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Soil Mechanics and Foundation Engineering - Engineering

Q1:

The void ratio of a soil sample decreases from 1.50 to 1.25 when the pressure is increased from 25 tonnes/m2 to 50 tonnes/m2, the coefficient of compressibility is

A 0.01

B 0.02

C 0.05

D 0.001

ANS:A - 0.01

.01 is correct.

The Coefficient of compressibility is asked, log should be used in the denominator if coefficient of compression (also known as compression index). Av= -(eo-e)/po-p.
= -(1.25-1.5)/50-25,
=0.01. e0 = initial void ratio = 1.5.
e = final void ratio = 1.25.
P0 = initial pressure = 25 t/m2.
P = final pressure =50 t / m2.
for co efficient of compressibility.
an = ((eo - e) / (p-po)) = (( 1.50-1.25)/(50-25)) = 0.01.
for compressibility index use;
= (( eo - e)/ (log (p/po)). CC = change in e/log10(initial stress+increased stress/initial stress).

Cc = 0.25/log(50/25) = 0.83.