Preliminary study on the contribution of osmotic effects for the electrical resistivity of sands

¹ IST, Universidade de Lisboa. , Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal
² INESC-MN, R Alves Redol, 9, 1000-029, Lisboa, Portugal
³ KLS Gogte Institute of Technology, Belagavi, 590008, India
⁴ CERIS, Av. Rovisco Pais, 1 1049-001, Lisbon, Portugal

^* e-mail: rafaela@civil.ist.utl.pt

Abstract

Electrical resistivity of soils can be used to evaluate the level of contamination in soils in geophysical prospection tests. The chemical composition of pore fluid also corresponds to a given water potential, named as osmotic suction. Therefore both electrical resistivity and osmotic suction can be related when soil is saturated. This paper investigates their relationship when the soil is not saturated. The osmotic suction and electrical resistivity were measured for uniform grading size samples of sand prepared with different concentrations of an ionic leachate from a real landfield. Both were measured also for the fluid with the different concentrations. Suction was measured for different degrees of saturation using the ionic fluid for the different concentrations. The soil osmotic suction is similar to the osmotic suction of the pore fluid independently from the degree of saturation, and the differences in electrical resistivity in the saturated samples and pore fluid alone as function of osmotic suction are related by a constant. Although pore fluid composition affects electrical resistivity, when evaluating the electrical resistivity considering the degree of saturation one should pay attention to factors that are related with matric suction instead of osmotic suction.