压缩条件下岩石断裂模式与断裂判据的研究

Research on mode and criterion of rock fracture under compressive loading

针对岩石类材料压缩断裂中可能发生的Ⅰ型张拉断裂和Ⅱ型剪切断裂的现象 ,依据裂纹尖端应力集中引发的微裂纹损伤性质 ,提出了主裂纹尖端“微裂纹单元应力模型”的概念。通过对不同方位微裂纹尖端Ⅰ、Ⅱ型应力强度因子变化规律的研究 ,以比应力强度因子和比断裂韧度作为表征参数函数方程 ,提出了压缩条件下岩石类材料复合型裂纹断裂模式与断裂破坏的判据。该判据既可以预测岩石内部斜裂纹在压应力下的Ⅰ型扩展 ,也可以预测它的Ⅱ型扩展。由此判据 ,还给出了Ⅱ型断裂出现的条件 ,讨论了不同的影响因素。

In order to explain the mode Ⅰ and Ⅱ of rock fracture under compressive loading, a stress model of microcracking element is presented on the basis of damage properties in the tip of main crack. Through studing the distribution law of stress intensity factors of branching cracks in various orientation, a new criterion of fracture mode and failure of mixed crack of rock subjected to compressive loading, expressed by ratios of stress intensity factors and fracture toughnesses, is obtained, which can predict not only mode Ⅰ, but also mode Ⅱ of fracture. Based on it, the geometrical and loading conditions of mode Ⅱ of fracture are given and discussed in detail.The results are in good consistent with experiments.