Abstract: Considering fabric evolution effects is crucial for accurately describing the macroscopic mechanical behavior of cohesionless soil under cyclic loading. Building upon the nonlinear dilatancy equation established for sand-gravel composites under monotonic loading, a fabric-dilatancy internal variable, which accounts for fabric evolution during the dilatancy stage under cyclic loading, is introduced. An elastoplastic constitutive model based on the generalized plasticity framework is proposed to capture the full range of mechanical behaviors of sand-gravel composites under both static and liquefaction conditions. By comparing the liquefaction deformation, stress paths, and excess pore water pressure development of sand-gravel composites before and after considering fabric evolution effects, the significance of fabric evolution effects in simulating the liquefaction response of sand-gravel composites is demonstrated. The model's performance is validated through a series of large-scale triaxial tests on sand-gravel composites under both static and dynamic loading conditions, as well as by comparing with test results from relevant literature. The results show that the model generally provides a reasonable representation of the stress-strain-volume behavior of sand-gravel composites under static drained conditions, as well as the accumulation and dissipation of excess pore water pressure, stress path evolution, and liquefaction deformation during liquefaction. This model can serve as a powerful tool for numerical simulation in sand-gravel composites engineering.

Key words: sand-gravel composites, liquefaction, fabric evolution, nonlinear dilatancy equation, elastoplastic constitutive model