Effect of specimen size on quasi-elastic properties of Toyoura sand in hollow cylinder triaxial and torsional shear tests

Quasi-elastic deformation properties of dry, dense Toyoura sand were experimentally investigated by triaxial and torsional shear tests on hollow cylindrical specimens of medium sizes (outer diameter D-o=20 cm, inner diameter D-i=16 or, 12 cm, and height H=30 cm) and small size (D-o=10, D-j=6, H=20 cm). In addition to the conventional external measurements, strains were measured locally by the newly developed pin-type local deformation transducers. The effect of specimen size on locally measured Young's modulus E-z was insignificant. On the other hand, the locally measured values of shear modulus G(z theta) with the small size specimen revealed lower reproducibility as compared with those measured with the medium size specimens, suggesting that larger specimen size is preferred in evaluating the small strain shear modulus in torsional shear tests on hollow cylindrical specimens. It was also inferred from the test results that, irrespective of the specimen size, effect of end restraint at the top cap and pedestal is significant on the externally measured values of G(z theta).