Florida Foundation and Sinkhole Repair Methods
Deep Compaction Grouting
For over 50 years Deep Compaction Grouting has been utilized to correct soil settlement problems in both new and existing structures. This type of sinkhole repair is widely used by many geotechnical engineering firms and is commonly recommended in many engineering reports.
Compaction Grouting is a process of injecting a low mobility cement grout mixture under high pressure, through a number of angled and vertical injection points around your home. The objective is to fill the voids beneath the structure and increase the density of the soil layers which supports your house thus remediating the sinkhole activity.
The first step is to install steel grout casings around your home using a drill rig. The casing is installed to the maximum treatment depth using the rotary wash method, which allows the casing to be snugly seated a few feet into limestone. Once all the injection pipes are installed, each point is flushed to ensure a clear path for the grout to flow. At this point the grout is ready to be pumped by connecting the concrete pump to the pipes.
As the grout is pumped through the steel casing the casing is slowly extracted in controlled incremental lifts, usually two to five feet at a time. In the first few treatment zones the compaction grout spreads, sealing the limestone surface. This creates a blanket over the limestone which will keep the upper soils from further raveling through the fissures in the limestone cracks. Then as higher pressures are reached, the casing is lifted and pumping resumes again at the new level. The process will continue at this level until pumping has reached higher pressures again. Then the casing is lifted more and pumping continues at the next level.
Grout is pumped through the casing creating a dense zone – compacting the soils around it and increasing soil density in the targeted treatment areas until the area is fully stabilized. As injection points are finished, the grouting process moves on to the next point and continues there, point by point all the way around the property until all the injection points have been fully pumped.
The structure is monitored continuously for movement by using pressure gauges located between the concrete pump and the injection pipe, transits, and laser levels. This allows the installation crew and the monitoring engineer to determine the effectiveness and extent of the compaction work.
The final site cleanup happens as all casing is removed from the property and landscaping is restored.
Sinkhole Underpinning or Steel Piers
Underpinning has many different names such as Steel Piers, Underpins, Push Piers, Resistance Piers, Pin Piles, Piles and Mini Piles. While the names and types of piers may vary, they all refer to a segmented structural steel piling which is hydraulically advanced to limestone.
Engineers recommend underpinning designs to stabilize the perimeter of your home or business which may have sustained damage from any number of factors such as; organic soils, shrink and swell clays, poor compaction, improper footer embedment, erosion, or sinkhole damage. In most cases the structure can be lifted back to a level position. Underpinning’s main function is the support and stabilization of the structure’s load by transferring the weight of the structure off the weaker soils and on to the underpins.
Another important consideration in choosing underpinning is the type of steel which is being used. Since underpins are relatively easy to make, many companies produce their own in their “backyard” or buy inferior materials from places like China. This means the strength of the steel could be equal to fence post material. Always look for the schedule of the steel, the higher the number the schedule is, the stronger the steel. Champion’s schedule 80 steel is the strongest in the business and can hold up to 120,000lbs per pier. Underpinning can be a great repair if you remember 3 keys factors; make sure the right materials are being used, they are installed correctly, and your limestone is attainable.
Underpinning is one of the two most common types of structural pilling for residential foundation and sinkhole repair in use today.
Chemical Grouting is a newer sinkhole repair method which injects a polyurethane foam in low viscosity liquid form at low pressure into cohesionless soils. Most geotechnical Engineers use Chemical Grouting for the purpose of consolidating the loose and sandy soils which are above the treatment zones from the compaction grouting processes.
This procedure can often also be used around pool decks, walkways, underneath foundation slabs, and re-leveling of foundation slabs. The entire Chemical Grouting process typically takes anywhere between1 to 2 days to complete.