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8/21/2019 Evaluation of Stone Columns versus Liquefaction Phenomenon
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Evaluation of Stone Columns versus
Liquefaction Phenomenon
Arsalan Salahi1, Hamed Niroumand2, Khairul Anuar Kassim3
1 Master student, Department of civil Engineering, Faculty of Engineering,
Islamic A. University, Central Tehran Branch, Tehran, Iran2Post-Doctorate, Department of geotechnical engineering, Faculty of civil
engineering, Buein Zahra Technical University, Iran3 PhD, Department of geotechnical engineering, Faculty of civil engineering,
Universiti Teknologi Malaysia
ABSTRACTLiquefaction is a phenomenon which has caused various inherent defects in buildings and
structures in recent years. It is therefore imperative to become familiar with this important
phenomenon in all aspects of Civil Engineering practice and technology. Liquefaction occurs in
cohesion less soil. Liquefaction is more pronounced during earthquake in which excess pore pressure water increases considerably during cyclic loading. In other words, if effective stress
becomes nil during such increase, then Liquefaction is the outcome and in fact, liquefaction occursas sand boil, losing its load bearing capacity. There are many techniques currently available that
could prevent liquefaction. One such technique is to use stone columns which are the subject of
this article.
KEYWORDS: Liquefaction, earthquake, soil improvement and stone column
INTRODUCTION
One of the many destructive events that occur during an earthquake is liquefaction which in
recent years has resulted in enormous amount of damage to the buildings and structures.
Understanding the behavior of liquefaction and the parameters that contribute to its behavior is very
necessary in today’s engineering field. In the past three decades considerable research on this have
taken place results of which could give an insight into this important phenomenon, however there are
still some perceived gaps that need further research and studies. Stone columns are known as rammed
aggregate piers, Geo piers or granular columns which are useful technics in reducing liquefaction.
Stone columns ware first used in France in 1830 as soil reinforcement, but it was not until 1950s
when stone columns were widely used in Europe for soil strengthening as well as being utilized onseveral project is the US in 1970’s. The background use of stone columns is the use of material with
high shear strength that in turn produces lateral resistance in the soil. Stone column is a soil
improvement method that will reduce the settlement in foundations and increase load bearing capacity
of the soil. This involves replacement of 15-35% by volume the unsuitable soil by excavating some
wells with certain diameter, depth and spacing relative to each other and filling them with sand,
gravel or aggregate layers followed by compaction of each layer with vibrating equipment to form
vertical columns. In this paper all of the results gathered have been analyzed through a
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comprehensive literature review which has been presented. Where a perceived gap is identified this
has also been recommended for future research.
Kumar [1] has presented a way of liquefaction mitigation for a site placed in a floodplain area of
America which is prone of seismic and liquefaction hazards. Deep dynamic compaction has been
used to improve the mentioned site, but because of not being suitable for over than 6 to 9 meters, thesoil improvement has been achieved by installing stone columns. This new method of soil
remediation has impressively changed the soil properties. Some of the advantages of using stone
columns, especially in liquefiable saturated loose sands and sandy soils containing fine grains, can be
summarized as: 1. Soil compaction in lower depths and reducing liquefaction potential. 2. Improving
load bearing capacity of foundations. 3. Economic benefits of stone columns in comparison with
piles. 4. Ease of implementation causing time consuming benefits. 5. The complete consistency of
SPT value with the recommended values for compaction
In the following, there is shown the way of DDC implementation.
Figure 1: Deep Dynamic Compaction [1]
Tsukamoto et al. [2] conducted multiple series of experimental large-scale hollow cylindrical
torsional shear tests on clean fine sand, to study the degree of soil densification properties caused by
static sand pile driving installation which is achieved by simulating stress changes of a soil element in
the neighborhood of pile penetration. On this basis, they provided a diagram to help evaluating the
degree of soil densification effects, so that the SPT N1 value was achieved. They also took
advantages of some case studies which have recently been done at three sites in Japan. To cover the
whole of soil improvement area for an in-situ investigation, they installed several sand compaction
piles with an equal spacing. They also analyzed the stress changes in the field during the pile
penetration based on the classical elasticity theory. They applied sequential stress changes to
saturated spciments which have been prepared in a torsional hollow cylindrical shear test apparatus.
