Sinkhole Repair: Chemical grouting eliminates need to excavate pavement at busy port
Client: The Port of Palm Beach, West Palm Beach, Florida
The Port of Palm Beach had a problem on its hands when a sinkhole developed under one of its main traffic routes. A leaking sewer line and storm water main drain caused erosion, resulting in a 4-foot-wide area of asphalt sinking approximately 6 inches. Beside causing major wear and tear on trucks and other equipment driving across it, a worsening dip could pose a dangerous situation.
Solution:
The contractor opted for probe grouting to seal the leaks with an expansive polyurethane resin. This eliminated the need to excavate the pavement. There was no need to shut down complete access to the port. The crew needed to cordon off only the immediate work area, allowing full function of the port.
The process:
The grout technician drilled holes through the asphalt and inserted an injection probe down to the leaking pipe. He injected Prime Flex 920, a hydrophobic polyurethane resin, around the pipe. The 920 sealed the leak by forming a closed-cell, watertight mass around the pipe. The expanding foam filled the voids created by the leaks. The technician continued resin injection in several “lifts” or installments between the pipe and the surface. This stabilized the soil and created a rock-hard column that increased the load-bearing capacity of the substrate.
At this point, following soil stabilization, the crew injected Precision Lift 4.0#, a high-density polyurethane structural foam, compacting any remaining loose soil and lifting the asphalt 4 1/2 inches. Any further lifting threatened to rupture the asphalt due to its softness and flexibility (relative to concrete). A slight dip remains where the sinkhole was, but does not impede normal operations of the busy port.
Asphalt is often not a great candidate for lifting because its relative softness and flexibility can result in tearing or rupturing of the asphalt. Port officials did not want the major disruption to operations caused by replacing the asphalt, so in this case it was a good solution.
Outcome:
The contractor sealed the leaks, stabilized the soil, and lifted the sunken asphalt nearly level. They completed the job within six hours.
The alternative:
The typical method of repairing this type of problem would include:
- shut down the road,
- cut out the asphalt,
- dig down to the pipe,
- repair the leak in the pipe,
- backfill the hole,
- replace the asphalt.
Repair costs of this approach are in the tens of thousands of dollars. The contractor solved a problem and fixed a potentially dangerous situation for the Port of Palm Beach at a fraction of the cost. In fact, the client said this solution saved him $40,000 and the major disruption of an excavation repair.