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软弱围岩大断面隧道经常采用三台阶七步开挖法,其具有充分发挥大型机械效能、加快施工进度、降低造价等优点,在隧道施工中的应用逐渐增多。然而,与其他工法相比,三台阶七步开挖法仍具有一定的施工风险,如果施工控制措施不当,往往引起隧道变形量过大、甚至围岩失稳。本文试图利用土力学中的“拱效应”现象,对比其他施工工法,对三台阶七步开挖法施工力学特征进行分析探讨,提出该法施工的关键环节及对应施工控制措施,为工程应用提供一些借鉴。
The large-area tunnel with weak surrounding rock often adopts three-step seven-step excavation method, which has the advantages of giving full play to the large-scale mechanical efficiency, speeding up the construction schedule and reducing the cost. The application in tunnel construction is gradually increasing. However, compared with other construction methods, the three-step seven-step excavation method still has some construction risks. If the construction control measures are not properly implemented, the amount of deformation of the tunnel will often be too large, and the surrounding rock may even become unstable. This paper tries to use the “arch effect” phenomenon in soil mechanics to compare with other construction methods to analyze and discuss the construction mechanics characteristics of three steps and seven steps excavation method. It puts forward the key links of construction and corresponding construction control measures, Application to provide some reference.