In a bold step toward integrating advanced geophysical tools into everyday construction practices, Granger Construction has added Ground Penetrating Radar (GPR) to its growing arsenal of drone-based visual capture technologies. This advanced non-invasive radar system, formerly limited to military and scientific use, is now transforming how construction teams view and work with subsurface conditions.
At the Muskingum County Jail project in Ohio, Granger’s Visual Capture team used a drone equipped with GPR technology to pinpoint the source of two sink holes that turned up while excavating a portion of the 20-acre site. The scan not only identified an undocumented dump pit as the cause of the two visible sink holes, but it also detected several other underground voids along an east-west trajectory now believed to be an abandoned coal mine shaft under the project site. Based on these results, the client and project team were able to make more informed decisions on how to move forward to resolve the sink holes and protect the long-term integrity of the $78 million project.
Why GPR?
Ground Penetrating Radar (GPR) is a non-invasive geophysical technology that emits radar pulses into the ground and analyzes the reflected signals to create images of subsurface structures. It’s increasingly being adopted in construction due to its:
⦁ Portability and affordability
⦁ Real-time data output
⦁ High-resolution imaging – capable of scanning depths of nearly 40 feet in average soil and 10 feet in concrete to accurately detect objects 1” or larger, with a positional accuracy of 1cm +1ppm
⦁ Minimal environmental impact
Key Applications of GPR in Construction
- Locating Existing Utilities and other Unknown Conditions: GPR helps identify the exact location of buried utilities such as fiber optic lines, storm sewer pipes, electrical and gas conduits and other unknown subsurface items such as old foundations, wells and more. This prevents costly and dangerous conflicts during excavation or directional drilling.
- Structural Analysis: GPR is used to assess the integrity of existing structures including building foundations, bridge decks, dams and more. It can detect corrosion, voids and material degradation which can then help teams prioritize maintenance or replacement solutions.
- Concrete Scanning: During renovations, GPR can locate post-tension cables, radiant heating tubes and electrical conduits to ensure safe cutting and coring without damaging these embedded systems.
Granger’s Innovation Edge
GPR is the newest component of Granger’s in-house Visual Capture toolkit, which serves numerous projects throughout Michigan and Ohio. By incorporating advanced technologies such as GPR, Granger maintains its leadership in promoting safety, efficiency, and innovative construction practices.
