Problems with Expansive Pyritic Shales in East Tennessee

Economic costs of damage due to expansive soils and rocks in the U.S. has been estimated at $6 to II billion annually, which is more than the combined annual damage costs of earthquakes, floods, and tornadoes (Nuhfer et aI. 1993). Considerable research and money have been directed towards controlling and preventing damage from these hazards, while relatively little attention has been given to damage caused by expansive shales. Expansive shale problems have been encountered in Norway, Canada, Sweden, Pennsylvania, West Virginia, and Ohio. However, this project focuses on a particular type of shale, called Sevier shale, which is common in East Tennessee. Sevier shale contains iron disulfide (FeS2) or pyrite, also known as "fool's gold." Pyrite can oxidize to form sulfate minerals, and in the presence of calcite, can produce gypsum crystals. The volume increase and accompanying heave pressures can cause extensive structural damage, collapse of culverts, failure of retaining walls, and mine floor deformation. In forming effective remediation and/or prevention practices for these situations, it would be useful to examine typical on-site recommendations and identify those which appear most successful. Therefore, this project examines several case studies in East Tennessee, evaluates testing procedures that predict expansion potential, and identifies the most effective management practices.