A GIS-based method for locating the critical 3D slip surface in a slope

The minimum safety factor and the critical slip surface of a slope can be located using various methods of optimization or random search. However these methods have not been adopted to search for the three-dimensional (3D) critical slip surface. This paper proposes a new Monte Carlo random simulation method to identify the 3D critical slip surface, in which assuming the initial slip as the lower part of an ellipsoid, the 3D critical slip surface in the 3D slope stability analysis is located by means of a minimization of the 3D safety factor. Based on a column-based three-dimensional slope stability analysis model, a new geographic information systems (GIS) grid-based 3D deterministic model has been developed to calculate the 3D safety factor. Several practical cases, of known minimum safety factor and its critical slip surface by using a two-dimensional (2D) optimization or random technique, have been extended to 3D slope problems to locate the 3D critical slip surface and to compare with the 2D results. As another 3D case, a multi-strata slope, considering the effect of a fault and the underground water, is used to demonstrate the efficiency and capability of the proposed method. Compared with the 2D result, the resulting 3D critical slip surface has no apparent difference for simple slope geometries, but the associated 3D safety factor is definitely higher. (C) 2004 Elsevier Ltd. All rights reserved.