铁道建筑

在山区峡谷非通航河流中施工埋入裸岩河床较深的低桩承台时，采用浮式平台先进行河床开挖、再搭设固定平台施工钻孔桩与拼装围堰的常规做法存在浮式平台对于周期性变化水位适应差、两类不同施工平台投入大、工序转换间隔时间长等问题。依托石门铁路澧水特大桥13#墩深水基础工程，在采用有限元数值分析法证明泥质砂岩河床水下垂直边坡能够保持稳定的基础上，设计出一种集开挖河床、钻孔桩施工、散拼围堰吊装等三重功能于一体的固定式水上施工平台。该平台以采用“板凳钢管桩”的支栈桥为核心，通过内侧桩顶牛腿布置滑道梁，支撑滑移式河床开挖平台、固定式钻孔平台；通过统筹统一不同施工阶段所需设备型号，滑移式河床开挖平台可转化为固定式钻孔平台、支栈桥能够直接用于围堰吊装。计算分析与工程实践表明，此种平台具有结构受力安全、环境适应性好、投入少、工序转换快、施工效率高等优点。

In the construction of low pile caps buried deep in bare rock riverbed in non-navigable rivers in mountainous valleys， the conventional practice of using floating platform to excavate riverbed first， and then erecting fixed platform to construct bored piles and assemble cofferdams has some problems， such as poor adaptability of floating platform to periodically changing water level， large investment of two different construction platforms， and long interval of process conversion. Relying on the deep-water foundation project of pier 13 of Lishui Bridge on Shimen Railway， on the basis of proving that the underwater vertical slope of argillaceous sandstone riverbed can maintain stability by using finite element numerical analysis method， a fixed waterborne construction platform integrating the three functions of riverbed excavation， bored pile construction and scattered cofferdam hoisting is designed. The core of the platform is a trestle supported by bench steel pipe piles， and the sliding beam is arranged on the top bracket of the inner pile to support the sliding riverbed excavation platform and fixed drilling platform.By co-ordinating and unifying the types of equipment required in different construction stages， the sliding riverbed excavation platform can be transformed into the fixed drilling platform， and the trestle can be directly used for cofferdam hoisting. The calculation analysis and engineering practice show that the platform has the advantages of structural safety， good environmental adaptability， less investment， fast process conversion and high construction efficiency.