Ground settlement caused by combining influence of excavation and dewatering in sand area is discussed in this paper. The soil seepage-stress interaction model in a deep excavation is established based on the modified Mohr-Coulomb model using finite element theory, in order to analyze seepage field and ground settlement surrounding the deep excavation caused by well dewatering and soil excavation. Total soil settlement, and ground settlement caused by soil excavation and dewatering individually are obtained from the numerical investigation. A case history in northeastern China is adopted in this study, and the results show that, impact scope of ground settlement caused by excavation and dewatering is about 3 times the excavation depth (He). The maximum settlement point of monitoring sections appears at a distance of 22m from the deep excavation, about 0.82–0.96 He. The ground settlement caused by soil excavation is dominant from 10m to 20m away from the deep excavation, while the ground settlement beyond 25m from the excavation is mainly caused by dewatering. Settlement caused by dewatering is kind of irreversible settlement, so the ground settlement of a deep excavation caused by well dewatering can not be ignored during design and construction of excavation engineering.
The foundation pit engineering, especially the deep and large foundation pit engineering in city projects. In shallow buried groundwater area, the underground aquifers will be exposed by foundation pit excavation, causing the foundation pit seepage failure. So it is extremely important to conduct dewatering before the pit excavation. In addition, seepage pressure caused by excavation dewatering will cause compression of the soils surrounding the excavation pit, and ground settlement caused by this phenomenon is also unignorable.