Strain-rate change effects in reconstituted London clay using a viscoplastic subloading model

This paper illustrates the capability of a viscoplastic subloading model recently proposed in reproducing strain-rate change effects in soil. The viscoplastic model used is based on the subloading surface concept making possible the occurrence of viscoplastic strains inside the yield surface. After a brief description of the basic principles and constitutive relations behind the model, a numerical simulation of an undrained triaxial compression test on a normally consolidated reconstituted London clay with several strain-rate changes was performed with success. This result was obtained with a general soil model which did not take into account these specific temporary effects in its formulation. The influence of the strain-acceleration during the strain-rate transitions on the model's response was also analysed. The temporary effects were found to be influenced by the value of the strain-acceleration. However, for the values normally used in the laboratory tests, the temporary effects seem to be insensitive to it.