Final Detailed Design Report Lower Nzoia Irrigation...

DESIGN AND SUPERVISION OF

WORKS FOR

THE CONSTRUCTION OF

THE LUKUGA BARRAGE

BARRAGE DRAFT DESIGN REPORT

May, 2013

PREPARED BY:Otieno Odongo & Partners

Consulting Engineers

P.O. Box 54021, Nairobi

Tel : +254 020 3870022

Fax : +254 020 3870103

Email:[email protected]

CLIENT

Secretary GeneralCOMESA Secretariat BEN BELLA ROADP.O BOX 30051LUSAKA,, ZAMBIA Tel: 260 1 229725 Fax 260 1 225107

Lukuga Barrage Draft Deisgn Report

TABLE OF CONTENTS

ABBREVIATIONS.............................................................................................................................................4Chapter 1 EXECUTIVE SUMMARY..................................................................................................................5

1.1 Objective..............................................................................................................................................51.2 Recommended Layout..........................................................................................................................51.3 Cost estimate.......................................................................................................................................6

Chapter 2 INTRODUCTION AND DAM SITING............................................................................................7Introduction.........................................................................................................................................................7

2.1 Purpose and objective.........................................................................................................................72.2 Background information......................................................................................................................72.3 Hydrology............................................................................................................................................82.4 Site investigations and field work........................................................................................................8

Geotechnical Conditions at site..........................................................................................................................92.5 Figure 1: geophysical survey point, old barrage location..................................................................92.6 Figure2: curves of interpreted VES, old barrage location................................................................102.7 Table 1: geophysical survey data analysis, old barrage location.....................................................112.8 Figure 3: geophysical survey point,..................................................................................................122.9 Figure4: curves of interpreted VES, away from old barrage location..............................................132.10 Table 2: geophysical survey data analysis, away from old barrage location...................................14

Grouting procedures.........................................................................................................................................152.11 Introduction.......................................................................................................................................152.12 Site location and topography.............................................................................................................16

Chapter 3 BARRAGE SELECTION AND DESIGN CRITERIA..................................................................193.1 General..............................................................................................................................................193.2 Barrage type selection.......................................................................................................................193.3 Classification as per function and use...............................................................................................193.4 Classification as per hydraulic design..............................................................................................203.5 Classification as per material use.....................................................................................................20

Barrage design criteria.....................................................................................................................................213.6 Seismic Dyke......................................................................................................................................213.7 Zoned rockfill Dam............................................................................................................................223.8 Blanketed rock fill dam......................................................................................................................223.9 Precast concrete caisson...................................................................................................................233.10 Concrete Gravity weir with central overflow spillway......................................................................233.11 PROPOSED BARRAGE....................................................................................................................243.12 Bridge................................................................................................................................................24

Hydraulic design................................................................................................................................................253.13 Design against overtopping-Freeboard............................................................................................253.14 Wave height.......................................................................................................................................263.15 Spillway Design.................................................................................................................................283.16 Stilling basin and energy dissipaters.................................................................................................303.17 Design input data..............................................................................................................................303.18 Stilling basin and energy dissipaters.................................................................................................313.19 Sluice gate sizing...............................................................................................................................333.20 Mechanical Facilities Design............................................................................................................343.21 Fish Ladder and Fish ways...............................................................................................................35

BRIDGE DESIGN.............................................................................................................................................363.22 Selection of bridge type.....................................................................................................................363.23 Geotechnical Investigation................................................................................................................393.24 Bridge Superstructure design............................................................................................................393.25 Bridge Substructure design...............................................................................................................40

Chapter 4 STRUCTURAL SYSTEM AND MATERIALS..............................................................................424.1 Structural system...............................................................................................................................434.2 Loadings............................................................................................................................................434.3 Foundations.......................................................................................................................................434.4 Column piers.....................................................................................................................................434.5 Walls..................................................................................................................................................434.6 Fire resistance...................................................................................................................................434.7 Concrete............................................................................................................................................434.8 Reinforcement bars............................................................................................................................43


4.9 Welding consumables........................................................................................................................444.10 Foundation Condition and Seismic loading Considerations.............................................................44

Chapter 5 STRUCTURAL DESIGN CALCULATIONS................................................................................45BARRAGE.........................................................................................................................................................45Forces acting on the Barrage...........................................................................................................................45

5.1 Figure 7: Diagram showing forces acting on the barrage................................................................45Load Combinations for Barrage......................................................................................................................48ACCESS ROAD AND BRIDGE......................................................................................................................49Forces acting on the Bridge..............................................................................................................................49

5.2 Characteristic Loads.........................................................................................................................49Live Loads.......................................................................................................................................................49

Chapter 6 REFERENCES...................................................................................................................................50Chapter 7 annex...................................................................................................................................................51


ABBREVIATIONSA Flow area

a.m.s.l above sea level

a.m.s.l above mean sea level

BS British Standard

C drowned weir formula Constant

DRC Democratic Republic of Congo

Fcu concrete strength grade

Fr Froude Number

fy Yield strength

L length

M metres

OO&P Otieno Odongo & Partners consulting engineers

q Flow rate m3/s

Q Volume of Discharge, m3

S channel slope

USBR United State Bereu of Reclamation

V Velocity, m/s

VES Vertical Electric Sounding


CHAPTER 1 EXECUTIVE SUMMARY The COMESA Secretariat commissioned M/s Otieno Odongo & Partners Consulting Engineers, to

undertake the Engineering design and supervision of the reconstruction of the Lukuga Barage on

Lake Tanganyika.

The Lukuga River originates from Lake Tanganyika and flows into the Congo River, which is the

only outlet for the water flow of Lake Tanganyika.

1.1 Objective

The overall objective of the report is finalize the general layout of the Lukuga barrage project:

selection of the type of barrage, localization and sizing of the spillway, localization and sizing of

stilling basin and sluices, and access bridge.

1.2 Recommended Layout

The finally recommended layout is:

Concrete Gravity dam

Crest elevation; 778m

Normal retention level; 774m

Height above river bed varies with a minimum of 5 m and maximum of 8m.

Type: The planned barrage structure will be a concrete gravity ogee with central overflow

spillway, with sluices to manage silt deposition and also when fitted with gates to allow

discharge of flood flow when in open position and retain water discharge during low flow.

Spillway

Spillway design flood: 5000 years return period.

It is an overflow weir at the centre of the barrage with a crest length of 180m, stilling basin

and energy dissipators.

Bridge

The bridge is 480m long with a two lane deck with column piers at 20m centres. It is

founded at the same level with barrage and friction piles incorporated on the column bases.

The soffit of the beams rest at the crest elevation of 778m a.s.l.


