Call Chris 813 545-5263
Sinkhole Formation - Sinkholes occur due to the nature of the limestone bedrock in Florida, which is primarily calcium carbonate and is subject to a gradual dissolution in the ground water. This process originates as rain dissolves carbon dioxide from the air, forming a very weak carbonic acid. As rainwater infiltrates into the ground, it also may pick up organic acids and additional carbon dioxide. The very weakly acidic infiltrating water. Because this reaction is fairly rapid, most of this corrosion/dissolution takes place at the surface of the limestone. Accordingly, loose/soft conditions are often found at the soil-limestone interface. The infiltrating water may follow preferential paths toward fractures or porous zones in the limestone, creating more dissolution localized areas. In addition, portions of the limestone may be more susceptible to weathering processes than other to composition and physical variations, which may take place on a regional as well as local scale. Further, it should be noted that the limestone in some area has been exposed and subject to weathering processes in the geologic past, resulting in an irregular surface with holes, depressions and pinnacles that may vary tens of feet or more over relatively short distances. Low spots in the limestone surface may contain soft sediments that never consolidated due to bridging of the overlying soils across the low spot. Accordingly, soft zones at the soil-limestone interface and variations to the depth of limestone are often evident in soil borings. Some geologists refer to this condition as epi-karst. Different types of sinkholes are thought to occur. One type is a buried ancient or relic sinkhole, which is a sinkhole that occurred in the geologic past and has been filled with sediment that often is organic stained or organic. A relic sinkhole may be stable or may show indications of re-activation. Another type of sinkhole is more dramatic. It involves formation of a sudden circular depression at the ground surface as the result of rapid erosion of soil into a void or cavity in the limestone bedrock or collapse of the roof of a cavern near the surface of the rock. These collapse events are often triggered in periods of heavy rainfall following brought conditions, and are due to a reduction in buoyancy support/increase in overburden soil weight due to a low ground water table, weight added due to wet soil above, and an increase in infiltration into the limestone, which can tend to erode the soils into voids. Similarly, installation and/or operation of a well can draw down the ground water and initiate groundwater flow, also triggering a collapse sinkhole. In a third type of sinkhole affect, gradual subsidence of the land surface may occur as the follows dissolution of the limestone surface or gradually slumps or erodes into a void. The very gradual, sinkhole-related subsidence process can result in slowly appearing settlement distress in an overlying structure. Therefore, structural damage is not likely to occur from this process. Structural damage is defined as damage to the structure such that repair measures are necessary to reestablish the load supporting capabilities of the structure sufficient to satisfy building code requirements. However, many non-sinkhole related subsurface conditions (compressible organic deposits, for example) as well as structural conditions and construction material behavior can create similar distress. In fact, multiple causes that may have contributed to development of the observed distress in the structure often are identified. The soil conditions capable of resulting in differential movement of the structure and material behavior are often more readily identifiable and their likelihood of causing distress more directly evident or quantifiable than the process of sinkhole activity. It should be noted that the statutes dealing with insurance claims refer to damage caused by 'sinkhole activity' rather than a sinkhole, which has, in our experience, further enabled claims to be made when minor settlement has occurred.) The contribution of non-sinkhole related conditions to the appearance of the distress can obscure any affects of the sinkhole activity and makes the determination of whether any subsidence-related settlement distress has occurred as the result of sinkhole activity difficult to discern, should indicators of sinkhole activity be present in the borings, especially given the legal context of sinkhole activity. Chris is the sinkhole home buyer © Copyright 2010 Langee. All Rights Reserved |
|---|
