RE-APPRAISAL OF JANBU'S GENERAL PROCEDURE OF SLICES.

The method of slope stability analysis most commonly used in Hong Kong is the General Procedure of Slices developed by N. Janbu. It is generally believed that the method is most suitable for analyzing the shallow type of slope failures which occur frequently in Hong Kong. The objectives of this paper are: to demonstrate that Janbu's procedure is numerically not as stable as is commonly believed; and to present a new derivation of the method of N. R. Morgenstern & N. E. Price (M&P). In contrast to the conventional procedures of Janbu and of M&P, the proposed method eliminates iteration in the calculation of the factor of safety F. The formulation of the proposed method is easier to understand and program than the original formulation by M&P. A simpler method is also used to replace the Newton-Raphson numerical technique in calculating the factor of safety and the constant lambda .