Transcript Slide 1

Interactions between Geogrid and
Sand with/without Tire Chips
Including Sensitivity Analyses and
Simulations
Khurram Shehzad
st104789
14 May 2008
Geotechnical and Geoenvironmental Engineering
Contents
1.
2.
3.
4.
5.
6.
7.
Introduction
Objectives
Scope of Work
Methodology and Laboratory Test
Numerical Simulations
Sensitivity Analyses
Conclusions
Introduction
When earth structures are constructed on soft clay
deposit following problems are occurred;

Large vertical settlements

Lateral deformations
Introduction
Solution of the problems;

Mechanically Stabilized Earth (MSE) Structure

Lightweight backfill materials
Objectives

To determine the index properties of
Ayutthaya sand and tire chips-sand
mixture.

To determine the



Shear strength parameters
Interaction coefficients
Efficiency of geogrid
Objectives

To simulate the pullout and direct shear
tests results using FE software PLAXIS 2D

Sensitivity analyses of the important
parameters affecting the pullout test
Scope of Work

Laboratory Tests

Numerical Simulations
Materials for this Study
1.Ayutthaya sand
2.Tire chips-sand mixture
3.Polyfelt geogrid
Basic Concepts of MSE
Reinforcing
material
Fill material
Facing
material
Soil/Reinforcement Interaction
A= Pullout Resistance
Soil or
rigid
block
B=Direct Shear Resistance
Laboratory Tests

