Vertical Electrical Soundings

GBG Group has staff and in house equipment to undertake a Vertical Electrical Sounding survey at any scale. Contact us to speak to one of our team about how we can be of assistance for your design project.

• Earthing design
• Define soil layering
• Delineate the groundwater table
• Delineate saltwater intrusions
• Soil resistivity surveys

Vertical Electrical Sounding (VES) is a 1D electrical method used for calculating the electrical resistivity approximated to horizontal layers. The method is a standard test for earthing design of critical infrastructures such as power poles and electrical substations. VES tests are made using a 4-electrode resistivity survey setup whereby a current is passed through the 2 outside electrodes and the resulting potential difference is measured across the 2 inside electrodes. The apparent resistivity can then be calculated using the known current, the measured potential difference and the electrode spacing.

By taking measurements starting with a short pin spacing (to measure the resistivity distribution in the shallow subsurface) and sequentially longer spacing (to measure deeper into the subsurface) a 1D measurement, terms a ‘sounding’, of the resistivity as a function of depth can be generated.

The calculated apparent resistivity values from the various electrode spacings are compiled and inverted using 1D inversion software based on the initial data curves and available constraining datasets. Inversion of the data is run over multiple iterations to determine the best-fit models of the acquired dataset.

The results of the inversion of VES data are presented as layer models showing the electrical resistivity distribution with depth. All surveys are designed to comply with the Ausgrid Network Standard NS116.