Research On Strata Pressure Behavior Law And Control Technology Of Multiple Coal Seams Overlap Mining In Datong Mining Area

The Jurassic and Carboniferous coal seams are overlap mined in Datong mining area, and the upper Jurassic coal seams have a long mining history and more mining forms. Strong strata pressure is appeared and the roof is maintained very difficulty when the Jurassic lower coal seam and Carboniferous special thick coal seam mining. Therefore, based on the occurrence characteristics and mining conditions of "dual system" coal seams in Datong mining area, the law of strata pressure behavior and control technology of working face are researched respectively when Jurassic close coal seams mining and Carboniferous special thick seam mining. The analysis method is field investigation, theoretical research, similar simulation experiment and field measurement. The principal results are as follows:The iterative associated model of strata stress and deformation is established for coal seams, with the analysis principle and method are also given. The upper support coal pillar is considered as typical stress unit to affect the lower coal seam mining. The calculation method of concentrated stress is proposed when overlying strata is fully collapse and not fully collapse. The law of superimposed stress transferred from coal pillar in multiple layers is analyzed by the theory. Strata fracture is divided into static fracture and dynamic fracture, and dynamic fracture analysis model of strata is established for coal seams mining. Strata fracture is analyzed by the theory under the conditions of roof structure stability and instability. Leakage space formed by strata collapse is considered as unified transfixion zone, and the developed level of transfixion zone are theoretical analyzed respectively under the conditions of single stope and multi-stope.Based on numerous tests of compressive and extension strength for specimens with different material ratio, the distribution law of overlying strata displacement, fracture and stress was researched when the Jurassic and Carboniferous coal seams collaborative mining. The analysis method is similar simulation experiment. Stress and collapse form of overlying strata is considered as coupled time-varying system when the coal seams mining. System status has experienced the cycling process of "balance-instability-balance", with obvious concentrated stress, strenuous strata movement and large range fissure. And complex connectivity status of multi-goaf is formed.The 8910 fully mechanized face of Yongdingzhuang coal mine is used as a typical to research on the law of strata pressure behavior and control technology when Jurassic close coal seams mining. The analysis method is theoretical research and field measurement. The direct influence of superimposed stress transferred from overlying coal pillar to the lower working face is analyzed. Dynamic deformation rules of the basic roof strata, strata behaviors characteristic and the mechanism of intensive strata behaviors are revealed for the fully mechanized face under the action of concentrated load. Reasonable working resistance of hydraulic support is determined respectively when the fully mechanized face under the goaf, entity coal and coal pillar. And the the corresponding control measures of mine pressure is put forward to ensure the safety mining of working face.The 8105 fully mechanized caving face of Tongxin coal mine is used as a typical to research on the law of strata pressure behavior and control technology when Carboniferous special thick seam mining. The analysis method is theoretical research and field measurement. The superimposed stress transferred from overlying Jurassic multi-coal pillar is analyzed, and the superimposed stress would play a energy accumulation role to the Carboniferous large strata area. Dynamic deformation rules of the key strata is revealed under the action of concentrated load. Inducement and mechanism of frequently intensive strata behaviors are analyzed when Carboniferous special thick seam mining. Reasonable working resistance of hydraulic support in fully mechanized caving face is determined by "cantilever beam-articulated beam" structure and strata torque balance analytical method. Combined with roof control technology, special thick coal seam is mined safely and smoothly.