含瓦斯煤岩剪切破断过程中裂纹演化及其分形特征

利用自主研发的含瓦斯煤岩细观剪切试验装置，开展了含瓦斯煤岩细观剪切试验，研究了煤岩剪切破断面裂纹的开裂扩展演化规律，并基于分形理论，分析了剪切破断面裂纹分布的分形特征。研究结果表明：含瓦斯煤岩剪切破断面裂纹的演化过程经历了5个阶段，即裂纹起裂、裂纹稳定扩展、裂纹非稳定扩展、剪切破断及裂纹摩擦阶段；含瓦斯煤岩剪切破断不同阶段的裂纹分布符合分形特征，且随着剪切应力水平的提高，含瓦斯煤岩剪切面裂纹分布的分形维数呈现上升趋势，通过剪切面裂纹的分形维数可定量描述含瓦斯煤岩随剪切应力状态变化的裂纹演化特征。

Fractal characteristics of crack evolution in gas-bearing coal under shear loading

A meso-shear test equipment was employed to carry out shear tests on gas-bearing coal and rock for investigating the production of cracks and their evolution law,as well as the fractal distribution characteristic of cracks.Based on fractal nonlinear theory,the crack distribution on the shear rupture face was studied.The results show that：the surface cracks’ evolution of gas-bearing coal and rock experiences five stages including cracks’ initiation,steady growth of crack,unsteady growth of crack,shear rupture and friction of materials.The distribution of cracks at the five stages has agreement with the prediction of fractal dimension theory.It is found that the fractal dimension of shear rupture surface cracks shows an increasing trend with the increment of shear stress.The evolution characteristic of cracks under variable shear stresses can be quantitatively described by the fractal dimension of shear rupture surface.