Small-strain shear modulus of calcareous sand and its dependence on particle characteristics and gradation

The soil small-strain shear modulus, G0, is necessary for static and dynamic soil analyses and is often correlated to other soil properties such as density and void ratio, on their turn depending on gradation. The paper first presents a concise literature review of parameters influencing G0 in detail. Secondly, a particle shape analysis is performed. Silica sand is found much more spherical than calcareous sand, and calcareous sand becomes more spherical after crushing. Bender element test results indicate that not only uniformity coefficient (Cu) but also particle characteristics including particle shape and stiffness are very important to G0. G0 of calcareous sand is found higher than that of silica sand. Indeed, with less sphericity and more angularity, the variety of particle shape in calcareous sand produces a better fabric for shear wave propagation. For calcareous sand, the test results show that particle shape is the main factor affecting G0. Less dynamic stiffness is found for particles owning more sphericity and less angularity. The increase of Cu or finer particles (at low Cu) causes a decrease in G0. Finally, predictions of G0 for the tested calcareous sands using empirical equations from previous studies give very high relative errors (16.7-30%).