基于传递矩阵的平顶直墙地铁车站横向管棚受力变形计算方法研究

平顶直墙地铁车站PBA工法施工可以采用管棚先行支护。针对PBA法暗挖平顶直墙地铁车站密布横向管棚结构，通过总结管棚“荷载－梁模型”中弹性地基梁、简支梁、固支梁3种简化方法及其计算原理，以北京地铁19号线平安里站工程为背景，采用上述3种模型计算管棚受力变形，并与实测值进行比较分析，然后针对不同工程参数和地质参数进行受力变形影响分析。结果表明： 1）弹性地基梁模型计算弯矩和跨中挠度处于固支梁模型和简支梁模型计算结果之间，其中弹性地基梁模型和简支梁模型计算结果较符合实测数据；但简支梁模型和固支梁模型无法体现导洞侧壁处挠度，且无法体现地层参数的影响以及钢管壁厚对受力的影响。2）最大弯矩值出现在简支梁的跨中，建议在设计时以简支梁模型计算跨中弯矩进行包络，以保证施工安全。3）开挖跨度和覆土厚度（荷载）对弯矩和挠度影响较大，其中跨度影响最大。4）基床系数和钢管壁厚对管棚弯矩影响较小，但对减小挠度有一定作用。

Research on Calculation Method for Stress and Deformation of Transverse Pipe Roof in Subway Station with Rectangular Cross section Based on Transfer Matrix

The pipe roof support can be used in metro station with rectangular cross section constructed by PBA method in advance. The transverse pipe roof is densely arranged in PBA mined metro station with rectangular cross section. Firstly, the simplified methods and calculation mechanisms of elastic foundation beam, simply supported beam and clamped beam of the "load beam model" of pipe roof are summarized. And then, the three models of elastic foundation beam, simply supported beam and clamped beam are used to calculate the stress and deformation of pipe roof of Ping′anli Station on Beijing Metro Line No. 19, and the calculation results are compared with monitoring results. Finally, the influence factor analysis is carried out on stress and deformation of pipe roof of different projects with different geological parameters. The research results show that: (1) The bending moments and mid span deflections calculated by elastic foundation beam model are between the results calculated by clamped beam model and simply supported beam model, and the results calculated by the elastic foundation beam and the simply supported beam model are more consistent with the measured data; however, the models of simply or clamped supported beam can not reflect the deflection at the sidewall and the influence of the formation parameters and the pipe thickness. (2) The maximum bending moment occurs in the mid span of simply supported beam, thus the security can be ensured by using mid span moments of simply supported beams. (3) The excavation span and soil thickness (load) affect the bending moment and deflection of pipe roof greatly, and the influence of span is greater. (4) The foundation bed coefficient and pipe thickness affect the bending moment of pipe roof little, while they can reduce the deflection to a certain extent.