Research On The Destruction Mechanism Of Coal Rock Body Under The Action Of Liquid Carbon Dioxide Blasting

CO₂ pre-splitting blasting is one of the key research directions in the"Twelfth Five-Year Plan for Coal Science and Technology"as the key technology for efficient gas permeability enhancement in coal mines.In order to explore the reasonable mechanical model and parameters of coal and rock masses,and to determine the actual effect and cracking range of liquid CO₂ blasting,this paper relies on the CO₂ blasting and mining of a mine in Shenmu,northern Shaanxi,and uses the coal and rock of this mine as the research object to carry out mechanics,the mechanical property test and Split Hopkinson Pressure Bar?SHPB?test are carried out.Based on LS-DYNA^3D numerical simulation test platform,the HJC model is determined by orthogonal test method By numerical simulation,the characteristics of liquid CO₂ blasting are analyzed,the range of crushing area and fracture area is given,and the reasonable spacing of 38 type liquid CO₂ blasting is determined.It has been applied to engineering practice and achieved good results.The main research contents are as follows:?1?The uniaxial compression test,Brazilian disc splitting test and SHPB impact compression test were carried out on coal and rock respectively by using stress loading system and SHPB device to determine the basic mechanical parameters of coal and rock,study the deformation and failure characteristics of coal and rock under static and dynamic load,and analyze the dynamic and static characteristics of coal and rock.?2?According to the test data,on the basis of the empirical range value,based on the LS-DYNA^3D numerical simulation test platform,the whole process of SHPB impact compression test is reproduced.The person correlation coefficient is used to determine the consistency between the simulated strain signal and the test strain signal.The values of the limit surface parameters B and N of the Holmquist-Johnson-Cook?HJC?model of coal rock were determined.Based on the HJC model,the dynamic failure characteristics and damage evolution process of coal rock were studied through numerical simulation experiments.?3?According to the determined HJC model parameters of coal and rock,a liquid CO₂blasting model is established to simulate the blasting process of the 38-type fracturing device,and the crack expansion characteristics and stress wave attenuation law of the original explosive blasting and liquid CO₂ blasting are compared and analyzed,and the range of crushing area and fracture area of the liquid CO₂ blasting is determined.?4?According to the numerical simulation results,the effective cracking range of the38-type fracturing device is 0.6?0.8m.According to this,the designed blasting hole distance and row distance are both 0.7m in the industrial test of Shenmu mining area in Northern Shaanxi,which has achieved good mining results,and the lump coal rate has increased by38.5%compared with explosive blasting.