Refer to Problem 9.9. Water may be introduced into the cut to improve the stability against heaving.

Question:

Refer to Problem 9.9. Water may be introduced into the cut to improve the stability against heaving. Assuming that a cut is made up to the maximum permissible depth calculated in Problem 9.9, what would be the required height of water inside the cut in order to ensure a factor of safety of 1.5?