Experimental study on the vertical load-bearing performance of single piles and pile groups in saline soil foundations

To investigate the vertical bearing performance of single and group piles in layered saline soil, a series of indoor model tests were conducted. A multi-pile theoretical calculation model correlating soil salinity, pile-soil shear stiffness, and vertical bearing capacity was established, and corresponding calculation methods for single and group piles were further proposed. The Q-S curves, pile top stiffness, and pile group interaction coefficients under different salinity conditions were acquired via model testing, and the influencing mechanism of saline soil salinity on pile group interaction was systematically analyzed. Test-derived stiffness and pile group efficiency coefficients were compared with theoretical calculations to validate the reliability of the experimental results. Consistent with the unified logical framework of the manuscript's Results and Discussion sections, this study clarifies the differential effects of soil salinity on pile bearing behavior: varying salt concentrations do not change the overall evolutionary trend of pile Q-S curves, whereas they impose a significant quantitative influence on ultimate bearing capacity. Under identical loading conditions, increasing soil salinity effectively reduces the settlement of both single and group piles and enhances pile top stiffness, thereby shifting the Q-S curves toward lower settlement values. Obvious pile-pile interaction exists in pile group foundations, while the stiffness of group piles does not exhibit a simple multiple relationship with that of single piles. Additionally, the pile group effect gradually weakens with the increase in the number of foundation piles.