Research On The Stability Of Homogeneous Soil Slope Based On Shear Strength Reduction

Compared with the conventional limit equilibrium method and the limit analytical method, the finite element method based on shear strength reduction (SSR) technique has many evident advantages in analyzing the stability of slope. The primary advantage of the SSR is that it can obtain the most dangerous slip surface and the corresponding safety factors of the slope without predetermining the shape and location of the slip surface , but only by reducing the shear strength parameters of the rock and soil of the slope continuously until the shear stress exceeds the shear strength and consequently result in the failure of the slope. However, there are also many problems of the SSR. In order to solve above problems and deeply investigate the SSR, this thesis mainly takes the homogeneous soil slope as case studies , and analyzes their stabilities by making use of the SSR. Some useful conclusions and improved measures are as follows:①This paper proposes a new transform formula between any different yield criterions based on Drucker-Prager(D-P) criterions according to their semidiameter of projection circles on theπPlane. The ratio of the semidiameter of the projection circles on theπPlane of different D-P yield criterions is equal to the ratio of their corresponding safety factors. Because the ratio is only relative to the friction angle of the soil, this paper lists the transform tables about the frequently used friction angles and their corresponding safety factors under different D-P yield criterions, so that the safety factors of the slope can be found conveniently through the tables when different D-P yield criterions are employed in analyzing the stability of the slope in ANSYS.②This paper compares the results of different D-P yield criterions under three diffirent calculated conditions, and the conclusions indicate that it is more appropriate to take the D-P yield criterion which is matched by the Mohr-Coulomb criterion under the plane strain condition as the yield criterion of the homogeneous soil slope.③One of the most important problems to analyse the stability of slope with the finite element method based on SSR technique is how to evaluate whether the slope is steady or not according to the result of FEM. This paper discusses three common criterias(the convergence of numerical computaions, the connectivity of plactic zone and the abruptness of the displacement or deformation at a certain characteristic location) and proposes an improved method based on the abruptness of the displacement or deformation at a certain characteristic location: this paper makes research on the maximal horizontal displacement, and obtains the safety factor of soil slope with the new curve of the ratio of the maximal horizontal displacement increment△S and strength reduction coefficient incremen△Fs and strength reduction coefficient Fs instead of the curve of the maximal horizontal displacement Smax and strength reduction coefficient Fs. The new curve can show the essence of SSR technique more clearly, and also can make the solution more exact and easy, and finally prove it feasible with some examples of application.④Different calculating parameters have various influences on the analysis accuracy of slope stability: First, the variation of cohesion C and friction angleφaffects the analysis results evidently, and the the variation of E andνaffects the analysis slighty ,which can nearly be igored.However,the value of E can't be too little, or it will cause too large value of deformation of the slope, which results in the divergence of numerical analysis and affects the safety factor accurately.In case of no practical data, it's better for the Young's modulus E to be greater than equal to 1.0Mpa.