Abstract:

At present, there is no semi construction experience and settlement control standard for main structure of underground station. The main structure of Lanzhou Zhongchuan Airport Underground Station is constructed by semi construction method; and the uneven settlement standards for the underground station should be settled according to relevant standards and documents. The uneven deformation rules of the foundation and the stress of the station structure are analyzed under 7 conditions of the station structure with and without top roof backfill by software FLAC3D. The study results show that: 1) The deformation potentials can be classified into 5 levels, i.e. safety, single index warning, double index warning, critical state (as long as one index reached) and ultralimit (as long as one index reached). 2) The semi construction with postcast strip is good for uneven settlement control during construction period and following long term. It is also good for structural stress during construction period but not for structural stress in long term. As a result, the semi construction without postcast strip is recommended. 3) The deformation potentials of underground station in sandy loess under different working conditions vary obviously. The double index warning and single index warning occur under working conditions of semi construction. 

Key words: sandy loess, underground station, semi construction, uneven settlement, control standard