Field performance of large-scale deep excavations in Suzhou

The performance of large-scale deep excavations in Suzhou, China is comprehensively examined based on a great deal of field data, concerining the excavation of Suzhou Modern Media Plaza (SMMP), 11 rectangular excavations (i.e., aspect ratio of length to width is around 1.01~2.68) constructed by the bottom-up method and supported by auger-cast-in-place piles, and at least 23 long and narrow metro station excavations supported by diaphragm walls in the same area reported in literatures. On the basis of the analysis of monitoring data, some major findings are obtained: (1) the average of the maximum lateral wall deflection, δ_hm, is 0.08%H_e for the rectangular excavations and 0.20%H_e for the metro excavations, where H_e is the excavation depth; (2) the depth H_m, where δ_hm occurs, falls between H_m = H_e-10 and H_m = H_e + 5 for the rectangular excavations and between H_m = H_e-7 and H_m = H_e + 8 for the metro excavations. H_m of the excavation propped by steel-reinforced concrete struts is a little smaller than that propped by steel pipe struts; (3) the maximum ground surface settlement, δ_vm, is around (0.01%~0.09%) H_e for the rectangular excavation of SMMP supported by diaphragm walls and around (0.04%~0.27%) H_e for the metro excavations. The ground settlement zone is about 4.5H_e behind the retaining walls for the metro stations which is larger than that of the rectangular excavations; (4) the ratio of δ_vm/δ_hm is around 0.13~1.07 for the excavation of SMMP and around 0.22~1.65 for the metro excavations; (5) the vertical column movement, δ_cu, is around (0.07%~0.26%) H_e for the rectangular excavations and around (0.10%~0.23%) H_e for the