They found that a sufficiently great volume change will occur in the specimens, which can bring
about substantial densification in the sand. They reported that densification under drained conditions
was not great enough to cause volume decreases corresponding to that likely to occur in the field. In
the following picture the installation of sand compaction piles has been shown.
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Figure 2: Sand pile installation steps
Rudolph et al. [3] has presented a case study of using impact rammed aggregate piers (RAPs) for
a site in the vicinity of Colma Gulf by the aim of reducing its liquefaction potential. The project is
within a mixed residential, commercial, and light industrial area of California. The site contains
liquefiable sandy clay soil with a low plasticity index and mean compression. Their study includes the
results of a pre and post-ground improvement Cone Penetration Test (CPT) program that has been
implemented to evaluate the post-ground improvement liquefaction and seismic settlement potential.
In their investigation, they have only focused on the soil compression near the RAP without paying
attention to reducing pore water pressure built up or improving site stiffness that can be studied later.
The engineering result of this investigation is that using RAP will reduce the liquifaction potential of
seismic areas. One other engineering advantage of it, is time-dependent liquifaction reduction that is
deduced from it’s CPT penetration resistance. The following picture is related to RAPs configuration
in site.
Figure 3: Rammed Aggregate Piers improvement plan [3]
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Okamura et al. [4] described the results of in-situ tests, conducted at three sites where foundation
soil were improved by vibratory or non-vibratory sand compaction pile techniques. They also
obtained high quality undisturbed samples at each site by the in-situ freezing method and carried out
cyclic triaxial and shear tests on them.These triaxial specimens obtained from frozen samples, were
fully saturated in the triaxial cell. They also discussed about spatial distributions on SPT N-value and Nd -value which were obtained by rotary ram sounding. Besides, they compared the relationship
between liquefaction and N-value of natural soil deposits during an earthquake, which was achieved
by field evidences of earthquake. They used the test results, to verify the applicability of conventional
method in assessing liquefaction resistance of soils improved by sand compaction piles. By the
results, they concluded that penetration resistance is highly heterogeneous and randomly distributed
in a horizontal plane at any depth. Another engineering result of their study is that neither vibratory
compaction piles nor non-vibratory sand compaction pile cannot increase significantly the
liquefaction resistance of soils near the ground surface. Another conclusion of this study is that there
is good correlation between the liquefaction resistance and mean value of Nd , which have been
obtained from several locations. The results show that the liquefaction resistance of the improved
sand is considerably higher than those obtained from N-value based conventional method which is
only available for fully saturated soils.Adalier et al. [5] has prepared the results of dynamic centrifuge tests conducted by the aim of
assessing stone column performance against liquefaction phenomena in non-plastic silty soils.
The effect of stone column on stiffness improvement of considered site has been evaluated.
The tests have been conducted on four different conditions of silty specimens:
- With or without stone column
- With or without surcharge
All analyses have been done based on dynamic excitation conditions and recorded dynamic
responses. Some of the important conclusions of these experimental studies are:
- Using stone column is an effective technique to mitigate the liquefaction potential of
cohesionless silty sands.
- Stone column can partly rebate the excess pore water pressure build-up
- Stone column is an effective method in increasing the stiffness of foundation soil
- The mentioned method can significantly reduce the foundation settlement caused by effective
surcharge (up to 50%).
In the following, it has been shown the stone column configuration in the models.
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Figure 4: Cross-sectional and plan view of stone colmns in /model 2 [5]
Adalier and Elgamal [6] have investigated the current state of stone column technologies as an
effective method in mitigating liquefaction phenomena. In this paper, it has been conducted a review
by four important purposes: (a) Defining key considerations for using stone columns as a liquefaction
countermeasure, (b) Providing insights for designing and construction of stone columns, (c) Preparing
the latest advancements in researches and (d) Presenting the useful information resources. They
gathered a comprehensive list of significant publications that discuss stone columns as a seismic
liquefaction countermeasure in North America, Europe, and Japan. Also different applications of
stone columns have been mentioned here. At last, it must be mentioned that the installation method of
stone columns has a direct effect on reducing liquefaction potential, also stone column should be
designed to reduce clogging and loss of drainage effectiveness. The following picture shows the wayof modelling stone column by shaking table.
