Study on Techniques for Crossing Under Main Lines of Long-Span and Flat Tunnels by the Superly Long Pipe-Shed Method
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摘要: 浅埋隧道下穿重要基础设施时地下结构的稳定性及周边环境变形控制是工程的重点和难点,管棚法是一项提高岩土稳定的重要技术措施。结合福建某大跨扁平超浅埋隧道采用超长管棚法下穿铁路干线的工程实践,分析棚架体系工作原理,总结出超浅埋暗挖隧道超长管棚的施工方法及技术要点。基于Winkler弹性地基梁理论,考虑三步掘进预留核心土施工过程,分析地表沉降规律及隧道支护结构内力分布特性,优化现场支护参数及支护措施设置,结合实测结果验证了计算结果及支护措施的合理性,并结合施工过程及环境特点对地表变形原理进行详细探讨。最后基于实测地表沉降,对超长管棚施做引起的沉降特点及影响因素进行系统分析,结合实际工程特点提出轨道变形控制措施,并从管棚施工技术要点提出地表沉降控制方法。Abstract: The stability of underground structures and the deformation control of surrounding environments are key and difficult subjects in shallow tunnels crossing below important infrastructures,and the pipe-shed method is an important technical measure, which can improve the stability for the environment of rock and soil. Combined with an engineering practice of a long-span, flat and superly shallow tunnel in Fujian Province, which was used the superly long pipe-shed method to cross below main lines, the working principles of the pipe-shed system were analyzed, and the construction methods and crucially technical points of superly long pipe-sheds in ultra shallow tunnels were summarized and put forward. Based on the Winkler elastic foundation beam theory,considering the construction process of three-step tunnelling to reserve core soil,the laws for subsidence of the earth’s surface and the internal force distribution characteristics of the tunnel support structure were analyzed to guide the setting of support parameters and support measures on site. Based on the measured results, the rationality of the calculation results and support measures were vindicated. Combined with the construction process and environmental characteristics, the principle of the subsidence was discussed in detail. Finally,based on the measured subsidence,the subsidence characteristics and influencing factors caused by superly long pipe-shed construction were analyzed systematically. According to the actual engineering characteristics,the control measures of rail deformation were proposed,and the subsidence control methods were proposed from key points of construction techniques.
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