Research On The Deformation Mechanism And The Location Optimization Of High-Level Entry For Gas Extraction

The high-level entry ,with the strike parallel to the advancing direction of the working face ,is a typical roof roadway. It is 50~60m above the working face,and has a widespread use in YangQuan mining areas. It is an ideal way to drainage gas from adjacent layers. Among gas emitting to working face , gas from adjacent layers reaches 90% of total amount.At present,the design and support scheme of high-level entry is mainly depending on the field experience. Once put into use,it will be sealed and no one can get access to it. Being in the mining fissure zone,the high-level entry is destined to deform,which restricts high production and high efficiency of gassy mines. The deformation process of high-level entry is lack of systematic research,not to mention the locaiton optimation of it,which decreases its function.On basis of numerical simulation and mechanical analysis, the dissertation summarizes such conclusions:1)Floor heaving is the typical deformation characteristics of high-level entry. After 80m behind working face ,the section closure is serious; when high-level entry is 140m behind working face ,the section is approaching closure.2)The deformation process of high-level entry is: (a)the initial period. Before 40m behind working face,the floor begins to heave;(b) the violent period. During 40m~80m behind working face,the floor heaving is serious; (c)the closure period. After 80m behind working face,the high-level entry is approching closure.3) The horizonal stress of both sides and floor is sharply increasing during the coal mining,and the horizonal stress of roof is decreasing. The mechanical analysis shows,that the increasing horizonal stress leads to the floor separation,which contributes to the floor heaving.4)Among the schemes 60m,70m,85m above the working face,the optimizaiton location for high level entry is 40~60m,40~70m,60~90m away from the return airway respectively.The research results provide scientific basis for reasonable arrangement of high-level entry at gassy mines. And it is an effctive way to safeaurd high production and high efficiency of gassy mines.