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Figure 5: Cross sectional view of model used in shaking table tests [6]
Shenthan et al. [7] developed an analytical methodology to evaluate the effectiveness of vibro
stone columns and dynamic compaction techniques together with pre-fabricated vertical drains by the
aim of increasing compression and mitigating liquefaction in saturated sands and cohessionless silty
soils. The improvement of designing guidelines to compact silty soil with the use of stone column and
dynamic compaction together with key parameters of soil reinforcement have been discussed in this
paper. In order to analyzing the soil compression by the use of stone column and dynamiccompaction, some numerical methods have been developed. In this study, the main soil properties and
stone column designing parameters for sands and saturated cohessionless silty soil have been
introduced. One of the important engineering advantages of this study, is preparing the design chart of
stone column and dynamic compaction in order to liquefaction potential mitigation. This method will
also reduce the consolidation time and improves the drainage rate. The computer modelling presented
here, is a proper method in analyzing stone column and dynamic compaction of different soils. In the
following, it has been shown a stone column together with wick drain.
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Figure 6: Vibro stone columns and composite vibro stone columns [7]
Sadrekarimi and Ghalandarzadeh [8] discussed two famous improvement methods of mitigating
liquefaction consisting gravel drains and compacted sand piles, which also have been compared at the
end. They conducted some precisely prepared 1g vibrating table tests by considering these methods.
These tests have been done in two cases of containing improvement method and without it, in which
the accelerations, pore water pressures and settlements are evaluated during the tests. They compared
the results to each other which drives this conclusion that compacted sand piles are more efficient
than gravel drains in case of liquefaction resistance and settlement of the subsoil during the shaking
period. Nevertheless, after shaking, the efficiency of the gravel drains is getting better by the means
of dissipating excess pore water pressure. They reported that the resistance to liquefaction could be
improved considerably by compaction, compared with the use of gravel drains. They concluded that
both gravel drains and compacted sand piles can retard excess pore water pressure build-up. The
engineering benefit of their comparative study is that the compaction method can better reduce the
settlement than gravel drains.
Homoud and Degen [9] have discussed about designing stone columns in seismic areas andguidelines for Marine Stone Columns designing against liquefaction. They described the new
patented Marine Double-Lock Gravel Pump, which is an innovation in marine stone columns
technology. Some of the main engineering benefits of this technique are: high speed implementation,
cost-effective construction and liquefaction mitigation in seismic areas. By the use of guidelines
presented in the paper, the engineers are capable of deducing suitable quality indexes for stone
column designs. In the following, there is shown a schematic view of implementing marine stone
columns.
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Figure 7: Marine Gravel Pump unit [9]
Rollins et al. [10] presented a case history in which pre-fabricated vertical drains were used in
connection with stone column treatment for a 4 meters thick layer of liquefiable silty and sandy silt. It
can be deduced from this study that the mentioned method can only be suitable for the soils with fines
percentage lower than 20%, otherwise the least effectiveness of this method will be achieved. Some
of the main engineering benefits concluded from this investigation are:
1- Using stone column together with wick drain will significantly improve the NSPT value.
2- If the stone columns spacing has decreased from 2m to 1.8m, the effectiveness will increase
up to 60%.
In the following, a view of stone column plan containing wick drains is shown.
Figure 8: Schematic view of stone columns and wick drains [10]
Krishna et al. [11] evaluated the liquefaction mitigation of the ground reinforced by granular piles
by considering the pore pressure build-up and dissipation accounting for both the densification and
drainage effects of granular piles. In this study, the modified Seed and Booker’s model (1977) for
computing the densification effect of granular piles and excess pore water pressure has been applied.
By the use of this new modified model, the effect of Rammed aggregate pier densification can also be
considered. Some of the engineering considerations of this investigation are listed below:
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- If the vertical drainages spaces are increased, the pore pressure rate will decrease and
increases with cyclic ratio increase.
