FALLING ROCK

TRAFFIC SIGNALS


PRIORITY ROAD ( STA~GERED)

END OF DUAL CARR IAGEWAY'

t· ROO(.'a' 'I

SHARP CHANGE IN DIRECTION

IRISH CROSSING

PEDESTRIAN CROSSING CHILDREN / SCHOOL

AIRFIELD


PRIORITY ROAD

TWO - WAY TRAFFIC AHEAD

MERGING TRAFFIC FROM THE LEFT (MAY BE REVERSED)

T. JUNCTION AHEAD CROSS ROAD

~400 i .. inl

JUNCTION AHEAD

NOTE- ALL DIMENSIONS ARE IN MILLIMETRES

WARNING TRAFFIC SIGNS

SLIPPERY

ROAD SURFACE

DOMESTIC ANIMALS

TWO-WAY TRAFFIC ACROSS

MERGING TRAFFIC FROM THE RIGHT (MAy BE REVERSED)

laoo

WATER DEPTH GAUGE AT

IRISH CROSSING

Figure 6.2b

6.2.3 Informatory Signs

These are used to convey a message to motorists such as services

available, points of interest and other geographical or cultural

information and also to show route designations, destinations,

directions or distances •

. Figure 6.2a shows some of the informatory signs. The size of the

signs showing rou te designations. destinations, etc. f depends on the

contents and the size of the lettering. For the wording it is

recommended to include names and numerals in both Arabic and

English. For the Arabic wording, it is recommended to use the

'Naskh' style rather than the 'AnguJar'. For the English letters and

numerals, it is recommended to use the British Transport Medium

Alphabet complying with the 1968 Geneva Convention on Road Signs

and Signals.

It is proposed that the 'Aleph' height of the 'Naskht script sha]] be

equal to the English letter height (e.g .• capital letter height).

Details of these letters, together with signface spacing arrangements

for legends, symbols and borders. etc .• are shown on Figure 6.2c.

6.2.4 Siting. Orientation and Foundations

(a) Siting

The m:'1imum horizontal distance between the post of the sign and the

edge of the carriageway should be 0.6 m.

The minimum vertical distance between the bottom of the traffic sign

and the carriageway leveJ should be:

2.0 m in urban areas. However, where direction signs are

mounted on pedestrian guard rails or islands this distance may

be reduced to 0.9 m.

1.50 m in rural areas.

6 - 13 ID738/D

(b) Orientation

To reduce the effects of specular glare, signs should be set to an

angle of 93 0 away from the general alignment of the near-side edge of

the carriageway.

(c) Foundations

Figures 6. 2d to 6. 2f show recommended foundations details for single,

dual and multi-post traffic signs. For large signs it is recommended

to take into consideration the wind velocity and the safe bearing

pressure of the soil in order to obtain the sizes of the foundation and

the reinforcement details. The details of a standard kilometre post

are also shown on Figure 6.2g.

6.3 GUARD RAILS AND CRASH BARRIERS

~.\,

Guard rails are used where vehicles accidently leaving the road would ......

be subjected to hazard. They are largely used on sections of high

embankment, but their installation may be justified in the following

si tuations :

At roadside obstacles; non traversable hazards and fixed objects

close to the travelled way

At approaches to structures

At an isolated sharp curve on a road otherwise built to higher

standards

At locations subject to fog

At crossings of water courses

On narrow medians of dual carriageway roads.

The need to provide guard rails at embankment sections is governed

by the height of embankment and its side slope. Consideration

should be given to the instalJation of guard rails where the height of

the embankment is higher than 3 m and the side slopes are steeper

than 4: 1.

6 - 14 ID738/D

r (

I ; I I I t

1

'. -

-

'--

-

ARABIC LETTERING --+I TO 'NASKH' SCRIPT

ENGLISH LETTERING TO BRITISH TRANSPORT MEDIUM

I Y22Y2

DIRECTION SIGN

LEGENDS VARY

IY2~ ~ 1-'1' (ARABIC MINIMUM LENGTH TO BE EQUIVALENT OF ENGLISH LENGTH)

3

12 3x

8 2x

1\12

1112

ADVANCE

T ['7'7:;77I77r~~\7'77:'1

+~~~~

+ trrIT:7:~~77 8

-L 1illJillJ21ill2lL----L~

1

I· 4 • 16 -I

ARROW DETAIL

NOTE: ALL DIMENSIONS SHOWN ARE IN STROKE WIDTHS (s/w), UNLESS OTHERWISE SHOWN, AND RELATE TO ENGLISH LOWER CASE

. LETTERS ('x' HEIGHT)

SIGN FACE DETAILS

DIRECTION

3x

2 HP t-I T ~

-!:Oct

T .L

R=3

SIGN

a m'-"'" ALEPH HEIGHT

.. ~ASE LINE

6

TILE DETAIL

. Figure 6.2c

..

0'1

0'1

., • en -C> Z

" 0 ~ r 0 0

~ 0 z > z c > en en m ~ m ~ c m

~ r en

:n co r:: CiJ en N 0.

. ' .. •

3·OOm. MIN. TO EDGE OF PAVEMENT*

l'Om >--MIN.

SHOOLDER

'90

·50

". ~-- 1Ij--~ -r'- , ~ r,-~

/',1",

'18 6mm.HARD ::T RUBBEIl:\ ·10 WASHER

.52 2Onvn.HARD RUBBER

.10 I WASHER ~

W-;;~

10mm.8OLTS AND NUTS. NUTS TACK WELDED TO BOLTS.

·45 '45 a.W W go:: 0::

W (I) <t <t ..J ZZ ..J III 0 <t <t <t III 0:: ii: C) 0:: => <t Z=> 0:: > o~--

·10

if;~f:'M;"}1;;kJ ,. :·t, " ~.

~'{'~~I f;';::'1 1·80 f:~:',:l'f:;"'I' ~;:r~Jf),~; t, ::,Wf.~.::) ~':J';:";;: '.10

.50

K>JI1

~ E f~ a.o ,0 ~N ..:..

POST -I

~~2;!-ij ':~;~1 :~~~:; ~~; ~r{. 3n;

,", . '0.'

SECTION A-A

IRON BARS

CLASS 210/25 CONCRETE

WARNING AND REGULATORY SIGNS

NOTES : I. ALL DIMENSIONS IN METRES UNLESS OTHERWISE SHCNlN. 2, * 0·50m. MIN. TO EDGE OF CURBED PAVEMENT 3, ALL STEEL POSTS HAVE 3" INTERNAL DIAMETER

~. ~ I -r-' ...,-...

\

w 'I I' B1 '-+18 I .15

!IiIIj:"""'''''', ~'i """f""""" 1 . . I

~ III <t

7nvn.HARD RUBBER WASHER

fimm.HARD RUBBER WASHER

'-.. IOrrm.BOLTS N4 ,/NUTS.MJTS TJV:,:

0= ~

r~15 W!5 I 3!5W W!5 ~:J

I, ~:

::>=> STEEL POST E ~

I 2~

~i I

/4W/5 JI

W .1

3Omm.HARD RUBBER -'I WASHER

jWEll£D 10 BOl

STEEL POST

,~11~!~! SECTION B-B

~~~-I4e DEFORMED BARS

~~~IOeIRON BARS

~~-CLASS 210/25 CONCRETE

INFORMATORY AND PLACE IDENTIFICATION SIGNS

3.0m. TO W/5 EDGE OF PAVEMENT'"

3" INTERNAL DIAMETER ----II STEEL POST

'3W/10

W

. 3W/1O

'18 :-·15 -

-'15

w/5 I

I W/5 W/5 _I ·70 I

I- W c .. -I

LARGE TRAFFIC SIGNS

NOTES: I. ALL DIMENSIONS IN METRES UNLESS OTHERWISE SHOWN. 2 .... 0·50m. MIN. TO EDGE OF ItURBED PAVEMENT 3.ALL STEEL POSTS HAVE 3' INTERNAL DIAMETER

SIGN POST LOCATION AND ASSEMBLY DETAILS

. 6 - 17

7mm. HARD RUBBER ---. WASHER.

15mm. HARD 10mm. BOLTS AND RUBBER~tt-r---t NUTS. NUTS TACK WASHER WELDED TO BOLTS.

'3Omm.HARD RUBBER -' WASHER

SECTION C-C

Figure 6.2e

[

(

I I

..... :::r z cd: cd: a:: co ::J ~ a:: - -o 10 N ·1

·80

T

1

D

1·00 MIN.

* a:: UJ 0 ...J ;:) 0 :J: (/l

u.

STEEL POST 0 ~ u cd: co

10 IS IRON BAR

CLASS 210/25 CONCRETE

DIRECTION SIGNS

NOTES I. ALL DIMENSIONS IN METRES UNLESS OTHERWISE SHOWN. 2. * 0·5m. TO EDGE OF CURBED PAVEMENT 3.ALL STEEL POSTS HAVE 3"INTERNAL DIAMETER

6mm.HARD RUBBER_ WASHER

SECTION 0-0

SIGN POST LOCATION AND ASSEMBLY DETAILS

6 - 18

10mm. BOLTS AND NUTS. NUTS TACK WELDED TO BOLTS

Figur:e 6.2f

I ~7 ~. ~

~, 't ~ ........

900 ,~ '( 675

~~ 1"""/ ~~A~

A

600

+-<0, ~<O FACE A

75 ::::l:-~

100 .'~ 5O:I

100 C· •

.,-/

- GREEN RER..ECTIVE PAINT ~ LETTERS AND FIGURES ON KILOMETRE POST ,

900 - WHITE REFLECTIVE

PAINT FOR BODY

~~ r 6 r

II I II J L L_JL_J I L _____ JJ ±fC

FRONT ELEVATION FACE B

16 OIA. MAIN ROAD

375

L GROUT 601A. LINKS @ 225 C-C

PLAN CROSS SECTION

STANDARD KILOMETRE POST

REFLECTIVE DISC ro(min)

to .:.: ... : .. :.:::::' 150 ... -1. . -'-T

350 t--2f; NOT TO EXCEED :350 I METRE ABOVE +- CARRIAGEWAY 225 SURFACE.

to 350 ..i.-. J

HAZARD MARKER NOTE: ALL DIMENSIONS ARE IN MILLIMETRES

75 T

; ,

. ',1

'1

I

1 j

I I '1

t

f

1

J ]

]

,:J

J I I J

DETAILS OF HAZARD MARKER AND KILOMETRE POST Figure 6.2g J 6 - 19

i'J

T

T

T

Guard rails are expensive and require continual maintenance, hence

they should not be indiscriminately used. Field inspection should be

carried out to assess the need of guard rails at the less obvious

locations by considering the following factors:

Heights of embankment and its side slope

Road width

Accident bJackspots

Visibility

Climatic con di tions

Speed and volume of traffic.

