Abstract：The settlement of thick backfill sand foundation in phase I of Yangshan deepwater seaport project is calculated by specification and one-dimensional consolidation theory. Based on layered settlement data measured in field，compressibility modulus and consolidation coefficient of soil layers are obtained by back analysis method，and thus the post-construction settlement of the foundation is predicted. It is demonstrated that the post-construction settlements of the treated backfill sands at almost all the sequence settlement measurement points of Yangshan deepwater seaport are all less than 60 mm，those of untreated backfill sand and subsoil are all less than 300 mm，and that the post-construction settlement is mostly caused by the compression of the untreated backfill sand and subsoil，which consists of 80.90%～88.19% total post-construction settlement. The investigation can provide references for design and construction of other great deepwater seaport project.
