南京浦仪公路西段跨江大桥主桥施工技术

南京浦仪公路西段跨江大桥主桥为主跨500 m的钢箱梁斜拉桥,采用钻孔桩基础,桥塔为大断面独柱形钢塔,通过高强拉杆与承台和塔座连接,主梁分左、右两幅布置。钻孔桩基础采取搭设钢平台的方式施工;钢塔采用大型浮吊和塔吊安装;钢箱梁采取边跨浮吊高支架存梁+中跨桥面吊机单悬臂拼装的方式施工;斜拉索安装采用塔端挂设、梁端压锚、梁端张拉的总体施工工艺。施工过程中,钻孔桩砂质泥岩钻进时,采取高焊齿滚刀钻头解决中风化砂质泥岩易糊钻问题;钻孔桩检测合格后,进行钻孔平台拆除和围堰安装;利用BIM技术对钢塔首节段定位进行模拟,通过足尺模型试验,选择水泥基灌浆料,采用立轴式搅拌机在高位搅拌进行塔底灌浆,确保灌浆密实度;中跨合龙采用无工艺拼接板自然温差合龙法,保证了安装精度和成桥线形。

Construction Techniques for Main Bridge of West River-Crossing Section of Puyi Highway in Nanjing

The main bridge of west river-crossing section of Puyi Highway in Nanjing is a steel box girder cable-stayed bridge with a main span of 500 m.The bridge consists of identical left and right structures.The pylons are large-cross-section and mono-columned steel structures supported by bored pile foundations,the pedestals of which are connected with the pile caps by high-strength rods.Steel platforms were installed to ease the bored pile foundation construction.The steel pylons were erected using the large floating crane and the tower crane.The steel box girders in the side spans were first stored on high-rise scaffolds and then hoisted by floating crane,while the steel box girders in the central span was assembled in a single cantilever way using deck crane.The stay cables were stretched down from the pylons,anchored to the main girder and tensioned.Given that the bored piles had to be driven through silty mudstones,the milled-tooth bits were selected,since this kind of bits are not easy to be stuck by mud.After the quality of the bored piles was verified,the steel platforms were demolished and cofferdams were installed.The positioning process of the first pylon section was simulated by BIM,and full-scale model test was also conducted.To ensure the compactness of the cementitious mortar,vertical agitators were used for mixing and blending.The central span was closed by using the natural temperature difference closure method,which required no splices and could assure the installation precision and geometry of the completed bridge.