Influence of Consolidation Shear Stress Magnitude and Orientation on Stress–Strain Behavior of Sand under Traffic Loading

Traffic-load-induced principal stress rotation has been widely studied. Most of these tests were conducted using a hollow cylinder apparatus to simulate ground-level traffic conditions, and only one shear direction was considered. However, fewer studies focused on the stress conditions of subsoil below slopes or embankments, which involved bidirectional shear. In this study, a series of bidirectional cyclic simple shear tests were performed using the variable-direction dynamic cyclic simple shear apparatus to investigate the effects of multidirectional principal stress rotation on sand induced by traffic loads. The specimens were first $K_{\alpha }$-consolidated with various static shear stresses and then subjected to traffic-induced cyclic shearing in different directions. The experimental results showed that both the magnitude and orientation of the initial static shear stress had significant effects on sand strain development and stress–strain behavior. A larger angle led to a higher axial strain, while larger initial shear stresses led to stiffer sand responses.