Particle Breakage Energy in Coarse-Grained Soil and Its Effect on the Stress–Dilatancy Equation

The breakage of particles in coarse-grained soil consumes the strain energy stored within the particles, altering the original energy relationship during deformation and weakening the soil’s dilatancy. By studying the breakage energy of individual particles, the breakage energy of coarse-grained soil was calculated, leading to the establishment of a new stress–dilatancy equation. The single-particle breakage energy density (ud) is defined, and a method for determining ud is presented. Through statistical analysis of ud from 365 single-particle breakage tests across eight particle sizes, two key findings are drawn: (1) the optimal probability distribution for ud is the Weibull distribution, and (2) ud decreases as the particle size increases, with their relationship described by a power function. The statistical results for single-particle breakage strength (σb) align with those for ud. Based on these statistical conclusions for ud and σb, the breakage energy of coarse-grained soil was determined, with the evolution of particle gradation considered to ensure the accuracy of results. Finally, a new stress–dilatancy equation was proposed and validated using triaxial experimental data from two other types of rockfill. Mathematical analysis of an energy-balance equation revealed limitations in the soil friction coefficient expressions from previous studies, and the results from this paper further support this finding.