Influence of stress wave-induced disturbance on ultra-low friction in broken blocks

Abstract

Deep rock mass tends to be broken into blocks when mining for materials deep below the surface. The rock layer of the roof of the mine can be regarded as a system of blocks of fractured rock mass. When subjected to high ground stress and mining-induced disturbance, the effect of the ultra-low friction of the block system easily becomes apparent, and can induce rock burst and other accidents. By taking the block of rock mass as research object, this study developed a test system for ultra-low friction to experimentally examine its effects on the broken blocks under stress wave-induced disturbance. We used the horizontal displacement of the working block as the characteristic parameter reflecting the effect of ultra-low friction, and examine its characteristic laws of horizontal displacement, acceleration, and energy when subjected to the effects of ultra-low friction by changing the frequency and amplitude of the stress wave-induced disturbance. The results show that the frequency of stress wave-induced disturbance is related to the generation of ultra-low friction in the broken block. The frequency of disturbance of the stress wave is within 1–3 Hz, and significantly increases the maximum acceleration and horizontal displacement of the broken blocks. The greater the intensity of the stress wave-induced disturbance is, the higher is the degree of block fragmentation, and the more likely are effects of ultra-low friction to occur between the blocks. The greater the intensity of the horizontal impact load is, the higher is the degree of fragmentation of the rock mass, and the easier it is for the effects of ultra-low friction to occur. Stress wave-induced disturbance and horizontal impact are the main causes of sliding instability of the broken blocks. When the dominant frequency of the kinetic energy of the broken block is within 20 Hz, the effects of ultra-low friction are more likely.