GEOPHYSICS

Contact Us

Ground Penetrating Radar GPR Surveys:-

Ground Penetrating Radar, Ground Probing Radar, GPR, Impulse Radar and Surface Penetrating Radar are common names for the ground radar geophysical survey technique. It is a non-destructive geophysical survey method which can be used to obtain almost continuous subsurface geophysical data or obtain non-destructive testing, imaging and mapping data from a concrete or masonary structure including rebar mapping.

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 Radan radar processing software from the USA.

Our work has included imaging concrete thickness and reinforcement mapping in concrete floor slabs, locating tendon ducts in concrete bridge decks and slabs, locating underground tanks used as pollution interceptors, testing the condition of reinforced concrete chimney stacks at a UK petroleum refinery and locating wash-out under a 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 as a requirement for mapping the configuration of rebar reinforcement within a concrete chimney stack at a UK refinery.

Applications:-

Concrete chimney inspection

Chimney flu location

Utility detection and on site mark out surveys

Concrete slab thickness imaging and rebar reinforcement mapping

Location of conduits and cable trenches in concrete slabs

Post tensioned tendon duct location in concrete bridges and decks

Retaining wall surveys

Location of shafts, voids, air raid shelters, pipes, utilities, services

Foundation and pile cap beam mapping

Pavement condition assessment

Tunnel lining inspections - lining defects and voids

Forensics

Geological surveys

Contaminated Land and Pollution surveys

Badger sett mapping

Masonary arch bridge assessment