5.2 Stability analysis of slope

Most conventional stability analyses of slopes have been made by assuming that the curve of potential sliding is an arc of a circle. The procedures of stability analysis may be divided into two major categories.

1.  Mass procedure: In this method, the mass of soil above the surface of sliding is taken as a unit. This procedure is useful when the soil that forms the slope is assumed to be homogeneous, although this is not the case in most natural slopes.

2.  Method of slices: In this procedure, the soil above the surface of sliding is divided into a number of vertical parallel slices. The stability of each slice is calculated separately. This is a versatile technique in which the non-homogeneity of the soil and the pore pressure can be taken into consideration. It also accounts for the variation of the normal stress along the potential failure surface.


Generally the factor of safety is defined as follows


The shear strength of soil consists of two components: cohesion and friction, and may be written as


 Shear strength, MPa

Normal stress on the potential failure surface, MPa

Friction angle, Degree