Experimental research on macroscopic and mesoscopic evolution mechanism of land subsidence induced by groundwater exploitation

Land subsidence induced by groundwater exploitation is a typically multi-scale and multi-field coupling process. The adjustment process and action mechanism of soil mesostructure play a decisive role in the characteristics and development of land subsidence. To reveal the essential mechanism of land subsidence induced by groundwater exploitation, a physical model experimental system is developed. Corresponding experiments are carried out on the mesostructural characteristics and evolution processes of sand particles under different pumping rates. The particle image velocimetry (PIV) technology is introduced to analyze the mesoscopic evolution mechanism of the whole process of land subsidence. The macroscopic and mesoscopic deformation characteristics and subsidence rates of soil are compared and analyzed. The results show that: (1) Hydraulic replenishment conditions play a crucial role in the characteristics of land subsidence; (2) with the increase of pumping intensity, the subsidence rate of sand surface increases first and then decreases, and the cumulative land subsidence continues to increase; (3) in the process of water pumping, the sand particles mainly migrate downward and toward the center of the well with the well as the axis of symmetry. The migration rate of particles at the surface is higher than that at the bottom, and the migration rate of particles far away from the pumping well is higher than that near the pumping well; (4) the whole development process of land subsidence generally includes four stages: surface subsidence starting, subsidence funnel forming, subsidence extending to the peripheral area, and finally overall subsidence.