Use of Fly Ash for Road and Embankment Construction CRRI Sudhir Mathur

Use of Fly Ash for Road Use of Fly Ash for Road & Embankment & Embankment

Construction Construction

Presentation by

Sudhir MathurHead

Geotechnical Engineering DivisionCentral Road Research Institute, New Delhi

Major Road Construction Major Road Construction ProgrammesProgrammes

• National Highway Development Programme (NHDP)

• Pradhan Mantri Gram Sadak Yojna (PMGSY)

Necessity of alternate Necessity of alternate materialsmaterials

• Large quantities of construction materials required

• Scarcity of good quality aggregates / soil for road construction

• Waste and marginal materials like flyash

• Disposal and environmental problem

Properties of Fly ashProperties of Fly ash

Major constituents - Oxides of silica, aluminum, iron, calcium & magnesium

Favourable properties for embankment & road construction - Pozzolanic nature

- Light weight, Non plastic- High shear strength- Ease of compaction- Self hardening- Amenable to stabilization- High permeability- Faster rate of consolidation

Utilization of Fly ashUtilization of Fly ash

• Construction of embankments / backfills

• Stabilization of subgrade and sub-base

• Construction of semi-rigid / rigidpavements

Engineering Properties of Fly ashEngineering Properties of Fly ashParameter Range Specific Gravity 1.90 – 2.55 Plasticity Non-Plastic Maximum Dry Density (gm/cc) 0.9 – 1.60 Optimum Moisture Content (%) 18-38 Cohesion (kN/m2) Negligible Angle of Internal Friction () 300 - 400 Coefficient of Consolidation Cv (cm2/sec)

1.75 x 10-5 - 2.01 x 10-3

Compression index Cc 0.05 – 0.4 Permeability (cm/sec) 8 x 10-6 - 7 x 10-4 Partcle Size Distribution (% of materials) Clay size fraction Silt size fraction Sand size fraction Gravel size fraction

1 – 10 8 – 85 7 – 90 0 – 10

Coefficient of Uniformity 3.1 – 10.7

Physical Characteristics for Flyash as Pozzolana

Indian Roads CongressSpecial Publication 58

Guidelines For Use Of Flyash In Road Embankment

Published in 2001

Guidelines for Use of Fly ash in Guidelines for Use of Fly ash in Road EmbankmentsRoad Embankments

These guidelines provide salient details regarding design and construction of road embankments using fly ash

• Site investigations• Characterization of materials• Detailed design• Clearing and grubbing• Stripping and storing top soil• Setting out• Dewatering• Compacting the ground supporting embankment• Handling and transportation of fly ash• Spreading and compaction

Fly Ash for Road Embankment

Earth Cover Earth

Cover

Bottom ash or Pond ash

Typical cross section of fly ash road embankment

FLYASH

FLYASH

FLYASH

Bituminous Top

Granular Layer

SelectedEarth Cover

Shoulder

0.5m minimum

Natural Ground Level

1-3m

Typical cross section of fly ash road embankment

Approach Embankment for Second Approach Embankment for Second Nizamuddin Bridge at DelhiNizamuddin Bridge at Delhi

– Length of embankment - 1.8 km – Height varies from 6 to 9 m– Ash utilized - 1,50,000 cubic metre– Embankment opened to traffic in 1998– Instrumentation installed in the

embankment showed very good performance

– Approximate savings due to usage of fly ash is about Rs.1.00 Crore

Design ConsiderationDesign Consideration

The following major factors weighted heavily while designing the fly ash embankment

Adverse site condition – location of site in flood plain area

Low specific gravity of fly ash- may lose strength under submergence

Non availability of specific data and specifications of using fly ash as structural fill

Approach Embankment for Nizamuddin Bridge Approach Embankment for Nizamuddin Bridge

Slope stability analysis of fly ash embankmentSlope stability analysis of fly ash embankment(Different side cover thickness)(Different side cover thickness)

