Abstract: In the construction of deep water platform of Beidou bridge's main pier, without adopfing underseal concrete base．we succeeded in directly using steel telescopic caisson's bottom slab as the encasing form and in only setting up the water seal lagging to seal up the water on the steel protecting lagging of the pile bottom．This paper illustrates the structure， the construction procedure and the key constnIction items of the steel telescopic caisson．

Key words: platform, steelteleseopieeaisson, undersealconcretebase, waterseallagging, construction

摘要： 在北斗大桥主墩深水承台施工中，采用无封底砼层仅在桩基钢护筒处设置止水套筒进行止水，直接利用钢套箱底板做承台底模，取得了成功.文中介绍了钢套箱的构造、施工工艺流程与施工要点，对类似工程施工人员有一定参考作用.

关键词: 承台, 钢套箱, 无封底砼层, 止水套筒, 施工