STABILITY ANALYSIS OF LANDSLIDE USING JOINT FORCES METHOD ON MULTIPLE PROFILES

The accuracy is the most important in stability analysis of a landslide. Both the sliding plane and the slope surface are three dimensional, resulting in great spatial variation of thicknesses of the sliding body. The analysis of slope stability is usually carried out by calculating the factors of safety along the"representative longitudinal profile" of the central axis or nearby profile. Because the calculation uses a unit width, the results can only represent the local stability of the slope within small widths on both sides of the selected profile in most cases, but not the stability of the entire landslide. Therefore a multi-profile joint forces method is proposed to assess the stability of a landslide. To reduce the man-power and cost for multi-profile exploration of a landslide, the sliding surfaces are classified into two categories:simple slip surface and complex slip surface. For a simple slip surface, it is required to have a minimum of two profiles with a total of 2 to 4 boreholes. The multiple longitudinal profiles required for calculation are then delineated through drawing the auxiliary cross sections by using several curve functions of the slip surface. The multi-profile joint forces method is based on parallelogram law for addition of forces. Each profile is first divided into slices. The shear forces and resistance forces of each slice are then converted to horizontal and vertical components on each slice of a profile. The horizontal and vertical resulting forces along each profile are determined by adding the horizontal and vertical shear forces and resistance forces on all slices, respectively. The resulting joint sliding force and resistance forces on all profiles are used to calculate the sliding and resistance forces of the entire landslide. Their ratio(resistance force vs.sliding force)-the safety factor of the landslide are calculated at the end. Two case studies of landslides, one with a simple slip surface and another with a complex slip surface, are used to validate the method.