Question

The critical gradient of the seepage of water in a soil medium is (Where G=Specific gravity of soil, and e=Void ratio.)
1. \(\dfrac{1-G}{1+e}\)
2. \(\dfrac{G-1}{1+e}\)
3. \(\dfrac{1+e}{1-G}\)
4. \(\dfrac{1+e}{G-1}\)

Answer 1

Correct Answer - Option 2 : \(\dfrac{G-1}{1+e}\)

Concept:

Critical hydraulic gradient (ic): The quick condition occurs at a critical upward hydraulic gradient ic, when the seepage force just balances the buoyant weight of an element of soil. The critical hydraulic gradient is typically around 1.0 for many soils.

At the critical conditions, the effective stress is equal to zero.

Critical hydraulic gradient,

∴ \({{\rm{i}}_{\rm{c}}} = \frac{{{\rm{G}} - 1}}{{1 + e}} \)