内支撑体系下装配式车站基坑支护受力研究

Stress of Prefabricated Subway Station Foundation Pit Support under Internal Support System

以深圳地铁装配式车站中医院站为工程背景,结合车站所处的工程地质条件以及装配式车站的施工工序,采用ABAQUS有限元分析软件,建立地层-结构模型,重点分析装配式车站施工过程中基坑的变形规律、支撑轴力变化规律及倒换接续支撑的受力特点。首先,分析装配式车站基坑变形,主要分为开挖阶段和车站拼装阶段,地连墙总变形为10.31 mm,其开挖阶段占比较大,占总变形的88.6%,开挖过程中基坑变形趋势与现浇车站一致;其次,在支撑倒换及结构拼装过程中,地连墙变形占总变形的11.4%,变化范围为0.05~0.99 mm,其变形的量值及变形的范围同现浇车站均存在较大的差异;再次,分析拆撑、换撑的工序及受力特点,拆撑及换撑是装配式车站施工的重要施工步序,在靠近拆撑环的中板临时支撑轴力较大,占整个换撑轴力的80%,因此在布置接续撑时,靠近换撑的1环接续撑数量可适当增加,远离换撑1环接续撑可减少支撑数量;最后,对比数值计算和现场监测结果,两者的变化规律基本一致,验证数值分析的有效性。

Using the Shenzhen Traditional Chinese Medicine Hospital prefabricated subway station as the engineering background,a ground structure model was established using ABAQUS finite element analysis software combined with the engineering geological conditions and the construction process of the prefabricated station structure.The deformation law of the foundation pit,the change law of the axial force of the support,and the stress characteristics of the inverted continuous support during the construction of the prefabricated station were analyzed.The deformations of the foundation pit of the prefabricated station divided into excavation and station assembly stages were analyzed.The deformation of the diaphragm wall was 10.31 mm and accounted for 88.6%of the deformation in the excavation stage.The deformation trend of the foundation pit during the excavation process was consistent with that of a cast-in-place station.In the process of support switching and structural assembly,the deformation of the diaphragm wall accounted for 11.4%of the deformation with a variation range of 0.05–0.99 mm.The magnitude and range of deformation of the prefabricated structures were quite different from those of the cast-in-place structures,and the process and stress characteristics of support removal and replacement were analyzed.Support removal and replacement are important steps in the construction of prefabricated structures.The temporary axial force on the middle plate near the support removal ring accounted for 80%of the axial force of the entire support replacement.Therefore,the number of single rings of continuous support close to the support replacement can be appropriately increased when arranging the continuous support,and the number of single rings of continuous support far from the support replacement can be reduced.The results of the numerical calculation and field monitoring were compared,and the change laws of the two were basically consistent and verify the effectiveness of the numerical analysis.