Advancements to the Generalised Clay Disaggregation Model

PhD Thesis

Redmond, Thomas William. 2023. Advancements to the Generalised Clay Disaggregation Model. PhD Thesis Doctor of Philosophy. University of Southern Queensland.

Advancements to the Generalised Clay Disaggregation Model

TypePhD Thesis
AuthorsRedmond, Thomas William
1. FirstDr Yingcan Zhu
2. SecondDr Stirling Roberton
2. SecondA/Pr David Freebairn
Institution of OriginUniversity of Southern Queensland
Qualification NameDoctor of Philosophy
Number of Pages198
PublisherUniversity of Southern Queensland
Place of PublicationAustralia
Digital Object Identifier (DOI)

This thesis documents modifications and improvements to the McNeal-Ezlit Generalised Clay Disaggregation (GCD) model. This semiempirical model provides soil specific predictions of soil behavioural response to water quality, quantified by measurement of the saturated hydraulic conductivity (KS). The aim was to identify limitations and shortcomings currently present in the model, and to modify or propose improvements to the model. Concretely, this thesis provides a simplification of the underlying model equation which is evaluated on 26 soils for which the fitted parameters of the model have previously been published. It is shown that this improves overall transparency and interpretability of the model without significant modification to the model outputs. The present algorithm for transforming measured KS data to fit to the model is evaluated and shown to be flawed. Alternatives are investigated and a revised method using a single reference datum per soil data set is proposed. The GCD model does not presently account for variability as part of its measurement process. A novel method of z-score normalisation of pre-treatment data is proposed to estimate soil-packing related variability in the model. In undertaking this evaluation, the validity of the method by which conductivity measurements are made for fitting this model is questioned with respect to the concentration of pretreatment, and equilibrium conditions for obtaining suitable measurement data. The improved GCD model is then tested for its ability to compare two soils or distinct soil conditions for site comparison or change measurement. It is shown that there is no mechanism within the model to make direct comparisons between two soils or soil states, and alternatives are proposed and demonstrated in a preliminary sense. Through doing so it is found that salt-dominated soil behavioural responses patterns described by the GCD are dynamic and not static properties.

KeywordsIrrigation, Salinity, Sodicity, disaggregation, Clay swelling
Contains Sensitive ContentDoes not contain sensitive content
ANZSRC Field of Research 20203002. Agriculture, land and farm management
370401. Computational modelling and simulation in earth sciences
401106. Waste management, reduction, reuse and recycling
Public Notes

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Byline AffiliationsCentre for Sustainable Agricultural Systems
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