隧道三台阶开挖锁脚锚管倾角优化研究

跨度大、扁平率高的隧道在施工过程中拱顶沉降等控制要求十分严格,台阶法因其施工效率高、控制隧道变形能力较强等优点而被广泛采用。工程实际中若支护结构封闭较晚,隧道变形则较难控制,打设锁脚锚管是控制隧道变形的有效手段,然而目前关于锁脚锚管施工和设计方面的研究较少。以新疆石人子沟隧道为例,开展了锁脚锚管倾角优化分析。分析认为,上台阶锁脚锚管是施工控制的关键,锁脚锚管最优倾角范围为上台阶0°~45°、中台阶0°~56°、下台阶10°~60°;且从控制隧道变形的角度考虑,倾角在所述范围内应尽可能大,这与诸多现场经验结论较为吻合,相关成果可以为类似工程提供参考。

Dip angle optimization of feet-lock bolt in tunnel constructed by three steps excavation

Highway tunnel has the characteristics of large span and flat rate, so the crown settlement control is demanding in the construction process. The three-step excavation is widely used in tunnel construction because of its high construction efficiency and strong tunnel deformation control capability. If the supporting structure closed late in construction, the tunnel deformation would be difficult to control, and the feet-lock bolt is an effective way to restrain the deformation. However the research on feet-lock bolt is almost blank at present. Taking the Shirenzigou tunnel in Xinjiang as a case, the optimization of dip angle of feet-lock bolt was carried out. The analysis results indicate that the key of construction control is the feet-lock bolt construction in upper step, and the optimal angle range is 0~45° for the upper step, 0~56° for the second step, and 0~60°for the bottom step. In the above angle range, the angle should be as large as possible in view of controlling tunnel deformation, which is in good agreement with many field experiences.