Guard rails are deSigned to resist impact by deflecting the vehicle so

that it continues to move at a reduced velocity along the guard rail.

Typical guard rail details are given on Figures 6. 3a and 6. Sb.

At escarpments. the use of reinforced concrete crash barriers is

recommended. Dimensions and details are given on Figure 6. 3c.

6.3d. 6.3e and 6.3f.

6.4 HAZARD MARKERS

Hazard markers can be used tc indicate the edge of the carriageway

on embankments. mountain roads and other points where special

dangers exist. Typical details of a hazard mRr 1q;r post are shown in

Figure 6. 2g.

6 - 20 ID738/D

0'1

IV

r-0 0 ~ -0 z 0 -n C> c » :n c :n ~ r-en

:!! to C -t CD

en .

EDGE OF PAVEMENT DIRECTION OF TRAFFIC ~

EDGE OF SHOULDER ~----~------------~~

[ , i t-=== I I 1 I It II it t t ttl 1.14 ,..-..--- i I I I I - I I

11.40 15.24 I LIMITS OF: 11.40 I.. SPACING OF POSTS I. 90 • .. SPACING OF POSTS 3.81 ol·CULVERT .. SPACING OF POSTS I. 90 •

APPROACH END NORMAL STRETCH HIGH FILL DEPARTURE END OR HAZARD

GUARD RAIL FOR BOX CULVERTS, HIGH FILL (>3m) OR HAZARD

DIRECTION OF TRAFFIC ~

0.30-, EDGE OF HARD SHOULDER

"l 1 1:

LAP IN DIRECTION OF TRAFFIC

EDGE OF PAVEMENT

I

10.1 PARABOLIC FLARE L: II. 40 NORMAL STRETCH GUARD RAIL FACE

ANCHOR END RAIL -' SPACING OF POSTS I. 90 SPACING OF POSTS 3.81

TYPICAL APPROACH END

DIRECTION OF TRAFFIC --. EDGE OF PAVEMENT DIRECTION OF TRAFFIC ......

POSfS~-O:95c/c OVER 11.40 LENGTH ADJACENT o CONCRETE BARRIER

r----EDGE OF PAVEMENT

GUARD RAIL FACE

1: 1.14~

I 11.40 I • APPROACH END 0

PACKER

CONCRETE PARAPET

GUARD RAIL AT BRIDGE APPROACH

EDGE OF HARD SHOULDER

x

NORMAL STRETCH SPACING OF POSTS

3.81

1: r 1: r

POSTS AT 1.90 clc FOR 11.40

TYPICAL DEPARTURE END

ANCHOR EN RAIL WITHOI FLARE

w 0) NOTE ALL DIMENS'ONS ARE IN METr""

-- '~i'<~

~ .... "'- - _ .. .....

TOLERANCE

..... ___ ~V.;::.E~RG;:.:E=-___ ~ ___ , __ "\_'-"~ :-_C'.:,;.,:_R~~_

1.00

N ,.. o

Z :e 2

10 ,.., o

'(

I

" • .. " ~ !t "

,.-___ BLOCK. WOOD OR SAME AS POST SECTION

0,30 MIN, FOR NORMAL STRETCH

151.44 TO 0,30 FOR APPROACH END 12 GAUGE x 3. BI ARMCO FLEX

~-mr--c,rL SEAM OR APPROVED EQUAL

~, ": !.:

" . ':.,:

~.

(THICKNESS 2,74mm)

10 It)

o

ARMCO POST UNP 120 OR APPROVED EQUAL

POST HOLES TO BE BACKFILLED LEAN CONCRETE OR COMPACTED >95% ~RY DENSITY

TYPICAL POST DETAIL

ANCHOR POST~

f

WITH TO

(ALL LAPS IN THE DIRECTION OF TRAFFIC)

TYPICAL END RAIL ANCHORAGE FOR APPROACH AND DEPARTURE ENDS

'\ FO

.027

0.70

l I

~r::.;~ ~~.-]~ o

I~ 0.084 r 0.002

(USED ON L Y WHERE TAMPING IS OMITTED)

SECTION THROUGH W - BEAM W - BEAM TERMINAL SECTION

NOTE - ALL DIMENSIONS ARE IN METRES

DETAILS OF GUARD RAIL Figure 6.3b

6 - 22

REMOVABLE LIFTING DEVICE

WELDED ANCHOR ----_

INSERTS FOR CABLE SUPPORTS IN BARRIER WALL

BARRIER CONCRETE CLASS 270/20

REINF BARS 12 mm 0 AT 300mm CIC BOTH WAYS AT 40 mm COVER (MIN I

PREFORMED 60 mm 0 SLOT TO BE PRESSURE GROUTED AFTER PLACEMENT OF BARRIER ( NOT REQUIRED IF BARRIER IS CAST

850

IN SITU )-------------~-_1

DOWEL BARS 30 mm 0 450mm ---_+_. LONG AT I· 25 CIC PRESET IN BASE CONCRETE

O' 100 X 0·300 DRAINAGE SLOT _____ "

AS REOUIRED ALONG CENTRAL MEDIAN. AT 5· OOm .SPACING

CONST JT (LEVEl)---------~

180

20 mm CHAMFER

BASE CONCRETE CLASS 210/50 ---- ~ ....... .,.;.:,;.:,...;..:.;;.;~::..;.;;;..:;:;:f_"_'~p;.:.".,~ WITH SQUARE MESH FABRIC A252 ( 200 " TO BS 4483 BOTH WAYS. ~ 150

TOP AND BOTTOM

NOTE ALL DIMENSIONS ARE IN MILLIMETRES

DETAIL OF CRASH BARRIER

6 - 23

[

I

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j I.

I ! f 4'

.. i

I I .1

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Figure 6.3c J .J .., $i ~

5x 2.5 PH'!:'I c:: : ,., 0';

L r 0.48r 1t:=::J::====::J::====:::C====:=C====:::C====::::J

j

5x2.5 PANELS: 12.5 1 TOP OF BARRI~ 0 •

~ _ FINISHED GROUND LINE

r--lt==:IC===:::JC=====:J~:/===~======~======~ 0.85-*-1 F i ~ I b ~ A =to.05

ELEVATION

SINGLE FACE BARRIER TERMINATION DETAIL

-

I-51t 2.5 PANELS: 12.5 .\

0.71.ct PLAN

TOP OF BARRIER:. !" 51t2.5 PANELS: 12.5

11.0005 FINISHED GROUND .LINE

0.8~t I I I /' .:::::::: I i

F E 0 C B A +

ELEVATION

DOUBLE FACE BARRIER TERMINATION DETAIL

----F ~ __ ---F

"';""---E ---E

----0 ---0

----c --c

---B

t=:==:::::j' -A f--------=!- A

END VIEW END VIEW

SINGLE FACE BARRIER DOUBLE FACE BARRIER

":)TE ALL DIMENSIONS ARE IN METRES

TYPICAL DETAILS OF CRASH BARRIERS Figure 6.3d

6 - 24

t.

......

I

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N VI

r 0 0 ~ -0 Z

~ 0 :u » en ::J: m » :IJ ::0 -m :u en

,.. _. Ul C ... CD CJ)

W CD

....... '--i

EMBANKMENT WIDENED

10 ACCOMMODATE B~~~~~_ -----

SIDEWALK

CURB LINE CARRIAGEWAY

rn 0.85

EMBANKMENT SLOPE

- - ~ .-..

VARIES

fULL HEIGHT BARRIER

rA ....... ~-:r;.-.:' •• .:.

L!

miDGE

PA PET

i ...

PLAN

~

VARIES

FULL HEIGHT BARRIER

EMBANKMENT WIDENED

£_~~~CCOMMODATE BARRIER

;:·:-?~!;R?;:;:·,·i! .. :···,.· 'fllOnpzm -----SIDEWALK

CURB LINE

CARRIAGEWAY

(AT BRIDGE APPROACHES WITH SIDEWALK)

SINGLE FACE CONCRETE BARRIER

BEHIND SIDEWALK

SECTION A - A

'...-' ..... --- - - - --

LEGEND

I;.;.;.; .....•. ) FULL HEIGHT, SINGLE FACE CONCRETE BARRIER .,. (FOR DETAILS SEE FIGURE 6.3d)

Vll.llllJ BARRIER TERMINATION SECTION (FOR DETAILS SEE FIGURE 6.3d)

t=::::I TRANSITION SECTION FROM BRIDGE PARAPET

IHlIHfJll SIDEWALK rn BRIDGE

.... DIRECTION OF TRAFFIC FLOW

NOTE-ALL DIMENSIONS ARE N METRES

.... )4',

~ .. ".~;~ ..- .. ~,."",*, ..

•

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0 :0 » en ::t OJ » :0 :0 -m :u en

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EMBANKMENT WDENED TO ACCOMMODATE BARRI~l

-- -----=

SHOULDER

CARRIAGEWAY

.. .. ~'.'I.; ...

\ARIES FUll HEIGHT

BARRIER

r;

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20 I~

l! ~

1I1Iil\" '.:9f . ~.' '; -r~~" -r- MI"

r71RIDGE

~RAPE

t ~, .~IJ ". • '\ • ''CruRB LINE

PLAN

,",~ .... ~

\ARIES FUll HEIGHT

BARRIER

.........

~

~' *'I, -r

EMBANKMENT WIDENED L 10 ACCOMMODATE BARRIER

... _-SHOULDER OR SHYAWAY

CARRIAGEWt! ~

(AT BRIDGE APPROACHES WITH HARD SHOOLDER OR SHYAWAY)

EMBANKMENT SLOPE

ri SINGLE FACE . 'CONCRETE BARRIER

BEHIND SHWlDER OR SHYAWAY

SECTION B - B

LEGEND

rnm FULL HEIGHT. SINGLE FACE CONCRETE BARRIER ".:". (FOR DETAILS SEE FIGURE 6.3d)

t7lZ1lllJ BARRIER TERMINATION SECTION (FOR DETAILS SEE FIGURE 6.3d)

c::::=:J TRANSITION SECTION FROM BRIDGE PARAPET

IIIIIIIIIII SIDEWALK ON BRIDGE

.... DIRECTION CF TRAFFIC FLOW

NOTES I. ALL DIMENSIONS ARE IN METRES 2. BEHIND CONCRETE BARRIER WEEP HOLE

SLOPE PROTECTION WILL BE PROVIDED

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SECTION 7: STRUCTURES

7.1 INTRODUCTION

In any highway project the need to cross wadis, valleys and other

obstacles often arises. Apart from major tunnels, such crossings

represent critical points of the highway both during and after

execution of the project. For this reason, it is important to consider

all aspects of bridge design, construction and maintenance. Some of

the more important features of bridge design and construction are

described here. Such a description can, however, be only brief

since each aspect Is a field of speciality in itself.

