Earthwork for Road Construction
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EARTHWORK FOR ROAD EMBANKMENTS
Presentation by
Dr. Vasant G. Havanagi
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INTRODUCTION
• Pavement failures due to settlement of embankment fill and subgrade
• Need for suitable fill materials and proper quality control during execution
• Adoption of MORTH specifications
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Types of soil in IndiaTypes of soil in India
Alluvial soils Fine sands Coastal soils BC soils Red gravelly soils
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Types of soil in IndiaTypes of soil in India
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Desirable properties of Desirable properties of soilsoil
Stability Incompressibility Permanency of strength Minimum changes in volume &
stability Good drainage Ease of compaction
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Undesirable types of Undesirable types of soilsoil
Highly plastic soils Soils which favour capillary rise of water Frost susceptible soils Organic and sulphatic soils Permissible limits
Sodium sulphate - 0.5 per cent maximum Organic matter - 1.0 per cent maximum
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EARTHWORK FOR EMBANKMENT/SUBGRADE
• SUITABILITY OF MATERIALSFree from peat, perishable and other organic
materialShould not be spontaneously combustibleLL 70, PI 45With salts are not suitableFree Swell Index 50 % should not be used Total sulphate content ( 0.5 %) must be avoided
within 500mm of metallic itemsBorrow pits – max.depth 1.5m, offset from toe min.
10m.
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EARTHWORK FOR EMBANKMENT/SUBGRADE (Contd.)
• SIZE OF MATERIAL Size of coarse material 75 mm in
embankment fill 50 mm in subgrade Max. particle size 2/3 of compacted
layer thickness
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Density requirements for Embankment and Subgrade (Section 305.2.1.5)
S.No. Type of work Maximum laboratory dryunit weight when tested as
per IS: 2720 (Part 8)
1. Embankments up to 3 metresheight, not subjected toextensive flooding
Not less than 15.2 kN/cu.m
2. Embankments exceeding 3metres height orembankments of any heightsubject to long periods ofinundation
Not less than 16.0 kN/cu.m
3. Subgrade and earthenshoulders/verges/backfill
Not less than 17.5 kN/cu.m
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Construction operations (MORTH specifications-305.3)
• Clearing and grubbing• Setting out• Dewatering• Stripping and storing top soil• Compacting ground supporting
embankment/subgarde.• Spreading material and bringing to
appropriate moisture content.
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EARTHWORK FOR EMBANKMENT/SUBGRADE (Contd.)
• Spreading of material in layers and
bringing to appropriate moisture content. Max. compacted thickness = 20 cm Moisture content (-2 % + 1% of OMC)
Expansive soils (@ OMC or on wet side of optimum) Pan drying method Oven drying method Speedy moisture meter (AASHTO T-217) Microwave oven method
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EARTHWORK FOR EMBANKMENT/SUBGRADE (Contd.)
• Compaction Smooth wheel rollers Sheep foot rollers Pneumatic tyred rollers Vibratory rollers
• Other compacting equipments Small vibratory rollers Plate vibrators Rammers
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Objectives of soil compactionObjectives of soil compaction
• Increase in strength
• Reduction in compressibility
• Reduction in tendency for subsequent changes in moisture content
• Reduction in erodability
• Reduction in frost susceptibility
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Factors influencing Factors influencing compactioncompaction
• Type of soil
– Gradation (Well-graded/Uniformly-graded)
– Clayey soil
– Silty soil
– Sandy soil
– Gravel
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Moisture-density relationship for Moisture-density relationship for different types of soilsdifferent types of soils
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Factors influencing Factors influencing compactioncompaction (contd.)
• Moisture content– Dry of optimum
– Optimum
– Wet side of optimum
• Compactive effort– Energy applied per unit weight of soil
• Weight of rammer, height of fall, number of blows
• Weight of roller, number of passes
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Moisture-density relationshipMoisture-density relationship
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Effect of compaction on soil Effect of compaction on soil propertiesproperties
• Unconfined compressive strength
• California Bearing Ratio (C.B.R)
– Unsoaked C.B.R
– Soaked C.B.R
• Permeability
• Settlement
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Relation between density and unconfined compressive strengthRelation between density and unconfined compressive strength
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Relation between density and CBR for a heavy clayRelation between density and CBR for a heavy clay
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Variation of CBR of silty clay with Variation of CBR of silty clay with compactioncompaction
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Compaction-permeability relation for clayCompaction-permeability relation for clay
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Effect soil content & size of aggregate on Effect soil content & size of aggregate on CBRCBR
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Field compacting Field compacting machinerymachinery (Contd)
• Smooth wheel roller
– Used for compacting subgrade, base and asphaltic surfaces
– Suitable for compacting gravels, sand, and crushed rock
– 8 to 10 tonne rollers
– Appropriate speed of the roller should be 3 - 6 km/h.
