5.3 Stability analysis for Cohesionless Soil

In dry or drained sandy or silty soil, a stable bank can be designed based on the requirement that the bank angle be less than the angle of internal friction of the soil (Sherman, 1973). Usually the design is based on the factor of safety (FOS) that is calculated using the angle of the slope  and the angle of internal friction ф. The factor of safety then becomes:

Numerically, the value of FOS range between 1.0 to 2.0, with a commonly accepted design limit of at least 1.25 for non permanent slopes.