+ of

If the water table rises to the ground surface Le., by a height of 2.5 m, the change in the effective stress will be,

~d =Yd x 2.5 - Yb x 2.5 =17 x 2.5 - 10.7 x 2.5 =15.75 kN/m2 (negative) Hence the decrease in shear strength will be,

=~d tan 35° = 15.75 x 0.70 = 11 kN/m2

Example 8.2 Direct shear tests were conducted on a dry sand. The size of the samples used for the tests was 2 in. x 2 in. x 0.75 in. The test results obtained are given below:

1 15 540 12 432 2 20 720 18 648 3 30 1080 23 828 4 60 2160 47 1692 5 120 4320 93 3348

o 1000 2000 3000 4000 5000

Figure Ex. 8.2