Numerical simulations of seismic and post-seismic behavior of tailings

Abstract

Several tailings impoundments have failed as a result of earthquakes in the last few decades. A majority of these failures were due to direct seismic loading, tailings liquefaction during shaking, or the post-seismic behavior of the tailings as it relates to the dissipation of excess pore-water pressures that were generated during shaking. Previous work has indicated that the UBCSAND model developed by Byrne et al. in 1995 is capable of simulating the cyclic simple shear testing response of low-plasticity tailings over a range of consolidation stresses and cyclic shear ratios. However, the ability of the model to simulate the dynamic and subsequent behavior of such tailings for other conditions, such those induced by shaking table tests, has not yet been evaluated. In this regard, previous work has shown that the main components of the UBCSAND model cannot realistically simulate some specific responses, including the post-seismic volumetric strains related to excess pore-water pressure dissipation. This paper presents numerical modeling results of the dynamic behavior of tailings from hard rock mines. It introduces a method for simulating their post-seismic behavior by including an updating scheme for the elastic moduli into the UBCSAND model. The results of cyclic simple shear testing, seismic table testing, and complementary experimental relationships were used to calibrate and validate the model with its new component. The simulated response of tailings during cyclic simple shear testing and for a complete seismic table test shows that the proposed approach simulates the experimental observations well. Level-ground, seismically induced liquefaction and post-seismic behavior of a 15 m thick tailings deposit are also simulated, leading to post-liquefaction settlements that are in agreement with empirical relationships.