孟加拉国帕德玛大桥施工关键技术

Key Construction Techniques of Padma Bridge in Bangladesh

孟加拉国帕德玛大桥为双层桥面公铁两用桥,主桥为连续钢桁组合梁桥,桥跨布置为6×(6×150)m+1×(5×150)m。单个桥墩基础采用6根∅3.0 m、倾斜度为1∶6的大直径钢管斜桩;上部结构为全焊接连续钢桁梁-胶拼桥面板组合梁结构。钢管斜桩采用岸上分段制造,浮运至墩位处采用水上定位平台+多层导向架分2节插打的方案施工;上部结构钢桁梁采用整孔制造、整孔架设、逐孔合龙的方案施工。施工过程中下部结构采用水上定位平台及多层导向架施工技术,确保了钢管斜桩的快速插打和施工精度;通过桩内取土置换以及桩侧、桩底压浆技术,提升了桩基承载力,有效解决了桥址地质条件差等问题。大跨度连续钢桁梁采用工厂全焊接整孔制造、现场整孔架设技术,保证了钢梁制造质量和架设工期;桥面板施工采用岸上预制、现场安装的方法,减少了桥上现浇作业量及高空作业风险,保证了施工质量。

The Padma Bridge in Bangladesh is a rail-cum-road bridge accommodating two levels of decks.The main bridge is a steel truss bridge containing six continuous units of 6×150 m and one continuous unit of 5×150.Each pier is supported by six raked steel pipe piles of 3.0 m in diameter,and all the piles incline a degree of 1∶6.The superstructure consists of fully-welded steel trusses that are glued and act compositely with the overlaid concrete slabs.The steel pipe piles were manufactured off site in sections and shipped to pier sites.With the assistance of the positioning platform over water and multi-layer guiding frame,an individual steel pipe pile,which was assembled from sections into two long lifts to ease the construction,was driven into position,lift by lift.The steel truss in each span was monolithically manufactured and also erected as an entirety at bridge site,followed by span-by-span closure.To address the poor geological conditions at the bridge site,a series of techniques were employed to improve the load-bearing capacity of the pile foundation,including soil displacement in piles and pile-side and pile-tip grouting.By employing the monolithic manufacturing,full-welding,span-by-span erection techniques,the manufacturing quality of the steel girder and erection schedule were guaranteed.The concrete slabs were precast on land,and shipped to the bridge site for erection,which greatly reduced the cast-in-situ work on bridge and overhead working risk and ensured the construction quality.