A Case Study of High-Resolution Gravity and Wenner-Schlumberger Resistivity for Geotechnical Engineering: An Example from North Jordan

During 2011, high-resolution gravity and Direct Current (DC) Wenner-Schlumberger resistivity geophysical techniques were made over an area of 80×70 m at the location of a proposed educational building at Jarash City, north Jordan. The objectives of the study were (i) to evaluate the resolution of these geophysical techniques in field work in detecting and locating anomalies caused by subsurface structures and (ii) to provide additional rock stratigraphy information at the site. High-resolution gravity data were collected on 5 m grid station along survey lines spaced 5 m apart. Resistivity measurements were carried out utilizing the Wenner-Schlumberger array configuration with 2-m electrode spacing along thirteen profile lines. Results of the survey demonstrated a strong correlation between the two geophysical techniques and subsurface geology. The interpretations obtained from gravity of the field data provided useful information in detecting near-surface channels. The DC-resistivity surveys allowed the determination of the specific resistivity down to a depth of about 6.5 m. The results indicate zones of chalk, marl and chalky marl with limestone intercalation with low resistivity values. Moderate high resistivity values were detected and were attributed to the presence of marly limestone sedimentary rocks.