Geosynthetics in Flexible Pavements and Carbon Foot Print Analysisand Carbon Foot Print Analysis
Prof. K. RajagopalDepartment of Civil EngineeringDepartment of Civil Engineering, IIT Madras, Chennai, India 600036
f fThis work was part of M.Tech. projects of AvinashUnni, S. Chandramouli, K. Iniyan & Lt.Col. Tushar VigThanks are also d e to Prof A Veeraraga an and DrThanks are also due to Prof. A. Veeraragavan and Dr.Sivakumar Palaniappan
Outline• Field and Laboratory tests performed to
th i fl f ll lassess the influence of geocell layer• Equivalent modulus of the geocell layer q g y
evaluated• Influence on pavement thickness• Influence on pavement thickness
evaluated through stress analysis programsprograms
• Carbon foot print analysis of construction activities
Back ground (GEOCELL)g ( )• Expandable 3-d permeable,
h b b t thoneycomb or web structure,made of strips of polymerIn ented b the US arm corps• Invented by the US army corpsof engineers in the 1970’s toconstruct temporary roads for3D Cellular confinement system construct temporary roads forheavy military vehicles overweak soils
(GEOCELL)
• Extensively used by US Armyduring the Gulf war for effective
fmoving of militaryvehicles/trucks over the desertsandO iginall de eloped b US sand.Originally developed by US
Army Corps of Engineers (1979)
Simultaneous Mechanisms in 3 DimensionsDimensions
a) Unreinforced soil subjected to shear a. When pressure is applied on unreinforced weak soils, failure occurs immediately due to lateral flow of soil
b. When surface soil is confined by geocells,b. When surface soil is confined by geocells, failure mechanism is suppressed from formation.
S f t f d tb) Pushing decrease by confinement c. Surface pressures are transferred to deeper strata due to interaction.
c) Lateral stress on cell due to stress with in the cell Ofer and Rajagopal (2008)
Simultaneous Mechanisms in 3 Dimensions
c) Hoop stress development
The three dimensional structure confinesthe infill soil, limiting lateral deformation.Lateral expansion of the infill is restricted by
d) Passive resistance of neighbouring cells
high hoop stress.
) g ge) Interface friction force developed along the cell walls.
Because of all the above phenomena, the pressure transmitted to thefoundation soil reduces.
Trial Construction on an Expansive Clay soil
Trial road section with geocell reinforcement builtgeocell reinforcement built over a length of 200 m
Subgrade Soil at Site
CBR 4%Swell index 150%Swell index 150%Liquid Limit 60%Plastic Limit 25%Plastic Limit 25%
Shrinkage limit 8%
Geocell Reinforced Flexible Pavements
GEOCELL Reinforced Road construction at Govind Dairy Factory
Preparation of ground Stapling to join different geocells
Stretching of the geocell layer
Filling of stone aggregate in geocell Compaction by vibro-roller
Observations on the performance
R i f d tiUnreinforced section Reinforced sectionUnreinforced section
Reinforced section could maintain good level surface
Unreinforced section showed excessive surface depressionsexcessive surface depressions
Road surface was quite uneven Frequent repairs by dumping large Frequent repairs by dumping large
stones
Set Up for Laboratory Model TestsSet Up for Laboratory Model Tests
Soft clay bed prepared in the laboratory
Pressure‐Settlement
Pressure KPa
0
1
0 2 4 6 8 10 12
1
2
tlemen
t cm
3
4
Sett
4
5
6
The Avinash Unni Project Review150 Geocell Sand 150 Geocell GSB 100 Geocell GSB 50 Geocell GSB 100 WMM 50 Geocell Sand 50 Geocell Sand 2
Measured Pressures below geocell layer
The Avinash Unni Project Review
The Avinash Unni Project Review
Laboratory Model Tests
