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Evaluation of Liquefaction Risk of Reinforced Soil with Stone 
Column 
 
Z. Ben Salem 
Email:zeineb.bensalem@gmail.com 
 
W. Frikha 
Email:wissem.frikha@enit.rnu.tn 
 
M. Bouassida 
Email:mounir.bouassida@enit.rnu.tn 
 
Research Team Geotechnical Engineering. Ecole Nationale d'Ingénieurs de Tunis, URIG, ENIT, BP 37, LE 
BELVEDERE 1002 TUNIS, TUNISIA 
 
SUMMARY: 
 
Stone column is a ground improvement technique employed to increase bearing capacity and to 
reduce settlements of soils. Installation of stone column is the most widely adopted technique as a 
liquefaction countermeasure (Mitchell and Wentz, 1991).Installation of stone column mitigate the 
potential for liquefaction by increasing the density of the surrounding soil, providing drainage and 
reducing the stress levels in the initial soil. Several approaches have been developed to estimate the 
potential risk of liquefaction from in-situ and laboratory tests results. Several case histories from 
different literatures of reinforced effect of stone column installation were treated. In these cases, 
Standard Penetration Test (SPT) and Cone Penetration Test (CPT) were performed before and after 
stone column installation. In the present paper, the effectiveness of stone columns technique as a 
liquefaction countermeasure is quantified and design recommendations for the improved effect of 
stone column installation in liquefiable soils are presented. 
 
KEYWORDS: Liquefaction, stone column installation, improvement. 
 
 
1 INTRODUCTION 
 
Liquefaction is the most hazardous damage 
during an earthquake. Liquefaction damage 
induced sand boils, excessive settlement, lateral 
spread, landslides and slope failure, loss of 
bearing capacity, etc. 
 Seed and Idriss (1971) developed and 
published the basic "simplified procedure" for 
liquefaction evaluation which involves 
comparing the Cyclic Shear Stress Ratio (CSR) 
caused by the design earthquake with the 
capacity of the soil to resist liquefaction 
expressed in terms of Cyclic Resistance Ratio 
(CRR). The simplified procedure was developed 
from empirical evaluations of field observations 
and field and laboratory test data. This 
procedure has been modified and improved 
based on in situ tests, such as those developed 
by Seed (1979) ,Seed and Idriss (1982) , Seed 
et al. (1985) ,Youd and Idriss (1997), Youd et 
al. (2001), Cetin et al. (2004), Idriss and 
Boulanger (2008). 
 To reduce the potential risk of liquefaction, 
various ground improvement methods are used 
including densification, reinforcing, 
grouting/mixing and drainage. Installation of 
granular columns like gravel drains, granular 
piles and stone columns is the most widely 
adopted method for liquefaction mitigation 
(Mitchell and Wentz, 1991). Adalier and 
Elgamal (2004) reviewed the current state of the 
stone column method as a liquefaction 
countermeasure. In fact, installation of stone 
column by vibro replacement provides drainage 
by reducing excess pore pressures generated by 
 
cyclic loading and by accelerating its 
dissipation (Baez 1995; Priebe,1991;Mitchell et 
al. 1995) and increases the density of the 
surrounding soil which increase the Cyclic 
Resistance Ratio (CRR). The introduction of 
stiffer material (stone) can potentially carry 
higher stress levels and thereby reduce stresses 
in the liquefiable soil (Priebe,1991). 
Consequently, Cyclic Shear Stress Ratio CSR is 
reduced. 
 The present paper examines the effectiveness 
of stone column installation in reducing the 
liquefaction potential. Several case studies 
based on stone column reinforcement project 
are considered, where SPT and CPT tests were 
performed before and after stone column 
installation. The CRR is then evaluated based 
on theses in-situ test results using Idriss and 
Boulanger (2008) procedure. The CSR 
reduction is estimated using several approaches 
developed by Priebe (1998), Baez and Martin 
(1993) and Goughnour and Pestana (1998). 
 
