Mudbanks of the Southwest Coast of India IV: Mud Viscoelastic Properties

Abstract

A small-strain rheological model has been developed to characterize the complex equivalent viscosity in the equation of mud motion due to water waves. The dynamic viscosity and the sheaf moduli of elasticity in this model are determined from creep and dynamic shear tests in a controlled-stress rheometer, and their dependence on the forcing stress amplitude frequency and the solids volume fraction is examined. For a comparative evaluation of mud rheology, the model has been applied to mud samples obtained from the southwest coast of India, Lake Okeechobee in Florida and Mobile Bay in Alabama, and to an aqueous clay mixture. In each case within the measured stress amplitude range, the viscoelastic coefficients are found to depend significantly on the forcing frequency for a given solids volume fraction.  The India mud is found to be the most viscous of those tested. This high viscosity results in very high rates of wave energy dissipation off the coast of Kerala during the monsoon season.