Prediction Of Surface Subsidence Considering Evolution Characteristics Of Mining-induced Overburden Structure

At present,our country’s energy development is shifting towards green ecology,green environment an,d’green energy.Coal,as the main energy source in my country,has attracted more and more attention to a series of environmental problems caused by its mining.Among them,the problem of surface subsidence caused by coal mining is not only one of the significant factors that threaten the safety of underground production,but also one of the important challenges of surface land reclamation and environmental governance in mining areas.In mining subsidence,the mining subsidence prediction methods,are important measures to solve the problem of surface subsidence environment,and has made great progress in rec?nt years.However,these methods are all based on mathematical statistics,and don’t consider the limitations of physical and mechanical properties and otl1 er influencing factors in the overlying rock mass.In this context,this paper establishes the corresponding mechanical subsidence prediction model based on the breaking motion?tate of overburden rock during coal mining by using tile mechanical theory analysis method,combined witll the key strata theory and the law of spatio-temporal development during separation.The main research results of this paper are as follows:Firstly,exploring the key strata theory,this paper analyzes tl1 e effect of the key strata on surface subsidence and reveals the dynamic development law of the separation layer following the coal mining process.Furthermore,we also study the application and deficiencies of the key strata theory and the dynamic development law of delamination in mining subsidence.The results illustrate that the key strata controls the movement and deformation of the ground surface,and the dynamic development of the delamination layer plays a role in transmitting the free space of the goaf.By now,they are mainly used in the field of mining subsidence prediction and grouting reduction,but there are still major deficiencies in the research of inclined coal seams.Secondly,We divided the mining stage and analyzed the mechanical deformation based on the breaking evolution characteristics of the overlying rock in the horizontal coal seam,and considered whether the collapsed broken rock block is full of the goaf and the coexistence of the simplified beam.The prediction model of surface subsidence was established on the basis of the key strata theory,the dynamic development form of delamination,and the mechanical theory.In addition,according to the impact factors contained in the subsidence prediction model,the orthogonal test method was used to conduct primary and secondary sensitivity analysis of the impact factors,and the order of sensitivities from high to low was as follows: controlling the thickness of the surface key strata,controlling the location of the surface key strata the location,the average breaking angle of the key strata overlying the coal seam,controlling the overburden load of the key surface layer,and controlling the elastic modulus of the key surface layer.Based on analyzing the influence of coal seam inclination on overburden breaking characteristics and surface deformation morphology,exploring the fracture mechanism of overburden strata of inclined coal seam,and finding the effect of inclination on the influence range of key strata control and the dynamic development law of separation,we establish a surface point sinking predicted model utilizing geometric analysis,the span distance of the overburden layer above the separation layer during mining,and the mechanical deformation mechanism.Finally,we developed the numerical models of horizontal and inclined coal seam based on the FLAC3 D numerical simulation method by utilizing the measured data of the 85301 working face of Sandaogou Coal Mine.On the one hand,the rationality,accuracy and error of the theoretical prediction model under the condition of horizontal coal seam are measured by using measured and simulated data.The results show that the theoretical prediction model has a higher accuracy within a certain range of the surface,i.e.,the closer to the central position,the higher the accuracy.On the other hand,we verified the sinking results under inclined coal seam conditions between the simulation results and theoretical prediction model results.The results between the two have good consistency,and the mean relative error is 15.7%,which is reliable.