Geotechnical Investigation of karst sinkholes using an empirically-based CPT raveling chart

Abstract

Sinkholes are a major geohazard damaging transportation infrastructure in karst areas where soluble carbonate bedrock exists. This paper presents a study on the resistance characteristics of soil prone to internal erosion and subsequent sinkhole formation through subsurface investigation and data processing. The Cone Penetration Test (CPT) enables the identification of soil deposits indicative to sinkhole activity and internal soil erosion. The output of this study is a CPT-based chart that identifies internally eroded soils referred as sinkhole raveling. The chart is divided into multiple zones that represents different potential progressions of raveling. For construction of the chart, a database of subsurface testing in karst sinkhole-active sites was created. A filtering scheme was employed to remove “noise” signals and statistical methods were used to define the dividing-criteria lines to create each zone of typical resistance values in the various soil raveling progressions encountered. Implementation of the CPT-based soil raveling identification chart allows sinkhole vulnerability assessment that better understand the subsurface soil behavior in karst areas and provides a standardized tool to identify depths at which the soil may be experiencing raveling.