GPR ( Ground Penetrating Radar )

ClearView Geophysics Inc., carries out GPR (Ground Penetrating Radar) surveys for a wide variety of applications:

  • diamond exploration
  • UST locates
  • depth to water table
  • depth to bedrock
  • pipe locates
  • stratigraphic mapping
  • contaminant mapping (in special cases)
  • reinforced concrete testing
  • road-bed studies
  • grave site mapping

 

Note that GPR works best in low conductivity (high resistivity) areas. Conductive materials (e.g., clay) attenuate the GPR signal to the point that very little depth penetration is achieved. Penetration is greatest in unsaturated sands and fine gravels.  When possible, additional geophysical methods, such as the Geonics EM61 metal detector for UST locates, or the Geonics EM31 for depth to bedrock mapping, are used.  Physical evidence from boreholes and test pits are commonly used to complement the geophysical data to provide a more robust quantitative interpretation of the broad coverage geophysical results.

GPR can also be used to detect contaminants and water main leaks, if the conditions are right. The reflection delay time is controlled by the dielectric properties of the material. The signal velocity (m/ns) is approximately equal to one third the value of the dielectric constant. Some contaminants have different dielectric properties compared to the host geology. For example, GPR signals travel at 0.01 m/ns through sea water compared to 0.06 m/ns through clean, saturated sand.

The penetration depth of the instrument is also dependent on the chosen base frequency. The higher the frequency, the less the penetration. The trade-off is that the lower frequencies lose target resolution. Typically, 100 MHz and 50 MHz are used for bedrock detection, 500 MHz and 250 MHz antennae are used for tank locates, and 1000 MHz is used for rebar checking.

Contact ClearView Geophysics Inc. to discuss whether this method is ideal for your site specific case.

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