2 SIMPLIFIED PROCEDURE FOR 
LIQUEFACTION EVALUATION 
 
 Seed and Idriss (1971) proposed a "simplified 
procedure" for liquefaction evaluation based on 
empirical evaluations of field observations and 
field and laboratory test data. Seed and Idriss 
procedure involves comparing the Cyclic Shear 
stress Ratio (CSR) caused by the design 
earthquake with the capacity of the soil to resist 
liquefaction expressed in terms of Cyclic 
Resistance Ratio (CRR). The factor of 
safety (FS) against liquefaction is defined as 
follows: 
 
CSR
CRR
FS 
 (1) 
Hypothetically, a FS less than 1.0 suggests that 
the soil is susceptible to initiation of 
liquefaction. 
Seed and Idriss (1971) formulated the following 
equation to estimate CSR induced by 
earthquake ground motions, at a depth z below 
the ground surface: 















g
a
..r.65,0CSR max
'
v
v
d'
0v
ave




 (2) 
 
Where: amax is the peak horizontal acceleration 
at ground surface generated by the earthquake, 
g is the acceleration of gravity, 
v
and 
v
'
 are 
total and effective vertical overburden stresses 
respectively and rd is the shear stress reduction 
factor evaluated using Idriss and Boulanger 
(2008) recommendation. 
 Empirical methods based on measurements of 
in situ soil strength and observations of field 
performance in previous earthquakes have been 
developed to predict soil liquefaction resistance 
expressed by the Cyclic Resistance Ratio 
(CRR): 
 
atm1,5.7MCRR.K.MSFCRR  
 (3) 
 
Where CRRM=7.5,1atm is the cyclic resistance 
ratio of the soil adjusted to 1 atmosphere of 
effective overburden pressure for the 
earthquake magnitude M=7.5, MSF is the 
Magnitude Scaling Factor for earthquakes of 
magnitude other than 7.5 and Kσ is the 
overburden correction factor for the overburden 
stresses at the depth of interest. 
 In the present paper, a focus is made on Idriss 
and Boulanger (2008) procedure for evaluating 
soil liquefaction resistance based on SPT and 
CPT results. Idriss and Boulanger (2008) 
recommended a correlation between the 
CRRM=7.5,1 atm and the SPT and CPT penetration 
resistance , respectively, via the following 
expressions: 
 











































8.2
4.25
N
6.23
N
126
N
1.14
N
expCRR
4
cs,60,1
3
cs,60,1
2
cs,60,1cs,60,1
atm1,5.7M
 (4) 
 



































3
114
q
80
q
67
q
540
q
expCRR
4
Ncs1c
3
Ncs1c
2
Ncs1cNcs1c
atm1,5.7M
 
 
 (5) 
 
Where N1,60,cs is the corrected blow count 
adjusted to a clean sand equivalent and qc1Ncs is 
the equivalent clean-sand value of the corrected 
tip resistance. 
 
3 ANALYSIS OF LIQUEFACTION 
POTENTIAL OF PRE- AND POST- STONE 
COLUMN INSTALLATION 
 
 Stone columns installation is commonly 
adopted for liquefaction mitigation and has 
proven its effectiveness in many instances 
(Mitchell and Wentz, 1991).Stone columns help 
to mitigate liquefaction through one or more of 
these ways(Baez 1995 ; Adalier and 
Elgamal,2004): i) the installation process of 
stone columns densifies the surrounding soil, 
which increases the liquefaction resistance 
(CRR), ii) the stone columns act as drains due to 
higher permeability than the liquefiable soil and 
allow the rapid dissipation of excess pore water 
pressure from the soil and iii) the stone columns 
act as reinforcing elements due to higher 
stiffness than the surrounding soil. The stone 
columns can potentially carry higher stress 
levels and thereby reduce stresses in the 
liquefiable soil. Consequently, Cyclic Shear 
Stress Ratio CSR is reduced. 
 In the present paper, to study the effectiveness 
of stone column for liquefaction mitigation, a 
focus is made on the prediction of : i)the shear 
stress reduction (CSR) and ii) the increase of 
liquefaction resistance (CRR) using SPT and 
CPT tests performed before and after stone 
column installation. 
 
