warehouse and office extension was planned for an old manufacturing facility. Many renovations had occurred at the site over the years with little documentation. This left the engineering firm and the contractor working on the current project with little knowledge of where utilities ran throughout the structure.
Challenges
Confirming the as-built construction at the design stage allows planners to optimize placement of new infrastructure. On this project it was clear that some long cuts would need to be made in the existing slab on grade. Due to the complex operations of the facility it was known that many conduits and electrical cables ran through the concrete. Striking a live power cable was a real hazard on this project and something had to be done to mitigate the risk.
Solution
CONQUEST® 100 GPR was brought on site to scan concrete slab structures and identify embedments and, in particular, locate live power cables to protect the cutting crew. On one occasion, the GPR operator found an anomalously strong response from a reinforcing member but no indication of the expected conduit. In order to get a clearer picture of what was happening in the concrete a 24" × 24" grid was collected. When viewing the map of live power cables over the same area, a strong power response was noted. This lined up with the strong GPR response, suggesting that the rebar and the power cable were located side by side.
The map of live power cables produced by Conquest allows operators to know the risks they are dealing with.
Results & benefits
Subsequent coring and chipping confirmed that an electric cable was located close to a rebar. The GPR anomaly was indeed the combined response of the rebar and the electrical cable. The cutting crew was able to avoid potential injury and the project continued on schedule.
This case study demonstrates the power of Conquest® with PCD; combining the two technologies provides more definitive indication of embedded live power cables. Some key observations are:
- Conquest® imaging quickly defines reinforcing structure
- The map of live power cables produced by Conquest® allows operators to know the risks they are dealing with
- GPR provided information that kept people on the job safe and allowed the project to move forward on schedule
