Experimental Study of Bearing Capacity in Single and Group Stone Columns With and Without Encasement.pdf

HBRP Publication Page 1-22 2023. All Rights Reserved Page 1
Journal of Advances in Geotechnical Engineering
Volume 6 Issue 1
DOI: https://doi.org/10.5281/zenodo.7736100
Experimental Study of Bearing Capacity in Single and Group
Stone Columns With and Without Encasement
Mehul Katakiya1
, Samirsinh P Parmar2
1
Assistant Professor, Dept. of Civil Engineering, Chandubhai S Patel Institute of Technology,
CHARUSAT Campus – Changa.
2
Assistant Professor, Department of Civil Engineering, Dharmasinh Desai University,
Nadiad.
*Corresponding Author
E-mail Id: - spp.cl@ddu.ac.in
ABSTRACT
Stone columns are regarded as one of the most influential soil-stabilizing methods, capable of
significantly increasing the strength and workability of soft soil foundations. In this
experimental study, some laboratory tests on various model stone columns were performed in
order to improve its workability. They are made up of various gravel shapes and particle
distributions, as well as columns reinforced with geotextile reinforcements. Model stone
column were tested for load carrying capacity. Various soil parameters such as soil moisture
content and shear strength variation with respect to depth was also measured. The model
stone columns were tested for cased versus uncased condition and also tested for single
versus group effect of stone column. The test results were compared appropriately for cased
versus uncased condition and single versus group of stone columns. It has been revealed that
using, geotextile reinforcements increase their load-carrying capacity, providing a group of
stone columns also enhances the consolidation properties of clay and load carrying capacity
compared to single stone column. Moisture dissipation in the clay bed was found to be
greatest for the group of three stone columns.
Keywords: Soil improvement, Experimental study, Stone column, Geotextile reinforcement,
Cased and Uncased stone columns, Group of stone columns, moisture content.
Abbreviations:
Cu or Su Undrained Cohesion
D Diameter
De effective diameter of stone column
GP Granular Pile
H Height
Ip Plasticity Index
LL Liquid Limit
Qu or Q Ultimate Bearing Capacity
S spacing of the stone columns
w Moisture content
Wp Plastic Limit
ξ Shear Strength
GG-1 Geo-grid type-1
GG-2 Geo-grid type-2
GT Geo-Textile
OSC Ordinary stone column (without casing)
ESC Encased Stone column

Volume 6 Issue 1
INTRODUCTION
In soft soil, the creation of stone columns
results in increased load-carrying capacity
and stiffness, as well as a reduction in
consolidation settlement. Numerous
researchers have attempted to investigate
various aspects of stone columns. They
investigated the workability of stone
columns in a variety of soil samples,
including clay samples [1–4], soft clay
foundations [5, 6], layered soil [7], and
sand confined with single and multiple
geocells. Furthermore, numerical studies
on stone columns were carried out [8–10].
Inadequate lateral support in soft soils
significantly reduces the effectiveness of
stone columns. This lateral confinement
insufficiency is most common at shallow
depths, resulting in bulging failure of the
upper half of the columns. For the first
time, Huges and Withers [11] explain this.
In these circumstances, encasing the
column in various types of geotextile
improves the behavior of the stone
column. As a result, different
investigations on the behavior of
encapsulated stone columns have been
done, including experimental tests,
theoretical and numerical analysis, and
field applications. Some of them are
discussed in this article.
Small scale laboratory tests have been
used to conduct experiments, with the
majority of the focus being on the analysis
of load-settlement behavior [12–15].
Because one of the primary constraints of
stone columns is failure during loading,
various failure mechanisms, such as
bulging failure, shear failure, and punching
failure, have been studied in other studies,
such as those presented by Ali et al. [16,
17] or Chen et al. [18]. For these
experimental studies, the sleeves were
primarily made of geotextiles through a
sewn overlap of the fabric (e.g. Murugesan
and Rajagopal [19, 20] or a glued overlap
of the fabric) (e.g. Gniel and Bouazza
[21]). Yoo and Lee [22] studied the
performance of encased stone columns in
soft ground with full-scale load tests in the
field, in addition to small-scale laboratory
tests.
Other studies use triaxial compression tests
of encased samples, such as Sivakumar et
al. [23], who used stone columns to
reinforce clay samples with diameters and
depths of 300 and 400 mm, respectively, in
a large triaxial cell under a confining
pressure of 50 kPa. Wu and Hong [24] also
conducted triaxial compression tests on
reinforced and non-reinforced columns,
primarily to assess the effect of the
encasement on the radial strains of the
sample and the deviator stress. The same
procedure was used by Najjar et al. [25] to
examine normally consolidated kaolin
samples reinforced with single sand
columns. Furthermore, Kim and Lee [26]
conducted some tests using a centrifuge.
A study based on a compression test is
performed by plate loading test in this
paper to supplement the understanding of
stone column behavior in a more
rewarding way. This test is performed on
columns containing various geotextiles,
group of stone columns and cased versus
uncases stone column study. The effect of
moisture change due to installation of
stone columns for various combinations
were analyzed.
EXPERIMENTAL STUDY
In the present study, model test will be
carried out on the long end-bearing single
and groups of stone-columns with and
without reinforcement to evaluate the
relative improvement in the failure stress
of the stone-column reinforced Kaolinite
clay bed. This will be done also by
performing tests on three different kinds of
geo-textile materials.