Details Factor of safetyCase I Case II

6 m high embankment, 1 m side cover throughout

1.5 m side cover throughout

2 m side cover upto mid height and remaining portion 1 m cover

2 m side cover throughout

--

1.30

1.42

1.48

1.05

1.20

1.36

1.41

Case I Fly ash saturated upto mid height

Case II Fly ash saturated upto top level

Approach Embankment for Second Approach Embankment for Second Nizamuddin Bridge at DelhiNizamuddin Bridge at Delhi

Spreading of pond ash

Compaction of pond ash

Second Nizamuddin Bridge Approach Embankment


Stone pitching for slope protection

Traffic plying on the embankment


Following instruments installed for monitoring performance of embankment

– Magnetic settlement gauges for settlement

– Pressure cells for base pressure – Pore pressure transducers for pore

water pressure measurement

InstrumentationInstrumentation


Installation of pressure cells

Installation of settlement gauge under progress


– No settlement of the embankment structure (fly ash fill)

– No pressure variation with in embankment body

– No change in saturation level of fly ash fill

Inferences from instrumentation dataInferences from instrumentation data

TechnoTechno--Economic AdvantagesEconomic Advantages

• Direct saving of about Rs.One Crore in second Nizamuddin Bridge project for PWD

• Additional savings to Vidyut Board, saving of precious top soil

• In road projects savings to the extent of 15-20 per cent can be achieved

• Savings depend on cost of transportation of fly ash

1.6 m

.3 m (drain) ((drain)

2.3 m

0.15 m, M15 concrete

1 m

0.5 m

2.0

10.2 mPond ash

7.0 m1.2 m

Existing Embankment

4.0 m

Filter 0.2 m, thickStone pitching, 0.3 m thick

Ground level

6 m

H.F.L

Foot path

0.6 m x 0.8 m parapet wall

1.5 m

1.5 m

Existing carriage way

Stone pitching to be removed

Weep holes at 1-2m c/c

Intermediate soil layers (0.2 m compacted thickness)

Parameter Pond ash Earth cover Sub soil

bulk 1.56 kg/cm2 2.0 kg/cm2 1.8 kg/cm2

c 0 0.15 kg/cm2 0

33o 28o 30o

Sat.condition Factor of safety

With Earthquake Without Earthquake

At H.F.L 1.06 1.7

Sudden drawdown

1.2 1.35

Fly ash Embankment from G.T Road to Kajouri chowk, Delhi

Filter material by the side of toe wall

Stone pitching on filter material

Drainage system in the embankment

USE OF POND ASH FOR ROAD USE OF POND ASH FOR ROAD EMBANKMENT EMBANKMENT

(Four-laning work on NH-6, Dankuni to Kolaghat, Km 17 to 72, West Bengal)

• National Highways Authority of India – Client

• M/s ICT, India and SNC-LALALIN,Canada –Consultant

• M/s Road builders (M) Shd.Bhd, Malaysia - Contractor

AGENCIES INVOLVEDAGENCIES INVOLVED

FourFour--laning work on NHlaning work on NH--6, Dankuni to Kolaghat,6, Dankuni to Kolaghat,

• Length of road - 60 km

• Height of embankment - 2 to 4 m

• Water logged conditions

• Soft sub-soil conditions

TYPICAL ROAD FEATURES/CONDITIONS TYPICAL ROAD FEATURES/CONDITIONS OF THE PROPOSED ROADOF THE PROPOSED ROAD


c

Existing carriageway

Typical CrossTypical Cross--section of Existing section of Existing HighwayHighway


EXISTING CONDITION OF ROADEXISTING CONDITION OF ROAD


EXISTING CONDITION OF ROAD OTHER EXISTING CONDITION OF ROAD OTHER SIDESIDE


PRELIMINARY INVESTIGATION AND PRELIMINARY INVESTIGATION AND ASSESSMENT OF SITE CONDITIONSASSESSMENT OF SITE CONDITIONS

• Medium to High rainfall• Water table is high• Waterlogged conditions

• Subsoil generally weak– Silty clay or clayey soil up to 20 m depth– SPT values in the range of 2 to 5– C = 0.25 kg/cm2, = 0o


NEED FOR ALTERNATIVE MATERIALNEED FOR ALTERNATIVE MATERIAL

• Earth proposed in contract document. Earth requirement –approx. 2.0 million cum.