650 mm thick GSB base GSB + Geocell layer filled with sand or GSB
LABORATORY Model TESTS
100 ll d100 mm geocell with sand fill layer 100 mm geocell+sand
100 mm geocell+GSB 150 mm geocell+GSB
Typical results from Plate Load Tests
0 1000 2000 3000
pressure (kPa)
‐10
0
‐30
‐20
m)
‐50
‐40
men
t (m
100 mm Geocell+GSB
‐70
‐60
settl
em
100 ll d
100 mm Geocell+GSB
‐90
‐80100 mm geocell + sand
GSB alone‐100
GSB alone
Analysis of pressure-settlement data
1) KENPAVE (Elastic layer analysis):• Back calculation of modulus of geocell layer based on fieldBack calculation of modulus of geocell layer based on field
plate load test results• Calculation of modulus values of 50 mm,100 mm,150 mm
geocells layers with different in fills based on lab test results• Optimization done by calculating damage ratio and design
liflife
2) PLAXIS 2D Analyses2) PLAXIS 2D Analyses
• Back calculation of modulus of geocell layered pavement section
• Calculation of modulus values of 50 mm,100 mm,150 mm ll l ith diff t i fillgeocells layers with different in fills
Analysis of the Plate Load Test Datay
• E Value for subgrade (CBR 4%)• E- Value for subgrade (CBR 4%) = 10*4 =40 MPa
• E-Value for stabilized subgrade (CBR 6%) g ( )= 17.6*6^0.64 = 55.40 MPa
• E-value for GSB (225 mm thick) = 55400*0 2*225^0 45= 126 8 MPa= 55400*0.2*225^0.45= 126.8 MPa
• E-value for GSB (75mm thick) = 55400*0.2*75^0.45 = 77.3 MPa
• E-value for GSB (150 mm thick) = 55400*0.2*150^0.45 = 105.63 MPa
E l f GSB (400 thi k)• E- value for GSB (400mm thick) = 55400*0.2*400^0.45 = 164.2 MPa
Geocell Reinforced Flexible Pavements
Modulus Improvement FactorsModulus Improvement FactorsType of study MIFType of study MIFField tests 2.75 (150 mm geocell)Laboratory tests 2 92 (150 mm geocell)Laboratory tests 2.92 (150 mm geocell)
2.84 (50 & 100 mm geocell)
Pavement sections were designed using this revised modulus values and different subgrade CBR values
Geocell Reinforced Flexible Pavements
Pavement Thicknesses for 150 msa & 2% CBR
CombinationsIRC-
unreinforcedGeocell at Subgrade
Geocell in base and subgrade
BC 50 mm 50mm 50 mm
DBM 215 mm 185 mm 170 mmDBM 215 mm 185 mm 170 mm
WMM 250 mm 0Geocell with GSB-200
mm
GSB 460 mm 500 mm 100 mm200mm Geocell with soil infill on 200mm Geocell with soil
sub-grade 500 mm300mm
subgrade layerinfill on 300mm subgrade layer
cost (Rs.) / m2 2,635 2,490 2,450
Total thickness 975 mm 735 mm 520 mmDesign Life 16 years 20 years 20 yearsDesign Life 16 years 20 years 20 years
Geocell Reinforced Flexible Pavements
Geocell reinforced dirt track being constructed in a desert
Geocell Reinforced Flexible Pavements 21
Geocell reinforced dirt track being constructed in a desert area
Desert sand being filled in the geocell pockets
Mini-bucket wheel excavator for filling sand in geocell pockets
Heavy army trucks moving easily on the geocell track
Soil details
(Ref: http://maps.google.co.in)
CBR 3%
( p // p g g )
Plasticity index 45%
Swell index 140
Shrinkage limit 8%Shrinkage limit 8%
Section adopted at construction siteSection adopted at construction site
Max damage ratio 0.865
Field Plate Load TestField Plate Load TestTh f ll i t i d f d ti thThe following apparatus were required for conducting the test:
• Circular steel plate of 300 mm diameter and 30 mmCircular steel plate of 300 mm diameter and 30 mm thickness
• Hydraulic jack of capacity 300 kNy j p y• Supporting steel beam of length 5 m• Dial gauges having accuracy of 0.01 mm• Plumb bob• Spirit level• Short steel supporting members• Loaded truck
Compacted SubgradeCompacted Subgrade
1 Test set up Over Subgrade1. Test set up Over Subgrade
Test Result (Subgrade)
