Field Monitoring Analysis of Construction Process of Deep Foundation Pit at Subway Station

Taking the excavation of deep foundation pit of a subway station in Ji’nan city as the background, and the measured data of the deep-horizontal displacement, support axis force and the surface settlement of the retaining pile body during the excavation was analyzed. It was shown that with the increase of excavation depth of the foundation pit, the position of the maximum horizontal displacement of the pile gradually moved downward from the top of the pile, and the pile deformation curve gradually changed from a similar cantilever beam to a “bow shaped” curve, the phenomenon of moving to the outside of the pit occurred at the top of the pile in the end-well of subway station. It is necessary to prevent the first reinforced concrete support and the retaining structure from being broken due to the lateral displacement of the top of the pile. The foundation pit excavation caused the settlement of the surrounding surface. The maximum settlement point was about 15 m from the boundary of foundation pit. The maximum surface settlement value was located in the middle of the standard section. The maximum settlement was 18.5 mm. The maximum horizontal displacement of ZQT37 measuring point at the standard section was 23.79 mm, and the location of maximum horizontal displacement was approximately 17 m from the top of the foundation pit. The axial force of the concrete support and the third steel supports at the ZCL20 section of the standard section were the largest. All supports were in safe working condition during excavation of the foundation pit.