Granular materials are associated with the irreversible behaviors during the loading-unloading-reloading path

the mechanism of which can be analyzed in terms of complex network evolutions. In this paper

the discrete element method is used to conduct triaxial tests for granular materials under the loading-unloading-reloading condition. The macroscopic responses of the granular materials and its corresponding complex network characteristics of different strong contact systems are analyzed. It is found that the macroscopic “hysteresis loop” is formed during the loading-unloading-reloading path of dense granular materials

and the microscopic coordination numbers and clustering coefficients also exhibit irreversible behaviors. Different thresholds are used to classify the strong and weak contact systems for granular materials under different loading and unloading stress states

and the difference in the mesostructure corresponding to each stress state decrease as the threshold increases. The maximum cluster of the strong contact system reaches the limit of percolation when the force threshold falls in a range

and the irreversible behaviors of granular materials can be reflected in the geometric and topological features of strong network during the loading-unloading- reloading path.