Geosynthetic Reinforced Foundations “Laboratory Model Tests & FE Analyses”
byMurad Abu-Farsakh, Ph. D., P.E.,
Qiming Chen, and Jie Gu
Louisiana Transportation Research Center
February 12, 2007
AcknowledgmentThe project is financially supported by the Louisiana Transportation Research Center and Louisiana Department of Transportation and Development (LA DOTD).
LTRC Project No. 04-2GT .
Bridge Deck Rigid Slab Pavement
Footing
Pile Group
δ
Problem StatementBridge Bump Problem
Uncomfortable rides Dangerous driving conditions Costly frequent repairs
Bridge Deck Slab Pavement
Emb Settlement
Pile Group
Bump 2
Bump 1
Bump 1
Bump 2
δB
δD
δ
θ
δs
Problem StatementReinforced Soil Foundation (RSF)
Reinforcing embankment soil directly Replacing the soils with stronger granular fill in combination with the inclusion of geosynthetics
ObjectivesInvestigate the influences of different variables and parameters contributing to the benefits of RSF,
Study the stress distribution within the soil mass for unreinforced and reinforcement conditions, and the strain distribution along the reinforcement,
Examine the existing analytical methods and/or develop new analytical/FE methods.
Design Parameters of RSF
Effective length of reinforcement (LR), Depth to top (first) reinforcement layer (u),Effective reinforcement depth (d),Number/Spacing of reinforcement layers,Type and stiffness of reinforcements,Soil-reinforcement interaction,Footing’s embedment depth.
Typical Geosynthetic RSFTypical geosynthetic RSF with the geometric parameters and a typical layout of instrumentation
BClay
Strain Gauges
Footing
h
h
u
d
h
h
203 mm203 mm203 mm
203 mm203 mm203 mml
N=3
N=2
N=1
N=5
N=4
d: Total depth of reinforcementh: Vertical spacing between layersu: Top layer spacingB: W idth of footing
N: Number of reinforcement layersPressure Cells
: Length of reinforcement
Dial gaugeLoad Cell
Geosynthetic
Research Approach
Small-Scale Lab Model TestEmbankment silty clay soilCrushed limestone Sand soil
Large-Scale Field Model TestEmbankment silty clay soil
Finite Element AnalysisEmbankment soilCrushed Limestone
Material Properties
Soils
Soil Type Dry Density (kg/m3)
Moisture Content (%)
Friction Angle (φ)
Embankment Soil
1670 18 25o – 30o
Crushed Limestone
2268 7.5 48o-53º
Sand 1620 4.8 40o-45o
Material PropertiesReinforcement
Reinforcement Polymer TypeTa, kN/m Eb, kN/m Aperture
Size, mmMDc CDd MDc CDd
GG1 geogrid Polyester 7.3 7.3 365 365 25.4×25.4GG2 geogrid Polypropylene 3.6 5.1 182 255 33×33GG3 geogrid Polypropylene 5.5 7.4 274 372 33×33GG4 geogrid Polypropylene 4.1 6.6 205 330 25×30.5GG5 geogrid Polypropylene 6.0 9.0 300 450 25×33GG6 geogrid Polypropylene 8.5 10.0 425 500 25×30.5GG7 geogrid Polypropylene 6.1 9.0 305 450 25×30.5
GT1 geotextile Polypropylene 14 19.3 700 965 ≈ 0Steel Wire Mesh Stainless Steel 236 447 11780 22360 25×51Steel Bar Mesh Steel 970 970 48480 48480 76×76
Lab Testing ProgramTests were conducted in a steel box with dimensions of 5 ft (length) × 3 ft (width) × 3 ft (height),The model footing: a steel plate with dimensions of 6 in × 6 in (B×L) ×1 in thick,Sample preparation: The soil was compacted in lifts. The lift thickness depends on the number and location of reinforcement,Compaction: three passes: 8 seconds (1st pass) → 3 seconds (2nd pass)→ 1 second (3rd pass) of vibratory jack hammer.Quality Control: Geogauge & Nuclear Density Gauge.
A Complete Test Set-up
Multiplexer
Data Logger
Load CellDial Gauge
Computer
Hydraulic Jack
Reaction Frame
Reference Beam
Lab Testing Program
Lab Testing ProgramPressure Cell
Geosynthetic
BSoil
203 mm203 mm203 mm
203 mm203 mm203 mm
Pressure Cells
102 mm
51 mm
102 mm
FootingPressure Cell
Model: Geokon Model 4800 Model: Geokon Model 4800 VW earth pressure cellsVW earth pressure cells
Diameter: 4 in.Diameter: 4 in.
