Research On Attenuation Law Of Vibration Energy In Rock Mass And Scale Of Roof Presplitting In Rockburst Coal Mine

As a dynamic failure process,rockburst releases the energy accumulated in the coal and rock in a flash,which poses a serious threat to the life safety of workers and the safe and efficient production of coal mines.When the energy accumulated in the coal and rock mass increases significantly and reaches the critical equilibrium state of the geological body,effective prevention and control measures must be taken to ensure the safety of coal mining and other activities.In this paper,Midas blasting numerical method is used to simulate the change of energy behind roof collapse in coal and rock mass,and the energy attenuation law is obtained.The influence weight of mechanical parameters of coal and rock mass affecting energy attenuation is calculated by using Matlab analytic hierarchy process,and then the calculation formula of rock mass vibration energy attenuation is obtained.The attenuation law of vibration wave signal is verified by laboratory test with VM-2000 rock mass vibration detector.Combined with the microseismic monitoring data of a mine in Shanxi Province,the attenuation coefficient is verified on site.The mechanical parameters of the roof rock samples taken from the 8005 working face of the mine are tested.The attenuation law of the energy signal is obtained through the change of the strength of the signal captured by the sensor.The attenuation coefficient of the energy is calculated according to the attenuation law of the energy,and then the accuracy of the calculation formula of the energy attenuation of rock mass vibration is verified.Based on this,the instability of the roof rock layer of the 13230 working face in the rockburst mine-Gengcun Coal Mine is determined in advance,and the pre-cutting scale is determined,which provides theoretical support for the targeted implementation of rockburst prevention measures in Gengcun Coal Mine.The research results show that the attenuation coefficient of vibration energy in coal and rock mass is affected by the mechanical parameters of rock mass such as elastic modulus,Poisson’s ratio,unit weight,friction angle,void ratio and cohesion.Among the influence weights of various mechanical parameters,Poisson’s ratio accounts for 0.3838,elastic modulus accounts for 0.2558,void ratio accounts for 0.1719,unit weight accounts for 0.0963,friction angle accounts for 0.0580,and cohesion accounts for 0.0342.According to the calculated attenuation coefficient,the roof cutting scale of 13230 roof strata in Gengcun Coal Mine is calculated:if the release energy of the initial instability of the roof strata is controlled below 10~6 J,the roof shall be pre-cut at the interval of 30 m in the middle hard strata and 50 m in the low hard strata.If the energy released from the initial instability of the rock stratum is controlled below 10~5 J,the top of the middle hard rock stratum is pre-cut at an interval of 20 m,and the top of the low hard rock stratum is pre-cut at an interval of 30 m.If the energy released from the initial instability of the rock stratum is controlled below 10~4J,the top of the middle hard rock stratum is pre-cut at an interval of 12m,and the top of the low hard rock stratum is pre-cut at an interval of 20m.If the release energy of periodic instability of rock strata is controlled below 10~6 J,the medium hard rock strata and low hard rock strata may not be pre-cut.If the release energy of periodic instability of rock strata is controlled below 10~5 J,the mid-hard rock strata can be pre-cut at 39.3 m intervals,and the low-hard rock strata can be pre-cut at 25.5 m intervals.If the release energy of periodic instability of the rock stratum is controlled below 10~4 J,the mid-hard rock stratum can be pre-cut at an interval of 30 m,and the low-hard rock stratum can be pre-cut at 20 m.Therefore,study the dissipation and attenuation law of the energy behind the roof collapse,calculate the instability and energy release of the rock strata,and effectively control the rock burst by optimizing the parameters of preventive measures such as pre-cutting according to the research results.In this paper,there are 51figures,27tables and 73references...