Ground Penetrating Radar (GPR)

Ground Penetrating Radar is an NDT method that investigates and maps the subsurface. Sandberg uses it to analyse building construction details, identify defects, locate buried objects, and more.

What is GPR?

Ground Penetrating Radar, commonly abbreviated to GPR, uses high-frequency radio waves to detect changes and objects in the subsurface. It is a geophysical technique initially developed for geological mapping.

It is now widely recognised as a highly cost-effective, non-intrusive testing technique. It offers a rapid means of obtaining subsurface information from soil and various materials, including concrete, brick, masonry, wood, and asphalt.

Ground Penetrating Radar can penetrate below the surface and detect changes in the subsurface. However, it is not limited to the detection of metallic objects. It will also differentiate between most materials, such as plastics, clay pipes, wood, disturbed ground, layer interfaces, and voids. The main requirement is that the target material has sufficiently different electrical properties from the material surrounding it.

GPR will also provide estimates of depth and layer thickness—all done non-intrusively. Sandberg uses it to determine the depth and extent of objects, the width of walls, and the thickness of slabs, asphalt, and screed.

GPR Surveys in the Construction Industry

Sandberg was amongst the first to recognise the potential of Ground Penetrating Radar surveys as an investigative survey technique in the Civil Engineering and Construction industries.

We have developed techniques and considerable expertise in the application and interpretation of Ground Penetrating Radar, including:

• Concrete imaging and rebar detection
• Concrete floor slab surveys
• Chimney flue location
• Historical building investigation (embedded steel location)
• Post-tensioned tendon location
• Locating underfloor heating pipes
• Mapping of services and conduits in concrete floor slabs
• Retaining wall surveys
• Slab thickness measurement surveys
• Site mark-up surveys
• Wall thickness measurement
• Void detection and location

GPR is a very flexible, nondestructive survey technique with many potential uses. Its application is limited only by the surveyor’s imagination and skill. Their knowledge and experience in conducting and interpreting the survey data are crucial.