In some megacities, urban subway and municipal engineering are developing in the tendency of large cross-section and great buried depth, which brings a series of challenges to the design and construction of underground engineering. The mechanical characteristics and failure mechanism of tunnels have been paid more and more attention. Based on Xietaizi Subway Station tunnel in Chongqing, China, the paper carried out a geo-mechanical model test to simulated partial excavation processes of the large cross-section tunnel, integrating the resultant disturbances from partial excavation. The deformation and stress characteristics of the tunnel under different buried depths are analyzed, and the failure mechanism of large cross-section tunnel lining is investigated. The reliability of the research results is verified by the geo-mechanical model test and numerical simulation. The results indicate that under the pressure of the surrounding rock, the tunnel lining adjusts its internal forces primarily through deformation before transitioning to cracking, and retains earing capacity after the first crack appears. The tunnel structure experiences a process characterized by ‘elasticity-plasticity-injury-failure’. The tunnel section exhibits a ‘flattening’ deformation trend. The invert cracks are primarily distributed within a range of 0.5 times the tunnel span, while the vault cracks are mainly concentrated at the mid-span. Ultimately, the tunnel structure is compromised by the fracture of the invert’s middle section.

中文翻译：

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深埋大断面地铁站隧道破坏机理：地质力学模型试验与数值研究


在一些特大城市，城市地铁和市政工程正朝着横截面大、埋深大的趋势发展，这给地下工程的设计与施工带来了一系列挑战。隧道的力学特性和破坏机理越来越受到重视。本文以重庆市协台子地铁站隧道为基础，进行了地质力学模型测试，模拟了大型断面隧道的部分开挖过程，整合了部分开挖产生的扰动。分析了不同埋深下隧道的变形和应力特性，研究了大断面隧道衬砌的破坏机理。通过岩土力学模型试验和数值模拟验证了研究结果的可靠性。结果表明：在围岩的压力下，隧道衬砌在过渡到开裂之前主要通过变形来调节其内力，并在第一次出现裂缝后保持了凸耳能力。隧道结构经历了一个以“弹性-塑性-损伤-失效”为特征的过程。隧道截面呈现“扁平化”变形趋势。拱形裂缝主要分布在隧道跨度的 0.5 倍范围内，拱顶裂缝主要集中在跨中段。最终，隧道结构因井底中段的断裂而受到损害。