北京地铁朝阳站配套交通枢纽内部主体结构使用功能的差异,使得枢纽基坑呈现平面几何形状复杂、基坑开挖深度不同及基坑周边附加荷载不对称等特点。为解决常规基坑支护方案存在的问题,基于分级开挖和分级支护的理念研发了多级深基坑支护结构体系。论文详细讨论了各级支护结构的布置、结构参数局及施工步序。采用数值模拟和现场监测的方法,研究了多级深基坑开挖过程中支护结构体系的受力和变形特征。结果表明:基于分级开挖和多级支护的理念,研发的多级组合支护结构体系,具有布置形式灵活,控制变形能力强的特点;支护结构体系受各级基坑开挖的附加扰动影响,受力复杂,呈“悬臂+弓形”变形;紧邻高铁站侧围护结构水平变形远大于远离侧,但当各级基坑间距超过3倍开挖深度时,可忽略上一级结构变形产生的附加影响;数值模拟及现场监测结果表明多级组合支护结构变形及受力能满足控制值要求,可为类似工程提供参考。
The difference in the use function of the main structure inside the supporting transport hub of Chaoyang Station of Beijing metro makes the hub pit present the characteristics of "complex planar geometry, different depth of pit excavation and asymmetry of additional loads around the pit". In order to solve the problems of the conventional pit support structure, a multi-level deep pit support structure system was developed based on the concept of graded excavation and multi-level support. The paper discusses in detail the arrangement, structural parameters and construction sequence of each level of support structure. Numerical simulation and on-site monitoring methods are used to study the force and deformation characteristics of the multi-stage deep foundation pit support structure system during the excavation process. The research results show that: based on the concept of graded excavation and multi-level support, the developed multi-level combined support structure system has the characteristics of flexible arrangement form and strong deformation control ability. The support structure system is affected by the additional disturbances from the excavation of all levels of foundation pits, showing "cantilever + bow" deformation. The horizontal deformation of the enclosure structure on the side immediately adjacent to the high-speed railway station is much larger than that on the side far away from it, but when the spacing between the various levels of foundation pits exceeds three times the excavation depth, the additional influence of the deformation of the previous level of structure can be ignored. The numerical simulation and on-site monitoring results show that the deformation and force of the multilevel combined support structure can meet the requirements of the control value, and it can provide a better reference for the similar projects.
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