Study On Roadway Stability Of High Intensity Mining Condition

Fully mechanized Top Coal Caving method was widely used in china during recent decades. This method is with the advantage of high efficiency, high capacity, centralized production and etc. However, high capacity exploration caused large quantity of residual coal, large space at mined-out region. As a result, the methane content at workface of mined-out region increases rapidly and the methane content at return airway and upper corner of workface often exceed the limitation. Not only can power failure at coal workface and consequently serious economic loss be caused, but also destructive accidents such as methane combustion even explosion can be caused, which is a serious potential danger for coal mining safety. It has caused restriction for the spread of fully mechanized top coal caving method. In this case, the study for the spread, moving, flow and distribution regularity is necessary from the view of economic point and actual practice point. The main content of this paper is as follows:1,After coal exploration with fully mechanized top caving method, top roof could fall directly at mined-out region。As a result, loose areas could be formed near coal columns and supports. On the other hand, rotation and unstability could happen at the area which is far from workface and the area at the deep inside of mined-out region could be compacted again. With the progress of workface and enlarging of mined-out area, the compaction area is becoming bigger and bigger gradually. In this case, the circle area like "O" is formed and a great deal of methane is stored at these circle areas.2,Considering mined-out region as non-homogeneous porous medium, we can get the methane effusing and methane moving control equation.3,Simulation study for the methane moving regularity at 3201 working surface under "U" type ventilation and "U+L" type ventilation is carried out through software FLUENT. Methane content and distribution rules at different position under "U" ventilation and "U+L" ventilation are stated in detail. According to the comparison and analysis, it can be concluded that no matter under "U" ventilation or "U+L"ventilation, methane content will decrease with the increasing of ventilation. In addition, under the same ventilation, although the content difference between "U+L" ventilation and "U" ventilation is not so large, methane content at upper corner near to return airway can be decreased a lot and safe production can be ensured.4,Relation between Production volume and methane effusing quantity is analyzed According to the actual survey for the coal mine 3201 working surface for almost half a year. In addition, the actual result is compared with numeric simulation result and it is concluded that the simulation result can be used as reference during actual practice.