Civil Engineering Professional Engineer Practice Exam 2025 – All-in-One Comprehensive Guide to Exam Success!

The resistance to sliding for retaining walls is primarily determined by evaluating the weight of the wall and the friction between the base of the wall and the subgrade soil. The weight of the retaining wall contributes to its stability, as a heavier wall will have a greater gravitational force acting downwards, which helps in opposing the lateral forces exerted by the soil and any surcharge loads behind the wall.

Friction plays a crucial role as well; the interface between the wall's base and the supporting soil generates a frictional resistance that also aids in preventing sliding. This frictional resistance is influenced by the coefficient of friction between the materials and the vertical load on the base of the wall, which includes the wall's weight and any additional loading conditions.

Other factors, such as the water pressure against the wall (as mentioned in one of the other options), can contribute to sliding by increasing the lateral forces acting on the wall. However, the fundamental calculation of resistance to sliding focuses on the weight of the wall in combination with the friction at the base, making this the most accurate and effective method for evaluating sliding stability.