Evaluation of variables such as the soil stratification and its in-place shear strength may prove difficult. Water seepage through the slope and the choice of a potential slip surface add to the complexity of the problem. There are several different techniques used to help determine the safety factor of a slope. This sheet will introduce you to one of these techniques. One can model the slope failure as a 3-dimensional cylinder that rotates about a point in space called O .
Lets take a brief look at the theory of such an approach.
Figure 2 Both the soil cohesion and the weight of the soil W 2 produce another moment, M R , tending to resist failure. The moment causing the failure can be expressed as . The moment produced by the shear strength of the soil is and is in the counter-clockwise direction. For equilibrium to be maintained for every point O and radius r selected. The most probable slip surface can be determined by varying the position in space of point O and the radius r to obtain the largest c d required to maintain the above inequality.