盾构隧道联络通道涌水涌砂诱发结构倒塌试验

Experimental Study on the Segmental Tunnel Collapse Induced by Water and Sand Inrush in the Connecting Passage

国内外盾构隧道建设施工过程中发生过多起由于局部涌水涌砂进而诱发结构倒塌的事故,造成巨大的经济损失。由于隧道倒塌事故具有突发性与隐蔽性的特点,针对盾构隧道结构倒塌的发展过程与力学机理的研究尚处于起步阶段,难以针对性提出有效的防控措施。为了探明盾构隧道联络通道涌水涌砂进而诱发结构倒塌的机理,为后续防控措施提供理论基础,以上海地铁4号线事故案例为研究背景,设计并开展了盾构隧道联络通道涌水涌砂诱发结构倒塌的模型试验,重现了盾构隧道倒塌的发展过程,对倒塌过程中的地层响应与隧道响应进行了讨论,进而提出隧道渗漏诱发结构倒塌的发展过程与原因。结果表明:①隧道渗漏后渗流侵蚀作用在外部地层产生土洞,土洞在形成→失稳→再现的过程中向地表发展;②地层土拱效应造成隧道外荷载重分布,进而引发隧道结构大变形;③土洞达到临界高度时地表土体失稳坠落,冲击荷载造成隧道结构倒塌,试验中最大冲击荷载达到正常水土荷载的13倍;④初步提出用于计算隧道受冲击荷载的理论计算公式。

Several tunnel collapse accidents caused by water and sand inrush during the construction of shield tunnels have resulted in significant economic losses.Due to the sudden and concealed nature of these accidents,research on the development process and mechanism of shield tunnel collapses is still in its early stages,making it challenging to propose effective preventive measures.To explore the mechanism of segmental tunnel collapse induced by water and sand inrush in connecting passages and provide a theoretical basis for subsequent prevention measures,a model test was designed and conducted,using the accident case of Shanghai Metro Line 4 as the research background.The development process of tunnel collapse was reproduced,and the responses of the strata and tunnel during the collapse were analyzed.The study proposed the development process and causes of structural collapse induced by tunnel leakage.The results indicate that:①Seepage erosion following tunnel leakage creates soil caves in the external strata,which develop to the ground through a process of formation,destabilization,and reproduction;②The soil arching effect causes load redistribution outside the tunnel,leading to significant deformation of the tunnel structure;③When the soil caves reach a critical height,the top soil destabilizes and falls,and the impact load causes the tunnel structure to collapse.The maximum impact load observed in the test was 13 times the normal soil and water load;④A preliminary theoretical formula for calculating the impact load on the tunnel is proposed.