双线盾构隧道下穿既有地铁车站沉降控制技术研究

Settlement control technology of double line shield tunnelling undercrossing existing metro station

随着城市地下交通的发展普及,地铁交通作为常用出行方式,盾构隧道下穿地铁车站的工程越来越多,盾构在不引起较大位移沉降及变形超限的基础上切磨既有地铁车站围护桩是目前盾构施工的新挑战。文中以广州地铁12号线官洲站—大学城北站盾构区间下穿既有地铁4号线为研究背景,研究富水条件下新建盾构隧道下穿既有运营地铁、切磨围护桩的施工要点。分别从盾构机针对性设计、盾构下穿提前控制及盾构下穿过程控制3方面辅助盾构机顺利磨桩;采取上述措施后,既有地铁4号线最大沉降量为4.54 mm,最大水平位移为3.5 mm,满足车站沉降控制要求。研究表明,对盾构机刀盘采取针对性改造、使盾构慢速推进、优化渣土改良剂等方法可有效控制磨桩引起的车站变形,以及减少既有车站结构与隧道结构间的差异沉降,为后续盾构下穿既有地铁工程提供参考。

With the development and popularization of urban underground traffic,metro traffic is a common trip mode,and more and more projects of shield tunnelling undercrossing metro station are carried out.Cutting and grinding the existing retaining piles of metro station without causing large displacement settlement and deformation overrun is a new challenge for shield construction at present.Based on the research background of shield section between Guanzhou Station and University Town North Station of Metro Line 12 undercrossing the existing Metro Line 4,we studied the construction key points of new shield tunnelling undercrossing the existing metro and cutting and grinding the retaining piles under the condition of rich water.The shield tunnelling machine was assisted to grind the pile smoothly from three aspects of shield tunnelling machine's targeted design,shield tunnelling advance control and shield tunnelling process control respectively.After taking the above measures,the maximum settlement of existing Metro Line 4 was 4.54 mm and the maximum horizontal displacement was 3.5 mm,which met the station settlement control requirements.The research shows that the station deformation caused by grinding pile and the differential settlement between the existing station structure and the tunnelling structure can be effectively controlled by the targeted transformation of the cutter head of the shield machine,the slow advance of the shield,and the optimization of the mule modifier,which provides a reference and advise for the subsequent construction of the shield undercrossing the existing subway.