Abstract: By analyzing the progressive evolution of particle crushing of crushable soils, four basic properties of particle crushing are presented, and three characteristic states are also given over long-term or repeated loading. Two breakage indexes, namely the global and or breakage index, are defined for the crushable soils to distinguish temporary stop from perpetual termination of particle crushing, and a mathematical relationship is put forward between the revised relative breakage and the grading index. A series of consolidated drained large-scale triaxial tests are conducted for the coarse-grained materials (CGMs). The evolution of particle grading and breakage is analyzed, and some mathematical formulations are presented for various breakage indexes, which exhibits a entire rule of particle crushing of CGMs under the monotonic loads: (1) The global breakage has a negative exponential increase with the non-moralized deviatoric stress and the mean principal stress upon shearing. (2) At the end of consolidation or in the critical state, it increases merely with the non-moralized mean principal stress which meets the above-mentioned negative exponential function. (3) The local breakage varies with the stress level in a way of hyperbolic function and approaches 1 in the critical state.