Soil failure in subsidence sinkholes
The vast majority of ground failures within karst terrains are due to the erosion, transport and failure of the soils that overlie cavernous bedrock. Dissolution and removal of enough limestone to form a cave of significant size requires geological timescales that cover tens of thousands of years. In contrast, a comparable volume of soil can be removed during a single rainstorm, where there is a stable, old karstic cave somewhere beneath that can accept the displaced material. The rock left over a limestone cave is generally strong enough to stand for very long periods of time. In contrast, a soil arch over any void is inherently unstable, and may fail immediately or during a subsequent rainstorm. For these two reasons, soil failures are much more common than rock failures in karst. The chances of an engineered structure being damaged or destroyed by sinkhole development due to soil failure, during its design lifetime, are orders of magnitude greater that the chances of rock collapse.
KeywordsPore Water Pressure Soil Cover Soil Cavity Karst Terrain Soil Arch
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