Ahmad Tourei , Ali Pak, Mohammadali Iranmanesh, Mohammadreza Naddafnia

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 alignment with finite element method (FEM) and theoretical results. We inves-tigated the effects of groundwater pumping on land subsidence and hydraulic head variation in both isotropic and anisotropic aquifers considering unsaturated effects. Our results indicate a nonlinear correlation between groundwater extraction and both hydraulic head decrease and land subsidence increase. In anisotropic aquifers, initial discrepancies were observed between the EFG and FEM models, although final land subsidence and hydraulic head values were closely aligned. Com-parison results show that EFG's land subsidence and hydraulic head decline trends for anisotropic aquifer exhibit a better agreement with the isotropic model compared with those of the FEM. The parametric study revealed 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.