基坑开挖施工对超近距离下卧既有盾构隧道的保护技术研究

Protection Technology for Underlaid Shield Tunnel: A Case Study of Ultra-close Foundation Pit Excavation

为确保超近距离下卧既有盾构隧道的安全,以实际工程为背景,采用结构分析、理论计算和监控量测等方法,针对基坑开挖施工对下卧既有盾构隧道的保护技术进行了研究,主要包括:1)结合上部基坑开挖施工工况,利用计算软件分析不采取措施时下卧隧道的内力转换及变形,发现随着基坑开挖施工,管片结构内力虽先增大后减小,但增大的幅度有限,对安全不起控制作用,下卧隧道的安全主要受变形控制;2)为有效抑制基坑开挖施工引起的超近距离下卧既有盾构隧道的变形,分别研究隧道内设置抗浮锚杆、隧道侧设置隔离桩、隧道内增设临时支撑及配重等技术措施对抑制隧道变形的作用,发现隔离桩+临时支撑+配重措施效果最好,隔离桩措施次之,抗浮锚杆措施效果最差;3)根据研究成果,提出下卧隧道保护设计方案,并应用于工程实际,以期能为类似工程提供参考。

In order to guarantee the safety of the ultra-close underlaid shield tunnel, the protection technologies arestudied by adopting structural analysis, theoretical calculation and monitoring method during foundation pit excavation.The study results show that： 1） The internal force conversion and deformation of underlaid shield tunnel is analyzed byusing calculation software under protection condition; the internal force of the tunnel segment increases firstly and thendecreases with foundation pit excavation, of which the increasing range is limited; the internal force of the shield tunneldoes not affect the safety control, but the deformation of the shield tunnel plays an important role in safety control. 2）The effects of uplift anchor bolt in tunnel, separation pile at tunnel side, temporary support in tunnel and balance weighton shield tunnel deformation control are studied; the deformation control effect of separation pile ＋ temporary support ＋balance weight is the best, followed by that of separation pile, and that of the uplift anchor bolt is the worst. 3） Theshield tunnel protection technologies are put forward and applied to practice. The results can provide reference forsimilar projects in the future.