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A nanosecond Nd:YAG laser was used to study the laser ablation of aluminum foil in the phase explosion regime at a laser intensity range of 0.63–3.61 × 10 12 W / cm 2. Laser ablation and plasma characteristics were studied using microscopic ablation crater images, plasma emission spectra, and plasma plume images. Measured plasma density using a Stark width of Al I (396.2 nm) showed a strong linear correlation with crater size, with a Pearson correlation coefficient (r) of 0.97. To understand the origin of this linear correlation, plasma temperature was estimated using Bremsstrahlung emission from 512 to 700 nm. The estimated plasma temperature and aspect ratio of the plasma plume were negatively correlated, having r = − 0.76. This negative correlation resulted from a laser-plasma interaction, which heated the plasma and increased its hydrodynamic length. The percentages of laser energy used for plasma heating ( E p / E L ) and Al foil ablation ( E Al / E L ) were estimated from plasma temperature. Increased E Al / E L , such as crater size, with increasing laser intensity, confirms that greater mass ablation is the fundamental reason for the strong linear correlation between crater size and plasma density. [ABSTRACT FROM AUTHOR]

Due to the logistical challenges associated with using nuclear densitometers at remote sites, the industry is seeking an alternative method to determine the in situ density and moisture content during the construction of filtered tailings facilities. This study aims to investigate the impact of salinity on soil electrical properties and evaluate the feasibility of using an electrical density gauge (EDG) to measure the in situ density and moisture content of saline filtered tailings. The results indicate a dependence of electrical measurements on salinity. To develop procedures for soil calibration models of filtered tailings, standard Proctor tests were first conducted using Devon silt. These procedures were then applied to the filtered tailings to establish correlations between electrical properties (dielectric constant, impedance, capacitance-to-resistance ratio) and physical properties (density and moisture content) at varying salinities. It is suggested to build the soil calibration model using an EDG within a water content range of 10% to 18%. Furthermore, the effectiveness of the developed calibration models has been validated, demonstrating the applicability of the EDG instrument for filtered tailings in a saline environment. However, applying the salinity correction is crucial when the sample has a considerably different salinity than the calibration model. [ABSTRACT FROM AUTHOR]

Historically, tailings facilities have been designed primarily with consideration of the mine's active life. This is problematic, as the lifespan of a tailings dam may far exceed the life of the mine. Over time, it is expected that these structures will transform into a mine waste structure and then eventually a landform. In Alberta, Canada, dam owners can submit a decommissioning, closure, and abandonment (DCA) plan and completion reports to apply for the facility to be de-registered as a dam. If successful, the structure would be considered a solid waste structure and may be reclassified and regulated as a mine waste dump. The Alberta Energy Regulator expects DCAs to be accompanied and supported by risk assessments that consider long-term physical failure modes, including failure modes that may not be applicable during operations, in accordance with Manual 019. To help support the process of de-registering a tailings dam, a risk management tool, referred to as a Generalized Failure Modes Effects (G-FMEA) framework, was developed and presented in the Journal of Minerals in the Special Issue Tailings Dams: Design, Characterization, Monitoring, and Risk Assessment. The G-FMEA was designed to be used for assessing risks of an external tailings facility in closure, with the goal of assessing the long-term risk of geotechnical failure to support the process of de-registration. In Alberta, a number of tailings dams are undergoing closure and reclamation activities. This paper applies the developed G-FMEA framework to an oil sands tailings dam in Alberta to demonstrate the application of the framework. The paper assesses two specific failure modes of two different elements, including clogging of the drains and surface erosion of the berm. The failure modes are assessed over different timescales to demonstrate how the consequence, likelihood, and risk rating may change over time. The results of this process are discussed in the context of the potential for the facility to be de-registered as a dam. [ABSTRACT FROM AUTHOR]

