肥槽回填对装配式地下车站结构的力学影响

Mechanical Influences of Foundation Trench Backfillingon Prefabricated Underground Station Structure

肥槽回填是明挖装配式地下车站的主要施工阶段,对装配式地下结构的内力和变形有重要影响。针对肥槽回填阶段装配式地下车站结构的力学特性,建立增量法结构计算模型,对不同肥槽的回填材料、回填方案以及中板结构施作的先后次序等工况下的装配式地下车站的结构进行分析,研究不同工况对装配式地下车站结构内力和稳定性的影响。研究结果表明:①采用常规土体材料进行肥槽回填,其回填荷载会导致该阶段装配式结构部分的接头内力超过接头承载能力,回填荷载作用下结构有失稳趋势(拱脚支撑受拉);②采用结硬性材料进行肥槽回填,不同分层方式的回填方案对装配式结构的接头内力和稳定性影响差异较大,其中结硬性回填材料一次性回填对结构的影响比常规土体回填更大,分多层回填时能有效降低回填荷载的影响,采用4次分层回填方案,结构受力与变形均有大幅改善,能确保结构稳定性,使接头承载性能满足要求;③在肥槽回填之前施工中板结构,能大幅改善肥槽回填荷载对结构接头承载能力和稳定性的影响,各种回填方案均能满足结构受力和稳定性的要求,因此中板施工前置工况可降低对肥槽回填材料和方案的要求,不排除今后采用较低强度结硬性材料回填的可能性。

Backfilling a foundation trench is the main stage in the construction of an open-excavation prefabricated underground station structure and has a significant influence on the internal force and deformation of the structure.In this study,an incremental method calculation model was established based on the mechanical characteristics of a prefabricated underground station structure during the backfilling stage.The structure under the working conditions of backfill materials,backfill schemes,and orders of construction of the middle-floor structure were analyzed.The effects of different working conditions on the internal structural force and structural stability of the structure were studied.The following results were found.First,using conventional soil material for the backfill of the foundation trench,the backfilling load(arch foot support tension)caused the internal forces of some joints of the prefabricated structure to exceed their bearing capacity,and the structure became unstable.Second,when hardening material was used for backfill and different layered backfill schemes exerted greatly different impacts on the prefabricated structure joint internal force,the structural stability.Among the schemes investigated,the one-time hardening backfill material scheme resulted in a greater structural stability than that of a conventional soil backfill.Multilayer backfilling can effectively reduce the impact of the backfill load,and the use of a four-layered backfill scheme could minimize the stress and deformation of the structure and thus ensured the stability of the structure,and the bearing performance of the joint met the requirements.Third,when the floor structure was constructed before backfilling,the influence of the backfilling load on the bearing capacity of the structural joint and the structural stability were greatly improved.All types of backfilling schemes met the requirements of structural force and stability,suggesting that the pre-construction conditions of the floor have lower requirements for backfilling materials and schemes.The possibility of backfilling with a low-strength bonded material cannot be ruled out.