3.1 Evaluation of Shear Stress Reduction 
 
The CSRsc reduction is estimated, after stone 
column installation, using several approaches 
developed by Priebe (1998), Baez and Martin 
(1993) and Goughnour and Pestana (1998). The 
shear stress reduction factor denoted KG is 
defined as: 
 
CSR
CSR
K scG 
 (6) 
 
 Where CSR is calculated Seed and Idriss 
(1971) approach. 
 Baez and Martin (1993) and Priebe (1998) 
considered that both the soil and the columns 
respond as shear beams, with the distribution of 
the seismically induced stress computed 
accordingly. The shear stress reduction factor 
KG proposed by Priebe (1998) is as following: 
 
0
G
n
1
K 
 (7) 














 1
)1).(
2
45(tan
1
1n
c2
0


 (8) 
 
Where n0 is the ground improvement factor for 
vibro-replacement which depends on the area 
replacement ratio
A
Asc
which is the ratio of 
stone column area Asc to the tributary area A, 
and on the friction angle φc of the column 
material. 
 Baez and Martin (1993) proposed the 
expression of shear stress reduction factor KG as 
following : 
 
)1G(1
1
K
r
G



 (9) 
 
Where 
G
G
G scr 
 is the ratio of the stone 
column’s shear modulus Gsc to the shear 
modulus of the soil G. 
 Goughnour and Pestana (1998) included the 
effect of flexural response to the large slender 
ratio of stone columns. They assumed that the 
soil responds as a shear beam while the 
columns respond as flexural beams. If so, this 
implies that little to no additional shear stress is 
carried by the columns. The shear stress 
reduction factor KG proposed by Goughnour 
and Pestana (1998) is: 
 
)1G.(1
)1n.(1
K
r
G





 (10) 
 
Where: n is the vertical stress ratio defined as 
the ratio of vertical effective stress within the 
stone to that in the in situ soil and can be 
calculated as following (Barksdale and 
Bachus,1989) : 
 
 
s
sc
r
21
1
21
1
Gn





















 (11) 
 
Where ν is Poisson’s ratio. 
 Figure 1 provides a comparison in CSR 
reduction using Priebe (1998), Baez and Martin 
(1993), Goughnour and Pestana(1998) 
approaches. Typical values of material 
parameters are adopted, namely Gr equal to 10, 
η equal to 0.2 and φc of the column material 
equal to 35° and Poisson’s ratio ν of initial soil 
and column material equal to 0.3 and 0.2 
respectively. This figure shows that Baez and 
Martin (1993) approach provides the greatest 
amount of CSR reduction . However, 
Goughnour and Pestana (1998) approach gives 
little CSR reduction. For example, when initial 
CSR calculated with Seed and Idriss (1971) 
approach is equal to 0.3, after shear stress 
reduction CSRsc becomes equal to 0.10, 0.17 
and 0.24 using Baez and Martin (1993), Priebe 
(1998) and Goughnour and Pestana (1998), 
respectively. 
 Finite element analyses were performed by 
Olgun and Martin (2008) and Green et al. 
(2008) to better understand column deformation 
and shear stress reduction behavior. The 
combined flexural and shear behavior of the 
column was confirmed. Experimental tests are 
of considerable interest to predict shear stress 
distribution behavior of stone columns. 
 
 
 
Figure1.Reduced CSR after stone column reinforcement 
 
3.2 Analysis of Pre- and Post- Liquefaction 
Potential using SPT and CPT Correlations 
 
 In order to study the liquefaction potential of 
reinforced soil with stone column, several case 
studies based on stone column reinforcement 
project are considered. Site investigation 
consisted of in situ testing including SPT and 
CPT tests performed before and after stone 
column installation. Table 1 provides a 
summary of these case studies where different 
design parameters of stone column. An 
earthquake magnitude of 7 and a maximum 
ground surface acceleration of amax=0.20 g are 
used in liquefaction analyses and liquefiable 
layers soils properties were given. 
 Comparative results of N1,60,cs and qc1N,cs 
before and after stone column installation were 
reported in figures 2 and 3 respectively. A 
significant increase in penetration resistance 
was observed after stone column installation, 
which confirmed the densification effect and 
reach in some cases more than five times the 
initial resistance. For these different case 
studies, varied degrees of densification were 
observed. In fact, the degree of resulting 
densification is a function of soil type, fines 
content, soil plasticity, pre-densification relative 
density, vibrator type, stone shape and 
durability, stone column area, and spacing 
between stone columns (Adalier and Elgamal 
2004). Such measurable densification increased 
the liquefaction resistance. 
 
