GROUND RADAR

Ground Penetrating Radar GPR Surveys:-

Ground Penetrating Radar surveys / Ground Probing Radar (GPR) surveys / Impulse Radar surveys are common names for the ground radar geophysical survey technique. It is a geophysical survey method which can be used to obtain almost continuous subsurface geophysical data or obtain non-destructive testing data from a concrete or masonary structure. Ground Penetrating Radar surveys often require only a single geophysicist and the system can be hand held, trolley mounted or towed by a vehicle. A ground penetrating radar (GPR) unit consists of a power supply, a radar data processing unit and a variety of antennae, depending upon the depth and resolution required. Bentham Geoconsulting have invested in the latest GSSI SIR 3000 ground penetrating radar system and radar processing software from the USA. Our work has included obtaining information on the thickness and condition of a concrete floor slab, locating underground tanks used as pollution interceptors, non-destructive testing of the condition of concrete chimney stacks at a UK petroleum refinery and locating wash-out under the quayside at a northern UK port.

Ground Penetrating Radar operates by propagating electromagnetic pulses into the ground or structure. Where there is a change in the type or proportions of material then some of the radar energy is reflected back to the receiving antenna. The processing unit samples the return radar pulse and depicts the degree of reflection using a predefined colour chart. As the ground penetrating radar system is moved along the survey line a 2-D image is built up showing the changes in the reflected energy. A survey normally consists of a grid of survey lines so that a full site or area interpretation is possible and the extent of sub-surface material changes becomes apparent.
The photograph to the right shows a ground penetrating radar survey being undertaken on a concrete chimney from a cradle at 112m height.

To a skilled geophysicist ground penetrating radar survey data can be interpreted in-terms of engineering or environmental information. After processing, the anomaly patterns are usually shown on an image map and can be used to plan intrusive investigations or simply as a means to avoid existing structural elements during refurbishment.

The image below shows processed ground penetrating radar data obtained over a 1m x 1m test panel used to show the configuration of steel reinforcement within a concrete chimney stack at a UK refinery.

GPR ground penetrating radar surveys - concrete testing & reinforcement mapping

Applications:-

Concrete chimney inspection
Underground storage tanks, UST and fuel interceptor installations
Concrete slab thickness and reinforcement mapping
Location of shafts, voids, air raid shelters, pipes, utilities, services
Foundation and pile cap beam mapping
Pavement condition engineering
Tunnel lining inspections
Forensics
Geological surveys
Pollution