Abstract: The purpose of this study is to present the development of a 1D elasto-viscoplastic (1DEVP) constitutive model to describe the time-dependent behavior of soft clays. Firstly, based on Bjerrum’s concept of time lines, a new concept of viscoplastic strain rate lines is proposed, and after the relationship between viscoplastic strain rate and viscoplastic strain increment is deduced, the 1DEVP model for soft clays is established. Secondly, the relationship between the newly developed model and other three well-known elasto-viscoplastic(EVP) constitutive models are theoretically discussed. It demonstrated that the new model with no essential difference from the other three EVP models is simpler in form and clearer in physical meaning than others. Thirdly, the established 1DEVP is used to develop analytical solutions for consolidation-creep coupling effect, strain rate effect, stress relaxation effect. Lastly, based the one-dimensional consolidation tests on Ningbo soft clays, the model parameters is calibrated. Furthermore, the model is used to simulate 1D consolidation-creep tests on Ningbo soft clays, 1D staged constant rates of strain tests on Wenzhou soft clays and 1D relaxation tests on Hongkong marine clays. The comparisons between experimental results and simulations show that the newly proposed 1DEVP model has a good predictive ability for the one-dimensional time-dependent behavior of soft clays.

Key words: soft clays, elasto-viscoplastic model, time-dependent behavior, consolidation, creep, strain rate effects, stress relaxation