It must be noted that like other disciplines of applied science, the

technique of bridge design and construction evolves continuously and

must be reviewed periodically to account for changing circumstances,

adapt to new techniques of analysis and adopt new materials,

equipment and plant.

7.2 CONCEPT

Conceptual design forms the most important phase of the design. It

requires an appreciation of every facet of bridge design, construction

and maintenance.

The assessment of materials and labour available locally, including the

degree to wrich the transfer of constructional technology is

practicable are also called for. The overall economy of the

structures, the amount of problems encountered during construction,

durability and aesthetic quality and th~ degree of maintenance

subsequently necessary are all directly or indirectly attributable to

the conceptual design. It is therefore, imperative that conceptual

designs of bridges be carried out by persons of great experience and

vision with established stature in their profession.

7.3 LOADING

Bridge loadings adopted by the industrialised countries are invariably

linked to statutes and enforceable by law, which restrict the gross

7 - 1 ID738/F

and axle weights of commercial vehicles including their speeds. widths

and laden heights t and in some cases, the lanes to which they must

adhere to. Where such laws either do not exist. or if they exist

where there is no mechanism of enforcing them. the loading to be

used for bridge design must be viewed with caution. This must of

course be balanced by the need to design and build economic

structures by not being over conservative.

The AASHTO loading specifications provide a good basis because not

only are they widely recognised. but also they are used in most

countries of the Middle East in various derivative forms. One such

derivative is the bridge loading currently used in the Kingdom of

Saudi Arabia, shown on Figure 7.1. In view of the close

geographical and commercial link with Saudi Arabia. it is proposed

that the loading shown on Figure 7.1 be adopted for the design of

highway bridges in the Yemen Arab Republic.

The loads are to be applied in accordance with AASHTO specifications

and the design of structural components should accord with AASHTO •.

Environmental factors such as wi~d speed, duration and intensity of

rainfall, temperature variation and siesmicity of the region will have

to be determined from existing records where such records exist.

Where records are not available, field measurements will have to be

made. When such data are available, it should be possible to

formulate design parameters in the manner given by AASHTO or other

internationally recognised standards.

7.4 BRIDGE LOCATION

It is important to integrate bridge design with the design of highway

alignment and profUe. The two processes are interactive and any

attempt to divorce the two operations will result in badly located

structures which are difficult to build and costly to maintain.

of the basic rules are:

Some

Not to locate a bridge on a sag curve. Impact forces are

greater and there is the danger of waterlogging which can cause

corrosion of reinforcing and prestressing steels.

7 - 2 ID738/F

r [

I

T-

z *~I ~l ,I/t g Illi. 4·30 :1- Variable :1 (4-30m_ to g{)Om.)

~llE! Cf) ~ u ::> a:

~ 4~kN ' _____ J l~kN ~ --~ -§~B ~ T ~

I g I ~ .:.. ~~ ~ .,3= -' ~~ - ~

40kN -----~ 13tkNf ~-00

~..J .... (3 .-

V= Variable spacing (4'30m_ to g-OOm) inclusive. Spacing to be used is that which produces maltimum stresses.

* In the design of orthotropic steel decks (excluding transverse beans) one oxle load of

(19-88 Tons) or two altll loads of 130kN (13'26 Tons) each ,spaced I-20M. apart may be used whichever produces the greater stresses ** For the slab design the centre line of wheels shall be assumed 30cm. from the face of the curb.

All dimensions are in metres.

(a) STANDARD TRUCK LOADING

1150 kN (15·30 Tons) FOR MOMENT

J--- CONCENTRATED LOAD 220 kN (22-43 Tons) FOR SHEAR

UNIFORM LOAD 20 kN PER LINEAR METRE (2·04 Tons)

OF LOAD LANE

(b) STANDARD LANE LOADING

PROPO:::::> BRIDGE LOADING

7 - 3

-

tp I-0 --z

~

0 0 0

2 U)

0 a:

U) <t 6 0

Z <t I-Cf)

Figure 7.1

-= I

Not to locate a bridge on a tight curve. Horizontal forces are

greater and it is easy for incompetent designers to overlook the

effect of curvature. The bridge is also difficult to build.

A void changes of crossfall along the bridge in order to avert

complex construction and unsightly appearance. Where varying

crossfall is unavoidable, then the superelevation application

should be as long as practicable and uniformly applied from one

end of the bridge to the other in order to give a pleasing effect

of carriageway edges and paraphet profiles.

Not to introduce concurrent high horizontal and vertical curves

within the bridge length. It is not only difficult to build but

also visually unattractive.

Bridge design must also interface with the design of services, ducts

and other facilities that have to be carried on the bridge. Some

forms of deck construction will not accommodate even the smallest of

ducts while others are ideal for services.

7.5 BRIDGE SUPERSTRUCTURES

The most common forms of bridge deck using reinforced or

prestressed concrete are shown on Figures 7.2a to 7.2e. Bridge

decks using steel, either in the form of plate girders or box sections

have not been included principally for economic reasons. At present,

because all structural steel will have to be imported into the Y AR,

steel bridges are not economically viable. Technically, steel bridges

are more susceptible to fatigue failure than concrete and thus require

a high degree of. skill, quality control and testing during

manufacture. Finally, steel bridges require a stricter regime of

maintenance than' concrete ·bridges.

In general, beam-and-slab type of bridge decks are more sensitive to

axle loads than the slab or box-girder types and are therefore more

prone to damage if subjected to over-loaded trucks. Again in

7 - 4 ID738/F

r I

SIDEWALK

I

I. L

OVERALL WIDTH

WIDTH (CURB TO CURBI

L

.-THICKNESS OF TOP SLAB

t

L .\. o

L .1 PRECAST BEAMS WITH CONTINUOUS R8NFORCED CONCRETE SLAB

(a) TYPE 1

r SIDEWALl

I I-

OVERALL WIDTH

WIDTH (CURB TO. CURB)

THICKNESS OF TOP SLAB

L L L

., ·rEWAL!'1

-I PRE:.~.:T BEAMS WITH INTERMEDIATE R8NFORCED TOP SLAB

(b) TYPE 2

r SIDEWALK

I- -I-

I

~ L

OVERALL WIDTH

WIDTH (CURB TO CURB)

I

.\.

DEPTH OF CONSTRUCTION

L

SIDEWALK

, -I

L

PRECAST BEAMS WITH CONTINUOUS R8NFORCED CONCRETE SLAB

(c) TYPE 3

BRIDGE DECK TYPES Figure 7.2a

7 - 5

OVERALL WIDTH


I

L L

I

.1. L

RECTANGULAR PRECAST BEAMS WITH CONTINUOUS R8NFORCED CONCRETE SLAB

(d) TYPE 4

I

I· L

OVERALL WIDTH


-I.

DEPTH OF CONSTUCTION

L -I. IN-SITU BEAM AND SLAB DECK

(e) . TYPE 5

L .1

OVERALL WIDTH I r -SIOEWALK WIDTH (CURB TO CURB) SIDEWALK r -\' -\' -\

~~;.~I t-----~L.. _________________ ....J~---- j

BRIDGE DECK TYPES

IN-SITU SaJOSLAB DECK

(f) TYPE 6

7 - 6

Figure 7.2b

(

(

I I l 1

06 MINlI ~

06 MIN~ ~

CARRIAGEWAY WIDTH

IN-SITU VOOEO CONCRETE SLAB DECK (g) TYPE 7

CARRIAGEWAY WIDTH

00

.1 --l li°'; MIN.

PRECAST OR IN - SITU BOX GIRDER DECK . (h) TYPE 8

NOTE - All dimensions ore in metres.

BRIDGE DECK TYPES Figure 7.2c

7 - 7

:I: (.) a:: ~

I ~-{

--' -z ~ CI)

1L 0

:I: I-(!) z ILl -'

,... ...... -'

,... ...... -'

,... ...... -'

BRIDGE DECK TYPES

,.------.. I I I I ~ I

~::::::l...- - - -~ I ~ ----7 .... ;>-'-...1

I I /

/

\ \

\ \ ....... -, b:===;i----==-:.........> I

'" I (' I : I L... ____ ....l

7 - 8

W (!)m Ow -a.. 0:>-CDf-J: u:= 0:-«

Figure 7.2d

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BRIDGE DECK TYPES

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7 - 9

~ ~ a. Wo o~ ~W c..:>a. W>-o~ W ....J ::.. ro-ex: c: ex: >

Figure 7.2e

,

general, prestressing bridge decks produce more durable structures

because of the possibility of eliminating cracks in~uced by high

tensile strain in the concrete.

7.6 BRIDGE SUBSTRUCTURES

Typical bridge piers and bridge abutments are shown on

Figures 7. 3a, 7. 3b and 7.4. Except for major bridges of a certain

type whose piers are often of steel construction, bridge piers and

abutments are today built exclusively in concrete. Depending on the

subsoil conditions at the bridge site, piers and abutments may be

supported on piles or pad footings. Where the salt content of the

soil surrounding the substructure is high, sulphate resisting cement

with or without additional protective membrane may have to be used.

As a guide, Table 49 of the British Standard Code of Practice CP 110

is recommended.

7.7 BRIDGE AR TI CULA TION

It is important to allow bridge decks to undergo dimensional changes

with the rise and fall of air temperature. Otherwise stresses are

built up and local damage results. To facilitate such movements,

bearings are provided to allow the deck not only to expand and

contract freely, but also to deflect and rotate on the supports when

transversed by vehicles.

For small span bridg'1s, the most common type of bearings used today

is the elastomeric type. Though simple and convenient, great care is

necessary in their design, quality control and installation. From

experience, the following is recommended in respect of elastomeric

bearings:

Design to BS 5400: Part 9.

Carry out materials test to BS 5400: Part 9 except for a ozone

resistance test which should be performed in accordance with

ASTM D1149.

