Relationship Between Gas Emission And Periodic Weighting Of Coal Face With Hard Roof

Methane problem is getting more seriously with the depth of mine pits is increasing in our country. There are many low methane mines are gradually becoming high ones even coal and gas burst ones. On the basis of 21010 synthetic mechanical mining face in Pingdingshan 2nd Coal mine.It analyzed the relationship between period weighing in the process of the synthetic mechanical mining and out-flow of methane.through field measurements and numerical modeling. Meanwhile,based on the theoretical analysis,it can derive the mechanism which the period weighting effected the increase of out-flow of methane,and directly provide theoretical instruction for the methane control,with the important practical significance.Firstly,Basic parameters of panel pressure are concluded by numerical modeling and Field measurements which conduct in the 21010 synthetic mechanical mining face.The analysis of real time curve of methane density in the tailgate stated during pressure observation and the change of methane density in the tailgate sorted back and forth the first weighting and period weighting resulted that the increase of out-flow of methane with posteriority, normally ,this occurs in 2~3 producing time after the caving of the main roof. Stope TEM can be used to measure the source of out-flow of methane, while methane which emit from coal wall and gob are used as object of study for analyzing the increase of abundance of methane.The coaction of the changes of cracks region in front of coal wall and H.D methane which accumulated by the main roof caving of gob areas resulted the increase of abundance of methane after period weighting. During period weighting, extension of the cracks in front of coal wall makes its permeability changed, Obviously, the mechanism can be analyzed from lateral pressure coefficient and impact stress wave respectively. The empirical formula can be used to analyze and calculate the bulking factor and permeability, on the direction of vertical, the closer the upper, the smaller their values. and on the direction of face advance, the closer the face, the larger the permeability. When the main roof caves, it is one of the main factors that H.D methane can only flood in face.