Q1: If the unit weight of sand particles is 2.696 g/cc. and porosity in loose state is 44%, the critical hydraulic gradient for quick sand condition, is

ANS:E - 0.95

G = Υs/Υw;
G= 2.696/1.
Ic = (G-1)(1-n),
Ic = (2.696-1)(1-0.44) = 0.9497. Unit weight of water = 1. So directly specific gravity of soil is = 1. G = Υs/Υw => G= 2.696/1.

Υs = Unit weight of sand particle.

Ic = (G-1)/(1+e).

e = n/(1-n) => e = 0.44/(1 = 0.44) = 0.78.

Ic = (2.696-1)/(1+0.78) = 0.9528. Ic = G-1/1+e.
e = n/1-n.
e = 0.44/1-0.44 = 0.78.
Ic = 2.696-1/1+0.78.
Ic = 0.9528.