- The effect of densification by regarding the coefficients of volume change and permeability,
can be positive or negative proportion to relative compaction degree.
Madhav and Krishna [12] have evaluated different mechanisms that are effective in the operationof granular piles as a ground improvement method for liquefaction mitigation. The different effective
mechanism is Drainage, Reinforcement, Storage, Dilation and Densification which have been studied
in details. At last, it has been proved that granular pile is a very effective technique in reducing
liquefaction potential of seismic areas. In this paper, generation and dissipation of excess pore water
pressure have also been investigated. Some of the engineering applications of granular piles comprise
its effectiveness in drainage, soil compression in the neighborhood of piles and soil reinforcement.
The most important mechanism of granular pile is dissipating excess pore water pressure as fast as
generating it.
Ranjbar Malidare and Janalizadeh Choobbasti [13] have studied the areas along the Caspian Sea
which contain saturated sandy soil together with high groundwater level that led to liquefaction
potential.They revealed the high efficiency of this technique for decreasing the risk of liquefaction, byusing numerical analysis software (FLAC), field explorations and laboratory tests. One of the most
important engineering benefits of installing stone column is the reduction of excess pore water pressure. In the following table, some of the most important results of this study have been presented.
Table 1: A summary of the results of analysis [13]
Krishna and Madhav [14] evaluated the densification of reinforced soil caused by dilation as an
effect of RAP reinforcement method, and also the pore water pressure generation and dissipation of
the reinforced ground under earthquake conditions have been explored. They applied the modified
theory of pore water pressure generation and dissipation developed by Seed and Booker(1977), for
evaluating the densification and dilation effects of Rammed Aggregate Piers together, under
earthquake conditions. In this study, by considering the effects of installation and dilation of gravel
column, the liquefaction phenomenon has been analyzed. They concluded that both coefficients of
volume change and permeability, can have positive or negative effect due to compression degree.Another result is that on the basis of different studies, dilation has positive effect on liquefaction, so
we can conclude that both factors comprising densification and dilation, should be considered in
designing stone columns.
Rollins et al. [15] investigated the pre-fabricated vertical drains in conjunction with stone
columns to reinforce sandy soils containing high fines content. No comparison has been made
between the existences of drains or lack of them in their study, but generally improved performance
of stone columns with drains may be achieved. Using pre-fabricated vertical drains in conjunction
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with stone column will significantly increase the NSPT value, however by increasing the fines content,
its effectiveness will decrease, in a way that the layers containing 15% or more clay sized particles,
will have the least effectiveness. Another important result of this investigation is that significant
increases in SPT values with time will be caused in the present of wick drains. The following picture
is a view of stone columns and pre-fabricated vertical drains.
Figure 9: Layout of Stone columns and wick drains [15]
Krishna and Madhav [16] prepared an overview of granular columns toward liquefaction. In this
study, the liquefaction phenomena and its results have been briefly discussed. Also there have been
discussed about some of the different techniques of liquefaction mitigation in seismic areas. The main
approach of this paper toward liquefaction mitigation, is applying granular columns. Different
construction methods of granular columns are discussed. They reported recent developments in the
area of liquefaction by investigating granular conclusions as liquefaction countermeasures, on the
basis of physical, numerical and analytical models. One of the important engineering effects of this
study is that, granular column is a very effective technique in reducing liquefaction potential and
since they also serve as drains, we can use them to dissipate the excess pore water pressure. Different
mechanisms of granular columns such as densification, reinforcement and drainage operation of stonecolumns, can significantly reduce the liquefaction hazards.
