Strength and dilatancy of crushable soils with different gradings

Peak strength and dilatancy of granular materials generally decrease with increasing mean effective stress, and such a decrease will be enhanced due to the occurrence of particle breakage. This paper presents a simple empirical approach to modify Bolton’s original strength and dilatancy equation for crushable soils with different crushability. The proposed approach is based on data of a series of drained triaxial tests on carbonate soils with five different particle size distributions and three initial relative densities. It is also validated against other published experimental data on various crushable soils, including carbonate soils, limestones, coarse aggregates, and silica sands. The modified relation retains a similar form to Bolton’s equation with only one additional parameter introduced. As a result, the crushing strength-related parameter in the original relation is modified to incorporate the impacts of particle shape, gradings, and mineralogy on particle breakage. This modified parameter tends to increase as soil crushability decreases, which keeps a similar physical meaning to Bolton’s crushing strength-related parameter, and is suitable for a wider range of crushable soils with different gradings. The proposed strength and dilatancy equation for crushable soils yields to Bolton’s equation for strong soil particles where particle breakage is negligible.