Field Investigation of Deflection Characteristics and Control Strategies of a Short Floating Pile Adjacent to Deep Excavation

This case study aims to evaluate the impact of deep excavation on the adjacent short floating pile and lateral deformation control strategies using capsule expansion technology (CET). Two control strategies, i.e., real-time control (RTC) and one-time control (OTC), were applied to control the lateral displacement of piles. In this case, the wall lateral deflections (δhm) range between δhm=0.075%He and δhm=0.11%He, which are relatively small and less than the specified protection levels. Although the wall deflection was controlled to a relatively small level through reasonable excavation and support schemes, the maximum horizontal displacement of the short floating pile reached 13.2 mm (0.054%He). Therefore, reasonable deformation control measures are necessary. After three stages of RTC treatment, the maximum lateral displacement of P2 was reduced by 49.2%, while P1 was decreased by 22.7% treated by OTC. Meanwhile, multiple RTCs can always control the pile deformation within the cracking limit, which avoids the dilemma of protecting the pile after it has been damaged. It confirms the feasibility and efficiency of CET in controlling pile deformation in real-time. In addition, RTC for pile lateral displacement mainly includes two aspects: (1) expansion directly induces lateral displacement of piles; and (2) expansion compensates for the soil stress loss in front of the pile to reduce the impact of the next excavation on the pile. Therefore, as external influence sources have long-term adverse effects on adjacent piles, RTC as an efficient control method should be given priority consideration for controlling pile lateral displacement.