Volume 6 Issue 1
Table 1:-Proposed Scheme of Investigation
Sr.
No.
Figure
Number
Abbreviation
Description of
With/Without Casing
Plate Load Tests
1
Figure-
1.2
A Single stone-column
Without Geo-textile (WGT)
2 B Group of 3 stone-columns
3 A-1 Single stone-column
With Geo-grid type-1 (GG-1)
4 B-1 Group of 3 stone-columns
5
Figure1.3
A-2 Single stone-column
With Geo-grid type-2 (GG-2)
7 A-3 Single stone-column
With Geo-textile (GT)
Table 1 denotes the experimentation
schedule for different combinations of
model test on stone columns and Figure -1
indicates the arrangement of model stone
columns in the test tank. The test tank is
made up of precast RCC pie section,
impervious from sides possess reasonably
good stiffness due to the hoop stress.
Fig1.1:-Plane view of tank
(all dimensions are in mm)
Fig.1.2:-Investigation-I Fig.1.3:-Investigation-II
Fig.1:-Schematic diagram for stone column model testing.
Figure 2 depicts the typical test arrangement of different materials inside the test tank to
carryout model stone column experiments. The
Section views of uncased stone column Section views of encased stone column
Fig.2:-Typical arrangement of Stone columns into the test tank.

Volume 6 Issue 1
PHYSICAL MODELS
Figure: Geogrid wrapped
around pipe
Figure: Bottom piece of Geogrid
for encased stone column.
Fig.3:-Geotextile wrapped around PVC pipe to install encased model test tank.
Test Materials
Soils
The basic soil properties such as Liquid
Limit, Plastic Limit, Maximum Dry
Density and Optimum Moisture Content
were investigated for kaolinite soil. The
properties of the Kaolinite clay are
depicted in table-2 and MDD-OMC curve
is shown in figure-4.
Table 2:-Property of clay
Sr. No Parameters for clay Properties of clay
1 Type of Clay Kaolinite Clay
2 Specific gravity (%) 2.56
3 Liquid limit (Wl) (%) 59.7
4 Plastic limit (Wp) (%) 26.91
5 Soil classification CH
6 Maximum dry density(gm/cc) 1.51
7 Optimum moisture content (%) 24
8 Free swell (%) 7.5
9 Shrinkage limit 25
Fig.4:-MDD -OMC curve for kaolinite soil.
1
1.1
1.2
1.3
1.4
1.5
1.6
10 15 20 25 30 35
Dry
unit
weight
(gm/cc)
Water Content (%)
MDD-OMC Curve
MDD=1.51
OMC = 24

