GPR IN THE RAIL CORRIDOR

GPR has many applications within and around the rail corridor. 
Ground Penetrating Radar (GPR) is a fast and effective electromagnetic survey technique that enables the measuring of layers thickness, detection of changes on structure or on materials properties along the line. It can also detect different types of defects such as ballast pockets, fouled ballast, poor drainage, subgrade settlement and transitions problems, depending on their extension.
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These defects are generally the causes of vertical deviations in track geometry and they cannot be detected by the common monitoring procedures, namely the measurements of track geometry. (Fontul et al., 2016)

In addition to track defects GPR can be used to assess heritage infrastructure surrounding the rail corridor, for example platforms or tunnels. 

Application includes:
  • Tunnel wall and rood assessments 
  • Voiding in tunnel roof or walls
  • Ballast thickness on tracks
  • Utility location in or around tracks
  • Platform structural inspection
  • Excavation planning
  • Heritage rail structure assessment 

Tunnel Inspection
Tunnels are an essential and growing part of our infrastructure all around the world. Since it is hard to estimate how long time a certain tunnel will last, and be safe to use, there is also an increasing need to continuously estimate the status of our tunnels. If not maintained, tunnels will not only cause delays and grievance, but also lead to human health problems, unnecessary injuries, and in extreme cases even loss of lives. Safe, efficient, and constant evaluation of all our tunnels is therefore needed.

Common PRoblems
​The rate in which a tunnel is deteriorating is dependent on many different factors, such as environmental, geological, materials used, construction method etc. Life span estimations are unreliable. Unexpected and untimely problems are common. Some of the problems include movements in bedrock causing fractures in tunnel lining, water seepage and other structural defects. Voids and lining separation may collect water causing stress and failure, especially during winter climates. Rapid and precise evaluation methods and tools are therefore needed.

METHODS
The methods in which a tunnel can be inspected vary to a certain extent with what kind of tunnel and what purpose the tunnel fulfils but a non-destructive and rapid method is preferred. Common methods include direct and mechanical methods, infrared thermography, multi-spectral, ultra-sonic methods, and Ground Penetrating Radar (GPR).

Due to advances in GPR development, the GPR method is in many areas around the world quickly becoming the preferred method for tunnel investigations. GPR is an easy-to-use, non-invasive, rapid and light-weight method. It can successfully detect and track fractures, both in lining and in the bedrock behind. GPR can locate risk zones, such as locating areas where lining separation and corrosion is present. GPR gives in most cases instant results at site, whereas other methods usually need more thorough and tedious evaluation.
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MALA GPR Applications
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