Four electrode resistivity probe for porosity evaluation

The objective of this study is to develop and verify a four electrode resistivity probe (4ERP) for the estimation of electrical properties of saturated soils without polarization at the electrodes. The 4ERP design is categorized by two types: wedge and plane. The wedge type is used for penetrating into the soil samples and the plane type is used for installing into experimental cells such as an oedometer cell. Consolidation tests are carried out on six different sized glass beads. The test results reveal that the shape factor, m, used in Archie's law, is about 1.19 for glass beads. One-dimensional liquefaction tests show that the porosity obtained by the 4ERP is similar to the porosity determined by volume fraction. The porosity profile obtained by the penetration of the 4ERP into the large-scale calibration chamber in the clay-sand mixture is similar to the volume based porosity. Furthermore, the porosity profile estimated by the resistivity is almost the same as the volume based porosity in glass beads. This study demonstrates that the 4ERP may effectively estimate the porosity of saturated soils.