Characterization of the Resilient Modulus of Soil–Pebble Mixtures Using Discrete Element Modeling and X-ray Computed Tomography

ABSTRACT

Soil–pebble mixtures containing particles larger than 40 mm, hereafter referred to as SPM-G, pose considerable challenges for resilient modulus (RM) testing because their maximum particle size exceeds the capacity of conventional laboratory specimens. However, the RM is an essential parameter for the structural design of underground-cavity backfills and road subgrades. To address this limitation, this study developed a numerical simulation method for RM evaluation (NSM-RM) by integrating X-ray computed tomography imaging with discrete element modeling. The method was first evaluated by comparison with laboratory test results, with deviations within 2.5 %. It was then applied to investigate the effects of the soil-to-pebble mass ratio, the proportion of particles larger than 40 mm, and the maximum particle size (Dmax) on the RM of SPM-G. Within the investigated ranges, the RM generally increased with increasing pebble content, proportion of particles larger than 40 mm, and Dmax. Based on the combined laboratory and numerical results, an RM prediction model and corresponding evaluation procedure were established. A preliminary field evaluation using six measurement points from two road sections yielded a maximum deviation of 4.6 % between the predicted and measured values. These results demonstrate the feasibility of NSM-RM for estimating the RM of SPM-G when conventional laboratory testing is constrained by specimen-size requirements.