Analysis of Influence of Foundation Pit Excavation and Confined Water-Inrush on Pile Bearing Capacity

This paper discusses the influence of foundation pit excavation and inrushing for confined water to pile bearing capacity through a typical engineering case. In this case, the distribution of aquifer and the depth of water level are investigated by field test which are used to calculate and find the causes of inrushing for confined water, combined with the process of inrushing and engineering construction conditions, the causes of inrushing for confined water are found. Then in-situ static cone penetration test is carried out, which is used to find the disturbance depth and extend of soil layers caused by foundation pit excavation and inrushing for confined water, while the relations are suggested between disturbance degree of each soil layer and pile capacity parameters, with this relationship, it is easy to see the disturbance law of these influences. The results show that confined water going through the plug in pipe pile is the main reason of inrushing, the depth of influence of foundation pit excavation on the soil strength below the pit bottom is about 6.5 meters to 9 meters, and the disturbance degree decreases linearly with depth increase. By comparison, the inrushing's influence on the soil strength is much greater than foundation pit excavation, the influence range are from a distance of 2 meters above the pile tip to a distance of 4 meters under the pile tip, and the maximum disturbance degree reaches 0.91. Additionally, the lowest bearing capacity of pile foundation is at the location of inrushing point, the farther away from the inrushing point, the larger bearing capacity can be achieved.