|ELECTRICAL RESISTIVITY IMAGING SURVEYS||
Electrical Resistivity Imaging Geophysical Surveys:-
Electrical resistivity imaging geophysical surveys (also known as resistivity tomography, ERI or ERT) measure the resistivity properties of the sub-surface by assessing the potential drops between electrodes in a variety of configurations, depending upon the type of geophysical survey data required.
Electrical resistivity surveys can be completed using a 4 electrode frame and the survey completed by walking the grid lines. The resulting data will give apparent electrical resisitivty data from a fixed depth range governed by the electrode spacing, usually 0.25 to 1m.
The electrical resistivity tomography survey data are split into levels representing depth intervals and powerful modelling software is used to convert the data into calculated apparent resistivity depth sections. Depths of study up to 30m are not uncommon and on occasion 100m. This is a very powerful means by which to image the sub-surface over large sites for engineering or environmental projects.
Below is an electrical resistivity imaging survey section collected to determine the internal situation within a closed landfill site. Note the low resistivity wastes (blue) over higher resitivity (reds) bedrock. Internal structures such as cell bunds and areas of drier waste are also visible.