Question

The ratio of a given volume change, expressed as a percentage of dry volume to the corresponding change in water content, is known as:
1. index ratio
2. volumetric ratio
3. linear ratio
4. shrinkage ratio

Answer 1

Correct Answer - Option 4 : shrinkage ratio

Shrinkage ratio  (S.R.):

• It is defined as the ratio of volume change expressed as the percentage of dry volume to the corresponding change in water content above the shrinkage limit.

\(S.R. = \frac{\frac{(V_o-V_d)}{V_d}×100}{w_o -w_s} =\frac{S_r}{w_o-w_s}= \frac{M_d}{\rho_wV_d}=\frac{γ_d}{γ_w} = G_m\)         ...(1)

Here,

Vo - Initial volume of saturated sample at water content wo

Vd - Final volume of the soil sample at water content ws

Md - Mass of dry volume 'Vd' of the sample

γd, γw - Unit weight of dry volume of soil and water respectively.

Gm - Mass specific gravity of soil in its dry state.

Sr - Degree of shrinkage = \(\frac{(V_o-V_d)}{V_d}×100\)

Soil may be classified into four groups as follows based on the degree of shrinkage -

Type of soil	Degree of shrinkage, Sr (%)
Good	< 5
Medium Good	5 - 10
Poor	10 - 15
Very Poor	> 15