常泰长江大桥5号墩沉井基础下沉取土装备研究与应用

Research and application of soil excavation equipment for open caisson sinking of No.5 pier of Changtai Yangtze River Bridge

常泰长江大桥主桥为跨度1176 m的双层钢桁梁斜拉桥,该桥5号墩采用沉井基础。沉井为钢壳内填充混凝土结构,采用两端为圆端型截面、台阶型的新颖结构设计形式,是世界上最大水中沉井基础。根据施工要求,内、外井孔泥面需形成台阶,沉井下沉过程中需穿透粉质黏土层、砂质胶结层等硬质土层。为解决有关问题,研发了自动化气举取土集群控制系统、机械臂水下定点取土机器人,实现了井孔内高效取土与刃脚盲区取土全覆盖,引入高压旋喷、气水复合射流破土方法,有效解决了节点及隔墙处取土难题。沉井日均下沉量达到45 cm,平稳、高精度下沉至设计标高。

The Changtai Yangtze River Bridge is a double-deck steel truss cable-stayed bridge with a main span of 1176 m.Open caisson foundation is chosen for the pier No.5.The caissonis a steel shell structure filled with concrete,it is a novel structure design form with circular end section and stepped type,which is the largest submerged open caisson foundation in the world.According to the construction requirements,the steps shall be formed on the mud surface of inner and outer wells.During the sinking of the open caisson,it needs to penetrate the hard silty clay layer and sandy cemented layer.To address these issues,the automatic control airlift pump system and the underwater fixed-point excavating robot were developed,which realizes high efficient soil extraction and the full coverage of the blind area.Meanwhile,high pressure rotary jet and gas-water composite jet were applied for solving the problem of soil breaking at cross joint and partition wall.Average daily sinkage of the open caisson reaches 45 cm,and finally settles to the design elevation smoothly and accurately.