Rise of water table above the ground surface causes A. Equal increase in pore water pressure and total stress B. Equal decrease in pore water pressure and total stress C. Increase in pore water pressure but decrease in total stress D. Decrease in pore water pressure but increase in total stress

The correct answer is: C. Increase in pore water pressure but decrease in total stress.

Pore water pressure is the pressure exerted by the water in the pores of a soil or rock. Total stress is the total force per unit area acting on a soil or rock.

When the water table rises above the ground surface, the water pressure in the soil pores increases. This increase in pore water pressure causes the soil to swell and the total stress to decrease.

The following is a brief explanation of each option:

• Option A: Equal increase in pore water pressure and total stress. This is not correct because the increase in pore water pressure is greater than the decrease in total stress.
• Option B: Equal decrease in pore water pressure and total stress. This is not correct because the decrease in total stress is less than the increase in pore water pressure.
• Option C: Increase in pore water pressure but decrease in total stress. This is the correct answer because the increase in pore water pressure is greater than the decrease in total stress.
• Option D: Decrease in pore water pressure but increase in total stress. This is not correct because the decrease in pore water pressure is less than the increase in total stress.