Method for building subway station by expansively digging large-diameter shield tunnel

The invention relates to a brand new method for building subway station by expansively digging large-diameter shield tunnel; namely, based on the large-diameter shield tunnel, the subway station is dug and built by shallow bedding and undercutting method. The invention mainly comprises the following steps: (1) assembling the large-diameter shield segments for the station in the range of the station; (2) building bottom girder, rectangular column and top girder in the shield tunnel, and establishing a temporary support; (3) symmetrically digging first supporting protection of the platform tunnel by the shallow bedding and undercutting method; (4) symmetrically removing the shield segments, the temporary support and other temporary structures; (5) constructing the second lining and platform panel of the platform tunnel. The invention gives full play of the advantages of the shield method and the shallow bedding and undercutting method, which can largely reduce the influence to the surrounding environment and adjacent building structures under complex construction environment of city; the construction period is shortened and the project cost is decreased.