Analysis Of Overburden Structure Feature In Steeply Dipping Seam Mining

The steeply dipping seam is defined by the coal seam which pitch is between 35°~55°. As the exhaustion of kind resources in the eastern and mining focus diverts to the western, the steeply dipping seam mining has turned to be a problem that need to be solved in process of the western regional economies development and the eastern highly efficient production and sustainble development. For the multi-factor influence of coal seam pitch, geological structure and so on, overburden stucture is a complex, dynamic, nonlinear space problem in steeply dipping seam mining. Analysis of overburden structure feature in steeply dipping seam mining has great significance to the stablishment of steeply dipping seam mining theory, and has some important references on the mining support structural parameter designing, abutment controlling and safety mining and so on.The overburden migration rule, mechanics feature and structure are studied systemical and comprehensively by the integrated methods of physical simulation, numerical simulation and theory analysis in the extensive overburden of steeply dipping seam stope. The results are shown as follow:1. Overburden caving form has the asymmetrical arch characteristic along working face tendency in the steeply dipping seam mining, and influence degree of various factors to fractured zone height is in turn: the coal seam dip angle>roof rock strength>mining height, and regression formula to the roof fractured zone height in steeply dipping seam mining is obtained: H = 168.3 ? 2.45 X 1 ? 9.53 X 2 ? 0.65X3. Compared with simulation experiment data, the rationality of regression formula is verified.2. In the steeply dipping seam mining, nonsymmetry in space and asynchronism in time of overburden migration and overburden stress heterogeneous distribution rule are revealed. The roof stress release area is mainly in the upper region of working face, the floor stress reduces gradually from upper to down, abutment pressure of the upper is smaller and the distance of it's peak value from working place is farther than those of the down.3. Surrounding rock macro stress arch-shell in the steeply dipping seam mining is proposed, which has the geometry shape asymmetry and the stress distribution heterogeneity. The analyzing model is construeted and the configuration equation is educed. Based on studying the effecting factor of surrounding rock MSAS and mining induced fracture developmental shape parameter systemically, compressive instability mode, tensile instability mode, shear instability mode and multiple instability mode of the MSAS are obtained, and instability criterion of the four kind of instability mode are given.4. Based on the condition of No.25112 working face of steeply dipping seam mining in prime coking coal mine of Xinjiang tar coal group co. ltd, the MSAS configuration equation of this condition is given by applying the analyzing mode, the tensile instability is fist happened in arch-shell roof and shoulder along with the working face advancement, and the feasibility of analyzing mode is proved.