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Conceptual structure of compacted material using static roller
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Field compacting Field compacting machinerymachinery (Contd)
• Sheepsfoot roller
– Used in road and earthen dam works
– Suitable for compacting heavy clays and silty clays
– Important parameters affecting compaction• Weight of roller
• Area of each foot
• Number of foots/lugs in contact with the ground at any time
• Contact area of the foot
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Field compacting Field compacting machinerymachinery (Contd)
• Pneumatic tyred rollers
– Used for both earthwork and bituminous works
– Suitable for compacting cohesionless gravel,
sand and cohesive soils
– Important parameters affecting compaction• Tyre inflation pressure• Area of contact
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Field compacting Field compacting machinerymachinery (Contd)
• Vibratory rollers– Higher compaction level can be achieved with
minimum work
– Compaction can be done up to greater depths
– Output is many times more than conventional rollers
– Suitable for compacting sand and gravels
– Important parameters affecting compaction• Dead load
• Frequency
• Amplitude
• Area of contact
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Vibratory Vibratory rollerroller
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Conceptual structure of compacted material using vibratory roller
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Effect of frequency on compactions of gravel
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Density depth relationship with various compaction unit
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Field compacting Field compacting machinerymachinery (Contd)
• Vibratory plate compactors– Useful for small road works and narrow areas such as trench
backfilling
– Suitable for compacting thin layers
– Can be tractor-towed
• Rammers– Provide impact load
– Suitable for compacting small areas, back filling of trenches
in foundations
– Suitable for compacting cohesive as well as non-cohesive soils
– Operated manually (driven by petrol engines)
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Small Small vibratory vibratory rollerroller
Plate Plate compactcompact
oror
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Lift thickness during Lift thickness during compactioncompaction
• Depends on different factors
– Type of roller
– Weight of roller
– Type of soil
– Number of passes
– Prevailing moisture content
– Degree of compaction required
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DozersDozers
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JCB JCB (Backhoe (Backhoe cum cum Loader)Loader)
Motor Motor gradergrader
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Tractor as Tractor as gradergrader
Tractor Tractor as as
ploughplough
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Construction in urban areas
Need of survey of underlaying Cables, Water pipe lines, and Sewer lines etc. Shifting the same as per requirement.
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EARTHWORK FOR EMBANKMENT/SUBGRADE (Contd.)
Man hole in the centre of Compacted subgrade
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EARTHWORK FOR EMBANKMENT/SUBGRADE (Contd.)
• Field density control Core cutter method Sand replacement method Non-destructive methods, Nuclear density
gauge (AASHTO T-238, ASTM D-2922,D-3017)
• Relative compactionField dry density x 100
Laboratory density
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Compaction requirements for embankment and subgrade (Table 300-2,MORTH specifications)
S.No. Type of work/material Relative compaction aspercentage of max. laboratory drydensiy as per IS: 2720 (Part 8)
1. Subgrade and earthenshoulders
Not less than 97
2. Embankment Not less than 95
3. Expansive clays
(a) Subgrade and500 mm portionjust below thesubgrade
(b) Remainingportion ofembankment
Not allowed
Not less than 90
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Sl.No Test Relevant code
Frequency of test
1. Deleterious content IS:2720 : Part - 27
Min 2 tests per borrow area
2. Natural Moisture content IS:2720 : Part - 2
1 test / 250 m3
3. Gradation IS:2720 : Part - 4
2 tests / 3000 m3
4 Plasticity Index IS:2720 : Part - 5
2 tests / 3000 m3
5. Compaction tests IS:2720 : Part - 8
2 tests / 3000 m3
6. C.B.R IS:2720 : Part - 16
1 test / 3000 m3
7. FField density(a) Embankment (b) Subgrade/shoulders
IS:2720 : Part – 28
IS:2720: Part - 29
1 test / 1000 m2
1 test / 500 m2
Quality control tests and their frequencies (Section 903,MORTH)
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QUALITY CONTROL (Contd.)