Carry out vertical load test to 1.5 times rated load in accordance

with BS 5400: Part 9.

7 - 10 ID738/F

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MAX. PIER HT.

PIER BASE

MAX. PIER HT.

PIER BASE

<t BRIDGE I I

LENGTH 0 PIER WIDTH OF

WALL

NATURAL GROUND LEVEL

WALL TYPE PIER

(a) TYPE 1

~ BRIDGE I

LENGTH OF'CROSSHEAD WIDTH OF CROSSHEAD

] MAX. DEPTH

~ ____ ~ ___ .,....:::=--_ _ OF CROSSHEAD

ENGTH

I

OF I SUPPORTIN PIER

I

WIDTH OF SUPPORTING PIER


WALL TYPE PIER VV1TH CROSSHEAD

(b) TYPE 2

BRIDGE PIER TYPES

7 - 11

<t PIER i I I

Figure 7.3a

-

-

-

---

EQUAL COLUM SPACING

--. N I

x. MA PIE RHT.

..

~

---PIER B ASE

MAX. PIER HT.

PIER BASE

L

It. BRIDGE

LENGTH OF!CROSSHEAD

I L , L .J .

I

L

•

I:

WIDTH OF CROSSHEAD

--. MAX. DEPTH --L OF CROSSHEAD

CDWM NS

I

ATURAL GROUND LEVEl. ;

MUL TJPLE COLUMNS AND CROSSHEAD

(c) TYPE 3

LENGTH

ct BRIDGE

OFlcROSSHEAD

'MAX. DEPTH -1.. OF CROSSHEAD


TWO COLUMNS VVlTH BALANCED CROSSHEAD

(d) TYPE 4

BRIDGE PIER TYPES

7 - 12

t PIER I

I WIDTH OF CROSSHEAD

I I I I I I I

.'1 I I I

-I

.1

1 I I I I I

Figure 7e3bl

I

1

I SIDE ELEVATION FRONT ELEVATION

(a) RETAINING WITH CONSTANT OR VARYING THICKNESS

TYPE 1

TRANSITION SLAB

I SIDE ELEVATION FRONT ELEVATION

TRANSITION SLAB

(b) SPILLWAY ABUTMENT

TYPE 2

I I

I I I I

I I

I I I I I I I I I

I

, • I I I

1 I 1

I I I I I

, 1 1

(e) RETAINING WALL WITH BUTTRESS SUPPORT

TYPE 3

TYPES OF BRIDGE ABUTMENT

7 - 13

: I I , I I

I I

i I I I I I

1 1

I

SU PPORT LUMNS CO

J

COUNTERFORTS

I

Figure 7.4

Carry out shear test at 50 per cent and 80 per cent rated

vertical load to full shear strain in accordance with BS 5400:

Part 9.

Install bearings only in the horizontal plane.

Use laminated elastomeric bearings instead of plain elastomeric

pads or strips wherever practicable.

Design bearing shelves such that bearings can be replaced

without too much trouble.

On major bridges, metal bearings are commonly used, of which the

'pot-type' is the most popular today. This consists of a steel disc

which cups an elastomeric disc. A middle steel plate provides the lid

and a top steel plate provides the sliding medium. Such bearings

should be designed using finite element technique and the

manufacture verified by load tests. Like the elastomeric bearings.

vertical and horizontal load tests should be carried out.

In the past, other steel bearings such as rollers and simple sliding

plates have been used as bearings. Their use has been greatly

reduced in recent years due to the cost of manufacturing each

individuaJ. design and their need for regular maintenance.

7.8 OTHER BRIDGE COMPONENTS

Parapets

Figures 7.5a, 7.5b, and 7.5c show typical bridge parapets.

Parapets should be designed not only to contain errant vehicle,

but also to redirect the vehicle without killing the occupants or

causing accident to either the following or oncoming traffic.

Expansion joint

A typical elastomeric expansion joint is shown on Figure 7.6.

Expansion joints are necessary to prevent impact at the joints.

Such impacts can cause local damage not only to the bridge, but

7 - 14 ID'i'J S/F

[

[

I I

SINGLE RAIL SECTION

F

IE E o o If)

(a) SINGLE RAIL SYSTEM

BRACKET

CAST POST

CONCRETE PLINTH CONNECTED TO BRIDGE DECK

BRIDGE PARAPET TYPES Figure 7.Sa

7 - 15

E e o o ID

E E

8 ..,

BRIDGE PARAPET TYPES

POST--f---

(b) 2-RAIL SYSTEM

7 - 16

2 -RAIL

FRANGIBLE POST

t----CONCRETE PLINTH CONNECTED TO BRIDGE DECK

Figure 7.Sb

\ .'

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FRANGIBLE POST --ii---I~ 3- RAIL

(c) 3 -RAIL SYSTEM

BRIDGE PARAPET TYPES

7 - 17

CONCRETE PLINTH CONNECTED TO BRIDGE DECK

Figure 7.Sc

(J)

~ 2 5 .., 2 ~ 0

~ 2

~ 5 ~ 2

~: 2 5 eX .., 0 uJ- 122 2 UJ UJ a.. ~ a.. ~ UJ UJ (.!) > 0 0 :z 0 (.!)

en :z 2 0 UJ 0 ~ UJ

0 m a: ~ a:

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0 a.. m UJ

C) 2 X u:: uJ--

C) :z en ~

0 U 2 UJ

0 a: ~ a: 0 :E

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SECTION THROUGH TYPICAL ELASTOMERIC EXPANSION JOINT

7 - 18

Figure 7.6

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• I

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---------- ~--~---- ~~-~--

also the vehicle. An elastormeric type of expansion joint is

recommended in general because they are watertight and thus

prevent water and other liquids from reaching the bearing

shelves where corrosion and unsightly stains would otherwise be

caused.

Deck waterproofing

Waterproofing of the bridge deck i.. a worthwhile investment

because even the densest concrete and asphalt are not

watertight. Once moisture penetrates the deck, corrosion of

reinforcing and prestressing steels will inevitably take place.

Maintenance problems associated with steel corrosion in bridge

deck are very serious and any measure to minimise them should

be considered.

Deck surfacing

A layer of wearing course on the bridge deck is recommended.

It is difficult to cast deck concrete to the exact road profile and

the wearing course is useful in achieving the correct profile.

,The wearing course also reduces impact on the bridge and

provides a quieter and smoother surface than concrete.

WIDTH OF CARRIAGEWAY ON BRIDGES

The width of the carriageway over the bridge should not be less than

the width of the carriageway of the approach road.

Where sidewalks are not provided on bridges, a raised verge of

600 mm minimum width should be provided adjacent to parapets as

emergency walkways.

7 - 19 ID738/F

.~.

7.10 RETAINING WALLS

Typical types of refraining walls are shown in Figures 7. 7a and 7. 7b.

Gravity type walls which consist of mass concrete with or without

'plums' can be used where the ground slope is fairly gentle and the

height of retained fill not high. For higher retained fill heights, the

cantilever type of retaining walls, with or without counterforts, is

generally adopted. In steep escarpments, it may be possible to use

anchored walls if sound rock is encountered.

7.11 DRAINAGE CULVERTS

Typical structures for storm water drainage are shown in Figures

7 . Sa to Figure 7. Sm. Essentially, a drainage structure consists of

either a pipe or box culvert under the highway embankment with inlet

and outlet structures.

Reinforced concrete pipe and box culverts shall be designed in

accordance with 'AASHTO Specifications for Highway Bridges, Twelfth

Edition, 1977'. The design loading is that for a 600 KN-Truck (refer

to Figure 7.1 - Proposed Bridge Loadings).

The design of the culvert for any given opening size is governed by

the height of fill above the culvert and the nature of ground

conditions at the culvert location.

Where the iul height varies along the length of a culvert, the details

appropriate to the maximum fill ~eight encountered, shall be used for

the whole length of the culvert, provided that the difference in the

height of fill encountered does not exceed one metre: where this

difference in height exceeds one metre, the culvert must be designed

as a particular case, relating to the prevailing conditions. The

design criteria should also be investigated where the fill height

encountered is less than one half metre or greater than seven metres.

Culverts using tubular steel pipes or fabricated arch segments are

not envisaged for use in the YAR. At the present. time, concrete

culverts constructed in-situ are not only cheaper but are also

logistically more practicable in the more mountainous regions of the

country.

7 - 20 ID73S/F

[

I

I I I I ,I I I I I

TOP OF EXiSTInG CARRIAGEWAY FILL SLOPE ~"'----=:';~~:'::";';'';'';'';'''---et

CARRIAGEWAY CONSTRUCTION

PERMEABLE BACKING u.....---+-( POROUS BLOCKS)

GRANULAR FILL

MASS CONCRETE WITH PLUMS

MASS CONCRETE

(a)

TOP OF EX!ST1Nl FLL SLOPE

SOUND ROCK

GRAVITY RETAINING WALL

CARRIAGEWAY

WEEP PIPES

GROUTED RIPRAP

CARRIAGEWAY CONSTRUCTION

LJ.--I--- PERMEABLE BACKING (POROUS BLOC KS)

GRANULAR FILL

MASS CONCRETE

SOUND ROCK

CANTILEVER RETAINING WALL

GROUTED RIPRAP

(b) CANTILEVER RETAINING WALL

TYPES OF RETAINING WALL Figure 7.7a

7 - 21

TOP OF EXISTING CARRIAGEWAY ----*-------------------~ FILL SLOPE

~-t--PERMEABLE BACKING (POROUS BLOCKS)

GRANULAR FILL ANCHORED WALL

GROUTED RIPRAP

MASS CONCRETE

(c) ANCHORED RETAINING WALL

TYPES OF RETAINING WALL

7 - 22

Figure 7.7b

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." rE" t: ., (I)

...... en OJ

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(LENGTH ALONG ~_ CULVERT) r "l l ", T "1 "I EMBANKMENT SLOPE

I~I 2

! LONGITUDINAL FAll

I I

I·--·~·--·I·

PRECAST A'" -" •• _ .. ..-- w __ ... - I "'lET I CHANHElIlEDWITH SEGMENT S SCOUR PROTECTION AS 1-·1 PIPE CULVERT • _ DETAIL. DIRECTED BY ENGINEER

(SIMILAR TO INLET)

SECTION A - A

Lo: LI'+2LI

(OVERALL CULVERT LENGTH)

. / SKEW I

ANGLF/ l-e-,'

EMBANKMENT TOE LINE

D J:L. 600 1400 750 1400 900 2000 1050 2000

~~ T I R.C.CONCRETE ~ ..-/RETAINING WALL

••••

Hf ,

NOTES: D : INTERNAL DIAMETER OF CULVERT

/ /

LI : LENGTH OF INLET AND OUTLET OF CULVERT H f: HEIGHT OF FILL

. £. CULVERT jA

R.C. CONCRETE CUT OFF WALL

SETTING OUT POINT

TYPICAL PIPE CULVERT - GENERAL ARRANGEMENT

." .

