Study On The Strata Control Research Of Mining Middle Abandoned Coal Seam With "Upper Caving-Lower Pillar" Composite Residual Areas

Coal as a non renewable energy,its reserves are declining,while many countries in the world to use clean energy and other renewable resources to gradually replace coal in the energy reserve status,but still as the main body of the global coal industry and other resources.In view of the limited coal reserves and industrial life in great demand,along with the development of residual coal mining technology.Some of mine abandoned small thickness or inferior coal seam mining under the influence of various factors in the process of coal mining,such problems of complex ore pressure,deformation and gas migration of roof and floor water inrush in upper and lower coal seam mining central whole layer abandoned coal mining process.Taking Xishan group Baijiazhuang Coal Mine "caving under pillar" composite residual mining area No.7 coal seam as the background,mainly through theoretical analysis,numerical simulation and simulation method combining the similarity of stress characteristics and the stability of a comprehensive analysis of surrounding rock caused by mining of No.7 coal seam,the comprehensive evaluation of the feasibility of coal mining and the special geological conditions.The main research contents and results is as follows:(1)The central composite residual mining area the whole layer of abandoned coal caving mining is carried out by simulation analysis,and the upper part of the lower coal seam No.8 No.6 coal mining brings multiplemining influence,the interlayer rock strength weakening,the central No.7abandoned coal direct roof periodic caving distance is small,fall the block is small and the rock are extruded and occlusal arranged in coal seam floor.Since the middle of No.7 coal mining influence,the lower part of the goaf stability of coal pillar under certain interference.Due to the superposition coal pillar stress concentration effect,the coal pillar is further spalling,roof rupture range extended upward trapezoid space collapse column becomes larger,forming layers lead to rock "beam,plate structure to high migration.(2)The central composite residual mining area the whole layer of abandoned coal caving mining was simulated,in the middle of the whole layer of abandoned coal caving mining,should be features of field of force between the rock strata: column mining range between the rock strata under the stress field of the mining influence is significant.The specific performance of the 8-1column and 8-4 column in mining overburden rock tensile stress zone and No.6coal seam goaf floor through tensile stress zone,8-3 column mining overburden stress extension zone;less affected and abandoned coal mining tool column coal pillar rock stress field.(3)The central composite residual are in the whole layer on the lower part of the abandoned coal mining influence keeping the stability of coal pillar is analyzed in theory,analyzes the process of coal pillar failure,pointed out that "saddle shape" is the stability of the coal pillar should be the typical form of the stress distribution of coal pillar is to maintain stability,to the existence of nuclear area,further that the design principle and calculation method of coal pillar width.The calculation formula of the actual load at the same time,based on the traditional small coal pillar,deduces the two mining coal pillar under the actual load calculation formula for multi coal upward mining of lower coal seam,the reference design for coal pillar mining pillar.(4)By the combined method of theoretical analysis and Simulation of a comprehensive study on the central composite whole layer of abandoned coalmining residual mining area the feasibility,we get the results as follows: the lower coal pillar mining,stope above the control layer,the deformation and failure of overlying rock plays a major role in controlling the lower part.Coal mining coal mining upper control layer,eventually supported by the coal body around,and the formation of three-dimensional plate structure with some boundary constraints in the mining unit above.Control stability can be analyzed by plate structure strength calculation.The upper part of the coal caving mining,the upper layer of the rock between the bearing layer maintain the rock stability,bearing layer stability can guarantee the efficient mining of central coal safety,through the depth research on the instability of bearing layer position on the mining damage state of surrounding rock and the damage.The bearing layer of stress and strain analysis,that this rock is clamped rectangular elastic plate structure.Based on the superposition principle of plate bending,can be clamped rectangular plate with maximum deflection value,and then determine the bearing layer stability characteristics.Through the analysis of simulation of similar bearing-under control "the stability of Baijiazhuang Coal mine" on that fall under the knife-column composite residue in the central mining whole layer of abandoned coal can be safe and efficient exploitation.