Limit Equilibrium Global Stress Method For Slope Stability Analysis Under Tension Compression Shear Failure Characteristics

In order to overcome the limitations of the assumptions of the traditional limit equilibrium method,a new global stress method under the framework of limit equilibrium theory is established in this paper.In this method,the slope sliding body is regarded as a whole,the stress on the sliding surface is taken as the calculation core,and the assumed function with dimensionless variables is used to describe the stress distribution on the sliding surface.Then,the limit equilibrium state of the slope and the overall slope safety factor are solved by using the mechanical equilibrium condition of the sliding body.Furthermore,the heterogeneity,anisotropy and nonlinearity of rock and soil strength parameters and the unsaturated condition of soil are introduced into the limit equilibrium global stress method,which widens the application scope of the global stress method.Through the comparison and analysis of cases and examples,the feasibility and rationality of this method are verified.At the same time,the following main research results were obtained:(1)A reasonable stress distribution function of the sliding surface is constructed by using multiple unknown variables,and the stress constraints at the end of the sliding body are creatively introduced,which overcomes the problem that the traditional limit equilibrium method can not describe the progressive failure mode of the slope,the tensile stress zone at the trailing edge of the slope and the shear stress rise zone near the toe of the slope.Finally,the strict slope safety factor solution is obtained from the static equilibrium equation satisfied by the sliding body;(2)Based on the widely used Casagrande anisotropic model and heterogeneous model of soil strength,the anisotropic correction term and heterogeneous boundary conditions are introduced.The new model solves the problem that the existing anisotropic models lack universality or ease of use,and the problem of unlimited increase or decrease of soil strength under the existing heterogeneous models;(3)Taking the strength parameters of rock and soil as the carrier,the coupling calculation model of heterogeneous,anisotropic and nonlinear strength of rock and soil is completed.Then,by constructing a reasonable logical relationship,the calculation model is applied to the limit equilibrium global stress method,the slope stability solutions under nonlinearity,heterogeneity and anisotropy are obtained,and the applicability of soil strength nonlinearity in the limit equilibrium theory is solved;(4)In the general nonlinear Mohr Coulomb(M-C)strength criterion,the effective stress calculation formula of Lu and likos unsaturated soil and van Genuchten soil water characteristic curve are introduced to establish the effective stress calculation model of unsaturated soil shear strength under the nonlinear strength theory.It breaks the limitation of the application range of the traditional unsaturated soil strength calculation formula,can better simulate the shear strength behavior of fine-grained soil,and can show the "peak" phenomenon of unsaturated coarse-grained soil shear strength.