Lab Testing ProgramStrain Gages
Geosynthetic
BSoil
51 mm
51 mm
51 mm
51 mm
Strain Gages
Footing
Resistance: 120±0.15%Ω
Gage Factor: 2.055±0.5%
Evaluation of ParametersThe benefits of RSF were evaluated in terms of :
Bearing Capacity Ratio (BCR) : the ratio of the bearing capacity of the reinforced soil to that of the unreinforced at a specific settlement.
Settlement Reduction Factor (SRF) : the ratio of the settlement of the reinforced soil to that of the unreinforced at a specific surface pressure.
Improvement in Vertical Stress Distribution :below reinforced zone.
Evaluation Parameters
qR, q: bearing capacity of reinforced soil and unreinforced soil at a settlement of ssR, s: settlement of reinforced soil and unreinforced soil at a surface pressure of q
s
q Rq
sR
Applied Pressure
Foot
ing
Settl
emen
t
qRq
BCR =
SRF =s Rs
Unreinforced ReinforcedSoil Soil
Test Factorial - Silty Clay
Footing Reinforcement Df/B Variable Parameter Constant Parameters
6 in × 6 in
No 0 NA NA
GG1 0u = 1, 2, 3, 4, 5, 6, 8 in. N=1
N = 1, 2, 3, 4, 5 u = 2 in., h = 2in
GG2 0 N = 1, 2, 3, 4, 5 u = 2 in., h = 2in
GG3 0N = 1, 2, 3, 4, 5 u = 2 in., h = 2in
h = 1, 2, 3, 4 in. u = 2 in., N = 3
GT1 0 N = 1, 2, 3, 4, 5 u = 2 in., h = 2in
Test Results and Analysis-Silty ClayTop Layer Spacing (u) – GG1 geogrid
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0 200 400 600 800 1000 1200
Applied Pressure ( kPa)
Sett
lem
ent R
atio
(s/B
)
NR ...GG1 25GG1 51GG1 76GG1 102GG1 127GG1 152GG1 203
Type u (mm)
(u/B)opt ≈ 0.330.33
0.90
0.95
1.00
1.05
1.10
1.15
1.20
0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40
u/B
BC
R
s/B=3%s/B=10%s/B=16%
Test Results and Analysis-Silty ClayInfluence Depth (d) – GG1 geogrid
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Applied Pressure ( kPa)
Sett
lem
ent R
atio
(s/B
) NR 0GG1 1GG1 2GG1 3GG1 4GG1 5
Type N
(d/B)cr ≈ 1.51.5
1.0
1.2
1.4
1.6
1.8
2.0
0 1 2 3 4 5
N
BC
R0.00 0.33 0.67 1.00 1.33 1.67
d/B
s/B=3%s/B=10%s/B=16%
Test Results and Analysis-Silty ClayInfluence Depth (d) – GG3 geogrid
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Applied Pressure ( kPa)
Sett
lem
ent R
atio
(s/B
) NR 0GG3 1GG3 2GG3 3GG3 4GG3 5
Type N
(d/B)cr ≈ 1.51.5
1.0
1.2
1.4
1.6
1.8
2.0
0 1 2 3 4 5
N
BCR
0.00 0.33 0.67 1.00 1.33 1.67d/B
s/B=3%s/B=10%s/B=16%
Test Results and Analysis-Silty ClayVertical Spacing (h) – GG3 geogrid
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0 200 400 600 800 1000 1200 1400 1600 1800
Applied Pressure ( kPa)
Sett
lem
ent R
atio
(s/B
)
NR ... ...GG3 51 25GG3 51 51GG3 51 76GG3 51 102
Type u h (mm)(mm)
h/Bh/B BCRBCR
1.00
1.20
1.40
1.60
1.80
0.00 0.20 0.40 0.60 0.80
h/B
BC
R
s/B=3%s/B=10%s/B=16%
Test Results and Analysis-ClaySettlement Reduction Factor
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0 100 200 300 400 500 600 700 800
q (kPa)
GG2 1 51GG2 2 51GG2 3 51GG2 4 51GG2 5 51
Type N u(h) (mm)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0 100 200 300 400 500 600 700 800
q (kPa)
SRF
GT1 1 51GT1 2 51GT1 3 51GT1 4 51GT1 5 51
Type N u(h) (mm)
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0 100 200 300 400 500 600 700 800
