为研究隧道超前长管棚的承载机制和结构响应，考虑管棚搭接和两端支承条件的影响，建立超前长管棚力学响应理论模型，基于有限差分原理给出管棚不同位置挠度的计算方法。利用所建模型分析不同管棚直径、不同开挖步距和考虑管棚搭接对管棚挠度变化的影响规律。以厦门第二西通道海沧隧道为工程背景，对该隧道合理开挖步距进行优选。计算结果表明： 1）所建模型相较于现场试验结果的最大误差仅为8.14%；相较于不考虑管棚搭接的悬臂梁模型，考虑管棚搭接可以消除管棚挠度不合理上拱的现象。 2）随着管棚直径不断增大，管棚最大挠度逐渐降低，但降低效果逐渐减弱。 3）海沧隧道开挖步距为1.2 m时，相较于无管棚时拱顶挠度降低67.35%，并调整初期支护最大主应力至更加均匀的状态。
The authors establish a
theoretical model for the mechanical response of advance long-pipe roofs, considering the influence of pipe roof overlap and
support conditions at both ends. Using the finite difference principle, a
calculation method for deflection at various pipe roof positions is developed.
The model examines the influence of pipe roof diameter, excavation spacing, and
pipe roof overlap on deflection changes. Furthermore, a case study on the
Haicang tunnel in the Xiamen Second West Passage is conducted to optimize its
reasonable excavation spacing. The results indicate the following: (1) The
maximum error of the proposed model is only 8.14% compared to the field test
results, and pipe roof overlap eliminates the unreasonable upward arching of
deflection. (2) Increasing the pipe roof diameter gradually decreases the
maximum deflection, but the reduction effect weakens. (3) At an excavation
spacing of 1.2 m in the Haicang tunnel, the crown deflection is reduced by
67.35% compared to that without a pipe roof, and the maximum principal stress
of the primary support is adjusted to a more uniform state.
