高应力硬岩开挖扰动的能量耗散规律

Energy dissipation of high-stress hard rock with excavation disturbance

基于离散元PFC 2D软件建立的深部岩体模型,根据巷道围岩的可释放应变能、岩石耗散能以及岩石颗粒总动能的能量,描述深部硬岩的能量耗散和释放规律,揭示深部能量演化机制。研究结果表明:所建立岩体离散元模型及微观参数能有效反映深部开挖应变能释放规律;当侧压系数λ=2.1时,高地应力作用下巷道围岩的破裂形式以集中于巷道顶底板位置的拉伸破裂为主,破裂区域随采深增加而增加,破裂面积以圆形断面最小;开挖卸载后的能量演化是一个动态调整的过程,巷道附近围岩的应变能积累较动能释放有约2.5 ms的滞后;开挖后岩体后续应变能的积累量远大于巷道围岩总释放动能与总耗散能之和,约为两者之和的10倍,这也是开挖扰动容易引起围岩破裂的重要原因之一;岩体的总耗散能主要用于岩体颗粒间裂纹的萌生、扩展及贯通,裂纹总数和岩体总耗散能表现出极好的线性相关关系。

Based on a rock mass model established by the DEM software PFC 2D in deep mine, energy tracing logic was triggered to monitor releasable strain energy, dissipated energy and total kinetic energy of rock particles in the tunnel surrounding rock, so as to describe energy dissipation and release principles of deep hard rock, and reveal energy revolution mechanism in deep mine. The results show that the established rock mass model and its micro-parameters can successfully reflect strain energy release rules of excavation in deep mine. When horizontal pressure coefficient is equal to 2.1, the principal failure mode of tunnel surrounding rock under high-stress turns to tensile damage concentrated on tunnel roof and floor, and fracture area increases with the increase of mining depth, but different shapes of tunnel have different damage areas, which is the minimum for circular cross section. Energy evolution after excavation is a process of dynamic adjustment, in which strain energy accumulation of tunnel surrounding rock has a delay of 2.5ms compared to kinetic energy release. The strain energy accumulated after excavation are about a tenfold of the sum of total released kinetic energy and total dissipated energy in tunnel surrounding rock, which can account for the fracture of surrounding rock due to excavation disturbance. Total dissipated energy of rock mass is mainly used to conceive, expand and connect cracks in rock particles, and the cracks development presents a great linear relationship with total dissipated energy evolution.