几种悬索桥锚碇结构基坑的施工风险分析及对策

润扬长江公路大桥南汊悬索桥北锚碇基坑工程,在初步设计阶段,结合科研,针对冻结壁围护结构、沉井、地连墙围护结构的设计方案,进行了施工风险分析和对策研究(特别是冻结法方案)。针对冻结法方案大直径结构冷量损失大、冻结壁均匀性要求高、基底突水、停电等风险,提出了三排冻结管布置、冻结壁保护、基底注浆、双回路供电、钢筋混凝土内衬等对策;针对沉井下沉控制困难、地表沉降及井底流砂等风险,提出了空气幕或触变泥浆助沉、控制降水等对策;针对地连墙成槽风险,提出了液压铣槽机成槽等对策。最终将地连墙围护结构方案用于工程实践,实现了润扬大桥北锚基坑施工的万无一失。

Construction Risks and Countermeasures of Some Different Kinds of Anchorage Pits of Suspension Bridge

In the designing process of north anchorage pits of the south suspension bridge for the Runyang Yangtze River Bridge,based on the science researches,the risks and countermeasures of three kinds of bracing structures,including the frozen wall supporting system(specially considered),the open caisson and underground continuous wall were put into careful analysis during the preliminary design stage.Considering large-diameter structure will lose large amount of refrigerating capacity if freezing method is adopted,and also this method raises high requirements to freezing wall leveling,and have risks like water-inrush from foundation and power cut,thus it is proposed a few countermeasures including three rows of freezing pipes,freezing wall protection,foundation grouting,two-circuit power supply,reinforcement concrete as internal liner.As for difficult control of caisson sinking,ground subsidence and sand floating in shaft bottom,it is proposed to use air curtain or thixotropy mud to help sinking,control precipitation.As for the risk of ground and wall forming into groove,it is proposed to use hydraulic slot milling machine.The project practice of the underground continuous wall has realized the safety and success of the construction of the north anchorage pits for the Runyang Yangtze River Bridge.