1.3 Cost estimate

Below is a summary extracted from the detailed bill of quantities.

SUMMARY OF THE BILLS OF QUANTITIES

Bill No. Description Amount

($USD.)

1 PRELIMINARIES AND GENERAL 1,763,826.04 2 SETTING OUT 22,844.09

3SITE CLEARANCE AND TOP SOIL STRIPPING 670,661.00

4 RIVER PROTECTION EARTHWORKS 3,138,962.21

5EXCAVATION AND FILLING FOR STRUCTURES 2,288,744.30

6 CONCRETE WORKS 43,340,288.57 7 ROAD FURNITURE 6,312.50

8 GROUTING 499,808.75 9 SITE INVESTIGATION 121,715.00

10 ROADS AND PARKING 378,083.47

11 Dayworks 151,406.25

SUB - TOTAL 52,382,652.18 Contingency = 10% 523,826.52 Variation of Prices 6.5% 3,404,872.39 16% VAT 8,381,224.35

TOTAL PROJECT SUM FOR THE WORKS

64,692,575.44


CHAPTER 2 INTRODUCTION AND DAM SITING

Introduction Lake Tanganyika is situated within the western Great Rift Valley and is confined by mountainious

walls of the rift valley.

The main ports on the lake are kalemie railhead to DRC rail network, Kigoma railhead to Dar es

Salam in Tanzania, Mupulungu railhead for Zambia and Bujumbura port.

2.1 Purpose and objective

The purpose of the Dam/ Barrage studies is to provide a control structure at source of river Lukuga

that will maintain the predetermined water level.

The objective of this study is aimed at preparing a design for the appropriate water control structure

at the beginning of river Lukuga that will regulate and stabilize the lake water levels to desired

levels which will enable the ports to operate at all times.

2.2 Background information

The Lukuga River is the main outlet of water from Lake Tanganyika. It is located on the western

part of the lake with its source at Kalemie in Katanga Region. It flows into River Congo eventually

entering Pacific Ocean.

Lake Tanganyika has catchment area that is riparian to Republic of Tanzania, Republic of Burundi,

Republic of Zambia and Democratic Republic of Congo.

The major rivers from the above catchments feeding into the lake includes; River Ruzizi from Lake

Kivu, River Malagarasi from Tanzania, and River Kalambo from Malawi.

The Lake Tanganyika has a number of ports including kigoma, kalemi, uvira, etc serving the

riparian countries, and the flacuation of the lake levels often adversely affects the operations of

these ports. In order to reduce the adverse impacts of the flacuations of the lake levels it is necessary

that water balance thereon be maintained such that levels fluctuations is limited to a predetermined

minimum that will allow use of the ports at all times. The purpose of the Dam/ barrage studies is to

provide a control structure at mouth of river lukuga that will maintaion the predetermined water

level.

The design looks into geotechnical studies at the proposed control structure location, metrology and

hydrology of the catchment area and lake water balance and levels fluctuations, design of the

control structure options.


2.3 Hydrology

From hydrological report, the required level for Kalemie port for optimal operations of port

shipping was found to be 774.0m a.m.s.l. and the proposed height of the dam above the current

water level of 770m a.m.s.l (from 2011 field study) is 4m. The location of the barrage from the

river source is approximately 1.12km, where the distance to contour 774 is relatively small and up

stream of the railway bridge.

2.4 Site investigations and field work

Extensive geophysical survey was undertaken during February 2011 along Lukuga River with the

main objective of determining the underground lithology within and along the 1200m long stretch

of the river. The geophysical survey carried out 11 No. deep lithology and plotted the river

underground soil and rock conditions. From the review of the 11 number lithology plots two sites

were selected across the river as potential locations of the proposed dam design options. These are

the locations where the firm hard ground is at shallowest depth.

The existing barrier which was constructed in the year 1952 was damaged and vandalized, rendering

it ineffective in controlling the flow.


Geotechnical Conditions at site Location A:

Construction of barrage at the previuosly constructed site through the following locations

2.5 Figure 1: geophysical survey point, old barrage location


VES 14 – 35M 0743292; UTM 9345930, on HEP 04

VES 03 – 35M 0743209; UTM 9345838, on HEP 01

VES 04 – 35M 0743090; UTM 9345554, on HEP 02

VES 09 – 35M 0743073; UTM 9345412, on HEP 03

The curves of the interpreted Vertical Electrical soundings are as follows:

2.6 Figure2: curves of interpreted VES, old barrage location


2.7 Table 1: geophysical survey data analysis, old barrage location


Formation Thickness (m)

True Resistivity (ohm m)

Expected Geological Formation

Curve No. VES 09

LUKUGA RIVER KALEMIE DRC SOUTH OF LUKUGA RIVER

0 – 0.92

0.92 – 3.80

3.80 – 10.07

10.07 – 18.20

Over 18.20

517

57

14

56

6

Sands deposits

Sandstone

Gravels

Gravels

Clayey soil

Curve No. VES 04

LUKUGA RIVER KALEMIE, DRC, SOUTH OF LUKUGA RIVER

0 – 0.37

0.37 – 1.59

1.59 – 15.17

15.17 – 36.84

Over 36.84

1934

184

26

9

20

Sands deposits

Sandstone

Gravels

Clayey soil

Gravels

Curve No. VES 04

LUKUGA RIVER KALEMIE DRC, NORTH OF RIVER AT THE EXISTING BARRAGE

0 – 0.77

0.77 – 2.87

2.87 – 17.40

17.40 – 45.25

45.25 – 56.77

Over 56.77

1577

130

27

9

26569

30

Sands deposits

Sandstone

Gravels

Clayey soil

Quartzite Sill

Gravels

Curve No. VES 14

LUKUGA RIVER KALEMIE DRC, NORTH OF LUKUGA RIVER AT THE EXISTING BARRAGE 124m NE OF VES 03

0 – 0.53

0.53 – 2.30

2.30 – 3.26

3.26 – 38.17

Over 38.17

862

80

8

16

20

Sands deposits

Sandstone

Clay soil

Gravels

Gravels

Location No B:

CONSTRUCTION OF WEIR/BARRAGE DOWNSTREAM OF THE EXISTING BARRAGE FOUNDATION REMNANTS SITE THROUGH THE FOLLOWING LOCATIONS


2.8 Figure 3: geophysical survey point,

VES 14 – 35M 0743292; UTM 9345930, on HEP 04

VES 01 – 35M 0743209; UTM 9345838, on HEP 01

VES 05 – 35M 0743063; UTM 9345658, on HEP 02

VES 09 – 35M 0743073; UTM 9345412, on HEP 03 at 90m downstream

When plotted on Topographic Map forms a straight line with distance across the river being approximately 256m.