• Tolerances in surface levels in subgrade
+ 20 mm, -25 mm
• Acceptance crireria
Mean density should not be less than
specified density +
1.65 - 1.65 times the standard deviation
(No. of samples)0.5
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EARTHWORK UNDER SPECIAL CONDITIONS (MORTH specifications 305.4)
• Compacting ground supporting Embankment/Subgrade
• Earthwork over existing road surface
• Earthwork for widening existing road embankment
• Embankment construction under water
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EROSION CONTROL (MORTH SPECIFICATIONS 306 TO 308
• Common methods Turfing with sods Seeding and mulching with jute/geo netting
Special techniquesUse of geocellsSlopes in cohesionless sands and
black cotton soils
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Erosion Control of Slopes
Use of Jute Geotextile
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GEOCELL FOR SLOPE STABILIZATION AND EROSION CONTROL
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CASE STUDIES
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APPROACH EMBANKMENT FOR SECOND APPROACH EMBANKMENT FOR SECOND NIZAMUDDIN BRIDGE AT DELHINIZAMUDDIN BRIDGE AT DELHI
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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
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APPROACH EMBANKMENT FOR SECOND APPROACH EMBANKMENT FOR SECOND NIZAMUDDIN BRIDGE AT DELHINIZAMUDDIN BRIDGE AT DELHI
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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 safety
Case 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
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Spreading of pond ash
Compaction of pond ash
Second Nizamuddin Bridge Approach Embankment
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Second Nizamuddin Bridge Approach Embankment
Stone pitching for slope protection
Traffic plying on the embankment
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PITCHING/REVETMENT OF SLOPES• Road embankment with stone, boulders• Stones in wire crates over a layer of granular
material (filter)-protection against river action.• Size and weight shall conform to clause 5.3.5.1 of
IRC:89• Min.weight of stone 40 kg.• Size of spalls min.25mm• Use of cement concrete blocks (M15) when
stones not available
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Approach Embankment for Nizamuddin Bridge Approach Embankment for Nizamuddin Bridge
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
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Deatails of instrumentation
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Second Nizamuddin Bridge Approach Embankment
Installation of pressure cells
Installation of settlement gauge under progress
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Approach Embankment for Nizamuddin Bridge Approach Embankment for Nizamuddin Bridge
– No settlement of the embankment structure (fly ash fill)
– Development of negligible pore water pressure
INFERENCES FROM INSTRUMENTATION DATAINFERENCES FROM INSTRUMENTATION DATA
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TECHNO-ECONOMIC ADVANTAGESTECHNO-ECONOMIC 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
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USE OF POND ASH FOR ROAD USE OF POND ASH FOR ROAD EMBANKMENTEMBANKMENT
(FOUR-LANING WORK ON NH-6, DANKUNI TO KOLAGHAT, KM 17 TO 72, WEST BENGAL)
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• Length of road - 60 km
• Height of embankment - 2 to 4 m
• Water logged conditions
• Soft sub-soil conditions
TYPICAL ROAD TYPICAL ROAD FEATURES/CONDITIONS OF THE FEATURES/CONDITIONS OF THE
PROPOSED ROADPROPOSED ROAD
Four-laning work on NH-6, Dankuni to Kolaghat,Four-laning work on NH-6, Dankuni to Kolaghat,
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EXISTING CONDITION OF ROAD OTHER EXISTING CONDITION OF ROAD OTHER SIDESIDE
Four-laning work on NH-6, Dankuni to Kolaghat,Four-laning work on NH-6, Dankuni to Kolaghat,
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EXISTING CONDITION OF ROADEXISTING CONDITION OF ROAD
Four-laning work on NH-6, Dankuni to Kolaghat,Four-laning work on NH-6, Dankuni to Kolaghat,
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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
Four-laning work on NH-6, Dankuni to Kolaghat,Four-laning work on NH-6, Dankuni to Kolaghat,
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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
RECOMMENDATION OF POND ASH AS AN ALTERNATIVE MATERIAL
Four-laning work on NH-6, Dankuni to Kolaghat,Four-laning work on NH-6, Dankuni to Kolaghat,
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Soil cover (1.5 m thick)
Improved Subgrade of compacted thickness not less than 50 cm
Fly ash in compacted layers of 200 mm thickness
Temporary pond ash bund
Existing embankment
Median
2
1
Proposed berm of pond ash after completion of embankment
Granular sub-base
Min. 0.5 m
Rock or boulder filling
PROPOSED ALTERNATIVES FOR CONSTRUCTION
Alternative 1
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Fly ash in compacted layers of 200 mm thickness
Soil cover (1.5 m thick)
Improved Subgrade of compacted thickness not less than 50 cm
