Seismic stability analysis of slopes stabilized with EPS-block geofoam

The use of lightweight fill, such as EPS-block geofoam, is a slope stabilization procedure that can be used to reduce the weight of the sliding mass and, thereby, reduce the driving forces of the sliding mass. This paper proposes the use of the horizontal slice method (HSM) for seismic stability analysis of slopes stabilized or repaired with EPS-block geofoam. © 2013 American Society of Civil Engineers

Three-Dimensional Seepage Simulation of a Tailings Storage Facility : A Case Study

Seepage response to tailings deposition and subsequent pore pressure condition characterization within the embankments of tailings dams are important in evaluating their performance under static and dynamic loading conditions. In this study, three-dimensional seepage response in a large tailings storage facility under tailings deposition and embankment raise was evaluated in the FEFLOW numerical platform. The simulation model considers interactions among the reclaim pond, deposited slurry, embankment, perimeter wells, and regional ground water table, analyzing both saturated and unsaturated flow conditions. The numerical model was first calibrated to the past and existing conditions, in which initial material properties were assigned based on field and laboratory testing, and then were adjusted through an iterative process until the pore pressure conditions in the model generally matched measured values. The documented piezometer measurements and pore pressure dissipation test results were used as calibration targets. The calibrated model was then used to project responses into the future for varied tailings deposition rates. The embankment crest and reclaim pond were evaluated in a series of raise steps over the time in a transient seepage analysis that accounted for consolidation-induced excess pore pressures under the increased overburden stresses. The effects of the raise rate, depositional scheme, and material water storage capacity on the projected pore pressure conditions were also evaluated. The results indicate that the numerical model can predict seepage response and pore pressure conditions reasonably well. The outcomes of such models provide more insights into the seepage performance of the tailings storage facilities. Additionally, pore pressure responses can be used in the framework of performance-based design to assist geotechnical engineers in evaluating embankment stability and to better inform decision-makers by reducing uncertainties. Such studies highlight the importance of using numerical models to evaluate the seepage response in tailings storage facilities. By providing a better understanding of the seepage performance, these models can help mining companies to identify potential risks and improve their management practices, ultimately leading to safer and more sustainable mining operations.Non UBCUnreviewedOthe

Seismic Evaluation of a Tailings Dam Using Uncoupled and Fully Coupled Soil Constitutive Models

The Henderson Tailings Storage Facility (TSF) is an active facility located near Parshall, Colorado, consisting of two dams – 1 Dam and 3 Dam. The upstream method of construction has been used for tailings deposition since the mid-1970s. This paper presents the results of the seismic evaluation of 1 Dam using multiple constitutive modeling methodologies: an uncoupled Mohr-Coulomb approach and a fully coupled critical state-compatible PM4Sand/Silt approach. The analyses were completed to study the seismic response of the tailings embankment under the Maximum Design Earthquake (MDE) with a return period of 10,000 years. The numerical analyses showed that the results of the fully coupled, effective stress PM4 models were generally consistent with the uncoupled Mohr-Coulomb models. The PM4 models have the capability to estimate the generation of excess pore water pressure and onset of soil liquefaction during the application of the input ground motion. Subsequent zones of tailings materials that were prone to soil liquefaction or strength loss were identified based on two criteria: 1) excess pore water pressure ratio; and 2) shear strain in the PM4 modeling. This study provides valuable insights into the methods used to estimate seismic response of the Henderson TSF and highlights the importance of using properly calibrated advanced constitutive modeling methodologies to capture the complex response of tailings materials under seismic loading. The fully coupled models were capable of capturing the hysteretic soil response, including stress-strain response and accumulation of plastic shear strains, providing confidence in the predicted modes of deformation and informing the design and management of the facility.Non UBCUnreviewedOthe