A non-linear viscoelastic model for sediments flocculated in the presence of seawater salts

A new empirical three-parameter viscoelastic model is proposed for describing the rheological behavior of linear and nonlinear materials. In particular, the model succesfully reproduced experimental creep curves at various constant stresses for flocculated suspensions of alumina in the presence of different types of seawater salts. The new model is compared to the classical standard linear solid model and to an extension of this, also proposed here, to represent nonlinear materials. Based on the goodness of fit, the new model is found to be the most appropriate for the experimental system studied. A sensitivity analysis of the parameters to applied stress and type of salt in the sediments reveals that the new model, originally proposed as an ansatz, has three components, constant, linear and nonlinear, as inferred from the behaviour of each model parameter with the applied stresses. The linear contribution follows a correlation with the applied stresses for salts that enhance the hydrogen network of water, so called maker salts, and another for the salts that weaken the network, so called breaker salts. Even more interesting, the nonlinear contribution is characterized by large exponential decay lengths for breaker salts and small exponential decay lengths for maker salts. The existence of linear and nonlinear components may enable applying the model to a variety of systems. (C) 2015 Elsevier B.V. All rights reserved.