The relationship between the electrical resistivity and saturation of unsaturated soil

Comparing with the saturated soils, the unsaturated soil, which composed of soil particles, water and air, display more complex properties due to negative pore water pressure. Recently, the interest in introducing electrical resistivity measurement to measure the properties of soil has increased markedly. This work aims to apply a digital multimeter to measure the electrical resistivity of unsaturated soil, and to analyze deeply the effects of saturation on the resistivity. In this paper, a digital multimeter and a homemade insulated model were used to measure electrical resistivity of unsaturated sand, loess and clay. Based on analysis of test data, an equation about the electrical resistivity and saturation is proposed, a power function that the electrical resistivity decreases with the increase of saturation and then tends to be a constant. The researchers indicated the main reasons that cause the different variation law of electrical resistivity of soil. (1) The pore water leads to the variation law of soil electrical resistivity. (2) That electrical resistivity of the sand is far greater than that of the loess and clay is attributed to mineral compositions, particle arrangement and internal impurities. (3) The soil particle distribution also affected the electrical resistivity. © 2014 ejge.