The curves of the interpreted Vertical Electrical soundings are as follows:

2.9 Figure4: curves of interpreted VES, away from old barrage location


2.10 Table 2: geophysical survey data analysis, away from old barrage location

OBSERVATION: one of the findings of the geophysical survey was the determination of the

apex of the lukuga river sill which is consistent with positions marked option site A and B, the

ground conditions became better as you move away from the lake.


Formation Thickness (m)

True Resistivity (ohm m)

Expected Geological Formation

Curve No. VES 09:

LUKUGA RIVER KALEMIE DRC SOUTH OF LUKUGA RIVER

0 – 0.92

0.92 – 3.80

3.80 – 10.07

10.07 – 18.20

Over 18.20

517

57

14

56

6

Sands deposits

Sandstone

Gravels

Gravels

Clayey soil

Curve No. VES 05:

LUKUGA RIVER KALEMIE, DRC SOUTH OF LUKUGA RIVER

0 – 0.37

0.37 – 1.59

1.59 – 8.24

8.24 – 31.95

Over 31.95

4360

321

30

9

20

Sands deposits

Sandstone

Gravels

Clayey soil

Gravels

Curve No. VES 1

LUKUGA RIVER KALEMIE, DRC, NORTH OF RIVER 70m downstream of existing barrage

0 – 0.37

0.37 – 1.59

1.59 – 7.02

7.02 – 44.52

44.52 – 48.90

Over 48.90

2320

136

19

9

146

20

Sands deposits

Sandstone

Gravels

Clayey soil

Sandstone

Gravels

Curve No. VES 14

LUKUGA RIVER KALEMIE DRC, NORTH OF LUKUGA RIVER AT THE EXISTING BARRAGE 124m NE OF VES 03

0 – 0.53

0.53 – 2.30

2.30 – 3.26

3.26 – 38.17

Over 38.17

862

80

8

16

20

Sands deposits

Sandstone

Clay soil

Gravels

Gravels

From the measurements interpretation (given in table above) the underground foundation strata

is determined to be that of sandstone is found at depths varying from 1m to 3m, as the first layer

of rock lying above gravel. Gravel extends to lengths not less than 17m.

With reference to BS 8004:1986, table 1, a bearing pressure of 450kn/m2 has been adopted for

the design.

The required foundation treatment consists of cleaning the top sands deposit and part of the top

mudstone up to depth of 3m from original bed level.

Below the excavation curtain and contact grouting to 10m and 6m respectively is applied to

close the area from leakage/seepage.

Grouting procedures

2.11 Introduction

All holes for grouting, shall be drilled at the locations, in the direction, angle, and to the depths

indicated or as directed by the Engineer. A maximum tolerance for deviation in angle and direction

shall be (30) the first series of holes to be drilled and grouted shall be at (5) - foot intervals and

hereinafter are referred to as primary holes. The location of secondary and succeeding series

(intermediate) holes shall be determined by the split spacing method as defined in paragraph SPLIT

SPACING. The number of grout holes shall be increased, progressively, by the split spacing method

as defined in paragraph SPLIT SPACING. The number grout holes shall be increased progressively,

by the split spacing method as deemed necessary by the Engineer until the amount of grout used -

indicates that the foundation is tight. Each hole drilled shall be protected from becoming clogged or-

obstructed by means of a cap or other suitable device on the collar and any hole that becomes

clogged or obstructed due to fault of the contractor before completion of operations shall be cleaned

out in a manner satisfactory to the Engineer or another hole provided by and at the expense of the

Contractor.

Records:

The Engineer will keep records of all grouting operations, such as a log of the grout holes, results of

washing and pressure testing operations, time of each change of grouting operation, pressure, rate of

pumping, amount of cement for each change in water/cement ratio, and other data deemed by him to

be necessary. The Contractor shall furnish all necessary assistance and cooperation to this end.


2.12 Site location and topography

Location of the dam/dyke is within the mouth of the lukuga river for effective control of the

flooding impacts of the river ponding area upstream of the dam and erosion of the sandy river

banks.

The Lake Tanganyika lies between Lat 30 20’ to 8048’ S and Long 2905’ to 31015’. OO&P carried

out topographical survey of the river lukuga mouth and a topo plan produced. The topo plan covered

a stretch of 2km of the river from the source, with 1m contour intervals. The remains of the

damaged barrier were also captured.

The site is generally gentle with elevations varying from 766m a.m.s.l to 774m a.m.s.l.

This Topography allows fitting of a weir of crest height of 5m from riverbed to raise water level to

774m to as proposed on the hydrological study.

From site topography and the required crest elevation of 774m, the following Weir parameters were

noted,

The crest height from river bed is 774 -769 = 5m.

The weir height above river bank is 774 –774 =0m.


Figure 5: barrage location at Kalemie


Figure 6: barrage location at Kalemie (topography)


CHAPTER 3 BARRAGE SELECTION AND DESIGN CRITERIA

3.1 General

Barrage structure is designed to facilitate the control of water flow to river lukuga, to raise the head

of the lake by 4m within Kalemie Port (as per the hydrological report). The water level required for

port is 774m a.m.s.l. a bridge will be running above the barrage for vehicular transport.

Considering the foundation condition where depth of firm materials range from 1 to 3 metres along

the proposed barrage alignment above the lukuga river, the foundation of the weir is proposed to be

at elevation 769-3=766m, (769 is the river bed level) the overall height of the weir is 774-766=8m

on the overflow potion.

3.2 Barrage type selection

The geological conditions on site and geometry of valley dictate that a rigid gravity dam are considered practical. The selection of the dam type options are as follows:

3.3 Classification as per function and use

Storage Barrage

This is the most common type of barrage normally constructed to store excess flood water which

can be utilized later when demand exceeds the flow in river. The Storage dams may be constructed

for various purposes such as irrigation, water supply, hydro-power generation etc. they may be

made of concrete, stone or earth or rock fill etc.


LUKUGA BARRAGE

USE

STORAGE

DIVERSION

DETENTION

HYDRAULIC DESIGN

OVERFLOW

NON OVERFLOW

MATERIALS USED

CONCRETE

MASONRY

EARTHFILL

ROCKFILL

HEIGHT

LARGE

MEDIUM

SMALL

Detention barrage

These types of barrage are mainly constructed to control flood. This type of barrage stores water

temporarily and releases it gradually at a safe rate when the flood recedes. Detention barrage

provides safeguard against possible damage due to flood on the downstream side of it. Sometimes a

detention dam may also be used as storage dam.

Diversion Barrage

The purpose of diversion dam is necessarily different. It is constructed to divert the river water into

canal, conduit etc. For this purpose, mostly a weir or low level dam is constructed across the river to

raise the water level which can be diverted as per the needs. This type of dam may be used for water

supply, irrigation or some other purposes.

