Changes in the electrical resistivity of arid soils during oedometer testing

Electrical methods used in geotechnical engineering are considered to be potentially useful for characterising soil settlement. In this study, a standard American Society for Testing and Materials oedometer was specifically designed for measuring the electrical resistivity of soils during oedometer testing. Relationships between the electrical resistivity and soil settlement were established for three remolded samples of saturated soils collected from the Yazd University (Iran) test site. The low resistivity values (less than 3m) measured during the oedometer tests were correlated with the high-salinity solutions in the pores (i.e. interstitial brine) that are typically observed in arid soils. In contrast to similar studies conducted in silty and clayey soils collected from areas with a moderate climate, our results have shown for the first time that the resistivity of the soil increases with increasing soil settlement and for loadings greater than 24.43kPa. This increase was more pronounced for the soil with the highest evaporite minerals content, which reveals the strong effect of chemical reactions between the percolating brine and the solid skeleton. The increase in resistivity during settlement was interpreted as resulting from the crystallisation of evaporite salts from the interstitial brine that was induced by the decrease in brine solubility during drainage.