Volume 6 Issue 1
Property of Granular Material
Gravel from locally available quarry site was used as a stone column fill material. Table-3
shows the properties of gravel.
Table 3:-Properties of granular material
Sr. No. Parameter of sand Value
1 Angle of internal friction (degree) 45°
2 Particle size (mm) 1 to 4.75
3 Dry density (KN/m3) 17.5
Geotextiles
Geo-textiles were procured from Giridhar,
Tec.Feb.Pvt.Ltd. from Ahmadabad. Open
glass fiber grid manufactured in stable
construction and is coated with modified
elastomeric polymer along with self-
adhesive backing as option. The melting
point of coating and glass fibers are > 250°
and >820° respectively. The geotextile
material was tested as per standard
guideline satisfying ASTM standards.
Table 4:-Geogrid specifications.
Type of grid
Geo-Grid-1 (GG-
1)
Geo-Grid-2 (GG-
2)
Test direction MD CD MD CD
Aperture size (mm) 9×9 9×9
Gauge length (mm) 100 100 100 100
Rib Width (mm) 4 1.9 4 1.9
Thickness (mm) 0.6 0.67 0.6 0.67
Maximum load (kN) 0.5 0.9 1.3 0.9
Deflection at maximum load (mm) 2.3 5.9 3 5.5
Stress at maximum load (N/mm2
) 80.1 137.7 170.1 114.2
% Strain at maximum load 2.3 5.9 3 5.5
Work to maximum load (J) 0.5 1.4 2.1 3
Stiffness (N/mm) 296.2 365.4 585.6 424.9
Young's modulus (N/mm2
) 4686.3 5448.7 7546.4 5476.1
Load at break (kgf) 20.6 35.5 89.2 34.2
Deflection at break (mm) 2.4 6.1 10 13.8
Stress at break (MPa) 32.1 55.1 112.8 43.3
Tests performed on geotextile
Random sampling done from the
geotextile roll and was tested for different
properties of geotextile. Physical and
mechanical properties of geotextile
materials, such as thickness, aperture size,
gauge length and stiffness, ultimate load,
young’s modulus, deflection at break etc.
were measured and compared for both
Geo-grid-1 and geogrid-2 which is shown
in table-4. Figure-6 describes the testing
procedure for geogrid-1, geotextile
material.

Volume 6 Issue 1
Single strip test on Geo
grid
Wide width test Thickness measurement
Fig.6:-Various tests performed on geotextiles
Seam Strength of Geotextile
When Geotextiles are sewn, the seam
strength plays an important role, so after
determining the elastic modulus of
Geotextiles, a cube test is performed to
determine the seam strength of
Geotextiles, and this cube test is also
performed with different densities.
The seam strength is evaluated using the
CBR test apparatus. The encased stone
cube is put in the center of two circular
plates in such a way that load is transferred
vertically at a rate of 1.25mm/min, as
shown in fig.-7 (a) & (b).
After achieving its maximum strength, the
cube begins to take load, as shown in the
figure-7. The density graph (figure-8)
shows that the load is the same, but
deformation is less when density is higher.
Fig.7:-Setup Arrangement for Compression Test on model stone column
under CBR apparatus
The deformation of GG-1 is less compared
to GG-2, for compression test carried out
in CBR apparatus. It is evident that more
the tensile strength of geogrid, more load it
can take under radial stresses. Seam
strength is important for the
geosyhthetically encased stone column, as
the fill material inside the stone column
remains intact.

Volume 6 Issue 1
Fig.8:-Load versus deformation for different geotextile material under CBR test.
Loading device
Fig.5:-Schematic AutoCAD diagram of loading device.
Clay bed preparation
• Mixing: - First of all the Powdered
Kaolinite Clay is taken and mixed with the
water, about double the liquid limit, to
form slightly stiff slurry. (figure-9, step-7)
• Sieving: - The slurry is then passed
through “M.S. SIEVE”, to form a uniform,
lump-free and air free paste of clay.
(figure-9, step-10)
• Filling: - Then the slurry is filled
into the RCC tank, having slotted bottom,
and allowed to consolidate under its own
weight for ten days and then it is covered
with aluminum plate, having radial holes.
• Consolidation: - After that the
uniform dead load is applied on that plate
for further consolidation of clay. The
slotted bottom allows the water to squeeze
out from the lower portion of the soil, and
similarly the radial holes of aluminum
plate allow from the upper portion of the
soil. The consolidation is applied in
incremental order as shown in table-5.
• Measurement: - After 1 month of
loading the plate is removed from the top
plate is removed and water content and
vane shear strength is measured.
• Covering: - After the measurement
of water content, the top of soil cake is
covered with the polythene sheet, to
maintain the water content same
throughout the experimental schedule.
After completing the process of sample
preparation, the casting of stone column is
0
2
4
6
8
10
12
14
16
18
20
0 200 400 600 800 1000 1200 1400 1600 1800
Settlement
(mm)
Load (kg)
GG-2
GG-1

