What Is Ground Penetration Radar (GPR)?

by | Nov 20, 2020

Though it might sound like something from an 80’s action movie, ground penetration radar (GPR) is actually an important part of many a site investigation. This non-intrusive investigative method is mainly used to identify buried services before a careful evacuation – as well as looking for sinkholes and features of karst Geology. But how does it work? And in what situations is it most needed? The team here at Borehole Solutions Ltd, a  geotechnical firm working out of Peterborough, England, wanted to explain exactly that.

 

What Is It?

First thing’s first, then, what actually is it? This technique dates back almost a century. The first radar technology was conceived as far back as the late nineteenth century, however its first real use within a geotechnical setting was in 1926 when a man named Dr. Hülsenbeck patented his pulse radar system. It works by sending pulses of energy down into the ground you’re looking to investigate – but how?

 

How Does It Work?

High-frequency radio waves are first emitted from the GPR transmitter into the ground below. Upon hitting buried material (such as concrete) the pulse is either reflected or scattered back towards the surface. A receiver records the return pulse (and its particular characteristics) and from that a comprehensive picture of the subsurface can be built up. Unquestionably, the technique’s main advantage is that of its non-intrusiveness.

This is particularly beneficial when you look at the kinds of features GPR is used to locate. For instance, the radar is often used in locating utilities (gas works or fibre optic cables, for example) under major arterial road carriageways and motorways. In other words, any work that needs doing is going to have a fairly major impact on the surrounding area in the form of road closures. By using a non-intrusive site investigation method like GPR, you significantly mitigate ‘downtime’. So, it’s not only cheap in its operation, it’s often more economically viable for a project across its entire lifecycle.

 

A Variety Of Materials (And Lack Of Materials)

Another benefit of this method is that it can detect pretty much anything under the ground; it works, remember, on recording those changes in the subsurface environment. This means that GPR not only detects buried materials, but voids as well (such as sinkholes or former coal workings, for instance).

 

How Accurate Is It?

GPR is, on the whole, an incredibly mature and accurate surveying and mapping methodology. Its accuracy varies, depending on factors such as the material composition and particular moisture content, but generally speaking, it can be very well trusted to deliver reliable results.

 

Contact Borehole Solutions Ltd

GPR is one of those techniques which is often forgotten about in the geotechnical world; it just goes about its work nice and quietly, no JCB diggers required. Yet without this silent bit of kit, the ground investigation world would be a poorer place off! Used not only in geotechnical settings, but in forensic and archaeological arenas as well, GPR surveying should be carried out by highly-qualified contractors. Now, where could you find one of those?!…

So, if you’d like to find out more about our site investigation services – which include GPR – then get in touch! Contact Borehole Solutions Ltd today on 01733 200501 or by emailing us on info@boreholesolutions.com. Or why not head over to our Instagram to take a look at some of our previous work?