Theoretical And Experimental Studies On Coal Blasting Action Mechanism

Use of blasting technology to produce mutually penetrated crack in coal, then improve the gasdrainage rate, Shorten the drainage time, is the best radical measure for controlling gas accidents.Use the methods such as theoretical analysis, experimental research and numerical simulationcalculation. Author studied the coal blasting mechanism and crack expansion mechanism, theresearch findings have important scientific significance and wide application prospects in improvingthe coal seam gas drainage rate and preventing the outburst.Based on the investigation and analysis of coal’s physical and mechanical properties，thenature of project, and according to the country rock classification methods,author selected coalblastability and roadway stability as working index, the coal is divided into five categories, thatis,special hard coal, strong hard coal, hard coal, medium hard coal and soft coal. The coal simulationmaterial and proportion are determined by designing coal similar simulation test. Author analyzedthe action mechanism of the blasting stress wave, the detonation gas and coal mine gas in theory, anddivided the process of coal blasting damage and fracture into the initial stage of blast waves and thelater stage of the detonation gas and coal mine gas. Calculated the stress intensity factor of the initialmacro crack tip identified crack propagation and its fracture criterion at different stages under twokinds of loads. Based on the Taylor method, author defined blasting damage variable by initialdensity and damage density of coal, and studied the damage evolution equation, then determined theconstitutive equation of coal containing gas according to the effective stress principle, and finally,established the blasting damage model of coal containing gas. Author designed simulating coalblasting experiments, measured and statistical analyzed the explosive stress wave, ultrasonic wave,surface crack，the geometric parameters of blasting crater and the distribution of the fragments.Using the results of the experiments and test block blasting effect,studied on the law of blast stresswave’s propagation and attenuation, the law and mechanism of blasting damage, the effect ofdetonation gas and methane gas in coal blasting process, broken crater characteristics and coalblasting action mechanism. The test results verified the correctness and rationality of theoreticalanalysis. Finally, author established the blasting calculation model of coal containing gas using theDYNA software, and then calculated the explosive stress field, the calculation results agree well withexperimental results and the theoretical analysis results.The research findings have important scientific significance and wide application prospects in improving the coal seam gas drainage rate, provides theoretical and experimental basis for the Deepstudy on coal blasting mechanism.