.. ' . "

o

TY~CALCROSSSEcnON

I

....

..., ~

JZ -a m o c !< m ~ c m ~ -Iii

..., {ij" c ... CD ~

en r:r

-

f d

.f-d

~ ~a

/(FOR UNIFORM SOIL

00 FOllNDATION)

~ t~

BEDDING DETAILS

"-(FOR ROCKS OR MIXED SOIL FOUNDATION)

NORMAL BACKFILL IN ACCORDANCE WITH GENERAL SPECIFICATION .

.., (SOOmin) , < < , ',r4:

L .Jo(..;,)" T{0"""" :,:"f:-UNDISTURBED EXCAVATION , Q , , , ,

~", ",' ... ~ " ,', " ' " , ,

I. 2110 ,I (mall.)

MAX. TRENCH WIDTH

,...

NOTES -

I. All dimensions are in miUimetres.

2. TRENCH WIDTH. The dimensions shownon this drow~ must be strictly adhered to. To avoid accidental slips, the trench should preferible be constructed using trench sheeting. the sheating being withdrawn p'!"ooressively as tha work advances, before the backfill is placed. Any soft area or local hard spot in the trench bottom Should be dug out and the bottom leval restorad with wen tamped granular material.

3. BEDDING.

a- Setected free draining, compactabte granular moteriat such as gravet or broken stona of approllimately IOmm. sile, wall tamped under and alongside the pipe.

b- Uniform compoctable material free from tr.. roofs, vegetable motter, clay lumps etc. well tamped by hand In 75 - 150mm. layar ••

c- Uniform compactable material as 'b' but lighlly tamped by hand.

4. LAYING a JOINTING •

During jointing, the pipe shall be supported on its point of balance just clear of the trench bottom. Aftar jointing, the pipe shall be lowered on to bed and the Ii fting sling removed. If is important that the oIpe is supported evenly along its whole length. Under no circumstance Should bricks or other pocking mat.rial be placed under the pipe to adjust its level.

DIRECTION OF FLOW 1

I

..... I

PIPE JOINT

PIPE CULVERTS - BEDDING AND JONTING DETAILS

- ...... JIIIlIIIIIIIIII

.....

N 1.11

"~)

:g ." m o c: !< m ~ c m ; ~

-n _. CQ c: a; ...... o

en o

'~~I ,~ ~H1 'M (

b (FOR UNIFORM

NOTES-

I. All dimensioM ore in milimetres.

2. TRENCH WIDTH. The ditnensioM shown on this drawing must be .frlctly adhered to. To avoid occidental slips the trlOCh should preferably be lined up with trench sheetino, the !heeting being withdrawn pra9ressively os the work aavances before the backfill IS placed. flIIy soft orad or Iocol hard ~ in Ihe tXlftom should be dug out and the bottom level restored with well tamped gronular material.

3. BEDDING.

0- Selecled free draining compactable gra,.,lor moterlal such os gravel or broken stone of approximately 1Onvn. size, well tamped under and alongside the pipe.

• SOIL

-,-_~~. !;;?,TOO) _l¥&:lIIJ::QL.;~:DCIDIU~~ ~~~.~_ \

b- Uniform compactable malerial free from tree rooll. vegetable molter, cby lumps. etc., well tamped br hand in 75 - l50mm. byers.

c- Uniform compoctable moterial as "bO but lightly tamped

by hondo

4. LAYING 6 JOINTING.

T Hf

1"

U D-2T

-2-

300

BEDDING DETAilS

I I I I • TRENCH WIDlli ~(D.2T). 3OO(n-I)+(D-2T) •

(n= No. of pipes)

(FOR ROCKS OR MIXED SOIL

2 FOUNDATION)

i.' )RMAL BACKFILL IN ACCORDANCE WITH GENERAL SPECIFICATION.

During jointing the p~ shall be supported (Jl its point of balance just clear of lhe Irench botlom. After jointing, the pipe snail be lowered on to bed on~ Ihe lift ing 51 Ing removed. It is imporlanl tnat tne PIpe is supported evenly along ils whole lenglh. LInder ro circumc;toncl!') should bricks or otner materials tle placed under the pipe to adjust its level.

.. _ UNDISTURBED EXCAVATION DIRECTION

~~ OF FLOW'"

...

PIPE JOINT

MULTI-PIPE CULVERTS. BEDDING AND JOINTING DETAILS

'-I

N 0\

-0 --0 m o ~ m ~ ~ ~. -r en

:!! co c ., CD -... ex, a.

Tw

11

3&>

PLAN

SECTION A - A

DIA. PIPE (0)

CHANNEL BED WITH SCOUR PROTECTION AS DIRECTED BY ENGINEER I ~

Ll Lc (INLET LENGTH) (CULVERT LENGTH)

kr. . IJ _I' i" ±- i.::::·/j III! '·1=:±--l

1150 -L-

200 .1

SECTION B - B

1 (0 150 ,r,:

·WO ~:::~:.::'" • .. . tF·· .. ;·:-.. ·····~··· ==f ~ ';~.: 175 BLINDING :~. .. ..... :!.~::3l.?5 BLINDING

f75 BLINDING

SECTION C - C ( CUT OFF WALL TO BE

CONSTRUCTED IN TRENCH.)

T

SECTION D - D

NOTES- ALL DIMENSIONS ARE IN MILLIMETRES.

FOR VALUES Of"Tw ,Aw ,Ww ,HH ,Ls ,AD ,Wo,D ANO c>< SEE TABLE A FIGURE 7.BI

CULVERT INl - DETAILS - SKEW e- = 0° TO 45°, GEl 'HAL ARRANGEMENT. ! I .... ,'" I j ' ;', t

.",_ ... , ,- ""'- - - - - ~ ~~~~~"II ~ """" ~

.....

N .....

,> 1

:g "'0 m o c !< m ~ c m ~ lii

:!! CQ C '"" CD ...... Co CD

-·1

~

l.p

:J t-Tw

-----'-------\-''------,

PLAN

'>.. :1:/ )==-I ! \-==-\ ':::i:0 _______ _ L _____ _

LI Lc (INLET lENGTH) (CULVERT LENGTH)

20~ f1 " ,=---1

TT CHANNEL BED I I D H III' Jl H s~tl tiC I!~ ENGINEER, . I ,,,,,.---=:;=:=-

~

, 150 '-lJ ,

I. AD I~ ~ 1100 h 350 -, -,

SECTION B - B

200

11 ~O f ~~Y' ..... ,.;-.. , I

750 :','

L;} 75 BLINDING

SECTION C - C (CUT OfF WALL TO BE OONSTRUCTED IN TRENCH)

1~ Ii::.

VARIES JOINT

~~ h2lX:id::~ SECTION D - D

NOTES - - ALL DIMENSIONS ARE IN MILLIMETRES

ELEVATION A - A - FOR VALUES OF Tw ,Nw,Aw ,LS ,AD ,HH. T AND D SEE TABLE B FIGURE 7.8f.

CULVERT INLET DETAILS TWIN SIMILAR DlA. PIPE CULVERT SKEW e == O~ 15~ 3(f, 45?GENERAL ARRANGEMENT

TABLE A. PIPE CULVERT INLET DETAILS FOR SINGLE PIPE

INTERNAL DIAMETER OF PIPE (D) VARIABLE DIMENSIONS

600 750 900 1050 1200

WJOTH OF TRENCH (T w) 1400 1400 1700 1700 2000

WIDTH OF HEADWALL (H w ) 1100 1100 1400 1400 1600

WIDTH OF APRON (A w ) 2200 2200 2500 2500 2900

WIDTH OF WINGWALL (W w) 750 750 1000 1000 1000

HEIGHT OF HEADWALL (HH ) 1100 1100 1400 1400 1675

LEN.GTH OF SIDE (Ls ) 1100 1100 1675 1675 2294

DEPTH OF APRON (AD) 1200 1200 1800 1800 2400

DEPTH OF CUT- OFF WALL (Wo) 500 500 750 750 750

ANGLE OF SIDE- WALL (0<) 25° 25° 17° 17° Ira

TABLE B. PIPE CULVERT INLET DETAILS FOR TWIN PIPES

INTERNAL DIAMETER OF PIPE (D) VARIABLE DIMENSIONS

900 1050 1200

WIDTH OF TRENCH (Tw) 3200 3550 3950

WIDTH OF HEADWALL (Hw) 2900 3250 3550

WIDTH OF APRON (Aw) 4000 4350 4850

LENGTH OF SIDE (Ls ) 1675 1675 2100

DEPTH 6F APRON (AD) 1800 1800 2400

HEIGI~T OF HEADWALL (HH ) 1400 1400 1675

THICKNESS OF PIPE (T) 150 175 175

PIPE CULVERT DETAILS . Figure 7.8f

7 - 28

1

I

, .I

t l

I '1

1

I I ]

I ]

,]

J ]

] ..

I I J ]

I

.....

N \0

~-

::g "tJ m o c:: !< m ~ c m ~ li)

::!1 CO C .., CD ...... en

CO

nl_ .- .. - IIIIl .~ >l$1

-:1

WIDTH OF APRON

PLAN

.. W~iJlf1

I I

6" '~;51 I I I 1 __________ 1 ___ 1

SECTION A- A

INTERNAL VARIABLE DIMENSIONS DIAMETER OF PIPE (D) G L T

600 500 (1100 NP\ 100

. .. _!50 __ ,-5~0 (1300 NP-50) 125 WHERE NP IS NUMBER OF PIPES.

".,1 ,1 , .... [ --) , _ •. 1

I

CHAftIIEL BED WITH SCOOR PROTECTION AS DIRECTED BY ENGINEER"

W~~

~~--1T f ---r 1100

r=-~~:=::-l1 ~ 1 202\-J. --I ~ I.;;TT

--I ,.200

500 ,;;;.-" .",<:~ '. T-~' i _;{ T-75 BLINDING

±I~

175 BLINDING

SECTlONC-C (CUT -OFF TO BE CONSTRUCTED IN TRENCH)

1200

SECTlONB-B

-\ rOO T-·

:"f \ARIES '-' 10011100 CHAMFER

~_~;, I ".'!'.-.~ .~ ... "i.~'!i-' --1..

t;"~ f75

SECTION 0-0

NOTE- ALL DIMENSIONS ARE IN MILLIMETRES.

