With the expansion of existing networks of underground system, many metro tunnels are excavated in a pair undercrossing existing tunnels. The new excavations will affect the stress distribution and settlement behavior of the existing tunnels, particularly when the clearance is small. Generally, the construction of the second undercrossing tunnel induces more settlement in the upper tunnels compared to that caused by excavating the first one, due to the interaction between the new excavations. The degree of interaction makes it difficult to predict the settlement of existing tunnels. In this paper, a simplified two-stage analysis method considering the interaction between the undercrossing twin tunnels is proposed to estimate the induced response of existing upper tunnel. In the first stage, the greenfield settlement caused by the first excavation is estimated using Peck’s empirical function, and that caused by the second excavation is modified with a modification factor to consider the influence of the first tunnel. In the second stage, the additional stress calculated using the greenfield displacement is imposed on the existing tunnel resting on Pasternak foundation model. The calculated settlement profile and bending moment of the existing tunnel using the two-stage analysis method are compared with those obtained from finite element analysis and historical field monitored data. The effects of the characteristic parameter of Pasternak foundation model, the spacing between the new twin tunnels, and the modification factor of greenfield settlement, on the settlement profile and bending moment of the existing tunnel are also investigated.

随着地下系统现有网络的扩展，许多地铁隧道在与现有隧道交叉的下方成对开挖。新的开挖将影响现有隧道的应力分布和沉降行为，尤其是当间隙较小时。通常，由于新的基坑之间的相互作用，第二条穿越隧道的施工与第一条挖掘造成的沉降相比，在上层隧道中产生了更多的沉降。相互作用的程度使得难以预测现有隧道的沉降。本文提出了一种考虑跨界双隧道之间相互作用的简化的两阶段分析方法，以估算现有上部隧道的诱发响应。在第一阶段 使用Peck的经验函数来估算由第一个开挖引起的未开发的沉降，并使用修正因子对第二个开挖引起的未沉降进行修正，以考虑第一条隧道的影响。在第二阶段中，使用未开发原野位移计算出的附加应力被施加在基于Pasternak基础模型的现有隧道上。将采用两阶段分析方法计算的既有隧道的沉降曲线和弯矩与从有限元分析和历史现场监测数据获得的沉降曲线和弯矩进行了比较。Pasternak基础模型的特征参数，新双隧道之间的间距以及未开发区沉降的修正因子的影响，