Sinkhole stability chart for geotechnical investigation

Abstract

Sinkholes are a common geohazard in karst areas where soluble carbonate bedrock is present. Active groundwater flow causes internal soil erosion that creates cavities in the overburden soil layer. The subsurface cavity propagates upward due to the continuous erosion process, and ultimately, they reach to the ground surface, resulting in a sudden collapse. This cover-collapse type is generally a sudden event, particularly in the area where a thick cohesive soil layer is embedded. In this study, a sinkhole stability chart was developed to quantitatively evaluate the safety against the collapse-type sinkhole. Finite-element (FE) modeling was used to simulate the collapse of sinkhole. Field testing data collected from multiple sinkhole sites were used as input to the FE model. To simulate the progress of sinkhole activity, a number of different scenarios with varied size of cavity, strength of overburden soil were simulated, and the corresponding safety factors were determined. Even though each site has varied soil profile, a general trend of the safety factor was observed. The envelopes of safety factors (or equal-safety lines) were statistically determined by using a multivariate regression method. The chart that quantitatively evaluate the stability of sinkhole is used as a decision-making tool for further engineering investigation or mitigation.