CHARACTERIZING SINKHOLE SEDIMENT BASIN PROPERTIES ON CAVE HILL, GROTTOES, VIRGINIA

Sinkholes are normative features that are characteristic of karst terrains which are formed as water dissolves soluble rocks leaving behind concentric voids. Cave Hill, in the Town of Grottoes, Virginia, exemplifies a karst region that contains numerous sinkholes, making the location appropriate for a study area. Cave Hill is dominated by the Conococheague formation, a microcrystalline limestone, interbedded with dolostone and sandstone of Cambrian age.

In this study we apply LiDAR (Light Detection and Ranging) with SLAM (Scanning Localization and Mapping) technology to construct georeferenced dense point clouds to observe the geometry of three sinkholes on Cave Hill that exhibit various sizes, relative location, and depths. Additionally, soil samples were collected from each sinkhole to analyze their bulk density, organic carbon content, and particle size distribution to determine each individual sinkholes’ difference in strength, stability, and bearing capacity.

It was observed that as the length and depth of sinkholes increased, there was a prominent climb in bulk density towards the epicenter. Using a laser diffraction particle size analyzer, it was determined that SGC1, the largest and deepest sinkhole, was primarily coarse loam and silt with the furthest sample sites being silty clay. SGC2, a large sinkhole with a shallow basin, was primarily coarse loam and silt. SGC3, the smallest and shallowest sinkhole, had various compositions across the transect with sites being mostly coarse loam furthest away from the center, then fine loam, and fine clay near the center. Lastly, a single factor ANOVA test was conducted to determine the mean variation of organic carbon between sample sites; the p-value of 0.001184 (α = 0.05) indicates there is a difference in organic carbon content between the sinkholes. These results highlight subsequent patterns and methods that can be employed to examine sinkholes which are valuable for structural engineering endeavors, collapse mitigation, as well as understanding hydrogeologic sediment movement.