Resistivity Isotropicity and Homogeneity for Sub-base Layer of Selected Roads in Ninevah Governorate, Northern Iraq

Abstract

Field surveys of electrical resistance are achieved in order to study the sub-base layer of the under constructive roads where the present study is conducted in six locations (Bardarash, Rovya, Mahalabyia 1 and 2, Al-Gwair and Bashiqa) based on the existence of projects for roads under construction by the Directorate of Roads and Bridges. Furthermore, Azimuthal resistivity survey is applied using Parker-Watson array with an electrode spacing and azimuth depending on road directions. Also a reverse surveys are performed on the same points of sounding. The resistance ratios (Rd1, Rd2) are then calculated and represented as polar diagrams and cartesian curves. Moreover, analysis relationships are done between the phases, amplitudes, frequencies and their reflections. It is observed from the polar diagrams of the mean resistance values, there is a resistivity variation with the depths and directions of the spread. It is also noticed that there are changes of the Anisotropy Coefficient (AC) values reflecting the effect of the lithofacies contrasts of the sub-base layer belonging to the paving and compacting mechanism underneath the central point of the azimuthal survey. A comparison between AC and Homogeneity Indices (HI) are determined, and the latest values are detected using the standard deviation approach which is thought to reflect the dispersion of measured resistances due to the heterogeneity constitutes.