Prediction of ground cracks induced by coal mining in Yangchangwan Coal Mine

Cracks in ground surface induced by coal mining are the common type of land destruction in coal mine areas,and are also a challenge for ecological restoration. Understanding the development characteristics of surfer cracks and predicting their development are important for managing coal mining subsidence. A case study was performed at Yangchangwan Coal Mine. Aerial photography,field investigation and theoretical analysis were performed to summarize the development rules and characteristics of surface cracks and reveal the relationship between mining geological conditions and the characteristics of surface cracks. The results show that the degree of crack gradually decreases with the depth of mining. When the mining depth is more than 350 m,the parallel cut cracks stop developing. The parallel channel cracks develop in the form of "ring-belts". When the mining depth is deeper than 550 m,the characteristics of cracks development are not obvious. The development range of surface cracks can be simplified into a combination of two semi-ellipses and one rectangle,and their scale can be calculated by the surface deformation parameters and the coal seam depth. The width of surface cracks decreases with the decrease of the ratio of mining depth to mining thickness. After fitting treatment,the formula for predicting the maximum width of surface cracks is obtained.