Geophysical investigations are becoming increasingly popular as a method to investigate what is happening below ground, without expensive and disruptive excavation work. The various geophysical methods available today have many application in the field of civil engineering.

Ground Penetrating Radar

Often associated with geological applications the method also applies itself to investigation of the integrity and detail of concrete structures, the location of buried utilities, obstructions and cavities, and fracturing and subsidence monitoring. Impulse radar uses pulsed UHF radio waves to build up a 2-dimensional image of the subsurface.

High frequency antennae are suitable for near-surface investigations (0 to 3m). Lower frequency antennae can penetrate to around 25m+ and are used for investigating larger, deeper features such as mine levels, landfills and geological strata. In many circumstances the depth can be calibrated by scanning a target of known depth or by taking cores at key locations over the site.

Applications for Impulse Radar

• Civil Engineering : mapping of steel reinforcement, voids and fractures within concrete structures and determination of pavement, wall and bridge deck thickness and assessing post-tensioning ducts within bridge beams, detection of old foundations and mine workings, mapping of subsurface solution features in limestone and chalk environments, and performing bedrock surveys.
• Environmental: Location of buried structures, objects, utilities and pollutants, detection of old mine workings, location and monitoring of landfill sites and contaminant plumes, and location of buried drums, tanks and waste.
• Police Forensic and UXO: Location of disturbed ground.
• Archaeology: Location of buried walls and disturbed ground

Resistivity

Resistivity measurements can be used to determine subsurface properties very quickly with no need for initial subsurface examination. Resistivity has application to geological, environmental, engineering and archaeological problems. The method is applicable over large and small areas whether it is a single traverse across a known feature or a grid survey over a development site to provide remediation and planning information.

Conductivity

Conductivity measurements can be used to determine subsurface properties very quickly with no need for initial subsurface examination. Conductivity has application to geological, environmental, engineering and archaeological problems. The method is applicable over large and small areas whether it is a single traverse across a known feature or a grid survey over a development site to provide remediation and planning information.

Applications for Resistivity and Conductivity