 
 
Figure 2. Pre and Post reinforcement corrected 
N1,60,csvalues 
 
 
Table 1.Cases studies of stone column reinforcement 
Project Soil Site 
GWT 
depth 
(m) 
Treat. 
depth 
(m) 
Grid 
Space. 
(m) 
Diam 
(m) 
η 
(%) 
Source 
Christchurch,New 
Zealand 
Loose to 
medium dense 
sandy 
and silty-sand 
1.5 to 
1.8 
10.5 Triangular .1.65 0.6 12 
Mahoney and 
Kupec(2014) 
Hinckley 
Drive ,Utah, USA. 
Interbedded silts 
and sands 
~2.8 
12.2 
to 
13.7 
Triangular 2.44 0.91 14 Rollins et al.(2012) 
Debottlenecking 
project , 
New Delhi,India 
Silty Fine 
Sand–Silty Clay 
deposits 
2.8 7 to 8 Triangular 
1.8 to 
2.5 
0.8 to 
0.85 
25 
Basarkar et al. 
(2009) 
Shepard lane, 
Farmington,Utah 
Silty sand and 
sandy silt 
- 7.5 Triangular 2 1.1 27 Rollins et al.(2006) 
Marina Del Rey, 
CA 
Inter-bedded 
silty soil 
~2 - - 2.4 0.9 11 Shenthan (2005) 
Webster Street 
Tube, California, 
USA 
Loose fine sand ~0 15 Triangular 2.4 0.57 ~16 
Lee et al. (2005) 
 
Earth embankment 
project,western 
Washington 
Silty sand ~2.25 
5.1 
to 5.7 
Triangular 2.4 1 17 
Chen and Bailey 
(2004) 
Full-scale lateral 
load tests, 
California. 
Loose sand 1.5 
 
Square 2.4 
0.9 
 
11 
Weaver et al. 
(2004) 
 
Steel oil storage 
tanks,Georgia. 
Silty sand 1.5 15 Square 
2.2 
to2.5 
1 
12.5
-
16.5 
Duzceer(2003) 
East Anglia trial 
 
Clayey sand ~0 - - 
1.5 and 
2.1 
0.9 - 
Slocombe et al. 
(2000) 
Borcelik Gemlik 
Cold Steel Rolling 
Mill,Turkey 
Loose medium 
dense sand 
~0 12 Triangular 1.5 0.5 10 
Durgunoglu,et 
al.,(1995) 
Oxnard, California 
Silty and sandy 
alluvium 
2.74 6 Square 2.74 0.9 ~10 
Blanchard and 
Clements (1993) 
Monterey Sports 
Center in Monterey, 
CA 
- - - - 
1.8, 2.4 
and 3 
- - 
Baez and Martin 
(1992) 
Port of zarzis, 
Tunisia 
Very loose silty 
sand 
0.8 to 
1 
6.5 Triangular 2 1.2 33.3 Gambin. (1992) 
Steel Creek Dam 
California, USA 
Slightly clayey 
sand 
- - Triangular 1.8 0.9 22.6 Keller et al. (1987) 
 
 
 
Figure 3.Pre and Post reinforcement qc1N,cs values 
 
 The CRR profiles were then calculated based 
on N1,60,cs and qc1N,cs values deduced from 
measured values before and after stone column 
installation. Figure 4 and 5 show CRR plotted 
as a function of N1,60,cs and qc1N,cs respectively. 
The obtained results indicate that stone column 
reinforcement increase significantly the CRR. 
In fact, the increase in the degree of soil 
densification leads to an increase of the cyclic 
liquefaction resistance. 
 
