Predicting Wall Deformations for Deep Excavations Influenced by Confined Aquifer in Soft Deposits

ABSTRACT In coastal soft clay regions, confined aquifer hinders dissipation of pore water pressure at the bottom of the aquitard during excavation, reducing vertical effective stress in deeper layers. To accurately predict wall deformations in deep excavations, it is crucial to consider the impact of groundwater within the excavation zone. This study proposes a simplified beam spring method incorporating pore water pressure and nonlinear variations of subgrade reaction modulus. By combining the continuous drainage boundary with Melan's solution, a novel approach for determining the subgrade reaction modulus considering pore water pressure is derived. Furthermore, new incremental loads and modulus evolution are introduced into the beam spring method. The validity of the proposed method is verified through two excavation cases. A comparative analysis between calculated results and field data reveals that confined aquifer yields a low vertical effective stress at the bottom of the aquitard during deep excavation. The subgrade reaction modulus exhibits an increase‐decrease‐increase trend with depth, forming an R‐shaped distribution. Incorporating the effects of confined aquifer and soil nonlinearity on the subgrade reaction modulus during the design process can more effectively mitigate excavation risks and reduce construction costs.