Granular thermodynamic exploration on the shear-band formation process of crushable coarse-grained soil

A thermodynamic constitutive law is constructed for crushable coarse-grained soils, which elucidates the shear-band formation mechanism governed by particle breakage. The model introduces granular temperature/entropy as mesoscopic state variables and incorporates a structural strength parameter into the elastic potential energy density function to dynamically capture the particle breakage effect. Meanwhile, a quantitative relationship is established between fragmentation index and critical-state parameter, while the dilatancy equation is modified by incorporating particle breakage energy, enabling a unified framework to describe the coupled evolution of particle breakage, shear dilatancy/shrinkage, and shear-strength. Validated by uniaxial compression and triaxial shear tests, the model demonstrates improved predictive accuracy for the compressibility and shear response of coarse-grained soils. Finite element simulations further reveal the evolution law of shear-band accompanying particle breakage. Moreover, the parametric sensitivity analysis (initial stiffness parameter, elastic bulk modulus, confining pressure, and specimen geometry) elucidates the key regulatory mechanism governing the geometric characteristics (localization degree, dispersion, and structural configuration) of shear-band.