Abstract: The entrance structure of Shenjiamen Harbor immersed tunnel is designed to be sandbag cofferdam. However, due to the effect of ground condition, the tide and the rigidity of the sandbag, displacement occurs to the cofferdam. In order to ensure the successful construction of the entrance structure of the immersed tunnel, the causes for the displacement of the cofferdam is analyzed and different consolidation options are discussed, which leads to the determination that steel pipe piles are used to consolidate the cofferdam. The construction technologies and effects of sandbag cofferdam consolidated by steel pipe piles are presented. The construction technologies of sandbag cofferdam and twin steel pipe piles can be used perfectly by using steel pipe pile consolidation technology. In the end, good economical and social benefits are gained. 

Key words: immersed tunnel, steel pipe pile, cofferdam, sandbag, foundation treatment 