Volume 6 Issue 1
started by rammed aggregate method as
shown in figure-11. The plate load test was
performed (section 3.7) to find the ultimate
bearing capacity.
Step-1 Cleaning inside the test
tank
Step-2 Installation of
porous stone
Step-3: Laying a filter
paper
Step-4: Sand layer
preparation
Step-5: Laying filter
paper
Step-6: Slurry filter
preparation
Step-7: Mixing of clay and
water
Step-8: Clay slurry
filtered and dropped
inside the tank
Step:9 Slurry dropped
inside the test tank
Step-10 Tank filled up to top level Step-11: Slurry tank left for
consolidation
Fig.9:-Step wide preparation of test bed of kaolinite clay.

Volume 6 Issue 1
Initial loading stages
The dead load is applied on the clay slurry,
to achieve actual field condition. For this
purpose, the sample is initially loaded in a
cumulative stress as shown in this table.
Figure 10 represents the step wise loading
of the clay bed.
Table 5:-Load applied for consolidation
Sr.
No.
Cumulative
stress
(kN/m²)
Area
of
tank
(m²)
Cumulative
of load (kN)
Load
(kN)
1 0.98
0.64
0.62 0.62
2 1.96 1.25 0.62
3 3.92 2.50 1.25
4 7.85 4.99 2.50
5 9.81 6.24 1.25
TOTAL OF LOAD (kN) 6.24
(a) 1st Loading Stage (b) 2nd Loading Stage (c) Final Loading Stage
Fig.10:-One Dimensional Consolidation test set-up.
Procedure for installation of stone
column:
Without encasement
Step-1. Placing of Casing-Pipe in to
Sample:
After preparation of the soil sample into
the 900 mm diameter tank, the casing pipe
is inserted into 1 of the 4 portions.
Step-2. Removal of clay from Casing-
Pipe:
Then by using the clay removal spoon the
clay is removed from the casing pipe.
After removing all the clay, the pipe is
cleaned using the cotton cloth.
Step-3. Pouring of First Layer of
Aggregate:
After removal of clay and cleaning the
casing pipe, the next phase of filling the
casing pipe is started. For this the funnel is
used. Then aggregate of fixed quantity, for
first layer, is taken and start pouring it into
the casing pipe.
The size of aggregate should be such that
there must be 8-10 particles around the
periphery of casing pipe. Here we are
using 4.75mm to 12mm size particles, to
form stone column.

Volume 6 Issue 1
Step-4. Partial Withdrawal of Casing
Up to Predetermined Depth with
Ramming:
After filling aggregates for first layer the
rammer of 2.6 kg is taken and 25 no’s of
blows are applied on it, simultaneously the
casing pipe is partially removed for
predetermined depth. The blows are
distributed equally over the whole area
inside the pipe and care should be taken
that the blows applied should be perfectly
in vertical direction.
Step-5. Stone Column Ready after Full
Withdrawal of Casing-Pipe:
Similarly required quantities for 4-5 layers
are taken in step by step pouring of
aggregate and removal of casing pipe is
carried out, and blows of hammer are
applied on each of the layers. This is done
till we reach to the top and the stone
column.
WITH ENCASEMENT
In case of the encased stone column,
before installing the encased column, we
need to convert the Geotextiles in circular
shape so in case of geogrid the ARALITE
are used to form a circular shape and in
case of Geotextiles the nylon string is
used.
Here the perimeter length of geotextile or
geogrid is 280 mm and overlap length is
25% of total perimeter length are taken to
form a 70 mm diameter circular shape.
Stepwise installation procedure for
encased stone column;
 To form 80 mm diameter cased
stone column, first larger diameter casing
pipe of 84 mm inserted perfectly vertical
into the soil sample. The same was
removed with soil.
 after that 78 mm diameter pipe was
taken and geotextile material was wrapped
around its periphery considering the seam
strength of geotextile material. The same
was inserted to full height of stone column
(i.e., 570mm). After ensuring
encapsulation of geotextile with
surrounding clay material, the casing pipe
was removed without disturbing the
geotextile material.
 then granular material as specified
was filled equal to the top level of clay
layer at a density of 2 gm/cc. Ramming
wad done by steel hammer to achieve
uniform density throughout the height of
stone column. Proper care was taken while
doing the ramming of coarser fill material,
so that the geotextile material will not fail.

