Prediction of effective porosity of contaminated fine grained soils using electrical properties

The effective porosity is a required parameter for mass flow rate calculations in groundwater hydrogeology and movement of contaminants through clay liners. It is also an important soil parameter in geotechnical engineering. In this manuscript, a laboratory methodology based on electrical properties of soils is proposed to estimate the effective porosity of contaminated soils. Based on the cluster model proposed by Olsen 1962 and the three possible electrical current paths through soils, a three-element electrical model is proposed. Bulk electrical properties of a soil element were mathematically derived for input frequencies of 1-100 MHz. The bulk electrical properties of three soils at different confining pressures in both horizontal and vertical directions were measured for the said frequency range. The measured and the predicted bulk electrical properties of soil were compared; the predictions were used to establish effective porosity of the soil element. The predicted effective porosity values for three soils under different chemical environments were compared with those measured using tracer test. The comparisons show that electrical measurements could predict effective porosities of contaminated fine grained soils. These measurements can then be used to estimate in situ effective porosities, to be used in contaminant transport models.