Sinkholes at the Dead Sea have threatened tourists and forced Israeli (and perhaps Jordanian)authorities to close various facilities and cancel development plans to avoid these geologic hazards. These are not your typical Karst sinkholes. According to a recent AP article, they are caused by the erosion of salt deposits by fresh water as a result of the lowering of the water level. This is a human caused phenomenon as current size of the Dead Sea is just 1/3 of its size in 1960 since water has been diverted from the Jordan River, its main tributary to be evaporated for its phosphates. At the end of the article is an interesting note that the World Bank is currently evaluating a proposal to replenish the Dead Sea by digging a $15 Billion canal from the Red Sea, about 100 miles away. (Photo by urban_hipster)
The site for the new Harrison County Hospital, approximately 25-miles west of Louisville, Kentucky had 15 sinkholes formed by limestone dissolution, a geomorphologic process referred to as Karst topography. There were a number of geotechnical engineering and geological engineering challenges associated with the characterization, excavation, backfilling, foundation engineering and other mitigation measures as described by Peggy Hagerty Duffy, P.E. in her article entitled “Karst and Complications” in the August 2008 issue of Civil Engineering Magazine (Duffy, 2008b).
Mitigation measures for the sinkholes included use of graded filters with geotextiles, careful inspection of rock socket foundations along with pilot holes and careful geotechnical inspection throughout the construction process. One particularly interesting aspect of the project is that several of the sinkholes were used as drainage facilities to receive surface water runoff. Read on for a summary of this interesting article. (Photo of sinkhole in Karst Topography being used as a drainage feature, from Duffy (2008b), Civil Engineering Magazine)