Development characteristics and treatment methods of mining surface cracks in shallow buried coal seam gully

The surface crack induced by the mining of shallow coal seams is a kind of serious hazards in the Loess Gully area.In the shallow coal seams buried under the surface trench bottom,the trench where coal seams are buried shallow,the surface cracks will connect to the cracks in the rocks above the coal seam easily.The water channel may cause the surface water flowing down into underground coal mine.In order to study the characteristics of the surface cracks caused by the mining in shallow buried coal seams in the Loess Gully Region and the prevention methods of the ground water hazard,the Caigou section of the 125203 working face of Anshan Coal Mine was taken as the research object.Remote sensing technology and the field survey were adopted to study the plane distribution law and dynamic development law,and analyze its relationship with the production progress of the working face.Then,a zonal treatment method for different areas of the surface cracks in the trenches was proposed and applied on site by investigating the geological conditions of the trenches.The research shows that the cracks with parallel cuts at the bottom of the trenches are mostly developed in a “stepped” manner.The parallel cuts of surface cracks with a width of less than 5 cm account for 64%,surface cracks with a width of 5-10 cm account for 20%,and surface cracks with a width of 10-20 cm account for 10%.Surface cracks with a width of more than 20 cm account for 6%.Besides,the dynamic surface cracks at the forefront develop at the stop line in mining.The leading or lagging mining location is less than 6 m,and the cracks angle is approximately vertical to horizontal plane of coal roof.With the advance of working surface,the cracks on the forward slope show the dynamic characteristics of “cracking-stability”,and the cracks on the reverse slope show the dynamic characteristics of “cracking-closing-stable”,with an average dynamic change time of 3.7 days.The trench bottom cracks appear following the development trend of cracking-partially closed-partially cracked-stable and average development time is about 5.25 days,indicating that the surface crack development process in the shallow coal seam area has a certain self-healing ability.Based on the topography and geomorphological characteristics of the trench bottom,the characteristics of surface crack with parallel cuts development and land use methods,the regional governance areas can be divided into four types,and the targeted prevention and control methods for channel water damage in different areas were proposed.Additionally,the application results of engineering practice show that the zoning treatment method proposed in this paper can prevent the water damage caused by ground surface cracks in the trenches feasibly and effectively.