Study On The Influencing Factors And Parameter Optimization Of Coal Body Caused By Carbon Dioxide Phase Change Blasting

In order to improve the effect of CO₂ phase change blasting on cracking and increasing permeability of high gas coal seam,taking the gas drainage of e2307working face of Gaohe mine as the engineering background,the main factors influencing the effect of CO₂ phase change blasting on presplitting and increasing permeability of high gas coal seam are studied from two aspects of coal properties and blasting parameters by using the research method of theoretical calculation,numerical simulation and field measurement The main results are as follows:?1?The effect of the existing phase change blasting scheme in e2307 face is analyzed.After blasting,the average concentration of gas extraction increased by12.1%;the pure volume of gas extraction increased by 17.9%;the concentration and pure volume of gas extraction increased by less,resulting in poor cracking effect,so it is necessary to further optimize the blasting antireflection scheme.?2?The attenuation law of explosion energy and stress wave of phase change explosion of liquid carbon dioxide is studied.Based on the thermodynamic characteristics of phase change blasting,the energy of phase change blasting is positively related to the blasting pressure and filling amount;the impact pressure of stress wave generated by carbon dioxide blasting decreases exponentially with the distance;the stress wave generated by the simultaneous initiation of two holes appears the phenomenon of stress superposition between adjacent crack causing holes,and the stress wave intensity between crack causing holes is greater than that of single hole initiation.?3?The main influencing factors and rules of CO₂ phase change blasting effect are analyzed.By using numerical simulation and orthogonal test method,from two aspects of coal properties and blasting parameters,the influence law and sensitivity degree of elastic modulus,Poisson's ratio,compressive strength of coal and on the effect of coal cracking caused by filling amount,blasting pressure and spacing of crack causing holes are studied.Among them,the influence of coal compressive strength and spacing of crack causing holes on the effect of phase change blasting is significant.?4?The parameters related to presplitting blasting in E2307 face were optimized.The parameters of CO₂ phase change blasting are optimized by numerical simulation,and the optimized scheme of cracking and permeability enhancement caused by liquid CO₂ blasting is put forward.Compared with the original scheme,the fracture development range of adjacent blast holes changed from about 3.1 m apart to the occurrence of through fractures.The increase of gas extraction concentration increased from 12.1%to 58.8%,and the increase of extraction purity increased from17.9%to 68.7%.The optimized scheme has achieved ideal cracking effect.This article has 63 figures,22 tables,86 references.