Dynamic characteristics of coal gangue subgrade filler under traffic load based on the hysteretic curves

Traffic cyclic loading is the key factor that leads to the deterioration of the long-term service behavior of subgrade. A series of cyclic triaxial tests was carried out by the large-scale dynamic and static triaxial apparatus (LSDSTA) to study the dynamic behaviors of coal gangue subgrade filler (CGSF) under multi-step cyclic loading using the morphological characteristics of hysteretic curves (MCHC). MCHC was quantitatively characterized by four parameters, i.e., the unclosed degree (ε_phl), inclination of long axis degree (k_hl), area (S_hl) and fullness degree (α_hl). With the increase of dynamic strain, ε_phl increases exponentially. k_hl of the coal gangue sample first decreases and then shows an increasing trend with the increasing dynamic strain. The values of S_hl are close to each other, and the energy dissipation in the sample is small. However, with the increase of dynamic strain, the specimen failure degree is increased, S_hl increases exponentially, and the damping ratio increases. With the increase of dynamic strain, α_hl increases approximately linearly. Confining pressure has a certain effect on the four parameters. There parameters can be recommended and used for quantitative analysis the dynamic behaviors of subgrade filler under traffic cyclic loading.