Study On The Stability Calculation Of The Soil-rock Slope Combined With Morgenstern-price Method And Sarma Method

During the increase in the scale and the influence range of engineering construction in China, the stability of slope is having a much more great impact on economic efficiency and safety of constructions. Especially with the teeming of high and steep soil-rock slopes, a higher requirement of method and approach to compute the stability of slope has been raised. To ordinary soil-rock slope, there is a certain thickness of fully or strongly weathered rock formation on the rock strata. This weathered rock formation and different kinds of soil share a similar slide type which is suborbicular, while the slide type of the lower part which is Medium weathered and weak weathered rock depends on the type of the rock mass discontinuity, the occurrence of rock and lithology (Rock structure). Depending on different rock structures, the destruction of slope has been divided into seven categories by Chen Zuyu. On this basis, taking the boundaries of strongly weathered rock and Medium weathered rock as the boundaries of soil and rock, a landslide combined with a suborbicular slide of overlaying soil and a plane slide of underlying rock may occur, under the condition that plane sliding of underlying rock may occur.In view of the unique type of soil-rock slope landslide, according to this landslide type combined with a suborbicular slide and a plane slide, Morgenstern-Price method and Sarma method will be utilized together (as MP-S method) to analyze the stability of soil-rock slope. First, after predetermining the sliding surface (a), a new sliding surface (b) is set to meet the sliding surface (a) in the overlaying soil part, assuming only soil involved, and then the safety factor of sliding surface (b) is computable with Morgenstern-Price method. To search the most dangerous sliding surface (bm), above steps need to be repeated. Second, the forces on the boundaries of soil and rock can be obtained after the forces on the sliding surface (bm) in the overlaying soil part have been compensated. Then, sarma method can be used to compute the safety factor of underlying rock on sliding surface (c) which meet the sliding surface (a) in the underlying rock part, with the normal and the tangential forces on the boundaries of soil and rock as the external force of underlying rock. Generally, if the safety factors of soil and rock are not equal, the coefficient of coordinating force v can be used in iteration till the safety factors are equal, after the forces between soil and rock has been coordinated (setting coordinating force vW and coordinating moment Mc). Meanwhile, the safety factors of the whole sliding surface (a) and the sliding surface (c) are equal. Last, to search the most dangerous sliding surface (am) and calculate the safety factor of it, above steps need to be repeated with optimization method by assuming different sliding surface (a).Based on this, three tasks have been completed in this paper in order to raise a feasible method to compute the stability of soil-rock slope. They are the algorithm deduction of MP-S method, software programming and example computing to test the rationality of the algorithm.