Quantitative Characterization of Overburden Rock Development Pattern in the Goaf at Different Key Stratum Locations Based on DEM

Figure 17

Permeability zoning in goaf when excavated to 190 m of scheme 1. The porosity distribution of scheme 1 is shown in Figure 17, and the permeability zone is divided into four regions. (a) Strong permeability zone，the porosity rate in this area is generally greater than 0.25, mainly due to the coal gangue accumulation holes and vertical fissures of rock collapse, and dynamic changes with the advance of the working face, which can directly affect the working face. (b) Permeability zone，the porosity of this area is between 0.1 and 0.35, and it is mainly composed of vertical fissures, and the influence range can reach 60 m in the vertical direction, and if the above contains aquifer, it may directly affect the working surface. (c) Separation zone，the porosity of this area is 0.25–0.35, mainly composed of separation lateral fissures, which may become a water storage space if the rock formation contains water, but has less impact on the working surface. (d) Compacted stability zone，the porosity of this area is generally below 0.1, mainly because the coal gangue in the goaf is compacted under the action of the load above, and the stress is gradually recovered by the stress-relaxation area, resulting in the reduction of porosity. The water conductivity of this area is weak and has little influence on the working face.