| Project Background |
| The project site was a newly constructed
building in Center City, Philadelphia. Geo-Graf was
contacted to discuss nondestructive methods of locating
tendons prior to the installation of electrical equipment
that had to be thru-bolted to the floor. Other techniques
such as x-ray were tried by others, but proved to be
unsuccessful, hazardous, and disruptive to the active
building. We suggested the use of GPR, which had been
previously utilized with great success for delineating
rebar in concrete. |
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| Geo-Graf Investigation |
| We utilized a high frequency 900 MHz Ground
Penetrating Radar (GPR) antenna system to locate and
field mark the post-tensioned cables in various areas
prior to construction. Geo-Graf found that the cables
were generally located within the middle of the 9"
concrete floor slab at somewhat irregularly spaced
intervals. |
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| GPR Data Profile |
| Please Wait as
the image below loads. It is actual radar data of
post-tensioned cables collected by Geo-Graf engineers
utilizing a 900 MHz GPR antenna. |
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| Above: A GPR data profile over the
proposed construction area. The post-tensioned cables are
shown above and are generally located within the middle
of the 9" concrete floor slab. 900 MHz GPR antenna
system, edited from a 12ns range. |
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