Note: Problem #3 is left for the reader to do. HINT: A soil doesn't work in tension, disregard the tension part of the diagram for the resultant's magnitude and position.
1.3 Designing a retaining wall
An engineer must know the basic parameters, specific weight ([itex] \gamma [/itex]), internal friction angle ([itex] \phi [/itex]), and cohesion (c), of the soil mass retained by the wall and the soil under the slab of the base. The purpose of knowing such values is to obtain the lateral pressure distribution that dictates the appropiate design.
The design process of a retaining wall is divided in two parts. The first one deals with the stability, and the second one with the strength.
This article will only focus on the stability of rigid retaining walls.