Electrical resistivity tomography to check compaction control of road embankment made of partially saturated soil

Compaction control is essential in road embankment construction. Poor embankment compaction results in deteriorating stability of pavements and roads. While traditional bore log surveys can be used to assess compaction quality, they may miss isolated areas of poor compaction (soft pockets) due to the limited sampling points along a large embankment. Also, bore log can be cumbersome for extensive embankments. Non-invasive and non-destructive geophysical methods can provide a simple and economical alternative to predict the compaction quality of road embankments. This study investigates the efficacy of electric resistivity tomography (ERT) as a geophysical method, for predicting the degree of compaction (R_c) in a newly constructed embankment near Silchar City, India. Six ERT surveys were conducted at various stages of construction, and the resulting models successfully revealed anomalies associated with variations in soil compaction. To validate these findings, a comprehensive program of borehole and dynamic cone penetration testing (DCPT) was undertaken at multiple locations across the embankment. The investigation established a strong correlation between the electrical resistivity (ρ) of the soil and its compaction characteristics. A non-linear regression analysis was performed to quantify the relationship of ρ values with air content, void ratio, bulk density, dry density, degree of compaction (R_c), and DCPT cone resistance. This analysis yielded high regression coefficients, demonstrating the effectiveness of ERT for predicting the compaction state of road embankments.