Experimental and Numerical Investigation of Sinkhole Development and Collapse in Central Florida

Abstract

The mechanisms of sinkhole formation, development, and collapse are investigated in this study using experimental and numerical methods. Sandbox experiments are conducted to understand how excessive groundwater pumping triggers sinkholes formation. The experimental results indicate that the change of hydrologic conditions is critical to sinkhole development. When seepage force increases due to increase of hydraulic gradient, clay and sand particles start moving downward to form a cavity. The confining unit is of particular importance because the cavity is first formed in this layer. Based on the conceptual model developed from the sandbox experiments, the Fast Lagrangian Analysis of Continua (FLAC) code and Particle Flow Code (PFC) are coupled to simulate the sandbox experiments. PFC was used to simulate particle movement in the sinkhole area, and FLAC is used for other areas. While the current numerical simulation can simulate the experiment results such as the sizes of the cavity and the sinkhole, the simulation capability is limited by the computing cost of PFC. More effort of model development is necessary in the future study. Introduction Sinkholes are a common geological feature of karst landscape in Florida, southeastern United States, and worldwide. In particular, cover-collapse sinkholes occur abruptly and can cause catastrophic damages such as death, injury, and property damage. In Florida, a Tampa resident vanished into a sinkhole that opened under his bedroom on a night in March, 2013. In the last several years, sinkholes have become Florida’s insurance disaster due to sinkhole collapse in urban areas. Covercollapse sinkholes also do severely damage buildings, drain farm ponds, damage roads, and wreck farming equipment, and lead to engineering and environmental problems (Beck, 1988). There is an urgent need to understand the mechanisms of sinkhole development and catastrophic collapse. Cover-collapse sinkholes occur in the soil or other loose material overlying soluble bedrock. The thickness and cohesiveness of the soil cover determine the size of a cover-collapse sinkhole. Figure 1 shows a typical process of cover-collapse sinkholes formation caused by excessive groundwater pumping. A karst aquifer is the Xiaohu Tao Geophysical Fluid Dynamics Institute, Florida State University, Tallahassee, FL, 32306 College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, Jiangsu, 210098, P.R. China, taoxiaohu_hhu@126.com Ming Ye Department of Scientific Computing and Geophysical Fluid Dynamics Institute, Florida State University, Tallahassee, FL 32306, U.S.A, mye@fsu.edu Dangliang Wang Department of Scientific Computing and Geophysical Fluid Dynamics Institute, Florida State University, Tallahassee, FL 32306, U.S.A, dlw9800@163.com Roger Pacheco Castro Department of Scientific Computing and Geophysical Fluid Dynamics Institute, Florida State University, Tallahassee, FL 32306, U.S.A, matbnt@gmail.com Xiaoming Wang Department of Mathematics and Geophysical Fluid Dynamics Institute, Florida State University, Tallahassee, FL 32306, U.S.A, xwang@fsu.edu Jian Zhao College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, Jiangsu, 210098, P.R. China, zhaojian@hhu.edu.cn