oa Investigating the Deformational and Microstructural Changes in Unconsolidated Earth Materials using Complex Resistivity Measurements

Micro-structural modifications of near surface earth materials influence their geotechnical engineering behavior and stability conditions. the ability to characterize and monitor these modification non-invasively using geophysical techniques would be useful in geotechnical engineering Investigations. in this study, we conduct controlled laboratory experiments on sand-clay mixtures subjected to external loading and concurrently measure their deformational characteristics and frequency-dependent electrical resistivity (complex resistivity). the experimental setup consists of a modified oedometer with outlets for sample vacuuming, saturation and drainage, and is also fitted with pore pressure transducer, strain gauge and electrodes for electrical measurements. the samples are placed in the oedometer and saturated with water beyond their liquid limits and each subjected to an axial stress of 500kPa. the experiment is conducted under controlled drainage which allows measurements of changes in sample pore pressure and volume of water drained. At each effective stress level, the complex resistivity of the sample is measured over a frequency range (0.5Hz – 512Hz). the results show that electrical parameters obtained from the electrical response measurements are sensitive to the characteristic micro-structural changes occurring in the soil during the consolidation process. the relationship between the electrical parameters (resistivity amplitude, phase, capacitance, loss tangent) and the deformational and hydraulic parameters including axial strain, coefficient of compressibility, void ratio, dry density, pore size and hydraulic conductivity, influences the engineering properties and behavior of earth materials are also investigated. This study provides a good understanding of how changing state of soil and deformational characteristics can be predicted from electrical response measurements. the results will be useful in the use of geo-electrical methods in engineering, environmental and geohazard Investigations.