Predicting Soil Strength using Electrical Resistivity Measurements in Clays

ABSTRACT: This paper presents an experimental study that investigates the effects of stress history and mineralogy on the use of electrical resistivity to predict soil strength. Recent experimental studies show that the electrical resistivity, ρ, is promising in predicting the undrained shear strength, Su, for a given soil type under the same conditions (e.g., pore fluid and stress history). When employing ρ in surveying seabed sediments, the effects of natural variability in the soil, such as different stress histories and mineral compositions, need to be addressed. This study utilizes a special-made triaxial setup that can measure the electrical resistance, R, at any stage of a consolidated undrained test on reconstituted clay samples, which is used to calculate the electrical resistivity of the clay samples. Multiple triaxial tests are performed on specimens of varying plasticity indices (PI) and stress histories (represented by the overconsolidation ratio, OCR). The results provide a correlation of Su relating to ρ, PI, and OCR, which is useful in geotechnical engineering applications where the determination of soil strength using geophysical methods is an option.