Seismic deformation analysis of Tuttle Creek Dam

Stark, Timothy D.; Beaty, Michael; Byrne, Peter; Castro, Gonzalo; Walberg, Francke C.; Perlea, Vlad; Axtell, Paul J.; Dillon, John C.; Empson, William B.; Mathews, David L.

doi:10.1139/t11-107

Cited by 16 publications

(9 citation statements)

References 12 publications

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“…The average residual strength ratio obtained was 0.11, with no variation seen based on vertical effective stress observed. This result is consistent with the residual strengths measured with a vane in other low plasticity tailings and natural soils (Castro 2003;Stark et al 2012).…”

Section: Laboratory-scale Shear Vanesupporting

confidence: 90%

Stability of a proposed steepened beach

Reid¹,

Boshoff²

2015

Proceedings of the 18th International Seminar on Paste and Thickened Tailings

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Existing topography at an operational lateritic nickel facility is such that if the tailings beach slope could be increased to 1-2% for approximately one year, significant costs related to wall building could be deferred. As additional thickening capacity would require significant capital expenditure, polymer treatment technologies have instead been investigated. As part of the trial process for polymer treatment, the stability of the potential steepened beach was assessed. While beach slopes of the range targeted here would, for many materials, be unlikely to produce an unstable landform, lateritic nickel tailings develop very low dry densities, consolidate slowly, and contain hypersaline pore fluid. This combination results in a lower resistance to slope instability, all else being equal. Further, polymer treatment technologies, while providing benefits through rapid dewatering and beach slope development, have been shown to result in an increased brittleness for some materials. Laboratory characterisation of the polymer treated material was first undertaken, by means of (i) monotonic, cyclic and post-cyclic simple shear testing, to assess the potential for strength loss of the material, (ii) laboratory-scale shear vane testing, to estimate residual shear strength, and, (iii) settling and consolidation tests, to provide input to consolidation modelling. A consolidation model of the proposed steepened beach was then developed. Outputs from this model were used as the basis for infinite slope stability analyses on a variety of scenarios. It was found that over the one year planned deposition period, beach slopes of 1.5% or less are likely to result in a satisfactory factor of safety (FS) for the steepened beach. 2 Previous relevant studies 2.1 Steepened beach stability A number of previous studies have been undertaken to assess the expected stability of proposed unconstrained tailings beaches, most of which were developed from thickened tailings deposition. Each of

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Section: Laboratory-scale Shear Vanesupporting

confidence: 90%

Stability of a proposed steepened beach

Reid¹,

Boshoff²

2015

Proceedings of the 18th International Seminar on Paste and Thickened Tailings

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“…Also, the resulting effective stress is slightly lower than the CSRL also explains failure occurring after earthquake shaking ceases. Stark et al (2012) use a value of r u,seismic of 0.7 for assigning a liquefied strength for the seismic retrofit of Tuttle Creek Dam for a number of reasons including the sand FS Liq trend line in Figure 9 becomes asymptotic to unity (1.0) at r u,seismic values greater than or equal to 0.7. In addition, the range of sand trend lines in Figure 9 reach a FS Liq of unity at an r u,seismic of about 0.6, which is in better agreement with the CSRL for the Sand Slope and Sand Toe in Figure 15 and supports assigning a liquefied strength to these two zones.…”

Section: Critical State Line Representationmentioning

confidence: 99%

Pore-water pressure accumulation during closely spaced earthquakes: Fundão Tailings Dam

Stark

Lin

Gimenes³

2022

Applied Earth Science

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This paper focuses on pore-water pressure accumulation in loose sandy tailings during three (3) earthquakes within four minutes and the accompanying decrease in effective stress to assess the dynamic stability of the Fundão Tailings Dam, which failed on 5 November 2015. Results of laboratory cyclic direct simple shear tests are used to illustrate the accumulation of pore-water pressures with closely spaced low-level cyclic events. The seismically-induced pore-water pressures in the loose sands below the left abutment downstream slope and setback area are used to estimate the decrease in factor of safety with time until failure occurred within 20-30 minutes of the earthquakes. Field cone penetration and standard penetration test conducted prior to the failure are used to calculate the factor of safety against liquefaction to estimate pore-water pressures generated during the fore, main, and aftershocks in the sandy tailings. The effective stress stability analyses utilise a liquefied shear strength ratio for the sand tailings below the left abutment downstream slope and toe of the plateau because the sand tailings reached the critical state condition due to a reduction in the effective stress.

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“…However, for nonsymmetric cyclic loading conditions, the UBCSAND model predicts a less amount of damping compared to the damping of soils observed in laboratory tests [20]. As additional damping, 1% of the critical damping (i.e., damping ratio 0.01) was assigned to the tailings material zones whose constitutive behaviour was represented with the UBCSAND model (see [54,55]). On the other hand, 3% of the critical damping was assigned to the moraine, rockfill, and filter zones where the MC model was utilized (see [54,55]).…”

Section: Dampingmentioning

confidence: 99%

Numerical Analyses of Earthquake Induced Liquefaction and Deformation Behaviour of an Upstream Tailings Dam

Zardari

Mattsson

Knutsson

et al. 2017

Advances in Materials Science and Engineering

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Much of the seismic activity of northern Sweden consists of micro-earthquakes occurring near postglacial faults. However, larger magnitude earthquakes do occur in Sweden, and earthquake statistics indicate that a magnitude 5 event is likely to occur once every century. This paper presents dynamic analyses of the effects of larger earthquakes on an upstream tailings dam at the Aitik copper mine in northern Sweden. The analyses were performed to evaluate the potential for liquefaction and to assess stability of the dam under two specific earthquakes: a commonly occurring magnitude 3.6 event and a more extreme earthquake of magnitude 5.8. The dynamic analyses were carried out with the finite element program PLAXIS using a recently implemented constitutive model called UBCSAND. The results indicate that the magnitude 5.8 earthquake would likely induce liquefaction in a limited zone located below the ground surface near the embankment dikes. It is interpreted that stability of the dam may not be affected due to the limited extent of the liquefied zone. Both types of earthquakes are predicted to induce tolerable magnitudes of displacements. The results of the postseismic slope stability analysis, performed for a state after a seismic event, suggest that the dam is stable during both the earthquakes.

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Seismic deformation analysis of Tuttle Creek Dam

Cited by 16 publications

References 12 publications

Stability of a proposed steepened beach

Stability of a proposed steepened beach

Pore-water pressure accumulation during closely spaced earthquakes: Fundão Tailings Dam

Numerical Analyses of Earthquake Induced Liquefaction and Deformation Behaviour of an Upstream Tailings Dam

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