Correlations between Geotechnical Parameters and Electrical Resistivity for Limestone at Beni Suef, Egypt

Gihan E. Abdelrahman, Professor of Soil Mechanics and Foundation Engineering, Civil Engineering Department, Faculty of Engineering, Fayoum University, EgyptFollow
Elsayed A. Issawy, Professor of Applied Geophysics Director of Aswan Regional Earthquake Research Center, National Research Institute of Astronomy and Geophysics, Helwan, EgyptFollow
Walid I. Hammad, Associate Professor of Soil Mechanics and Foundation Engineering, Civil Engineering Department, Faculty of Engineering - Fayoum University, EgyptFollow
Ahmed A. Moheb, PhD Student Faculty of Engineering, Fayoum University, Egypt AND Associate Researcher of National Research Institute of Astronomy and Geophysics, HelwanFollow

Abstract

This study presents an integrated geotechnical–geophysical investigation of limestone formations in Ezbet Deir El-Hadid, Egypt. The research combines conventional geotechnical testing with two-dimensional (2D) electrical resistivity tomography (ERT) to develop a cost-effective subsurface characterization methodology. Forty-one boreholes (15–30 m depth) provided direct measurements of unconfined compressive strength (q_u) and rock quality designation (RQD), while twenty-five ERT profiles enabled spatial resistivity mapping. Three distinct geological conditions were identified: (1) intact limestone exhibiting resistivity of 21–602 Ω·m, (2) water-saturated zones with reduced resistivity (14–37 Ω·m), and (3) cavities showing higher resistivity (1,038–4,035 Ω·m). An optimized investigation protocol used a Wenner–Schlumberger array with 5 m electrode spacing across multiple 2D profiles, with depth-matched confirmatory boreholes (BH1–BH41). Within a calibrated resistivity range, statistically significant, monotonic relationships between resistivity and rock-mass indicators (RQD and unconfined compressive strength, q_u) were established, enabling quantitative cross-validation of geophysical imaging with geotechnical observations. The integrated approach reduced investigation costs by 30–40% while maintaining engineering reliability, offering practical benefits for landslide hazard assessment in carbonate terrains, infrastructure foundation design, and geohazard mitigation. The results delineate the geometry of competent limestone, water-affected or fractured zones, and localized cavities, consistent with borehole stratigraphy, and demonstrate the value of coordinated 2D ERT and borehole programs for robust site characterization and decision support.

Keywords

Limestone, Unconfined compressive strength, Rock quality designation (RQD), Electrical resistivity tomography (ERT)

Recommended Citation

Abdelrahman, Gihan E.; Issawy, Elsayed A.; Hammad, Walid I.; and Moheb, Ahmed A. (2026) "Correlations between Geotechnical Parameters and Electrical Resistivity for Limestone at Beni Suef, Egypt," HBRC Journal: Vol. 22: Iss. 1, Article 10.
Available at: https://journal.hbrc.edu.eg/journal/vol22/iss1/10