Abstract: Using Rowe’s stress dilatancy equation to considering the influence of particle breakage energy is a main method to express the dilatancy property of coarse-grained soils. However, the calculated breakage energy may be decreased during shearing or even be negative, which violates the irreversible thermodynamic theory. The reason lies in the friction factor, namely the critical state stress ratio Mc, is too larger during the entire shearing process. The breakage energy was closely relate with the evolution of particle breakage. An equation was proposed to express the relationship between the particle breakage factor and stress/strain state. A reduction scheme was suggested to replace the Mc by a new friction factor M. The newly calculated breakage energy proved to increase during shearing and approach to a stable value, which is reasonable and in accordance with the evolution of particle breakage. Then, the remaining unknown parameter dEb/pdεs of the dilatancy equation obtained by consolidated drained triaxial test was found to show a significant linear relationship with M. Therefore, the dilatancy equation was finally determined and verified by a series of test data from different rockfills.

Key words: coarse-grained soil, particle breakage, breakage energy, stress dilatancy, critical state