There are three types of slope failure such as (as shown in Figure 29.1):
Slope Failure: In this type of failure, failure surface intersects the slope above the toe. It occurs when slope angle is high and soil close to toe is strong and soil in the upper part of the slope is strong.
Toe Failure: Most common type of failure. In this type of failure, failure surface passes trough the toe. It occurs for steep slopes and when soil above and below the base is homogeneous.
Base failure: In this type of failure, failure surface passes below the toe. It occurs for flat slopes and when soil below the base is relatively week.
Fig. 29.1. Various failure surfaces.