新建双线盾构隧道下穿既有隧道近接影响分区及控制措施案例研究

A Case Study on Adjacent Impact Zoning and Control Measures for New Double-line Shield Tunnel Undercrossing Existing Tunnel

为探究不同近接度下新建隧道下穿施工对既有隧道结构造成的影响,以成都地铁30号线下穿既有成自高铁锦绣隧道为依托工程,采用理论研究的方法提出近接影响度表达式,并通过结构位移判别准则确定分区控制标准。采用数值模拟、回归分析的方法,对下穿施工近接影响范围进行量化分区,并对不同影响分区提出针对性控制措施。结果表明,既有隧道管片最大沉降值与新建隧道和既有隧道之间的净距、新建隧道左线和右线之间的间距都呈负相关;针对在强影响区中施工提出“门式”保护结构,可将既有隧道管片最大沉降值折减77.10%,针对在弱影响区中施工提出新建隧道管片壁后注浆加固,可将既有隧道管片最大沉降值折减56.86%。监测结果表明,采取合理的施工控制措施,可有效控制既有隧道结构的位移,将既有隧道管片最大沉降值控制在预警值6 mm内。

In order to explore the impact of new undercrossing tunnel on the existing tunnel structure under different adjacent degrees,based on the Chengdu Subway Line 30 undercrossing the existing Jinxiu Tunnel on ChengduZigong High Speed Railway,the expression for adjacent impact degree is proposed by the theoretical research method,and the impact zoning control standard is determined by the structural displacement discrimination criteria.Numerical simulation and regression analysis methods are used to quantify and zone the adjacent impact range of the undercrossing construction,and targeted control measures are proposed for different impact zoning.The results show that the maximum settlement of existing tunnel segments is negatively correlated with the net distance between the newly-built tunnel and the existing tunnel,as well as the separation distance between left and right lines of the newly-built tunnel.A"gate"type protection structure is proposed for construction in the strong impact zone,which can reduce the maximum settlement of existing tunnel segments by 77.10%.For construction in weak impact zones,grouting reinforcement is proposed behind new tunnel segment walls,which can reduce the maximum settlement of existing tunnel segments by 56.86%.The monitoring results indicate that reasonable construction control measures can effectively control the displacement of the existing tunnel structure,and control the maximum settlement of the existing tunnel segment within the warning value of 6 mm.