Void Ratio Estimation of Soft Soils Using Electrical Resistivity Cone Probe

Electrical properties of soils have commonly been used to estimate geotechnical properties. This paper introduces a new device, an electrical resistivity cone probe (ERCP), to determine the electrical resistivity of seashore soft soils and estimate void ratio in the field. The probe consists of inner and outer electrodes with a coaxial structure. The probe tip is conical to minimize disturbance during penetration. A four-terminal pair configuration is used to prevent electrical interference. The electrical resistance is measured during a consolidation test, penetration tests in a large-scale calibration chamber, and at two field sites. With the resistivity of soils and electrical resistivity of pore water extracted from undisturbed soils, the void ratio is estimated using Archie’s law. The void ratio estimated by the ERCP in an oedometer cell is almost the same as the volumetric void ratio of sand determined from consolidation tests. In addition, the void ratio profile obtained by the ERCP agrees well with the volume-based void ratio in a sand-clay mixture prepared in the calibration chamber. The void ratio profile estimated in the field is inversely proportional to the standard penetration testing N-value and the cone-tip resistance of the cone penetration test. This paper demonstrates that the ERCP may be an effective device for the estimation of the void ratio of seashore soft soils.