Question

Compression index developed by Casagrande is

• A. $C_V=0.009(LL+10\%)$
• B. $C_V=0.009(LL-10\%)$
• C. $C_V=0.009(LL+10\%)$
• D. $C_V=0.0009(LL+10\%)$

Answer 1

The correct option is B $C_V=0.009(LL-10\%)$

The compression index, $C_c$ is sometimes approximately estimated by empirical equations relating $C_c$ to some simple index property of the soil.

One of the most widely used equations with $\pm 30$ percent error, is the one proposed by Terzaghi and Peck (1967) for undisturbed clays of low to medium sensitivity.

$C_c=0.009(W_L-10)$

in which $W_L$ is the liquid limit expressed in percent.
This equation can be used only for clays which are not very sensitive $s_t<4$

For remoulded clays, the following equations is used

$C_c=0.007(W_L-7)$

Some of the other equations that have been proposed are:

$C_c=1.15(e_0-0.35)$ for all clays

$C_c=0.30(e_0-0.27)$ for inorganic cohesive soil

$C_c=1.15\times {10}^{-12}{W}_n$ for organic soils

Where, $W_n$ is the natural water content of the soil.