大跨度薄壁槽形梁支架现浇质量控制技术研究

Research on the Quality Control Technoloy in Support Cast-in-place of Large Span Thin-walled Channel Beam

研究目的:沪昆客专西北上行和南西联络线特大桥主桥紧邻运营高铁,结构为(32+80+112)m非对称槽形梁独塔双索面斜拉桥,总体采用"整体支架预制梁体、水平转体跨越武广高铁"的方案;按照总体施组安排,主梁采用国内高铁建设首次应用的薄壁槽形结构,针对主梁腹板薄、大开口、浇筑方量大等特点,在一次整体支架现浇施工中混凝土浇筑方法不当、养护不合理等因素导致梁体产生裂纹等问题。为确保大跨度薄壁槽形梁的现浇施工质量,本文从现浇支架体系安全、早期温度场防护开裂、现浇施工工艺等方面研究槽形梁支架现浇质量控制技术。研究结论:(1)本桥大跨度薄壁槽形梁采用一次整体现浇的方法是不可行的,通过仿真计算分析,提出了"分三段现浇+两道后浇带"的纵向浇筑方案;(2)横向浇筑方法是薄壁槽形梁局部质量控制的重要环节,为此提出了"先浇筑槽形梁底板、再浇筑箱形边主梁"的横截面浇筑方案;(3)针对紧邻运营高铁支架结构体系的高度高、跨度大、梁体坡度大等施工难点,通过对高支架结构的稳定性分析,提出了"整体连接、贝雷梁搭接固定、设置刚性墩"的构造措施;(4)提出的槽形梁支架现浇质量控制技术适用于紧邻运营高铁的大跨度混凝土槽形梁及类似梁型的现浇施工。

Research purposes： The main bridge of the northwestern and southwestern connecting line of the Shanghai-Kunming passenger dedicated line is a（ 32 ＋ 80 ＋ 112） m asymmetric slot girder single tower double cable plane cable-stayed bridge,which adopts the overall scheme of ＂ entirely prefabricated box structure,horizontal rotating across the Wuhan-Guangzhou high-speed railway＂. According to general construction organization,the main girder adopts thin-walled groove section which is first used in the field of high speed railway construction,according to characteristics of thin web,large opening and large quantity of concrete pouring,in one time integral casting of the concrete beam,factors of improper pouring method and improper maintenance lead to problems such as cracks. In order to ensure the construction quality of large span thin-walled channel beam,quality control technoloy in support cast-in-place is studied from cast-in-place support system design,early hydration heat,cast-in-place construction technology and other aspects.Research conclusions：（ 1） The scheme of one time integral casting of large span thin-walled channel beam is infeasible,longitudinal pouring sequence of ＂three pouring segments and post pouring belt ＂ is put forward by simulation;（ 2） The method of transverse pouring is the important link of local quality control,and the method of ＂first pouring base plate and then second pouring side box beam＂is put forward;（ 3） According to the bracket structurewhich is next to high-speed railways has construction difficulties of high height,large span and large slope,construction measures of＂integrated connection,fastening lap joint of bailey beam and setting rigid pier＂are put forward by stability analysis;（ 4） The quality control technology of cast-in-place beam supports is suitable for cast-in-situ construction of large-span concrete trough girders and similar beam types,which are next to high-speed railways.