How Do They Repair a Sinkhole Anyway?

sinkhole repair

I’m often asked how Helicon repairs sinkholes, and that is a reasonable question. 

It’s one I’d never even considered asking before coming to work for a sinkhole repair company. Frankly, it had never affected me personally, so I had no reason to ask. To my surprise, Hillsborough County is ranked third in the state for sinkhole occurrences. Number three! That’s where I live! So I suppose that I’m lucky I haven’t been affected, but I sure know who to call if I am.

Helicon’s crews are working constantly around the state. We have drilling crews, pumping crews and pinning crews. This week I visited a pumping crew on the job in the Forest Hills area of Tampa.

sinkhole repair

As always, the engineering firm’s representative was on site to monitor the job. Travis from FGE (Florida Geotechnical Engineering) was happy to answer my questions, which was fortunate, because I can be quite inquisitive (a polite way of saying nosey). Jason, Helicon’s foreman, was also very helpful in answering my questions and helping me understand the process.

As I learned, the pumping crew is responsible for performing the procedure known as compaction grouting. First, drill points are marked around the perimeter of the home in 4-6 foot increments, and the drilling crew inserts sections of pipe into the ground using Helicon’s custom drill rig. The depth, spacing, and pipe angles are directed by the engineering specs for each individual job.

The material used for sinkhole repair is a custom grout mixture. Unlike standard concrete used for driveways and sidewalks, which contains gravel, grout is primarily made of sand. The resulting consistency is much more fluid than I expected. This characteristic is important, because the grout must be pumped under high pressure, and must permeate any loose soils in the surrounding area, effectively filling all voids.

Using specialized hydraulic equipment, the pumping crew monitors the volume and pressure of the grout pumped. As each level is filled, the drilling crew retracts sections of pipe four feet at a time. Essentially, they start at the bottom of the affected area and work their way up, ensuring all voids are filled. Meanwhile, Jason from Helicon observed the home for movement. It is very important that the pressures below ground are closely monitored to avoid the lifting the house from underneath, which can be just as damaging as the original sinkhole.

This process is repeated around the perimeter of the structure until certified complete by the engineering company, then a final report is generated and given to the homeowner. You can view a video of compaction grouting here.

Compaction grouting is one way to remediate a sinkhole. Helicon offers many additional services, including Underpinning, Injection Piers, Helical Piers, Chemical Grouting, and Pre-Construction Piers.