浅埋大断面大跨度连拱隧道施工变形现场监测试验研究

结合浅埋大断面大跨度隧道工程实践，对浅埋大断面大跨度连拱隧道施工变形进行现场监测试验，分析隧道施工全过程及在不同开挖工序下的施工变形特点。研究结果表明：1)左、右洞上台阶开挖引起先行隧道变形较大，引起的后行左洞变形较其它工序要大；2)后行隧道施工对先行隧道变形影响较大；3)右洞上台阶开挖对右洞变形的纵向影响范围为隧道跨度的1/4，右洞下台阶及左洞上台阶开挖对右洞变形影响范围为隧道跨度的1/3，左洞上台阶开挖对左洞变形影响范围为隧道跨度的1/3；4)对于浅埋大断面大跨度连拱隧道，应及早施作二次衬砌，以控制隧道变形。研究成果可为日后类似工程的设计、施工和研究提供有益的借鉴和参考。

Experimental Study on Monitoring of Construction Deformation of Shallow-covered Large Cross-section and Large-span Double-arch Tunnel

Shallow-covered large cross-section and large-span double-arch tunnels have such characteristics as large span,shallow cover and frequent conversion of construction procedures.The multi-blast causes disturbance to the surrounding rock mass.Therefore,extensive monitoring of the tunnel is necessary.The contents,technique and method of the monitoring of the construction deformation of shallow-covered large cross-section and large-span double-arch tunnels are descried in detail.The deformation characteristics during the overall construction process and during different excavation stages are analyzed in detail.The following conclusions are drawn： 1） The excavation of the top heading of the left tube and the right tube changes the deformation of the preceding tube greatly.Especially the excavation of the top heading of the proceeding left tube causes larger deformation than the other procedures.Therefore,that procedure is the main point for ensuring the tunnel stability.2） The construction of the proceeding tube has some influence on the deformation of the preceding tube.Therefore,the disturbance effect of the proceeding tube should be paid attention to.3） The longitudinal incidence to the right tube deformation of the top heading excavation of the right tube is about 1/4 of the tunnel span and that of the bench excavation of the right tube and the top heading excavation of the left tube is about 1/3 of the tunnel span.As to the longitudinal incidence to the left tube deformation,the top heading excavation of the left tube is also about 1/3 of the tunnel span.4） The secondary lining must be timely installed to control the tunnel deformation.The experience and conclusions presented can be referred to in the design,construction and monitoring of similar works in the future.