抄録
Some of the limit equilibrium methods of slices commonly used for computing the factor of safety are the Fellenius method, the simplified Bishop method, the Janbu method, the Spencer method (1967, 1973) and the Morgenstern-Price method. In these methods, the Spencer method (1973) and the Morgenstern-Price method are called the general limit equilibrium method of slices that satisfy both moment equilibrium and forth equilibrium of the slices contained above an assumed slip surface. These method are applicable to general slip surfaces. As it is desirable to use the accurate method in order to accumulate the case histories, Morgenstern-Price method that is considered to be reasonable is often utilized for analyzing the stability of slopes. However, this method has. spread only to a few Institute in Japan because of it's difficulty and complexity.
On the other hand, the Spencer method (1967) is the simple one that satisfy moment equilibrium and forth equilibrium of the slices, but it is applicable only to the circular slip surface. This method become to be applicable to general slip surfaces by modifying the equation of moment equilibrium of the slices above a slip surface. The modified equation is ∑ QR cos (α-θ+γ)=0 (Fig. 8).
It is shown that the factor of safety computed by the modified Spencer method (1967) is equal to that of Spencer method (1973) for two cases.
