Macro- and micro-mechanical characteristics of crushed rock aggregate subjected to direct shearing

To study the mechanical behavior of crushed rock aggregate, a series of large-scale direct shear tests were conducted. Then the particle flow model was established with PFC3D (Particle Flow Code 3D) to analyze the micro-mechanical properties, including the distribution of contact forces and displacement vectors. The clump logic was adopted to replace the spheres to simulate the irregular particle. The main results were: The shear strength of crushed rock aggregate increased obviously with the increase of normal stress, and a strength envelope of the power function type was suitable for assessing this; within the range of chosen normal stresses, volumetric dilation was always observed after compression, and smaller normal stress led to larger dilation as well as a less amount of compression; within certain particle sizes, the shear strength at the same normal stress and compression displacement increased with increasing particle size, while the apparent friction angle showed an opposite trend; and the formation of the shear band and evolution of the volumetric strain were elucidated.