岩质边坡破坏机制有限元数值模拟分析

NUMERICAL SIMULATION ON FAILURE MECHANISM OF ROCK SLOPE BY STRENGTH REDUCTION FEM

岩质边坡的稳定性主要由其结构面控制,采用有限元强度折减法对岩质边坡破坏机制进行了数值模拟分析。计算表明,破坏“自然地”发生在岩体抗剪强度不能承受其受到的剪切应力的地带。分析表明,根据塑性力学破坏原理,采用有限元强度折减法有助于对岩质边坡破坏机制的理解。算例表明了此法的可行性。

The stability of rock slope is mainly determined by its discontinuity and rock bridge. The stability analysis of jointed rock slope is carried out by shear strength reduction finite element method. The elastic-perfectly plastic material is adapted in the finite element method. With the strength reduction, the nonlinear FEM model of jointed rock slope reaches instability, and the numerical non-convergence occurs simultaneously. The safety factor is then obtained by strength reduction algorithm. At the same time the critical failure surface and overall failure progress are found automatically. The numerical convergence or non-convergence is related to the yield criterion. The Mohr-Coulomb criterion is undoubtedly the best-known criterion. But its yield surface is an irregular hexagonal cone in principal stress space. For convenience the Mohr-Coulomb criterion is replaced by Mohr-Coulomb equivalent area circle yield criterion. Through a series of case studies, it is found that the safety factor obtained by strength reduction FEM with Mohr-Coulomb equivalent area circle criterion is fairly close to the result of traditional limit equilibrium method (Spencer's method). The result shows that the discontinuity coalescence pattern is influenced by its strength, length, location, and obliquity. The failure occurs naturally through the zone in which the shear strength of rock is insufficient to resist the shear stresses. This study presents a new approach for stability analysis of jointed rock slope, and it is especially available to the complicated geological condition and supported slope.