The Determination of Reduction Ratio Factor in Homogeneous Soil-Slope with Finite Element Double Strength Reduction Method

Even though there exist lots of documents on Finite Element Strength Reduction Method, cohesion and internal friction angle in these materials are reduced through the same reduction factor, which fails to reflect either of their safe reserving quality or the quality to precisely match slope failure process and mechanism. As is known, the exterior angle circumcircle yield criterion DP1 of the generalized Mises would cause larger slope stability factor in slope stability analysis, whereas inscribed circle yield criterion DP4 of the generalized Mises has higher precision for the plane strain problem. Since the ANSYS has only DP1 criterion, considering the DP4 yielding criterion's higher precision than DP1 in plane strain, the author first converts DP4 to DP1 that can be accepted by ANSYS, and then conducts separate reductions to cohesion and internal friction angle with different reduction proportionality factors according to double reduction factor method, and analyzes the calculation results afterwards. The results after analysis show that when cohesion and internal friction angle are reduced by reduction proportionality factor K=1.75, the failure characteristic of slope and attenuation specification of strength parameter match well to the real situation Therefore, reduction proportionality factor K =1.75 of cohesion and internal friction angle is typically recommended in homogeneous soil-slope.

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