The geotechnical properties, cyclic behavior, and liquefaction resistance of in situ fine coal refuse (FCR) have not been sufficiently investigated. This paper presents the characterization of static and dynamic geotechnical properties of in situ coal slurry samples. Representative coal slurry samples were taken from two coal slurry impoundments in the Appalachian coalfields in the USA. Standard penetration tests (SPTs) were conducted. Index properties, hydraulic conductivity, shear strength, and shear stiffness of the FCR were determined. The geotechnical properties of the representative FCR were found significantly dependent on the location and depth of the samples. However, the FCR samples were classified as soft and low plasticity silty sands to sandy silts. Cyclic direct simple shear (DSS) tests were conducted on representative samples prepared using slurry deposition method to evaluate the liquefaction resistance and cyclic behavior of FCR. The cyclic stress ratio – number of cycles required for liquefaction occurrence (CSR–N) curve for FCR was established. The cyclic resistance of FCR compared well with the empirical correlations for sand-like materials, though the stress–strain behavior and pore-water pressure generation exhibited clay-like behavior. Each cyclic DSS test was followed by a static shearing to assess the post-liquefaction shear strength of the FCR. Significant decrease in shear modulus and dilative behavior were observed after liquefaction.
