Evaluation of monotonic and dynamic shear modulus of sand using on-sample transducers in cyclic triaxial apparatus

This paper highlights the importance of the measurement of local strains in triaxial test using on-sample transducers. Specimens of sandy soil, prepared at two different relative densities (30% and 90%), were subjected to different effective confining stresses, and sheared monotonically as well as cyclically. Local strain measurements are obtained using Hall-type on-sample transducers attached at the mid-height of the specimen. The measurements from the on-sample transducers were further used to determine the modulus degradation curve for low-strain (less than 0.01%) to high-strain (greater than 1.0%) levels. Maximum shear modulus estimated from the cyclic tests is found to have an agreeable match with the same obtained from the monotonic tests corresponding to very low strains, as well as with those obtained from standard correlations. The experimental study indicates that for both monotonic and cyclic triaxial tests, the on-sample transducers can be effectively used to measure local strains in the soil specimen and evaluate the corresponding strain-dependent dynamic shear modulus.