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To investigate the effect of the pore matrix (i.e., ice and unfrozen water) on the strength of partially frozen sand, a series of triaxial compression tests with internal pore water pressure (PWP) measurements were performed. Both dense and loose saline sand samples were prepared by rapidly freezing the samples and then slowly warming the samples to, and subsequently shearing at the temperature of -3 [degrees]C. Test results indicate the temperature only affects the effective cohesion, not the effective friction angle of sand. The pore ice stress was estimated using Ladanyi and Morel's 1990 postulate on the internal stresses within frozen soil; the stress (hydrostatic) change in pore ice was reflected by an equal change in PWP in the partially frozen loose sand. Based on Ladanyi and Morel's 1990 concept of internal confinement in frozen sand, a Mohr-Coulomb model that uses effective failure and residual friction angles from unfrozen sand to estimate the strength of partially frozen sand is presented. The proposed model reflects how the pore matrix contributes to the strength of partially frozen sand. For loose sand, the peak strength is enhanced by the internal confinement and cohesion resulting from the pore water (suction) and pore ice, respectively. For dense sand, only pore ice affects the peak strength by incorporating the internal confinement and cohesion. Key words: pore matrix (ice and unfrozen water), partially frozen soil, shear strength, effective stress, pore ice stress, Introduction Climate change is a major challenge facing coastal and northern communities in Canada's North. A growing body of reports provides evidence that well-functioning infrastructure in permafrost regions is starting [...]

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]

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.

Considerable research has been conducted over the past decade by oil sands mining companies to improve the dewatering and strength properties of fluid fine tailings deposits in an effort to meet the regulatory and closure requirements. Commercially employed dewatering treatment technologies (inline flocculation, thickening, and centrifugation) may not be sufficient to develop the strength for the creation of trafficable landscape without the use of soft soil capping technologies. These treated tailings are continuously deposited creating soft and saturated deep deposits. Seasonal weathering may be an additional promising technology to further dewater the treated tailings and promote the development of shear strength at the surface. This paper presents the effects of seasonal weathering on dewatering and strength that were investigated by performing multiple cycles of freeze-thaw and alternate drying-wetting cycles on two types of treated tailings deposit. The results indicate that multiple cycles of seasonal weathering significantly increased the dewatering and strength properties. However, different parameters such as freezing gradient, number of seasonal cycles, and pore water chemistry play an influential role in changing the magnitude of the strength. The results also suggest that a minimum threshold strength value is required where the effects of rainfall rewetting had a minimal impact on strength reduction (the strength corresponding to the moisture content approaching the plastic limit). Key words: seasonal weathering, freeze-thaw, oil sand tailings, shear strength, evaporation, dewatering. Les entreprises d'exploitation des sables bitumineux ont mene des recherches considerables au cours de la derniere decennie pour ameliorer les proprietes de deshydratation et de resistance des depots de residus fins fluides dans le but de repondre aux exigences reglementaires et de fermeture. Les technologies de traitement de deshydratation employees commercialement (floculation en ligne, epaississement et centrifugation) peuvent ne pas etre suffisantes pour developper la resistance necessaire a la creation d'un paysage praticable sans l'utilisation de technologies de recouvrement par des sols mous. Ces residus traites sont continuellement deposes, creant des depots profonds mous et satures. La meteorisation saisonniere peut etre une autre technologie prometteuse pour deshydrater davantage les residus traites et favoriser le developpement d'une resistance au cisaillement a la surface. Cet article presente les effets de l'alteration saisonniere sur la deshydratation et la resistance qui ont ete etudies en effectuant des cycles multiples de gel-degel et des cycles alternes de sechage-mouillage sur deux types de depots de residus traites. Les resultats indiquent que les cycles multiples d'alteration saisonniere ont augmente de maniere significative les proprietes de deshydratation et de resistance. Cependant, differents parametres tels que le gradient de congelation, le nombre de cycles saisonniers et la chimie de l'eau interstitielle jouent un role influent dans la modification de l'ampleur de la resistance. Les resultats suggerent egalement qu'une valeur seuil minimale de resistance est necessaire, ou les effets de la rehumidification par les pluies ont un impact minimal sur la reduction de la resistance (la resistance correspondant a la teneur en humidite approchant la limite plastique). [Traduit par la Redaction] Mots-cles: alteration saisonniere, gel-degel, residus de sable petrolifere, resistance au cisaillement, evaporation, deshydratation., Introduction The Athabasca oil sand deposits in northern Alberta, Canada, are considered to be the fourth largest proven reserve in the world that contain approximately 177 billion barrels of economically [...]