3.4 Classification as per hydraulic design

Overflow Barrage/Dam:

An overflow dam is built to allow the overflow of surplus discharge above the top of it. They are

generally built of masonry or concrete and they are gravity type of dam. Usually dams are not

designed as overflow for their entire length. Only few meters of its length is kept as overflow

section

Non-Overflow Barrage/Dam:

In this type of dam, water is not allowed to overtop the dam. The top of the dam is fixed at a higher

elevation than the expected maximum flood level. Since water is not allowed to overtop, it can be

constructed of large variety of materials such as earth, rock fill, masonry, concrete etc.

3.5 Classification as per material use

The dam type options considered are:

Embankment dam which includes;

Seismic dyke

Earth dam

Rock fill dam

Zoned rock fill dam

Concrete dams which include;

Precast concrete caisson

Gravity concrete weir


Barrage design criteriaThese dam/dyke options design concepts have been elaborated on in order to determine their

technical viability.

3.6 Seismic Dyke

This option consists of an embankment constructed in dry and compacted materials in embankment

designed to resist earthquake loading. The embankment is zoned and consists of sand and gravel

shoulder fills separated with silt/clay core and filter.

The area where the embankment is constructed is dewatered dry using constructed upstream and

downstream parallel sets of temporary cofferdams. The embankment is built in sections to allow

reusing the cofferdam materials.

Considering the foundation soils consisting of sandstones and gravel materials the embankment

design considered in this option has the following particulars:-

a) Slope inclinations of 5:1(horizontal: vertical) on the upstream slope and 7:1 on the

downstream slope.

b) The crest of the dam would be 10m wide ( to allow for 2way traffic) and provide for 2.5m

of freeboard above mean lake level.

c) An overexcavation depth of 3m is provided under the embankment crest, and an

overexcavation depth of 5m is provided under embankment toes. An additional

embankment volume computed on basis of average settlement of 6% of the unexcavated

soft soils over the entire width of the embankment.

The main advantage of this option is that the dry construction method allows compaction of the

embankment materials that makes it stable.

The disadvantages:-

Extensive cofferdams are required for temporary dewatering and staging of construction is

complex.

Expensive river diversion works required.

The location does not have suitable material for construction of impermeable core.

A large river diversion channel required

Require a side spillway

All the disadvantages combined makes the option time consuming and expensive to construct.Lukuga Barrage Draft Deisgn Report

3.7 Zoned rockfill Dam

This option consists of an embankment built with rockfills in its outer shells and soil core. This is

constructed in the wet, and this do not allow for compaction of the embankment materials. Rock is

preferred, as compacted rockfills do not have substantial strength losses during earthquake,

compared to uncompacted soil fills.

As for seismic dyke, 3 to 5m loose foundation soils will be excavated and replaced with

embankment material. An additional embankment volume computed on basis of average settlement

of 6% of the unexcavated soft soils over the entire width of the embankment.

Slope inclinations of 5:1(horizontal: vertical) on the upstream slope and 7:1 on the downstream

slope.

The crest of the dam would be 20m wide (to allow for construction of the multiple lift rock dykes)

and provide for 2.5m of freeboard above mean lake level.

Large volumes of rocks, makes it expensive and time comsuming. They require a separate spillway

away from the main dam.They require heavy maintenance cost and constant supervision.They are

more susceptible to be damaged by floods than any other type of dam.

3.8 Blanketed rock fill dam

This is an option that consists of an embankment built in wet and entirely out of rockfills. To

mitigate seepage through the dam, ablanket would need to be placed on the upstream slope.

Conventionally, this is usually an asphalt or concrete pavement. However, construction below sea

level precludes those for this option. The upstream blanket will therefore consist of depositing fine

grained soils on the upstream slope to plug the rock fill.

Alternately, bentonite slurry would be constructed through the dam along its crest to provide a

seepage barier. As for seismic dyke, 3 to 5m loose foundation soils will be excavated and replaced

with embankment material. An additional embankment volume computed on basis of average

settlement of 6% of the unexcavated soft soils over the entire width of the embankment.

Slope inclinations of 5:1(horizontal: vertical) on the upstream slope and 7:1 on the downstream

slope.

The crest of the dam would be 10m wide and provide for 2.5m of freeboard above mean lake level.

Blanket rockfill dam is prone to high permeability hence large seepage quantities are expected. This

option also requires a separate spillwayaway from the main dam.


3.9 Precast concrete caisson

This option utilizes large precast concrete circular caisons to form a dam structure. The concrete

will provide for non corrosive structure, the caisons would be cast onshore and floated into position.

The caisson would be sunk by excavating the soils within and immediately below the caisson. The

remainder of the caisson would be filled with soil. The stability analysis requires that 22m in

diameter and 25m high caisson is required; the width height ratio is kept the same for lower sea

levels. The individual caisons will be tied together using steel sheet pile arcs, and the area between

the arcs filled with lean concrete.

Advantage of this option is that no over excavation of foundation soils would be required. However,

the concept is unique for application as a dam, and the rigidity of the system would not be as

accomodatind (as embankments) to seismic deformations.

3.10 Concrete Gravity weir with central overflow spillway

This option consist of Construction of a concrete gravity overflow weir with central overflow

spillway supported on reinforced concrete base on firm underground formation. Below the concrete

weir a curtain grouting layer is constructed to reduce water loss through seepage.

Advantages:

It is Stronger and more stable than any other type of dam

It can house an overflow spillway to pass excess flood water safely.

It can be built of any height provided suitable foundation is available to bear all the loads coming on

it.

The failure of a gravity dam is not sudden at all. It gives sufficient time for evacuation of area

downstream of it.

Though its Initial cost is higher, and It needs skilled labor and mechanized plants for construction

and It may take more time in construction, its is the most prefered option for Lukuga.

From considerations of technical viability of construction of the above options it was considered

that the concrete gravity dam with central overflow spillway was the suitable dam type for Lukuga

Dam/Dyke. The design therefore adopted this type for futher hydraulic and structural design

analysis.


3.11 PROPOSED BARRAGE

The planned barrage structure will be a concrete gravity ogee with central overflow spillway, with

sluices to manage silt deposition and also when fitted with gates to allow discharge of flood flow

when in open position and retain water discharge during low flow.

The proposed barrage structure is 5m high above the river bed at deepest point and has a crest weir

length of 180m, a non overflow concrete wall of 166 m and 134m on either sides of the 180m

overflow weir and an 480m access concrete bridge deck to allow access to the sluices penstock

gates for the control of sluices gates penstocks facilities and also vehicles connecting the north and

south sides of Kalemie Port.

