Simultaneous construction of adjacent projects may lead to emergencies in a foundation pit group, which significantly affects the deformation and safety of foundation pits. In this study, the deformation characteristics of a deep foundation pit group and the mutual interactions among the adjacent foundation pits were observed by a monitoring system during excavation. Field data of the foundation pit group, including the lateral deflections of the enclosure pile, the ground subsidence, as well as the vertical column movements, were analyzed and compared with individual excavations in Shanghai. The field data showed that the excavation of the adjacent foundation pit reduced the lateral deformation of the enclosure structure, caused by the reduction of active earth pressure acting on the retaining pile. Furthermore, the foundation pit excavated later caused upward movements of the soil between them. However, the foundation pit excavated earlier had a negligible influence on the vertical column movements of the foundation pit excavated later. Due to the optimized excavation sequence of the deep foundation pit group, the deformation of this special excavation was well controlled.

A series of centrifuge model tests were conducted to study the interaction between successively constructed adjacent foundation pits. The stress, deformation, and earth pressure on retaining structures and the settlement of the soil between the two adjacent foundation pits during successive construction were investigated by a comprehensive instrumentation program. To reveal the effect of the construction sequence, both the stress and deformation of successively constructed foundation pits were compared. The results showed that the stress and deformation of the retaining structure in the foundation pit constructed first were larger than those in the foundation pit constructed later. Due to the inward displacement of the soil around the foundation pits excavated first, the first strut of the foundation pit constructed later underwent high tension during the construction of the first foundation pit. The lateral deformation of the retaining structure of the foundation pit excavated first increased with the increase of the excavation depth. However, the excavation of the second foundation pit reduced the earth pressure on the retaining wall between the two excavations, thus leading to the recovery of the inward deformation in the first excavation. However, the top of the retaining wall deformed into the first foundation pit during the whole construction. The settlement of the soil between the two foundation pits showed a superposition effect. During the construction of the two foundation pits, the settlement of the soil between them kept increasing. The active earth pressure on the middle wall of the foundation pit constructed later was lower than that on the middle wall of the first foundation pit. The excavation of the foundation pit constructed later had no significant effect on the passive earth pressure of the first foundation pit.