Geotechnical-Electrical Evaluation of Soil Compaction Parameters, South of Baqubah City

Abstract

Soil compaction is fundamental for improving the geotechnical properties of a wide range of engineering structures. Evaluation of compaction parameters is crucial for maintaining the long-term performance of these structures. In this study, geotechnical-electrical relationships were adopted to evaluate the compaction parameters of soil south of Baqubah City. Forty-seven soil specimens, collected from eight locations, were prepared and compacted at various conditions that can be found in the geotechnical practice. First, laboratory tests such as sieve analysis, liquid limit, and plastic limit were carried out to characterize and classify the soil based on USCS classification. Second, the specimens were prepared in the lab using different moisture content, dry density, and compaction efforts. Electrical resistivity measurements were then conducted on compacted specimens using Kangda KD2571B2 instrument. All laboratory tests were performed based on ASTM standards. The results revealed that the soil at the site is fine-grained type CL of medium plasticity clay with sand. Optimum Moisture Content OMC and Maximum Dry Density MDD were, respectively, 14.72% and 1.83 g/cm3 for the Standard Proctor compaction test; and 11.08% and 1.90 g/cm3 for the Modified Proctor compaction test. Geotechnical-electrical relationships achieved showed that soil resistivity is strongly influenced by the main compaction parameters; moisture content, dry density, and compaction energy, particularly at low moisture content. A high correlation coefficient (R2 > 0.98) was achieved for the resistivity-degree of saturation and resistivity-volumetric moisture content relationships. These correlations were validated with R2 (0.896-0.934) between the measured and predicted data, which indicates the advantages of adopting the resistivity method as a complementary tool for the preliminary site investigation.