GEORADAR (GPR) SURVEYS

Ground Probing Radar (GPR) is a geophysical method exploiting the propagation of high-frequency (10-2600 MHz) EM waves in the ground and their reflection at velocity discontinuities, toward the surface. These discontinuities are essentially constituted by permittivity contrasts that can exist between different geological materials or between the ground and manmade structures.

EM waves are emitted by a transmitter antenna and received by a synchronized receiver antenna, and the signal is recorded by a suitable data logger. The first result of a GPR surveys are the radargrams, which represent the reflection intensity vs time along a profile, and most of the GPR interpretation is made from the analysis of these diagrams.

Investigation depth and resolution are frequency- dependent, and one would be forced to choose a trade-off between the two, since low-frequency allows to reach greater depths, while high-frequency better define the subsoil heterogeneities. Modern multi-frequency georadar equipment allow to overcome this issue. According to the adopted frequency, it’s possible to in detail investigate from tens of centimeters (concrete investigations) up to several kilometers (under ice sheets). For engineering applications, the first 20 m depth constitute the target.

 

GPR Applications:

  • Utility location: Surveys will locate the exact position and depth of subsurface utilities including gas lines, water lines, electrical lines, communication lines and storm & sewer lines. Old maps and as-built drawings are often unreliable and not updated. Damage to underground infrastructure can be expensive and potentially dangerous.
  • Archaeological studies
  • Water research
  • Foundations design
  • Landslide surface of rupture location
  • Void Detection: Surveys will locate the exact position and depth of subsurface voids and sinkholes. UltraGPR can image cavities of all sizes and depths in soils, beneath asphalt roads and beneath concrete slabs and floors. Subsurface voids are often caused by inadequate soil compaction, poor soil drainage and damaged utilities.
  • Bedrock and Water Table Profiling: Surveys will determine depth to bedrock, depth to water table, bedrock profile and water table profile. Civil infrastructure projects incorporate this information in order to determine drainage patterns and sediment densities and develop a logical grading plan.
  • Lake and River Profiling (Bathymetry): Surveys combines UltraGPR with acoustic sub-bottom profilometers to model freshwater lake and river bottoms.
  • Ice Road Profiling: Surveys has been active in the arctic since 1991. Our proprietary GPS systems are able to quickly and accurately profile snow and ice thickness prior to heavy equipment activities. Ice roads, airstrips, drill pads and any activity on ice is dangerous and can have dire consequences. UltraGPR removes any doubts.