INFLUENCE OF WATER CONTENT ON THE ELECTRICAL CONDUCTIVITY OF PEAT

Abstract

Organic layers are heterogeneous in space and their composition changes over time. This poses challenges to ecohydrologists, subsurface hydrologists, and ground engineers to characterize subsurface peat structures and to predict their behavior over time. A better characterization of peat deposits in terms of hydraulic properties can be achieved by performing multifrequency elect rical surveys provided the complex conductivity of peat is understood and connected to its index and geomecha nical properties.For this purpose, the relationship between water content, porefluid conductivity and the bulk conductivity of peat was investigated using a PVC compression cell equipped with two couples of electrodes placed at the top and bottom of the sample. This setup allows measurements of electrical resistivity and induced polarization at different levels of compression, and thus water contents, of the peat. Broadband frequency measurements (10 �1 to 10 6 Hz) of complex electrical conductivity were carried out on peat samples saturated with water at different salinity in the range 0.001 to 1 S/m. The results were interpreted with an empirical model which shows a positive correlation between water content and the peat conductivity when the porefluid conductivity is higher than the cond uctivity of the solid material, whereas the correlation is found to be negative when the porefluid conductivity is lower than the conductivity of the solid material. The results indicate that the water content of peat can be predicted by lowfrequency electrical measurement when the value of the porefluid conductivity is known. This study presents results that can provide a better understanding of the lowfrequency electrical properties of organic soil s.