Date of Award

2015

Degree Type

Thesis

Degree Name

Master of Engineering Science

School

School of Engineering

Faculty

Faculty of Health, Engineering and Science

First Advisor

Associate Professor Sanjay Kumar Shukla

Second Advisor

Professor Daryoush Habibi

Abstract

Liners are used in the engineered containment systems such as landfills for controlling the migration of contaminants. Although there are several techniques for detecting the leakages through the liners, use of the electrical resistivity method can assist in timely detection of contaminant migration in cost-effective manner. This method is based on the well-established fact that the electrical resistivity of soils and other geomaterials is much higher than the electrical resistivity of water, leachates or any liquid effluents which may permeate the landfill foundation material. Additionally, the geotechnical properties of a soil exhibit a close relationship with its electrical resistivity values for different conditions.

This thesis presents the results of investigation into the interaction between the various electrical factors pertaining to resistivity tests in Perth sandy soil (specifically AC-input voltage and frequency) and those controlling the soil characteristics, specifically water/fluid content and relative density of the soil, and the types of permeant employed in the tests, namely distilled water, tap water, three leachates and seawater. For a landfill system situated near a salt water body, the effects of seawater and seawater-leachate intrusion have also been scrutinized. For the measurement of electrical resistivity for different soil density and contamination conditions, the experimental apparatus was developed as per Australian standard AS 1289.4.4.1-1997 as a significant part of the thesis work.

The test results indicate that the resistivity of the sandy soil is almost independent of both AC-input voltage and frequency within the ranges used, while the choice of electrode material has an insignificant effect on the outcome of tests using this method. It is observed that the resistivity of sandy soil decreases rapidly with an increase in water/fluid content, but the rate of decrease reduces considerably for water contents over 12% in the case of distilled water and 10% for tap water, irrespective of the relative density. The resistivity is found to decrease almost linearly with an increase in relative density. However, the effect of relative density on the electrical resistivity of the soil is found to be negligible at higher water contents.

In the landfills and similar containment systems, there is a possibility of leakage of leachate across the liners and/or seawater intrusion, depending on the location of the landfills. Hence, the study was conducted to evaluate the effects of contamination on the electrical resistivity of the Perth soil by changing the fluid content with various combinations of tap water, three different leachates and seawater. The study shows that for any mix of leachate and tap water, the resistivity decreases rapidly with increasing fluid content; however, the rate of decrease reduces significantly for fluid contents over 9%, irrespective of the type of leachate. Almost the same trend is observed for the case of seawater.

Correlations between electrical resistivity, water content, relative density, amount and the composition of permeating fluid, which are applicable to the soil and permeating fluids used in the study, have also been developed and presented.

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