Exploring the linkages between geotechnical properties and electrical responses of sand-clay mixtures under varying effective stress levels

The strength and stability conditions of unconsolidated geo-materials, for example soils, are influenced by modifications of their micro-structure, texture, mineralogy and effective stress levels. These modifications in the internal structures of the soils often result in geohazards (e.g., landslides, liquefaction, debris flow), which often claim so many lives, destroy the environment, and cause considerable amounts of property damage. Characterization and monitoring of such geohazards demand knowledge about the geotechnical (physical and mechanical) properties of unconsolidated near-surface geo-materials of interest. The fundamental relations between geo-electrical parameters and the geotechnical properties that influence the mechanical behavior of soils are investigated by performing controlled laboratory experiments on sand-clay mixtures under stress. Spectral electrical response (SER) measurements are performed on these mixtures over a range of frequencies (0.001 Hz-1 kHz) with concurrent measurements of their geotechnical properties. Electrical parameters, such as phase, resistivity amplitude, capacitance, and loss tangent, are extracted from the SER measurements, and geotechnical properties of the mixtures, which include void ratio, dry density, and the modulus of elasticity, are obtained from laboratory measurements. Cross-plots of geotechnical properties and geo-electrical parameters indicate significant correlations. The phase and capacitance values decrease with an increase in the dry density, whilst the loss tangent and the resistivity values increase with increase in dry density. The phase and capacitance values, however, decrease with an increase in the values of the modulus of elasticity, whereas the loss tangent and the resistivity values increase with increase in elastic modulus. These relations can be useful in non-invasive prediction of the physical, mechanical, and geotechnical properties of unconsolidated geo-materials relevant in the assessment, monitoring, and mitigation of geohazards.

Duke Scholars

Author Fred K. Boadu Civil and Environmental Engineering