GPR News September - December 19
GPR Field Methods for Minimizing Site Impact (Part 2)
Application 2: Core holes with line stops
Project 2: Water main burst onto tennis courts
Challenges
- New pavement (recently laid) so minimal impact key a low cost of reinstatement
- Non-traceable water main (asbestos) at roughly 900mm
- Leaking around T-joint to fire service connection. Difficult to determine if it was the water main, fire service or joint that was leaking
- Water main valves were not close to leak and shutting them would affect many businesses. Also, it is a very old water main so valves may not work
Possible Solutions
- Use water stops – install band on pipe; water stopper senses pressure then expands to shut water (look them up to understand)
- Turn valve off – may or may not work and will affect businesses
Solution
- GPR to determine path of water main
- Small core hole pavement on either side of leak which was a much better solution than doing a square cut as it maintains structural integrity when core replaced.
- Live repair (band aid) – suck down with dry vac, find cast joint that was split and had to be cut out.
- Install water stops
- Put in a new T-joint
Project 3: Connecting new water main & join into existing line
Challenges
- Shut off valves far away and would affect 10 businesses that had just opened the same weekend
- Brand new 400mm bitumen paving. Saw cut would be too intrusive. To get through the 450mm bitumen, you would need a 500mm blade so minimum square hole would have been 1m x 1m
- Miscommunication about connecting to existing line
- Non detectable (EM wand) PVC water main
Solution
- GPR to confirm path of new water main and existing water line. GPR was correct and drawings were slightly off hence off-centering in photos…
- Core hole through 400mm bitumen. Core was replaced to maintain road integrity
- Water stop the line and core it at good spot on new road
Product Focus: Proceq GP8800
We take a closer look at one of the most excting products to hit our shores this year.
The Proceq GP8800 is a rugged, ultracompact single wheel GPR. Small enough to fit in the palm of your hand it makes it possible to get into tight spots, close to walls and around columns. Ideal for locating multiple layers of rebar, tendons, ducts, pipes and estimating slab thickness, the GP8800 can be used for hit prevention, as-built verification and structural investigation even in the tightest areas.
The GP8800 produces high resolution scans up to a maximum depth of 650mm by using a stepped frequency antenna which covers a frequency range of 0.4 to 6.0 GHz. For flexibility, the single-wheel connect on either side of the probe allowing for cross-polarization.
The GPR probe connects wirelessly to your iPad and utilizes the user-friendly Proceq GPR Live App allowing for on-site reporting, 3D scans and Augmented Reality.
