A limit equilibrium approach is proposed to evaluate the stability of slopes with an installed wall such as a sheet pile wall . The uniqueness of this method is that different slip surfaces can be assumed in the upslope and downslope soil masses separated by the wall. A target value of the factor of safety is prescribed by the designer, contrary to the conventional slope stability analysis where factors of safety are generally unknown. Wall design is then carried out in order that the target factor of safety is actually achieved, though the design method for wall itself is not discussed in this paper . How to evaluate forces which the wall must sustain and to search for a pair of critical slip surfaces which are the most dangerous for the wall are presented . A number of examples show that this method provides reasonable solutions.

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The differential features of topographical factors such as slope gradient or slope curvature of surface sliding collapses due to torrential rainfall or earthquake have been reported. In this paper, to clarify the topographical features in order to establish an assessment method of the degree of slope collapse risk, we present the calculation method of local topographical factors using by the digital terrain elevation distributing with the irregular grid mesh. Obtained results reveal that slope collapses due to the earthquake occur intensity the convex slope curvature in contrast to the slope collapses due to torrential rainfall occurring in concave slope curvature. Also, the results point up that the slope longitudinal curvature rather than the traversal slope curvature is more useful factor to clarify the occurrence position of slope surface collapses.

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