砂卵石地层浅埋盾构隧道开挖面稳定模型试验

为探究浅埋砂卵石地层对盾构开挖的响应及开挖面的稳定性规律,设计了土压平衡盾构精细模拟装置,并开展室内模型试验研究。试验分析了浅埋砂卵石地层盾构开挖面变形对地表沉降、沉降槽形态的影响,得到了开挖面的破坏模式及变形破坏细观过程,并与纯砂地层试验进行对比。研究结果表明:(1)不同空间位置土体对开挖面位移的敏感性不同,但土体的破坏规律相似;(2)随开挖面位移增大,地层沉降–开挖面位移曲线表现出不敏感阶段、缓慢线性沉降阶段、加速沉降阶段、快速线性沉降阶段等4个阶段的规律;(3)浅埋情况下土体未出现局部失稳,经历弹性变形、弹塑性破坏之后直接发展为整体失稳破坏;(4)砂卵石土沉降槽两侧在对称性上存在差异;(5)浅埋砂卵石地层中盾构开挖对侧面土体影响范围较小,对前方土体影响范围较大。

Model tests on face stability of shallow shield tunnels in sandy cobble strata

In order to study the response of shallow sandy cobble strata to shield excavation and face stability, an earth pressure balance shield model is designed to conduct the indoor model tests. The failure mode and detailed process of strata are observed in these tests. The regulation of surface settlement and feature of settlement through are analyzed based on experimental data. The results show that: (1) The soil in different spatial position have different sensitivities to face displacement, but have similar failure process. (2) With the increase of the face displacement, the ground settlement-face displacement curves exhibit the regulation of ground settlement, which can be divided into four stages as insensitive stage, slow-linear settlement stage, accelerate stage and fast-linear settlement stage. (3) The directly overall instability occurs after elastic deformation and elastic-plastic failure in the shallow tunnel, and local instability has not appeared. (4) The settlement trough of sandy cobble strata is not exactly symmetrical with the tunnel axis. (5) The influenced region of the shallow tunnel in sandy cobble stratum is smaller than that of the pure sandy one in transverse, while it is greater in the longitudinal direction.