肥槽回填是明挖装配式地下车站建造过程中的常见施工阶段,若按传统方式展开结构计算,此阶段计算易被忽视,考虑到装配式地下结构的内力和变形随施工过程的动态变化,有必要阐明肥槽回填在明挖装配式地下结构计算中的重要作用。本文首先对肥槽回填阶段混凝土液态转向固态对结构产生的影响展开机理分析；提出了能实现肥槽回填效应的结构计算模型；并采用增量法,通过对比分析肥槽有无回填荷载条件下装配式地下结构的力学变化差异,阐明肥槽回填在装配式地下车站结构计算中的影响；在此基础上,从肥槽分层回填次数、施做工序调整、结构形式调整等角度对装配式地下车站结构展开优化分析。针对预制装配式地下车站结构,结果表明：①肥槽回填主要影响侧墙的结构设计；②分层回填次数主要影响肥槽回填阶段装配式地下结构的稳定性,分层次数越少,拱形装配式地下结构的拱顶抬升和拱脚内缩越严重；③合理施做工序调整(如中板安装调整至肥槽回填之前),对抑制结构拱顶抬升和拱脚内缩有明显改善,但工序调整会引起侧墙区域的内力增加,对结构内力和变形的影响趋势相反；④拱形装配式地下车站结构调整为矩形结构,将明显降低结构肥槽回填阶段的失稳风险,同时降低结构的内力,对结构内力和变形影响趋同。

The backfilling of foundation trench is a common construction stage in the construction of open excavation prefabricated underground station. If the structure calculation is carried out in the traditional way, the calculation details at this stage are easy to be ignored. Considering the dynamic change of internal force and deformation of prefabricated underground structure with the construction process, it is necessary to clarify the important role of backfilling of foundation trench in the calculation of open-excavation prefabricated underground structure. In this paper, firstly, the mechanism of the influence of concrete liquid state to solid state on structure during the backfilling stage of foundation trench is analyzed. A structural calculation model based on the inheritance effect of liquid backfill load is proposed. The increment method is used to analyze the mechanical change law of prefabricated underground structure with or without inheritance effect. On this basis, the structure optimization analysis of the prefabricated underground station is carried out from the perspectives of the number of backfilling times of foundation trench, the adjustment of operation procedure and the adjustment of structure form. For the prefabricated underground station structure, the results show that: (1) the liquid inheritance effect of foundation trench backfilling mainly affects the structural design of the side wall; (2) The number of layered backfilling mainly affects the stability of prefabricated underground structure in the backfilling stage of foundation trench. The less the number of layered backfilling, the more serious the vault uplift and arch foot retraction of arch prefabricated underground structure. (3) Reasonable application of process adjustment (such as the middle plate installation before the backfilling of the trough) can significantly improve the inhibition of the uplift of the arch and the shrinkage of the arch foot, but the process adjustment can cause the increase of the internal force of the side wall area, and the influence of the internal force and deformation of the structure is opposite. (4) When the structure of arch prefabricated underground station is adjusted to a rectangular structure, the risk of instability in the backfilling stage of the structure foundation trench will be significantly reduced, and the internal force of the structure will be reduced, and the influence on the internal force and deformation of the structure will converge.

北京城建集团创新项目(新型预制装配式地下车站结构模型试验研究)；国家重点研发计划(2017YFB1201104)