Engineering and Construction

The factor of safety (F) for sliding of the retaining wall foundation is often defined as the resisting forces divided by the driving force. The forces are per linear meter or foot of wall length, or:



The typical recommendation for minimum factor of safety for sliding of the retaining wall foundation is 1.5 to 2.0 (Cernica, 1995a).

In some situations, there may be adhesion between the bottom of the retaining wall foundation and the bearing soil. This adhesion is often neglected because the wall is designed for active pressures, which typically develop when there is translation of the footing. Translation of the foundation will break the adhesive forces between the bottom of the footing and the bearing soil and therefore adhesion is often neglected for the factor of safety of sliding.

The factor of safety (F) for overturning of the retaining wall is calculated by taking moments about the toe of the foundation (Point A, Fig. 11.2), and is:

In Eq. 11.7, the moment due to passive pressure is neglected. The reason is because with a rotation type failure mode, the wall may not move enough laterally to induce passive earth pressures. The typical recommendation for minimum factor of safety for overturning is 1.5 to 2.0 (Cernica, 1995a).