(a) Insertion larger
diameter pipe
(b) Insertions of
main casing with
wrap GG
(c) Installed single
encased stone
column
(d) Installed groups
of three columns
Fig.11:- Step by step installation of encased stone column.

Volume 6 Issue 1
ANALYSIS & DISCUSSION OF
EXPERIMENTS
Different gravel density
The density of fill material inside the stone
columns plays important role to improve
the bearing capacity. To ensure the
behavior of stone columns deformation
with respect to density of fill material, the
granular material was filled at 1.97 gm/cc,
2.0 gm/cc and 2.1 gm/cc density into the
geo-grid encasement and then tested under
CBR apparatus. Load vs deformation
behavior was measured up to 15 mm
deformation. It is observed that the stone
column filled with higher density of
material fill able to sustain more load and
less settlement. To achieve uniformity for
the density of fill material 2.0 gm/cc was
adopted in the current experimentation.
Fig.12:-Load Vs settlement for different density of gravel filled inside the encased stone
column.
Shear strength of soil
Before starting the casting of the stone
column in situ shear strength is measured
using vane shear test apparatus. Here the
rectangle vane having four sleeves are
welded at a 90˚ angle and total height of
the needle is about 80cm.
The apparatus is arranged on the top of the
tank and the needle is sinking up to the
required depth by arranging the instrument
at different height, for measuring the shear
strength. The shear strength is measured
on CG of each section at a different depth
before the casting of granular column. But
after performing a plate load test the shear
strength is measured nearer to the column
in case of the single stone column and at
the center of three columns in case of
group three columns.
Then, the variation in shear strength with
respect to depth is shown in the figure-14
&15. It had been observed that the shear
strength improved with increased depth.
Shear strength measured after installation
of stone column is higher than it was
measured before installation of stone
columns for both encased as well as cased
stone columns. The shear strength of the
encased stone column is higher because it
provides proper drainage to allow water to
flow out of the soil mass, whereas in the
case of the ordinary stone column, the
0
2
4
6
8
10
12
14
16
0 100 200 300 400 500 600 700
Deformation
(mm)
Load (kg)
1.97 gm/cc
2 gm/cc
2.1 gm/cc
Density

Volume 6 Issue 1
water becomes clogged and spreads into
the soil, preventing a proper drainage path
from developing in the soil strata.
Improvement in shear strength is almost
1.2 times higher in the encased stone
column with respect to ordinary stone
column in both the cases because the
ordinary stone column giving less drainage
due to the clogging and squishing of the
particle. But in case of the encased stone
column, it resists the failure of the column
and gives proper drainage path to flow out
water from the surrounding soil mass.
Fig.13:-Arrangements of vane shear test apparatus
Fig.14:-Shear strength variation between single OSC & ESC
5
10
15
20
25
30
35
40
45
0 5 10 15 20 25 30 35 40 45
Depth
(cm)
Shear Strength (kN/m2)
before PLT(OSC)
after PLT(OSC)
before PLT(ESC, GG-1)
after PLT(ESC, GG-1)

Volume 6 Issue 1
Fig.15:-Variation of shear strength between groups of three OSC & ESC
Fig.16:-Improvement variation of shear strength with respect to depth.
Table 6:-Improvement in shear strength of soil due to stone column installation
Depth (cm)
Difference between initial and final reading
Single OSC
(kN/m2
)
Group of
three OSC
(kN/m2
)
Single ESC
(kN/m2
)
Group of three ESC
(kN/m2
)
10 3.51 7.68 3.07 9.21
15 4.39 6.14 3.07 7.68
25 3.51 7.68 6.14 10.75
35 5.26 13.82 9.21 19.96
45 7.02 15.35 12.28 23.03
Average 4.74 10.13 6.75 14.12
5
10
15
20
25
30
35
40
45
5 10 15 20 25 30 35 40 45 50 55 60 65
Depth
(cm)
before PLT(OSC)
after PLT(OSC)
after PLT(ESC, GG-1)
0
5
10
15
20
25
30
35
40
45
50
0 5 10 15 20 25 30 35
Depth
(cm)
Single OSC
Group of three OSC
Single ESC
Group of three ESC

