斜拉桥粉沙软土地基现浇箱梁支架基础施工技术

神舟友谊大桥主跨为现浇混凝土箱梁,采用落地现浇支架施工,由于支架基础存在4~6 m的粉沙地基,地基承载能力低,变形大。采用钢管混凝土扩大基础施工工艺,提高地基承载力。支架上部承重按等跨连续钢梁布置。钢管桩顶横向设双拼I40b工字钢横梁,横梁与桩顶钢板焊接,横梁上布设纵梁,横梁与纵梁在接触点采用焊接,纵梁上承碗口式满堂支架,支架上托横线安装方木横梁,上铺大钢模板,作为箱梁底模。以确保箱梁施工的质量和支架结构的安全,可为类似软土地基上现浇箱梁的支架施工提供参考。

Construction Technology of Cast-in-place Box Girder Support Foundation in Silt Sand Soft Soil Subgrade of Cable-stayed Bridge

The main span of Shenzhou Friendship Bridge is a cast-in-place concrete box girder,and is constructed by floor cast-in-place support.Because of the support foundation in the 4-6m silt subgrade,the bearing capacity of subgrade is low and the deformation is large.The construction technology of concrete filled steel tube(CFST)to expand the foundation is used to improve the bearing capacity of subgrade.The upper load-bearing capacity of the support is arranged according to the equal-span continuous steel girders.The top of the steel pipe pile is arranged with double-shaped I40b I-steel crossbeam.The crossbeam is welded with the steel plate of pile top.The longitudinal beam is arranged on the crossbeam.The crossbeam and the longitudinal beam are welded at the contact point.The longitudinal beam is supported by the bowl-shaped full-frame bracket.The square wood crossbeam with horizontal line is installed on the bracket.The large steel formwork is laid on it as the bottom board of box beam in order to ensure the quality of the box beam construction and the safety of the bracket structure,which provides a reference for the bracket construction of the cast-in-place box beam on the similar soft soil foundations.