Moayedi et al. [17] investigated the behavior of gravel drain piles under intensive earthquake
loading beneath the foundation. To achieve this goal, they selected one of the waste water septic tank
project in north of Persian Gulf in Hormoz Island as a case study to find suitability of gravel drain
pile system to reduce and control excess pore water pressure. Furthermore, they conducted different
tests of soil mechanics to achieve a better understanding of the behaviour of the soil layers during an
earthquake. They also carried out several finite elements modeling and vertical gravel drain analyzes
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to make such a reduction and/or postponed the time duration of maximum achieved excess pore water
pressure during earthquake loading. They reported that using these drain piles has large effects on the
excess pore water pressure rate and creates a liquefaction zone during an earthquake. Another
engineering benefit of using drain columns beneath the foundation is that, it will reduce the
possibility of liquefaction during an earthquake. Another result is that if the excess pore water pressure rate at the first 10 seconds of earthquake is below 1, liquefaction will never happen. Also
these columns will be effective in increasing load bearing capacity. In the following, a schematic
view of drain piles modelling is shown. In the following picture excess pore pressure water in two
conditions has been shown:
Figure 10: Excess pore pressure in two different items [17]
(a) Without draining system (b) With gravel drain ple system
Singh et al. [18] carried out a number of tests on a small vibration table (shake table) applying
excitations to the ash samples. The purpose of these tests was exploring liquefaction reduction of sand
stone columns with or without fly ash. They also evaluated the excess pore pressure. Another thing to
be studied was the effect of spacing of stone-sand columns on liquefaction resistance of the fly ash.The addition of stone-sand columns increases the liquefaction resistance of the pond ash significantly.
This also decreases the time of generating pore pressure; duration for which maximum pore pressures
stays and total time for dissipation of pore water pressure. As application engineering benefits of this
study, we can say: If column spacing equals to 4d, the liquefaction resistance of pond ash will
increase up to 22%, and for the 3d spacing, the increase will arrive up to 92%. So 3d distance is the
best spacing of columns to reduce liquefaction potential. Easement of implementation, is another
engineering benefit of this method. In the following, there is shown a plan of sandstone columns. In
the following picture schematic view of tests have been shown:
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Figure 11: Plan of stone columns in shake table in different conditions [18]
Yanmei [19] analyzed the liquefable soil of foundation treated by stone columns, by dynamic
analysis procedure. He also studied on the design parameters of stone column which are effective
against liquefaction. He reported that by increasing the diameter of stone columns, the settlement and
excess pore water pressure decrease, and by increasing the columns spacing, the settlement and
excess pore water will increase too. At the end it must be mentioned that different parameters of stone
columns such as diameter, length, spacing, etc. have important effects on liquefaction. In the
following, a schematic view of stone columns is shown.
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Figure 12: Schematic view of stone columns [19]
Adalier and Elgamal [20] conducted some dynamic centrifuge tests, to study the liquefaction
remedial effects of stone columns in marine cohessionless silty soils. In their study, they have focused
on the strength benefits, rather than improved drainage and densification caused by columninstallation. The tests have been done in two conditions of exerting surcharge or lack of it, then thetwo conditions have been compared with each other under the same shaking conditions. Based on the
mentioned comparison, they concluded that stone column will partly dissipate the pore water pressure
build-up, increase the stiffness and load bearing capacity of foundation and significantly decrease the
settlement caused by surcharge. They suggested that, the marine stone column method may provide
environmentally friendly and cost effective solution for marine gravity structures on liquefiable soildeposits and can effectively reduce the liquefaction of these soils. The following picture is a plan of
stone columns.
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Figure 13: Plan and cross-sectional view of stone columns [20]
Shao et al. [21] have studied the effects of stone column and drains in reducing liquefaction
potential of one site in an area of Washington. Also, the designing and construction procedures of
these columns are presented. They determined the soil properties by different tests such as SPT and
CPT. They also analyzed and determined the pore water pressure by using the computer program
FEQDRAIN (Pestana, et al., 1997). This computer program together with post-treatment CPTs, show
liquefaction mitigation as a result of stone column densification and using seismic drains. The
mentioned program will assess the liquefaction potential and lateral spreading. In fact, the analysis
and design of stone column along with seismic drains have been done by FEQDRAIN. The following picture, shows the application of stone column and seismic drain in a site.
Figure 14: Earthquake drain and stone column plan [21]
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H.P. Singh [22] performed a number of tests on a small Vibration (Shake) Table on the pond ash
samples prepared at relative densities of 20% without and with stone-sand columns at 4d c/c spacing.
