To achieve the failure mechanism of face for slurry shield tunnel in sand stratum, a model test device for shield excavation with ideal slurry film was developed. The active failure processes of tunnel excavation face in dry sand stratum for different densities and cover depths were achieved through model test and two-dimensional particle flow code (PFC^2D). Furthermore, soil deformation, failure mode and soil arching effect of tunnel excavation face were revealed. The results show that the face deformation can be divided into three stages in relation to the support pressure and the excavation face has been failed in third stage. The density of sand has a great influence on the failure mode of excavation face. The failure mode in dense condition is a combination of a wedge with slip arc and a prism chimney, while in loose condition it is a relatively dispersed “trumpet” shape failure zone. However, the cover depth has a negligible effect on the failure mode. In dense sand stratum, a loose failure zone was formed in front of the excavation face and a soil arch was formed above it. The soil arch developed continuously above the tunnel crown to the ground surface. The limit support pressure calculated by PFC^2D (two-dimensional particle flow code) increases with the cover depth, which is consistent with the observations in model tests.

为实现砂层泥浆盾构隧道工作面破坏机理，研制了理想泥浆膜盾构开挖模型试验装置。通过模型试验和二维颗粒流代码（PFC ^2D），获得了不同密度和覆盖深度的干砂地层中隧道开挖面的主动破坏过程。）。揭示了隧道开挖面的变形，破坏模式和拱效应。结果表明，相对于支撑压力，工作面变形可分为三个阶段，而在第三阶段开挖工作面已失效。砂的密度对开挖面的破坏方式有很大的影响。在致密状态下的破坏模式是楔形滑弧和棱形烟囱的组合，而在松弛状态下，它是相对分散的“喇叭”形破坏区域。但是，覆盖深度对失效模式的影响可以忽略不计。在致密的砂岩层中，开挖面的前面形成了一个松散的破坏带，而开挖面的上方则形成了土拱。土拱在隧道拱顶上方不断发展到地面。^2D（二维粒子流代码）随覆盖深度的增加而增加，这与模型测试中的观察结果一致。