断续节理岩体破坏模式对强度特性的影响

为定量分析断续节理岩体破坏模式与强度的关系,基于离散元软件PFC2D标定了测试材料的强度包络线,并通过对不同节理倾角、排距和连通率的断续节理试样进行扩展数值模拟,研究了破坏模式对岩体强度特性的影响。计算结果表明,节理的倾角、排距、连通率均显著影响岩桥断裂机理,进而影响岩体强度和破坏模式;随着加载方向与节理夹角的减小、节理连通率或排距的增大,节理岩体的破坏模式逐渐由阶梯状张拉断裂转变为沿节理平面剪切断裂,张拉破坏的强度受排距的影响较大,而剪切破坏的强度受连通率影响较大;同时,破坏模式转变时的临界节理倾角αcrit与节理排距d、岩桥长度lr密切相关,其关系可用经验表达式αcrit=αcont-λlr/d来表示。

Influence of Failure Mode on Strength Characteristics of Intermittent Jointed Rock Mass

To represent failure modes of intermittent jointed rock mass,the PFC2D were employed to study the mechanical behavior of intermittent jointed rock mass by setting orientation,space and persistence ratio of joints to different values,after the mechanical properties as well as strength envelop of test material were well calibrated.The influence of failure mode on strength characteristics of intermittent jointed rock mass was analyzed.The results show that the orientation,space and persistence ratio of joints significantly affect the fracture mechanism of rock bridge and further the strength and failure mode of rock mass.With the decrease of the angle between loading direction and joint orientation and the increase of persistence ratio or space of joints,the failure mode gradually transforms from tensile fracture along the step path to shear fracture along the joint plane.Besides,the tensile failure strength is greatly affected by the space of joints,while the shear failure strength is greatly affected by the persistence ratio of joints.At the same time,the critical joint orientationαcritof failure mechanism transformation is closely related to joint space dand rock bridge length lr,and satisfies an empirical expression,αcrit=αcont-λlr/d.