重庆鱼洞长江大桥主桥墩围堰防渗支护施工技术

Construction technology of seepage control and timbering in pier cofferdam of Yudong Yangtze Bridge

重庆鱼洞长江大桥为连续跨梁结构,其主桥墩14#、15#墩位于长江主河槽左右侧,桥墩基础采用低桩承台,承台底部位于枯水位以下7.0m左右,需要填岛和施工围堰才能进行承台的开挖和浇筑。在河中央的土石围堰中为了形成可开挖的基坑,防渗和支护是相辅相成的两个关键因素,由于土石围堰存在严重的架空结构和流动水,防渗支护难度较大。本文研究了膏浆性质,并根据鱼洞大桥桥墩的地质条件,详细讨论了速凝膏浆结合稳定浆技术的运用、施工工艺和效果评价,为动水下块石架空桥墩土石围堰进行防渗支护提供了一种有效、经济的施工技术。

The structure of the Yudong Yangtze Bridge is of continuous girder type. Its main piers, 14^# pier and 15^# pier, are situated separately at the left and right sides of the main river course. The foundation of piers is very deep with platform bottom 7.0m under water level in dry season. A cofferdam is needed to construct the platform of pier foundation. The seepage control and timbering support for the construction pits were the two key factors. The difficulty was to control seepage and retain the foundation slope because of the cofferdam＇ s large-cavity stratum and flowing water. According to the geological conditions of the bridge, a kind of quick-hardening paste was used. The characteristics of the paste were analyzed, the application of the paste and the relevant technique were studied in detail. The effectiveness of the method was evaluated. It was proved that this technology can be one of the effective and economical methods for constructing pier cofferdams under the conditions of large-cavity stratum and flowing water.