q (kPa)
GG3 1 51GG3 2 51GG3 3 51GG3 4 51GG3 5 51
Type N u(h) (mm)
0.00.20.40.60.8
1.01.21.41.6
0 100 200 300 400 500 600 700 800
q (kPa)
SRF
GG1 1 51GG1 2 51GG1 3 51GG1 4 51GG1 5 51
Type N u(h) (mm)
-2
0
2
4
6
8
10
12
-5 -4 -3 -2 -1 0 1 2 3 4 5
Relative Distance From the Center of Footing (x/B)
Stre
ss (k
Pa)
UNR 0 0 0GG2 51 51 5GG3 51 51 5GG1 51 51 5GT1 51 51 5
Type u h N (mm) (mm)
69% reduction
18% reduction
Stress Distribution-Silty Clay
Surface pressure, q=47 kPa
-30
0
30
60
90
120
150
-5 -4 -3 -2 -1 0 1 2 3 4 5
Relative Distance From the Center of Footing (x/B)
Stre
ss (k
Pa)
UNR 0 0 0GG2 51 51 5GG3 51 51 5GG1 51 51 5GT1 51 51 5
Type u h N (mm) (mm) 18% reduction
36% reduction
Surface pressure,q=468 kPa
Strain Along the Reinforcement-Silty Clay
-0.5
0.0
0.5
1.0
1.5
2.0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Relative Distance From the Center of Footing (x/B)
Stra
in (%
)
1%2%3%4%5%6%8%10%12%14%16%
s/B
strain gauge broken
(l/B)cr ≈ 5.0-0.5
0.0
0.5
1.0
1.5
2.0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
Relative Distance From the Center of Footing (x/B)
Stra
in (%
)
1%2%3%4%5%6%8%10%12%14%16%
s/B
At a depth of 1/3B
At a depth of 5/3B
Finite Element Analysis
00.5
11.5
22.5
33.5
44.5
5
0 100 200 300 400 500 600 700 800 900 1000
Footing Pressure (psi)
Foot
ing
Sett
lem
ent (
inch
) 0
20
40
60
80
100
120
0 1000 2000 3000 4000 5000 6000
(kPa)
(mm
)
3 layer reinforced soil4 layer reinforced soil6 layer reinforced soil8 layer reinforced soil12 layer reinforced soil
Typical pressure-settlement Curve (Type III geogrid)
Finite Element Model
Finite Element - Results
Optimum depth of first reinforced layer
0.00.20.40.60.81.01.21.41.61.82.0
0.0 0.2 0.4 0.6 0.8 1.0
Depth ratio (u/B)
Bea
ring
Cap
acity
Rat
i
Three-layer reinforced soil
Two-layer reinforced soil
One-layer reinforced soil
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
0 1 2 3 4 5 6 7 8 9 10
Number of Geogrid Layers
BC
R a
t s/B
=10%
0 0.5 1 1.5 2 2.5Reinforcing Depth Ratio, D/B
Type VIII GeogridType VI GeogridType III Geogrid
Influence depthof reinforced zone
Finite Element - Results
Effect of reinforcement Stiffness
0
0.02
0.04
0.06
0.08
0.1
0.12
0 0.5 1 1.5 2 2.5 3 3.5 4
Normalized Geogrid Stiffness
Settl
emen
t Rat
io, s
/B
3-layer reinforced soil4-layer reinforced soil6-layer reinforced soil8-layer reinforced soil12 layer reinforced soil
0.8
1
1.2
1.4
1.6
1.8
2
2.2
2.4
0 0.5 1 1.5 2 2.5 3 3.5 4
Normalized Geogrid Stiffness
Bea
ring
Cap
acity
Rat
io a
t s/B
=10%
3-layer reinforced soil4-layer reinforced soil6-layer reinforced soil8-layer-reinforced soil12-layer reinforced soil
Finite Element – Regression Model
BCR = 1.7761- 2.0237*X1 + 0.12367*X2 + 0.56264*X3 - 0.01889*X4 - 0.08193*X5
(R2=0.98)
Where: BCR: bearing capacity ratio of the reinforced soil (at s/B=10),X1: is the spacing ratio between geogrid layers (h/B),X2: is the stiffness ratio of reinforcement included in the reinforced soil
(i.e. Ereinforcement/Esoil),X3: is the interaction coefficient between reinforcement layers and soil,X4: is the footing embedment ratio (D/B), X5: is the footing width ratio (B/4ft).