 
 
Figure 4.Pre- and Post reinforcement CRR values based 
on SPT-correlations 
 
 
 
 
Figure 5.Pre- and Post reinforcement CRR values based 
on CPT-correlations 
 
 The CSR at each site was calculated and then 
adjusted for the reference values of M=7.5 and 
'
v
=1atm as: 
 
K
1
.
MSF
1
.CSRCSR* 
 (12) 
 
 The resulting CSR* values were plotted 
against the values of N1,60,cs and q c1N,cs in Figure 
6 and Figure 7 respectively with the boundary 
curve (i.e CRR adjusted to M=7.5 and 
'
v
=1atm). From these figures, it was observed a 
significant increase of N1,60,cs and q C1N,cs values 
after stone column installation. These figures 
show that the majority of data points recorded 
before reinforcement were located to the left of 
the boundary curve and are classified as 
liquefiable soils. After stone column 
installation, the data points were, mainly, found 
on the right of the boundary curve where no 
liquefaction occurs. It should be noted that in 
some cases, before stone column, potential risk 
of liquefaction was not considerable, however 
after reinforcement, it decreases. It is also noted 
from figure 7 in some data points that potential 
liquefaction using CPT test still remains after 
reinforcement. 
 
 
 
 
 
Figure 6.Relationship between CSR* and N1,60,cs 
 
 
 
Figure7.Relationship between CSR* and qc1N,cs 
 
 Figure 8 and 9 illustrate a comparison of 
safety factor calculated before and after stone 
column reinforcement based on SPT and CPT 
results, respectively. After stone column 
installation, the most of FS values are greater 
than 1.0 which indicate that no liquefaction 
occurs in the improved soil under the design 
seismic loading. 
 
Figure 8.FS before and after stone column reinforcement 
based on SPT-correlations 
 
 
Figure 9.FS before and after stone column reinforcement 
based on CPT 
 In order to study the effect of shear stress 
reduction, the CSRsc at each site is calculated 
using the above approaches adjusted for the 
reference values of M=7.5 and 
'
v
=1atm. Using 
only Baez and Martin (1993) approach, the 
resulting CSR*sc for liquefiable soils were 
plotted against the values of N1,60,cs and qc1N,cs 
measured before stone column installation in 
Figure 10 and Figure 11 respectively with the 
boundary curve. By using Seed and Idriss 
(1971) approach for CSR evaluation (i.e 
without shear stress reduction), the data points 
recorded before reinforcement are located to the 
left of the boundary curve and are classified as 
liquefiable soils. However, when shear stress 
 
reduction of Baez and Martin (1993) approach 
is used, the data points are, mainly, found on 
the right of the boundary curve where no 
liquefaction occurs. The results confirmed the 
effect of shear stress reduction on liquefaction 
potential. Without taking into account the 
densification effect due to stone column 
installation, it can be concluded that considering 
the shear stress reduction of Baez and Martin 
(1993) decrease considerably the liquefaction 
risk in reinforced soil. 
 
 
 
Figure10 .Shear stress reduction effect on liquefaction 
potential using SPT data 
 
 
 
Figure 11.Shear stress reduction effect on liquefaction 
potential using CPT data 
 
4 CONCLUSION 
 
 In the present analysis, the effectiveness of 
stone column in reducing liquefaction potential, 
as mentioned in literature, is confirmed through 
the prediction of the shear stress reduction 
(CSR) and the increase of liquefaction 
resistance (CRR). 
 The comparison in CSR reduction, after stone 
column installation, using various approaches 
lead to the following conclusions: by assuming 
that the columns respond as shear beams, Baez 
and Martin (1993) approach provides the 
greatest amount of CSR reduction in reinforced 
soil. Whereas, when the flexural deformation of 
column is considered, Goughnour and Pestana 
(1998) found that CSR reduction with stone 
column reinforcement is very small or 
negligible. 
 Based on several case studies, comparison 
between SPT and CPT values measured before 
and after stone column installation confirmed 
the densification effect of this ground 
improvement technique. The corresponding 
CRR were calculated and results show that after 
stone column installation liquefaction resistance 
increases considerably. 
 Without taking into account the densification 
effect due to stone column installation, it can be 
concluded that shear stress reduction of Baez 
and Martin (1993) decreases the liquefaction 
risk in reinforced soil. 
 It can be concluded that field tests performed 
before and after stone column installation are 
recommended for liquefaction analysis and 
improvement effect should be considered for 
design of stone column to mitigate liquefaction. 
 
