Spatial And Temporal Evolution Model Of Overburden Separation In Coal Mining And Its Application

The hydrogeological conditions of coal mines in China are complex.Water inrush is one of the major hidden dangers in coal mining.In recent years,the water in roof bedding separation inrush occur frequently,causing great harm.It is of great significance to study the temporal and spatial evolution model of overburden separation in coal seam mining for the prevention and control of water inrush from separation layer.Taking Yingpanhao coal mine in Ordos basin as the research background,based on the analysis of the geological data of the research area,this paper studies the formation mechanism and prediction method of the potential bed separation,mechanical model of spatial and temporal evolution of bed separation,and the prediction method of the dynamic development position of the separation by theoretical analysis,mechanical calculation,numerical simulation and field in-situ test,etc.The main results are as follows.(1)After mining,the movement of roof overburden is developed in the form of step-by-step in the unit of rock formation.Each rock formation is composed of the hard rock with high strength at the bottom and the soft rock at the top.The correct division of composite structure of overburden is the key to distinguish the location of potential bed separation.On this basis,the paper further analyzes the essence and defects of the conventional approaches of identifying the locations of potential bed separation,and puts forward a prediction method of the locations of potential bed separation based on the modified critical layer theory.(2)The location of potential bed separation in 2202 working face of Yingpanhao coalfield are predicted by theoretical method and empirical formula respectively: potential bed separation are developed in the internal and interface of Zhiluo group,Anding group and Zhidan group;potential bed separation are distributed sporadically and discontinuously in Zhiluo group and Anding group,and most potential bed separation are distributed in the interface between Zhidan group and anding group and the internal of Zhidan group.(3)Due to the coupling effect of mining thickness and rock mass expansion,the development mode of the separation layer at different levels is different.According to the different stress state of the rock group under the separation layer,the separation layer is divided into the supporting type and the unsupported type with the water conducting fracture zone as the boundary.The separation mode within the development height of the water conducting fracture zone is the unsupported type,and the other is the supporting type.(4)According to the type of separation layer,the deformation mechanics model of rock group under bed separation is established and solved respectively and a prediction method of separation layer dynamic development position is proposed,which mainly includes: delineating the development range of separation layer,predicting the potential position of separation layer before mining,distinguishing the bed separation mode,distinguishing the fracture of rock group and predicting the dynamic development position of separation layer.(5)Taking 2202 working face of Yingpanhao coal mine as an example,the spatio-temporal distribution characteristics of bed separation are analyzed by 3DEC software numerical simulation and settlement instrument actual measurement,the rationality of the prediction method of potential location of separation layer,time-space evolution mechanical model of mining roof separation layer and prediction method of dynamic development location of separation layer proposed in this paper is verified.