Engineering Behaviour of Coir Reinforced Clay Soil

Engineering Behaviour of Coir Reinforced Clay Soil 1
RESEARCH PAPER ON THE ENGINEERING BEHAVIOUR OF NATURAL CLAY
SOIL REINFORCED WITH COIR FIBER
A Research Paper on Coir Fibre By
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Engineering Behaviour of Coir Reinforced Clay Soil 2
INTRODUCTION
Clay soil is characterized by high compressibility and low permeability because of its
high capacity of holding water. The absorption of water leads to the behaviour of soil
plasticity which does not disintegrate easily and can be deformed or moulded. Since the water
holding capacity of the soil is high, it gives the soil another feature of low permeability which
leads to swelling and hence expansion of soil making resulting in the soil being weaker.
These features of clay soil make not recommended for holding or supporting huge loads of
any structure above the soil surface and also difficult to be used in engineering and
construction industries.
For the minimization of these negative characteristics of the clay soil, the soil should
be reinforced with numerous materials by the use of techniques of ground improvement. This
research paper aims at investigating the engineering behaviour of reinforced clay soil with
crushed coir through carrying out consolidation test and compaction test. The coir that is
crushed is composed of 100% natural fibre which was gotten from coconut husks. The reason
why the coir of the coconut husks was used was that it is economically viable, easy to handle
and also very light. The clay soil that was used in this experiment was gotten from RIPAS
Bridge site with the liquid limit of 38.4%, plasticity limit of 22.5%, and plasticity index of
15.9% (Ahmad, 2010).
The clay soil went through processes like crushing and drying followed by Atterberg
limit test and sieving to determine its primary characteristics. The clay soil reinforced and
non-reinforced soil with inclusion percentages of 2.0%, 1.5%, and 1.0% of coir that is
crushed went through compaction test to determine the impact on the moisture content and
dry density. In the test for consolidation, the clay soil samples were reinforced with numerous
inclusion percentages of 2.0%, 1.5%, 1.0%, 0.5%, and 0% of the crushed coir. This is dome

Engineering Behaviour of Coir Reinforced Clay Soil 3
to evaluate the effects on consolidation behaviour as a result of the inclusion of crushed coir
(Arora, 2011).
Performance of Clay Soil Reinforced with Coir Fibre
Majority of the soils have enough shear strength and good compressive strength.
However, they have power tensile strength. This problem can be solved through carrying out
techniques of soil improvements which are aimed at soil reinforcement and soil stabilization.
The tests which can be carried out to determine the impacts of adding coir to the clay soil can
be done through model footing tests and Proctor compaction tests. The Standard Proctor
compaction tests were performed to evaluate the impacts of clay soil reinforced with coir
fibre on the moisture content and the dry density of the soil (Babu, 2014).
The clay soil reinforced and non-reinforced soil with inclusion percentages of 2.0%,
1.5%, and 1.0% of coir that is crushed went through compaction test to determine the impact
on the moisture content and dry density. The Standard proctor’s compaction test by the use of
light compaction was done in relation to the relevant IS standard so as to find out the
optimum moisture content and maximum dry density for the unreinforced and reinforced clay
soil using coir fibre (Babu, 2011). The results of the dry density versus moisture content
gotten from the experiment can be graphically represented as shown in the figure below:
Figure 1: Dry density vs Moisture content curves for the reinforced and non-
reinforced coir fibre (Dixit, 2012)

Engineering Behaviour of Coir Reinforced Clay Soil 4
From the results, the optimum moisture content and maximum dry density for the
unreinforced clay soil is 20% and 1.85 kg/m3 respectively. The maximum dry density do not
depend on the amount or percentage of fibre in the soil. The dry weight is higher due to
absence of fibre which reduces the dry weight. The optimum moisture content and maximum
dry density for the coir reinforced clay soil with 2.0% coir fibre is 18.5% and 1.84 kg/m3
respectively. 2.0% fibre will make this soil to have a higher moisture content and lower dry
weight. The dry density will be lower than that of unreinforced soil while the moisture
content will be higher than that of unreinforced soil. The decrease in density of the reinforced
fibres is as a result of fibre filaments which have less specific weight when compared to soil
grains and fibres prevent particles of soil from approaching to each other. The increase in
moisture content is due the results of the fibres having a greater water absorption capacity
than the surrounding soil (Kalkan, 2013).
The optimum moisture content and maximum dry density for the coir reinforced clay
soil with 1.5% coir fibre is 18% and 1.72 kg/m3 respectively. When 0.5% fibre is used, the
dry density will be lower and the moisture content will be lower than that of 2.0% fibre
inclusion. The fibre filaments which have less specific weight will be less in the 1.5%
inclusion making the density to be slightly higher and the absorption capacity of the less fibre
content will also be lower.
The optimum moisture content and maximum dry density for the coir reinforced clay
soil with 1.0% coir fibre is 19% and 1.64 kg/m3 respectively. The overall results show that
the maximum dry density reduces and the optimum moisture content increases with an
increase in the fibre content (Dutta, 2015). In this case, the amount of fibre is greatly reduced
in the soil making the specific weight to be higher since there is less fibre and also the
absorption capacity of the soil as a result of the fibre content will also be lower (Jiang, 2014).