海上埋置式承台装配式双壁钢围堰研究

Study on Assembled Double-steel-wall Cofferdams for Offshore Embedded Platforms

深中通道伶仃洋大桥非通航孔桥上部结构均为110 m跨钢箱梁,下部结构采用群桩基础+埋置式承台+桥墩(整幅式、分幅式),深水区承台施工时最大抽水水头达24 m。承台围堰结构设计为装配式双壁钢围堰,横向分块,整幅式桥墩围堰由4个角块和2个水平块装配而成,分幅式桥墩围堰由4个角块装配而成,围堰主要由内外壁板、水平环、隔仓板、锁口钢管桩和内支撑5个部分组成。从开挖方量、支撑数量、入土深度、设备等方面,对比围堰分块下沉和整体下沉工艺,因整体下沉工艺具有挖方量小、支撑数量少、入土深度小、设备占有率低、围堰总重小等优点,确定围堰采用整体下沉工艺。采用有限元软件进行围堰施工模拟分析,得到围堰结构和封底混凝土受力均满足设计规范要求。

In the construction of Lingdingyang section of Shenzhen-Zhongshan Bridge,110m-span steel box girders served as the upper structure of non-navigable arch bridge,meanwhile,its lower structure consisted of pile cluster foundation,embedded platforms and abutments(overall and individual structures).The maximum pumping head reached 24m during the construction of platforms in deep waters.The platforms were protected by assembled double-steel-wall cofferdams,which could be divided into some transverse blocks.Overall abutment was assembled with four angle blocks and two horizontal blocks,individual abutment was assembled with four angle blocks.The cofferdam mainly composed of inner and outer wall panels,horizontal rings,partition plates,locking steel pipe piles and inner support.The overall sinking of cofferdam was compared with the process of sinking by blocks from such aspects as the amount of excavation,the number of supports,the depth below ground and the application of equipment.The former one led to less excavation work,fewer supports,shallow soil layer,lower occupancy of equipment and smaller gross-weight,and was selected in the construction.Cofferdam construction was simulated and analyzed by using Finite Element software,which showed that the structure and the stress acting on bottom-sealing concrete met the requirements of related design code.