Surface subsidence and its reclamation of a coal mine locating at the high groundwater table, China

Underground mining leads to surface subsidence, vegetation degradation and environment damage. In order to mitigate such negative influences, this study focuses on subsidence characteristics and reclamation methods of the second coal mine in Zhaogu mining area. Due to high groundwater table at the mine, post-mining land is divided into submerged and damaged zones. Zone boundaries are identified, respectively, by using Unmanned Ariel Vehicle (UAV) monitoring. The submerged area reaches 350 hectares, and average distance between the referred boundaries reaches 200 m. Three-dimensional subsidence basin is reconstructed based on unmanned ship (US) monitoring and real-time kinematic (RTK) monitoring. The basin shape is strongly influenced by overburden composition, mining method and mining sequence. The basin depth presents a decreasing trend in eastern-to-western and southern-to-northern directions. Due to caving and compacting behaviors of thick soil layer, surface subsidence coefficient is larger than 1.0. Both UAV, US and RTK measurements indicate that surface subsidence is characterized by large basin size, great variation in basin depth, long-term subsidence duration and large subsidence coefficient. For realizing diversified usage of the post-mining land, the submerged zone is divided into two sections. Eastern section is reinforced to be a water reservoir for preventing drought and flood accidents. An innovative algorithm is proposed for evaluating water-bearing capacity. Western section is further divided into three areas for purposes of aquaculture, fishing and boating, respectively. The damaged zone is modified into afforested areas, board and lodging areas, and picking gardens. The reclamation work achieves desired environmental and economic effects.