济阳黄河公铁两用特大桥施工关键技术

Key Construction Techniques of Jiyang Huanghe River Rail-cum-Road Bridge

济阳黄河公铁两用特大桥主桥为(84+144+228+240+300+120+60)m非对称、多跨、不等高、矮塔钢桁梁斜拉桥,采用塔梁固结、塔墩分离的结构体系。主梁采用N形双主桁、双层桥面布置,上层通行6车道公路,下层通行双线铁路。主墩桩基利用黄河枯水期采用大型旋挖钻机成孔,位于黄河主河槽的主墩承台采用锁口钢管桩围堰成套施工技术,其余主墩采用钢板桩围堰施工。主墩承台大体积混凝土结构采用自动测温及内部循环冷却水控制的智能化温度控制系统,承台混凝土未出现有害裂纹。钢桁梁利用门吊吊装杆件,设置墩旁托架和临时墩,采用双悬臂拼装+单侧悬臂拼装方式架设,结合钢塔两侧跨度不对称及跨黄河险工河段、施工条件受限等特点,通过定点精确配重+移动配重+索力调整,确保了钢桁梁线形满足设计要求、架设过程安全稳定。钢塔利用组合起重设备和定位工装分节组拼,钢横梁利用塔顶吊架整体提升,保证了钢塔安装精度。

The main bridge of Jiyang Huanghe River Rail-cum-Road Bridge is an extradosed bridge with seven spans(84+144+228+240+300+120+60)m,accommodating two levels of decks,where the upper deck carries six vehicle lanes and the lower deck bears double rail tracks.The superstructure consisting of N-shaped trusses is fixed with the four pylons,but supported on bearings atop pylon piers.The pile foundations of the pylon piers were constructed using rotary drilling rigs during the dry season,the pile caps that are situated at the main channel of Huanghe River were constructed with the aid of interlocking steel pipe pile cofferdams,and the remaining piers were constructed using steel sheet pile cofferdams.A smart temperature control system was installed in the mass concrete of pile caps of pylon piers for automatic temperature measurement and cooling water cycling control,and no hazardous cracks were observed in the pile cap concrete.The members of the steel trusses were hoisted using gantry cranes and installed into position by the combined two-way cantilever assembly and one-way cantilever assembly,with the assistance of pier-side brackets and temporary piers,The asymmetric span arrangement and the adverse river conditions imposed great challenges on the construction.Targeted counterweighting,mobile counterweighting and stay cable tension tuning were conducted to ensure that the alignment of the steel trusses would meet the design requirements,as well as a smooth and safe construction.The steel pylon segments were assembled in sequence,and the pylon crossbeams were integrally hoisted using the lifting cranes atop of the pylons,to ensure the installation precision of the steel pylons.