Performance of Soft Soil Reinforced with Bamboo and Geonet

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 11 | Nov -2017 www.irjet.net p-ISSN: 2395-0072
© 2017, IRJET | Impact Factor value: 6.171 | ISO 9001:2008 Certified Journal | Page 646
Performance of Soft Soil Reinforced With Bamboo and Geonet
Alida Mathew1, Aswathy Sasikumar2
1M.Tech Student, Marian Engineering College, Kazhakootam, Trivandrum, Kerala
2Assistant Professor, Marian Engineering College, Kazhakootam, Trivandrum, Kerala
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Abstract - The naturally available bamboo can be used as
soil reinforcement, which proves to be economical than
commercially available geosynthetics. The comparison of
performance of bamboo grid reinforced soil with geonet
reinforced soil was studied in this paper. Bamboo grid
reinforcement has better performance than geonet
reinforcement. Maximumbearingcapacitywasobtainedwhen
3 layers of bamboo grids placed at a spacing of 50 mm
between the successive layers. The depthoffirstreinforcement
layer from the base of the model footing was kept constant in
this study.
Key Words: Bamboo grid, Bearing capacity, Bearing
Capacity Ratio, Settlement, 400 GSM coir geonet
1. INTRODUCTION
The existing soil at a construction site may not have
sufficient strength to bear the load coming on it. In such
cases, soil improvement or ground improvement is needed.
Improvement of soil can be done in many ways. The soil
improvement techniques are used for the following:
 Reduce the settlement of structures
 Improve the shear strength of soil and thus increases
the bearing capacity of shallow foundations
 Increase the factor of safety against possible slope
failure of embankments and earth dams
 Reduce the swelling and shrinkage of soil
Any soil which is susceptible to failure or cause excessive
settlement when superstructure is built over it is referred to
as soft soil. The methods which are capable of improving
certain characteristics of soft ground are considered as
ground improvement techniques. Soft soils have poor
strength and they are compressible. Various ground
improvement techniques are largely available now- a -days.
The different methods of ground improvements are over
excavations or replacement method, densification &
compaction (mechanical modification), hydraulic
modification,admixturestabilization,reinforcementmethod,
electrical modification method, thermal modification
method, etc.
Soil reinforcement method is one of the most popular
ground improvement techniques. One of the major reasons
for increase in the use of soil reinforcementistheavailability
of different materials and techniques for reinforcement.The
reinforcement method can be in the form of vertical
reinforcement like piles, stone column etc. or horizontal
reinforcement like soil nailing, geosynthetic products, etc.
Sometimes they may be expensive. Researchisbeingcarried
out to develop new ground improvement techniques which
are affordable. Ground improvement ismainlycarriedoutto
improve the bearing capacity and to reduce the settlement.
This paper focuses on reinforcing the soil wirh naturally
available bamboo in the grid pattern and then compares it
with the performance of 400 GSM coir geonet.
2. EXPERIMENTAL SETUP
A series of laboratory plate load testswereconducted.The
dimension of the tank used in the test was 500mm x 500mm
x 500mm. A square shaped steel plate of 100mm size with
12mm thickness was taken as the model square footing.The
load was applied to the footing via a centrally placed
hydraulic jack. The load applied was measured through a
pre-calibrated proving ring. Test setup is shown in fig.1.
Fig -1: Test setup
2.1 Materials Used
The materials used for the tests are Kuttanadu soil,
bamboo grid and 400 GSM coir geonet.
The soil collected from Kuttanadu region in Alappuzha
district was used for the preparation of foundation bed. The
soil was air dried and pulverised for the laboratory tests to
carry out. The properties of the soil are tabulated in table I.
The grain size distribution is shown in chart 1.

The naturally available bamboo was made in the form of a
grid of aperture size similar to the aperture size of 400 GSM
coir geonet. The width of each strip was 10mm. The bamboo
grid is shown in fig.2.
The coir geonet of 400 GSM was collected from Geonet
Enviroslutions Pvt Ltd, Ernakulam. The 400GSMcoirgeonet
is shown in fig.3 and the properties are given in table II.
Table -1: Properties of Soil
Properties Value
Natural moisture content 115 %
Specific Gravity 2.6
Clay Fraction
(IS 2720 PART 4)
18 %
Silt Fraction
(IS 2720 PART 4)
72.52 %
Sand Fraction
(IS 2720 PART 4)
9.48 %
Liquid Limit
(IS 2720 PART 5)
79 %
Plastic Limit
(IS 2720 PART 5)
49.8 %
Shrinkage Limit 19.92 %
Plasticity Index
(IS 2720 PART 5)
29.2 %
Optimum Moisture Content
(IS 2720 PART 7)
31.29 %
Maximum Dry Density
(IS 2720 PART 7)
1.35 g/cc
IS classification MH
Free Swell Index 3.92 %
UCC Strength
(IS 2720 PART 10)
0.49 kg/cm2
Chart -1: Particle Size Distribution of Soil
Fig -2: Bamboo Grid
Fig -3: 400GSM Coir Geonet
Table -2: Properties of 400 GSM Geonet
Characteristics 400GSM
Mass/unit area, g/m2 Min 400
Width, cm, Min 100 or as required
Length, m 50 or as required
Thickness at 20 kPa, mm, Min 6.5
Ends (wrap) 180
Pcks (weft) 160
Break Load, Dry (kN/m), Min
Machine direction
Cross machine direction
7.0
4.0
Break Load, Wet (kN/m), Min
Machine direction
3.0
2.0
Peak Load, Dry (kN/m), Min
Machine direction
7.5
4.0
Peak Load, Wet) (kN/m), Min
Machine direction
3.0
2.0
Trapezoidal Tearing Strength
(kN) at 25mm gauge length,
Min
Machine direction
0.18
0.15
Mesh size, mm, Max 20.0 x 16.75