Pressure settlement curve for subgrade data
00 500 1000 1500 2000 2500 3000
Pressure (Kpa)
5
10
men
t (m
m)
Test 1Test 2
15
Sett
lem
20
25
2. Plate load test over Granular Subbase
3 Geogrid Reinforcement3. Geogrid Reinforcement
Subbase
Installing flexible and rigid geogridover subgrade
Compaction using rollerCompaction using roller
Set up Over Sub Base (Reinforced with flexible and rigid geogrid)
Pressure Settlement CurvePressure Settlement Curve
00 500 1000 1500 2000 2500 3000
Pressure (Kpa)
0
2
4)
PLAIN GSB Test 1
A GS 26
8
ent (
mm
) PLAIN GSB Test 2
GSB (with flexible GR) Test 1
GSB (with flexible GR) Test 210
12
14
Sett
lem
e
GSB (with rigid GR) Test 1
GSB (with rigid GR) Test 2
14
16
18
Field Density TestsField Density Tests
Field Density TestsField Density Tests
Fi ld d it t t d t d th• Field density tests were conducted over the subgrade and over the GSB (with and without reinforcement)reinforcement)
• Sand replacement method was performed as per• Sand replacement method was performed as per IS2720 PART-28
• For the same compaction efforts, the sub‐base layer compacted over geogrid layer achievedlayer compacted over geogrid layer achieved higher dry density
Data AnalysisData Analysis
KENPAVE (Elastic layered analysis software):
• Back calculation of modulus of Geogridreinforced pavement based on field plate load test results
• Optimization done by calculating damage ratio and design life
Data InputsData Inputs
Th f ll i t i d f l iThe following parameters required for analysis
• Thickness of layers
• Elastic Modulus
• Poisson's ratio
• Stress and contact area
STEP 1STEP 1
• As per IRC-37 the following formulas used for calculation of modulus of pavement layersp y
Calculation of ModulusCalculation of Modulus
• The applied load in the field test = 150 kNcorresponding settlement=10.47mmp g
Th di f h l 150• The contact radius of the test plate = 150 mm
• Modulus of the Sub base layer was obtained by t i l d d b t hi thtrial and error procedure by matching the measured settlement of 10.47 mm
KENPAVE RESULTKENPAVE RESULTS N E V l f U i f d V ti l Di l tS No E-Value of Unreinforced
layer (MPa)
Vertical Displacement
(mm)
1 65.11 12.49
2 100 10 782 100 10.78
3 105 10.55
4 107 10.47
5 110 10.35
Snapshot from KENPAVESnapshot from KENPAVE
IMPROVEMENT FACTORIMPROVEMENT FACTORI F E ( i f d) / E ( i f d)Improvement Factor = EBC (reinforced) / EBC (unreinforced)
Where E (reinforced) the mod l s of the reinforced base andWhere EBC (reinforced) = the modulus of the reinforced base and EBC (unreinforced) = the modulus of the unreinforced base
• The average value of the plate settlement at an applied load of 150 kN for the flexible reinforcement was 8.06 mm
• Considered the contact radius = 150 mm
• Contact pressure = load/area =150/area of plate = 2140 kPa
Flexible Geogrid ReinforcementFlexible Geogrid ReinforcementImprovement E-Value (Flexible Settlement (mm) p
Factor
(
Geogrid)
MPa
( )
on surface under
150 kN loadMPa 150 kN load
1 107 10 471 107 10.47
1.1 117.7 10.06
1.25 133.75 9.55
1.5 160.5 8.88
1.75 187.25 8.37
1.9 203.3 8.11
1.95 208.65 8.05
Rigid Geogrid ReinforcementRigid Geogrid ReinforcementI t E V l (Fl ibl G id) S ttl t ( )Improvement
Factor
E-Value (Flexible Geogrid)
MPa
Settlement (mm) on
surface under 15T load
1 107 10 471 107 10.47
1.25 133.75 9.55
1 5 160 5 8 881.5 160.5 8.88
1.75 187.25 8.37
2 214 0 7 952 214.0 7.95
2.25 240.75 7.61
2.3 246.1 7.55
The average value of the plate settlement at an applied load of 150 kN for theThe average value of the plate settlement at an applied load of 150 kN for the flexible reinforcement was 7.55 mm.
