Aging induced effect of elliptic paraboloid zone in mining cracks and pressure released gas drainage technique

The physical similar simulation test and theoretical analysis were applied to study the dynamic evolution law and the morphological features of the cracks in the overburden strata under the different advancing speed. The study results showed that with the advancing speed of the coal mining face increased, the development height of the cracks in the overburden strata would be steadily decreased. Meanwhile,the scope of the compacted area would be relatively increased. Mainly the width of the compacted area would be increased with the advancing speed increased. Thus,the scope of the pressure released gas migration dominant channel would be decreased with the advancing speed increased. Based on the analysis on the test results, a mathematical expression equation of the mining crack elliptic paraboloid zone was established in consideration of the advance speed. A design was conducted on the layout layer of the high level gas drainage gateway in the fully mechanized coal mining face in a trial mine. The site test results approved the rationality of the high level gas drainage gateway according to the designed advancing speed of the coal mining face. Therefore,the certain theoretical basis could be provided to the layout and parameter optimization of the pressure released gas drainage system in the coal mining face with a high intensity advancing speed.