2.2 Laboratory Plate Load Test
a) Preparation of soft soil bed:
The soft soil bed for the test was air dried and then
pulverized. It is then mixed in optimum moisture content
and fills it in the tank in 5 layers and compacted. The sidesof
the tank were coated with oil to reduce side friction. After
the preparation of test bed, plate load tests were conducted
and settlements corresponding to each loading were
measured using two dial gauges placed exactly opposite to
each other.
b) Test Procedures:
The reinforcements were placed in eachlayerofthetestbed.
The test was carried out by varying the number of
reinforcement layers. It was done for finding the effective
depth of reinforcement for the development of maximum
bearing capacity.
The square foundation supporting the prepared test bed is
shown in the fig 4.
Fig -4: Square Foundation Supporting the Prepared Test
Bed
The parameters shown in the figure are described below.
B = Width of the model square footing
u = Spacing between the base of footing and first
reinforcement layer
h = Spacing between two successive reinforcement layers
d = Depth of the last reinforcement layer from the base of
model footing
b = Width of geogrid
N = Number of geogrid layers.
Here the geogrid is placed full width of the tank. The
parameters u, h and B are kept constant throughout the test.
u and h were taken as 50mm. Here N is the varying
parameter i.e; d/B becomes varied.
The test was carried out for both bamboo grid and geonet
of 400 GSM and the performance of both the reinforcements
were compared.
2.3 Results and Discussions
Chart 2 shows the load settlement behaviour of
unreinforced soil bed and soil bed reinforced with bamboo
grid in different layers.
Chart -2: Load – settlement behaviour of soil when
reinforced with bamboo grid
From the test result the bamboo grid reinforced soil bed
has better performance than the unreinforced soil bed. Also
the bearing capacity increases with increase in number of
layers upto N = 3, after that it decreases. i.e; the optimum
number of layers for maximum bearing capacity was found
as 3.
Chart 3 shows the load - settlement behaviour of
unreinforced soil bed and soil bed reinforced with 400 GSM
coir Geonet in different layers.
Chart -3: Load – settlement behaviour of soil when
reinforced with 400 GSM Coir Geonet

From the test result the geonet reinforced soil bed has
better performance than the unreinforced soil bed. Also the
bearing capacity increases with increase innumber oflayers
upto N = 3, after that it decreases. i.e; the optimum number
of layers for maximum bearing capacity was found as 3.
The variation of bearing capacity ratio (BCR) with d/B for
bamboo grid reinforced soil and geonet reinforced soil are
shown in the chart 3 and 4 respectively.
Chart -3: BCR v/s d/B for bamboo grid reinforced soil
Chart -5: BCR v/s d/B for geonet reinforced soil
It is found from the chart 5 that the performance of
bamboo grid reinforced soil is better than geonet reinforced
soil.
Chart -5: Comparison of load settlement behaviour of
bamboo grid reinforced soil and geonet reinforced soil.
3. CONCLUSIONS
Reinforcing the soft soil with any material can improve it.
Here the study focused on reinforcing the soil with bamboo
grid and coir geonet of 400 GSM. The conclusions arrived
are:
 Soil reinforced with bamboo grid has better
performance than that reinforced with geonet.
 In both cases the bearing capacity increases with
d/B ratio up to N= 3 then it decreases, i.e; the
optimum number of layers for the development of
maximum bearing capacity is 3.
 The bearing capacity becomes increased and the
settlement gets reduced for reinforced soil.
REFERENCES
[1] Dharmesh Lal, N. Sankar, S. Chandrakaran. “Effect of
reinforcement form on the behaviour of coir geotextile
reinforced sand beds” Soils and Foundations 57, 2017
pp 227–236.
[2] Dutta, S. and Mandal, J.N. “Model Studies on Geocell-
Reinforced Fly Ash Bed Overlying Soft Clay.” Journal of
Materials in Civil Engineering, 2015,
10.1061/(ASCE)MT.1943-5533.0001356, 04015091.
[3] Hegde, A and Sitharam, T.G. “Use of Bamboo in Soft-
Ground Engineering and Its Performance Comparison
with Geosynthetics: Experimental Studies.” Journal of
Materials in Civil Engineering, 2016, 10.1061/ (ASCE)
MT.1943-5533.0001224., 04014256.
[4] Laman, M., Yildiz, A., Ornek, M., Demir, A. “Large scale
field tests on geogrid-reinforced granular fill underlain
by clay soil.” Geotextiles and Geomembranes, 2013
10.1016/j.geotexmem.2012.05.007, 1-15
[5] Omar, M. T., Das, B. M., Puri, V. K., and Yen, S. C. “Ultimate
bearing capacity of shallow foundations on sand with
geogrid reinforcement.” Can. Geotech. J., 30(3), 1993 pp
545–549.
[6] Zhou, H and Wen, X. “Model studies on geogrid- or
geocell-reinforced sand cushion on soft soil.”
Geotextiles and Geo membranes, 2008,
Doi:10.1016/j.geotexmem.2007.10.002, 231–238.

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