Abstract: To a deep and narrow foundation pit for a subway underground station in a soft ground of Shanghai, a detailed statistical analysis based on the site monitoring database has been conducted on the settlements of the ground surface and the surrounding buildings, the horizontal displacement of diaphragm wall, the uplift of the diaphragm wall and the upright column. Then, the spatiotemporal developing characteristics of deformation and the corresponding incentive are analyzed. Meanwhile, the relationships among the maximum lateral displacement of diaphragm wall ?hm, the maximum ground surface settlement ?vm and the existing statistical results are also compared and analyzed. The results show that the deformation spatiotemporal effect of a long and narrow deep foundation pit in soft ground is quite obvious. Compared with the predicted results obtained from the site monitoring database of some deep foundation pits in Shanghai area, the relationship curves between the ground surface settlement and the depth of the foundation pit is lower than that given before ones obviously. To the maximum ground settlement ?vm of the ground surface, the above finding is also existing. The main reason is that the supporting system for a narrow and long foundation pit is different from that for a general deep foundation pit, which proves that the diaphragm wall with the multilayer horizontal inner symmetrical supports can control the deformation of a narrow and long foundation pit for subway underground station built in soft ground.

Key words: thick and soft site, deep foundation pit, subway underground station, site monitoring, statistical analysis