Evolution Laws Of Filing Body Creep And Overlying Strata Permeability By Using Continuous Excavation And Continuous Backfilling

Continuous excavation and continuous backfilling(CECB)has the advantage of independent operation between mining and backfilling.The backfilling materials are always backfilled into the restricted space of the protected mining roadways,which can effectively control the movement of strata.This mining method can be used in water conservation mining.However,the problems need to be improved that the unclear long-term deformation law of filling body,the unknown long-term bearing capacity of filling body and the incomplete water resisting mechanism of overlying strata.Based on the creep characteristics of filling body,taking the structural stability of filling body as the premise,and aiming at the permeability control of overlying strata,the research methods of theoretical analysis,numerical simulation,laboratory test and field investigation are applied comprehensively.The research on evolution laws of filling body creep and overlying strata permeability by using CECB has been carried out.The main research results in the dissertation are as follows:(1)The mining characteristics of CECB and the composite cushion structural characteristics of filling body are analyzed.The method to determine the numerical calculation parameters during the filling body strain softening process,and the FLAC^3Dnumerical calculation model of the stress field in the filling body is established.The stress path characteristics of step-by-step cyclic loading and unloading are described,and the graded loading creep path characteristics of filling body are expounded.(2)The mechanical characteristics of filling body under the step-by-step cyclic loading and unloading stress path,and the cumulative damage characteristics of filling body in the process of stress deformation are expounded,which is defined as the initial damage before creep.On this foundation,the graded loading creep test of filling body considering initial damage is designed,and the creep mechanical characteristics of filling body is studied,such as axial strain,volume deformation,volume strain rate and failure stress.(3)The time dependence of filling body creep failure is analyzed.The plastic damage element which can be used to describe the accelerated creep characteristics of filling body is improved,and the HKBN nonlinear fractional order creep constitutive model of filling body is constructed.The determination methods of the stress thresholds,the instantaneous deformation parameters and the creep deformation parameters are proposed,and the creep deformation law of filling body is expounded.(4)The strain energy conversion characteristics of progressive destroy and abrupt catastrophe in the filling body are analyzed,and the cusp catastrophe mathematical model is constructed to describe the filling body destroy and catastrophe.The critical deformation criterion of abrupt catastrophe of filling body is obtained.Combined with the creep model,the positive constraint and reverse feedback effect of creep time on mining phase number,elastic modulus and other parameters are elaborated.The reasonable excavating and backfilling time of mining roadways is established.(5)The deformation characteristics of overlying strata considering filling body creep are analyzed.The coupling calculation model of the deflection deformation and permeability evolution of overlying strata is established,and the zonal characteristics of the permeability enhancement by unloading and creep are studied.The permeability constraint conditions of effective water resisting of strata are given,and the permeability control method of strata based on the given deformation of filling body is proposed.Combined with the engineering case,the control effects of mining factors,which includ the layout of working face,mining and backfilling type of working face,and excavating sequence of mining roadways,on the overlying strata permeability are expounded.There are 103 figures,23 tables and 202 references in the dissertation.