Abstract: In response to the instability problem of support structures caused by seepage deformation coupling in deep excavation engineering in soft soil areas, a three-dimensional deep excavation model was established using Plaxis3D finite element software with a project in Jiangsu Province. The influence of the depth and width of the water cut-off wall on the deformation and seepage stability of the soldier pile was studied. The results show that the depth and width of the water cut-off wall exhibit a significant nonlinear threshold effect on the performance of the deep excavation supporting structures. When the depth is ≥20 m and the width is ≥0.8 m, the horizontal displacement of the soldier pile decreases by more than 30%, and the seepage velocity synchronously decreases by more than 70%. However, as the depth and width of the water cut-off wall further increase, the decrease in the horizontal displacement and seepage velocity of the soldier pile is limited; Based on the standard limits, the critical depth of the curtain is 19.0 m and the critical width is 0.68 m. The results provide theoretical basis and parameter optimization methods for seepage cut-off design of the deep excavations in soft soils.

Key words: Deep Excavation Engineering, Water Cut-off Wall, Deformation Control, Seepage Stability, Parameter Threshold