Influencing factors of scale effects in large-scale direct shear tests of soil-rock mixtures based on particle breakage

Abstract

In studies of soil-rock mixtures (SRM), scale effect due to limitations of particle size often causes laboratory research results to differ from on-site measurements. To explore the specific impacts of scale effect on the shear behaviours of SRM, large-scale laboratory direct shear tests and numerical simulations using the discrete element method (DEM) were thus performed. The accuracy of the numerical simulations was verified with a comparison of test and simulation results. The results suggest that scaling has only a minor influence on the shear stress–strain relationship of SRM, while Mixing Method was shown to be the optimum scaling method for studying shear behaviours in SRM under laboratory conditions. Based on this, a value of 0.9 times the shear strength of a relevant sample treated using the Mixing Method is suggested as the representative shear strength of actual scale SRM on site. There are some obvious differences in stone content and porosity factor in scaled samples treated by different scaling methods, however, which can lead to further dissimilarities in shear strength and other strength parameters under high normal pressure. In SRM more generally, the bulk shrinkage of the SRM samples is obvious during shear, and the shrinkage rate gradually decreases. The normal pressure and stone content have significant effects on the bulk shrinkage.