Model test and numerical simulation study on soil arching effect evolution of pile-supported reinforced embankment

The load transfer mechanism of pile-supported reinforced embankments primarily relies on the synergistic interaction between soil arching effect and tensioned membrane effect of reinforcement materials, with its design rationality being crucial for engineering safety. However, existing studies have not reached a consensus on the assumed arch morphology, and most model tests adopt simplified conditions, particularly lacking systematic investigations on soil arching effects in cohesive fill materials and three-dimensional scenarios. To address this, this study employs a combined approach of model tests and numerical simulations to systematically investigate the influence of pile spacing, fill cohesion, and reinforcement materials on soil arching effects. The research results indicate that the differential settlement between piles and soil significantly influences the development of soil arching effects. Increasing the pile spacing promotes, to some extent, the mobilization of soil arching. The cohesion of the embankment fill contributes to load transfer, with higher cohesion leading to an increased pile-soil stress ratio and reduced differential settlement, demonstrating the dominant role of reinforcement materials in load distribution. Furthermore, the study establishes analytical equations describing the soil arching morphology in both the strip zone between two piles and the central area surrounded by four piles. Calculations reveal that the maximum arch height reaches $1.10(s-a)$ in the inter-pile strip area and $1.16\sqrt{2}(s-a)$ in the quad-pile central area. Principal stress vector analysis confirms the regional distribution characteristics of the arching structure. These findings elucidate the engineering mechanism by which cohesive fill regulates soil arching evolution through shear stress mediation, providing a theoretical basis for optimizing the design of pile-supported embankments.