Sinkhole Experiment

Madrid Engineering Group, Inc. is currently developing a bench top scale model to complete experiments related to sinkhole activity in central Florida. This model will be used to examine the relationships between soil density, clay content and the verticle hydraulic gradient as factors in the formation of a sinkhole.

It is understood that a sinkhole starts as a void or cavity within the limestone layer underlying the soil unit, as shown in Figure 1A. Progressively, the overlying soil begins to fail or "ravel" into the void (1B). The void then begins to propegate upward through the stratum (1C), causing a depression in the ground surface (1D), or alternatively, a total collapse (not shown). It is postulated that, because the clay is cohesive in nature and has a low permeability, sinkhole formation is more difficult for clay than it is for sand. Also, dense sand, having a higher shear strength, will resist sinkhole formation more than would a loose sand. Finally, many engineers and scientists believe that the groundwater gradient is the most important factor in sinkhole causation. The testing is to be conducted in a specially fabricated apparatus that will allow researchers to view the sinkhole formation as it happens through a clear front panel.

Andrew Madrid graduated from the University of Florida in May with a bachelor's degree in chemical engineering and will be doing research this fall at LSU toward his PhD.