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

• Published in: Tunnelling and underground space technology Vol. 112; p. 103909
• Main Authors: Zeng, Chao-Feng, Xue, Xiu-Li, Li, Miao-Kun
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.06.2021; Elsevier BV
• Subjects: Constraining; Cross wall; Deep excavation; Deformation; Deformation effects; Dewatering; Enclosure deflection; Enclosures; Excavation; Feasibility studies; Groundwater seepage; Numerical analysis; Soils; Studies; Tunnels; Enclosure deflection; Cross wall; Numerical analysis; Deep excavation; Dewatering; Groundwater seepage
• ISSN: 0886-7798; 1878-4364
• DOI: 10.1016/j.tust.2021.103909

•Pre-excavation dewatering (PED) with cross wall is simulated by numerical models.•The feasibility of cross wall in restraining pit deformations during PED is studied.•Cross wall spacing (Cs) significantly affects the deformation restraining effect.•We obtain a critical Cs within which pit deformations can be effectively limited.•We raise schemes to help better design cross wall to limit pit deformation. 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 (δhm) and surface settlement (δvm) 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 δhm and δvm. However, with Cs being larger than the critical spacing, the Cs effects on δhm and δvm become weak.