3.12 Bridge

The bridge is to connect the two towns to the port.

The bridge is a modular bridge 480m long composing of 24No. 20m span centre to centre bearings.

7.0m carriageway with 2 No. 1.9m clear walkways, 50mm thick surfacing.

The beams grillage is composed of 5 No. 1500 deep by 500mm wide main beams simply supported

on free bearings, 2No. 1500mm deep by 300mm wide Diagphrams each on support. The height of

the freeboard is 4m above the barrage crest overflow width.


Hydraulic design

3.13 Design against overtopping-Freeboard

Overtopping waves can constitute a danger to the barrage when they exert lateral loads on the

retaining gravity wall. Wave overtopping must therefore be prevented by giving the dam sufficient

freeboard above the maximum design water level. Freeboard is the vertical distance between the

maximum reservoir water level and the crest of the dam without camber. Free board (Ho) is the sum

of the significant wave height (Hw), wave run-up (Rw) and wind set-up S computed using the

following empirical relationships (based on UK Reservoir Flood Standards).

Zuiderzee formula:

Where:Hw is significant wave height (m), Rw is wave run-up (m) S is wind set-up (m)U is the wind velocity over water (km/hr)F is reservoir fetch (km)L is wave length (m)D is average water depth along the central radial (m)F is reservoir fetch (m)Ho is the freeboard (m) is the angle of upstream face of the dam with horizontalT is the wave period (sec)


DFUS*1400

2

CotL

HwHwRw 5.0

4.0

2*12.5 TL

3.14 Wave height

Waves are generated on the surface of the reservoir by the blowing winds, which exert a pressure on

the downstream side. Wave pressure depends upon wave height which is given by the equation

Molitor's empirical Formula

For F < 32 km, and

for F > 32 km

Where is the height of water from the top of crest to bottom of trough in meters.

V – Wind velocity in km/hour

F – Fetch or straight length of water expanse in km.

Wind velocity overland is 110km/h associated over water is 1.15 times larger; giving 126.5 km/hr

for design wind speed.

variables velocity normal pool 127 km/hrmax reservoir 92 km/hrFetch 2.64 km

norm. pool = 0.58478632 m0.032(FV)^0.5

max reservoir =0.49870744

9 m0.032(FV)^0.5

(VF)^0.5 18.2745725

F^0.251.27467944

2

norm. pool = 1.10258301 m

max reservoir =1.00789625

2 m

9% of waves may exceed the significant wave height hence the corresponding design wave height is;

1.1x1.002348=1.1026m.


Wave run-up Rw (m) and wind set-up, S (m)

Hw 1.10 mF 2.64 kmD 1400 m

90 U 127 km/hr

S is wind set-up (m)

S= 0.021554051 mTp=0.07118*F^0.3*U^0.4

F 2640 mU 35.13888889 m/sg 10 m/s

T= 3.141625198 sTm 2.576132662

L is wave length (m)= 33.97867261 m

Rw is wave run-up (m)

Hw/L= 0.032449267 Tan 572.957213 Cot 0.001745331

Rw= 2.75 m

Total Freeboard= Rw+Hw+S

The freeboard adopted therefore is 4.0 m.


3.15 Spillway Design

Spillways are hydraulic structures designed to release excess water from a reservoir to a stretch

downstream of the dam. This protects the dam from destruction from debris, wave action, and

floods. A spillway is sized to provide the required capacity, usually the entire design flood, at a

specific reservoir elevation. The spillway shall be designed as open earth channel broad crested

weir. Spillway capacity (Q) and Dimensions

Q=23

h∗b √ 23

gh

b= Q

1 . 7∗h3

2

Where;

b is the spillway width (m) h is the design upstream water head above the spillway crest, Q is the design flood

a. Spillway design flood

The proposed return period has been checked from Q1000 and Q5000. The maximum Q is used for

weir sizing. This flood is to be passed by the spillway after routing through the reservoir with full

freeboard allowance on the barrage meaning that with a 127km/hr wind the waves so produced will

not overtop the crest of the barrage.


b. Probable Maximum Flood (PMF)

This flood is to be passed by the spillway after routing through the reservoir with a nominal 0.50m

freeboard on the barrage and the waves produced by 127km/hr wind may be allowed to run on the

wave wall provided on the crest.

PMF METHOD ln(PMF+1)=1.175*(ln(CA+1))^0.755+3.133where PMF, Probable Maximum Flood, m3/sCA, Catchment Area (km2)CA >32 take 200km2

= 7.27367 PMF 1440.83 m3/sdesign floods are calculated has a proportion of the PMF, i.e. Q5000=0.46*PMF and Q1000=0.38*PMF

Q1000 547.516 m3/sQ5000 662.782 m3/sPMF 1440.83 m3/s

c. Spillway width

Q=23

h∗b √ 23

gh

Q=1440.8

3 m³/s

h= 4 mfreeboard max

h^(3/2)= 8

b105.94

3 m

Since the current width of the channel at the proposed site is 180m, a spillway width of 180 m will

be adopted.


3.16 Stilling basin and energy dissipaters

Hydraulic design is of 5m high concrete gravity overflow weir above the river bed supported on

reinforced concrete base founded at the firm ground which is 3m below the river bed level. The

overall height of the barrage from foundation is 8m.

3.17 Design input data

river bed elevation 769 mplanned weir crest level 774 mupstream face slope vertical downstream face slope 0.75:1 design discharge 600 m3/slength of the weir 180 m hydraulic analysis to determine design head discharge Q=CxLxH^2/3 where, Q=600m3/s, L=180m, Cd=2.2 design head, H=(Q/(2.2X180))^2/3 1.31918 mheight crest above riverbed P 5 m

P/Hd=P/He=5/1.32 3.787879

>1.33 therefore velocity of approach effect is negligible

(Hd+P)/He=(1.32+5)/1.32 4.787879 > 1.7 Therefore Cd is not affected by downstream apron and tailwater


3.18 Stilling basin and energy dissipaters

Selection of stilling basin USBR type, where the stilling basin is of the type where water returns to

the river directly and this requires a bucket that dissipates Energy by Impact.

