大理至保山铁路澜沧江大桥施工测量技术

大理至保山铁路澜沧江大桥为主跨342m的上承式劲性骨架钢筋混凝土提篮拱桥。大桥两岸河谷呈"V"形,大理岸桥台坡角约60°,保山岸桥台坡角约80°,局部近于直立。考虑山体自然状况,钢管拱施工采用二次竖转技术。为保证钢管拱准确合龙,采用高精度大桥专用控制网并精密联测二等水准网;建立拱座开挖独立坐标系,控制超欠挖,减少混凝土消耗;建立拱肋二次竖转数学计算模型,解决钢管拱预拼,拱肋支撑体系,拱肋竖拼,中间铰安装定位,拱肋转体、合龙等空间测量与调整问题。成桥后钢管拱轴线偏位<15mm,高程<15mm,满足规范要求。

Measuring Techniques Used in Construction of Lancangjiang River Bridge on Dali-Baoshan Railway

The Lancangjiang River Bridge on Dali-Baoshan Railway is a deck-type basket-handle arch bridge with a main span of 342 m,featuring its stiff-skeleton reinforced concrete arch.The bridge crosses a V-shaped ravine,resulting in a 60°sloppy angle between the Dali-side abutment and the river bank and an 80°sloppy angle between the Baoshan-side abutment and the river bank,with roughly vertical angles locally.Given the natural condition of the mountains,the steel tubular arch was constructed by two-time vertical rotation technique.To ensure the accurate closure of the steel tubular arch,a bespoke high-precision control network was established and used in combination with the precise second-grade leveling for comparison survey.Independent coordinates were set for the excavation of arch seat pits aiming to control overbreak and reduce the consumption of concrete.A model for mathematical calculation of the two-time rotations of the arch ring was built to address the issues related to spatial measuring and adjustment,including the assembly of the steel tubular arch,supporting system of arch ring,vertical assembly of arch ring,installation and positioning of central hinge as well as the rotation and closure of arch ring.In the completed bridge stage,the deviations of axial alignment and elevation of the steel tubular arch are all less than 15 mm,meeting the code requirements.