Research On Top Coal Cavibility And Control Of High Ductility Very Thick Seam In Top Coal Caving Mining

The paper is on the basis of big thickness, high ductility, bad cavibility of second coal seam in Lingwu mining district, and the fully mechanized top coal caving method is hard to broaden. First, through test research on second coal's mining technological condition and physical characteristic index, physical mechanical properity of high ductility coal seam is determined, ductility of top coal is defined and the critical index of ductility is given. By using FLAC program, numerical model is builded, the mechanism is obtained that high ductility top coal's elastic modulus is small and the cavibility is bad. Futhermore, the paper using "Fuzzy theory", the second coal's cavibility is analyzed and accrediates it as type Ⅳ, that is, the top coal's cavibility is bad. The main reason is joint crack is not developed and the ductility is big. The major controlling factor is top coal's crack. On the basis , top coal's properity is aggregative analysis and weakening method is compared, the reasonable method to control top coal's cavibility is the weakening technology of advance inducer shotfiring. The technological scheme is purposed that using advance blasting in process roadway to weaken top coal of workface. By industrical test at the test face in Ci Yaobao mine of Lingwu mining district, the recovery coefficient is up to 77.1﹪ and gets the expected effection. The research indicates that the definition of top coal ductility is reasonable and the evalution of top coal cavibility is proper, the determination of the cavibility's main controlling factor is correct and the technological scheme is feasible.