Construction of multi-purpose geophysical test site on a lateritic clay soil

Abstract

Developing a geophysical test site (GTS) to a full target requires a lot of work in sequential order. This article presents the construction procedures and requirements for developing a GTS, field measurements, geophysical response analyses, and site descriptions. A GTS is an experimental site that contains several targets of known properties, materials, and parameters, buried at different locations, depths, and orientations. The 55 m × 55 m multi-purpose GTS was developed within the Ahmadu Bello University Geophysics Test Site (ABUGTS). The site was developed on a lateritic-clay soil within a shallow depth of 0.6–3 m to study the geophysical signature of various burial scenarios and replicate situations usually encountered in geophysical surveys, engineering, and environmental investigations. A pre-buried investigation with integrated geophysical methods was conducted to provide adequate information about the site condition. The integrated geophysical methods were also explored on a few buried targets for test runs alongside a laboratory test to determine the electrical and magnetic properties of the buried targets. The pre-burial study indicates that the site’s electrical resistivity (ER) values decrease significantly from 1081 Ωm to 47 Ωm with depth due to the regional groundwater effect. The post-burial investigations show positive results, corresponding to the laboratory results. The post-burial results show that the subsurface resistivity of the burial terrain decreases from 200 to 0.1 Ωm due to the influence of the buried metallic target and increases from 1081 to 110,000 Ωm due to the influence of the buried non-metallic target, while the total magnetic intensity of the site increases from 44,500 to 48,000 nT. Seismic result shows distortion in subsoil layers after the buried target, confirming a significant influence of the natural geophysical signature of the site by buried targets. The implications of the GTS on economic growth and educational activities were discussed. Geophysicists, researchers, and institutions can now take advantage of the site to explore the existing and new geophysical techniques routinely employed in geophysical investigations. Geophysical equipment manufacturers and individuals can also use the site for instrument configurations. The site can provide an experimental site to appreciate the nature of subsurface anomalous generated by different buried targets. It can serve as a guide for modelling new GTSs while bridging the gaps between hypothetical teaching and real-life problems through effective field-based exercises.