Ground penetrating radar is an undeniably valuable instrument to locate underground and concrete utilities. The GPR device uses electromagnetic waves to scan the ground and find hidden utilities like post-tension cables, electrical wires, pipes, rebars, etc.
Moreover, GPR scanning technology is noninvasive and reliable, which makes it an excellent scanning tool. This scanning tool is used in forensic inspection, archaeology, the military, and the construction world, but this doesn’t mean the GPR method is an accessible technology. In this blog, let us read about the difficulties faced by a concrete scanning expert in their day-to-day life.
When is it hard for a GPR scanning professional?
What can a bad day be like for a GPR scanning professional? Most probably, the day when scanning couldn’t go well.
GPR technology shows its limitations when facing different kinds of sites with varying soil types and ground conditions. You will be amazed to see how GPR at one site can show magical results and leave people scratching their heads at the other. This is not a place to feel discouraged; we are going to learn about atmospheres that limit GPR and how they work so that you are equipped to understand which conditions are favorable and which aren’t.
What is GPR?
Before knowing anything else, let us discuss GPR scanning for those with less knowledge about it. It will help to refresh your knowledge base as well. Ground penetrating radar scanning is a method in which electromagnetic pulses are sent to the ground or concrete, and reflections are detected. These reflections create images of hidden utilities to locate and identify them.
- Most scanned utilities found inside the concrete are waterpipes, rebar, polyethylene gas pipes, and copper wires.
- GPR can also locate underground structures like tanks, tunnels, and foundations.
Amazing, right? GPR is a nondestructive method, and it means there is no need for physical excavation, coring, or concrete cutting to know what lies inside. It is an unmatchable tool that helps to create a utility map for a building or ground. But unfortunately, it also comes with the limitations. Let us know what challenges are created by these limitations:
Penetration depth capacity:
The penetration depth of GPR depends on the Frequency of the GPR antenna selected. Frequency waves that are as low as 100 MHz have longer wavelengths and the capability to reach deeper into the ground. However, the drawback is that these waves are prone to underground interference and do not provide high resolution.
Waves that have a 1000 MHz range are shorter in wavelength and can provide high-resolution subsurface images. The drawback with these waves is that they cannot penetrate deeper into the ground.
Penetration depth is affected by antenna frequency and other factors like soil density, the presence of metallic objects, and the amount of moisture in the soil. To get the best idea of the object and its location inside the concrete, the professional needs to create a balance between the Frequency of GPR and penetration depth.
Seeing through moist soil:
Factors like scattering, dispersion, and absorption cause attenuation (reduction of GPR signal). Soil having high levels of moisture content reduces the strength of electromagnetic waves. The GPR signal becomes weak and unable to give the correct resolution.
It means either the signals will not penetrate deeper or they won’t be detected by the antenna, making it difficult to get the right location of the object. To reduce attenuation, Professionals use high-frequency signals.
GPR make and model:
Different makes of GPR devices are designed differently. Some devices can only detect 2D images of concrete or ground and can only detect the utilities that are parallel to the ground. This happens due to the position of the antenna, which is such that it only emits a single beam of radar that goes in a downward direction. As a result, 2D images are created by GPR. A 2D GPR device can locate subsurface utilities in an ideal environment but works less in wet soil.
However, some other GPR systems can provide 3D images, and for that, multiple antenna arrays and GPR is required. Data collected by this GPR helps to create 3D images of structures and dimensions of embedded objects. Professional GPR scanning companies use up-to-date equipment to avoid any data lagging.
GPR cannot see through metal:
GPR signals are easily cheated by rebar, pipes, and other metal objects inside the concrete. The radar cannot penetrate the metal and tell what exists beyond it. Metal pipes or rebar reflect back the signals at the place of absorbing it.
Even the best GPR requires a trained professional to interpret the signals sent by radar, and it cannot be performed by anyone else. The data is often complex and requires calculations only an expert can do. The images come in a series of different reflections that can be affected by factors like depth and different utility materials.
If the professional is familiar with GPR and its principles, they will be able to distinguish between rebar and a plastic pipe easily. If you are looking to hire reliable and precise concrete scanning services, Concrete Insight provides GPR Scanning in MD and VA. We have 25-plus years of experience, and our professionals are skillful and experienced. To get precise GPR Scanning, coring, and testing services, visit our website now!