Systematical calibration and validation of discrete element models for fiber reinforced cement treated aggregates

Cracking of pavement materials affects the service performance of pavement structures. It is widely investigated by discrete element method (DEM) because the DEM can present the cracking behavior and mechanism from the mecroscopic perspective. However, improper calibration method is time-consuming and the simulation results are not applicable for different loading conditions. To address this issue, a systematical calibration method is proposed to establish a more reasonable DEM model, and it is used to explore the cracking behavior and mechanism for pavement materials. The fiber reinforced cement treated aggregates (F-CTA) used to construct the pavement base are selected as an example to elaborate the process. First, contacts within the F-CTA were divided into five groups according to physical components. Then, laboratory tests were performed to obtain macro mechanical properties including strength and modulus. Next, the corresponding virtual tests were established and the contact model parameters were calibrated from mono-component to mixture. This calibration method was validated by the three-point bending test incorporating all contact parameters obtained from the above calibrations and the process of cracking evolution was analyzed. Results show that the simulated mechanical responses and crack distribution based on the systematical calibration are in good agreement with laboratory measurements and observations, exhibiting well reliability for calibrating contact parameters of composite material. Young's modulus of the F-CTA is sensitive to the mecro effective modulus in the virtual indirect tensile test while Young's modulus and tensile strength are vulnerable to the mecro cohesion in the virtual uniaxial compression test. The mortar-aggregate and mortar-aggregate interface is relatively weak where cracks are prone to appear. The fibers can optimize the distribution of the crack network. The cracking evolution contains three stages and the second stage has a significant influence on the cracking behavior of the F-CTA.