Dutta, T T and Saride, Sireesh
(2015)
Effect of Confining Pressure, Relative Density and Shear Strain on the Poisson’s Ratio of Clean Sand.
In: 50th Indian Geotechnical Conference, 17-19 December, 2015, Pune, Maharashtra.
Abstract
In comparison to other dynamic properties of soil, Poisson’s ratio is mostly considered as an elasti
c
constant. The effect of
different para
meters on the Poisson’s ratio of soil is neglected in most of the
available
literature.
Proper estimation of the Poisson’s ratio is required as it signifies the stress and
deformation characteristics of the soil.
In
this study a series of resonant column tests were performed to
determine the variation of Poisson’s ratio with confining pressure, relative density and shear strai
n.
Clean
sand free from fines content
was used in this study
. The tests were performed on sa
nd sample of
size 50
100 mm compacted at relative densities
of
30%, 50% and 75
%.
The sample preparation
was
done
by
using a split mold.
B
y using a funnel
,
t
he sand
was
gently poured into the split mold. Then each
layer
was
compac
ted by means of a tamping rod which weighs 150
g. The sample preparation
was
done
in 5 equal thick layers. By
performing
few trial sample pre
parations
, the number of blows required per
layer for a desired relative density
was
determined.
A fixed free type
of resonant column was used in this
study
. By performing the resonant column test in torsional mode as well as flexural mode of excitation
, it
is possible to estimate the Poisson’s ratio of the soil. The confining pressure
was
varied from 100 kPa to
800 kP
a. The shear strain
vari
ed
from 10
-
4
% to 10
-
1
%.
Figure 1 gives the variation of Poisson’s ratio with confining pressure for various relative densiti
es. From
the figure i
t is observed that there is
a
continuous decrease in Poisson’s ratio of the soil wit
h
an
increase
in
the
confining pressure as well as relative density. The percentage reduction in Poisson’s ratio obtained
for the soil subjected to a confining pressure of 800 kPa as compared to soil subjected to 100 kPa
confining pressure is
19 %, 21 % an
d 22
% for 30 %, 50 %, 75 % relative densities of the soil.
In addition,
the percentage
s
reduction in Poisson’s ratio of sand prepared at 75 %
relative density
as compare
to
30 %
relative density
are
14 %, 15.7 %, 16.7 % and 17.6 %
for sand subjected to 100
kPa, 400 kPa, 60
0 kPa
and 800 kPa respectively
. It
can be concluded
that the percentage reduction in Poisson’s ratio increases
with the increase in confining pressure as well as relative density.
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