洞桩法车站扣拱方案优化

Optimization of PBA Method Station Arch Support Scheme

[目的]在洞桩法施工中,不同扣拱方案的选择对结构力学特性具有重要的影响。为确保城市地下结构的可靠性和安全性,必须严格监测地面沉降,因此有必要系统地研究各类扣拱方案对支护结构及地面变形的影响规律。[方法]以广州地铁11号线天河东站工程为例,采用MIDAS/GTS软件构建三维有限元模型,深入分析不同扣拱方案下的地面沉降特征及拱部初期支护的内力分布规律。同时,结合现场地面沉降监测数据对数值模拟结果进行验证。[结果及结论]根据初支扣拱的计算结果可知,相较于CD(中隔墙)法,台阶法的地面沉降、拱部初支弯矩和轴力分别增加了6.80%、9.74%和14.62%,但均满足施工控制要求。根据二衬扣拱的研究结果可知,相较于顺序拆撑法,交替拆撑法能够显著减小地面沉降,且对拱部初支内力的影响较小。CD法初支扣拱配合交替拆撑二衬扣拱的方案具有优越性。

[Objective]In PBA(pile-beam-arch)method construction,the choice of different arch support schemes significantly impacts the structural mechanics.To ensure the reliability and safety of urban underground structures,it is essential to rigorously monitor the land subsidence.Thus,it is necessary to systematically study the impact law of various arch support schemes on supporting structures and ground deformation.[Method]Based on Tianhe East Station project on Guangzhou Metro Line 11 and using MIDAS/GTS software,a three-dimensional finite element model is constructed to analyze the land subsidence characteristics and the arch initial support internal force distribution law of various arch support schemes in depth.Meanwhile,field monitoring data of land subsidence is also used to validate the numerical simulation results.[Result&Conclusion]The calculation results of initial support arches reveal that,compared to the CD(center diaphragm)method,the stepped method results in increases of 6.80%in land subsidence,9.74%in initial support bending moment,and 14.62%in axial force,all meeting the construction control requirements.Research results of secondary lining arch support show that the alternating support removal method significantly reduces land subsidence with a smaller impact on arch initial support internal forces compared to the sequential support removal method.The scheme of combining CD method for initial arch support with alternating support removal method for secondary lining arch support proves to be advantageous.