Correction of Wall Adhesion Effects in Batch Settling of Strong Colloidal Gels

TL;DR

This paper introduces a simplified 1D model to correct wall adhesion effects in batch settling tests of strong colloidal gels, enabling more accurate estimation of rheological properties despite measurement errors.

Contribution

A highly simplified 1D visco-plastic approximation of the complex hyper-elastic model is developed, allowing analytical solutions and robust parameter estimation.

Findings

Analytical expressions for equilibrium solids concentration and bed height.

Improved accuracy in estimating yield strength and adhesion from experimental data.

Method reduces complexity and enhances robustness against measurement errors.

Abstract

The batch settling test is widely used to estimate the compressive rheology of strongly flocculated colloidal suspensions, in particular the compressive yield strength and hydraulic permeability. Recently it has been discovered that wall adhesion effects in these tests may be significantly greater than previously appreciated, which can introduce unbounded errors in the estimation of these rheological functions. Whilst a methodology to solve the underlying static problem and correct for wall adhesion effects has been developed, this method is quite complex and unwieldy, involving solution of a 2D hyper-elastic constitutive model for strong colloidal gels. In this paper we develop a highly simplified 1D visco-plastic approximation to the hyper-elastic model which admits analytic expressions for the equilibrium solids concentration profile and bed height. These expressions facilitate robust estimation of the compressive yield and wall adhesion strength via nonlinear regression of experimental data in the presence of small measurement errors.