CULVERT INLET DETAILS FOR 600 AND 750 DIA. MULTI-PIPE CULVERTS. GENERAL ARRANGEMENT

.....

w o

m o )(

o c ~ m ~ c m ~ t;

!! CQ C

'"' CD ..... ex, ::r

'~-"¥h,", ~

LI LC Lr

Headwall details

(Length alori <i culvert)

Ernlxlr* ment slope

Eirb<J*ment slope- Hf

.....• -~.;.- .-~-~"-.--'-;.-;-;-:-;.--.: .~ ... '!: -:-::_.' J

Chamel bed with SCQI'

o protection as directed L th ~ be . .. . o by engineer I eng VI culvert tween expaIlSIOIl JOInts to Length of culvert between expansion joints to

1 be not more thon 12metres be not more than I metres

t--

"

I L1= 2P I oos-&

SeHing out point

75 Blildrv;! Concrete

Outlet [)etai Is (similar to inlet)

l.oogitulinal fall Detail X . -- ~ .... '

I Box Culvert

SECTION A - A

':.t.

75 Blinding Concrete

~Iet Details

2.0 Oil Dowell bars at 600el; debonded on one side only.

240 EKponsion Serviseal or similar approved waterstop (on all surfaces

. 11 con tad with soil)

Copwith compressible filer on debonded ~12 Servieised I<ork-Pak or similar approved

RC-Concrete retainiAg wall side

R.C.Concrete cut off wall Servicised Kork-Pak or similar approved

::=*::::«.::::z::£: _______ ::::-:::::."::::.::.:III. II ~ reinfon:ed ~~?JA DETAIL X FLOW (EXPANSION JOINT DETAIU

t ~~ Hf

rna'.' '.' . I , B

".. .\ ' .

ElCpansion joint

TYPICAL CROSS SECTION NOTE: ALL DIMENSIONS ARE IN MILLIMETRES UNLESS OTHERWISE SHOWN

TYPICAL R.C. BOX CULVERT - GENERAL l\RRANGEMENT ." - - ,.... .......

.......",., , -~~'" l""'Ij',.y-'it'I'i''ti \1~' .. 1·~_'!':l'III'~"

.....

w -

~

OJ o >< o c: !;: rn =I c rn ~ ~

!! (Q c a ..... . en

I-HF

TS

o

TS

JII;~ ',(1/ '~I ')

I~"HP" W TW ·1

"I " 8 TW . -I I-f··';J:··:· .. ,,>·:/'::··:·:···.." : .. , .... ' ~"il =1' . ~ ........ ' .: 0'25B ::.:.; 0·258 .::. 1i ._ H

, , .' ... . .

:'"

~ ..

,;_ ..

····,1 "",: ..

': .. . '," ".;

. :. . ~' .. ."

11

. :~':-.'.; :'.: : ~ CONSTRUCTION JOINT

. " L :.:' 50mm.

; "':::,' '~~'.~-;~.~' ~ :" .. ~';':'::'. T

ONE CELL BOX CULVERT (TH = O.5TS)

"FI T+'I:"'-'~""" "I :~w

o

T,

' . . .

.: ,' ..... ~;-: :.

ONE CELL BOX CULVERT (TH = 0)

i ') I

H 1·~--"v.P,"~.'. W "I FI ~ 1, ~

TS

o

TS

"I W I- 8 "I WI- 8 "I W ,-

...... ::. ::.' .' ........... , .•.•••• < •••••• , : • ' ••••• '., .• : .•••• '. • ........ =i ··'r·":;:'~;;ifj'''r~'t: T

, t ~.' •• : :~:.J'~! H : ',:. r:.:

.... ::: .

"

't! :.'/' .' ~ . ~:' :'

.,: . «;: ~:.'.":, ~. '.'

.... :'

'.' 50mm. 1<· !NSTRUCTION JOINT

·~···:'~:,:··;:.::.}~::F0::~.:·; .. T

TWO CELL BOX CULVERT (TH O.5TS)

HFI .rf B "ITf B ..ff ---~-.-."

., ,.....;.........+--+ ..........

TS Tsl -D

r.\ . " ' .. ~., .. _ ....... '" ~ TWO CELL BOX CULVERT (TH "" 0)

NOTE: TW ,T S ,TH ,VARY FOR DIFFERENT HEIGHTS OF FILL ABOVE CULVERT.

~w

....... I-----i

.' :" :.

o ...• : ...

B TW

. :: .... .. ., .

. ..

w

B TW

.... ...•. . •.. -,

B ·1

. . ,'"

.' CONSTRUCTION JOINT

:1-. -: '.: .' .... . ....... ' ." .: .'. .... T 50mm

. TS'T-_ ....,;...---.;___.,---.;:.......,.,;. ..;... ..:,; .. ;....;: ... -....;.;.;" ._--.;..:.....:...... ..• _ . ..;...,.;.. ........ .:.:,. .......... > .......... ,_.: ...:.--->.._-..;......:.;..:...;..., /-. ..;,.' ... ..,.;. ' ..... ';..,.;.:' ',;...-_< • ...:.. ..• '---',..J

BOX CULVERT - THREE OR MORE CELLS

~~~~~

HF PIT B ·rr B ·if B '11 T~~·-r·'~··~·=,~·~·~·~~=-~~~·~~~:·; .. ·= .. 4==·=·~·~·(,:~·.~,·~· .. ~~·~~·I·~~:~~~·-~.~,;·~\ :::Ll ~ ;.LL- -r-~'. 'L -,....D;

o TS

. l ~~~

T5 T5

TS TS

TS .. TS TS .,

TS TS T5

Ts~- ~.~"--".....,..........,.......,.-':.:.:.. '.':":>.2'-.. ::::::. ::::::. '.='=."=:' .~<.~i...:~;t;; ... ~ ... ~. ~'.::;:" :Z;::'Z".3.'/3:{~~:~r

BOX CULVERT - THREE OR MORE CELLS (TH = 0)

NOTES: TW ITS I TH I VARY FOR OIFFERENT HEIGHTS OF FILL ABOVE CULVERT.

BOX CULVERT DETAILS

7 - 32

Figure 7.8j

I I t

t

I I J

I 1 J ]

J I I J J ,

·1

.....

w w

'iIIII1

OJ o >< o c: ~ m ~ c m

~ In

." _. (Q c ... CD -... en ';1\

~ ''''1 '-: -1 ~ "''''''i 4

..Ji.-"Ie COSe -I

-:J I I

200Ll115~ r-

300

DETAIL 1

11-1\=-400

DETAIL 2 ~/lkrPANSKlN JOINT DETAIL DRAWN FOR 15° SKEW

300 20

NEL BED WITH SCOUR

~~~~ECTION AS DIRECTED I' ./ _~ t - .? 10 ~ENGINEER I ./'" _--I /"'_ A .l 600 I . __ -

!:!..J' /_ . f ;"... .,.- •• ...... '~ ••.• I .. , ...... ~ ... ,.t : •• _

~MBANKMENT SLOPE

EXPANSION JOINT TO BE PROVIDE C IF WI":;:;! 12000

~ ~ :J ~ ~o t: ("""""" ee e , W. ~R~f'RTOFHm:A't'lNOt:,"LS I I !I ~ I I IJ ' ~. (40'4OQlToo""" WI - cos 9 I

•

PLAN (DRAWN FOR 9:0)

D

SECTION A-A NOTE ALL DIMENSIONS ARE IN MILLIMETRES

0= depth of bOlt culvert

T= thickness of side wall

SECTION 8-8

A [

-1····;·,,···-··, ' ..... ,. ::,(,:' ~:.~~.:t",.~:: ~·~~rf~~ ~.~~~ 1000 f,'.;, T

- .~;:~:

SECTION C-C

NOTE; CUT OFF WALL TO BE CONSTRUCTED IN TRENCH

0 4000

H 3000 2500 2000

I I 1500 1000

I t::~J f/) w 0: :!

150 T

SECTION D-D

CULVERT INLET DETAILS ONE CELL BOX CULVERT SKEWe- = OOto 15°GENERAL ARRANGEMENT

T 350 275 225 200 200 200

......

w ~

m o x o c ~ m =t c m ~ rCJ)

-r1 cO' e OJ ...... 2!

.......... '-- L-

c=v r

JL cose

:J

~ EXPANSION JOINT TO B

PROVIDED IF WI ;0.1200 :1

BENCHING IN STRUCTURAL CONCRETE

300

it5

2ooL_ ,-300

DETAIL 1 DRAWN FOR 15° SKEW

20

o

1J~200 :~~

DETAIL 2

FOR DETAILS OF EXPANSION JOINT SEE CULVERT HEADWALL DETAILS

'J ;J ~ " g. -:001-----'-

. _ _ W, ' ...... (40-4OOIT .. 30' : J ----------------------------------------------------------------l~--~'

0 T 4000 350 PLAN SECTION B-B

_ -...:1'= .... ---- --

:1 .1 D

.. ' '.(.~-::~~

SECTION A-A NOTE: ALL DIMENSIONS ARE IN MILLIMETRES

D: depth of box culvert

T:: thickness of side waH

::.1 ~.'. ": ':.: ':-.. : .

300

11 150

~ . .~:.. . ':-. . . .'

1000 'V r,;., 75 BUNDING

SECTION C-C (CUT OFF WALL TO BE CONSTRUCTED IN TRENCH)

f3 ii ~

3000 275 2500 225 2000 200 1500 200 r1 ....

'::~.:.;: 1000 200 , ...... ~. ':'.

ONSTRUCTION JOINT 100xi00 CHAMFER

150

.' :: ::~:}::.~.::~:.~:-: .

