A hydromechanical EFG-based model for numerical simulation of land subsidence induced by groundwater extraction in anisotropic aquifers

Abstract

This study presents a coupled hydromechanical element-free Galerkin (EFG) model to simulate land subsidence induced by groundwater withdrawal. The EFG algorithm was validated with unsaturated hydraulic and hydromechanical benchmark problems, showing satisfactory agreement with the finite element method (FEM) and theoretical results. We qualitatively investigate the effects of groundwater pumping on land subsidence and hydraulic head variation in both isotropic and anisotropic aquifers, taking into account unsaturated effects. Our results indicate a nonlinear correlation between groundwater extraction and both decrease in hydraulic head and increase in land subsidence. In anisotropic aquifers, initial discrepancies are observed between the EFG and FEM models, although final land subsidence and hydraulic head values are closely aligned. Comparative results between the two methods show that, for the anisotropic aquifer, land subsidence and hydraulic head variation trends from the EFG method exhibit better agreement with those of the isotropic aquifer. A parametric study reveals that the elastic modulus and Poisson’s ratio significantly affect land subsidence levels. While hydraulic conductivity influences the rate of hydraulic head decline and onset of subsidence, it has a minor effect on steady-state values. These findings emphasize the importance of accurate in-situ measurements of elastic modulus and Poisson’s ratio for the precision and reliability of feasibility studies in groundwater extraction projects.