Use of the Cone Penetration Test for Geotechnical Site Characterization in Clay-Mantled Karst

Adapted for use as a mechanical soil exploration device in the 1930's in Holland, the cone penetrometer has evolved into an electric instrument capable of collecting essentially continuous data in the soil profile in the forms of the tip resistance, sleeve friction and pore water pressure. It provides an essentially continuous profile of information and is capable of identifying abrupt changes in soil stiffness and strength. The production of a typical cone rig makes the level of information comparable to that obtained by geophysical methods, but has the advantages of direct exploration. Although it has advantages over the widely accepted standard penetration test and geophysical methods, the cone penetration test has not been widely used for geotechnical characterization in clay-mantled karst. This paper discusses the relative advantages and disadvantages in the application of the cone penetration test to geotechnical site characterization in karst. It presents cone penetration test data collected at two project sites in deeply weathered, clay-mantled karst of east Tennessee and examines the karst conditions as interpreted from the cone penetration data and the anticipated impact of those conditions on project design and construction.