浅埋大跨度隧道管棚支护进洞三维有限差分法分析

随着隧道施工“新奥法”的日趋成熟，超前大管棚支护是隧道施工中穿越软弱破碎围岩的一种有效的加固施工方法．本文在对管棚法在大跨度极浅埋破碎地层隧道开挖中的加固机理研究的基础上，以某大跨度隧道为例，利用三维有限差分法对隧道开挖后的受力、变形情况进行模拟，分别分析了有无管棚预加固措施对拱顶沉降的影响并与实测拱顶沉降值进行比较，得出管棚能显著抑制破碎围岩地层的变形及拱顶沉降，减少隧道初期支护的变形和受力，保证施工安全．

Three-Dimensional Finite-difference Method AnalysisAppliance to The Pipe-shed Entrance of Large Span Tunnel

With the construction technique of Austrian tunneling method (NATM) developing, exceeding large pipe-shed support is a kind of effective reinforce construction measurement which can traverse goneness and break wall rock in tunnel construction. The mechanism of tunnel excavation reinforcement for the large span tunnel with shallow depth and weak wall rock condition is analysed in this paper. The stress and deformation of tunnel excavation is simulated by using Three-Dimension Fast Lagrangian Method. And the results of vault settlement is compared based on pipe-shed reinforcement or not.The method of pipe-shed can clearly restrain deformation of arch sank which has weak wall rock condition, reduce the stress and displacement of tunnel initial support and provide the security reference for the construction work.