• Systematic field monitoring: A comprehensive monitoring system was established for the long-strip deep excavation in water-rich sandy strata, including 40 inclinometer points, 40 ground settlement sections, 24 groundwater level monitoring points, and 14 sections for strut axial force monitoring. • Revealing deformation evolution patterns: Based on monitoring data, the evolution of lateral wall displacement, ground settlement, and strut axial force with excavation depth and time was systematically revealed. A progression model of displacement curves from “oblique shape” → “pot-bottom shape” → “shallow inverted V shape” → “deep inverted V shape” was proposed. • Statistical parameter comparison: Combined with literature data, key deformation parameters (e.g., maximum lateral displacement ratio, settlement influence zone, ratio of settlement to lateral displacement) for excavations in water-rich sandy strata were statistically summarized, providing references for design. • Analysis of leakage impact: The significant influence of partial leakage on deformation rate and ground settlement was analyzed based on an actual leakage incident, emphasizing the importance of construction monitoring and disaster prevention. Understanding the deformation behavior of deep excavations in water-rich sandy strata is crucial for ensuring the safety and stability of urban underground engineering. This study investigates a long-strip metro station foundation pit constructed in such challenging geology. Through comprehensive field monitoring, numerical simulation, and statistical analysis of case histories, the deformation characteristics of a row-pile supported excavation are systematically analyzed. The results reveal significant spatio-temporal effects on pit deformation. The lateral displacement of retaining structures and the ground settlement behind them are more pronounced in the standard segment and along the long side of the pit compared to the end shafts and short sides. The development of lateral wall displacement and ground settlement trough evolves through distinct patterns with increasing excavation depth. Furthermore, internal support axial forces dynamically adjust during construction, with concrete struts requiring 30-60 days to stabilize and steel struts 15-20 days. Measured maximum axial forces were lower than design values, indicating conservative support design. Key statistical parameters are derived: the maximum lateral wall displacement ranged from 0.02% to 0.16% of the excavation depth( h e ), with its location at 0.56 h e to 1.27 h e . The maximum ground settlement ranged from 0.02% to 0.17% of he, occurring at 0.14 h e to 0.84 h e from the pit wall, within an influence zone of 1.00 h e to 2.00 h e . The ratio of maximum ground settlement to maximum lateral displacement varied between 0.40 and 1.47. These findings provide valuable references for the design and risk control of similar deep excavations in water-rich sandy strata.
Mingming et al. (Fri,) studied this question.