Volume 6 Issue 1
Moisture content “w” (%)
In order to measure the water content, a
casing pipe is inserted into the tank and a
sample is collected at various depths.
Similar to the vane shear test, water
content is measured closer to the column
in the case of a single stone column and in
the center of three columns in the case of a
group of three columns.
The moisture content is measured depth
wise before and after the plate load test by
bringing the bore-hole closer to the stone
column, as shown in the figure. The graph
depicts the change in water content with
respect to depth before and after the PLT.
Because we considered two-way drainage
systems, the maximum water content is at
the tank's middle depth, according to this
graph (Top & Bottom of the tank). A stone
column provides a drainage path for
quickly draining water from the soil mass.
So, after conducting the experiment, we
discovered that the water content decreases
after casting the stone column, owing to
the increased rate of consolidation.
Fig.17:-Variation of water content between single OSC & ESC
Fig.18:-Variation of shear strength between groups of three OSC & ESC
5
10
15
20
25
30
35
40
45
50
50 55 60 65 70 75 80 85 90 95 100 105
Depth
(cm)
Water Content (%)
before PLT (OSC)
after PLT(OSC)
after PLT(ESC ,GG-2)

Volume 6 Issue 1
Fig.19:-Improvement variation of water content
Table 7:-Improvement in moisture content dissipation
Depth (m)
Difference between initial and final reading
Single OSC
(%)
Group of
three OSC
(%)
Single ESC
(%)
Group of
three ESC
(%)
0.10 5.3 6.36 3.45 6.54
0.15 2.86 6.54 5.49 7.67
0.20 3.33 6.73 4.9 9.03
0.25 2.24 6.33 3.97 8.32
0.30 3.33 7.78 4.63 10.39
0.35 3.29 7.63 6.23 11.04
0.40 4.05 8.85 7.08 11.76
0.45 4 9.6 7.25 12.93
Average 3.55 7.48 5.38 9.71
Bearing Capacity of Soil “Qu”
The plate load test is carried out for
finding the bearing capacity and its
variation with encasement.
Here, the rectangle plate is used in the case
of the single stone column having a size is
15cm×15cm×0.5cm and in the case of a
group of three columns 28cm diameter and
1cm thick circular plate are used. The
same plate is used in the case of a single
and group of three encased stone columns.
Then, the plate load test is performed as
per the IS:15284 (part-I), and the reading
is measured at each increment.
After completing the plate load test the
graph of load versus settlement is plotted
in every case. Here three-dial gauge is
arranged at an angle of 60˚ to measure the
settlement of the plate and a hydraulic jack
is used to apply the loading.
0
5
10
15
20
25
30
35
40
45
50
0 5 10 15 20
Depth
(cm)
Water Content (%)
Single OSC (%)
Group of three OSC (%)
Single ESC (%)
Group of three ESC (%)

