In Situ Seismic Investigations of Coal Tailings

Catastrophic tailings dam failures have resulted in significant social, economic, and environmental losses. The geotechnical properties of coal tailings have been investigated in the past using reconstituted samples or relatively undisturbed samples. To realistically assess the stability of coal tailings dams under dynamic loadings, there is a need to determine the in situ properties of coal tailings using non-destructive field testing. In this study, seismic refraction survey and multichannel analysis of surface waves method are performed in two coal tailings impoundments in the Appalachian coalfields in the USA. Shear wave and compressional wave velocities of coal tailings are determined based on the field data. Young's modulus, shear modulus, and Poisson's ratio that are critical in understanding the stress-strain relationship of coal tailings are estimated. The Poisson's ratio of the unsaturated fine coal tailings is determined to be 0.39. The Young's modulus of the soft fine coal tailings for the inactive site is higher than that for the active site (i.e., 65 MPa versus 35 MPa). The small-strain shear modulus of the fine coal tailings is determined to be in the range of 10 to 50 MPa. The parameters derived from these seismic investigations contribute to the scarce database of geotechnical properties of coal tailings and can be applied to future stability assessment of coal tailings dams.