Experimental Study On Influence Of Stress Wave Disturbance On Anomalously Low Friction Effect Of Block Media

With the increase of mining depth,the deep rock mass tends to break the block medium.Under the conditions of high ground stress and mining disturbance,the anomalously low friction effect of the block rock mass is easy to occur,and the rock burst is induced.Considering the actual working conditions between the sandstone roof,the roof-coal-floor,the deep rock mass,the roadway and the overlying rock layer.Taking the block rock mass as the research object,the anomalously low friction effect of different lithology,heterogeneity,different height and water-bearing block under stress wave disturbance condition was studied by self-developed anomalously low friction test device.Axial pressure,horizontal impact and vertical stress wave disturbance were applied to the block rock mass to simulate the stress environment where the rock was located.By changing the frequency and amplitude of stress wave disturbance,the residual vibration and horizontal acceleration of the working block were used to characterize the anomalously low friction effect intensity of the block,and the complete sandstone block,coal-rock combination block,two parallel jointed sandstone blocks,and four parallel joints were analyzed.The strength on anomalously low friction effect and block energy of sandstone block,sandstone block with pores and sandstone block and water-bearing sandstone block with different heights were analyzed.The conclusion of the study provides an important scientific reference for the understanding of the anomalously low friction effect of the block rock mass.Research indicates:(1)The influence of stress disturbance on the strength of anomalously low friction effect of block rock mass was analyzed.The frequency of stress wave disturbance has a strong and weak interval on the anomalously low friction effect of the block.When the frequency of stress wave disturbance was in the low frequency range of 1~3Hz,the residual displacement and the intensity of the anomalously low friction effect of the block increases.The strength on anomalously low friction effect of the block increases with the increase of the intensity of stress wave disturbance.The residual displacement and horizontal acceleration maximum of the four parallel joint blocks increase exponentially with the increase of the intensity of stress wave disturbance.(2)The influence of the lithology and heterogeneity of the block under the stress wave disturbance of the intensity on anomalously low friction effect of the block was analyzed.Under the same horizontal impact load,the anomalously low friction effect of the block from the strong to the weak is four parallel joint sandstone blocks,a hole-containing sandstone block,a coal block,two parallel joint sandstone blocks,and a complete sandstone block.(3)The influence of the height and water content of the working block under the stress wave disturbance on the intensity of anomalously low friction effect was analyzed.The smaller the height of the working block and the higher the water content,the greater the strength on the anomalously low friction effect of the block.(4)The kinetic energy and power spectral density characteristics of the working block under stress wave were analyzed.Kinetic energy of block has agglomeration effects and short-term peak characteristics.The energy spectral density curve accumulates in the low frequency region,and the high frequency region attenuates.When the block was subjected to horizontal impact of 2.5MPa,the extreme frequency of power spectral density was within 10 Hz;...