ANS:C -

The minimum depth ℎh of the foundation from the free surface of the earth for a retaining wall can be determined by considering the balance of forces acting on the wall. When a retaining wall supports a load W and retains earth of weight w per unit volume, the minimum depth of the foundation can be calculated using the concept of the pressure triangle. In this triangle, the vertical component represents the weight of the retained earth, and the horizontal component represents the load W acting on the wall. The minimum depth ℎh of the foundation can be calculated as: h=W/w⋅A​ Where:

• W is the load on the retaining wall,
• w is the weight of the earth per unit volume,
• A is the area of the foundation.

This formula represents the equilibrium condition where the pressure exerted by the retained earth is balanced by the pressure exerted by the load W on the retaining wall. Therefore, the minimum depth ℎ of the foundation from the free surface of the earth is given by W/w⋅A