Abstract: The upward displacement of pile and floor is a damage for the balance of support system during the excavation foundation of pit in thick alluvial clay Nishihara model improved with Newton fluid could well describe the behavior of creep deformation during pit excavation,and also trace the behavior of interface between pile and soil.The regularities of upward displacement of floor in the presence of different ratios of inserted pile depth to excavation depth,side lengths and spacings of support pile,as well as the rebound of column pile in the presence of different depths in soil,positions and types of column pile were analyzed via field data,improved Nishihara model and secondary development of FLAC^3D.The deep foundation pit of Culture Center of Jinan Province was taken as an engineering background.Results revealed that the sensitivity of the upward displacement of pit floor to different factors follows the order of:distance of adjacent support pile>ratio of inserted depth to excavation depth>length of support pile; and the sensitivity of the rebound of column pile follows the order of depth of column pile in soil>position of pile>shape of plie. The results could be a guidance for reducing the influence of excavation on the upward displacement of pile and floor.

Key words: improved Nishihara model, thick aluvial, rebound of foundation pit, column pile rebound, sensitivity analysis