Effect Of Mining Speed On Rock Burst On Fully Mechanized Caving Face In Mengcun Coal Mine And Its Dynamic Control Method

Taking the typical rockburst mine Mengcun Coal Mine as the engineering background,this paper systematically studies the overburden structure characteristics,migration law,and mine pressure behavior characteristics under different mining speeds in the mining process,reveals the mining speed effect of rockburst,and puts forward the dynamic regulation technology of mining speed based on the research.The main conclusions are as follows:(1)Aiming at the characteristics of comprehensive mining of thick coal seam in Mengcun coal mine,a cantilever beam model with triangular pressurized load distribution was established,and the influence of key mechanical parameters controlled by mining speed on the sinking displacement,bending moment,and elastic energy of the roof was theoretically studied.The accelerated mining speed of the working face would cause the overhanging roof area to increase and the over-support pressure to be more concentrated,thus increasing the bending moment and elastic energy of the roof.(2)A similar simulation experiment revealed the laws of overburden fracture and energy release in 401102 working face under different mining speeds.It was concluded that the acceleration of mining speed led to the increase of overburden collapse height and collapse range on the one hand,and the greater the elastic energy released at the moment of periodic exercise of the roof and critical layer on the other hand.And the greater the total energy of microseismic and acoustic emission events,the risk level of strong impact accounts for an increasing proportion.(3)The relationship between mining speed and loading rate was clarified,and the damage deformation characteristics and energy dissipation evolution law of coal samples under loading rate were investigated by numerical simulation,and it was concluded that the faster the loading rate,the higher the degree of fragmentation of coal samples,the larger the local energy release rate(LERR)value and the more the number of large energy release rate events.In addition,the faster loading rate caused the microcracks that can be induced at low strain rates to develop too late,resulting in a significant decrease in the acoustic emission signal.(4)Numerical simulation was used to dynamically evaluate the impact hazard of the working face at different mining speeds.The results showed that the stress concentration phenomenon and energy accumulation phenomenon of the roof plate was more obvious when the mining speed was accelerated,resulting in a higher impact hazard,and point out that the advancing speed of the working face of 401102 should not exceed 4.0m/d.(5)Microseismic warning indexes were given for different levels of the risk status of the retrieval working face,and the reasonable mining speed of the working face was classified by analyzing historical microseismic monitoring data at different mining speeds of 401101 working face,and the effect of mining speed regulation was tested by microseismic monitoring.This study provides a reference for the selection of reasonable mining speed in the mining face of rock burst coal mine.