Prediction of nonlinear viscoelastic behaviour of simulative soil for deep-sea sediment using a thermodynamically compatible model

This work focuses on the development of a suitable theoretical model for defining the nonlinear viscoelastic behaviour of deep-seabed sediments. To that end, shear rheological tests are performed on simulative soil samples at different shear rates. These samples are prepared by mixing bentonite with water based on the in situ vane shear strength of deep-sea sediments. A nonlinear viscoelastic fluid model based on a thermodynamic standpoint is derived by considering two scalar functions. The two scalar functions, namely, the stored energy and the rate of dissipation are found using the nonlinear response of the samples collected from experiments. This novel approach identifies the model parameters having physical significance and has considerable advantages over previous models which are predominantly empirical. This is carried out as an inverse problem in which the parameters are estimated by minimizing the deviation between the predicted and measured torque response of the sample when subjected to shear rheometry with the shear rate as the input. The efficacy of the model has been investigated and reasonable agreement with the peak as well as steady-state values of torque is observed.