Abstract: Laboratory freezing experiments were conducted to evaluate the feasibility of using cyclic freeze–thaw to enhance the surface stability of coal mine fine tailings. Undrained shear strength increased from non-measurable to 10 kPa after five cycles of freeze–thaw in tailings samples with initial moisture contents of 84% and 102%. Cyclic freeze–thaw also significantly dewatered the tailings samples. Decanting the melt water after each thaw reduced the water content of each sample by approximately 50%. A large scale one dimensional freezing test was also conducted to determine the advance of frost within the fine tailings and to understand how moisture migrates as the tailings freeze. Water was attracted to the freezing front from tailings ahead of the advancing front, decreasing the moisture content within the still unfrozen tailings. As the freezing front passed, the tailings were dewatered further at temperatures below 0 °C. Unfrozen microscale water from within the frozen tailings was attracted to a three dimensional network of ice lenses surrounding the frozen soil peds. The laboratory experiments suggest freeze–thaw may be a technically feasible method to increase the strength and surface stability of fine tailings. [Copyright &y& Elsevier]

Continuous deposition of flocculated tailings into a deep containment facility (known as deep deposits) is gradually becoming widely acceptable as an alternative to multiple thin layered deposits, due to its reduced footprint and material handling requirements for tailings disposal. However, capping deep tailings deposits remains challenging due to the extremely slow self-weight consolidation, uncertainty in the prediction of consolidation and low surficial strength. Consequently, the resulting tailings deposits remain very soft and need to be desiccated at the surface to support capping for reclamation. This paper evaluated the effects of natural dewatering processes such as multiple freeze–thaw cycles and evaporative drying on surface crust formation for a deep oil sands tailings deposit. This paper also explored how changes in temperature gradient, initial solids content and initial water chemistry or a change in treatment process can influence the freeze–thaw dewatering process. The results suggested that the tailings samples subjected to a lower temperature gradient resulted in overall higher gravimetric solids contents and subsequent higher shear strengths at the surface after five freeze–thaw cycles. When coupled with evaporative drying, the combined freeze–thaw–drying processes further contributed to surface crust formation (strength at the surface >100 kPa). The electrical conductivity measured at each cycle and after the drying–wetting phase predicted that the upward migration of the solute contributed to the overall volume reduction during the freeze–thaw process due to osmotic and osmotically induced consolidation. • Temperature gradient primarily influences the suction towards the freezing front. • An overall lower freezing temperature gradient results in higher dewatering. • Evaporation significantly increases the strength than freeze-thaw cycles alone. • Tailings surface with very high solids content (>80%) are less impacted by rainfall. [ABSTRACT FROM AUTHOR]

Abstract: The extraction and upgrading process for bitumen from oil sand deposits in Alberta, Canada currently requires large volumes of process water. This water demand is fulfilled by importing water and recycling/reuse of clarified process water. Reuse of the clarified water results in the steady increase of organic and inorganic (salt) contaminant concentrations in the recycle water. Using a specially designed flume housed in a cold room, trickle freeze separation was evaluated for contaminant separation of saline solutions used as a surrogate for mine waste water. Experiments were conducted at various ambient temperatures, salt concentrations and mass flow rates. Melting proved to be more effective at concentrating salts than freezing. The trickle freeze/thaw process developed during the experiment was very effective at separating and concentrating the salts into a smaller volume. For source waters frozen at an ambient temperature of −15 °C and with 3000 mg/L (NaCl) or less, 80% removal of salts was possible after melting 9% of the produced ice. For source waters with higher concentrations (20,000 mg/L), 80% removal was possible after melting 27% of the produced ice. [Copyright &y& Elsevier]

