Study on the effect of zonal excavation of deep foundation pit on adjacent subway tunnels in soft soil

The deeper the city subway is built, the more difficulty is to support the foundation pit along the subway line. Taking Shanghai Oriental Hope Headquarters Building as an example, the impact of deep pit zoning and layered excavation on the surrounding environment is analyzed. The support structures in different areas were differentially selected, and the B pit adjacent to the subway area was reinforced. The deformation and internal force distribution of the supporting structure under each working condition are calculated by finite element method, and compared with the monitored deformation of the supporting structure, which matched well with each other. The maximum displacements of the supporting piles and diaphragm walls occurred near the elevation of the pit bottom, and the maximum horizontal displacement of the supporting piles in pit A exceeded 50 mm, while that of the diaphragm walls in pit B was controlled to be less than 7 mm. The maximum surface settlement caused by excavation occurred in the area about 17mawayfromthe pit, with a maximum settlement of 33.8mm.The final horizontal displacement of the tunnel caused by the excavation of the pit was approximately parabolic, with the maximum horizontal displacement occurring near the middle of the pit, and the horizontal displacement of the downward tunnel close to the pit was larger than that of the upward tunnel which was a little farther away, but the maximum value was only 4.22mm, which was within the safety control range of the tunnel.