Abstract:
For over fifty years TDOT has been challenged by slope instabilities in the Pennington Shale Formation, most notably along several sites in the vicinity of I-40, Roane Co. (Rockwood Mtn.) site. This formation is exposed in Tennessee within the Cumberland Plateau and Valley\Ridge geophysical provinces. The material weathers then loses strength and becomes unstable in natural slopes, excavation cuts, and when used in embankment fills. TDOT has observed some measure of success by drilling horizontal drains to facilitate drainage and managing the slope movement risk to a tolerable level. Stone buttresses have also proven effective, but this application almost always requires a temporary road closure. Modern transportation networks have ever higher traffic volumes, and road closures required to install most stone buttress are often impractical for several reasons that will be explored. Recent advances in drilling equipment and methods are making stabilization techniques using drilled ground anchors more advantageous than building stone buttresses. This document\presentation will provide an overview of ground anchor stabilization applications and then contrast the ground anchor application of two project sites currently under construction at I-40, Roane Co. (Rockwood Mtn.) and SR-56, Grundy Co. (Beersheba Springs, TN) against stone rock buttress applications that have been built along other locations within Tennessee where the Pennington Shale formation has caused slope movement.