Deformation of servo steel supported zoned excavation pits in Hangzhou soft soil

Zonal excavation and servo-active regulation are two common methods for controlling deformation in soft soil deep foundation pits. However, in-depth research on the deformation behavior of foundation pits under the combined effect of these two methods remains limited. This study focuses on a large soft soil foundation-pit project adjacent to a subway station and tunnels in Hangzhou and proposes a method to evaluate surface settlement profiles outside the zoned excavation pits. To this end, long-term on-site monitoring of soil displacements and diaphragm wall deformations during the excavation process is performed. The results show that surface settlement near the pit edge is primarily influenced by the construction of the outermost pit, whereas the settlement further away is predominantly affected by the construction of a second sub-pit from the edge. Pits located outside the metro protection line have a relatively smaller impact on surface settlement. The servo-active control system occasionally causes localized pushback of the diaphragm wall, leading to an “S-shaped” deformation pattern. The zonal excavation method proves beneficial in optimizing the excavation scheme and enhancing the rigidity of the support system. The combined use of the servo-active control system and zonal excavation method effectively regulates foundation pit deformation. The study findings confirm the validity of the subway protection line and support the excavation scheme employed. Thus, this study serves as a guide for performing deformation control during the construction of large soft soil foundation pits in the Hangzhou area. • Long-term monitoring of the Hangzhou neighboring railway subdivision excavation was performed with the application of servo-active regulation. • An evaluation method applied to the surface settlement profile outside a zoned excavated foundation pit is proposed. • Evaluated deformation in servo actively regulated Hangzhou zoned excavation.