Layer OptimizationLayer Optimization
id i f d l id d d• Geogrid reinforced layers were considered and the thickness of the various alternate sections were analysed
• Damage ratio should not exceed the designed unreinforced section @ siteunreinforced section @ site
• Most economic and feasible section should be selected
Damage RatioDamage Ratio
Where
Nn
Di
if
Where,
Df is the damage factor,
N i
f g ,
ni is the actual number of vehicle movements of the ith load dgroup and
N is the maximum(allowable) number of vehicle movementsNi is the maximum(allowable) number of vehicle movements the structure can support for the ith load group.
Data Inputs
BC DBM WMM GSB
Poisson’s ratio 0.35 0.35 0.4 0.4
Flexible GG 2500 2500 88.94 208.65Flexible GG
reinforced section
E value (MPa)
2500 2500 88.94 208.65
E value (MPa)
Rigid GG reinforced 2500 2500 88.94 246.1
section
E value (MPa)
Cracking ModelCracking Model Th f il it i f ki i i b• The failure criteria for cracking is given by
Nf = f1 (Єr)-f2 (E1)-f
3WhereWhere,
Nf = allowable number of load repetition to preventNf = allowable number of load repetition to prevent fatigue crackingεt =tensile strain at the bottom of asphalt layerεt e s e s e bo o o sp yeE1=Elastic modulus of asphalt layerf1, f 2, f3 are constants1, 2, 3
Here f1 = 0.08060, f2 = 3.89, f3 = 0.8541 2 3
Rutting ModelRutting Model
f (Є ) fNd =f4 (Єc)-f5
Where,Nd = allowable number of load repetition to limitNd allowable number of load repetition to limit permanent deformationε = compressive strain on top of sub gradeεc = compressive strain on top of sub gradef4 and f5 are constants
Here, f4 = 4.1656x10-8, f5 = 4.5337
Optimised sections for different damage ratios (Flexible geogrid)
Optimised sections for different damage ratios (Rigid geogrid)
Reinforced Pavement SectionReinforced Pavement Section
EMISSION CALCULATION
Sustainable ConstructionSustainable ConstructionKey themes of sustainable construction practicesKey themes of sustainable construction practices
• Minimise the energy use in the all phases (production, construction, i d d f lif h )operation and end‐of‐life phases)
• Reduce environmental impacts during the life cycle
• Preserve and enhance bio‐diversity
• Conserve water and land resources
Ad t i ti t i l• Adopt innovative materials
• Reduce the generation of wastes at all level
Green house gas emissionsGreen house gas emissions
h i h• The primary greenhouse gases are water vapour, carbon dioxide, methane, nitrous oxide, and ozone
• Greenhouse gases usually affect the temperature of the earthtemperature of the earth
• Anthropogenic activities lead to the increase in green house gases
Need for AssessmentNeed for Assessment
M j it f t di i l f d• Majority of studies mainly focussed upon improving the energy efficiency of structures during the operational phaseduring the operational phase
• The environmental performance of onsite• The environmental performance of onsite construction processes is not currently being measured (Palaniappan et al. 2009)measured (Palaniappan et al. 2009)
• Quantification of carbon emissions from roadQuantification of carbon emissions from road projects is not followed yet
Site layoutSite layout
Ref: http://maps.google.co.in
