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 (epsilon phl ), inclination of long axis degree (k hl ), area (S hl ) and fullness degree (alpha hl ). With the increase of dynamic strain, epsilon 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, alpha 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.
