Research on surface subsidence law in high-intensity mining of shallow buried with thick coal seam

Taking Daliuta Coal Mine in Western Shendong mining area as the engineering background, this paper selected typical shallow buried high-intensity mining panel 52307 to establish the observation station for surface movement. Combined RTK technology and 3D laser scanning technology for real-time monitoring, based on key layer theory and CISPM comprehensive surface subsidence prediction model software, the characteristics of surface movement and deformation, surface movement angular parameters and surface cracks in high-intensity mining of shallow buried was studied. The results showed that with the advance of the panel from the set-up room, the surface subsidence was small at the set-up room position and then increased suddenly and rapidly. Simultaneously, the subsidence curve became steep sharply. When the maximum subsidence value was reached, the subsidence velocity tended to slow down. The surface movement deformation was mainly concentrated in the middle of the panel, while the subsidence deformation around the panel and the influence range of surface movement was small. The surface movement angular parameters were quite larger in the Daliuta coal mine area, while the bedrock movement angle and boundary angle reached 87.7 ° and 84.1 ° respectively. The surface cracks caused by mining were in an overall “C” shape, mainly distributed in the middle of the panel. Then, As the working face continued to advance, the ground fissures continue to slowly extend, develop, and gradually close from the set-up room to the tailgate side, eventually forming a continuous surrounding "funnel" shape. Ground fissures always lagged behind the working face position and the lag distance of surface cracks increases linearly with the mining speed. According to the analysis of surface subsidence law and surface cracks development, it was concluded that under the condition of high-intensity mining of shallow buried with thick coal seam, due to the high mining intensity of the working face, fast advancing speed, single key layer structure and low occurrence horizon, the roof activity was intense and easy to slide and lose stability. As a result, it was appeared resulting in rapid convergence around the surface movement basin, serious damage in the middle, and intensive development of ground fissures.