Deformation Characteristics of an Ultra-Deep Foundation Pit Supported by Servo Steel Struts in Reclaimed Areas

This paper presents a case study on an ultra-deep excavation in a reclaimed area supported by servo steel struts, addressing the limited case-specific data on deformation behavior under such complex geological conditions. Comprehensive monitoring of the pit structure and surrounding environment was performed throughout construction. Results highlight significant time-dependent deformation due to the rheological behavior of artificial fill and soft soil, with metro tunnel displacement during suspension phases contributing up to 29% of the total. Servo steel struts, via active axial force compensation, reduced maximum diaphragm wall displacement by 24%, ground settlement by 29%, and pipeline settlement by 46% compared to conventional supports. Integrated measures, including bottom-sealed diaphragm walls, isolation piles, and grouting curtains, successfully confined tunnel deformation within 5.4 mm, complying with strict safety criteria. A strong linear correlation between tunnel and wall displacements was observed, enabling a predictive envelope model for deformation. This study underscores the efficacy of servo steel struts in controlling excavation-induced deformation in reclaimed areas and offers practical insights for designing and managing ultra-deep excavations in similar challenging settings.