• Haul distance more than 100 km.• High transportation cost• Delays expected in the completion of the

project


LABORATORY AND FIELD LABORATORY AND FIELD INVESTIGATIONSINVESTIGATIONS

• Characterisation of soil and fly ash

• Sub-soil investigations

• Stability analysis with soil and fly ash as fill materials

• Evaluation of data to arrive at appropriate methodologies for construction


ARRANGEMENT FOR DEWATERING OF ARRANGEMENT FOR DEWATERING OF STAGNANT WATERSTAGNANT WATER


CONDITION OF THE GROUND AFTER CONDITION OF THE GROUND AFTER DEWATERINGDEWATERING


Soil cover (1.5 m thick)

Sand or bottom ash min. 0.5 m thick

Improved Subgrade of compacted thickness not less than 50 cm

Geotextile

Fly ash in compacted layers of 200 mm thickness

Temporary pond ash bund

Existing embankment

2 m 2 m

Median

21

Proposed berm of pond ash after completion of embankment

Granular sub-base

Min. 0.5 m

PROPOSED ALTERNATIVES FOR PROPOSED ALTERNATIVES FOR CONSTRUCTIONCONSTRUCTION


SPREADING OF GEOTEXTILE SPREADING OF GEOTEXTILE OVER SOFT GROUNDOVER SOFT GROUND


SPREADING OF FLY ASH OVER SPREADING OF FLY ASH OVER GEOTEXTILEGEOTEXTILE


COMPACTION OF FLY ASH OVER COMPACTION OF FLY ASH OVER GEOTEXTILE LAID ON SOFT GEOTEXTILE LAID ON SOFT

GROUND, (WORK ON THIS PROJECT GROUND, (WORK ON THIS PROJECT IS IN PROGRESS)IS IN PROGRESS)


Kalindi Road Project

SCPT Test In Progress

General Site Condition

Subsoil Investigation in Progress

Reinforced Fly ash EmbankmentReinforced Fly ash Embankment

• Fly ash - better backfill material for reinforced embankments

• Polymeric reinforcing materials - Geogrids, friction ties, geotextiles

• Construction sequence - similar to reinforced earth structures

Okhla Flyover Approach EmbankmentOkhla Flyover Approach Embankment

– First geogrid reinforced fly ash approach embankment constructed in the country

– Length of embankment - 59 m – Height varied from 5.9 to 7.8 m– Ash utilised - 2,700 cubic metre– Opened to traffic in 1996– Performance has been very good

Facing PanelsFilter Medium Geogrids

Pond Ash Fill

Reinforced Foundation Mattressof Bottom ash

7.8 m

7.8 m to 5.9 m

Okhla Flyover Approach EmbankmentOkhla Flyover Approach Embankment

Okhla Flyover Approach Embankment

Erection of facing panels

Rolling of pond ash

Okhla Flyover Approach Embankment

Support provided to facing panels during construction

Laying of geogrids

Hanuman Setu Flyover Approach EmbankmentHanuman Setu Flyover Approach Embankment

– Geogrid reinforced fly ash approach embankment

– Length of embankment - 138.4 m – Height varied from 3.42 m to 1.0 m– Opened to traffic in 1997

Reinforced Retaining Wall at Sarita Vihar Flyover

Sarita Vihar Flyover Approach Sarita Vihar Flyover Approach EmbankmentEmbankment

– Length of embankment - 90m – Max height - 5.25 m– Embankment opened to traffic in

Feb 2001– Polymeric friction ties used for

reinforcement

Sarita Vihar Flyover Reinforced Approach Embankment

Arrangement of friction ties before laying pond

ash

Laying of friction ties

Sarita Vihar Flyover Reinforced Approach Embankment

Compaction using plate vibrator near the

facing panels

Compaction of pond ash using static and vibratory rollers

Design of Reinforced Flyash Embankment

• Height of Wall – 8m • Reinforcing Material – Geogrid • Back Fill – Soil and Flyash• Design of Wall- BS 8006-1995• Checks made- Internal and External Stability

