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grouting
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Numerical modeling of laterally loaded pile groups in soft clay improved by jet
grouting
Cheng Lin The University of Kansas Jie Han The University of Kansas Shuilong Shen Shanghai JiaoTong University Zhenshun Hong Southeast University
Introduction
Outline of Presentation
Numerical modeling
Results and discussion
Conclusions
Introduction Why is jet grouting considered to improve lateral capacity?
Insufficient lateral capacity of pile group
Scour occurs at bridge pile foundation
Tighter design code
Solutions
Structural retrofit
Jet grouting
Introduction Why is jet grouting considered to improve lateral capacity?
Insufficient lateral capacity of pile group
Scour occurs at bridge pile foundation
Tighter design code
Solutions
Structural retrofit
Jet grouting
Costly, requiring additional piles and mobilization cost
Cost-effective in soft clay
(Rollins et al. 2003)
Introduction
What is the objective of this study?
Perform a numerical simulation of laterally loaded pile group test in soft clay
before improved by jet grouting
after improved by jet grouting
Overall goal
Parametric study
Improving mechanism due to jet grouting
Numerical modeling
2.84 m
2.75 m13.4 m
0.9 m
0.55 m
0.76 m
CorbelFt
3.0 m
0.9 m0.9 m4.57 m
3.2 m
Jet grouted zone
Test pile
(Adsero 2008) FLAC3D
Mohr-Coulomb model
Numerical modeling
Diameter, D (m)
Thickness, t (m)
Length, L (m)
Moment of inertia, I (m4)
Young’s modulus, E (kN/m2)
Poisson’s ratio,
p
Pipe pile 0.324 0.009 13.4 (1.42x10-4)a 2.0x108 0.3Concrete 0.306 13.4 (4.30 x10-4)b 2.1 x107
Equivalentpile 0.324 13.4 (5.41x10-4)c 6.9x107 0.3
Parameters of test piles
_ int( ) /p eq p A c outE E I E I IEquivalent pile modulus
Note: a, b, and c are the values of IA, Iint, and Iout
(Adsero 2008)
Pile properties
Numerical modeling
Properties of soilModel 1
Depth measured
from top ofpile cap (m)
Undrainedshear
strength, Cu (kPa)
Unit weight,’(kN/m3)
Young’s modulus,Es (kPa)
Poisson’s ratio,
p
Plasticity Index,PI (%)
0-0.76 50 18.4 600Cu 0.45 20.50.76-3 15.5 17.5 200Cu 0.45 233-10 30 17.5 400Cu 0.45 13
10-18.2 50 17.5 600Cu 0.45 21.3
Es is cited from Poulos and Davis (1980)
(Adsero 2008)
Soil properties
Model 2 150 us
CEPI
(Adsero 2008)
Numerical modeling
EG = 3,175 MPa qu (Taki and Yang 1989)
Grouted soil properties
G = 0.3
Results and discussion
0
500
1000
1500
2000
2500
3000
0 10 20 30 40 50 60
Late
ral l
oad
at p
ile c
ap (k
N)
Lateral displacement at pile cap (mm)
Improved (Field)
Improved (Model 1)
Improved (Model 2)
Results and discussion
0
500
1000
1500
2000
2500
-5 15 35 55
Lat
eral
load
at p
ile c
ap (k
N)
Lateral displacement at pile cap (mm)
Natural (Field)Natural (Model)Improved (Field)Improved (Model)
Results and discussion
-16
-14
-12
-10
-8
-6
-4
-2
0
-100 -50 0 50 100 150 200 250
Dep
th (m
)
Shear force (kN)
Improved (Model)Natural (Model)
Load
At the same lateral displacement of pile cap: 38 mm With lateral load at pile cap: 1300 kN (natural); 2200 kN (improved)
Results and discussion
-16
-14
-12
-10
-8
-6
-4
-2
0
-100 -50 0 50 100 150
Dep
th (m
)
Bending moment (kN-m)
Improved (Model)
Improved (Field)
Natural (Model)
Load
Conclusions
(1) The soil moduli based on 200 to 600 times soil undrained shear strengths yielded reasonable results
(2) The numerical results showed that jet grouting around piles in the group significantly increased the lateral resistance
(4) A further study is needed to investigate the reasons for the difference in the magnitudes of the bending moments.
(3) Distributions of lateral pile responses (i.e. shear forces and bending moments) before and after jet grouting below the certain depth were almost the same.
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