大跨径钢管混凝土拱桥管内混凝土顶升灌注工艺试验

Test on Technology of Jacking and Pouring Concrete in Pipe of Long-span CFST Arch Bridge

主拱管内混凝土顶升灌注是钢管混凝土拱桥建设的关键工序和技术难点,大跨钢管混凝土拱桥的管内混凝土方量大、强度高、泵送距离远、灌注时间长,容易出现堵管、爆管现象,国内已有多座桥梁发生该类事故。为降低主拱管内混凝土灌注施工风险,开展了大跨径钢管混凝土拱桥管内混凝土顶升灌注工艺试验研究,探讨了管内混凝土顶升灌注施工过程对混凝土坍落度、扩展度、塑性黏度、运动模式和泵送压力的影响规律。结果表明:管内混凝土经历高压泵送过程后,其坍落度、扩展度和塑性黏度有所降低,对抗压强度影响不明显;在高泵压条件下,混凝土含气量增加,在泵送过程结束时,混凝土含气量降低;混凝土在大直径主拱钢管和小直径泵管内的运动模式存在明显差异,前者运动速度极慢,以管内混凝土自身剪切运动为主,后者运动速度较快,以活塞式整体推移运动为主;管内混凝土运动模式差异导致泵送压力计算方法不同,大直径主拱钢管内混凝土泵送压力以克服重力做功为主,小直径泵管内混凝土的泵送压力以克服管壁摩阻力和自身剪切力为主。通过试验提出了小直径泵管和大直径主拱钢管的管内混凝土泵送压力计算方法,并通过工程实例验证了此方法的适用性。

The jacking and pouring of concrete in the main arch pipe is a key process and technical difficulty in the construction of CFST arch bridge.The concrete in the pipe of long-span CFST arch bridge has large volume,high strength,long pumping distance and long pouring time,it is prone to block and burst.Several accidents have occurred on many bridges in China.In order to reduce the construction risk of concrete pouring in the main arch pipe,the experimental research on the technology of concrete jacking and pouring in the pipe of long-span CFST arch bridge is carried out,and the influence rules of the construction process of concrete jacking and pouring in the pipe on the slump,expansion,plastic viscosity,movement mode and pumping resistance of concrete are discussed.The result shows that(1)The slump,expansion and plastic viscosity of the concrete in the pipe are reduced after the high-pressure pumping process,and the influence on the compressive strength is not obvious.(2)Under the condition of high pump pressure,the air content of concrete increases,while it decreases at the end of pumping process.(3)The movement modes of concrete in large-diameter main arch steel pipe and small-diameter pump pipe are obviously different.The former moves very slowly,mainly with the shear movement of the concrete in the pipe itself,while the latter moves faster,mainly with the piston type overall push movement.(4)The different movement modes of concrete in the pipe leads to different calculation methods of pumping pressure.The pumping resistance of concrete in the large-diameter main arch steel pipe is mainly to overcome gravity and do work,while the pumping pressure of concrete in the small-diameter pump pipe is mainly to overcome the pipe wall friction resistance and its own shear force.The calculation methods of concrete pumping pressure in the pipe of small-diameter pump pipe and large-diameter main arch steel pipe are put forward through the test,and the applicability is verified by project examples.