Mechanism And Method Of Key Aquiclude Strata Reconstruction By Backfill Mining Technology

The hydrogeological conditions of coal mines are complex in China,and the reserves of coal resources threatened by by potential water inrush from underground aquifers are huge.In the process of coal seam mining,the study of damage degree and permeability evolution response law of key aquifer strata(KAS)is of great significance for realizing safe mining of coal resources and water resources protection under aquifer.As a typical representative of groundwater environmental protection technology in green mines,solid backfill mining technology can effectively control the development of water-conducting fractures and the formation of seepage inrush channels in KAS,providing good conditions for the structure and seepage stability of KAS.Based on the theory of KAS in water-preserved coal mining,this thesis put forward the research route of KAS reconstruction in backfill coal mining,and then physical mechanics and seepage characterization test of KAS in typical mining area,the interaction between KAS and backfill body,mechanism of structure damage and nonlinear seepage instability of KAS reconstruction in backfill coal mining,spatio-temporal response characteristics of fracture field and seepage field are conducted by applying experiments,theoretical analysis,numerical simulation,physical simulation and industrial test.The dissertation also gives the engineering design method of the reconstruction of KAS in backfill mining under aquifer,which is then applied in the field application.The main innovative achievements are as follows:(1)Based on the theory of KAS in water-preserved coal mining,this thesis puts forward the concept of KAS reconstruction in backfill mining.Basic structural types and forms of KAS reconstruction in backfill mining are given,and by studying the reconstruction mechanism of the single KAS and the complex effect of KAS,the basic connotation of KAS reconstruction is revealed.(2)The mechanical model of composite beams on nonlinear elastic foundation and the nonlinear seepage dynamical model of KAS in backfill mining are constructed,and the mechanical structure damage and nonlinear seepage system instability criteria are given respectively.The quantitative relationship between structural damage and non-linear seepage stability of KAS and backfill materials' compaction ratio(BMCRs)are analyzed.The mechanism of instability in KAS reconstruction during backfill mining is revealed.(3)Through numerical simulation and physical simulation analysis,the evolution law of water-preserved capability of KAS during the reconstruction process of fractures initiation,expansion and development,fractures closed or fractures connected in backfill mining with different structure characteristics,horizon characteristics,and BMCRs are studied,and the fractures spatio-temporal evolution and seepage response characteristics of KAS reconstruction in backfill mining under mining-induced stress are obtained.(4)The engineering design method of KAS reconstruction in backfill mining is proposed under aquifer,based on the spatial distribution features,rock seepage characterization test,and nonlinear seepage stability mechanics model of KAS,the distribution characteristics and regional division of the BMCRs index of the backfill mining face in the test area are designed.Verification results of actual engineering project are also carried out,and good application effect is achieved.There are 122 pictures,24 tables and 207 references in this thesis.