Ground penetrating radar is a geophysical device that gives a continuous profile of the underground environment. We use ground penetrating radar manufactured by Geophysical Survey Systems Inc. The set includes measuring antennas with 100, 400 and 1200 MHz frequency and ground penetrating radar Mala GeoScience GPR ProEx, that has 500 MHz and 2300 MHz measuring antennas.
We perform following surveys with ground penetrating radar:
Studies preceding road reconstruction works (in combination with geological drilling)
Normally radar measurements on both driving directions are performed, in addition also cross profiles can be made. The survey gives a continuous profile of various pavement layers. The number of boreholes that are necessary for adequate interpretation of radar profiles and for establishing the cross section of the road, are determined based on the radar profiles. Such combined method (ground penetrating radar and boreholes) gives a considerably better picture about the road geology than traditional surveys that are based only on boreholes.
Quality check of road works (air voids content of bitumenous pavement)
In order to determine the air voids content three measurement lines are used for two lane road – on outer rut of both lanes and on the pavement joint at the road axle. Unlike traditional quality check with core samples, the radar measurements gives continuous data about air voids content of asphalt concrete pavement on a measurement line – it considerably diminishes the randomness of air void content data. The impact area of deductions is reduced tens of times for each sector checked for air voids content. Only 8 core samples are taken from the tested section for calibrating the measurements. This means that the number of boreholes that damage the pavement is diminished tens of times. The only restriction about this method is that it can’t be used if the pavement is wet or frozen.
Ice thickness measurements on ice roads
Radar gives a continuous profile of ice thickness on measurement line. The measurement data can be presented either with colours on a map, as a table or as a profile. In addition to ice thickness measurements on ice roads, it’s also possible to get the first picture about ice thickness in a wider area – the radar measures along a zigzag profile between the edges of the chosen corridor. This kind of measurement gives an overview of the distribution of areas with thicker and thinner ice cover. If the ice condition is unknown, it’s safer to fix the radar behind the snowmobile or on the ATV for preliminary measurements.
Locating the utility networks, buried structures and voids
For searching and locating underground objects the measurements with radar are made along measurement lines that are either parallel or perpendicular to each other. This enables to determine approximate contours of the object and to draw these on the map.