For some specimens, the pond ash has been improved by the effect of surcharge loads. He also
evaluated the liquefaction resistance of pond ash, in terms of maximum pore water pressure ratio for
all the tests. He reported that the liquefaction resistance of pond ash increases with the inclusion ofstone-sand columns, and also there is a significant increase in liquefaction resistance of pond ash due
to surcharge loads. He also concluded that by increasing the surcharge loads exerting on the pond ash,
the maximum excess pore water pressure rate will decrease, so the liquefaction potential will be
reduced too. The following picture is a schematic view of stone column.
Figure 15: Location of stone column in shake table tank [22]
Asgari et al. [23] have parametrically investigated the effects of stone columns and pile pinning
on reducing the potential of liquefaction during earthquakes, applying three-dimensional finite
element simulations using OpenSeesPL. At last the two mentioned techniques are being compared to
each other. The main aim of this paper is evaluation of different parameters in reducing liquefaction
potential. They have reported that increasing the structure mass will led to pore water pressure
decrease. Another important conclusion is that the dissipation of pore water pressure in sandy soil is
faster than silts.
Selcuk and Kayabali [24] have developed a finite element computer program which is able to
analyzing the distribution of excess pore water pressure during an earthquake. This computer program
is capable of analyzing the undrained condition before the installation of stone columns as well as thedrained conditions in the existence of stone columns. They applied the modified model of Seed and
Booker (1977). The main aim of this program is determining the appropriate construction of stone
columns in order to reducing the excess pore water pressure in liquefiable soil. The engineering
benefit of this investigation is determining the optimum diameter and spacing of stone columns for
the best protection against soil liquefaction. They reported that by increasing the radial distance
between stone columns, the pore pressure rate increases and reaches its maximum value when the
radial distance equals the radius of influence of the stone columns. Another engineering benefit of
this study, is minimizing the number of stone columns needed per unit area. They also reported that
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stone columns are utilized not only in preventing the soil liquefaction but also in reducing settlement
and increasing load bearing capacity.
Forcellini and Tarantino [25] presented computational modelling, free field response, and stone
columns remediation assessment. They also conducted a parametric study to assess the effectiveness
of stone column mitigation technique by gradually increasing the extension of remediation, in order toachieve a satisfactory lower level of permanent deformation. Their study is based on the use of a
finite element computational interface that able to analyse the earthquake-induced three-dimensional
pore pressure generation adopting one of the most credited nonlinear theories in order to assess
realistically the displacements connected to lateral spreading. So the aim 2of their analyses was
numerically reproduce Italian Emilia-Romagna Earthquakes (May 2012) allowing several
considerations. They concluded that stone column remediation was so effective in reducing the sand
stratum lateral deformation taking into consideration area replacement ratio ( rr) parameter. They
imparted that mitigation effectiveness and dimensioning design depend on the required performance
to be provided in terms of safety level. As an engineering benefit outcome from this investigation, it
can say that this study can quantify soil performance to liquefaction-induced effects using metrics that
are of immediate use for both pre-earthquake and post-earthquake risk assessment analyses.
Figure 16: Deformed mesh at the end of the motion [25]
Table 2: A comparison between papers conducted on stone columns versus liquefaction
phenomenon in geotechnical engineering.
Authors Year Project goal Application and Methodology
Kumar [1] 2000Liquefaction mitigation in a
floodplain site in seismic area.Use of stone columns and deep dynamic
compaction to reinforce deeper soils.
Tsukamot
et al [2]2000
Study the degree of soil
densification properties caused
by static sand pile driving
installation of stone columns.
Do multiple series of experimental large-
scale hollow cylindrical torsional shear
tests on clean fine sand by simulating stresschanges of a soil element in the
neighborhood of pile penetration.
Rudolph
et al [3]2003
Reducing liquefaction potential
by using impact rammed
Present the results of a pre and post-ground
improvement Cone Penetration Test (CPT)
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aggregate piers (RAPs) for a site
in the vicinity of Colma Gulf.
program that has been implemented to
evaluate the post-ground improvement
liquefaction and seismic settlement potential.
Okamuraet al [4]
2003
Evaluate foundation soil that
improved by vibratory or non-vibratory sand compaction pile
techniques against liquefaction.
