Study On Improvement Of Instability Criterion Of Strength Reduction Method Based On Cluster-Change Point Analysis

With the development of China's social economy,many railway,highway and water conservancy projects have been put into construction,and a large number of engineering slopes have appeared.Slope instability often causes great economic losses and casualties,so slope stability analysis has become a very important subject in the field of engineering.The commonly used slope stability analysis methods include limit equilibrium method,limit equilibrium analysis method,strength reduction numerical simulation method and so on.Compared with the limit equilibrium method,the strength reduction method does not need to assume the sliding surface in advance.By reducing the strength parameters of the slope,the most dangerous sliding surface of the slope can be determined directly and the safety factor of the slope can be solved.However,when the strength reduction method is used for slope stability analysis,it is difficult to determine the criterion of slope instability failure.Therefore,an improved criterion of feature point displacement mutation based on the fusion of cluster analysis and change point analysis is proposed in this paper.In this method,the sliding body center is selected as the feature point,and the feature displacement mutation points are calculated by combining cluster analysis and change point analysis,so that the subjective factors in the traditional feature point mutation criteria can be reduced,and the criterion can be established on a more solid mathematical theory basis.The validity of the method is verified by a numerical example,and it is applied in a concrete project.The main work of this paper is as follows:(1)Based on numerical calculation,the displacement data of the slope node in the example was obtained.K-Meams clustering analysis method was used to separate the sliding body from the non-sliding body node,and then the coordinate of the sliding body node was calculated by centroid solution method,and the sliding body center was obtained as the feature point.Selecting the feature points can eliminate the influence of the whole sliding body rotating around the centroid on the displacement of the feature points,so that the selection of the feature points has a more specific physical significance.(2)Calculate the abrupt points of characteristic displacement based on cluster analysis and change point analysis,so that the identification of abrupt points is more objective and accurate:according to the same mesh division,the safety factor calculated based on the solution tool in FLAC^3Dsoftware is 1.07,and the relative error between it and the judging value is 0.07;The relative error between the calculation result and the judging value is 0.05,which verifies the objectivity of the method and the accuracy of the result.(3)Based on this study,the strength reduction method,cluster analysis and change point analysis were comprehensively used to solve the safety factor of the actual engineering slope and analyze the stability of the engineering slope.The applicability of the proposed method in slope stability analysis in practical engineering is further verified.At the same time,according to the calculation results,it provides a reference for stability monitoring in the later stage of the project.