Soil site investigations using 2D resistivity imaging technique

Abstract EN

The use of 2D Electrical Resistivity Imaging (ERI) technique in combination with geotechnical and geological data allow the determination of the lithological composition and detailed internal architecture of the subsurface and understanding the characterisation and description of the geology of the site.

This study is aimed to evaluate the use of 2D ERI for the detection and characterisation of heterogeneities in subsurface soil.

The survey was conducted using a Wenner-Schlumberger and Wenner configurations along thirteen ERI parallel profiles which have been investigated in the project of Al-Obaidi Electrical Transformation Station site to find the resistivity and depth of soil horizons with their lithological description.

Analysis of imaging sections shows that Wenner-Schlumberger sections are with higher resolving power than Wenner sections in both horizontal and vertical variations in resistivity reflecting more pronounced soil horizons with depth, where Wenner sections are limited to the upper soil layers.

Resisitvity values in the imaging sections indicate that the stratigraphy of the study area is mostly of clayey soil.

4 to 7 distinct geoelectric layers generally identify the subsurface down to depth of about 20 m.

High resistivity values in the top soil, medium-high resistivity values representing the upper soil layers, while lower reistivity values are indicated for the lowerest layers.

The resistivity values are inversely proportional to many soil properties such as fine content (clay and silt), salt content (sulphate and gypsum content) for saturated conditions, water content, plasticity index (P.I) and void ratio particularly for saturated condition.

The resistivity values are directly proportional to sand content, void ratio, salt contents for dry condition.

The integrated use of ERI technique and conventional site investigation has led to a far better understanding of the site than could have been achieved using site investigation methods alone.