Investigating the long-term deformation behaviour and non-coaxiality of siliceous sand under traffic cyclic loading

Subgrades composed of siliceous sand are often subjected to traffic-induced cyclic loads. However, there is a knowledge gap regarding the long-term deformation behaviour and non-coaxiality of siliceous sand under high-cyclic traffic loading. This study addresses this issue by conducting a series of drained high-cyclic tests using a hollow cylinder apparatus to simulate an anisotropic heart-shaped stress path. The effects of cyclic stress ratio (I) and torsion-shear stress ratio (;id) were carefully evaluated and interpreted. The results showed that an increase in I and ;id results in a higher axial cumulative strain and resilient modulus, along with increased susceptibility to volumetric contraction. The dilatancy d (deacc v/deacc q ) characterizing overall deformation accumulation experienced a transformation of first stabilizing then declining. By contrast, the individual stress-dilatancy relations within loading and unloading stages exhibited an inward movement trend. Moreover, the development and influencing factors of non-coaxiality were meticulously analysed, revealing that while the number of loading cycles had a negligible effect on non-coaxiality behaviour, it was considerably influenced by stress levels. A significant increase in the range of non-coaxiality angle variation was observed at larger I and ;id values. This study provides insights for the construction and design of tunnel foundations and pavement engineering.