REFERENCES 
Adalier, K., and Elgamal A. (2004)Mitigation of 
liquefaction and associated ground deformations by 
stone columns. Journal of Engineering Geology, Vol. 
72, No. 3-4, , pp. 275-291. 
Baez, J.I. and Martin, G.R. (1993) Advances in the 
design of Vibro-systems for improvement of 
liquefaction resistance.Proceedings of the Symposium 
on Ground Improvement, Canadian Geotechnical 
Society, Vancouver. 
Baez, J.I (1995) A design model for the reduction of soil 
liquefaction by vibro-stone columns. Ph.D. 
Dissertation, USC, Los Angeles, CA. 
Baez,J.I.,and G.Martin (1992).Liquefaction observation 
during installation of stone columns using the vibro-
replacement technique,Geotechnical News,September 
Issue. 
Basarkar,S.S.,Panse,V.,Wankhade,R.R,(2009).Ground 
strengthening by vibro-stone columns-a case 
study.Indian Geotechnical Conference IGC. 
Blanchard, J. D. and Clements, K. M.(1993). Site 
 
Improvements with Stone Columns in Stratifield Silty 
Soils. Proceedings: Third International Conference on 
Case Histories in Geotechnical Engineering, St. 
Louis, Missouri, p. 7.18. 
Cetin, K. O., Seed, R. B., Der Kiureghian, A., Tokimatsu, 
K., Harder, L. F., Kayen, R. E., and Moss, R. E. S. 
(2004) Standard penetration test-based probabilistic 
and deterministic assessment of seismic soil 
liquefaction potential, J. Geotechnical and 
Geoenvironmental Eng., ASCE 130(12),1314–340. 
Chen, B. and Bailey, M., 2004. Lessons Learned from a 
Stone Column Test Program in Glacial Deposits. 
ASCE Geotechnical Special Publication No. 124, 
Geo-Support 2004, Orlando. p. 508-519. 
Durgunoglu,H.T, H.F Kulac,O Nur,S.Ikiz,O.Akbal and 
C.G Olgun,(1995).A case study on determination of 
soil improvement realization using CPT.Proceedings 
International Symposium on Cone Penetration 
Testinds,Vol.2,Swedish Geoechnical Society Report 
3;95.Oct.4-5,p. 441-446. 
Duzceer R. (2003).Ground improvement of oil storage 
tanks using stone columns. Proceedings of the 12th 
Pan American Conference in Soil Mechanics and 
Foundation Engineering, Cambridge, MA,1681–1686 
Gambin M.(1992).Reducing Liquefaction Potential by 
Deep Soil Improvement.Chap. II-4 in "Recent 
Advances in Earthquake Engineering and Structural 
Dynamic", V.Davidovici Editor, Ouest Editions, 
Goughnour, R.R., and Pestana, J.M. (1998) Mechanical 
behavior of stone columns under seismic loading. 2nd 
International conference on Ground Imporvement 
Techniques: 8-9 October 1998, Singapore: 157-162 
Green, R.A., Olgun, C.G., and Wissmann, K.J.(2008). 
Shear stress redistribution as a mechanism to mitigate 
the risk of liquefaction, Geotechnical Earthquake 
Engineering and Soil Dynamics IV, GSP 181, ASCE 
2008. 
Idriss, I. M., and Boulanger, R. W. (2008) Soil 
liquefaction during earthquakes. Monograph MNO-
12, Earthquake Engineering Research Institute, 
Oakland, CA, 261 pp. 
Keller,T.O, Castro,G.and Rogers,J.H. (1987).Steel Creek 
Dam foundation densification.Soil Improvement-A 
Ten Year Update, ASCE,Geotechnical Special 
Publication,No,12,p.136-166. 