Tailings dams remain on site following mine closures and must be designed and reclaimed to meet long-term goals, which may include walk-away closure or long-term care and maintenance. The underperformance of these structures can result in significant risks to public and environmental safety, as well as impacts on the future land use and economic activities near the structure. In Alberta, Canada, the expectation is for a tailings dam to be reclaimed and closed so that it can undergo deregistration. To aid in assessing the risks of underperformance during and after closure, a Generalized Failure Modes and Effects Analysis (G-FMEA) framework was developed to assess the long-term geotechnical risks for tailings dams in Alberta, with the goal of assessing the potential success of a tailings dam closure strategy. The G-FMEA is part of an initiative to enhance closure evaluations in Alberta in a collaborative effort between industry, the regulator, and academia. The G-FMEA incorporates the element of time to account for the evolution of the system, which should be applied at the planning stage and updated continually throughout the life of the facility. This paper presents the developed G-FMEA framework for tailings dams in Alberta, including the developed risk matrix framework. [ABSTRACT FROM AUTHOR]

We report a method for the phase reconstruction of an ultrashort laser pulse based on the deep learning of the nonlinear spectral changes induce by self-phase modulation. The neural networks were trained on simulated pulses with random initial phases and spectra, with pulse durations between 8.5 and 65 fs. The reconstruction is valid with moderate spectral resolution, and is robust to noise. The method was validated on experimental data produced from an ultrafast laser system, where near real-time phase reconstructions were performed. This method can be used in systems with known linear and nonlinear responses, even when the fluence is not known, making this method ideal for difficult to measure beams such as the high energy, large aperture beams produced in petawatt systems. [ABSTRACT FROM AUTHOR]

Weathering cell test, designed specifically to overcome material-limited constraints, yields prompt and efficient experimental assessment during the development stages of mining projects. However, it has barely benefited from geochemical modeling tools despite their ease of use. Accordingly, this paper aims to strengthen the upstream geochemical assessment via parametric analysis that simulates the effect of various mineral assemblages on leachate quality recovered from weathering cells. The main objective is to simulate the pH in presence of silicate neutralizing minerals and Mn release from carbonates based upon minimal characterization data. The public domain code PHREEQC was used for geochemical kinetic modeling of four weathering cells. The kinetic model utilized a water film concept to simulate diffusion of chemical elements from mineral surfaces to the pore water. The obtained results suggest that the presence of the silicate neutralizing minerals slightly affects the Mn release from carbonates. Furthermore, plagioclases could supply a significant neutralization potential when they predominate the mineral assemblage. Finally, coupling weathering cell test and parametric analyses illuminate the pH evolution for various mineral proportion scenarios. [ABSTRACT FROM AUTHOR]

Three-dimensional geological modeling is an efficient tool to visualize ore body features during both exploration and operation phases of mines. Repurposing the 3D geological modeling for mine waste management allows for the visualization of hazardous metal(loid)s distribution throughout an ore body and its host rock. With this information, a mine manager could seamlessly carry out waste rocks management based upon their classification. The major prerequisite to such an approach is to procure sufficiently large datasets in order to ensure high interpolation quality and suitable resolution. Apart from metals of economic interest, non-economic and deleterious elements usually do not undergo exhaustive geochemical analyses throughout the footwall and the hanging wall of ore bodies. Based on that premise, the Éléonore mine site provided restricted grades of arsenic, the most hazardous element within the mine setting, to create a 3D spatial model of arsenic content. A stochastic process coupled with the geological logging of drill cores was created to fulfill the 3D modeling prerequisite with known margins of error. The outcome of this work consists of a multi-realization 3D spatial model of arsenic content across the ore deposit and the host rock. Each realization was assessed using available chemical analyses to underline the model's reliability. The results revealed a spacious geochemical halo of arsenic extending up to 500 m away from the gold deposit, with up to 94% of arsenic grades exceeding 50 ppm. The process developed in this work will enable mine waste classification before stripping, thereby providing the opportunity for the formulation of proactive upstream mine waste management options that could prevent future environmental liabilities. • Merging stochastic simulation and geological logging to create 3D geomodel • Simulated As grades comply with the geological characteristics of the orebody. • As halos may reach up to 500 m away from the ore body. • Geochemical halos of As contain grades, which are seldom lower than 50 ppm. • Waste rock backfill should be preferred over surface disposal. [ABSTRACT FROM AUTHOR]