Verification of BCR Regression Model
h (in) X1
Egeogrid
(psi) X2 CI
* X3Df
(in) X4
B (in) X5
BCR (Fem)
BCR (Reg)
Abs (Err) (%)
12 0.25 43850 1.16 0.5 0.5 0.0 0.00 4.0 1.0 1.62 1.61 0.16 12 0.25 43850 1.16 0.7 0.7 0.0 0.00 4.0 1.0 1.69 1.73 2.13 12 0.25 91280 2.42 0.5 0.5 0.0 0.00 4.0 1.0 1.78 1.77 0.48 12 0.25 131800 3.50 0.7 0.7 0.0 0.00 4.0 1.0 1.99 2.01 1.01 24 0.50 54620 1.45 0.7 0.7 0.0 0.00 4.0 1.0 1.32 1.26 4.79 24 0.50 102100 2.71 0.7 0.7 0.0 0.00 4.0 1.0 1.45 1.41 2.98 12 0.25 102100 2.71 0.7 0.7 0.0 0.00 4.0 1.0 1.84 1.92 4.22 6 0.13 54620 1.45 0.7 0.7 0.0 0.00 4.0 1.0 2.05 2.01 1.62 6 0.13 102100 2.71 0.7 0.7 0.0 0.00 4.0 1.0 2.23 2.17 2.63 18 0.38 43850 1.16 0.7 0.7 0.0 0.00 4.0 1.0 1.50 1.47 1.80
Developed Plastic Zones
In unreinforced soil In 3-layers geogrid reinforced soil
Test Factorial-Crushed Limestone
Footing Reinforcement Df/B Variable Parameter Constant Parameters
6 in × 6 in
No 0 NA NA
GG1 0 N = 1, 2, 3 u = 2 in., h = 2in
GG4 0 N = 1, 2, 3 u = 2 in., h = 2in
GG5 0 N = 1, 2, 3 u = 2 in., h = 2in
GG6 0 N = 1, 2, 3 u = 2 in., h = 2in
GG7 0 N = 1, 2, 3 u = 2 in., h = 2in
SWM 0 N = 1, 2, 3 u = 2 in., h = 2in
SBM 0 N = 1, 2, 3 u = 2 in., h = 2in
Test Results and Analysis-Crushed Limestone
Type and Stiffness of Reinforcement-One Layer
0.00
0.04
0.08
0.12
0.16
0.20
0.24
0.28
0 2000 4000 6000 8000 10000 12000
Applied Pressure ( kPa)
Sett
lem
ent R
atio
(s/B
)
Unreinforced ... ...GG4 1 51GG1 1 51GG5 1 51GG7 1 51GG6 1 51SWM 1 51SBM 1 51
Type N u (mm)
Stiffness Stiffness increaseincrease
0.0
0.5
1.0
1.5
2.0
2.5
GG4 GG1 GG5 GG7 GG6 SWM SBM
Stiffness
BC
R
1 51 ...2 51 513 51 51
N u h (mm)(mm)
Test Results and Analysis-Crushed LimestoneNumber of Layers and Stiffness of Reinforcement
StiffnessStiffness BCRBCR0.0
0.5
1.0
1.5
2.0
2.5
3.0
GG4 GG1 GG5 GG7 GG6 SWM SBM
Stiffness
BC
R
1 51 ...2 51 513 51 51
N u h (mm)(mm)
s/B=3%
s/B=10%
0.0
0.2
0.4
0.6
0.8
1.0
0 1000 2000 3000 4000 5000 6000
q (kPa)
SRF
GG4 3 51 51GG1 3 51 51GG5 3 51 51GG7 3 51 51GG6 3 51 51SWM 3 51 51SBM 3 51 51
Type N u h (mm)(mm)
Test Results and Analysis-Crushed LimestoneSettlement Reduction
0.0
0.2
0.4
0.6
0.8
1.0
0 1000 2000 3000 4000 5000 6000
q(kPa)
SRF
GG4 2 51 51GG1 2 51 51GG5 2 51 51GG7 2 51 51GG6 2 51 51SWM 2 51 51SBM 2 51 51
Type N u h (mm)(mm)
0.0
0.2
0.4
0.6
0.8
1.0
0 1000 2000 3000 4000 5000 6000
q(kPa)
SRF
GG4 1 51GG1 1 51GG5 1 51GG7 1 51GG6 1 51SWM 1 51SBM 1 51
Type N u (mm)
Finite Element - Results
Optimum depth of first reinforced layer
Typical pressure-settlement curve
0
0.05
0.1
0.15
0.2
0.25
0 500 1000 1500 2000
Footing Pressure (psi)
Foot
ing
Settl
emen
t (B
)
0 1000 2000 3000 4000 5000 6000 7000 8000Footing Pressure (kPa)
unreinforced soil3-layer reinforced soil4-layer reinforced soil6-layer reinforced soil12-layer reinforced soil