Volume 6 Issue 1
Fig.19:-Plate load test on model stone column.
Here as shown in the graph the soil is like
a liquid because the water content is higher
than the liquid limit, even if we stand on it,
we will directly sink up to the bottom.
The load carrying capacity of the single
ordinary stone column is very less because
of the column bulging and also, it's so
much difficult to casting a column because
Their shear strength is very less and water
content is higher than the liquid limit.
In the case of end-bearing columns, the
bottom of the column rested on hard strata
and so penetration of the column was not
possible, the columns also could not fail
due to bulging because the bulging was
restricted by the geotextile encasement. A
versatile failure criterion by Vesic (1963)
defines the failure load as the point at
which the slope of the load– settlement
curve first reaches zero or a steady
minimum value. In this case, the stress–
settlement curves were almost linear when
the tests were stopped and the failure did
not occur as per this criterion. After the
test, the geotextile was found to be intact
without any damage indicating that the
induced hoop stresses were less than the
tensile strength of the geotextile which
prevented the failure of both geotextile and
columns. The tests on a group of geogrid-
encased end-bearing columns had to be
stopped at 13 mm settlement due to
slippage and tilting of the plate. At 13 mm
settlement bending was clearly visible in
the upper portion of the columns. As the
footing load increased, the net outward
force in the soft soil in the radially
outward direction increased as explained
earlier causing significant bending of the
columns so I have to stop the test at this
stage of loading.
Maximum possible precautions were taken
during the casting of the columns to ensure
a uniform column density, constant
diameter, and verticality. Thus, in the case
of both single and group end-bearing
reinforced columns, slippage and tilting of
the plate did occur at different stages of
loading and the test was stopped before the
maximum pre-decided footing settlement
(25mm) was reached. Possibly, during
these tests, at some stage, the stone chips
in some part of the column became
interlocked and resisted the settlement. As
the footing load was further increased, the
interlocking was broken, giving rise to
sudden jerks and uneven settlement
resulting in slippage and tilting of the
footing. In the case of the columns that
were fully encased with Geo-grid, the
footing slipped and came between the
columns, pushing the tops of the columns
outward and consequently the bases of the
columns inwards. This happened because
the columns were very stiff in this case as
they were fully encased with Geo-grid.
The stiffness of the column goes on
increasing during the process of loading of

Volume 6 Issue 1
the model due to reduction in the void
ratio of the stone chips upon compaction,
facilitated by lateral support provided by
the reinforcing material in the form of
increased hoop stresses.
From the load settlement graph the
improvement in the case of the encased
stone column is higher than the ordinary
stone column. So, here we have observed
the load carrying capacity corresponding
to 10mm settlement in order of single
OSC, a single ESC, a group of three OSC,
and a group of three ESC was 31kg,
310kg, 120kg and 300kg respectively
Effects of group of stone columns
The load vs settlement curve for uncased
stone columns, cased stone columns (both
GG-1 and GG-2) and geotextile material
shown in figure 20, 21, 22 and 23
respectively. It had been observed that
compared to single column, group of three
stone column exhibits more load carrying
capacity irrespective of provision of
casing. The Improvement in bearing
capacity is more predominant for uncased
stone columns compared to cased stone
columns.
Fig.20:-Load vs Settlement curve for Ordinary stone column (Uncased)
Fig.21:-Load vs Settlement curve for Encased stone column (GG-1)
0
5
10
15
20
25
30
0.01 0.1 1 10
Settlement
(mm)
Load (KN)
Three Column OSC
Single Column OSC
0
2
4
6
8
10
12
14
16
18
20
0.10 1.00 10.00
Settlement
(mm)
Load (KN)
Single column ESC (GG-1)
Three Column ESC (GG-1)

Volume 6 Issue 1
Fig-22: Load vs Settlement curve for Encased stone column (GG-2)
Fig.23:-Load vs Settlement curve for Encased stone column (GT)
Comparison between cased and uncased
stone column
The load vs settlement plot for single stone
column for uncased and cased by all
casing material was prepared to investigate
effect of casing. It is evident that effect of
casing is predominant over uncased
condition. Here it is peculiar that GG-2
takes more load compared to GG-1 and
GT material. The tensile strength of GG-2,
GG-1 and GT is 112.8 kN/m, 32kN/m and
30.7 kN/m respectively.
The effect of tensile strength of material
for encasement also plays important role
as the radial stress generated into the stone
column due to vertical stress leads to fail
the geotextile material under tensile forces.
0
5
10
15
20
25
30
0.10 1.00 10.00
Settlement
(mm)
Load (KN)
Single Colum ESC (GG-2)
0
5
10
15
20
25
30
0.02 0.15 1.50
Settlement
(mm)
Load (KN)
Single Column ESC (GT)
Three Column ESC (GT)

