应力波作用下含大型结构面岩体垮塌动力失稳机制

Dynamic collapse mechanisms of rock mass with large structural planes under stress waves

不连续结构面对爆炸应力波在岩体中的传播有很大影响,研究应力波作用下含大型结构面岩体动力垮塌失稳机制,为含结构面等地质构造条件下岩体开采及稳定性控制提供理论依据。以冬瓜山铜矿56–8#矿房采场回采诱发相邻56–7#矿柱采场垮塌为工程背景,建立结构面剪切滑移失稳力学模型,基于莫尔–库仑强度准则,采用理论分析方法计算了爆炸应力波通过结构面的透、反射系数,分析应力波通过结构面的应力响应特征;推导结构面发生剪切滑移的能量判据及应力判据,获得结构面的发生剪切失稳的条件。通过对结构面抗剪强度参数进行不断弱化,研究了微差爆破对结构面的破坏规律。研究表明:(1)入射角在一定范围内,反射波不发生相位延迟现象,并且在此入射角范围内,能量耗散系数大于0,结构面发生剪切滑移;(2)结构面是否发生剪切滑移失稳与结构面抗剪强度参数(内摩擦角、黏聚力)及应力波入射角、爆源距结构面距离有关;爆源距结构面的距离越远,结构面的抗剪强度参数越大,越不容易发生剪切滑移失稳。(3)微差爆破造成结构面强度参数不断弱化,使其发生剪切破坏变得容易,当结构面参数达到了发生剪切滑移的临界条件时,则56–7#矿柱采场发生垮塌。

Discontinuous structural planes have great influence on the propagation of explosion stress waves in rock mass,and studies on the dynamic collapse mechanism of rock mass with large structural planes under stress waves provide a theoretical basis for mining and stability control of rock mass under geological structure conditions. Based on the collapse of adjacent 56–#7 pillar stope induced by stoping in 56–#8 room stope of Dongguashan Copper Mine,a mechanical model of shear slip instability of structural planes is established. Based on Mohr-Coulomb strength criterion,the transmission and reflection coefficients of explosion stress waves passing through a structural plane are calculated by theoretical analysis method,and the stress response characteristics of stress waves passing through a structural plane are analyzed. The energy criterion and the stress criterion of shear slip are derived,and the condition of shear instability is obtained. By weakening the shear strength parameters of structural planes,the damage law of structural planes caused by millisecond blasting is analyzed. As is shown by the research findings:(1) when the incident angle is in a certain range,the reflected wave does not have phase delay,the energy dissipation coefficient is greater than 0,and the structural plane shear slip occurs,(2) the shear slip instability of the structural plane is related to the shear strength parameters(internal friction angle and cohesion),the incident angle of stress waves and the distance between the blasting source and the structural plane,and the farther the blasting source is from the structural plane,the larger the shear strength parameters of the structural plane and the less prone to shear slip instability,and(3) when the parameters of the structural plane reach the critical condition of shear slip,the stope of 56–#7 pillar collapses.