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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。
This paper presents a discrete crack model of Tangshan diamond-shaped block under pre-earthquake strain accumulation and pre-earthquake rupture sliding and stable expansion under compressive loading. It includes two processes of frictional sliding and crack tip stability expansion. The finite element method was used to calculate the stress and deformation of the crack surface and the stress intensity factor at the tip of the crack. The Coulometric-Navier criterion was used to determine whether there was frictional sliding on the crack surface and the crack tip propagation direction was determined by the maximum circumferential tensile stress criterion. The comparison between the model prediction and the field observation data shows that the crack model can well represent the process of the 1976 Tangshan earthquake bursting before the earthquake and the earthquake rupture propagation.