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 Is GPR a safe testing technique?
Many people question whether there is any danger for the person using GPR equipment, and the answer is no. Although “ground penetrating radar” may sound like a hazardous technique, it is extremely safe and emits roughly 1% of the power of a cellular phone signal.
Can GPR distinguish between post-tension cables and rebar?
The quick answer is yes. Like all trades there is some skill involved and necessary to accurately identify the sub-surface items. It is extremely important to use a reputable company with a history and speciality in locating post-tension cables. It is easy for someone without the correct training to misidentify the items and could prove to be very costly to repair such a mistake.
Can I see non-metallic subsurface features with GPR?
GPR is extremely accurate when it comes to locating metallic and non-metallic objects. GPR systems work by sending a tiny pulse of energy into the ground from an antenna. An integrated computer records the strength and time required for the return of reflected signals. Any subsurface variations, metallic or non-metallic, will cause signals to bounce back. When this occurs, all detected items are revealed on the computer screen in real-time as the GPR equipment moves along. SRImaging GPR locators can even tell from the signal returned whether the feature in question is metallic or non-metallic.
Can GPR determine how deep an object is below the surface?
If there is another buried or embedded object, at the site, whose depth is known, we can be very precise with our depth calculation. If there is no known object, we will have to do our own calculation based off of our past experience. GPR determines depth by the time it takes the signal to pass through a material and then return, which our operators will set. Moisture greatly hinders the depth that we can penetrate, thus if it is raining we will not see as deep as if the area has had several days of dry weather.
Is GPR necessary if "811 Call Before You Dig" locates the utilities?
The city locators will locate all documented utilities for each of the individual utility companies. Ground radar becomes valuable when a construction company is concerned with all other unknown utilities that were not as well documented. Ground radar is also beneficial by locating a utilities depth as opposed to just its location.
What is GPR used to determine when scanning pavement?
GPR is able to measure pavement layer thickness and it can reveal other conditions which are not seen from the surface. When GPR is used on concrete it can reveal locations of reinforcements and the presence of full-depth asphalt patches. GPR for bridge decks is used to assess the location of delamination and freeze-thaw damage, computation for depth of reinforcement, evaluation of deterioration quantities, identification of amount and location of debonding of overlay, measurement of overlay thickness and quality control of reinforcing
bar placement.
How deep can the radar survey penetrate?
The radar signal depth is dependent on the type of material and selection of antenna. Our antenna for underground utility locating (400MHz) can penetrate to a depth of 10' under ideal soil conditions. Our antenna (1600MHz) for concrete scanning can penetrate to a depth of 18" under ideal conditions, and for thicker areas we can scan from both side to achieve a full image.
Can your ground penetrating radar system equipment be used to scan vertical surfaces or could it be used on a ceiling?
Yes. We regularly use our equipment to scan for the location of rebar in concrete columns and walls. On occasion we are also asked to scan from the underside of a floor to mark out the reinforcing steel, post-tension cables and any embedded conduits. This is most common when a customer wants to set anchors into a floor or for seismic on large piping.
Can ground penetrating radar tell me the size of a void cavity below ground?
Ground penetrating radar can tell the area where the void is occurring and at what depth the void starts, with clearly identified boundaries. The ground penetrating radar systems cannot determine the overall depth of how deep the void extends beyond from where it starts.
How is the collected data recorded and presented?
With the advanced equipment available to us now, the data is collected and presented in real-time, on-site. Visit the GPR Pictures page to see real world examples.
Can I use my cell phone around the equipment?
GPR operates by transmitting and receiving electromagnetic (EM) energy at a particular frequency, which is only interfered with by some two-way radio communications, but not cell phones.
What is the cost of a typical GPR survey?
SRImaging with the most accurate locators in subsurface imaging provides a full range services, varying in cost, including:
- Underground-utility locating
- Underground-utility mapping (CAD drawings)
- Concrete scanning
- GPR road scanning
- Core Drilling
Please contact our office for a quote on any of our services.
If you have any questions that this site has not answered, feel free to contact SRI today.
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