The study of water-conducting fracture zone development height is key to the scientific prevention and control of water damage in mines. Based on the geological conditions of the Wenjiapo coal mine in Binchang, China, this paper investigates the development of water-conducting fracture zone in overlying bedrock during mining under large buried depth and huge thick aquifer by combining on-site well-location microseismic monitoring and laboratory similar material simulation. To overcome the limitation of the " limited outlook " of water-conducting fracture zone investigation, the spatial development characteristics of roof fissures in coal seam mining were determined by on-site " the underground - ground" combined microseismic monitoring and follow-up monitoring, and the development of overlying rock fracture under the large depth of burial was concluded. The fractures were mainly distributed in the upper part of the protective coal pillar on both sides of the working face, but less in the upper part of the working face, and primarily distributed in the protective coal pillar on the side of the working face and the adjacent mining area. To verify the accuracy of the conclusion, the overlying bedrock movement and deformation characteristics and the development process of the hydraulic fracture zone during coal seam mining were analyzed by simulating similar materials in the laboratory, using the monitored area as a prototype. The results show that the development height of the mining fracture zone obtained from microseismic monitoring is basically consistent with the simulation results of similar materials. The research finding have significant implications for the study of fracture distribution characteristics and the evolution law of mining overburden, and provide a foundation for scientific prevention and control of water damage on the roof.

Groundwater leakage in the loess gully terrain is one of the main hazards of coal seam mining at shallow burial depth. The burial depth of the 5−2 coal seam is less than 50 m from the ground in the gully of the study site. The fissures that expand upward after mining can easily penetrate the ground to form a water-conducting channels. During rainy periods, there is a potential risk of groundwater leakage. In order to reveal the characteristics of plane development and the dynamic evolution of gully ground fissures, the typical U-shaped gully in the northern Shaanxi coal mine was studied using the field measurement methods of “On-site measurement” and UAV aerial photography. Based on the experimental platform of ground fissure leakage developed and designed by the team, an indoor test model corresponding to the actual situation was established. In addition, the mathematical models of actual flood inrush, fissure width, and flood flow in the channel were established. The actual mine water flow and the mine drainage capacity were compared and analyzed, thus proposing criteria for classifying gully mining ground fissure collapsed water hazards. These criteria can provide theoretical references for predicting fissure leakage hazard zones in the ground gully of shallow buried coal seams. According to the development height of the water-conducting fissure zone (WCFZ), the treatment methods of ground fissures in gullies under different security conditions were designed, which was applied in the field with good results. The results showed that the treatment methods in this paper could effectively prevent the leakage of groundwater in the gullies along the ground fissures.

Surface damage caused by coal mining is one of the problems perplexing ecological environment restorations in coal mining areas. Accurately evaluating and predicting the degree of surface damage induced by coal mining with reasonable and correct indexes are of great significance to the restoration and treatment of the ecological environment. In this paper, these methods including the unmanned aerial vehicle aerial photography and manual measurement were used to investigate the development characteristics of surface damage caused by 2# coal seam mining in Yangchangwan Coal Mine. The results showed that with the change of mining conditions, the characteristics of surface cracks change obviously, which can be adopted to indicate the degree of surface damage. Thus, based on the results of the investigation, the classification standard of surface damage degree was established based on the evaluation indexes including density of crack, drop height of surface crack, crack width, maximum surface subsidence, and geological disaster caused by cracks and the damage characteristics of buildings. The evaluation method and process of surface damage degree also were given. Based on the ratio of the buried depth to the thickness of the coal seam (H/M), ratio of the thickness of overlying bedrock to the thickness of the coal seam, the thickness of loose layers (Ms), geomorphology, distance to faults, and distance to folds, the prediction model of surface damage degree was built on the GIS platform. The weight coefficient of each prediction index was obtained by the analytic hierarchy process (AHP) method. The surface damage degree map of 2# coal seam in Yangchangwan Coal Mine was divided into four classes: very minor, minor, moderate, and serious, which provides a relatively applicable method for the prediction of surface damage degree in Yangchangwan Coal Mine and its adjacent mining areas.