Oil sands fluid fine tailings deposits are challenging to reclaim due to their inherently high natural water content, low permeability, and low strength. Combinations of polymers and (or) coagulants are used by operators to improve the dewatering and strength properties of the tailings. However, considerably more work has been done to evaluate polymer performance with short-term dewatering metrics rather than with long-term metrics such as consolidation properties. This paper evaluates the potential of four novel polymers for use in fluid fine tailings treatment compared to a commercially available polymer and untreated tailings specimen. The performance of the polymers was assessed through initial screening with respect to short-term dewatering, evaluation of the consolidation and strength properties using large-strain consolidation tests, shear sensitivity in pipeline transport, and finally, large-strain consolidation modelling to appraise the relative potential performance under different strategies, such as terrestrial or aquatic reclamation options. One polymer exhibits remarkably fast dewatering at high void ratios, while another demonstrates dense and shear-resistant flocs. The paper discusses each polymer's distinctive tailings fabrics and how their unique merits and limitations would benefit different reclamation eventualities. Finally, potential improvements of the polymers are suggested for future assessment. Key words: oil sands, tailings, polymers, consolidation, strength, modelling. Il est difficile de recuperer les depots de residus fins fluides de sables bitumineux en raison de leur teneur naturelle en eau elevee, de leur faible permeabilite et de leur faible resistance. Pour ameliorer les proprietes de deshydratation et de resistance des residus, les exploitants utilisent des combinaisons de polymeres et/ou de coagulants. Les performances des polymeres ont toutefois ete evaluees davantage en fonction de parametres de deshydratation a court terme qu'en fonction de parametres a long terme tels que les proprietes de consolidation. Le present document evalue le potentiel de quatre nouveaux polymeres pour une utilisation dans le traitement des residus fins fluides par rapport a un polymere offert sure le marche et a un echantillon de residus non traites. Les performances des polymeres ont ete evaluees par le biais d'une selection initiale concernant la deshydratation a court terme, revaluation des proprietes de consolidation et de resistance a l'aide d'essais de consolidation a grande deformation, la sensibilite au cisaillement dans le transport par pipeline et, enfin, la modelisation de la consolidation a grande deformation pour evaluer les performances potentielles relatives dans le cadre de differentes strategies, telles que les options de remise en etat terrestre ou aquatique. Les resultats montrent qu'un polymere presente une deshydratation remarquablement rapide a des taux de vide eleves, tandis qu'un autre presente des flocs denses et resistants au cisaillement. L'article aborde les materiaux de residus distinctifs de chaque polymere et la maniere dont leurs merites et limites uniques pourraient profiter a differentes eventualites de remise en etat. Enfin, des ameliorations potentielles des polymeres sont suggerees pour une evaluation future. [Traduit par la Redaction] Mots-cles: sables bitumineux, residus, polymeres, consolidation, resistance, modelisation., Introduction Surface mining of oil sands bitumen deposits produce tailings, which comprise water, sands, clays, residual hydrocarbons, and chemicals originating from the bitumen extraction process (Royal Society of Canada Expert [...]

