目前,大跨、超大跨地铁隧道修建呈现递增趋势。大跨、超大跨隧道常设计临时支撑以减小跨度,但由于临时支撑与二次衬砌在空间上的相互干涉,需在二衬施做前拆除临时支撑。拆撑会打破结构原有受力平衡,是结构受力的薄弱环节,施工不当极易造成隧道塌方等安全事故。鉴于国内外关于采用双层初支拱盖法修建的超大跨隧道拆撑的结构力学响应及安全性仍缺乏系统的研究,以广州地铁11号线华华区段四线并行折返线区间隧道为依托工程,通过理论分析与数值计算相结合的方式,从横向和纵向两方面对隧道拆撑时结构的力学响应以及安全性进行分析,最终确定了科学、合理、安全、高效、快速的拆撑施工方案,并顺利通过了现场施工的检验。结果表明:城市软弱地层超大跨隧道采用“横向先边后中、对称拆除,纵向先隔三拆一、后隔一拆一”的拆撑方案是切实可行的,可为后续工程提供借鉴与指导。
At present, the construction of large-span and super-large-span subway tunnels is increasing. Temporary support is often designed to reduce the span in the construction of those tunnels. However, temporary support needs to be removed before secondary lining is constructed due to the spatial overlap between them. The removal of temporary support is the weak situation, because the original stress balance of the structure will be broken. Improper construction can easily cause safety accidents such as tunnel collapse. In view of the lack of systematic research on the structural mechanical response and safety of the super-large-span tunnel constructed by the double-layer initial support arch-cover method at home and abroad, this paper takes the four-line parallel tunnel of Huahua section of Guangzhou Metro Line 11 as the basis project. Through the combination of theoretical analysis and numerical calculation, the mechanical response and safety of the structure during the dismantling of the tunnel are analyzed from both horizontal and vertical aspects. Finally, a scientific, reasonable, safe, efficient and rapid dismantling scheme was determined, and successfully passed the inspection of on-site construction. The results show that it is feasible to dismantle the super-large-span tunnel in urban soft stratum by using the scheme of ‘first edge and then middle, and symmetrical demolition in cross direction, first three demolition and one demolition, and then one demolition and one demolition in longitudinal direction’, which can provide reference and guidance for subsequent projects.
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