Research And Application On Overlying Strata Movement And Surface Subsidence Mechanism Of Paste Filling Mining With Aeolian Sand

Long wall paste filling mining is an important mining technology,which can effective improve the mining environment,reduce the damage to water and land resources,and effectively protect ground buildings for the safe use.According to the characteristics of aeolian sand widely distributed on the ground and rich in coal resources in Northwest China,this paper studies the mechanical properties of aeolian sand paste filling materials,the filling pace of long wall paste filling mining,the failure characteristics of overburden with different filling rates,and the control factors of roof displacement,etc.in particular,the filling pace of paste is discussed in depth,with the emphasis on the basic research on the key issues of long wall filling mining strata movement and surface subsidence.In this paper,theoretical analysis,laboratory tests,physical simulation and numerical analysis,as well as engineering practical application and analysis in the field are used to carry out relevant research,and based on the specific problems of long wall filling mining in aeolian sand paste,the following contents are mainly studied:(1)Based on elastic foundation beam theory,the long-wall filling mining roof elastic foundation beam mechanical model was built,the displacement equation and supporting force equation in different regions of roof were deduced.At the same time,the roof force model was equivalent transformation,on this basis,the mechanical strength of filling body gradually enhance with the time prolonged.and combined with roof displacement equation,we had derived the mathematical formula on maximum span of roof,and its mathematical relationship with the roof control zenith distance and the filling pace,then the largest filling pace was get.(2)According to the condition that the primary paste coagulation can stabilize,as well as the stress characteristics of the plastic zone and the elastic zone under the action of overburden pressure and self-weight,Wilson's constraint theory and stress SMP criterion were introduced,and the minimum filling pace was deduced and determined;Through the analysis of the long wall filling mining case of Yuyang coal mine,the theoretical value of the filling pace is 2.83~9.5m under this condition.Thus the reasonable filling pace of roof was determined.(3)Under the condition of long wall filling mining,the failure range,displacement rule and stress evolution characteristics of overburden with different filling rate are studied.By using the method of numerical simulation and similarsimulation,it is concluded that the failure degree and fracture development range of overburden are closely related to the filling rate.When the filling rate is high,the fracture development is distributed in the lower rock stratum,and the displacement of rock stratum occurs in the direct roof.The overburden is relatively complete and presents overall bending deformation;The different stress concentration of coal pillar in the front and behind the working face will appear in filling mining,the stress concentration coefficient and the influence rang are small when the filling rate is high;the stress concentration coefficient and the influence range are large when the filling rate is low.At the same time,through comparative study and analysis of caving mining and full filling mining,the relationship between overburden failure and advancing distance of working face as well as the law of surface movement and deformation are obtained: when caving mining is used,before reaching the maximum damaging height,the scope of overburden failure is linearly related to advancing distance of working face,the front coal wall is severely damaged by compression and shear,and the roof of working face presents a tensile stress failure area,which will be finally collapses,forming the collapse zone;when the complete filling mining is used,the overburden tension shear failure only exists in the direct roof and coal floor strata,and does not affect the main roof overburden.The surface and overburden showing the overall slow subsidence and movement characteristics with the filling body carrying capacity gradually strengthen.The results show that there is a non-linear relationship between the filling rate and the surface movement deformation value: it is a power function between the surface subsidence coefficient and the filling rate,and the horizontal deformation,the tilt maximum and the filling rate is a logarithmic function.(4)The main influence factors of surface subsidence in long-wall filling mining were analyzed.The roof displacement in filling mining was mainly composed of three parts: subsidence of overlying strata before filling,compression subsidence of backfill and lacking distance of roof-contact.The Filling pace and the elasticity modulus of filling body,the filling body compression ratio and compression and strata load,strength and mining depth,mining thickness,dip angle of coal seam etc of geological and mining conditions are main controlling factors of the of strata displacement and surface subsidence deformation.This paper studies the relationship between the surface movement deformation and the underground roof displacement.Through the cooperative consideration of the surface and roof of the mine movement deformation,the method of adjusting the filling pace is adopted to control the roof displacement,soas to achieve the purpose and effect of protecting the surface buildings.(5)At last,according to the geological and mining conditions of Yuyang Coal Mine and the research results,the structural characteristics and deformation limit conditions of ground buildings are analyzed.The mathematical relationship between the displacement of roof,filling pace and ground displacement is established.Yuyang Coal Mine 2307 face's filling mining technical parameters and surface movement observation station were designed;The surface movement data and subsidence law of backfill mining were observed and summarized.Therefore,theoretical research with engineering practice indicates that aeolian sand long wall filling mining can effectively reduce the mining influence and protect the safe use of ground buildings.