关键词: 隧道工程;管棚;超前支护;弹性地基梁;有限差分法;

Abstract: As an important reinforcement measure in tunnel construction，pipe roofs are widely used in various engineering practices.However，the research on the mechanism of pipe roofs and its support effect in construction is still far behind the actual engineering needs.Many design theories and engineering practice are mostly based on engineering analogy and empirical methods，and the design parameters lack theoretical basis.Therefore，based on the interaction between surrounding rock and supporting structure，a mechanical analysis model of pipe roof was established by using the beam theory of two-parameter elastic foundation，and the finite difference method was used for theoretical solution.Combined with the example of Beijing-Shanghai high-speed Railway tunnel project，the deformation，stress，load transfer law of pipe roof support in the process of tunnel excavation were analyzed in depth，and the influence of factors such as sleeve arch，pipe diameter，pipe spacing and tunnel face reinforcement on pipe roof load transfer and support effect was further studied.The results show that the main mechanism of the pipe roof is to reduce and transfer the load released by the surrounding rock，which effectively limits the deformation of the surrounding rock in front of the face.The sleeve arch has a good control effect on the initial settlement of the pipe roof.The larger the diameter of the pipe roof，the larger the stiffness，and the smaller the settlement of the pipe roof.The larger diameter of the pipe roof and the smaller pipe spacing are more conducive to promoting the stability of the tunnel face.The tunnel face effect reduces the bearing capacity of surrounding rock on the tunnel face by about 7%，and the main reduction area is within 1.8 m in front of the tunnel face.Strengthening the tunnel face not only improves the bearing capacity of surrounding rock，but also improves the stress condition of the pipe roof and effectively controls the settlement of the pipe roof.The research results can provide a theoretical basis for studying the mechanical behavior，action mechanism and suitable surrounding rock conditions of pipe roof，and a reference for the design and construction of tunnel pipe roof in complex environment.

Key words: tunnel project；pipe roof；advanced support；elastic foundation beam；finite difference method