大直径盾构隧道轨下结构设计方案比选研究

京张高铁清华园隧道为国内首次采用全预制轨下结构的盾构隧道。以该工程为背景,为得出适合大直径盾构隧道的轨下结构方案,选择轨下结构全现浇、中箱涵预制两侧现浇、全预制3个方案,通过论述分析和建立有限元模型计算,从工期、施工工序、对隧道结构的影响、结构受力和变形特征、施工环境和环保要求、工程造价等方面对方案优缺点进行分析、比选。研究结论:轨下结构全预制方案在工期、施工工效、施工质量、施工环境等方面具有明显优势;全预制轨下结构在受力和变形上能够满足高速铁路的运营要求;施工实践表明,全预制轨下结构有效解决了本工程工期短、距离长、要求高的工程难点问题。

Comparative Study on Design Schemes of Prefabricated Sub-rail Structure for Large Diameter Shield Tunnel

The Tsinghuayuan Tunnel of Beijing-Zhangjiakou High-speed Railway is the first shield tunnel in China with full prefabricated sub-rail structure. In order to choose the sub-rail structure suitable for large-diameter shield tunnel, three design schemes of full cast-in-place sub-rail structure, prefabricated middle box structure with cast-in-place board structures on both sides, and full prefabricated sub-rail structure are proposed based on the project. Through analysis and finite element model calculation, the advantages and disadvantages of the schemes are compared from the aspects of construction period, construction process, influence on tunnel structure, structural stress and deformation characteristics, construction environment and environmental protection requirements, and engineering cost. The research results show that the full prefabricated sub-rail structure has obvious advantages in construction period, construction efficiency, construction quality, construction environment, and it meets the operational requirements of High-speed Railway in terms of stress and deformation. Construction practices demonstrate that the prefabricated sub-rail structure can effectively solves the engineering difficulties of short construction period, long distance and high requirements.