软黏土地层盾构隧道开挖面稳定性离心试验研究

针对软黏土地层中隧道开挖面稳定性开展离心模型试验,由远程控制模型推进模拟隧道开挖面被动渐进破坏。通过数字图像处理分析技术对开挖面被动渐进破坏模式进行了探究,结合相应数值模型对比,分析了开挖面极限支护压力以及地表变形规律。研究结果表明:在开挖面被动破坏状态下,隧道仰拱处首先出现与水平方向近似成45°+φ/2向上发展的滑动破裂带,当其发展接近隧道拱顶时,拱顶滑动破裂带形成,两滑动破裂带呈漏斗状向上逐步发展至地表;随着模型向前推进,开挖面压力前期呈现线性快速增长趋势,随后土压力增速逐步减小,开挖面压力值最终趋于稳定,分析确定软黏土地层开挖面被动破坏状态下的支护压力可控制在1~1.9倍的静止土压力;开挖面被动破坏会引起前方地表产生隆起。

Centrifuge Model Tests on Face Stability of Shield Tunneling in Soft Clay

A centrifuge model test is conducted for stability analysis of tunnel face in soft clay by using remote control of the tunnel face model to simulate progressive passive failure of the tunnel face. Through the digital graphic processing technique, the progressive passive failure model of the tunnel face is depicted. In addition, combined with corresponding numerical simulation, the limit support pressure and laws of surface deformation are studied. The results show that: under the condition of the passive failure model of the tunnel face, the first slide fracture zone which makes an angle of 45°+φ/2 to horizontal direction develops upward from the tunnel invert. When it draws near the tunnel vault, the second slide fracture zone develops from the tunnel vault, and the two slide fracture zones propagate in funnel-shape up to surface. As the tunnel face model moves forward, the monitoring pressure on the tunnel face increases linearly in earlier stage, then it grows slower, and finally approaches stable. The limit support pressure with passive failure model of the tunnel face in soft clay can be controlled in range 1~1.9 times of earth pressure at rest. The passive failure damage of tunnel face may cause ground heave.