Research On Back-analysis Methods Of Slope Shear Strength Parameters

Landslide disaster restricts the sustainable development of economy and the society, but also brings a serious threat to people’s life and property. The frequency of the landslide and massive investment of reinforcement treatment fund make the study of landslide become a hot and also difficult problem. The shear strength parameters c and (p of rock mass are the foundation of slope stability analysis and treatment design of landslide, so that the determination of the shear strength parameters becomes the key to affect the reliability of slope stability analysis result. Therefore, it is of major practical significance to research on the determination method of the shear strength parameters c and φ for the analysis and design of slope engineering.If back analysis adopts different model of slope stability analysis, the back-analysis shear strength parameters will be different. Currently, the most commonly used method for slope stability analysis at home and abroad is the limit equilibrium slices method, of which the transfer coefficient method is the most widely used in slope with broken-line sliding surface. For back calculating the shear strength parameters c and φ with the transfer coefficient method presented in this paper, the vertical slicing slope model with broken-line sliding surface is studied, considering the influence of pore water pressure. In view of the upper bound theorem considering the stress-strain relationship of geotechnical material, with strict theoretical basis than the transfer coefficient method, this paper proposes a new back-analysis method based on the upper bound approach.Due to the vast majority landslide presenting three-dimensional configuration, and the three dimensional effect of part of the landslide is very obvious. While two-dimensional analysis is just approximate simulation of landslide action, ignoring the lateral restraint effect of landslide, so it cannot reflect the actual form of landslide. Therefore, this paper expands two-dimensional limit analysis to three-dimensional limit analysis, and the back-calculated shear strength parameters of both methods are compared.The traditional deterministic slope stability analysis methods fail to consider the influence of randomness and uncertainty of geotechnical parameters on slope stability, so this paper combines the probabilistic reliability theory with back analysis method, and then proposes a simple and practical new back-analysis method of slope shear strength parameters.Using Xiangxi zhuquedong landslide as engineering example, the back-analysis results based on two-dimensional and three-dimensional upper bound approach, probabilistic reliability method and the traditional transfer coefficient method have good consistency, and they also coincide well with the field survey test values that verify the validity of the proposed new back-analysis methods. Back-analysis result of three-dimensional upper bound approach is smaller than two-dimensional one, which reflects the lateral restraint effect of landslide and its back-analysis results are more a reflection of actual circumstances of the landslide.