Direct Shear Tests

Pullout Tests
Large Scale Direct Shear Tests
Large Scale Direct Shear Tests
Large Direct Shear Apparatus
Longitudinal section
Cross section
Large Scale Direct Shear Tests
Direct shear failure envelopes of the sand and tire chips-sand mixture
without geogrid
100
140
Maximum
direct
shear
stress(kPa)
(kPa)
Maximum
direct
shear stress
Sand only
Sand only
120
80
100
Tire chips-sand
Tire chips-sand
mixturemix
Supawiwat (2002)
Prempramote (2005)
Shehzad (2008)
Shehzad (2008)
60
80
60
40
40
20
20
0
0
20
0
0
40
20
60
40
80
Normal pressure (kPa)
60
100
80
Normal pressure (kPa)
120
100
140
120
140
Large Scale Direct Shear Tests
Direct shear failure envelopes of the sand and tire chips-sand mixture
with geogrid
140
120
Tire chips-sand
mix mix
Tire chip-sand
Sand only
Sand
Maximum
directdirect
shear
stress
(kPa)
Maximum
shear
stress (kPa)
120
Prempramote (2005)
100
(Polyfelt
geogird)
Series7
Series6
(Polyfelt
geogird)
100
Shehzad (2008)
Shehzad (2008)
80
80
(Polyfelt geogird)
60
60
40
40
20
20
0
0
20
40
60
80
100
120
140
Normal pressure (kPa)
0
0
20
40
60
80
Normal pressure (kPa)
100
120
140
Pullout Tests
Pullout Tests
Pullout Apparatus
Longitudinal section
Cross section
Pullout Tests
Maximum pullout resistance versus normal stress for sand and tire
chips-sand mixture
120
Maximum pullout resistance (kN/m)
Sand
onlyOnly
Sand
Tire Tire
chips-sand
mix Mix
Chip-Sand
Supawiwat (2002)
(Hexagonal
Series7grid)
100
Shehzad (2008)
80
Prempramote (2005)
(Geogrid)
Series8
Shehzad (2008)
(Geogrid)
(Geogrid)
60
40
Slippage
failure
20
Breakage
failure
0
0
20
40
60
80
Normal stress (kPa)
100
120
140
Interaction Coefficients
Direct shear interaction coefficients between backfill materials and geogrid
Interaction Coefficients
Pullout interaction coefficients between backfill materials and geogrid
Geogrid Efficiencies
Geogrid efficiencies from pullout and direct shear tests
Prempramote (2005)
Backfill
Materials
Shehzad (2008)
Eφ
Ec
Eφ
Ec
Sand only
--
--
98.19
89.12
Tire chipssand mixture
(30:70 % by
weight)
98.06
87.10
97.37
88.01
Direct Shear Tests Simulations
Comparison of measured (R=0.98) and predicted (R=0.9) direct shear
resistance from sand backfill using PLAXIS software
140
Measured (R=0.98)
σ = 30 kPa
Direct shear stress (kPa)
120
100
FEM (R=0.9)
σ = 30 kPa
σ = 60 kPa
σ = 60 kPa
σ = 90 kPa
σ = 90 kPa
σ = 120 kPa
σ = 120 kPa
80
60
40
20
0
0
10
20
30
40
50
Direct shear displacement (mm)
60
70
80
Direct Shear Tests Simulations
Comparison of measured (R=0.95) and predicted (R=0.9) direct shear
resistance from tire chips-sand backfill using PLAXIS software
120
Measured (R=0.95) FEM (R=0.9)
Direct Shear Stress (kPa)
100
80
σ = 30 kPa
σ = 30 kPa
σ = 60 kPa
σ = 60 kPa
σ = 90 kPa
σ = 90 kPa
σ = 120 kPa
σ = 120 kPa
60
40
20
0
0
10
20
30
40
50
Diect Shear Displacement (mm)
60
70
80
Pullout Tests Simulations
Comparison of measured and predicted pullout resistance from
sand backfill
120
Pullout resistance (kN/m)
100
80
PLAXIS
σ = 30 kPa
Measured
σ = 30 kPa
σ = 60 kPa
σ = 60 kPa
σ = 90 kPa
σ = 90 kPa
σ = 120 kPa
σ = 120 kPa
R=0.7
60
40
20
0
0
10
20
30
40
50
Pullout displacement (mm)
60
70
80
Pullout Tests Simulations
Comparison of measured and predicted pullout resistance from tire
chips-sand backfill
100
PLAXIS
Pullout resistance (kN/m)
80
60
R=0.6
Measured
σ = 30 kPa
σ = 30 kPa
σ = 60 kPa
σ = 60 kPa
σ = 90 kPa
σ = 90 kPa
σ = 120 kPa
σ = 120 kPa
40
20
0
0
10
20
30
40
50
Pullout displacement (mm)
60
70
80
Pullout Tests Simulations
Comparison
Comparison of predicted pullout resistance from PLAXIS and FLAC
for sand backfill
120
Measured
Pullout resistance (kN/m)
100
80
PLAXIS (MC)
FLAC (Hypoplaticity)
σ = 30 kPa
σ = 30 kPa
σ = 30 kPa
σ = 60 kPa
σ = 60 kPa
σ = 60 kPa
σ = 90 kPa
σ = 90 kPa
σ = 90 kPa
σ = 120 kPa
σ = 120 kPa
σ = 120 kPa
60
40
20
0
0
10
20
30
40
50
Pullout displacement (mm)
60
70
80
Sensitivity Analyses
Comparison of measured and predicted pullout resistance from sand
Backfill at different R values using PLAXIS software
140
Measured
σ = 30 kPa
σ = 60 kPa
σ = 90 kPa
σ = 120 kPa
120
Pullout resistance (kN/m)
R = 0.7
σ = 30 kPa
σ = 60 kPa
σ = 90 kPa
σ = 120 kPa
100
R = 0.9
σ = 30 kPa
σ = 60 kPa
σ = 90 kPa
σ = 120 kPa
80
60
40
20
0
0
20
40
Pullout displacement (mm)
60
80
Sensitivity Analyses
Comparison of measured and predicted pullout resistance from tire
chips-sand backfill at different R values using PLAXIS software
120
Measured
Pullout resistance (kN/m)
100
80
R = 0.6
R = 0.9
σ = 30 kPa
σ = 30 kPa
σ = 30 kPa
σ = 60 kPa
σ = 60 kPa
σ = 60 kPa
σ = 90 kPa
σ = 90 kPa
σ = 90 kPa
σ = 120 kPa
σ = 120 kPa
σ = 120 kPa
60
40
20
0
0
10
20
30
40
50
Pullout displacement (mm)
60
70
80
Sensitivity Analyses
Comparison of measured and predicted pullout resistance from sand
backfill at different axial stiffness values using PLAXIS software
120
Measured
σ = 30 kPa
σ = 60 kPa
σ = 90 kPa
σ = 120 kPa
100
Pullout resistance (kN/m)
EA = 583 kN/m
80
σ = 30 kPa
σ = 60 kPa
σ = 90 kPa
σ = 120 kPa
EA = 1000 kN/m
σ = 30 kPa
σ = 60 kPa
σ = 90 kPa
σ = 120 kPa
60
40
20
0
0
10
20
30
40
50
Pullout displacement (mm)
60
70
80
Sensitivity Analyses
Comparison of measured and predicted pullout resistance from tire chipssand backfill at various axial stiffness values using PLAXIS software
120
Pullout resistance (kN/m)
100
Measured
σ = 30 kPa
EA = 583 kN/m
σ = 30 kPa
EA = 1000 kN/m
σ = 30 kPa
σ = 60 kPa
σ = 60 kPa
σ = 60 kPa
σ = 90 kPa
σ = 90 kPa
σ = 90 kPa
σ = 120 kPa
σ = 120 kPa
σ = 120 kPa
80
60
40
20
0
0
10
20
30
40
50
Pullout displacement (mm)
60
70
80
Conclusions

Weight of the MSE can be reduced by
28% using tire chips-sand mixture

Cost of MSE structure can be reduced
30% by using Tire chips mixture

Efficiency of the geogrid can be
increased by improving axial stiffness
and interaction coefficient of the geogrid