Perform undisturbed samples at each site by the in-situ freezing method and carried
out cyclic triaxial and shear tests on them.
Adalier et al [5] 2003
Evaluate stone column
performance against
liquefaction phenomena in non-
plastic silty soils.
Perform dynamic centrifuge tests on four
different conditions ( with and withoutsurcharge and stone columns).
Korhan and
Elgamaz [6]2004
Mitigating of liquefaction
phenomenon by using stone
column technologies as aneffective method.
Gathering a comprehensive list of
significant publications that discuss stone
columns as a seismic liquefactioncountermeasure in North America.
Shenthan
et al [7]2004
Mitigating liquefaction in
saturated sands and
cohessionless silty soils byusing of vibro stone columns
and dynamic compactiontechniques together with pre-
fabricated vertical drains.
Developing analytical methodology andnumerical methods to evaluate the
effectiveness of vibro stone columns and
dynamic compaction.
Sadrekarimi
andGhalandarzade
h [8]
2005
Discussing two famousimprovement methods of
mitigating liquefaction
consisting gravel drains and
compacted sand piles.
Considering some precisely prepared 1g
vibrating table tests.
Homoud, andDegen [9]
2005
Designing stone columns in
seismic areas and guidelines forMarine Stone Columns
guideline against liquefaction.
Describing the new patented MarineDouble-Lock Gravel Pump.
Rollins
et al [10]2006
Evaluating pre-fabricatedvertical drains in connection
with stone columns for layer of
liquefiable silty and sandy silt.
Evaluating this method in different
conditions which the fine content is
variable.
Krishna
et al [11]2006
Reducing liquefaction
mitigation potential by ground
reinforcing ground by granular
piles.
Considering the pore pressure build-up and
dissipation accounting for both the
densification and drainage effects.
Madhav and
Krishna [12]2008
Considering granular piles as a
ground improvement method forliquefaction mitigation.
Evaluating different mechanisms that are
effective in the operation of granular piles.
Ranjbar
Malidareh andJanalizadeh
Choobbashi
[13]
2008Evaluating the decrease of riskof liquefaction near the Caspain
sea by stone columns.
Using numerical analysis software
(FLAC).
Krishna and
Madhav [14]2008
Evaluating the densification of
reinforced soil caused by
dilation as an effect of RammedAggregate Piers.
Rammed Aggregate Piers reinforcement
method for liquefaction mitigation.
Rollins
et al [15]2009
Reinforcing sandy soils
containing high fines content
Using pre-fabricated vertical drains in
conjunction with stone columns.
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against liquefaction.
Krishna and
Madhav [16]2009
Presenting an overview of
granular columns toward
liquefaction.
Evaulating different techniques of
liquefaction mitigation in seismic areas and
discussing the results.
Moayedi
et al [17]2010
Evaluating the behavior ofgravel drain piles under
intensive earthquake loading
and also controlling excess porewater pressure.
Using selected one of the waste waterseptic tank project in north of Persian Gulf
to find suitability of gravel drain pile
system.
Singh
et al [18]2010
Exploring liquefaction reduction
of sand stone columns with or
without fly ash.
Performing a number of tests on a small
vibration table (shake table) applying
excitations to the ash samples.
Yanmei [19] 2011
Analyze and evaluate dynamicresponse of liquefy soil under
foundation that reinforced with
stone columns.
Evaluating design parameters of stone
column which are effective against
liquefaction.
Adalier and
Elgamal [20] 2011
Evaluating stone columns as
liquefaction remedial effects inmarine cohessionless silty soils.
Conducting some dynamic centrifuge testsin two conditions of exerting surcharge or
lack of it, then the two conditions have been compared with each other under.
Shao
et al [21]2013
Studying the effects of stone
column and drains in reducing
liquefaction potential.
Designing and construction procedures of
stone columns.
Singh [22] 2013Evaluating the liquefaction
resistance of pond (fly) ash.
Perform tests on small Vibration (Shake)
Table on the pond (fly) ash samples.
