Experimental study on sinkholes: Soil-groundwater behaviors under varied hydrogeological conditions

Sinkholes have been one of the major geohazards in karst terrain and have resulted in loss of human life, as well as significant civil engineering infrastructure. Approximately 20 % of the United States is underlain by karst terrain formed from the dissolution of soluble rocks, and is susceptible to a sinkhole hazard. Particularly, Texas, Florida, Tennessee, Alabama, Missouri, Kentucky, and Pennsylvania are known as sinkhole states. Surprisingly, the understanding of sinkholes is still poor in geotechnical engineering. This paper presents and discusses a preliminary study on the mechanism of Florida's sinkholes that are triggered by groundwater flow. A physical soil-groundwater model was devised, and multiple tests were conducted under different hydrogeological conditions (e.g., with/without aquitard and overburden soil thickness). Groundwater at multiple locations was monitored during the sinkhole-simulation process so that integrated soil-groundwater behaviors could be investigated. It is found that groundwater responds before the surface collapse (showing a cone of depression); thus, a pattern change of groundwater flow can be used as input to pre-detect a sinkhole. In addition, having a clayey sand layer within sand shows a significant influence that includes a rapid change of groundwater flow in the sinkhole process and a larger surface sinkhole.