小净距重叠盾构隧道下穿铁路线施工安全技术研究

Construction Safety Analysis of Overlapping Tunnels with Small Space Under Railway Lines

为了解决小净距重叠隧道下穿准高速铁路的安全施工问题,采用数值计算的方法,对上下重叠隧道不同施工顺序引起的地层变形、管片结构位移和受力情况进行分析。结果表明,采用“先下后上”开挖方式时,地表沉降、隧道管片结构竖向位移及其弯矩均小于“先上后下”开挖方式。当采用“先下后上”盾构掘进时,上隧道引起的最大地表沉降为13. 934 mm;采用“先上后下”时,最大地表沉降为15. 516 mm(沉降控制值为10 mm)。对铁路线路、上下隧道间夹层土体和铁路路基软土进行加固后,地表沉降数值计算值为9. 525 mm,实际观测最大值为5. 9 mm(均在控制值范围内)。该研究结论为重叠隧道顺利下穿准高速铁路施工提供了关键技术支持。

Based on the construction of overlapping tunnels with small spacing under high-speed railway lines using shielding tunneling method in Shenzhen Metro Line 7, the paper analysis the effects of different constructing sequences on the stratum deformation and displacement and stress distribution of lining segment structures by the use of numerical simulating tool. Analysis shows that the method of "excavating the lower tunnel first", which induces smaller ground surface settlement and vertical displacement and bending moment of segment structures, is more appropriate than the method of "excavating the upper tunnel first". The maximum ground surface settlement is up to 13.934 mm with the former method, while it's 15.516 mm with the later one (the mandatory limit is 10 mm). In practice, simulating data and monitoring data of ground surface settlement are within the scope of mandatory limits after the reinforcement of railway line, soft soil of railroad base and the soil between the upper tunnel and lower tunnel, the maximum ground surface settlement is 9.525 mm from simulating result while it is 5.9 mm from monitoring system.