| Most mining areas are facing the depletion of recoverable resources,the inability to mine pressed coal under buildings,railways,and water bodies,and the serious environmental pollution by coal-associated solid wastes with the improvement of coal mining equipment and technology and the long-term high-intensity mining of coal resources.Coal mining under buildings,railways,and water bodies is an urgent problem to be solved.Paste backfilling mining is one of the green mining methods that effectively solve the problem of "coal under buildings,railways,and water bodies " coal pressure and recover coal resources.the work combined theoretical research,laboratory experiments,physical simulation,numerical simulation,and field measurements to Study the Efficient Stratified Paste backfilling Mining Technology and the Movement Law of Overlying Strata.The following innovative research results have been achieved.(1)Samples were prepared on-site for laboratory experiments,and the destruction process and test results of backfilling samples in the experiment were recorded according to the composition of paste-backfilling materials in the Lu’an mining area.Multiple inversion tests were performed through particle-flow simulation software to obtain results consistent with the experiment.Then the microscopic parameters of the backfilling body were calibrated and assigned to the particle flow model.The damage and bearing mechanism of the backfilling body were studied during three-way loading to establish a synergistic bearing capacity model of paste backfilling and mining is established.Besides,the work proved the force deformation characteristics of coal and rocks and backfilling bodies in different areas of the backfilling-mining working face.(2)Four technical solutions were proposed for long-wall stratified backfilling and mining of thick coal.Combined with the technical parameters of the latest selected paste-backfilling and mining-related equipment,the backfilling and mining process has been optimized to achieve efficient paste-backfilling mining.The influence range of the advanced stress of backfilling mining and the bearing effect of backfilling bodies in different areas were studied to determine the key technical parameters of stratified backfilling and co-mining and co-backfilling of thick coal seams.(3)A mechanical model of the clamped beam was established to study the critical conditions of roof fractures of the lower-layer and upper-layer backfilling surfaces.The masonry beam theory was used to explore the connection stability of paste’s false roof and immediate roof during stratified mining.The instability conditions of paste’s false roof were determined to propose the roof-stability control strategies of different stratified backfilling surfaces.(4)The damage model of overlying-strata mining by backfilling mining and caving mining was established to study the correspondence between the overlyingstrata fracture development of backfilling mining and collapse mining.Besides,a method was proposed for calculating the height of the fracture development of backfilling mining.The protection of the surface brick-mixed structure of pastebackfilling mining was evaluated based on the on-site measurement results.This thesis includes 100 figures,16 tables and 208 references. |
