Stability of Slopes by Logarithmic-Spiral Method

A logarithmic-spiral method programmed for a computer is presented for determining the factor of safety of a simple slope. The method differs from Taylor's in that the friction angle of the logarithmic spiral is not a constant but varies with the factor of safety. The method yields a factor of safety with respect to strength, instead of that with respect to cohesion. Furthermore, the inability of Taylor's method to obtain a factor of safety, when the slope angle is smaller than the angle of internal friction of the soil, is circumvented. The result of this study shows that the factor of safety for a simple slope can be determined effectively by the logarithmic-spiral method. It was found that the factor of safety obtained from the logarithmic-spiral method checked closely with that from the ICES-LEASE computer program, based on the simplified Bishop method, as well as from the finite element program developed by the U.S.Bureau of Mines.