Laboratory Study of the Detection of Metal Contaminated Clay Layer Using Four-Electrode Resistivity Cone

Abstract

Electrical resistivity measurements provide potentially powerful tool for detection of heavy metal contaminated soil, which is on the rise in the whole world with the boost of industrialization and urbanization. A four-electrode resistivity cone penetrometer (RCPT) test (non-destructive, continuous, reliable, and demonstrates strong correlation with subsurface information such as soil properties, stratigraphy, and the location of anomalies) was used to detect metal contaminated soil layers in this study. To investigate the relationship between electrical resistivity and unsaturated subsurface conditions with varying physical property and metal contamination, the polluted clays were synthesized with controlled metal ions concentration and moisture content of loading in a chamber. A series of tests of polluted clay was performed and the mechanism of these tests were analyzed by electrical conduction theory. For all tested soils, the results show that increasing the degree of saturation and metal ions concentration on the clay led to a reduction in the electrical resistivity of clay, while increasing the porosity led to a higher electrical resistivity for the clay. It indicates that altering the porosity and saturation of polluted clay sample changed the ionic movement within the clay’s interlayer. In addition, data gotten by four-electrode soil resistivity box test was used to compare with the data measured from RCPT. The results showed that a linear approximation was sufficient in relating resistivity ρ_s of soil resistivity box to resistivity ρ_r of RCPT. In general, the RCPT was well used to examine the pollution of soil and the effects of remediation effectively in-suit.