Volume 6 Issue 1
Fig.24:-Load vs Settlement curve for single stone columns.
Fig.25:-Load vs Settlement curve for group of three stone columns.
CONCLUSIONS
The following are the key findings of the
current study.
 Load comparisons corresponding
to 10mm settlement of stone column show
that load bearing capacity of single OSC, a
group of three OSC, a single ESC and a
group of three ESC were 0.304 kN,
1.177kN, 3.04 kN, 2.942 kN respectively.
 The load test revealed that the
settlement of a stone column rapidly
increased above the load of 0.304 kN for a
single stone column and 1.177 kN for a
group of three ordinary stone columns.
This appears to be the cause of column
failure due to the bulging of the upper part
of the column. The load carrying capacity
of the Geo-grid encased stone column
prevented the column from collapsing
suddenly by limiting the column's bulging
failure and thus improved the load
carrying capacity of the GESC.
0
5
10
15
20
25
30
0.01 0.10 1.00 10.00
Settlement
(mm)
Load (KN)
Single Column OSC
Single Column ESC (GG-1)
Single Column ESC (GG-2)
Single Column ESC (GT)
0
5
10
15
20
25
30
0.01 0.10 1.00 10.00
Settlement
(mm)
Load (KN)
Three Column OSC
Three Column ESC (GT)

Volume 6 Issue 1
 According to the plate load test, the
load carrying capacity of a single encased
stone column improved by 10 times that of
an ordinary stone column, but the load
carrying capacity of a group of three
encased stone columns improved by 2.5
times that of a group of three ordinary
stone columns.
 When failure stress is compared in
enclosed single column and group column
tests, the values in a single column are
(approximately) marginally higher than the
values in column groups. This is because,
unlike individual columns, group columns
are compressed and bent. At about the
mid-depth of the clay sample, the moisture
content is maximum before and after the
test. This is because the drainage is
provided in two ways and the middle
section of the sample is the highest
distance from the drainage side. The water
content at the top and bottom is reduced
considerably.
 Reduction of the water content is
observed in all stone column cases, but the
maximal water content in a group of three
stone columns is recorded and the
corresponding values are reduced to 3.55
%, 7.48 %, 5.38% and 9.71% in the order
of three ESC, three OSC, single ESC and
single OSC.
ACKNOWLEDGEMENT
Authors are thankful to PG Geotechnical
engineering laboratory staff of Department
of Civil engineering of Dharmasinh Desai
University, Nadiad, India.
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Ethics approval and consent to participate
The Study conducted at Geotechnical
Engineering PG Lab, Dharmasinh Desai

Volume 6 Issue 1
University, Nadiad, Gujarat, India. All the
data, readings and observation are
produced in the paper is purely unique and
solely the property of above-mentioned
laboratory.
Availability of data and material
All data generated or analyzed during this
study are included in this published article
(and its supplementary information files).
The datasets generated during and/or
analyzed during the current study are not
publicly available due to the data is not
published in any published yet, but are
available from the corresponding author on
reasonable request.
Competing interests
The authors declare that they have no
conflicts of interest regarding financial
assistance, involvement of animals or
humans as well as standards of practice to
perform the experiments.
Funding
The experimentation set-up and material
were provided post graduate Geotechnical
Engineering laboratory, Dharmasinh Desai
University, Nadiad, Gujarat, India. The
Research is fully sponsored by
Dharmasinh Desai University.
Acknowledgements
The authors are thankful to Dr. H.M.
Desai, Who granted permission to conduct
research work in Surface Science and Nano
technology, and also permit to use the
Laboratory in above mentioned
department.
Authors' information
Authors SAMIRSINH P PARMAR MEHUL KATAKIYA
Affiliation Assistant Professor, Dept. of Civil Eng.
Dharmasinh Desai University, Nadiad
The then M.Tech Student, Now-Assistant
Professor, Dept. of Civil Engineering,
Chandubhai S Patel Institute of Technology,
CHARUSAT Campus – Changa.
Mail:ID spp.cl@ddu.ac.in mehulkatakiya.cv@charusat.ac.in
Cite this article as:
Mehul Katakiya, & Samirsinh P
Parmar. (2023). Experimental Study of
Bearing Capacity in Single and Group
Stone Columns With and Without
Encasement. Journal of Advances in
Geotechnical Engineering, 6(1), 1–22.
https://doi.org/10.5281/zenodo.7736100

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