Dynamic effective stress analysis of a centerline tailings dam affected by subduction earthquakes – Case Study

We present a case study that evaluates the seismic performance of a centerline tailings dam in the South American Andes through dynamic effective stress analyses with advanced constitutive models. The seismic demand at the dam site was evaluated through a probabilistic seismic hazard analysis (PSHA), which derived in deterministic and probabilistic-based seismic design criteria. The PSHA results were used to select spectrally matched ground motions for the subsequent dynamic analyses. The centerline tailings dam is planned to be raised in stages to 90 m high, which was considered in establishing the initial stresses and pore pressures before seismic loading. The material properties were based on a large geotechnical characterization program considering the mine tailings to be stored in the deposit and other critical dam components. The dynamic analyses were performed using the UBCHYST constitutive model for materials that are not expected to generate significant excess pore pressures and the PM4Silt constitutive model for the materials that may generate excess pore pressures due to cyclic loading. The results show the deformation patterns in the centerline dam, after the seismic loading, are significantly affected by the mine tailings presence. The results are useful to plan the overall operational management of the tailings facility.