Responses of cover-collapse sinkholes to groundwater changes: a case study of early warning of soil cave and sinkhole activity on Datansha Island in Guangzhou, China.

In karst areas of Quaternary sediments, fissures and solution channels through soluble rocks provide unseen conduits for the vertical movement of surface water into the underlying karst aquifers. This downward flow may also transport overburden material, which can result in the formation of soil caves and ground loss called cover-collapse sinkholes. Because of the concealed development of such soil caves and generally complicated geological conditions, the prediction of soil cave development and sinkhole activity is far from perfect. This study focused on the early warning of soil cave and sinkhole development by monitoring groundwater-level decline. Based on the improved Terzaghi loosening pressure theory and using excess pore water pressure, two types of critical groundwater-level decline are discussed. The first, denoted as ∆₀, is the critical groundwater-level decline related to soil cave formation and evolution; the second, denoted as ∆H_T, is the critical groundwater-level decline related to soil cave roof collapse. This method of groundwater monitoring for the early warning of soil cave and sinkhole development is currently being applied on Datansha Island in Guangzhou, China. [ABSTRACT FROM AUTHOR]