关于有限元边坡稳定性分析中安全系数的定义问题

在边坡稳定性分析的极限平衡法中存在3种安全系数的定义:定义1将安全系数定义为剪切强度比剪应力;定义2将安全系数定义为强度储备系数,当土体抗剪强度除以安全系数后,边坡将处于临界平衡状态;定义3将安全系数定义为沿某一特定滑面的抗滑力比滑动力。讨论了定义3与定义1之间的关系,给出了在进行有限元边坡稳定性分析时确定对应于定义3和定义2的临界滑面的统一算法,最后通过算例证明了一般情况下基于定义3所求得的安全系数和临界滑面不同于基于定义2所求得的结果,同时指出基于定义3的计算结果会表现出一些不合理的现象。

ON DEFINITIONS OF SAFETY FACTOR OF SLOPE STABILITY ANALYSIS WITH FINITE ELEMENT METHOD

There exist three definitions of safety factor in slope stability analyses by limit equilibrium methods (LEM). Definition 1 defines the safety factor as the ratio of the shear strength of soil to the shear stress required for equilibrium. Definition 2 defines the margin of safety factor as the factor of the strength reduction,by which the shear strength of the soil would have to be divided to bring the slope into a state of critical equilibrium. Definition 3 defines the safety factor as the ratio of the resistant shear force to the driving shear force along a certain slip surface. This study discusses the relation between Definition 1 and 3. A unified algorithm is given,which is used to locate the critical slip lines corresponding to Definition 3 and Definition 2 respectively. It is also proved while the finite element method is used to analyze slope stability,both the safety factor and the potential slip surface based on Definition 3 are different from those on Definition 2. Some irrational results might be obtained if Definition 3 is used in finite element slope stability analysis.