Stiffness evaluation of coarse unbound granular materials using large-scale repeated load triaxial test

This research investigates the effect of downscaling coarse unbound granular material (UGM) for characterization of the resilient modulus with large-scale repeated load triaxial testing. Four open-graded and two dense- graded materials are downscaled based on the particle size distribution curve and upper sieve size for subbase materials of crushed rock (CR) 22/125 mm and CR 0/125 mm as defined by the Norwegian road design regulation. The results were evaluated using the K-theta model and Uzan's model. The findings for CR 4/22 mm, CR 6/32 mm, CR 8/45 mm, and CR 11/63 mm indicate that downscaling of coarse open-graded UGMs could be applicable for characterization of the resilient modulus. The results for dense-graded UGMs CR 0/22 mm and CR 0/63 mm indicate that downscaling reduces the resilient modulus. Further research should include complementary gradings and rock types.