- F.S. against Sliding- F.S. against overturning- F.S against bearing capacity- F.S. against rupture- F.S. against pullout

No of Layers = 12

0.20.81.422.63.23.8

4.6

5.4

6.2

7

0 2 4 6 8Length of geogrid (m)

Vert

ical

Spa

cing

(m)

No of Layers = 16

0.20.611.41.82.22.633.43.8

4.4

5

5.6

6.2

6.8

7.4

0 2 4 6 8

Length of geogrid (m)

Vert

ical

Spa

cing

(m)

Soil Fly Ash

F.S. Sliding 1.97 2.18

F.S. Overturning 4.10 4.50

Bearing Pressure 259 KN/m2 179 KN/m2

Slope Failure of High Embankment of Noida- Greater Noida Expressway

Salient features of site• Height of embankment

varies from 3m to8m• Approximately 23 km

stretch • Six Lane Carriageway

with Median

• Side shoulders – 1.5mPaved & 1m Unpaved

• Flyash covered with Good Earth

Noida-Greater Noida Expressway

CrossCross--Section Proposed for NOIDASection Proposed for NOIDA--GREATER NOIDA Express HighwayGREATER NOIDA Express Highway

Causes and types of Failure

• Heavy Runoff from six lane carriageway discharged water on side slopes•Sandy Silty soil was used as cover without proper slope protection•Severe Erosion on superelevated sections• Absence of longitudinal kerb channel and chutes allowed water to drain off along slope

Types of Failure

• Failures observed on both sides of slope

•More pronounced on d/s side

•Deep cavities were observed exposing fly ash at many locations

• Undermining caused caving in of road pavement

Causes of Failure

• Heavy flow of water intersected side slopes inspite of grass turfing

•Deep pits in slope to provide foundation for crash barrier and electric poles

•Pits were loosely backfilled

Immediate Preventive Measures

• Prevention of flow of water in side slopes by providing soil filled up bags through out the slope

•Filling of soil in erosion gullies

•Filling of soil filled bags in deep cavities

Long Term Remedial Long Term Remedial MeasuresMeasures

• Compaction of Side Slopes

• Provision of Toe Walls

• Provision of Kerb Channel

• Provision of Chutes

• Provision of drains in Medians

• Provision of Stone Pitching along with Filter (Granular/Geotextile)

Remedial Measures

IRC Guidelines / SpecificationsIRC Guidelines / SpecificationsGuidelines available on pavement construction

IRC 60 ‘Tentative guidelines for use of lime fly ash concrete as pavement base or subbase’

IRC 68 ‘Tentative guidelines on cement fly ash concrete for rigid pavement construction’

IRC 74 ‘Tentative guidelines for lean cement concrete and lean cement fly ash concrete as a pavement base or subbase’

IRC 88 ‘Recommended practice for lime fly ash stabilised soil as base or subbase in pavement construction’

ConclusionsConclusions• Ideally suited as back fill material for urban/

industrial areas and areas with weak sub soils• Higher shear strength leads to greater stability• Design is similar to earth embankments• Intermediate soil layers for ease of construction

and to provide confinement• Side slope erosion needs to be controlled by

providing soil cover• Can be compacted under inclement weather

conditions• Use of vibratory rollers is preferred

In road projects savings to the extent of 15-25 per cent can be achieved. Savings depend on cost of transportation of fly ash

Coarse ash is suitable as a fill material, finer part of the ash (fly ash) collected in dry form can be used to replace cement

Fly ash collection and handling techniques need to be improved

Use of ash for all road projects in the vicinity of thermal power plant should be made mandatory

Conservation of conventional construction materials is possible by adopting fly ash for road construction

Thank youThank you

Use of Fly Ash for Road and Embankment Construction CRRI Sudhir Mathur

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