In this paper, an elasto-viscoplastic constitutive model is proposed to predict the one-dimensional consolidation behavior of natural soft elay deposits. In order to describe the yielding and time dependent behavior of natural clays the proposed model is derived being based on the flow surface theory of viscoplastisity and the concept of internal state variable. The applicability of the model is examined by comparing calculated results with laboratory behavior of natural days, and it is confirmed that dependence of both time-loding history and strain rate on the consolidation yielding behavior of natural days can be expressed by the proposed flow surface history variable model.
Clay behavior under compression has always been a topic in geotedmical engineering. Recently, in connection with coastal development, the consolidation yielding characteristics of pseudooverconsolidated clays or lightly overconsolidated clays have become of major interest. On the other hand, the influence of time-loading history and strain rate on the compressibility of natural clays has been evidenced-based on laboratory experiments by many researchers. Therefore, in order to predict the consolidation behavior of natural soft clay deposits realistically, has to be developed the elastoviscoplastic constitutive model that can describe dependence of both time-loading history and strain rate. In the following sections, first the elasto-viscoplastic model for natural clays is proposed, being based on the flow surface theory and the concept of internal state variable. And then the applicability of the proposed model is examined through numerical simulations for laboratory behavior of natural days. It is also demonstrated that the proposed flow surface history variable model (FSHVmodel) can explain consistently the consolidation tests conducted by Aboshi (1973). Finally, it is shown that the time-loading history and the strain rate are essential factors controlling the consolidation behavior of natural days.