Crest length L=180m

Crest height D= 5m

Discharge Q=600m3/s

Consider rectangular channel

Discharge/m width spillway q= 600/180 = 3.33m3/s

Compute He from, drowned weir formula, q=2/3xCdx(2g)^1/2xHe^3/2

Discharge q=2/3 x C x (2g)^1/2 x He^3/2

C=0.7

He ={3.33/0.7)x 2/3 /2x9.8)^1/2 }^2/3 = 1.37m

Average fall of water = 8+1.37/2 = 8.685m

Theoretical velocity at foot of spillway V1= 2(gH) ^1/2 = (2x9.81 x 8.685) ^1/2 = 13.05m/s

Velocity of approach V1= 0.92x13.05=12.006m/s

Depth of flow at foot of spillway y1= q/V1 = 3.33/12.006 = 0.277m

Froude no Fr= V1/ (gy)^1/2 = 12.006/(9.81x0.277)^1/2 = 7.278

Tail water depth

Fr.=7.3

Tw/y2=1.0

Tw/y1=11

Tw=y1x11=0.277*11=3.047m

Y2=Tw=3.047m

Factor of safety

Twmin /y1=10.5, Twmin =10.5x0.277=2.9085m

FS= (TW-Twmi)/y2=(3.047-2.9085)/3.047

=4.5percent < 5% (recommended minimum margin of safety)

To satisfy minimum margin


Tw=Twmin+ 0.05y2= 2.9085+0.05*3.047=3.061m

Determine the basin length

Length of stilling Basin = 5x (y2-y1) = 5(3.061-0.277) = 16.65m

Length of stilling Basin = 5x (y2-y1) = 5(3.061-0.277) = 16.65m

Adopt 23m including the sill blocks.

Fr=7.3 (> 4.5)

V= 13.05m/s (<15m/s)

Therefore use type II stilling basin USBR with chute Blocks and end sill.

Blocks:-

Height 2y1= 2 x 0.345= 0.69m

Width 2y1= 0.69m

Length 2y1 = 2x 0.345 = 0.69m, use 1m

Spacing between blocks 2.5 w= 2.5 x 0.345=0.86m use 1.0m spacing.

Adopt 1m high, 1m wide, 1m long and 1m spacing.

Dentated End sill

Height 0.20y2= 0.2 x 3.061=0.6122m use 1m.

Width 0.15y2= 0.15 x 3.061=0.459m use 1m.

Spacing 0.15y2= 0.15 x 3.061=0.459m use 1m.


3.19 Sluice gate sizing

Sluice gates have been provided to allow for scouring and environmental flow for river Lukuga.

At the Lukuga River, the flood flows of 402m3/sec. occurs during the month of May while the low

flow of 252m3/sec occurs during the month of October and November. The average flow from

hydrological study is as shown on the graph below;

Jan Feb Mar

Apr

May Jun Jul

yAug

Sept

Oct

Nov

Decem

ber

0

100

200

300

400

Average Monthly Flow of Lukuga River at Sill in M3/sec.

Series1

Month of the year

Aver

age

Mon

thly

Flo

w in

M3/

sec.

The evarage annual flow is 292.333m3/s.

Sluice sizing

INPUT DATAQ 250 m3/s

River Channelwidth 180 mheight 0.5 msluice dia 1.45 m

V=Q/A 2.77778 m/senvironmental flow

1/3Q 83.3333 m3/ssluices total area for environmental flow

A=Q/V 30 m2area for one sluice

1.65046 m2number of sluices

18 The sluice diameter is 1.45m with gates to control flow as appropriate. The gates will be manually operated.


VxAQ

3.20 Mechanical Facilities Design

The design provides for the provision of:-

(a) 18no. cast iron penstock/GMS gates at the gravity dam spillway width

(a) Cast Iron Penstock Gate

The design provides for 18 no. sluice openings at 5m depth to control flow through a 1.45m sluice

fitted in the Low Gravity Concrete Diversion Weir.

The sluice 1.45m diameter provided has a capacity of Q=C x A x (2gH)1/2 ,

Where Q= discharge (m3/s),

A= sluice x section area (m2),

C=coefficient (0.7) ,

H=Crest Head over the sluice H (m).

These sluice will each discharge Q= 4.629m3/s total 83.33m3/s. at water level at spillway crest

elevation.

From reference to Ham and Baker Catalogue, a 1500 x 1800mm penstock gate with half frame

thrust remote rising spindle, having the following particulars:-

(a)Thalf frame with remote spindle rising above water level,

(b) Cast iron door (b) seating faces

(c) Wedges adjustable with wear

(d) Flush invert mounting

(e) Cast iron thrust housing

(h) Standard Invert seal

(i) Phosphor bronze door nuts

(j) Standard fasteners

(k) Opening spindles with extensions.

(l) Operating gears to lift or lower the gate door.


Generally the gates will be left open during the period when river flow spills over the weir, but will

be closed should river flow stop spilling over the weir.

3.21 Fish Ladder and Fish ways

A fish ladder (or stair, fish way, fish pass) is a structure designed to allow fish the opportunity to

migrate upstream and continue their function as part of the river ecosystem. With diverse fish types,

it will need varying properties for the ladders hence may necessitate different types. The most

appropriate pathways will be gated sluices for fish migration.


BRIDGE DESIGNIn the design of Lukuga Bridge we set out to undertake bridge designs to worldwide standards

whose approach entails the following

Selection of bridge type.

o Safety

o Economy

o Aesthetics

Geotechnical investigations and selection of foundation types.

Bridge design.

o Design standards

o Loading

o Methods of analysis

o Analysis Results

o Design of foundations and structural elements.

Construction methodology and maintanance.

3.22 Selection of bridge type.

Safety

In the design of the bridge, we set out to ascertain that ideal structure adopted does not

collapse in use. It must be capable of carrying the loading required of it with the appropriate

factor of safety.

The structure is designed not to suffer from local deterioration/failure, from excessive

deflection or vibration, and it must not interfere with sight lines on roads above or below

it.

To ensure that the above is achieved, strict adherence to recommended codes of practice for

bridge engineering governing loading and design of the various structural elements was ensured.


At the preliminary stage, previous designs carried out worlwide can give a pointer as to the most

adopted bridge decks for various spans.

For bridges Up to 20m the following deck types are adopted

Insitu reinforced concrete.

Insitu prestressed post-tensioned concrete.

Prestressed pre-tensioned inverted T beams with insitu

fill. For bridges from 16m to 30m spans;

Insitu reinforced concrete voided slab.

Insitu prestressed post-tensioned concrete voided slab.

Prestressed pre-tensioned Y and U beams with insitu slab.

Prestressed pre-tensioned box beams with insitu topping.

Prestressed post-tensioned beams with insitu slab.

Steel beams with insitu

slab. For bridges from 30m to 40m;

Prestressed pre-tensioned SY beams with insitu slab.

Prestressed pre-tensioned box beams with insitu topping.

Prestressed post-tensioned beams with insitu slab.

Steel beams with insitu

slab. For bridges from 40m to 250m and

beyond

Box girder bridges

suspension bridges

cable stayed

A 20m spans with expansion joints at every 40m has been adopted hence adopting the insitu

reinforced concrete deck with insitu T Beams.

