Abstract: The deformation and failure of rock masses are in general governed by the preexisting discontinuities and the local fissures induced by the state of stress, because these weak planes increase the deformability and reduce the strength of the rock mass. The mechanical properties of a rock system are thus determined by its interior structure and texture, as well as by the boundary conditions, such as the loading path, the constrained displacement and the geometry of the system.This paper describes a three-dimensional finite element model of the rock mass, where a fault underlain closely with or without a solf layer is dipping an angle of 60°or 90°between the fault plane and the horizontal axis. The external forces different in magnitude and direction are imposed at the boundaries, the effect of the intermediate principal stress, σ₂, on the concentrated stress level at the fault tip is studied as well.Numerical results similar to that of both the field and the laboratory tests confirm that present model provides physically measurful simulation and thus can be used to study the stress distribution of a geological body under different boundary conditions and thus to evaluate the geological background causing a huge earthquake.

摘要： 本文叙述一个既有断裂也有软层的三维有限单元数值计算模型,其中断层面倾角为90°或60°,作用力的大小和方向是变化的。特别着重研究中间主应力σ₂对断层端部的最大剪切应力的影响,也注意到软层的存在与否对整个应力状态和变形特征的作用。数值计算结果与现有的室内、室外实验结果非常相似,从而可以用来探讨复杂的地质体在不同边界条件下的应力分布和变化,以此评价地震发生的地质条件,可为中期地震预报提供线索。