Abstract: Most of the mountain highway waste soil disposal sites are in the valleys with complex terrain. If these disposal slopes are not handled properly, they will not only destroy the ecological environment but also threaten the life and property safety of downstream residents. Therefore, their stability needs to be evaluated. The “Y” shaped disposal slope of an expressway is selected for the evaluation. In order to overcome the deficiency of the conventional two-dimensional profile analysis in the evaluation of the global stability of the slope, a triangular prism solid model is constructed with the original surface as the potential sliding surface. The stability is analyzed by the three-dimensional limit equilibrium Hovland method. The results show that the topographic distribution characteristics such as the slope and the slope direction at different parts of the sliding surface of the “Y” shaped disposal site and the spatial relationship between the slope direction and the main sliding direction cause the stability of the triangular prism units at different positions on the sliding surface to be different. The distribution patterns of the triangular prism units with different safety factors constitute the sliding area and anti-sliding area. According to the characteristics of the valley waste soil on both sides of the “Y” shaped disposal site squeezing towards the middle, the global safety factor of the disposal site under the natural and rainfall conditions is further analyzed. The results can meet the requirements of the specification. Compared with the conventional two-dimensional limit equilibrium and the finite element numerical analysis methods, this method can intuitively obtain the global stability coefficient of the “Y” shaped disposal slope, provide a basis for the subsequent hazard mitigation.

Key words: Mountainous Expressway, Complex Terrain, Disposal Slope, Stability Evaluation, Three-Dimensional Limit Equilibrium Method