Deformation characteristics of deep foundation pit with suspended waterproof curtain during excavation

Dewatering conditions have an important influence on the deformation characteristics of foundation pit excavation. In order to study the deformation problem during foundation pit excavation under the condition of a wall-well system consisting of suspended waterproof curtain combined with confined partially penetrating well, this study takes a deep foundation pit with suspended waterproof curtain as an example, uses the finite element numerical analysis to establish a 3D fluid-solid interaction model, and takes into account the actual working conditions of graded dewatering during the pit excavation by defining the seepage boundary conditions of the dewatering well and the surface. The monitoring data and simulation results are combined to explore the variation features of underground diaphragm wall deformation and surface settlement with suspended waterproof curtain, and the surface settlement under the conditions of suspended waterproof curtain and drop waterproof curtain is further compared and analyzed. The results show that in dewatering process of the foundation pit at all levels, the horizontal displacement increment of the underground diaphragm wall is the greatest with the most of the surface subsidence as the dewatering depth reaches the first confined aquifer. The maximum surface settlement generated by foundation pit with suspended waterproof curtain is about 2.7 times that with drop waterproof curtain, with the greater 0.8 m of the maximum surface settlement location. At the peak of horizontal displacement of underground diaphragm wall, the displacement during dewatering accounts for 28%, and at the peak of surface settlement, the settlement during dewatering accounts for 49%. When the suspended waterproof curtain is used at 12 times the excavation depth from the edge of the diaphragm wall, the ratio of surface settlement to the peak of surface settlement is 0.1, which is about 13 m greater than that of the drop waterproof curtain. The research results are of a reference value for determining the deep foundation pit dewatering scheme and ensuring the safety of deep foundation pit excavation construction.