The gravitational field represents the fundamental stress field in geotechnical engineering. Its influence on soil mechanical behavior is manifested not only through variations in stress magnitude but also through stress gradient effects. However, existing soil mechanics frameworks and classical continuum-based numerical methods cannot characterize the intrinsic mechanical response of granular media under stress gradient conditions. Based on a previously established higher-order continuum theory incorporating stress gradient effects, this study develops a multiscale coupled Finite Element Method–Discrete Element Method (FEM–DEM) numerical framework. The method is implemented using Esys-escript in conjunction with the open-source discrete element platform Yade. By embedding representative volume elements (RVEs) at the finite element level and introducing gravity-induced stress gradients within the RVE using the discrete element method, stress gradient transfer and multiscale coupling are achieved. The proposed method is validated through numerical simulations of triaxial compression and trapdoor tests. The results demonstrate that the method can capture the microscale mechanisms associated with stress gradient effects and effectively resolve the constitutive solution difficulty encountered in the previously proposed generalized continuum framework incorporating stress gradients. The developed framework provides a new numerical tool for investigating the mechanical behavior of granular media under stress gradient conditions, with potential applications in geotechnical problems governed by gravitational fields, including deep underground engineering and extraterrestrial environments with non-conventional gravity.
Chen et al. (Mon,) studied this question.