GPR as inspection tool
GPR as inspection tool
(OP)
Has anyone out there had experience in using GPR in building inspection? Do you know a contractor in the Florida West Coast area who does this work? Any cost data you have would be appreciated.
A client has requested testing of his project now under construction for subgrade compaction and presence of organic material, and placement of reinforcing steel.
We have never used GPR as an inspection tool; we do have a copy of the Construction Specifications Institute article "Infrared Imaging and Ground Penetrating Radar as QA/QC Procedures".
A client has requested testing of his project now under construction for subgrade compaction and presence of organic material, and placement of reinforcing steel.
We have never used GPR as an inspection tool; we do have a copy of the Construction Specifications Institute article "Infrared Imaging and Ground Penetrating Radar as QA/QC Procedures".





RE: GPR as inspection tool
I don't understand the need for GPR. You have been retained for QA/QC construction inspection/testing of;
-subgrade compaction
-percent organics
-placement of reinforcing steel
These inspections/tests can be done using standard methods. Where do you need to use GPR?
RE: GPR as inspection tool
Thank you for the reply. Most site work is completed, the walls are up and roof framing is in progress. The client has been dealing directly with the builder, relying on the local building department inspections for QA/QC.
The client now feels he needs third party assurance that the work has been done properly,and he is willing to pay for this assurance.
We're doing our due diligence in preparing a proposal for him. We can of course go the destructive testing route. However, the CSI article I referenced above indicates GPR might work, but at a large cost.
Thanks again for any advice.
RE: GPR as inspection tool
RE: GPR as inspection tool
now I understand. However, what if your "findings" indicate bad soil, and overall negative results? Is he willing or ready to accept these results? Or is he only willing to pay if you give him "assurance"? Prehaps he is just looking for cheap insurance.
If that is resolved, I would recommend 4 or 6" borings. Relatively non-destructive and you will be able to get a real first hand look and underlying soil conditions. Also you will be able to run actual laboratorty tests and back up your findings with hard raw test results. Just keep in mind and mention in your report that it only pertains to the EXACT borings or locations you tested! who knows what could be below the ground elsewhere.
RE: GPR as inspection tool
More relevant to your question, compaction is generally a comparison of dry density (field vs. lab standard). As such, moisture content would have to be established. In addition, I doubt that GPR can provide the density precision necessary for verification of compaction density.
RE: GPR as inspection tool
RE: GPR as inspection tool
RE: GPR as inspection tool
As to what the client will do if we find significant problems, we will have to give that some thought. A lot of thought.
Thank you again.
RE: GPR as inspection tool
I don't envy your position. Good luck, and remember that a key decision was the owner's - s/he chose to forego verification testing during construction. A very unwise choice. The presence of a technician and nuclear density gage really keeps a lot of contractors on the "straight and narrow." It could have prevented the present circumstance by forcing the contractor to do the job in accordance with the specs -
Of course, the contractor is clearly responsible for the quality of their work. If it isn't in accordance with the specs, it has to be remedied. At the contractor's expense -
Please see FAQ731-376 by VPL for tips on how to make the best use of Eng-Tips Fora.