11.051.1
1.151.2
1.251.3
1.351.4
1.451.5
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1
Top Layer Spacing (B)
BC
R
1-layer reinforced soil2-layer reinforced soil3-layer reinforced soil
Finite Element - Results
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
0 1 2 3 4 5 6
Normalized Stiffness
BC
R a
t s/B
=10%
12-layer reinforced soil6-layer reinforced soil3-layer reinforced soil
0
0.2
0.4
0.6
0.8
1
0 1 2 3 4 5 6
Normalized Stiffness
SR
F at
Fin
al S
tate
of
Unr
einf
orce
d S
oil
12-layer reinforced soil6-layer reinforced soil3-layer reinforced soil
0
100
200
300
400
500
600
0 1 2 3 4 5 6 7 8
Distance from Central Axis along the horizontal line 1.5 B below footing (B)
Vert
ical
Stre
ss D
evel
oped
at f
inal
sta
te
of u
nrei
nfor
ced
soil
(psi
)
0
500
1000
1500
2000
2500
3000
3500
4000(k
Pa)unreinforced
3-layer SW reinforced soil6-layer SW reinforced soilunre asso
0
100
200
300
400
500
600
0 1 2 3 4 5 6 7 8
Distance from Central Axis along the horizontal line 1.5 B below footing (B)
Vert
ical
Stre
ss D
evel
oped
at f
inal
sta
te
of u
nrei
nfor
ced
soil
(psi
)
0
500
1000
1500
2000
2500
3000
3500
4000
(kP
a)unreinforced3-layer SW reinforced soil6-layer SW reinforced soilunre asso
Finite Element – Regression Model
BCR = 1.84917-0.29706*X1 + 0.03031*X2 -0.2015*X3 - 0.34724*X4
(R2=0.98)
Where: BCR: is the ultimate bearing capacity ratio of the reinforced soil (at
s/B=10),X1: is the spacing ratio between geogrid layers (h/B),X2: is the normalized stiffness of reinforcement included in the
reinforced soil ,X3: is the footing embedment ratio (D/B), X4: is the footing width ratio (B/4ft).
Verification of BCR Regression Model
No.X1 X2 X3 X4 BCR
(Fem)BCR
(Reg)Abs (Err)
(%)
1 0.375 0.4 0.0 1.0 1.69 1.73 2.13
2 0.375 1.77 0.0 1.0 1.99 2.01 1.01
3 0.375 0.59 0.5 1.0 1.84 1.92 4.22
4 0.375 0.59 1.0 1.0 2.23 2.17 2.63
5 0.375 0.59 0.0 0.75 1.50 1.47 1.80
6 0.375 0.59 0.0 1.5 1.63 1.63 0.20
7 0.1875 0.80 0.0 1.0 1.47 1.47 0.23
8 0.1875 3.54 0.0 1.0 1.56 1.55 0.22
9 0.1875 1.18 0.5 1.0 1.37 1.38 0.52
10 0.1875 1.18 1.0 1.0 1.28 1.28 0.09
11 0.1875 1.18 0.0 0.75 1.62 1.57 3.27
12 0.1875 1.18 0.0 1.5 1.32 1.31 0.99
Large-Scale Testing ProgramTest dimensions: 3.658 m (12 ft) (length) × 3.658 m (12 ft) (width) × 1.829 m (6 ft) (height),The model footing: a concrete block with dimensions of 452 mm (1.5 ft) × 452 mm (1.5 ft) (B×L) ×254 mm thick,Section preparation: a tiller was used to mix the cohesive soil and water. The soil was compacted in lifts. The lift thickness depends on the number and location of reinforcement,Compaction: MultiQuip Plate Compactor → three passes
Wacker-packer → six passes
Test Factorial
Reinforcement Type
No. of Reinforcement
Layers
umm
h mm
Unreinforced* - … ...