Lee, T., Dash, U., and Anderson, R. (2005).Pipe Pile 
Stone Columns at Webster Street Tube, Oakland, 
California. Innovations in Grouting and Soil 
Improvement, p.1-15. 
Mahoney D.P.and Kupec J.(2014).Stone column ground 
improvement field trial: A Christchurch case 
study.NZSEE Conference. 
Mitchell, J.K. and Wentz, F.K.(1991).Performance of 
improved ground during the Loma Prieta earthquake, 
Report No. EERC91/12, Earthquake Engineering 
Research Center, University of California, Berkeley. 
Mitchell,J.K.,Baxter,C.D.P. and Munson, T. C. 
(1995).Performance of improved ground during 
earthquakes, Geotechnical Special Publications, vol. 
49, p. 1–36. 
Olgun, C.G. and Martin J.R. II (2008). Seismic behavior 
of columnar reinforced ground, The 14th World 
Conference on Earthquake Engineering, October 12-
17,Beijing, China 
Priebe, H.J (1998) Vibro Replacement to Prevent 
Earthquake Induced Liquefaction, Ground 
Engineering. 
Priebe, H.J. (1991).The prevention of liquefaction by 
vibro replacement. Proceedings of the 2nd 
International Conference on Earthquake Resistant 
Construction and Design, S. A. Savidis, Ed., p. 211–
219, A. A. Balkema, Rotterdam, The Netherlands. 
Rollins, K, Wright, A., Sjoblom, D., White, N., Lange, C. 
(2012). Evaluation of liquefaction mitigation with 
stone columns in interbedded silts and sands. Proc. 
4th Intl. Conf. on Geotechnical and Geophysical Site 
Characterization, Taylor and Francis Group, London, 
Vol. 2, p. 1469-1475. 
Rollins, K., Price, B., Dibb, E., and Higbee, J. 
(2006).Liquefaction Mitigation of Silty Sands in Utah 
Using Stone Columns with Wick Drains. Ground 
Modification and Seismic Mitigation. p. 343-348. 
Seed, H.B, Tokimatsu, K. Harder, L. F.,Jr., and 
Chung,R.(1985)Influence of SPT procedures in soil 
liquefaction resistance evaluations. J. Geotechnical 
Engineering, ASCE, 111(12),1425-1445, 1985. 
Seed, H.B. and Idriss,I.M(1982) Ground motions and 
soil liquefaction during earthquakes, Earthquake 
Engineering Research Institute, Berkeley, CA, 134 
pp.,. 
Seed, H.B. and Idriss, I.M. (1971). Simplified procedure 
for evaluating soil liquefaction potential. Jnl GED, 
ASCE, 97(9), 1249-1273. 
Seed, H.B.(1979) Soil liquefaction and cyclic mobility 
evaluation for level ground during earthquakes." J. 
Geotechnical Engineering Division, ASCE, 105(GT2), 
201-255. 
Shenthan, T. (2005).Liquefaction mitigation in silty soils 
using stone columns supplemented with wick drains. 
PhD Dissertation, University at Buffalo, NY, 342p. 
Slocombe, B.C., Bell, A.L. and Baez, J.I. (2000) .The 
densification of granular soil using Vibro methods, 
Geotechnique, Vol. L, No. 6, p.715-726. 
Weaver, T.M., Ashford, S.A., and Rollins, K.M. 
(2004).Performance and analysis of a laterally loaded 
pile in stone column improved ground.Procs. 13th 
World Conf. on Earthquake Engineering, EERI, 
Vancouver. 
Youd, T.L., and Idriss, I.M., eds, (1997),NCEER 
workshop on evaluation of liquefaction resistance of 
soils, National Center for Earthquake Engineering 
Research Technical Report NCEER-97-0022, p. 276