青藏铁路三岔河特大桥空心薄壁高墩寒季混凝土施工技术

三岔河特大桥地处海拔高、干燥多风的恶劣气候区,是青藏铁路的咽喉工程,按总体部署须跨越寒季施工,依据高墩薄臂特点,优选拆装式大模板施工方法。该项技术采用试验研究、理论计算分析、现场监测分析等手段,使现场量测与设计数据、施工管理等工程信息相结合,并反馈于施工过程中。利用成熟度法对砼早期强度进行预测和估算,以确定下道工序的时间和对混凝土质量进行预测;采用双层保温层及内置供热系统形成高原高寒高墩薄臂负温混凝土保温加热养护技术;选用塔吊配合整体拼装式模板的高墩施工技术,成功解决空心薄臂高墩快速连续施工和寒季砼加热养护的难题,实现了高墩流水化、机械化作业。以温度为主线的信息化监控技术是该技术成果的创新内容,该创新成果对于高寒地区,尤其对青藏铁路、青藏公路桥梁下部结构施工具有广泛应用和借鉴价值。

Construction Technology of Hollow Thin-shell High Piers of Extra-large Bridge on Sancha River in Qinghai-Tibet Railway Project in Frozen Season

Sancha River Extra-large Bridge of Qinghai-Tibet Railway Project locates in adverse climate area with high altitude, dry and windy all year round. It is one of the most critical projects. Acoording to general schedule, the construction has to be done through frozen winter. Since the piers were high with thin shells, after the advantages and disadvantages of tip-form, slip-form and monolithic-form hoisting techniques were carefully analyzed, assembled large panel formworkd were selected for coonstruction. Experimental study, theoretical calculation and analysis, field monitoring analysis etc were adopted to combine data from the on-site survey and monitoring with design data and constructional management, and then fed back to the construction. Maturity method was adopted for concrete to estimate and forecast early strength of concrete to determine contruction time of the following procedure and to forecast the concrete quality. Double thermal insulators and internal heating system were adopted to form a curing system suitable for high shell pier conerete on plateau in frozen region. Tower hoisters and monolithic piece-up formwork were used for construction af high piers. Fast and continuousconstruction problems of hollow high piers and concrete curing by heating and thermal insulation in extremely frozen climate were successfully solved. Streamline construction was achieved, and mechanization was improved. Comprehensive minitoring technique with temperamre monitoring as the core technology is an innovation, which would be widely applied and referred by construction in extremely frozen region, especially for construction of bridge substructures of Qinghai-Tibet railways and Qinghai-Tibet highway.