Spatiotemporal Evolution Characteristics and Transfer Law of Land Subsidence in Sand-Clay Interbed Caused by Exploiting the Groundwater

The dynamic variation of deep groundwater level and the spatiotemporal evolution characteristics of land subsidence in Dezhou city were systematically analyzed based on a vast amount of monitoring data concerning groundwater level and land subsidence in this area. Taking the hydrogeological engineering characteristics in Dezhou city as the research background, a three-dimensional fluid–solid coupling model of land subsidence was established. The spatiotemporal evolution characteristics, transfer law, and essential reason of land subsidence in sand-clay interbed were analyzed and discussed by adopting the Biot’s poroelasticity theory, and the sensitivity analysis of soil parameters was carried out. The research results are as follows: (1) The soil shows different subsidence characteristics when pumping groundwater from different confined aquifers; (2) The land subsidence is smaller when pumping from the deeper and thicker confined aquifer, and the location of the maximum subsidence is not at the land surface; (3) The lower transfer rate of the additional stress in the aquifuge is the essential reason that the process of land subsidence has usually been lagged behind the pumping process; (4) The response degree and sensitivity of land subsidence to the main physical and mechanical parameters are different. The most sensitive parameter in aquifers is the permeability coefficient, followed by the elastic modulus, followed by the Biot–Willis coefficient and Poisson’s ratio. The most sensitive parameter in aquifuges is the elastic modulus, followed by the permeability coefficient, followed by the Biot–Willis coefficient and Poisson’s ratio.