Protective Mechanism And Control Of Overlying Water-Seepage-Resistance Zone Under Continuous Extraction And Continuous Backfill

In view of the problems of insufficient filling time and space,as well as the mutual constraints between mining and filling in longwall backfill mining,a new continuous extraction and continuous backfill（CECB）mining method based on continuous mining and partial backfill was proposed.The indoor experiments,numerical andphysical simulation,mechanical analysis,and on-site measurement have been comprehensively employed to conduct in-depth study around the protective mechanism and control of WSRZ.The main research results are as follows:（1）The CO₂ mineralized filling body（CMFB）for CECB has been developed,and the mechanical properties,microstructure,phase characterization,rheological properties and carbon fixation rate have been investigated to clarify its mine applicability.The post-peak attenuation laws of strain-softening parameters for CMFB in protective block are illustrated.A parameter assignment method for the strain-hardening elastic constitutive model of the caved gangue in mining block was proposed,based on real-time replacement of elastic bulk modulus with vertical strain increment.The numerical inversion of overburden damage was implemented based on the secondary development of FLAC^3D,and the partition threshold of"three seepage zones"based on damage and permeability deterioration was determined.The definition and classification criteria of WSRS are given,and the mutual feedback mechanism between WSRS and WSRZ was revealed.The concept of water-seepage-blocking was proposed,and the criteria are given.（2）The mechanical model of the Proctor pressure arch was established and the mechanism of stress transfer and arch extending is revealed.The constraints of the ultimate span of extending arch and CMFB strength were explored.A chain instability criterion for CMFB based on stress transfer and redistribution are also proposed.The elastic foundation beam mechanical models for the collaborative deformation of the"CMFB-coal-WSRS"and the"gangue-CMFB-WSRS"were established,respectively.The characteristics of gradual loading and asynchronous deformation of the CMFB was revealed,and the coupling elastic foundation coefficient of the"CMFB-coal"was determined.A non-linear elastic and linear elastic improvement method for the Salamon’s model of the gangue in mining block was proposed,and the elastic foundation coefficients of the gangue and CMFB were thus ascertained.The deflection,stress,and bending moment of each overlying layer was obtained,and a mechanical method to predict the height of WSRZ based on maximum tensile stress was proposed.（3）The spatiotemporal evolution laws of stress,displacement,and fractures in overlying strata in CECB were analyzed,and the overburden damage features of the mining block were determined.The UDEC-COMSOL multifield coupling simulation was conducted under mining height,the width of mining and protection block,mining depth and hard rock lithology ratio were conducted and the development law and distribution characteristics of fracture seepage were obtained.A main factor sensitivity analysis of the height of WSRZ was carried out,and a prediction model of the vertical level for WSRZ in CECB was established.（4）The features of mining-induced stress paths in three seepage zones were analyzed,and were equivalently converted into laboratory stress paths.Triaxial seepage experiments under stress paths were then conducted,and the characteristics of rock damage due to compression shear and tensile failure and the permeability evolution law of S-shaped in complex stress conditions were analyzed.The coupling relationship between the deviatoric stress and permeability in stress paths was demonstrated,and a permeability evolution model based on the segmented characterization was constructed.The evolution laws and partition characteristics of overburden permeability and seepage characteristics were illustrated.The permeability zoning threshold based on permeability deterioration rate and seepage velocity has been determined,and the control effect of mining and filling parameters on water seepage was clarified.（5）A tertiary-level comprehensive evaluation model with twelve indexes for the WSR grade of WSRZ was constructed.Aiming at the mining-filling span with large weight in the model,the WSRS deformation and the water level drop of aquifer corresponding to 5 mining-filling spans were studied and the reliability of the model were verified.The spatial visualization was conducted on tertiary factors in the Yu-Shen mining area.The zoning maps of the WSR grade of 400 boreholes under different mining and filling parameters were drawn.A control system for maintaining the stability of WSRZ based on the qualitative-quantitative regulation was constructed,and a method for optimizing the width of mining and protective block was proposed in complex hydrogeological conditions.There are 115 pieces of figures,19 pieces of tables and 214 pieces of references in the dissertation.