I. VARIES .,

SECTION D-D

CULVERT INLET DET '.S MULTI - CELL BOX CULVERT SKEV B- = 0°10 15° GENERAL ARRANGEMENT I '.,- .... ~,(¥ ,

__ '--L.-~:......-o......-_------.....-- -

·\

....

w VI

I-I

CD a x 0 c: !< m ~ 0 m

~ r-en

." cS" c .., CD ...... ix» 3

-I ,-1 ...J.. -.j "''''I ,.~ol.<""

.JL cos -&

EXR\NSION JOINT DETAIL

( , ( -c'l I

'1 2D "Ii '1-

CHANNEL BED WITH SCOURI/ /' /" A ,PROTECTION AS DIRECTED /' H---

,/

~MBANKMENT /' 2 SLOPE

-~KMENT DETAIL FOR SLOPE <1:2

~BY ENGIN~ ME' I /",~~..-"- --- 0 ~O •. ~---

~ . ~. ~ II \ II 1000 :: ..,., ..... w:J ~ ""''''_, L "'OR DETAILS OF EXPANSION JOINT W, : cos~t (20 -200) TAN 600 SEE CULVERT HEADWALL DETAILS

.., ....

1000

PLAN EXPANSION JOINT TO BE PROVIDED IF W,~1200G

H - - - - - - - ---II -r-- I

,; ," ::: .: ~.

. ~ ", ,'. . ...... - .:. ~ .:.: .

o

i-- -' '--

SECTION A-A

NOTE: ALL DIMENSIONS ARE IN MILLIMETRES D = depth of box culvert T = thickness of side wall

._ ••• 11. •••• ':

I t~1

D T 4000 350 SECTION B-B

CONTRACTION 300 /JOINT

i1 I

[ ill", '. '," ,,',;' . .1."

1000 .. ~

_:~: 75 BLINDING

SECTION C-C

(I) w 0: ~

150 T

NOTE: CUT OFF WALL TO BE CONSTRUCTED IN TRENCH

3000 275 2500 225 2000 200 1500 200 1000 200

'I/CONSTRUCTION JOINT .... ,Y /100 x 100 CHAMFER

150

I. VARIES .1

SECTION D-D

CULVERT INLET DETAILS ONE CELL BOX CULVERT AND MULTI - CELL BOX CULVERT e = 300 to 45°GENERAL ARRANGEMENT

--:- ..... ~---.~ .. ~ -~-.t"':"-"""-·Y·""-··-" .... -t"-.: ... ... ,;:" ~ .~ .j:- .. .;.~ -: .. '

"'<'

. ~:.' ' ........ ,~ ~)~;;1:~<~:-~ --

. ~~~~ ~ .... ~.- '. ~.

, .-{ ... ~.::: , -

, ':" ~-~<.:y:~.-::..~~

,..:,.! •...

r

.-

• • .-

.-

SECTION 8: GEOTECHNICAL CONSIDERATIONS

8.1 GENERAL

Consideration of the likely geotechnical conditions to be encountered

is essential for the design of highways and individual solutions may

be necessary for the countrywide variations that may occur. The

following sections therefore provide brief discussions on some of the

main protlems likely to be encountered and give general

recommendations.

It is most critical that a continual review of aJJ aspects of geotechnical

design is carried out during construction. Frequently unexpected

ground conditions are encountered and carefuJJy considered design

methods are necessary to overcome them.

8.~ SITE INVESTIGATION

8.2.1 Structures

As part of the design requirement for all structures it is necessary to

determine the sub-soil conditions. This is usually accomplished by

the sinking of holes or pits to determine the nature of the ground

and to extract samples for testing. The type of sampling method

selected will vary depending on the type of structure and nature of

the ground.

Boreholes and pits should be spaced to provide a comprehensive

record of all variations in ground types. Testing should be carried

out to determine the strength of aU soil and rock materials within

the zone of influence of the structure in question. The results

should provide comprehensive recommendations on founding depths •

bealing capacity and where appropriate ground loadings .

8.2.2 Pavements

Sampling of sub-grade materials should be carried out along all

proposed highways as part of the collection of design information.

Samples should be coJJected at regular intervals (generally not

exceeding 1 km) but sufficient to sample all variations in ground type

8 - 1 ID738/G

and all areas of problematic conditions. All samples shouJd have

standard grading compaction and classification tests carried out on

them to define fully the expected road sub-grade conditions.

8.2.3 Materials

The location of quarries, borrow pits and sources of construction

material should be clearly identified at the design stage of every

project. Sources of fine and coarse aggregate shouJd be fu]]y

investigated to determine size distribution, durability and strength.

The location of sources should be selected to take into account the

length and difficulty of haul routes.

Tables 8. 1 and 8.2 list the layout and depth requirements of

boreholes for different conditions.

TABLE 8.1: REQUIREMENTS FOR BORING LAYOUT

Areas for Investigation

Development of site on soft compressible strata

Large structure with separate closely spaced footings

Isolated rigid foundation, less than 250 m2 in area

Slope stability, deep cuts, high embankments

8 - 2

Boring Layout

Space borings 30 to 40 m at possible footing locations. Add intermediate borings when sites are determined.

Space borings approximately 15 m in both directions, including borings at possible walls and footings, and establish geologic sections at the most useful orientations.

Minimum of two sample borings at opposite ~orners. Add more for erratic conditions.

Provide three to five borings on line in the critical direction to establish a geological section for analysis. The number of geological sections depends on the extent of stability problem. For an active slide, place at least one boring upslope of sliding

. area.

ID738/G

[

I

I I

r

• • • • • •

( • ,

TABLE 8.2: REQUIREMENTS FOR BORING DEPTHS

~reas of Investigation

Isolated rigid foundations

Long wall

Slope stability

Deep cuts

High embankments

Highways

8 - 3

Boring Depth

Extend to depth where vertical stress decreases to 10 per cent of bearing pressure. Generally all borings should extend no less than 10 m below lowest part of foundation unless rock is encountered at shallower depth.

Extend to depth below dredge line between 3/4 and l~ times unbalanced height of wall. Where stratification indicates a possible deep stability problem. selected borings should reach top of hard stratum.

Extend to an elevation below active or potential failure surface and into hard stratum. or to a ·depth for which failure is unlikely because of geometry of cross section.

Extend to depth between 3/4 ~nd 1 times base width of narrow cuts. Where cut is above groundwater in stable materials, depth of 3 m below base may suffice. Where base is below groundwater. determine extent of previous strata below base.

Extend to depth between ~ and one and a quarter times horizontal length of side slope in relatively homogeneous foundation. Where deep or irregular soft strata are encountered, borings should reach hard materials.

Extend auger ~orings to 2 m below top of pavement in cuts, 2 m below existing ground in shallow fills. For high erebankmen~s or deep cuts, follow criteria given above.

ID738/G

8.3 EMBANKMENTS

The design and construction of embankments requires the carefuJ

selection and pJacing of a wide range of materials. These may vary

from rockfiJI to dune sand but should ideally be well graded and

suitable for compaction.

In the construction of embankments a distinction may be made between

two different types of material used, earthfiJl and rockfi11. This

distinction can be based upon either the grading of the materiaJ used

and/or the method used for placement and control.

Earthfill is usually selected from wen-graded soil materiaJ, not

exceeding 60 mm in size. This should be pJaced in layers not

exceeding 300 mm thickness and compacted to at least 90 per cent of

its maximum density. RockfiH consists of sound dense rock up to

300 mm maximum size placed in layers a maximum of 600 mm thick.

Unlike earthfiJJ. the density of rockfiJJ is difficult to determine with

confidence. Therefore when extensive use of rockfil1 is to be made,

triaJ embankments are necessary to determine the optimum conditions.

Similar trial embankments are also required for the use of aJJ

probJematic embankment materials.

Embankments should only be placed on suitably prepared and

compacted ground. In no circumstances should embankments be

pJaced on slopes greater than IH to IV and all slopes steeper than 4H

to IV should be benched before placing of fill.

Stability of all major embankment~ should be carefully checked and no

side slopes should exceed 1. 5H to IV. Designs should· also include

slope protection and drainage measures where appropriate and

especialJy where there is 8 possibility of scouring. On his::h

embankments, over 10 m, benches should also be provided to facilitate

construction of surface water run-off ditches and allow access for

maintenance.

8.4 RETAINING STRUCTURES

In areas of high filJ and where availabJe construction space is limited,

it may be necessary to construct soil retaining structures. These can

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be of reinforced concrete (as described in Section 7). grouted

masonry t or gabions. Typical dimensions for the Jetter two are

shown on Figures 8.1, 8.2 and 8.3.

A11 retaining structures should be checked for stability during design

and particular care should be taken to ensure good founding

conditions. On major lengths of wall (over 20 m) boreholes should be

sunk to Cietermine ground conditions. All walls. unless free draining

(Le.. gabions) should be designed with adequate weep holes to

prevent the build-up of water pressure behind the structure.

8.5 CUTS

8.5.1 General

The construction of highways almost invariably requires the

excavation of a number of cuts. The geometry of these depend on a

number of different variables of which the most important is usually

the nature of the ground conditions. Ideally. 8 complete survey of

the likely conditions- for each major cut t<> deterr!line the ground

type(s) to be encountered should be unCiertaken.

A· detailed assessment of the stability of each cut is seldom practical

at design stage although regular inspection and evaluation of all cuts

during construction is essential. Figure 8.4 provides guidelines on

s]opegeometries which have proved successful on completed works

but should not be taken as indicative of guaranteed stability.

8.5.2 Slope Stability

In some cases it may be necessary to make provisions for slope

stability measures in the design of cuts. One of the principal causes

of slope instability is water and particularly the heavy run-offs that

occur during periods of storm. Care should therefore be taken to

divert water away from excavations to prevent the erosion of cut

faces and the initiation of slides.

8 - 5 ID738/G

G') » ~ o z » z c s: » en o z ::xJ -< ~ r r

.001 en 0\

"l'~ ~~:'l~

!! C,Q c: ... CD (X) . .....

.....

I, 1.00 STEPS 0.50

EXIST"H; ~D

:~ I.Oxl.Ox30or 4.0 . LONG GABIONS

30cm. THICI( BACK FILL <F GRADED CRUSHED STONE I·.:::~ OR GRAVEL (MINIMUM)

HEIGHT VARIES

2 4 ~I 1[7

TYPICAL SECTION THROUGH GABION RETAINING WALL '~, ..... '" < ..... - - -- -- ~;1 ."~:""!\'\'

HEIGHT OF WALL

0.21

0.30 0.60

CONCRETE (New Jersey) BARRIER

.3Om THICK FILL <F GRADED CRUSHED STONE OR GRAVEL

TYPICAL SECTION THROUGH MASONRY RETAINING WALL

CARRIAGEWAY

NOTE- ALL DIMENSIONS ARE IN METRES

~ ....,

{ ?! ,

TYPE 1 A WALL FRONT FACE ON 1:6 BATTER

TYPE 1 WALL Numberd H 8(m) VOlJJv1E M3 per M in length

Courses (m) I·AWalt I·e Walt I-A Wall I·B Walt

I 1.0 1.0 1.0 1.0 1.0 2 2.0 1.5 1.5 2.5 2.5 3 3.0 2.0 2.0 4.5 4.5 4 4.0 2.5 2.5 7.0 7.0 5 5.0 3.0 3.0 10.0 10.0 6 6.0 3.0 3.5 13.0 13.5 7 7.0 3.5 4.0 16.5 17.5

GASION WALLS - SURCHARGED

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MAX. 11/2

EMBANtO.£NT I~ '~

1;

(X)URSE

NUMBER\li[""5;:i!l~~ ~

TYPE 1 - B WALL FRONT FACE STEPPED

GENERAL NOTES-

H

Gabion walls ShaD be CCJ'IStructed to the lines OIld grades as staked or directed by the Engineer.