Granular material (Cu > 10)
Temporary pond ash bund
Existing embankment
Median
2
1
Proposed berm of pond ash after completion of embankment
Granular sub-base
Min. 0.5 m
PROPOSED ALTERNATIVES FOR CONSTRUCTION
Alternative II
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PROPOSED ALTERNATIVES FOR CONSTRUCTION
Alternative III
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RESULTS OF STABILITY ANALYSISRESULTS OF STABILITY ANALYSIS
Condition Fill material Minimum factor of safety
Unsaturated condition
Soil 1.62
Pond ash 1.92
Saturated condition
Soil 1.36
Pond ash 1.50
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ARRANGEMENT FOR DEWATERING OF ARRANGEMENT FOR DEWATERING OF STAGNANT WATERSTAGNANT WATER
Four-laning work on NH-6, Dankuni to Kolaghat,Four-laning work on NH-6, Dankuni to Kolaghat,
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CONDITION OF THE GROUND AFTER CONDITION OF THE GROUND AFTER DEWATERING AND SCARIFYINGDEWATERING AND SCARIFYING
Four-laning work on NH-6, Dankuni to Kolaghat,Four-laning work on NH-6, Dankuni to Kolaghat,
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SPREADING OF GEOTEXTILE SPREADING OF GEOTEXTILE OVER SOFT GROUNDOVER SOFT GROUND
Four-laning work on NH-6, Dankuni to Kolaghat,Four-laning work on NH-6, Dankuni to Kolaghat,
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COMPACTION OF BOTTOM ASH OVER THE GEOTEXTILE
Four-laning work on NH-6, Dankuni to Kolaghat,Four-laning work on NH-6, Dankuni to Kolaghat,
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UTILISATION OF FLY ASH IN THE WIDENING PORTION OF
EMBANKMENT (AT SHASTRI PARK, NEW DELHI)
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EMBANKMENT CONSTRUCTION AT SHASTRI PARK
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OVERALL STABILITY OF FLY AH EMBANKMENT WITH 2 M TOE-WALL
Parameter
Pond ash
Earth cover
Sub soil
bulk 15.6 kN/m3
20 kN/m3
18 kN/m3
c 0 15 kN/m3
0
33o 28o 30o
Properties of soil
STABILITY ANALYSIS
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FLY ASH EMBANKMENT WITH TOE WALL
EMBANKMENT CONSTRUCTION AT SHASTRI PARK (CONTD.)
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FILTER MEDIA BEHIND RETAINING WALL
EMBANKMENT CONSTRUCTION AT SHASTRI PARK (CONTD.)
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Dredging Plant used for Transporting Sand from Yamuna
Construction of embankment using Hydraulic fill Technique
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Dredging of Sand Through Pipes
Construction of embankment using Hydraulic fill Technique (Contd.)
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Pumping of Dredged Sand
Construction of embankment using Hydraulic fill Technique (Contd.)
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Drainage Pipes used for Disposal of Water
Construction of embankment using Hydraulic fill Technique (Contd.)
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Spreading of Dredged Sand using Dozer
Construction of embankment using Hydraulic fill Technique (Contd.)
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Embankment built using Dredged Sand
Construction of embankment using Hydraulic fill Technique (Contd.)
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Stone Pitching on Embankment Slope
Construction of embankment using Hydraulic fill Technique (Contd.)
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Construction of Embankment in Salt Infested Area - Runn of Kutch on
Indo-Pak Border in Gujarat
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The Problem• The embankment fill consists of soil excavated within
Runn of Kutch
• High salt content (0.44-1.28%)
• Rills are formed on the slope, which shows highly erosive nature of soil
7m
1:2
1.5m
India Pakistan
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RD 31.975 Pak Side
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Causative Factors• Overflowing of water:• Wave action• Piping phenomenon resulting in slope failure and
subsidences.• Reduction of effective stresses
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The Solution (Contd)
Fig. 2 Proposed Measures for A2 and B1 Sections
Locally Available GSB
H
CC 1:4:8
GL
450
35
300
600
2.25 H
Formation Height
150
100
150 GSB 100
380
Existing Toe Wall
Provision of Toe wall and GSB
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The Solution (Contd)
Proposed sections in water logged areas
Fig 3 Proposed Measures for B2 and C1 Sections
GL 35150
H
CC 1:4:8
450
300
600
2.25 H
Formation Height
Existing Toe Wall
Dry stone pitching filled with gravel on Existing slope
100
150 GSB 100
380
Geotextile
Fig 4 Proposed Measures for C2 Section
CR Masonryof Variable Height
150
600Dry Stone Pitching Filled with Gravel
Formation Height
Geotextile
Original side slope
Existing Toe wall
CC 1:4:8
450
380
150
100
300
35
H
2.25 H
150 GSB 100
GL
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The Solution (Contd)
Fig. 5 Proposed Measures for locations having height of Toe wall > 1000mm
Formation Height
Geotextile
Original side slope
35
CC 1:4:8
GL
600
150
100
400
150 GSB 100
Dry CR Masonry of
Variable Height
Dry stone pitching filled with gravel on Existing slope
H
2.25 H
600
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