Development of Methods to Predict the Dynamic Behavior of Fine Coal Refuse: Preliminary Results from Two Sites in Appalachia

Over the past 40 years, approximately 15 mine tailings dams have failed worldwide as a result of earthquake shaking. Methods to analyze the dynamic response and liquefaction resistance exist for soil, but fine coal refuse, including slurry that is hydraulically placed behind the dike, is inherently different than soil. Therefore, a research study is underway to understand and predict the dynamic behavior of fine coal refuse. To date, field testing has been performed at two coal refuse impoundments in eastern Kentucky. Laboratory resonant column testing was used to measure modulus reduction curves (i.e. the relationship between shear modulus, material damping, and shear strain) of undisturbed specimens. Field standard penetration testing, seismic cone penetrometer testing, and geophysical surface wave testing was performed to measure blow count (N₆₀), cone tip resistance (q_c), and shear wave velocity (v_s). Field vane shear data were acquired to correlate peak and residual undrained shear strength to q_c. Preliminary results of this study include development of modulus reduction curves for fine refuse and development of methods to estimate peak and undrained shear strength based on in situ CPT testing. Future results will include correlation of overburden-corrected field data to cyclic resistance ratio (CRR) to predict liquefaction resistance.