2 Intermediate wall heights shall be obtained by using 0.5 m. or 0.3m. deep ~bions i1 one of the CIOUrses.

3 Gobions stall be placed so the vertical joints between baskets are staggered on alternate courses unless ctherwise apprCMId by the Engineer.

4 The horizontal joints between ~bion courses shall not be staggered unless authOrized by the Engineer.

5 All dimensions .... In mitres.

Figure 8.2

!f'~~ 0·50 MINIMUM TO ORIGINAL GROUND WHEN FACE OF WALL IS SUBJECT TO SCOUR.

TYPE 2 - A WALL

'::r"~~:-:- FACE ON 1:6 BATTER

i<: CODE A GABIONS (2·0 x 1-0 x 1'0)

COUNTER FORT-

~- -"

~ ---I. 2.0 .\

-, LO

1 2.0

-t 1.0

---1..

SECTION A - A

GABION WALLS - UNSURCHARGED

8 - 8

Number of H

COJRSE NUMBER \~~~

B

TYPE 2 - B WALL

FRONT FACE STEPPED

TYPE 2 WALL B(m~ VOW ME M3 per M in lenqth

Co,·~ (m) 2·AWall 12·BWall 2·A Wall 2'B Wall

I 1.0 1.0 1.0 1.0 1.0 2 2.0 1.0 1.3 2.0 2.3 3 3.0 1.5 1.6 3.5 3.9 '4 4.0 2.0 2.0 5.5 5.9 5 5.0 2.5 2.5 8.0 8.4 6 6.0 2.5 3.0 10.5 II. 4 7 7 -'. 3.0 3.5 13.5 14.9 . .

GENERAL NOTES-Gabion walls shall be constructed to the lines and grades os staked or directed by the Engineer.

2 Intermediate wall heights shOll be obtained by using 0.5 m. or 0.3m deep gabio!,s in one of the lOourses.

3 Gabions shaU be pla:ed so the vertical joints between baskets are staggered on alternate courses unless otherwise approved by the Engineer.

4 The horizontal joints between gabion courses Shall not be staggered unless authorized by the Engineer.

5 AD dimensions are .j,., """Ires.

H

Figure 8.3 -

I

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-1

CASE I EARTH CUT

CUT >7m HIGH

SHOOLDER

e o o ,...

x ~ :i

3·00 BENCH

CASE II CONGLOMERATE

(WITHOUT BLASTING)

SHOULDER

3·00 (IN MOOERATLY FISSURED ROCK) I I!' 00 (FOR llGHLY FISSURED ROCK :-\2 BENCH

CUT>IOm . . CUT> 10m HIGH

HIGH 10 I -=:JI

E 0 0

!2

" x < ~

:r CUTS ~ 10m HIGH

CASE 11\ WEATHERED ROCK

SHOULDER

E 0 0

!2 " x < ~

:i

10 --==1

CUTS < 10m HIGH

SHOULDER

CASE IV SOUND ROCK

SOUND ROCK :: Typically massive unweathered rock block size 0'5 rJ.

WEATHERED ROCK :: Typically slightly to moderately weathered rock, fractured, jOint

spacing greater than 300mm.

CONGLOMERATE :: Typically poorly cemented soil consisting of silt, sand, cobbles and boulders.

EARTH All non cemented low strength soil materials.

DETAILS OF SIDE SLOPES IN CUT Figure 8.4

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Where conditions likely to lead to slope failure are identified, various

methods of slope stabilisation can be used, including:

Wire netting

Rock bolts

Sprayed concrete

Retaining wans {masonry OF' reinforced concrete)

Gabions.

The design of these measures should be optimised to suit the

conditions for each individual site.

8.6 SAND DUNE AREAS

8.6.1 General

All roads in sand dune areas require careful investigation to ensure

that the accumulation of sand is minimiseG and does not provide a

hazard to the road user. It is important that the alignment is

selected after careful consideration of the wind direction. If at an

possible. roads should be elevated on embankments above general

dune crest height and cuts and all features causing wind speed to

drop and sand deposition to occur should be avoided.

In areas of varying wind direction, typically Barchan type dune fields

and where considerable dune movement is occurring, extreme

difficulty can be encountered in construction and maintaining any

type of road.

In dune areas the availability of materials for road construction is

usually severely limited and the need to import material, often for

considerable distances should always be considered.

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8.6.2 Road Alignment

The following considerations should be used to select alignments in

transverse sand dune areas.

If the road is parallel or inclined to dune but perpendicular to

the prevailing wind direction t few problems are usualJy

encountered. The read shouJd be constructed in the interdune

spaces keeping away from the leeward side of any dunes. I: two

transverse sand dunes are located close by. the gently sJoping

windward side of the sand dune, which is fairly well stabilised.

should be selected with balanced cut and fill so as to avoid any

chances of blockage of carriageway by the active fore dune •

If the alignment of the road runs perpendicular to dunes or

parallel to the prevailing wind direction. several sand dunes may

have to be crossed and cutting of dunes and filling of the space

in between two dunes may be necessary to maintain proper

grade. Cuttings or embankments are not likely to be adversely

affected by strong winds and dust storms if their direction is

the same . as that of road alignment. Cuttings are on the

contrary widened sometimes by wind erosion since the velocity of

wind is ir: :,~eased. due to fluming. However. embankments near

cuttings may sometimes be blown away and deep trenches

formed.

If an alignment makes an angle more than five degrees with the

direction of prevailing winds, embankments can be seriousJy

affected. Any fine soil in berms, gets blown from the windward

direction and is accumulated on the other side or even on the

carriageway and thus creates a serious maintenance problem

Experience shows that an alignment requiring cuttings and

fillings of more than three metres should be avoided at all costs.

An alignment involving minimum cuttings and fillings is

considered to be the best one

Another possibility in transversing transverse dunes is

the crests of the dunes rather than cutting dunes.

slopes of one in six need to be provided.

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Stable

ID738/G

In areas of longitudinal sand dune alignment, the following should be

adopted:

8.6.3

Road alignment in the wind direction poses few problems and can

easily follow the line of interdune plain in the case of sand

dunes. However, in the case of several longitudinal sand dunes

being located adjacent to each other, the alignment should be

located on the dune lee slope since this requires minimum cut

and fill

Roads perpendicular to wind direction (or parallel to longitudinal

dunes) or inclined to it, pose serious problems, since the

prevailing wind direction is similar to that of the axes of the

dunes. Cuttings and embankments can be subjected to serious

sand drift and erosion

Valleys or saddles in a chain of longitudinal sand dunes can be

safely utilised for aligning the road. The alignment of the road

will often become circuituous by following the interdune spaces

but will be the best from construction and maintenance points of

view.

Sand Accumulation

The cross-section of the road should be carefully examined to

minimise wherever possible the accumulation of sand. A level road

will receive a thin layer of sand over the leeward side during normal

direction wind conditions. The layer will be thin and will probably

not impede the vehicles even if equipped with high pressure tyres.

When a reversed direction wind occurs, the thin layer of sand will

shift to the other side of the road. This should not, however, be

serious enough to impede the vehicles. A crown to the road will

aggravate the down wind side accumulation. For this reason the

crown must be kept to the absolute minimum. Flat roads are

preferred.

A slight super elevation on the leeward side of the road will keep the

surface of the road free from sand carried by normal direction winds.

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The road will, however, become covered with sand during the time of

a reverse direction wind storm. This construction should generally

be avoided.

Depression of the normally downwind side of the road will immediately

result in an accumulation of sand. The depth of the accumulation will

depend upon the amount of depression. This factor must be taken

into consideration when makin g 'banked' turns. Turns should have

as long a radius as possible without banking.

8.6.4 Construction and Protection

Typical construction, on embankments, is shown on Figure 8.5. Such

construction is suitable in Rreas of stable or Jow mobility dunes. If

dunes are very mobile it is necessary to consider the use of other

forms of sand stabilisation to prevent inundation of the road.

A vailabJe methods are:

SRnd fences

Shrub and tree planting

Sand trenches

Asphalt spraying

Geotextiles.

The method to be used should only be selected after careful study of

its effectiveness nnd the environmental consequences for each

particular site.

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~~ (1)-(

t.J) m ~ a Z

:!! co c ... CD 0) . 01 --~ -

SHLD. CARRIAGEWAY SHLD. 6·OOm.

~"1}~ .....

1 5 01 I 150LJ ,/;for H)4 < 1'5%1 (1·5% < I· 10 (. ~ /" 6 for H(4

3'OOm

""77~-.... ___ -.....

:----:-:-.. -- - "~~O ~ ................. ', ..... , ... ;; .~... O~ I ...... . .. . ... ; ... ~ .. :.,..' . ........ ~ A#'''' .. : ............ :. I .', ," .... , .. :-;-.; .... .

~====J-~=:I=t:;:: GRAVEL BASE OR GEOTEXIIL: .,. .' ,

SURFACE BENCHED TO FORM WINDROWS

050m MIN. SELECTED IMPORTED FILL

REINFORCING LAYER

ROAD CONSTRUCTION

030m(FINISHED THICKNESS)NATURALLY OCCURING GRAVEL SUB-BASE (CBR), 25% COMPACTED IN TWO LAYERS

NOTE:

A MAXIMUM SUPER ELEVATION RATE OF 5% FOR CARRIAGEWAY AND SHOULDERS SHOULD NOT BE EXCEEDED

-- ... --._--- -- ,,,,~~~I ~1lM\II!

TYPICAL ROADWAY SECTION SAND DUNE AREAS

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Yemen Highway Design Standards (1986)

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Transcript of Yemen Highway Design Standards (1986)