| China is a big country of coal resource consumption,and it is also a big country of coal mining.Therefore,the area of surface subsidence caused by coal mining is increasing year by year.The damage of regional hydrogeological environment and the formation of surface subsidence caused by coal mining have seriously damaged the ecological environment in some areas.Moreover,there has been a series of environmental degradation phenomena such as the reduction of agricultural production and the collapse of the road and building.Therefore,it is necessary to determine the surface displacement range caused by the mine goafs.Through this analysis,it can provide the basis for the restoration management.The surface subsidence caused by the Dongfu Second Coal Mine was taken as the study object in this paper.This coal mine belongs to the Shulan Mining Group.According to the detailed field investigation of the study area,the distribution range of ground deformations has been determined.Then,the specific genetic mechanism for surface subsidence is also given.The influence of geological conditions and goaf conditions on the surface subsidence has been analyzed in the goaf.Moreover,the mechanism of different surface deformation phenomena was determined.According to the location and scale of the goafs in the study area,the calculation parameters required by the probability integral method can be determined by combining existing achievements and the actual geological conditions of the study area.Then,the maximum possible subsidence value and the possible affected area of each goaf can be obtained.According to the above calculation results,the superposition method is used to plot the maximum possible subsidence basins for each coal seam and the whole coal seam.Based on the characteristics of the subsidence basins and the existing surface subsidence in the study area,the area tends to be stable or instability can be determined.The FLAC3 D software was used to determine the maximum possible subsidence basin of the study area.In this study,the Hoek-Brown model is used as the constitutive model for rock masses,and the Mohr-Coulomb model is used as the constitutive model for soils.The strength parameters of the numerical simulation model are determined by the indoor test,and the Hoek-Brown strength empirical parameters can be determined by the actual geological conditions of the study area.According to the mining area plots and the geologic section maps in the study area,the fluctuation of each strata can be determined.Then,the surface topographic features and the fluctuation of each strata can be considered in the numerical simulation model.The differences between the probability integral method and the numerical method are also presented in this study.The differences are mainly caused by the fact that the probability integral method does not consider the interaction between the goafs and the geochemical parameters are homogeneous in the model.In comparison,the results of the numerical method have more practical significance.Finally,the FLAC3 D software was used to simulate the influence of the change of the topography and inclination of coal seam inclination on the subsidence basin.In this study,a total of three sets of comparative experiments and ten numerical models were established.The following content are analyzed:(1)When the surface topography is the same,the changes of the subsidence basin with the relative position of the surface slope are studied;(2)When position of the goaf is the same,changes of the subsidence basin with the different gradient of the surface slope are studied;(3)When the surface topography is the same,the changes of subsidence basin with the dip angle of coal seam are studied.Moreover,the influence degree of each factor for subsidence basins is determined and the action mechanism of each factor is discussed. |
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