Elastic-Viscoplastic Modeling for Natural Soft Clays Considering Nonlinear Creep

This paper focuses on nonlinear creep behavior with a consecutively decreasing creep coefficient C-alpha e fully related to the soil density. Conventional oedometer tests on reconstituted samples of several natural soft clays are selected to clarify the evolution of creep coefficient throughout testing. On this basis, a simple nonlinear creep formulation is proposed accounting for the effect of volumetric packing of soil assemblies. The formulation is then incorporated into a newly developed elastic-viscoplastic model to take into account the nonlinear creep of natural soft clays. One additional parameter is added that can be determined in a straightforward way from an oedometer test without additional experimental cost. The enhanced nonlinear creep model is examined by simulating a conventional oedometer test on reconstituted Haarajoki clay. The improvement of predictions by the nonlinear creep formulation is highlighted by comparing predictions with constant C-alpha e. The enhanced model is further applied to Murro test embankment. The influence of consideration of nonlinear creep on the embankment behavior is discussed. (C) 2014 American Society of Civil Engineers.