Seismic stability of coal tailings dams with spatially variable and liquefiable coal tailings using pore pressure plasticity models

Failure of tailings dams can result in significant spill, loss of human lives, and damages to the environment and infrastructure. Cyclic loadings such as earthquakes and blasting are among the main threats to the stability of tailings dams. Seismic stability analyses of tailings dams are further challenged by the uncertainty and variability of tailings properties. In this paper, the influence of input motion characteristics and spatial variability in coal tailings (CT) properties on the seismic stability of a typical upstream-construction CT dam is investigated. Among the input motion characteristics, peak ground acceleration (PGA), equivalent number of cycles (ENC), and frequency content are the focus of this study. First, the applicability of two advanced constitutive plasticity models, PM4Sand and PM4Silt, in simulating the cyclic behavior of CT is evaluated and a suitable model is selected. The undrained shear strength of CT is modeled as a spatially correlated Gaussian random field. Six input motions — one blast and five earthquakes — are selected for the dynamic analyses. The dynamic analyses are conducted in co-seismic and then post-seismic stages. The seismic stability of the CT dam with uniform properties (i.e. uniform models) is compared to the stochastic models under the selected input motions. Post-seismic analysis was found critical for the stochastic models. This study highlights the importance of stochastic modeling and the consideration of spatial variability in seismic stability analysis of CT dams.