Question

Foundation soil at the toe of dam has void ratio of 0.7. The specific gravity of soil grains is 2.6. To assure safety against piping, the upward gradient should not exceed 30% of gradient at which quick condition occurs. The maximum permissible upward gradient is

• A. 0.282
• B. 0.157
• C. 0.09
• D. 0.425

Answer 1

The correct option is A 0.282

G = 2.6
E = 0.7
$i_c=\frac{G-1}{1+e}$

$i_c=\frac{2.6-1}{1+0.7}=\frac{1.6}{1+0.7}=\frac{1.6}{1.7}=0.941$

Limiting gradient $=0.3\times 0.941$

$=0.282$

Maximum gradient is 0.282