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BENEFITS OF GROUND PENETRATING RADAR FOR INFRASTRUCTURE INSPECTION

January 2nd, 2018   Author: Doug Thaler

Ground penetrating radarThe ever-growing advancements in the field of construction design using concrete as well as the growth and safety of our infrastructure has given birth to the demand of services like concrete scanning, non-destructive testing, coring, and cutting. In the past few years, a technique for accessing and imaging the interior of the concrete structure called Ground penetrating Radar has emerged which has provided quantitative data to properly assess the structure being inspected.[1]

 

Ground penetrating Radar uses electromagnetic fields to examine the dielectric materials for detecting their structures and also the material properties. The widespread use of GPR occurs not only for geologic materials but also man-made composites which include construction materials like concrete, asphalt.[2]. As the electromagnetic rays fall into the material under investigation, the reflections of these waves are analyzed to evaluate the location and the depth of the buried objects and detected interfaces. [3].

 

In the field of infrastructure inspection, there are a number of advantage of non destructive testing utilizing GPR;

 

 

-Accurate Imaging

One big advantage of GPR is that it provides accurateground penetrating radar images. GPR provides orientation and the depth of the buried objects due to its ability to analyze the slices at different depths. Current inspection methods are manual and visual in nature not providing the quantitative data necessary to properly maintain today’s infrastructure.

 

 

 

 

 

-Cost effective as compared to drilled core

 For the most part destructive testing involves drilling out concrete samples or coring. These cores are used by the highway engineers to determine the thickness of different layers by taking a sample and using that sample for laboratory assessment. However, this method of core sampling is not only time consuming but also expensive. In addition, coring is destructive in nature exposing the concrete to air, water and the elements which will further deteriorate the structure being inspected. Utilizing ground penetrating radar is nondestructive in nature keeping the original structure intact and making long term maintenance less costly.

 

 

-Pavement evaluation
GPR’s applications in the field of pavement evaluation are numerous which include determining pavement thickness, detection of voids and water intrusion under the joint concrete slabs, compactness of the ground, the location and placement of rebar, utility lines, pipes and conduits that are placed under the concrete.

 

 

-Controlling embedded depth and inclined position of the dowels
The embedded depth and the inclined position of the anchors placed in a perpendicular position to the joints in concrete pavements during construction can be controlled with the help of GPR.[3]

 

 

-Stay on Schedule
The unexpected problems that arise while working on a construction project can and almost always do delay it. The use of GPR (Ground penetrating radar) scanning is extremely beneficial compared to the current techniques because it can scan and identify the potential problems before they show up on the surface and become a headache for the engineers. Hence GPR lets the company save time by allowing the builder or engineering firm to find issues prior to construction as well as avoiding drilling into obstructions that can cause further delays. [4]

 

 

-Difficult Sites & Locations
Due to the very small size of the GPR sensors, they can be used in tight spaces and they can be placed in any orientation either on walls, floors or ceilings.

 

 

-Analysis of Geological structures
GPR can be used to analyze geological structures. With the ability to scan through the surface and map rocks, soil and fill layers in geotechnical investigations and for foundation design can be done in a nondestructive manner. Locating potential obstructions prior to digging can save time and money as well as keeping the construction site safe.

 

 

 

-Survey of critical transport Infrastructure
GPR is used to survey roads, airport runways, tunnels, bridge decks and bridge approach ways as well as highway pavements, dams, ports and other critical infrastructures. The underground voids, obstructions and cavities are detected as well as conduits and utilities with the help of EM waves.

 

 

-Detailed inspection of reinforced concrete
Another huge advantage of GPR is that it can performinfrastructures inspection a detailed inspection of reinforced concrete. Moreover, it can be used to locate steel reinforcing bars and pre/post-tensioned stressing ducts. The pre-cast concrete structure’s quality control can also be carried out. Locating post tensioned tendons as well as their positioning and post construction inspection analysis can be conducted with ground penetrating radar being used to verify concrete thickness, rebar and post tensioned tendon placement against construction plans.

 

 

 

-Bridge Decks and Bridge Approach Ways
GPR is used to map the zones of deterioration and delamination on bridge decks. Moreover, the zone of fungal decay in the wooden bridges can also be detected. This can help the constructors and engineers to take necessary steps to save the bridges from damaging which can ultimately lead to huge loss.[5] The FHWA requires 

ground penetrating radar image

that bridges be inspected every two years. Currently they are inspected the same way they have been inspected for the past 50 years.  It is much safer and less expensive to locate issues early on and conduct repairs accordingly vs rebuilding a bridge or putting public safety at risk.

 

 

-Health and Safety
GPR is harmless to the infrastructures and offers no threats to the general public and as well as the operators. It can be used safely even in crowded areas as it poses no risk to the people around. Ground penetrating radar is safer both for the inspector and the public.

 

 

Conclusion:
The use of concrete scanning with GPR (Ground Penetrating Radar) till now has been quite limited and can easily replace the manual subjective nature of today’s concrete inspections. One reason for the limited use of gpr till now has been the availability of trained technicians and sophisticated interpretation software.

 

 

As time has progressed, certain developments in the hardware and software including making the interface user-friendly and private companies developing more sophisticated interpretation software have brought GPR into greater use. GPR is a reliable method for locating objects buried in concrete. Furthermore, the recent developments have modernized the technology to an extent that the data can be converted into 3D volume images to be displayed as volume renderings and plan maps at specified depths.[1].

 

 

The ability to utilize quantitative assessments and the data provided to conduct repairs on vital infrastructure assets in order of importance, allow the asset owners to conduct repairs and maintenance in order of importance and within budget.

 

Infrastructure Preservation Corporation is a non destructive testing and robotic engineering company that specializes in updating transportation infrastructure inspections with modern technology and robotics. For more information go to https://www.infrastructurepc.com.

 

References
[1] “Web page 1.” [Online]. Available: https://www.sensoft.ca/blog/advantages-of-integrating-gpr-in-concrete-inspection/.
[2] A. P. Annan, “Ground penetrating radar principles, procedures and applications,” p. 293, 2003.
[3] “Use of Ground Penetrating Radar for Construction Quality Assurance of Concrete Pavement Use of Ground Penetrating Radar for Construction Quality Assurance of Concrete Pavement,” no. November, 2009.
[4] “Web Page 2.” [Online]. Available: http://www.concretevisions.ws/ground-penetrating-radar/benefits-gpr-technology/.
[5] L. Pajewski et al., “Applications of Ground Penetrating Radar in civil engineering – COST action TU1208,” IWAGPR 2013 – Proc. 2013 7th Int. Work. Adv. Gr. Penetrating Radar, no. July, 2013.

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