Determination on rational layer position of high level gas drainage gateway for high gassy fully- mechanized top coal caving mining face

In order to solve the problems of high gas emission from the high gassy area of the goaf in No. ZF301 coal mining face of Xiagou Mine and the frequent over limit of the air flow in the coal mining face and the gas at the top corner, based on the " O" ring theory of mining overburden strata failure, a control method of the h igh level gas drainage gateway set in the roof was provided. With the theoretical calculation, the height of the cracking zone in the roof strata obtained was 47.03 ~ 58. 23 m. Fluent numerical software was applied to simulate the drainage effects of the high level drainage gateway at three different vertical distances of 45, 55 and 65 m. . The drained gas density obtained from the high level drainage gateway at 55 m layer position was maximum and the gas volume fraction at the top corner was minimum and would be below 1%. At the mine site, the high level drainage gateway was set in the 50 m layer position. During the normal mining period, the average gas drained pure volume was 31.58 m3/min and taken 69.74% in the absolute gas emission volume percentage of the coal mining face. Thus, the gas volume released the mine ven tilation was reduced to 4.79 m3/min. The gas content at the top corner was never over the limit and the gas prevention and control target of the coal mining face was re ached.