Geological Surveys

For the detection of the bedrock, water table and the stratification of the ground, it is possible to buy or source commercially available GPR down to frequencies as low as 25MHz: such GPR have very poor surface resolution and are of little use for typical applications, but they can detect very large features and interfaces (layers) which are located deeper in the ground.

Typical examples of a use for a very low frequency GPR include the detection of the bedrock, the water table, stratification of the ground, and karsts.

Due to building works necessitating a cut into a hillside, a GPR survey was requested to locate the depth from the surface to the bedrock, this would allow the engineers to decide to what extent the ground needed to be pinned to prevent future landslides.

We attended site and collected a series of cross sections which saved for office based processing and compilation into a report and a table of offsets. Because the surface resolution of such a low frequency antenna is poor, the results were challenging to produce, however we identified the bedrock approximately 2m below the surface (shallower than expected) which was sufficient information for the engineers to work from.

There are many disused landfill sites scattered around the UK. At each of these, the thickness of the waste can vary from just a few meters to tens of meters deep. In the past the sites would have been left open and once the land had been filled to capacity the waste was compressed and capped.

Over the years many of those landfill sites have been left unmanaged and become scrub land, whilst the surrounding areas have been developed. As land prices increase, it has become economical to reclaim a disused landfill, clean the waste, and develop it.

Our client had speculatively purchased some of those sites and was looking for a method to cost effectively determine which ones had the most development potential. Sites with a relatively thin layer of waste could be cleaned much more easily and economically than sites with a thicker layer of waste.

We achieved a maximum penetration of 11m but were unable to positively identify the bottom of the landfill. Although we were unable to answer our customers ultimate question of how deep is the landfill, we could inform them that the depth of fill was greater than 11m and using the area of the site, our customer could calculate a minimum volume of fill and therefor a minimum cost to reclaim the land from which they could make an informed decision about further site investigation.