压剪应力状态下岩石复合型断裂判据的研究

Research on combined fracture criterion of rock under compression-shear stress

考虑岩石闭合裂纹壁面间存在的摩擦力对裂纹尖端应力场的影响,应用最大周向应力理论得到压剪复合裂纹的断裂角。在此基础上,依据岩石裂纹尖端双向受力时的破坏特征,结合最大周向应力准则与修正的格里菲斯(Griffith)强度理论,建立了考虑摩擦效应的闭合裂纹失稳扩展的岩石压剪断裂判据。研究结果表明:断裂角受裂纹和荷载方向的夹角、裂纹壁面之间的摩擦系数、侧压力系数的影响;当压剪裂纹的断裂角是某个定值时,纯II型裂纹的断裂韧度与纯I型裂纹的断裂韧度的比值只与岩石裂纹表面的摩擦系数取值有关,而与其他岩石力学参数无关。此研究成果可为压剪应力作用下裂隙岩体的失稳破坏提供参考。

By considering the effect of friction between the crack surfaces on the crack-tip stress field, the fracture angle value of the compression-shear combined crack is deduced by using the maximum circumferential stress criterion. According to the failure characteristics of the crack tip of rock subjected to biaxial stresses, a compression-shear combined fracture criterion is proposed by combining the maximum circumferential stress criterion with the modified Griffith strength theory. The frictional effect of the closed crack propagation is also considered in the criterion. The calculation results show that the fracture angle is influenced by the angle between the crack and the loading orientation, the friction coefficient of the crack surfaces and the lateral pressure coefficient. When the fracture angle of the compression-shear combined crack is one specific value, the ratio of the fracture toughness of the pure mode-II crack to that of pure mode-I crack is only influenced by the friction coefficient of the crack surfaces. This study is essential for the research on the failure models of fractured rock mass under the combined compression-shear stress.