宁天城际盾构下穿国铁地基加固设计方案

Foundation Reinforcement Design of Metro Shield Tunnel Crossing underneath Existing National Railway

依托南京地铁S8宁天城际下穿宁启铁路工程,结合南京地质条件,研究新建地铁隧道下穿既有铁路线时,地铁隧道施工对既有铁路线的影响,提出在既有铁路线下方采用注浆加固的方法以规避风险,采用"桩+板"加固的方法预留后期铁路复线施工条件。研究结果表明,采用注浆加固时,地铁隧道双线贯通铁路线路最大沉降(6.9 mm)比不加固减小58.9%,铁路线路最大高低偏差(3 mm),比不加固减小51.3%,采用"桩+板"加固预留铁路复线扩建条件,桩板结构最大变形及内力均能满足规范要求。

Nanjing Metro S8 was used as a case to study the settlement of a railway foundation caused by the construction of the shield tunnel, and the influence of the expanded railway construction on the newly constructed subway tunnel. The author pro- poses that grouting should be used to reinforce the existing railway foundation and use pile ＋ plate to reserve space for the con- struction of the expanded railway foundation. The result shows that the largest settlement of the existing railway foundation is 6.9mm alter grouting reinforcement when the subway tunnel is completed, reducing 58.9% than conducting no measures; the largest line elevation difference is 3mm, reducing 51.3%. On the other hand, the largest deformation and internal force can meet the requirement of specification by using pile ＋ plate reinforcement to reserve space for the construction of the expanded railway foundation.