College of Transportation Engineering, Nanjing Tech University, Nanjing, China.
Department of Civil Engineering, Dalian Maritime University, Dalian, China.
PLoS One. 2024 Sep 10;19(9):e0310111. doi: 10.1371/journal.pone.0310111. eCollection 2024.
The excavation of Earth Pressure Balance (EPB) shield can be divided into two distinct stages, i.e. advancing and lining installation. The frictional force applied on surrounding soils reverses at these two stages, which is harmful to the settlement control. Based on Mindlin's method, a new model of surface settlement is derived to involve the reversed friction. A closed form formula is then obtained for the major type of metro tunnels. Main operational parameters are also used as input of the formula. Numerous operational data and measured settlements are collected from EPB tunnels of Chengdu Metro, Line 7. The proposed formula is validated against these field data in sandy gravels. It is shown that the new formula gives reasonable prediction of surface settlement along the tunnel sections. The accuracy of new formula is significantly higher than that of Peck's formula. This study provides a new vision in settlement control of EPB shield tunneling. The increase of chamber pressure will induce higher negative friction during the lining installation. Therefore, surface settlement of EPB tunneling cannot be controlled by just increasing chamber pressure. A balanced relationship between the chamber pressure and the thrust should be maintained instead.
土压平衡（EPB）盾构机的挖掘可以分为两个明显的阶段，即推进和衬砌安装。在这两个阶段，作用在周围土壤上的摩擦力会发生反转，这对沉降控制是有害的。基于 Mindlin 的方法，推导出了一个新的包含反向摩擦力的地表沉降模型。然后为主要类型的地铁隧道获得了一个封闭形式的公式。主要的操作参数也作为公式的输入。从成都地铁 7 号线的 EPB 隧道中收集了大量的运营数据和实测沉降数据。该公式在砾石砂中对这些现场数据进行了验证。结果表明，新公式对隧道段的地表沉降有合理的预测。新公式的精度明显高于 Peck 公式。本研究为 EPB 盾构隧道沉降控制提供了新的视角。在衬砌安装过程中，增加气室压力会导致更大的负摩擦力。因此，仅仅通过增加气室压力不能控制 EPB 隧道的地表沉降。应该保持气室压力和推力之间的平衡关系。
