Buried sinkholes and rockhead features
Within the contractual tangle of construction projects, many of the numerous claims of “unforeseen ground conditions” relate to rockhead variations, especially where sound rock is found to lie deeper than had been anticipated. Some of the most extreme rockhead relief is found in mature karst terrains, and the largest individual features are buried sinkholes that have been filled with soil during natural evolution of the site, and now have little or no surface expression. These features may be known as either buried sinkholes or filled sinkholes; both terms are accurately descriptive, but the former is better as it invokes appropriate associations with buried valleys, with which many engineers are more familiar as a rockhead hazard. Very old buried sinkholes may be referred to as paleokarst features (James and Choquette, 1988); the fills in these are generally lithified, so that they have less influence on structural loading capacity except at very sensitive sites (though they may be critical as potential leakage paths from reservoirs). Younger features, with unconsolidated fills that may be the cause of ground subsidence, are sometimes also described as paleokarst as there is no absolute definition of the term.
KeywordsSurface Subsidence Ground Subsidence Subsidence Event Karst Terrain Soil Arch
Unable to display preview. Download preview PDF.