Abstract: The main sliding direction is directly related to the slope stability evaluation and the determination of residual thrust force. At present, the sliding direction of the slope is mainly determined with semiempirical or empirical approach, such as whole vector direction of the displacements monitored inside the slope, parallel to the bottom of potential slip surface or the hypothesis made based on the failure mechanism of the slope. According to the principle of minimum potential energy, 2-D and 3-D sliding direction are rigorously deduced on the basis of current stress state of the slope. Moreover, this theoretical solution is verified to be rational by simple sliding block placed on an inclined plane and 3D slope examples. Besides, the curve of the sliding direction angle along the slip surface is also determined, which accurately supplies theoretical foundation to slope stability problem and the determination of residual thrust force.

Key words: main sliding direction, principle of minimum potential energy, slope stability