Research And Application Of Double Strength Reduction Method

Traditional strength reduction method(SRM) adopts the idea that the reduction factors of the internal friction angle and cohesion are equal, which ignores the diffenence of formation mechanism of the internal friction angle and cohesion, in the last step, the safety factor is determined by reduction factors. This method provides only one critical point, which is hard to depict the slope stability better.Double reduction method(DRM) is a new slope stability analysis method, and this method considers that the reduction factor of cohesion is not equal to the factor of the internal friction angle, which is more rational than the traditional strength reduction method. There is a ratio of reduction factor K in this new method, it will lead to produce two starting ways of reduction for the same K, which produces the different paths of reduction. A finite element example’s calculation result shows that these two paths are united to one, and this difference of path doesn’t have influence on critical points. And the difference merely determines computational efficiency. Directly comparing the result of the traditional strength reduction method with the result calculated by the double strength reduction method can not reasonably reveal the essence and the property of DRM. Meanwhile, the essence of slope failure should be the strength wakening. As DRM is also belong to strength reduction technique, it should embody this essence. And the calculation value of DRM should not have an enormous devition. Using these two judgments can get a reasonable applicable scope of DRM. In the practical engineering, the factor of safety(Fo S) of slope is unique, but there are two reduction factors in DRM, which is a trouble for getting the Fos of slope. At present, in this new method, usually adopting the average value and the minimum value to determine the Fo S of slope. And these two ways are lack of theoretical basis, also are inconformable to actuality. Combining the concept of reduction path in the strength parameter coordinate system with the concept of strength area can define the expression of Fo S, which is more rational. For the same model of slope, when the slope is given various initial strength, parameters the critical points’ s distribution is not related to initial points, this distribution law is an innate attribute, which also conforms to the notion of yield criterion in plastic mechanic. The discrepancy of Fo S between DRM and SRM is determined by critical points, it needs to use the relative position of these points to evaluate the relationship of two methods.