Investigation of the Effect of Waste Rock Inclusions Configuration on the Seismic Performance of a Tailings Impoundment

Waste rock inclusions can improve the seismic response of tailings impoundments, mainly through their reinforcing effect. Preliminary simulations of reinforced impoundments illustrated how such inclusions can be beneficial for impoundments subjected to earthquake loadings. This paper presents new results of numerical analyses of the seismic performance of a tailings impoundment with different configurations of waste rock inclusions (i.e. various widths and center-to-center spacings). The simulations were conducted using two base ground motion records, one characterized by high frequencies typical of the east coast of North America and the other characterized by low frequencies typical of the west coast. Both ground motions were scaled to obtain the same Arias intensity and peak horizontal ground acceleration. The seismic response of the tailings impoundment was evaluated using (1) the deformation of the downstream slope at the end of shaking, with respect to the energy content and predominant frequency of the applied ground motions, as well as the configuration of the inclusions, (2) the critically displaced volume of tailings at the end of shaking. A total of 108 dynamic numerical simulations were conducted and evaluated. The main results presented here show that waste rock inclusions can enhance significantly the seismic performance of a tailings impoundment when appropriate configurations are considered. These also indicate that the low frequency ground motions tend to produce larger deformations and greater critically displaced volumes of tailings in comparison with the high frequency ground motions. These simulations results provide preliminary guidelines to determine optimum configurations of waste rock inclusions for different seismic loadings.