###### Abstract  
In the context of increasing environmental awareness and the demand for sustainable construction practices, the use of recyclable materials in civil engineering projects has gained significant attention. This study focuses on the bearing characteristics and deformation behavior of recyclable steel-pipe piles during the excavation of foundation pits. Field experiments and numerical simulations were conducted to comprehensively analyze the stress characteristics and surface settlement patterns behind the piles. The results reveal critical insights into the interaction between the steel-pipe piles and the surrounding soil, providing a detailed understanding of the stress distribution and deformation mechanisms. An empirical method for calculating the surface settlement value, induced by foundation pit excavation under the support of steel-pipe slope protection piles, has been proposed. This method improves the accuracy of settlement predictions and enhances the reliability of foundation pit design. recoverable steel-pipe piles; supporting structure; field test; pile strain; ground surface settlement +
Footnote †: journal: Applied  
ccepted: 29 June 2024  
Footnote †: journal: Applied  
ccepted: 29 June 2024  
have examined the applicability of micro steel-pipe piles in foundation pit support and reinforcement projects through model tests and field tests, revealing their action mechanisms and stress-bearing deformation patterns [10]. For large-diameter open-mouth steel-pipe piles, [PERSON] [11] used numerical simulation to study their load-bearing and settlement characteristics. Field tests have provided insights into the frictional resistance distribution along the pile body and the soil parameter values adjacent to the piles through combined field and numerical methods [12; 13]. Recent studies have extensively explored the application of micro steel-pipe piles in foundation pit support, while research on large-diameter steel-pipe piles has highlighted their stress-bearing and operational effectiveness when used as foundation piles. The excavation process of foundation pits inevitably disturbs the surrounding soil, causing deformation in both the supporting structures and the affected soil. Existing studies have focused on the settlement behavior of support structures and soil during the excavation process, particularly within the two-dimensional influence area of settlement [14; 15; 16; 17]. Additionally, soil settlement laws have been studied in the context of foundation pit dewatering [18; 19; 20]. In practical scenarios, foundation pits exhibit three-dimensional deformation. Many researchers have studied them through multiple methods [21; 22; 23; 24; 25; 26]. The settlement of soil behind pit walls varies between the long and short sides due to spatial effects. [PERSON] [27] analyzed measured data to determine the settlement laws of soil and the deformation of supporting structures under spatial effects based on statistical analysis of measured data from the excavation of thirty metro stations in Nanjing. [PERSON] [28] divided the soil behind foundation pit walls into two areas: Area A, unaffected by spatial effects, and Area B, affected by spatial effects. [PERSON] proposed ground surface settlement patterns for different influence areas, but these patterns consist of three broken lines that differ from the actual ground surface settlement curves. In summary, few studies have been conducted on the application of recoverable large-diameter steel-pipe piles in foundation pit support processes. Therefore, it is crucial to study the mechanical performance of these steel-pipe piles in such applications. This study employs field tests and finite element analysis methods to investigate the performance of large-diameter recoverable steel-pipe piles. It examines the deformation patterns of the piles during the support process and the ground surface settlement caused by excavation.