MULTI PARAMETER EVALUATION INDEX OF PROGRESSIVE FAILURE OF LANDSLIDE

The traditional strength reduction method (SRM) uses strength reduction to characterize the softening mechanical behavior of rock and soil after failure. The reduction coefficient is essentially a description of the overall stability coefficient of the slope, but its physical significance is not obvious. The stability of slope is a complex scientific subject related to many factors. When the local part of slope is in the state of failure stress, its whole failure may not happen, and the entire system composed of failure zone and non-failure zone is essentially in the state of an unstable mechanical state. It is difficult to obtain the real solution by the method of continuum mechanics. A multi- parameter evaluation index is put forward to describe the stability of the point, the surface (sliding surface) and body (sliding body) of slope. The definitions for point failure and surface failure (failure area ratio, failure stress rate, failure strain rate, etc.) are also presented. The different coefficients are developed, such as coefficient of frictional resistance, coefficient of normal force, coefficient of sliding force, coefficient of displacement along sliding surface, etc., for describing the law of force and displacement change. The safety factors of the entire slope are also clarified, such as surplus frictional resistance method, main thrust method, surplus frictional force method, comprehensive displacement method, surplus displacement method, and so on. It is possible to describe the all-round evolution process of slope by using the multi- parameter evaluation index. Under the condition of making full use of the partial strength reduction method (PSRM), or the perfect elasto-plastic model (PEPM), and the complete process constitutive model (CPCM), the multi parameters of point, surface and body of slope can be obtained with the change of displacement and force. Taking the traditional and extended unbalanced thrust method as an example, the progressive failure process of slope can be described by using the multi- parameters and can reveal the characteristics of the critical stress state movement step by step. The calculation results of Taohuashan slope in Huangshi City of Hubei Province show that: the multi parameter evaluation index can describe the evolution law of progressive failure of the slope, the values of the point and surface multi- parameters obtained by PSRM with the PEPM are smaller than that obtained with the CPCM; and the overall safety factors of the main thrust method, comprehensive displacement method and surplus displacement method using the PEPM are larger than that of the CPCM, but the stability coefficient of surplus frictional force method is opposite, etc. The focus of this study is to establish the slope multi-parameter stability evaluation index, and to make the traditional stability coefficient can be compared with the method proposed in this paper, which provides a theoretical support for slope monitoring and early warning.