Scale effect of rockfill materials using super-large triaxial tests

A super-large triaxial apparatus and a common large triaxial apparatus are used to conduct triaxial tests on quarried rockfill materials with the maximum particle size d_max of 200 and 60 mm in parallel gradation. The study mainly focuses on the effect of particle size on the stress-strain relation, particle breakage, characteristic stress state and parameters of Duncan-Chang model. The results show that the peak friction angle of d_max=60 mm is higher than that of the d_max=200 mm, and the axial stain at the peak strength of d_max=60mm is smaller than that at d_max=200 mm. The phase transformation stress ratio of d_max=60 mm is higher than that at d_max=200 mm, and the volumetric and axial strains in phase transformation state are smaller than those at d_max=200 mm. The amount of particle breakage of d_max=200 mm is greater than that at d_max=60 mm. The secant elastic and bulk moduli at 50% stress level of d_max=60 mm are larger than those at d_max=200 mm. The parameters k and k_b of Duncan-Chang model for d_max=60 mm are 1.22 and 1.38 times those for d_max=200 mm, respectively. This study may provide valuable experimental references for the constitutive model considering scale effect and the deformation analysis for rockfill structures.