Indeed Single or multi-cell reinforced concrete box Girder Bridge have been proposed and

widely used as econo m ic a est h e t ic s o l u tion for the over crossings, under crossings, grade

separation structures and viaducts found in modern highway system examples including Nyali

bridge at Mtwapa and the sabaki bridge in malindi.


Economy.

The structure must make minimal demands on labour and capital; it must cost as little as

possible to build and maintain. The bridge being of concrete cast insitu is comparatively

cheaper than any other form of construction.

Appearance.

Bridges being long lasting structural monuments, emphasis, in recent years, has been actually on

the aesthetic appeal of the bridge. Bridges all over the world are fast becoming tourist

attractions with their elegant forms.

the blend of the bridge and the weir provides beautiful scenery to the area surrounding.


3.23 Geotechnical Investigation

It was established two areas that are potential for the construction of barrage with underlying stratum

capable for holding foundations.

Further downstream it was established presence of weak points due to some fractures in the ground

which are believed to have contributed to the River formation and the flow out of the lake. The lake

formation was a result of Greater Rift Valley formation due to faulting phenomenon episodes.

The safe foundation strata varied from 2.3 - 8 m with clayey soil beneath. Friction piles have been

incorporated in the design.

3.24 Bridge Superstructure design

The bridge superstructure design was based on design width, loading and other parameters that were

strictly in conformity with Bridge Design Manual Part IV – Draft October 1991 and as revised in

August 1993. The other guidelines of BS 5400 (Parts 1 [General], 2 [Loads], 4[Concrete],

7[Workmanship], 8[Materials] and 9[Bearings]) have been taken on board. Reference was made to BS

8110 for reinforced concrete design.

Reference has also been made to Y Maekawa’s (Bridges section, Ministry of Roads and Public Works

/ JICA) guidelines on calculations presentation dated December 1985. Design has been carried out for

both permanent and transient loads on the bridge structure.

The following loadings were considered:

Dead loads, self weight, surfacing, fixings etc

Live load surcharge: HA loadings with a check for a minimum of 30 units HB loading.

Braking forces

The effects of seismic activity were checked to be in conformity with the Kenyan

Seismic Design Code as issued by the Building Centre, Ministry of Roads and Public

Works especially for the rift valley belt.


The following loads were considered in addition to the above for the Preliminary design.

Erection loads, wind loads

Effect of any skew

Temperature changes

Friction at bearings

Differential settlement

Skidding or centrifugal forces (if the bridge is on a curve)

Parapet to be able to take some collision loads

Detailed computerized design was carried out by use of Engineering softwares SAP 2000,

bestech sam bridge, oasys gsa bridge.

The details of the structural modeling, the computer analysis for both serviceability and

ultimate limit states and the member design are attached as in the design calculations.

3.25 Bridge Substructure design

The bridge sub-structural design involved the design of piers, abutments and associated foundations.

Pier/abutment heights were determined by the required hydraulic openings and the vertical alignment

at bridge crossings. Design was carried out for all the forces transmitted from the structure onto the

substructure. In addition, horizontal forces from earth pressures and from the braking forces were

considered. Various combinations of these were considered to evaluate the most onerous cases and

appropriate factors of safety provided against bearing pressure, failure and overtopping.

Abutments specified is solid reinforced concrete with transverse diaphragm beams to distribute the

deck structure loading onto them. Wing walls have been designed as free-standing cantilevers but

with continuity bars connecting the wing walls to abutments to eliminate longitudinal movement

between the wing walls and the abutments which is fairly common in purely free standing wing walls

unconnected to abutments.

Piling has been included in the design together with spread footing as currently specified. The pile

arrangements will be bored cast insitu piles. Alternatives may be made at construction stage.

Bridge bearings

Elastomeric bridge bearings were adopted


Expansion Joints

Expansion joints were designed to take into consideration expected movements during serviceability

and ultimate limit states arising from loading, temperature, deck shortening due to creep and

shrinkage and rotation.


CHAPTER 4 STRUCTURAL SYSTEM AND MATERIALS

The structural analysis and design for the proposed barrage, has been based on the Ultimate Limit

State method. Factors of Safety as applied to materials and loadings are as specified in the Standards

and Codes of practice currently in use. The softwwares used included masterseries, prokon and

spreadsheets for analysis and design

The following references have been used in the design:-

B.S 6399: Loading for Buildings

CP3 Chapter V Part 2 1972: Wind Loading

B.S. 8110 Part 1, 2 and 3: Structural Use of Concrete.

B.S. 8007: Design of Concrete Structures for Retaining Aqueous Liquids.

Reinforced Concrete Designer's Handbook: 10th Edition by Reynolds

Structural Use of Timber to B.S. 5268

Eurocode 8 for seismic loads

B.S 8004-Foundations

Road Design Manual Part 1V, Bridge Design, August 1993.

BS 5400 Part 1 General Statement.

BS 5400 Part 2 Specifications for Loads

Department of Transport Highway & Traffic Departmental Standard BD 37/88 loads for

Highway Bridges 1989.

BS 5400 Part 4 Code of Practice for Design of Concrete Bridges.

BS 5896 High Tensile Steel Wire and Strand for Pre-stressed Concrete, 1980

AASHO Standard Specifications for highway Bridges

BS Codes of Practice for foundations


4.1 Structural system

The weir is of ogee type mass concrete with a reinforced concrete base and stilling basin. The gravity

wall has norminal reinforcement for anticrack on the surface of the wall. The barrage base and that of

bridge piers will be founded at the same level, with friction piles on the column bases. All the column

piers will be wall type.

4.2 Loadings

Loading condition is usual which includes normal operating and frequent flood conditions.

Dead load on the structure comprises of own weight of the designed structural elements and applied

finishes.

4.3 Foundations

Due to the interface between the pier bases and barrage base, a raft foundation have been used to spread

the total loading coming from the columns and are optimally sized to be in tune with gravelly type of

soils with Safe Bearing Capacity up to 450Kn/m2.. Additional friction piles have been incorporated on

the pier bases.

4.4 Column piers

Columns are rectangular reinforced concrete walls. The sizes relate to the height so that slenderness is

minimized and will also depend on the anticipated intensity of loading. The columns are designed to

carry the axial loads combined with fraction of framing moments and water floor loads.

6000x800mm Rectangular reinforced concrete columns have been used as structural supports in the

entire bridge.

4.5 Walls

Stilling basin walls are reinforced concrete walls and acts as retaining walls.

4.6 Fire resistance

Minimum cover to reinforcement has been proposed as 50mm.

4.7 Concrete

Concrete class 30 is considered for all substructures and superstructures. The slump is between

75-125mm.

4.8 Reinforcement bars

All rebars used are high strength d bars of 425N/mm2. Provide to full length of pile considering the

possible tensile forces, both loading and construction.


