超大矩形顶管盾构隧道近接下穿高铁施工加固方案对比分析

Comparative analysis of construction reinforcement scheme of super large rectangular pipe jacking shield tunnel close to and under high-speed railway

为保证超大矩形顶管盾构隧道近接下穿高铁的施工安全,以某矩形顶管盾构涉铁工程为背景,研究软弱地层中超大矩形顶管盾构近接高铁施工的安全性。结果表明:软弱地层中超大矩形顶管盾构近接高铁施工时轨道沉降和管节安全系数远超控制阈值,必须采取施工加固方案;采取超前注浆可使轨道沉降减小58.20%,管节最小安全系数提高至1.35;采用人工挖孔桩+D型钢便梁可使轨道沉降减小63.05%,最小安全系数增至9.49;采用桩板结构加固可使轨道沉降减小70.90%,最小安全系数增至9.00;人工挖孔桩+D型钢便梁加固方案和桩板结构加固方案的效果明显优于超前注浆的加固效果,推荐在下穿待建高铁段采用桩板结构加固方案,在下穿既有高铁段采用人工挖孔桩+D型钢便梁加固方案。现场监测结果表明:超大矩形顶管盾构在近接下穿待建福厦高铁段采用桩板结构后,顶管掘进导致的地表沉降最大值为3.25 mm,在近接下穿既有杭深线段采用人工挖孔桩+D型钢便梁后,高铁轨道最大沉降仅为1.65mm,均远小于沉降阈值,超大矩形顶管盾构顺利近接下穿待建福厦线和既有杭深线。研究结论可为类似大尺寸隧道的近接工程提供参考。

To ensure the construction safety of super-large rectangular pipe jacking shield tunnel adjacent to the high-speed railway,based on an actual railway related project, the safety of super-large rectangular pipe jacking shield close to high-speed railway in soft stratum is studied. The results show that the track settlement and pipe segment safety factor far exceed the control threshold during the construction, so the reinforcement scheme must be adopted. The track settlement can be reduced by 58.20% and the minimum safety factor of pipe segment can be increased to 1.35 by adopting advance grouting scheme. Using manually dug pile and D-shaped beam can reduce the track settlement by 63.05% and increase the minimum safety factor to 9.49. After adopting the pile-plate reinforcement scheme, the track settlement can be reduced by 70.90% and the minimum safety factor can be increased to 9.00. The reinforced effects of manually dug pile and D-shaped beam scheme and pile-plate scheme is significantly better than that of advance grouting. It is recommended to adopt the pile-plate scheme in the section under the high-speed railway to be built, and the manually dug pile and D-shaped beam scheme in the section under the existing high-speed railway. The on-site monitoring results show that the maximum surface settlement caused by pipe jacking tunneling is 3.25 mm after the super-large rectangular pipe jacking shield passes through the Fuzhou-Xiamen railway section to be built. After the manually dug pile and D-shaped beam is adopted for the existing Hangzhou-Shenzhen section, the maximum settlement of the high-speed railway track is only 1.65 mm. Both track settlement and surface settlement are far less than the settlement threshold. The super-large rectangular pipe jacking shield successfully crosses the Fuzhou-Xiamen Railway and Hangzhou-Shenzhen Railway. The research conclusion can provide reference for similar large-scale tunnel proximity engineering.