Abstract
Safety calculation methods of slope were presented more than 70 years ago and various methods have been presented in the past. Slip surface of the safety factor calculation method of slope practically adopted assumed to be circular. Because it has small number of parameters, simple algorithm, efficient and high computation stability. On the other hand, one of the safety factor calculation methods of slopes with non-circular slip surface is Spencer method, which has complex algorithm and low computation stability. In this research, factors of computation instability in the safety factor calculation of slope by Spencer method were revealed and improved algorithm of the safety factor calculation method with high computation stability was presented.