4.9 Welding consumables

All welding consumables, including covered electrodes, wires, filler rods, and flux and shielding gases,

should have be class 42.

4.10 Foundation Condition and Seismic loading Considerations

The area where the barrage is located is considered to be of moderate seismicity and the design has

adopted design peak acceleration of 0.34g vertically and 0.17g horizontally.

Foundation treatment will consist of:-

Exposing and removal of top sand material and loose rocks to depth of 3.0m which will result into

reduction of settlement from loose materials.

Application of drilling and grouting foundation treatment to approximately 10m depth below weir

foundation base to seal lenses between hard rocks which will seal leakages through these seepage

potential seepage paths.

Removal of loose material including sand will reduce potential occurrence of liquefaction in case of

occurrence of seismic activity when the weir structure is built.


CHAPTER 5 STRUCTURAL DESIGN CALCULATIONS

BARRAGE

Forces acting on the Barrage

5.1 Figure 7: Diagram showing forces acting on the barrage

The forces are as listed below;

1. Water pressure

2. Uplift pressure

3. Earthquake

4. Silt pressure

5. Wave pressure

6. Weight of the dam

Water pressure

Water pressure act on the upstream and downstream face of the barrage. The water pressure on the

upstream face is destabilizing (or overturning) force acting on the gravity dam. Tail water helps in

stabilizing. Tailwater is generally small in comparison with water pressure on the upstream face.

The water pressure p, (kn/m2) varies linearly with the depth of the water measured below the free

surface (m).


Uplift pressure

Water has a tendency to seep through the pores and fissures of the foundation material. It also seeps

through the joints between the body of the dam and its foundation at the base, and through the pores of

the material in the body of the dam. The seeping water exerts pressure and was accounted for in the

stability calculations.

The uplift pressure is defined as the upward pressure of water as it flows or seeps through the body of

the dam or its foundation.

A portion of the weight of the dam will be supported on the upward pressure of water; hence net

foundation reaction due to vertical force will reduce. The effective area is taken as approximately equal

to the total area.


Earthquake

The earthquake sets up primary, secondary, Raleigh and love waves in the earth’s crust. The waves

impart accelerations to the foundation under the dam and cause its movement.

The earthquakes cause random motion of ground which can be resolved in any three mutually

perpendicular directions (vertical and horizontal). This motion causes the structure to vibrate.

Peak ground acceleration of 0.32g horizontal and 0.16g vertical have been adopted for analysis. This is

the accelerations with expected increase by 10% in 50years. Hence the design acceleration is 0.34g and

0.17g respectively.

Silt pressure

Gravity dams are subjected to earth pressures on the downstream and upstream faces where the

foundation trench is to be backfilled. Silt is treated as saturated cohessionless soil having full uplift and

whose value of internal friction is not materially changed on account of submergence.

Wave pressure

In addition to the static water loads the upper portion of dam is subjected to the impact of waves. The

force and dimensions of waves depend mainly on the extent and configuration of the water surface, the

velocity of wind and the depth of reservoir water. Empirical formula adopted.


Wave height was used in the determination of freeboard requirements due to wave run up.

Weight of the dam

The weight of the dam is the main stabilizing force in the gravity dam. The dead load to be considered

comprises the weight of the concrete, such appurtenances as piers, gates and bridges.

Load Combinations for Barrage Load combination 1: (normal operating condition) - full reservoir elevation, normal dry weather

tailwater, normal uplift, silt.

Load combination 2: (flood discharge condition) - dam at maximum flood pool elevation, all

gates open, tailwater at flood elevation, normal uplift and silt.

Load combination 3: (construction condition)- dam completed but no water in the reservoir and

no tail water.

Load combination 4: combination 1 with earthquake



All the load combinations have been analysed for different section both at the overflow section and non overflow section.

The requirements of stability satisfied by the design are as follows;

1) Safe against sliding on any plane and combination of planes within the dam, at the foundation

or within the foundation.

2) Safe against overturning at any plane within the dam, at the base, or at any plane belw the base.

3) Safe unit stresses in the concrete of the dam and foundation have not been exceeded.


ACCESS ROAD AND BRIDGE

Forces acting on the Bridge

5.2 Characteristic Loads

The following characteristic Loads based on the aforementioned codes, were considered;

Live Loads

Dead Loads

Wind Loads

Seismic Loads

Dynamic River Current Load

Live Loads

The following traffic loads were considered in the design;

HAU loading

HA KEL Loading

30 Units HB loading

Pedestrian loading

Dead Loads

The following dead loads were considered in the design by the previous consultant namely.

Reinforced or pre-stressed concrete : gc=25KN/m3 Backfill soil : gs=18KN/m3 Asphalt concrete pavement : ga=23KN/m3 Handrail : 1KN/m

Mean hourly wind speed was taken as 30m/s


CHAPTER 6 REFERENCES 1. Request for Proposal for Consultancy Services for the Preparation of Engineering Design and

Supervision of the works for the construction of the Lukuga Barrage by common Markets for

Eastern Africa dated April, 2009

2. B.S 6399: Loading for Buildings

3. CP3 Chapter V Part 2 1972: Wind Loading

4. B.S. 8110 Part 1, 2 and 3: Structural Use of Concrete.

5. B.S. 8007: Design of Concrete Structures for Retaining Aqueous Liquids.

6. Reinforced Concrete Designer's Handbook: 10th Edition by Reynolds

7. Structural Use of Timber to B.S. 5268

8. Eurocode 8 for seismic loads

9. B.S 8004-Foundations

10. Road Design Manual Part 1V, Bridge Design, August 1993.

11. BS 5400 Part 1 General Statement.

12. BS 5400 Part 2 Specifications for Loads

13. Department of Transport Highway & Traffic Departmental Standard BD 37/88 loads for

14. Highway Bridges 1989.

15. BS 5400 Part 4 Code of Practice for Design of Concrete Bridges.

16. BS 5896 High Tensile Steel Wire and Strand for Pre-stressed Concrete, 1980

17. AASHO Standard Specifications for highway

18. Ham and Baker Catalogue-Sluice gates, slide gates and penstock.

19. Seismic Hazards in the DRC CONGO and Western Rift Valley of Africa- By T Mavonga and R

J Durrheim.

20. Engineering Manual-Gravity Dam Design- By US Army Corps of Engineers

21. Y Maekawa’s (Bridges section, Ministry of Roads and Public Works / JICA) guidelines on

calculations presentation dated December 1985


CHAPTER 7 ANNEX A-1: barrage and bridge Drawings

A-2: barrage structural calculations


Final Detailed Design Report Lower Nzoia Irrigation...

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