Asgari
et al [23]2013
Investigating the effects of stone
columns and pile pinning on
reducing the potential of
liquefaction during earthquakes.
Applying three-dimensional finite elementsimulations using OpenSeesPL.
Selc¸uk and
Kayabali [24]2014
Determining the appropriate
construction of stone columns inorder to reducing the excess
pore water pressure in
liquefiable soil.
Developing a finite element computer program which is able to analyzing the
distribution of excess pore water pressure
during an earthquake.
Forcellini and
Tarantino [25]2014
conducting a parametric study to
assess the effectiveness of stonecolumn mitigation technique
Presenting computational modelling, free
field response, and stone columnsremediation assessment.
CONCLUSIONS
Following a thorough review of the published papers to date on the subject of “stone columns and
liquefaction it can be concluded that stone columns play very important role in soil remediation inareas that are prone to earthquake hence preventing or limiting liquefaction. Stone columns can
dampen liquefaction potential by pseudo drainage effect through granular material, strengthening the
surrounding soil near stone columns and improving the soil foundation under the buildings and
structures.
One of the stone columns tasks in the event of an earthquake is to reduce the liquefaction by
dissipating the pore water pressure build up in the soil as they are occur. Stone columns are very
effective in preventing liquefaction but this would depend on area replacement ratio. Another factor
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Vol. 20 [2015], Bund. 2 757
that affects this is extent of surcharge load but this is disputed in the literature review. Diameter of
columns, spacing relative to each other and columns lengths are other contributory factors too.
Negative pore pressure that is created by dilation is also important in liquefaction reduction.
Densification effect near dilation can have a positive role in reducing the liquefaction potential, since
liquefaction resistance can be enhanced by well compacted soil. It should be noted that diversity ofstone columns installations can be an important factor in liquefaction reduction and should be
considered in practice Also pond (fly) ash liquefaction resistance can be inserting by stone sand
columns. To conclude, stone columns are very effective way of reducing the liquefaction potential
and they can be more economical in their construction than other traditional and costly methods.
Based on the existing researches on the stone columns and liquefaction, it is clear that some gaps
are exists that haven’t solved yet now, and should be worked on the future by autures, researchers,
students and related engineers, as these following subjects:
a) Work on stone column behavior and its mechanism during earthquake, especially when
saturated silty and sandy soil exist.
b) For better understanding the behavior of stone columns during an earthquake, whenconstructed in silty deposits, some tests should be done like permeability, diameter or slenderness
effect of columns.
c) There is a wide limitation of stone column case histories and its response during an earthquake,
and also great need for well documented on this subject exists.
d) To delimitate the degree of improvement and the degree of densification or some operational
parameters on degree of improvement that reached by stone columns, no comprehensive analytical
trend exists.
e) Construction of stone columns in marine soils on offshore areas are slow and much expensive.
Solving this problem is necessary for future.
f) When stone columns are constructed in conjunction with wick ( pre fabricated vertical) drains,
no comparisons tests have been done to determine that how much of the improvement is by the stone
column and how much is by wick drain.
g) When stone columns are constructed in silty sand soils with high content of fine particles, its
efficiency remarkably come down. Solving this problem is necessary for the future.
h) Stone columns rigidity in horizontal loads are too small and since its deformation, it causes
large settlement under the structure, so solving this matter is a future need for civil engineering.
i) Silty or clayey soils with low plasticity are vulnerable to liquefaction. Pond(fly) ash reduce this
danger, so some research should be done on this material to reducing the liquefaction hazard.
Guideline
We conclude based on the recent surveys and articles regarding to soil improvement by using
stone column that stone column is known as an effective technique, with other techniques to prevent
Liquefaction phenomenon, to decrease Liquefaction potential in saturated cohesion less soil in areas
prone to having earthquakes. Regarding to last surveys in this case and based on the present articles
following engineering specifications can be known for mentioned technique:
• Densification of surrounding soil of stone column (especially cohesion less soil)
• Dissipation of excess pore pressure water
• Redistribution of earthquake
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Some of operating & engineering benefits of this technique to decrease soil liquefaction could be
named as an economical technique, high speed in operation and easy to operate.
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© 2015 ejge
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