Material Collection detailsMaterial Collection details
Logistics AssessmentLogistics AssessmentTh t l di id d i t b d• The pavement layers are divided into subgrade, Granular Sub base (GSB), Wet Mix Macadam (WMM) and Hot Mix Asphalt (HMA)p ( )
• Study included y
1. Raw material transportation to the yard, 2. Extraction3. Processing of raw materials4 Onsite operation4. Onsite operation
Data Collection StrategyData Collection Strategy
T l l h 28 kTotal length = 28 kmNo of Chainages = 14 h i k1 chainage = 2 kmPilot Study @ Chainage 34
Data collected for
Material Processing Transportation Onsite Operations
1. Material Transportation
Fuel Consumption details (Transportation)
Total fuel consumption for transportation
T l f l i (Li )
1524111 60 000
1,80,000
Total fuel consumption (Litres)
152411
1259801,20,000
1,40,000
1,60,000
in Litres)
Total fuel consumption (L)
7267480,000
1,00,000
e (Diesel
36526
20 000
40,000
60,000
Fuel usag
0
20,000
Subgrade GSB WMM HMA
F
2 Material Processing2. Material ProcessingGSB WMM Pl t ( ill t )GSB
Crushing of 50 m3 GSB
(litres)250
WMM Plant (pug mill type)
(Runs using DIESEL GENERATOR)
Processing of 25 m3 WMM 360Crushing of 1 m3 GSB
(litres)5
Total quantity (m3) 28000
( litres) 360
Processing of 1 m3 WMM( litres) 14.4
Total quantity (m ) 28000Fuel consumption (litres) 140000
Total quantity (m3) 56000Fuel consumption (litres) 806400
HMA PLANT
Processing of 10 m3 HMA( litres) 340
Processing of 1 m3 HMA( litres) 34
Total quantity (m3) 19600
Fuel consumption (litres) 666400
Total fuel consumption for material processing
50 %60
Material Processing‐ Fuel Consumption
50 %
41.3 %40
50
ption
20
30
l con
sum
8.6 %10
20
Fue
0GSB WMM HMA
Pavement Layer
3. ON-SITE OPERATION
h d i l d h• The processed materials are transported to the required site location and will be dumped
• The materials will be spread properly using p p p y gmachineries or labours and compacted well to reach the desired density
• Compaction is one of the critical processes in theCompaction is one of the critical processes in the onsite operations (involvement of machineries)
Onsite operation GSB LayerOnsite operation‐ GSB Layer
GSB placement and compaction
F lDuration
f N fTotal
ki F l
Equipment
Fuel efficiency
(LPH)
for chainage 34
(hrs)
No of chainage
s
working time (hrs)
Fuel use (diesel in
litres)B k h 5 660 9240 46200Back hoe 5 660
14
9240 46200Tractor dozer
(D155A) 27 770 10780 291060
d (GD623A1) 11 880 12320 135520grader (GD623A1) 11 880 12320 135520Roller (l&t CASE
459) 4.5 530 7420 33390
Total 506170
Total fuel Consumption- Onsite operationsO it ti
506170
6,00,000Onsite operation
382620
506170
2995303826204,00,000
5,00,000
Fuel261870 299530
2,00,000
3,00,000Fuel
consumption (Litres)
1,00,000
2,00,000
0Subgrade GSB WMM HMA Excavation
Pavement Layer
Total fuel consumptionTotal fuel consumptionT t l f l ti
Transportation
Total fuel consumption
12%
Raw material processing
Onsite activities43%
processing45%
CO Emissions for unreinforced sectionCO2 Emissions for unreinforced sectionTotal consumption from transportation (L) 393597.95
Total consumption from processing(L) 1612800
Total consumption from onsite activities(L) 1557330.32Emission factor (US EPA)(kg of CO2)Emission factor (US EPA)(kg of CO2)
