Accurate prediction of surface settlement induced by tunnel excavation is significant for preventing damage to existing structures under complex geological conditions. The Peck formula is currently considered as an efficient solution for surface settlement prediction. This paper proposes a modified Peck formula considering geological conditions to improve the accuracy of surface settlement prediction of twin tunnels. The asynchronization of the sinking rate and stability of the vault settlement and surface settlement within the river-affected area may attribute to the groundwater drawdown caused by cofferdam construction on the river. A modified Peck formula is put forward with soil permeability and width-controlling parameters involved. There is a small settlement at the center of the twin tunnels, making the settlement trough upward buckling, which is like a “W” shape. This situation can be accurately predicted by the modified formula with a significantly increased adjusted R-square. The modified formula can accurately predict the surface settlement of tunnels excavated in low permeability soil layers with a permeability coefficient between 10⁻⁴ cm/s and 10⁻⁷ cm/s, especially in the groundwater drawdown environment. The reliability of the modified Peck formula is verified by other cases in Nanjing and Singapore.

中文翻译：

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修改Peck公式以预测低渗透土壤中双隧道的地表沉降

隧道开挖引起的地表沉降的准确预测对于防止复杂地质条件下现有结构的破坏具有重要意义。目前，Peck公式被认为是表面沉降预测的有效解决方案。提出了一种考虑地质条件的修正派克公式，以提高双隧道地表沉降预测的准确性。受河流影响的区域内下沉速率的不同步性和拱顶沉降和地表沉降的稳定性可能归因于在河上围堰建设引起的地下水抽取。提出了修正的Peck公式，并考虑了土壤渗透率和宽度控制参数。双隧道的中心有一个小的沉降，使沉降槽向上弯曲，就像一个“ W”形。这种情况可以通过带有显着增加的调整R平方的修改公式来准确预测。修正后的公式可以准确预测低渗透率土层中开挖的隧道的地表沉降，其渗透系数在10之间。^-4  cm / s和10 ^-7  cm / s，尤其是在地下水位下降的环境中。南京和新加坡的其他案例也验证了修改后的Peck公式的可靠性。