关键词: 地铁车站, 三圆盾构, 结构设计, 顶推力计算, 局部背土, 预应力组合梁

Abstract: The construction of metro stations in complex environments in busy urban areas is a challenging task. The open-cut method necessitates frequent pipeline relocation and substantial breaking works, while traditional mining methods require dewatering, which can induce construction settlement and adversely affect the surrounding environment. Herein, a case study is conducted on the Peking University station on the Shenzhen metro line 7. Scheme comparison, theoretical derivation, and model testing methods are employed to examine the construction technology of the metro stations using triple-circular shield from the perspectives of design and construction. The evaluation comprehensively considers architectural functionality, construction convenience, and construction cost. Optimized design schemes for the cross-section of the triple-circular shield, as well as for segment division and assembly, are proposed. A theoretical calculation formula for the jacking force of triple-circular shield metro stations is derived, yielding a theoretical jacking force of 61 534.18 kN based on the actual conditions of the Peking University station. Furthermore, the influence of soil physico-mechanical parameters—shield length, tunnel width, and friction coefficient—on the local soil load-carrying effect at the gull-wing block position is examined, leading to the derivation of a discriminant formula for the local soil load-carrying effect. The calculations indicate that there is no local load-carrying soil when the friction coefficient between the segment and soil is below 0.39. Based on these results, technical measures are proposed to reduce the soil load-carrying effect. Finally, a novel prestressed segment steel-reinforced concrete composite beam is designed. Model tests demonstrate that, compared to scenarios devoid of prestressed tendons, the inclusion of prestressed tendons with differing tensile forces increases the yield load by 28.2% and 19.3%, respectively, when subjected to positive bending moments and the ultimate load by 12.1% and 11.7%, respectively. Under negative bending moments, the yield load increases by 47.4% and 54.0%, respectively, and the ultimate load increases by 45.1% and 69.3%, respectively.

Key words: metro station, triple-circular shield, structural design, jacking force calculation, local load-carrying soil, prestressed composite beam