Study On Main Geological Factors Of Influencing Bear Capacity Of Geological Environment In Coal-mining Area

Aiming for a decrease in destruction of geological environment induced by coal mining, Theoretical system of "tectonic control of hazard"have perfected in this thesis, based on the research of the control mechanism of comprehensive hardness of the cover rocks ,the position of key stratum, groudwater , fractures and tectonic stress over ground environment hazards by means of theoretical analysis and mechanics,digital testing and similar material simulation in allusion to concrete condition of geological and underground mining in typical coal mining areas of Shaanxi. Under the minnig of the same intensity, coal-mining-induced subsidence is relatively weaker because hard cover rocks have stronger ability to resist deformation; The larger proportion in cover of loose ground is, the smaller synthetical hardness of cover rocks is, at the same time gravity of above coal seam is heavier, coal-mining-induced subsidence is easy to occur; The key stratum plays an important role on improving the ability to resist deformation of cover rocks. The more thicker ,harder key stratum is ,the more harder synthetical hardness is, the more higher intensity and stronger ability to resist deformation of cover is . The key stratum located upper position in the cover might clearly restrict the ground subsidence under certain mining intensity. Underground water can evidently facilitate coal-mining-induced subsidence because that it may intenerate the cover of worked coal seam, increase the cover's weight and change the stress in the cover with the results of reducing rock's mechanical strength and remodeling stress state in the cover. Coal-mining-induced subsidence may change underground water system.Water-resisting layer located under position in the phreatic water is not destroyed, but bending zone is formed by underground mining ,coal-mining-induced subsidence can't cause shallow groundwater resource loss, which can change the ecological environment, making groundwater turn into the surface water. Water-resisting layer located under position in the phreatic water is destroyed, and water flowing fractured zone communicates with aquifer,water of aquifer will along cranny flow into goaf, which not only causes the water resource loss but also leads to water hazard of mine. Fractures ,which have destroyed continuity of terrane and reduced the intensity of rocks and brought out the stress focusing on the interfaces , are the geological discontinuity surface within strata. Therefore, coal-mining-induced subsidence is easy to develop. Coal mining-induced subsidence occurs and develops more easily in the cover of worked coal seam in which exist large numbers of small faults and joints.There are great faults in cover , called non- continuous medium, not only the surface forms fracture or collapse, but also characteristics of collapse basin present asymmetric. Compression and tension are the most essential tectonic stress states in coal areas. They can't be neglect in controling function of coal-mining-induced subsidence. Coal mining-induced subsidence occurs and develops more easily in regional tensile stress. On the other way, the intensity of rocks will be strengthened in the regional compression stress. Therefore coal-mining-induced subsidence is reduced or lag in a compressive stress field.