GG2 4 152 203
GG3 3 152 305
GG3 4 152 203
GG3 5 152 152
GG4 4 152 203
Test Results and Analysis
0.00
0.05
0.10
0.15
0.20
0.25
0 500 1000 1500 2000
Applied Pressure ( kPa)
Sett
lem
ent R
atio
(s/B
)
Unreinforced ... ... ...GG2 152 203 4GG3 152 305 3GG3 152 203 4GG3 152 152 5GG4 152 203 4
Type u h N (mm) (mm)
1.0
1.1
1.2
1.3
1.4
1.5
GG2 GG3 GG4
Stiffness
BC
R
s/B=3%s/B=5%s/B=8%
N= 4, u= 152 mm, h= 203 mm
1.0
1.1
1.2
1.3
1.4
1.5
s/B=3% s/B=5% s/B=8%
BC
R
3 152 3054 152 2035 152 152
N u h (mm) (mm)
Analytical Solution – Silty ClayThe following failure mode would occur in reinforced soil foundation (Wayne, et al., 1998)
BFooting
Reinforcementd
qbT
After Deformation
ca ca
ccaa, , φφaa, , γγaa
ccbb, , φφbb, , γγbb
dBLTLB
BLLBK
dDd
BLdLBcqq a
as
faabult γ
φγ −+++⎥⎦
⎤⎢⎣⎡ ++++= )(2tan)(21)(2 2
Analytical Solution – Silty ClayBased on Meyerhof and Hanna’s solution for two layer soil system, Wayne, et al. (1998) proposed:
dBLTLB
BLLBK
dDd
BLdLBcqq a
as
faabult γ
φγ −+++⎥⎦
⎤⎢⎣⎡ ++++= )(2tan)(21)(2 2
qqbb = ultimate bearing capacity of the foundation below the = ultimate bearing capacity of the foundation below the reinforced zone;reinforced zone;
B = width of the footing; L = length of the footing;B = width of the footing; L = length of the footing;d = total depth of reinforcement; Dd = total depth of reinforcement; Dff = embedment depth of the = embedment depth of the
footing;footing;KKss= punch shear coefficient, which depends on friction angle of= punch shear coefficient, which depends on friction angle of
upper layer soil and the ultimate bearing capacity of botupper layer soil and the ultimate bearing capacity of bothhupper and lower soil layers;upper and lower soil layers;
T = uplift or restraining force of the reinforcements.T = uplift or restraining force of the reinforcements.
Measured Vs. Calculated – Silty Clay
GG1 Geogrid
1.0
1.2
1.4
1.6
1.8
2.0
0 1 2 3 4 5
N
BC
R
Measured, BCR@s/B=10% (GG1)Calculated (Wayne, et al., 1998)Finite Element Analysis
1.0
1.2
1.4
1.6
1.8
2.0
0 1 2 3 4 5
N
BC
RMeasured, BCR@s/B=10% (GG3)Calculated (Wayne, et al., 1998)Finite Element Analysis
GG3 Geogrid
Summary and ConclusionsThe optimum depth of the top reinforcement layer was found to be 0.3B - 0.35B,The bearing capacity increases with increasing the number of reinforcement layers within the influence zone. The influence depth of the reinforced zone was found to be ≈1.5 B,The effective length of reinforcement was found to be ≈5 B, Geogrids with higher stiffness performed better than geogrids with lower stiffness,The bearing capacity increases with the increase in reinforcement stiffness and with the decrease in the vertical spacing of reinforcement layers,
Summary and ConclusionsImmediate settlement can be reduced significantly with soil reinforcement. It decreases with the increase in reinforcement stiffness and with the decrease in reinforcement spacing,The inclusion of reinforcement improves the vertical stresses distribution below the influenced depth. This will be resulted in reducing the soil’s consolidation settlement,Regression models were developed from FE results, and were verified,The analytical solution proposed by Wayne, et al. (1998) and the finite element analysis are in good agreement with the experimental test results.
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