Particle Breakage and the Undrained Shear Behavior of Sands

This article presents particle breakage and the undrained shear behavior of sands, with the purpose of interpreting the undrained shear behavior of the precrushed sands by detecting the influence of particle breakage on the basis of the contractive stage, the dilative stage, and the whole shear stage of sand behavior. Particle breakage resulted in impairment of the dilatancy behavior of sand (or intensification of the contractancy behavior of sand) in influencing the stress–strain behavior of sand with intensification of the excess pore-water pressure. Under the same initial void ratio, the critical state was characterized by a reduction of the mean effective stress with increasing particle breakage in the e-logp′ plane. In view of all critical states on the same particle breakage, particle breakage resulted in the translation and rotation of the critical state line in the e-logp′ plane, but the critical state followed and evolved downward along the two-segment critical state line in the q–p′ plane with increasing particle breakage. In the q–p′ plane, particle breakage had an insignificant influence on the phase transformation line, but the phase transformation state evolved downward along the phase transformation line with increasing particle breakage. During each shear stage (the contractive stage, the dilative stage, or the whole shear stage), particle breakage resulted in movement of the confining-pressure normalized loci of the delta excess pore-water pressure ($\Delta u$) and delta deviator stress ($\Delta q$) $(\Delta u–\Delta q)$ and the delta excess pore-water pressure (Δu) and delta mean effective stress (${\Delta p}^{\prime }$) ($\Delta u$–${\Delta p}^{\prime })$ toward and then along a linear reference line with an increase of the normalized delta excess pore-water pressure and a decrease of the normalized delta deviator stress and the normalized delta mean effective stress with increasing particle breakage. In addition, the divergence from the linear reference line was revealed to decrease and even vanish with increasing confining pressure.