Effect of particle size on small strain stiffness of biotreated sands

Particle size is critical for the engineering behavior of sand. For biocemented sand, the studies concerning particle size and small strain stiffness are rare. In this study, particle size is seen as the main grain characteristic contributing to the change of small strain shear modulus Gmax. Isotropic consolidation tests with shear wave velocity measurement were performed to investigate Gmax and Gmax anisotropy of biocemented sand. The test results showed that for the uncemented sands, Gmax increases with the increase of particle size. The constants n and A in Hardin equation decrease and increase with the increase of particle size, respectively, when D50 is larger than around 1.5 mm. For biocemented sand, biocementation is more effective for the sands with smaller diameters. For smaller grain sizes, the contribution of stress increase to stiffness increment is higher than that of biocementation. For coarse sand, biocementation could inhibit the stiffness increase induced by stress increase and at a higher stress level, Gmax of uncemented sand is even higher than that of the biocemented sand. Particle size has no impact on the small strain stiffness anisotropy of uncemented and biocemented sand for the rounded glass beads.