Use of cross wall to restrict enclosure movement during dewatering inside a metro pit before soil excavation. (June 2021)

• Record Type: Journal Article
• Authors: Zeng, Chao-Feng; Xue, Xiu-Li; Li, Miao-Kun
• Is Part Of: Tunnelling and underground space technology. Volume 112(2021)
• Publication Date: 2021-06
• Subjects: Deep excavation -- Dewatering -- Enclosure deflection -- Cross wall -- Groundwater seepage -- Numerical analysis; Tunneling -- Periodicals; Underground construction -- Periodicals; Tunnels -- Periodicals; Underground areas -- Periodicals; 624.193
• DOI: 10.1016/j.tust.2021.103909
• Languages: English
• ISSNs: 0886-7798

Abstract

Highlights: 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 ( C s ) significantly affects the deformation restraining effect. We obtain a critical C s within which pit deformations can be effectively limited. We raise schemes to help better design cross wall to limit pit deformation. Abstract: 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 ( C s ) on the deformation control is discussed. The results indicate that with C s reduced, the maximum enclosure deflection ( δ hm ) and surface settlement ( δ vm ) get smaller, whereas there exists a critical C s (approximately 3 times the foundation pit width), within which the cross wall plays a significant role in restraining δ hm and δ vm . However, with C s being larger than the critical spacing, the C s effects on δ hm and δ vm become weak.