沪通长江大桥万吨级钢沉井浮运出坞施工关键技术

Key Construction Techniques for Floating Ten-Thousand-Ton Steel Caissons Out of Dock for Hutong Changjiang River Bridge

沪通长江大桥主航道桥为(142+462+1 092+462+142)m双塔连续钢桁梁斜拉桥,该桥桥塔墩钢沉井顶面平面尺寸为86.9m×58.7m,其中29号墩钢沉井高56m,重量达1.6万吨,采用船坞内整体拼装成型后出坞浮运至桥位。为满足船坞内地基承载力的要求,对钢沉井的刃脚进行抄垫,刃脚抄垫后灌注2.5m高刃脚混凝土;1.6万吨钢沉井入水后的理论吃水深度为12.4m,而浮运所经航道最大水深仅10.5m,在钢沉井中间12个井孔底口以上15.9m处对称增设钢结构封闭盖板,在封闭井孔内加注压缩空气,以调整钢沉井的吃水深度使钢沉井在出坞及浮运状态下的实际吃水深度为7.5m;对钢沉井的出坞水位进行系统分析;做好出坞前各项检查、出坞时机的选择、拖轮的配备、安全措施等准备工作。钢沉井在船坞内拼装成型后,船坞内放水起浮,系缆、抄垫后开启坞门,船坞内拖轮编队出坞,浮运钢沉井至桥位。

The main navigational channel bridge of the Hutong Changjiang River Bridge is a two-pylon continuous steel truss girder cable-stayed bridge with span arrangement of（142＋462＋1 092＋462＋142）m.The plan dimension of the top of the pylon pier steel caisson is 86.9 m×58.7m.The steel caisson for the pier No.29 measures 56min height and weighs up to 16 000 t,which is monolithically assembled to take shape in the dock and transported to the bridge site.To meet the ground bearing capacity demands in the dock,the cutting edges of the steel caisson were cushioned and cast 2.5-m thick cutting edge concrete.In the center of the steel caisson,at the15.9mlocation above the base opening of the 12 caisson holes,the steel sealing cover plates were symmetrically added.The closed caisson holes were filled with compressed air to make the actual draft of the steel caisson remain 7.5mduring the time it was transported out of the dock and in the process of transportation.The out-of-dock water level of the steel caisson was systematically analyzed.Before the caisson was transported out,a series of preparations should be done,including various checks,the selection of proper out-of-dock time,the tugboats used and the related safety measures.After the steel caissons took shape in the dock,the dock was filled with water to allow the caissons to float and the cables were fastened.After the cutting edges were cushioned,the door of the dock was opened.The tugboats inside the dock were numbered to transport the steel caissons to the bridge site.