Design Practice of Deep Foundation Pit Excavation Adjacent to Metro in Soft Soil Area

Foundation pit of Suzhou's Shin Kong Mitsukoshi project is a typical deep foundation pit in soft soil area,the nearest distance is only 12 meters on the south side with the new metro line interval,and only 6 meters with Times Square Station basement exterior wall The pit has the strict environmental protection request and complicated geological conditions.Simultaneously,the project construction period is very nervous,and less than 20 months from engineering piles completed to the tower cap structure completed,the conventional scheme is difficult to achieve the above requirements.This paper introduces the excavation engineering difficulties,and targeted measures taken-the pit and underground structure partition,steel support axial force servo system,the composite diaphragm wall,isolating confined water with ultra-deep diaphragm wall etc.Through the analysis of the monitoring data,slop monitoring,the subway structure displacement,confined water indicators are within the prescribed values,the construction period of main structure and the smooth operation of Metro line are ensured.