Analysis and Study of Deformation of Foundation Pit Excavation in Soft Soil Considering Time-space Effect

Based on a deep foundation pit project in Tianjin soft soil area,the in-situ monitoring data of deep horizontal displacement and vertical displacement of supporting pile,vertical displacement of the surrounding building and the surrounding ground are summarized in the process of foundation pit excavation,the change rules of them are analysed,the influences of the time-space effect are studied.The study results show that the foundation pit excavation have significant space-time effect on supporting piles and surrounding environment,the displacement occurs mainly in the stage of excavation,especially in the third stage of excavation,the increment of displacement is greater,the rate of change is faster,after the foundation pit floor construction is completed,the displacement tends to be stable;The deep horizontal displacement of the supporting pile shows the trend of “bulging”,the maximum displacement occurs near the excavation surface;The maximum surrounding surface displacement is located at the position of 6 m(0.51H) from the foundation pit,the displacement curve shows a basin shape,when the underground structure of foundation pit is completed,the maximum displacement occurs at the DB2-3 monitoring point,the displacement valueis -22.7 mm(about 0.19 H%);It is suggested that the pile-anchor retaining structure replaced the original design support form in the south and west side of the foundation pit,the research results can provide references for similar projects.