沱江特大桥钢板桩围堰及埋置式承台施工关键技术

Key Construction Technology for Steel Sheet Pile Cofferdam and Embedded Pile Cap of Tuojiang River Bridge

金简仁快速路沱江特大桥全长963m,主桥采用空间曲线独塔扭索面斜拉桥。桥址区域覆盖层为卵石薄层,下卧层为高强度中风化粉砂岩和砂质泥岩。主墩承台为大体积混凝土结构,埋置于河床面以下。为克服传统围堰在此类工程条件下的施工难题,提出“钢板桩+岩壁”新型组合围堰的解决方案。为确保钢板桩嵌岩深度>10m且垂直度偏差≤0.5%,采用“全护筒跟进引孔”工艺;同时,为确保围堰锚固稳定性和不透水性,采用“回填砂注浆止水”工艺。主墩承台施工过程中采取综合温控技术措施保证了大体积混凝土浇筑质量。监测结果表明,围堰变形、内支撑应力、混凝土温差等控制指标均在合理范围内,实现了特大型桥梁基础施工安全、效率与质量保障。

Tuojiang River Bridge on Jintang-Jianyang-Renshou Expressway has a total length of 963m,and the main bridge is a space curve single pylon cable-stayed bridge with twisted cable planes.The overburden at the bridge site is a thin layer of pebbles.The underlying stratum consists of high-strength moderately weathered siltstone and sandy mudstone.The main pile cap is a mass concrete structure which is buried below the riverbed surface.In order to overcome the construction problems of traditional cofferdams under such engineering conditions,a new type of composite cofferdam solution of“steel sheet pile+rock wall”was proposed.To ensure that the socket length of the steel sheet piles was greater than 10m and the perpendicularity deviation was less than 05%,the guide hole technology supported by full casing was adopted.Meanwhile,to ensure the anchoring stability and watertightness of the cofferdam,the water sealing technology by backfilling sand and grouting was adopted.During the construction of the main pile cap,the pouring quality for the mass concrete was ensured by the comprehensive temperature control technical measures.The monitoring results show that the control indexes,including the cofferdam deformation,internal bracing stress and concrete temperature difference,are within a reasonable range.The safety,efficiency and quality assurance are achieved for the super-large bridge foundation construction.