Numerical investigation of processes, features, and control of land subsidence caused by groundwater extraction and coal mining: a case study from eastern China

Land subsidence is a typical geological disaster that will produce many secondary disasters and negatively impact human production and life. Human engineering activities (underground mining and coal mining) are the leading causes of land subsidence. This study takes Jining, a typical land subsidence city in eastern China, as a case study to investigate the features and control of land subsidence under the combined action of groundwater extraction and coal mining. A three-dimensional numerical model of land subsidence considering groundwater extraction and coal mining is established. The evolution process of land subsidence in the study area from 2000 to 2020 under the action of groundwater extraction and coal mining was obtained through numerical simulation. Results showed that coal mining was the main cause of land subsidence compared to groundwater extraction in the study area. Different groundwater extraction schemes were proposed to try to control the land subsidence, and the land subsidence features of different schemes from 2021 to 2030 were also investigated. Results showed that the ground rebound phenomenon occurred during the first few years, and the rate and amount of ground rebound decreased over time. After that, land subsidence continued, and its rate gradually slowed. The more mining wells are shut down, the smaller the final cumulative land subsidence will be. According to the comparison of these schemes, the land subsidence is basically stable when the amount of groundwater exploitation wells is closed by 50%, which is a more reasonable and practical exploitation scheme.