cbr improvement of clayey soil with geo

“CBR IMPROVEMENT OF CLAYEY SOIL WITH
GEO-GRID REINFORCEMENT”
PROJECT REFERENCE NO. : 37S1000
COLLEGE
: ANGADI INSTITUTE OF TECHNOLOGY AND MANAGEMENT,
BELGAUM
BRANCH
: CIVIL ENGINEERING
GUIDE
: NOORAHMED A. H
STUDENTS : BABAGOUDA PATIL
NITESH MOTEKAR
PAVANKUMAR PUJARI
ULLAS ANAWAL
Keywords: CBR (California Bearing Ratio), geo-grid, Maximum Dry Density (MDD),
Optimum Moisture Content (OMC), reinforcement.
Introduction:
Economic constraint is a major issue in the maintenance and development of pavement infrastructure. Conventional practices in the design and construction of pavements require
material of higher quality to satisfy the required standards. Soil to be used as sub-grade does
not satisfy this norm in many parts of the world, making it mandatory to seek alternative
solutions for the use of weaker sub-grade soil. Sub-grade soil transfers the applied load from
the pavement to the layers beneath. It should have sufficient strength. Geo-synthetics, in
particular, geo-grids, are one of the commercial construction aids to improve the strength of
weaker sub-grade. Geo-grids include a large variety of polymer products designed to improve
strength of the sub-grade. Geo-grids are extensively used as reinforcement in structures with
unbound material like pavements, embankments, slopes and retaining walls. It is placed at
interface between the base course and the sub-grade.
Many authors report that the inclusion of geo-grids at the interface between base course and
sub-grade significantly improves the performance of the pavement on a weak sub-grade, both
in the laboratory and full-scale field experiments. Their studies showed significant increase in
the soaked and unsoaked California Bearing Ratio (CBR) values of the soil on the
introduction of fibers.
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Objectives:
 To collect clayey soil from site .
 To analyze the properties of soil selected .
 To check alternatives to improve CBR of clayey soil
 To improve the CBR of clayey soil by reinforcement of geogrid.
 To analyze the variation in CBR with change in depths of geogrid reinforcement
Methodology:
Geo-grid: Geo-grids are nothing but the open structures formed by bonding polymer strips at
their cross point or punching. Geo-grids are basically derived from the highly durable and
strong grid structures made up of polymer
CBR tests were conducted on selected soil, unreinforced and reinforced with a single layer of
geo-grid. To reinforce a sample, the geo-grid was placed in a single layer at different
positions: 20%, 40%, 60% and 80% of the specimen height from the bottom surface. It was
cut in the form of circular disc of diameter slightly less than that of the specimen to avoid
separation in the specimen by the reinforcing layer.
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The highest CBR of 16.64% was obtained for 0.8H (80% from bottom of the specimen) for
unsoaked condition and 12.36% for soaked condition. Hence from the results, it is clear that,
the optimum depth of geo-grid is 0.8H to get the maximum density.
Placing the geo-grid
Properties of Clayey Soil Sample Used For Project
Locally available clayey soil from shallow depth of about 1.5m is used for our project. The
soil is collected from Deshnur near Nesaragi of Belgaum Dist. It is 32 kms away from our
study area.
Results and Conclusions :
The results of soaked CBR values for soil sample at different depths of geo-grid
reinforcement indicated that the highest CBR of 12.36% at 2.5mm penetration for 80% dept
from bottom of mould is obtained for Clayey soil.
Based on the experimental results the following conclusions are drawn.
 The CBR of a soil increases by 50-100% when it is reinforced with a single layer of
geo-grid. The amount of improvement depends upon the type of soil and position of
geo-grid.
 CBR of sub-grade soil is 5.7 % without reinforcement and when geo-grid was placed
at 0.8 H from the bottom, the CBR value increased to 12.36 % in soaked condition.
 The stress-strain behaviour of sub-grade soils under static load condition improved
considerably when geo-grid was provided at optimum position
 Physical and strength characteristics of the soil are improved.
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 Stabilization provides sound pavement foundation and reduce the thickness of the
overlying layers.
Scope for future work:
Most of the Belgaum district area is covered with Black cotton soil, which is not suitable as a
sub grade material. The following studies can be carried out to improve the characteristics of
Black Cotton soil.
 A review on effects of stabilizing agents for stabilization of weak soil
 Strength of the soil also improved by fibre reinforcement by using geosynthetic fibers
it can be tried.
 Geosynthetics in railway track substructure.
 Effect of utilization of geosynthetic on reducing the required thickness of sub-base
layer of a two layered soil.
 Cost effectiveness of clavev soil & moorum, treated with fly ash-lime for construction
of low volume roads.
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