Florida’s geologic composition is very dense in mineral rich clays that absorb water and expand in size and volume. When these soils become saturated under a foundation, they build pressure and expand which can lead to concrete bulging and uneven floors. These soils can also shrink significantly in the dry season, leaving voids and holes under your home or structure.
Erosion occurs when soils or sediments are being altered or removed at a faster rate than they can be replaced, and is typically attributed to poor drainage conditions or a failed waterproofing system. This shifting or removal of soil particles will continue to transpire with time and eventually create voids or a “piping” effect under your foundation. Piping is the most severe form of erosion, where the soil is constantly being removed to create hollow pathways or tunnels along the length of the foundation. Eventually there will be a void created that is large enough to collapse, causing failures to surrounding soil layers and structures.
Poor site drainage
Sinkholes are extremely common throughout Florida, and are the result of erosion and water flow through limestone, carbonate rock, and salt beds that can naturally be dissolved by groundwater. When the limestone or salt deposits dissolve, cavities and holes are formed throughout the subsurface, which many times lead to sinkholes or depressions at the ground surface. Some sinkholes are minimal and take years to develop, whereas others can be catastrophic and fail abruptly. When these voids are created, it leaves no soil structure to support the weight of the soil or any structures above it. Failure occurs when the void or cavity collapses and this creates the “swallowing” effect that you see in many sinkhole failures. This can have a devastating effect if anyone is near a sinkhole that is partially failing or collapsed.
Un-compacted fill will eventually settle until it is at the soil's maximum density. We typically see differential foundation settlement issues with homes or buildings that were constructed on a “cut and fill’’ grade. The cut and fill process is employed when you need a level surface area in an area that is far from level, like the slope of a hill. Contractors will cut into the slope and use the cut material to build up a level grade for a foundation to be constructed. The problem is that it is extremely difficult to compact the fill material as well as it was compacted before it was disturbed. This typically results in disproportional settlement throughout the foundation, eventually leading to foundation cracking and buckling. The foundation crack or failure line will typically propagate along the length of the foundation section where the underlying soil changed from cut material to fill material.
Slope Stability/Excess Pore Water Pressure
Slope stability can become an issue when a load is applied at the top or along the length of a slope. This added load will surcharge the underlying soil and cause a wedge type failure if the loads exceed that of which the soil can handle. Every slope or retained soil mass has a certain failure line which propagates from the base up through the soil to the existing grade of the soil being retained. The soil between the slope grade and this failure line are referred to as the soil’s failure wedge. When dealing with retaining walls, the problem is often compounded due to the possibility of a wedge type failure and/or a structural failure of the wall due to buildup of excess water pressure. As pore water pressure infiltrates the soil mass behind the retaining structure, it will actually weaken the overall strength of the soil mass itself. This can lead to premature soil failure behind the retaining wall which will apply more load on the wall than it was designed to withstand.