Abstract: A discrete crack model for the strain accumulation of the Tangshan rhombic block, as well as slip and stable extension of the earthquake fault prior to and during the 1976 Tangshan earthquake, is presented. It includes two processes: frictional slip along the crack surface and stable extension of the crack tips. The Finite Element Technique is used to calculate stress and deformation along the crack surface and stress intensity factors at the crack tips, and the Mohr-Coulomb principle is applied to judge the existence of frictional slip along the crack surfaces, while the extension direction of the crack is determined by using the maximum circumferential tensile stress criterion. The similarity between the data predicted by the model and those obtained from field observation indicates that the crack model has successfully simulated the process of strain accumulation and fracture propagation prior to and during the Tangshan earthquake.

Key words: Crack model, Stability extension, Maximum circumferential tensile stress criterion, Double point, Special triangular quartepoint crack tip element

摘要： 本文提出唐山菱形块体在压缩载荷作用下震前应变积累和震时破裂滑动与稳定扩展的一个离散裂纹模型,它包括裂纹面的摩擦滑动和裂纹尖端稳定扩展两个过程。模型采用有限单元技术计算裂纹面的应力和变形及裂纹尖端的应力强度因子,并用库伦-纳维准则判断裂纹面是否发生摩擦滑动及用最大周向拉应力准则判断裂纹尖端扩展方向。模型预测与野外观测资料对比指出:裂纹模型能很好的表示1976年唐山地震震前积累和震时破裂传播的过程。

关键词: 裂纹模型, 稳定扩展, 最大周向拉应力准则, 双节点, 四分之一节点特殊单元