Abstract:

Sinkholes are becoming more often in many areas of Vietnam, causing serious damages on lives and properties. The main reason of many cases is human activities, especially the ones lead to rapid drawdown of groundwater level. The paper deals with characteristics of sinkholes in limestone areas, mechanism of sinkhole formation with a case study of Bang Lung town and Ngoc Phai commune, Cho Don district, Bac Kan province where a series of 5 sinkholes occurred in 2008. Herein, the main reason was defined as the water pumping for lead-zinc mineral exploitation. Sinkholes take place in fluvial sediments in a close relation to sand piping of sandy gravelly layer.