Use of cross wall to restrict enclosure movement during dewatering inside a metro pit before soil excavation

摘要

Field records have demonstrated that the dewatering before soil excavation can induce enclosure wall movement of up to 15 mm. Typically, this deformation is neglected and cannot be effectively restricted by the traditional support schemes. Recently, cross wall system is proposed to limit enclosure wall movement during soil excavation, whereas its effectiveness in restraining deformation during pre-excavation dewatering (PED) is unclear. In this study, the feasibility of cross wall in restricting pit deformations during PED is investigated numerically. The effect of cross wall spacing (Cs) on the deformation control is discussed. The results indicate that with Cs reduced, the maximum enclosure deflection (Ethm) and surface settlement (Etvm) get smaller, whereas there exists a critical Cs (approximately 3 times the foundation pit width), within which the cross wall plays a significant role in restraining Ethm and Etvm. However, with Cs being larger than the critical spacing, the Cs effects on Ethm and Etvm become weak.