关键词: 岩石力学, 块系岩体, 摆型波, 超低摩擦

Abstract:

When rock burst occurs in deep coal mine, there is a significant phenomenon of rupture in coal and rock mass. Based on the theory of pendulum-type wave's propagation in the block rock mass, the mechanism of anomalously low friction between rock blocks is studied. Block rock mass is composed of rock block and the weak medium between rock blocks. The law of anomalously low friction in rock mass is studied by maximum value of relative displacement between rock blocks under dynamic action. The soft medium between rock blocks has periodic tensile and compressive variations under the effect of blocks during pendulum-type wave's propagation in block rock mass. When relative displacement of soft medium between rock blocks reaches the maximum value in the tensile direction, the adjacent blocks would show an obvious separation state. At this time, positive pressure between rock blocks is small relatively and rock block is easy to slide under lateral force in the mechanism of anomalously low friction between rock blocks. As a result, the criterion for block rock mass' anomalously low friction is put forward. Based on the dynamic model of pendulum-type wave's propagation, this paper analyzes the relative displacement between rock blocks under the effect of various external perturbations including the transient perturbation and periodical perturbation, as well as the transient state response and steady state response of block rock mass. The effect of mass of local block and viscoelasticity property of soft medium between rock blocks on the relative displacement between local rock blocks is calculated. When the viscous coefficient in block partings increases or the mass of rock block decreases, the maximum tensile value between rock blocks decreases, at this moment, the anomalously low friction does not act easily. However, when the elasticity coefficient in block partings decreases, the maximum tensile value between rock blocks increases obviously, at this moment, the anomalously low friction acts easily. Meanwhile, the effect of external disturbance property on anomalously low friction in rock mass is analyzed. Changing external disturbance frequency will lead to change of maximum tensile value between rock blocks, which will rise sharply at the disturbance frequency close to the quasi-resonant frequency and decline gradually at the disturbance frequency far away from the quasi-resonant frequency. It is important for understanding the laws of fault movement type rock burst through the analysis of the anomalously low friction mechanism of rock mass based on propagation of pendulum-type waves.

Key words: rock mechanics, block rock mass, pendulum-type waves, anomalously low friction