One litre diesel = 2.664 kg CO2 2.664CO2
emission CO2
emission (Kg) (MT)
Transportation 1048544.9 1048.54
Processing 4296499.2 4296.50
Onsite 4148728.16 4148.73Total (for 28
km) 9493.77Total (per
k ) 339 0km) 339.0
Emission for Reinforced SectionEmission for Reinforced Section
• The optimised section designed using the flexible and the rigid geogrid reinforcement g g ghas been taken
• The emissions were calculated for both flexible geogrid reinforced and rigid geogridflexible geogrid reinforced and rigid geogridreinforced pavement section
CO Emissions for reinforced sectionCO2 Emissions for reinforced section
Emissions ComparisonEmissions ComparisonCO i i l K (MT)
339350
400CO2 emission per lane Km (MT)
266 263250
300
350
150
200
50CO2 emission
(MT)
50
100
0Unreinforced section Flexible Geogrid
reinforcementRigid Geogrid reinforcement
Economic AnalysisEconomic Analysis
h l i h b l l d f h• The layer wise cost has been calculated for the designed section without including the profit margin
• The same has been extended to reinforced sectionsection
• Reduction in construction duration in case of reinforced section is assessed
Cost of different sectionsActual section
Layer Quantity per Unit rate Cost
Flexible Geogrid
Layer Quantity per sq.mUnit rate
(Rs.)Cost
(Rs. per sq.m.)Layer sq.m (m3) (Rs.) (Rs. per sq.m)
Subgrade 0.5 375 187.5
GSB 0.2 1170 234
y Q y p q ( ) ( p q )
Subgrade 0.5 m3 375 187.5GSB 0.15 m3 1170 175.5WMM 0 2 m3 1445 289
WMM 0.4 1445 578
HMA 0.14 9498 1329.72
Sum 2329.22
WMM 0.2 m 1445 289HMA 0.14 m3 9498 1329.72Geogrid 1 No 130 130
Sum 2111.72Miscellaneous 116.4
Total 2445.7Miscellaneous 105.5
Total 2217.3
Rigid Geogridi
Layer Quantity per sq.m (m3)Unit rate (Rs.)
Cost(Rs. per sq.m.)
Subgrade 0.5 m3 375 187.53GSB 0.15 m3 1170 140.4
WMM 0.2 m3 1445 289HMA 0.14 m3 9498 1329.72
Geogrid 1 No 160 160Sum 2106.62
Miscellaneous 105.3Total 2211.9
Schedule analysisSchedule analysis
h b li h d l f hi j i• The baseline schedule of this project is analysed and the time duration for completing each activity is taken for the study (reinforced and unreinforced)
• Duration of the roadwork activities has been• Duration of the roadwork activities has been reduced drastically from the original 883 days to 669 days in case of geogrid reinforcedto 669 days in case of geogrid reinforced pavements
Summary of Resultsy
NATIONAL HIGHWAYNATIONAL HIGHWAYNATIONAL HIGHWAY NATIONAL HIGHWAY
DEVELOPMENT DEVELOPMENT
PROJECTPROJECT
Conclusions• The geocell layer increases the structural stiffness• The geocell layer increases the structural stiffness• Thickness of granular layers reduces by as much as
50%50%. • Total cost of the pavement system per unit area is lower
even with the use of expensive geocell layereven with the use of expensive geocell layer.• The long term performance and service life are
increasedincreased• Geocell layer near the surface leads to be best
fperformance.• In case of extremely soft subgrades, additional geocell
l ld b l d t b d l llayer could be placed at subgrade level.• The reduction in thickness of the base layers leads to
f t t ti d l b f t i tfaster construction and lower carbon foot print.Geocell Reinforced Flexible Pavements