Characteristic of cyclic loading due to passing wheels is associated with one-way loading without stress reversal,which includes a simultaneous cyclic variation of vertical normal stress and horizontal normal stress lasting for a long period of time and generally takes place in partially-drained conditions.Therefore,it is of great practical relevance to study the deformation behaviour according to the characteristic of traffic loading.In this work,a series of one-way stress-controlled cyclic triaxial tests with a simultaneous variation of the vertical and horizontal stress components during cyclic loading were conducted to investigate the deformation behaviour of natural K_0-consolidated soft clay in partially-drained conditions.Test results demonstrate that not only the deviator part of the stress rules accumulation but also the volumetric part significantly contributes.While the deviator part of the stress amplitude is held constant,the increase amplitude of cyclic confining pressure will promote the development of both permanent volumetric strain and axial strain significantly.Furthermore,the effects of cyclic confining pressure on the deformation of natural K_0-consolidated soft clay was quantified.Finally,an empirical formula for permanent axial strain considering the effects of cyclic confining pressure was proposed which can be used for feasibility studies or for the preliminary design of foundations on K_0-consolidated soft clay subjected to traffic loading.
The discrete element method was used to investigate the microscopic characteristics of granular materials under simple shear loading conditions. A series of simple tests on photo-elastic materials were used as a benchmark. With respect to the original experimental observations, average micro-variables such as the shear stress, shear strain and the volumetric dilatancy were extracted to illustrate the performance of the DEM simulation. The change of anisotropic density distributions of contact normals and contact forces was demonstrated during the course of simple shear. On the basis of microscopic characteristics, an analytical approach was further used to explore the macroscopic behaviors involving anisotropic shear strength and anisotropic stress-dilatancy. This results show that under simple shear loading, anisotropic shear strength arises primarily due to the difference between principal directions of the stress and the fabric. In addition, non-coaxiality, referring to the difference between principal directions of the strain rate and the stress, generates less stress-dilatancy. In particular, the anisotropic hardening and anisotropic stress-dilatancy will reduce to the isotropic hardening and the classical Taylor’s stress-dilatancy under proportional loading.
