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The influences of particle breakage on the position of the critical state line (CSL) were systematically investigated in this paper through a series of large-scale triaxial compression tests on Tacheng rockfill material (TRM). It was found that the critical-state stress ratio of TRM (i.e., the gradient of the CSL in the p - q space) was approximately regarded as a constant. In the e - log p space, the CSL of TRM descended with a decrease in the initial void ratio, whereas the gradient of the CSL was constant. A procedure was established for evaluating the critical state point at a same particle breakage, which comprised the breakage critical state line (BCSL). An increase of the particle breakage led to not only a vertical translation but also a rotation on the BCSL of TRM in the e - log p space, which was similar to the observation of Dog's Bay sand. Consequently, the initial gradation (or the corresponding initial void ratio) was the dominant factor that affected the position of the CSL of TRM in the e - log p space. [ABSTRACT FROM AUTHOR]

A series of large-scale triaxial compression tests on Tacheng rockfill material (TRM) showed that the dilatancy and stress-strain behaviors were significantly influenced by density and pressure. The critical state friction angle ofTRM decreased with an increase in the initial confining pressure. In addition, the critical state line of this material in the e-log p9 plane ascended with an increase in the initial void ratio. On the basis of the specific critical state behaviors of TRM, a state-dependent constitutive model was slightly adapted in the triaxial stress space. The model, with only a set of model parameters, could capture the state-dependent behaviors of the dilatancy, stress-strain, and mobilized friction angle of TRM at various densities and pressures. The peak friction angle of TRM was found to be linear, with a coefficient of 0.21, in relation to the maximum dilatancy angle. The coefficient for rockfill materials was smaller than that for sands, indicating that the influence of dilatancy on the strength for sands was more pronounced than that for rockfill materials. [ABSTRACT FROM AUTHOR]