Study On Characteristics Of Overburden And Thick Loose Layer Surface Movement Deformation By "Mining And Filling" Coupled Mining

The surface of China's east area is mostly villages and farmlands,and the fourth layer of loose layer is thick.Longwall mining could lead to serious surface subsidence,rising water table,crop extinction and other problems,it was easy to induce serious contradictions between workers and farmers.At present,strip mining and filling mining are used to control surface subsidence,however,there are problems such as low recovery rate and high excavation rate in strip mining,The full-filling mining has the disadvantages of low mining efficiency and high filling cost.And under the thick loose layer,coal mining strata and surface movement deformation showed significant change.In order to control the effect of mining on surface subsidence,in this paper,a method of coupled mining techniques for the fall strip and the filling strip are proposed,through the combination of theoretical analysis,similar material simulation and numerical simulation,the law of "mining-filling" and coordinating the exploitation of overburden and thick and loose layer surface movement deformation was studied.,the following main conclusions were obtained:(1)Based on elastic mechanics and thin plate theory,the filling strip force model and the"mining-filling" coupled mining mechanics model were established under the key control stratum conditions,the filling body force expression under the key stratum condition was derived by the four-sided solid-branch sheet limit carrying capacity,combining the volume of load under the critical destabilization limit of the filling body,and the relationship expression between the width of the filling body and the width of the goaf area was given.Combined with the actual mining geological conditions,the "mining-and-filling" dimensions were analyzed and calculated.(2)Based on physical similarity material simulation experiment,the influence of key control stratum formations on the strata structure in the process of working surface propulsion was studied.It is shown that the reasonable "mining-filling" size can effectively control the surface without the occurrence of wave-shaped subsidence basins.The maximum subsidence at the top was 610mm.In terms of stress monitoring,the maximum stress concentration of the roof in the whole mining process is 11.9 MPa,the stress concentration coefficient is 1.5.(3)The deformation law of overburden and surface under the thick loose layer condition was studied by the numerical simulation experiment of FLAC3D,the maximum surface subsidence 601mm,the surface form is a relatively flat sunken basin,tilt deformation 1.52mm/m,horizontal movement of 324mm,horizontal deformation-1.21 mm/m,the basin boundary is horizontally stretched and the middle part is in horizontal compression.The stress distribution on the filling body in support stress was "saddle-shaped",core stress of the filling body is 10 MPa,with a stress peak of 20.42 MPa on both sides,which is 2.3 times the stress of the original rock.The laws of overburden and surface movement deformation under the conditions of different filling surface width,thickness,filling rate,loose layer thickness were studied,and the functional relationship between variables and surface movement deformation and sinking coefficients was obtained based on regression analysis.Through orthogonal experiment,it was concluded that the influence of various factors on the deformation of surface movement has been sorted as:fill rate,fill face width,coal seam thickness,loose layer thickness,the degree of influence of each factor on the stress of the top plate has been sorted as:loose layer thickness,filling surface width,filling rate,coal seam mining thickness.(4)By comparing with strip mining surface subsidence,the relative surface subsidence and subsidence coefficient of "mining-filling coupled mining" were increased by 50%.,tilt deformation increased by 45%,horizontal deformation increased by 60%,surface deformation can be controlled within the extent I damage when the fill surface width is greater than 60m,and the control effect on the surface when the width of the "mining-filling coupled mining" filling surface was 100m equivalent to strip mining leave 52m coal column.At the same time,the economic benefits of mining-filling coupled mining are analyzed,which shows that the high recovery rate of mining-filling coupled mining for coal resources and the full-fill cost control have obvious advantages.