Can I use GPR to investigate road layers?

November 25 2022

Yes, GPR can be used to investigate road layers. Most often you would use a combination of several different antenna frequencies to map different parts of the roadbed. Common applications include the mapping of asphalt layer thickness, investigations of the supporting layers and even surveys of the different layers below the roadbed.

Investigations of roads are carried out for several different reasons. The most common applications are:

Mapping asphalt (surface course) thickness

Recording internal road layers
Mapping geology underneath the road (such as bedrock, peat and soil layers)
Locating utilities within the road and/or the embankment
Mapping pile decks underneath road embankments
Detecting voids within the road structure
Mapping boulders/stones within road embankments
Mapping frozen ground ground frost and moisture

A road investigation survey commonly utilizes 1 to 3 different antennas/frequencies collecting data at the same time. For customers using the MALÅ ProEx system it is possible to collect data with up to 8 antennas simultaneously. These antennas are often either mounted on a MALÅ Road Cart (see image below) and pulled behind a car or attached directly onto a vehicle on special carrier solutions. For smaller areas it is even possible to place your GPR antenna in an RTC Cart.

For road embankment mapping (investigating total thickness and mapping internal layers), frequencies around 450 MHz to 2.3 GHz are usually recommended. If the geology underneath the road is of interest as well, frequencies in the range of 100 to 250 MHz can also be deployed.

Road investigations are often carried out by towing the GPR antennas in parallel profiles over a road. The goal is usually to cover all lanes and the full road width (the exact transect spacing would in each case depend on the purpose of the survey). For accurate positioning, a GNSS can be connected to the GPR system.

Please note that in regions with colder climate the winter roads may be sprayed with salt / salt slurry. The addition of salt leads to an increased electrical conductivity of the roads which in turn leads to a strong attenuation of the radar wave. This will have a very strong negative effect on any GPR measurements and the potential depth penetration of the survey.

Some of the features that you can identify in roads are shown in the images below (both GPR data examples and a corresponding interpretation is presented for reference).

Can I use GPR to investigate road layers?

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