The unsaturated properties of a soil are required to predict the rate of dewatering and magnitude of strength gain of a mine waste tailings deposit during desiccation dewatering. This prediction requires the soil-water characteristic curve (SWCC), which is time-consuming and challenging to attain and may take anywhere from weeks to months to complete a single test. As a result, alternative methods are needed to estimate the SWCC. Past research has indicated that the soil-freezing characteristic curve (SFCC) can be used to estimate the SWCC in some soils. An experimental method and apparatus were developed to measure the SFCC to estimate the SWCC for different mine waste tailings, including copper tailings, gold tailings, and oil sands centrifuge cake. The experimental method involved using a resistance temperature detector to measure the temperature and time domain reflectometry to determine the unfrozen water content of the soil. The results showed that the SFCC could be used to estimate the SWCC for tailings from metal mines (gold tailings and copper tailings) with a high portion of sand-sized particles and a small amount of clay-sized particles, but was not able to estimate the SWCC for oil sands tailings. Key words: soil-freezing characteristic curve (SFCC), soil-water characteristic curve (SWCC), time domain reflectometry (TDR), tailings, unsaturated, dewatering. Les proprietes d'un sol non sature sont necessaires pour predire le taux de deshydratation et l'ampleur de gain de resistance d'un depot de residus de dechets miniers au cours de la deshydratation par dessiccation. Cette prevision necessite la courbe caracteristique de l'eau du sol (<< soil-water characteristic curve, SWCC >>), ce qui est long et difficile a atteindre et peut durer de quelques semaines a quelques mois pour completer un essai unique. En consequence, d'autres methodes sont necessaires pour estimer la SWCC. Des recherches anterieures ont indique que la courbe caracteristique de gel du sol (<>) peut etre utilisee pour estimer la SWCC dans certains sols. Une methode experimentale et l'appareil ont ete mis au point pour mesurer la SFCC pour estimer la SWCC pour differents residus de dechets miniers, y compris les residus de cuivre, d'or, et de gateau de centrifugation des sables petroliferes. La methode experimentale consistait a utiliser un detecteur de temperature a resistance pour mesurer la temperature et a utiliser la reflectometrie a dimension temporelle afin de determiner la teneur en eau non gelee du sol. Les resultats ont montre que la SFCC peut etre utilisee pour estimer la SWCC pour les residus provenant des mines de metaux (or et cuivre) avec une forte proportion de particules de sable et une petite quantite de particules de la taille de l'argile, mais n'a pas ete en mesure d'estimer la SWCC pour les residus de sables bitumineux. [Traduit par la Redaction] Mots-cles: courbe caracteristique de gel du sol (SFCC), courbe caracteristique de l'eau du sol (SWCC), reflectometrie a dimension temporelle (RDT), residus, insatures, deshydrates., Introduction Mineral processing results in the generation of large volumes of tailings that consist of different combinations of sand, fines, and water (Bussiere 2007). These tailings are often subject to [...]

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]

Regulatory policy and regulations in Alberta require oil sands companies to reduce their production and storage of fluid fine tailings by creating deposits that can be reclaimed in a timely manner. To meet the regulatory requirements, some companies are adding flocculants to the fluid fine tailings and then using thickeners, inline flocculation or centrifuges to increase the solids content. Freeze-thaw and drying processes are then used to further dewater the tailings. The effects of flocculating, thickening, and freeze-thaw treatments were investigated by performing large-strain consolidation and shear strength tests on these treated fluid fine tailings. The consolidation and shear strength results were then compared with those of untreated fluid fine tailings. All of the treatments increased the hydraulic conductivity of the fluid fine tailings to some degree, but had little to no effect on the compressibility and shear strength. The effects of the treatment processes are discussed and evaluated. Key words: tailings, consolidation, thickening. La reglementation et les reglements en vigueur en Alberta exigent que les entreprises de sables bitumineux reduisent leur production et leur entreposage de residus fins liquides en creant des gisements qui peuvent etre recuperes en temps opportun. Pour repondre aux exigences reglementaires, certaines entreprises ajoutent des floculants aux residus fins fluides, puis utilisent des epaississants, de la floculation en ligne ou des centrifugeuses pour augmenter la teneur en solides. Des procedes de congelation-decongelation et sechage sont ensuite utilises pour deshydrater davantage les residus. Les effets des traitements de floculation, d'epaississement et de congelation-decongelation ont ete etudies en effectuant de grands essais de consolidation de la deformation et de resistance au cisaillement sur ces residus fins fluides traites. Les resultats de la consolidation et de la resistance au cisaillement ont ensuite ete compares a ceux des residus fins fluides non traites. Tous les traitements ont augmente la conductivite hydraulique des residus fins fluides dans une certaine mesure, mais ont eu peu ou pas d'effet sur la compressibilite et la resistance au cisaillement. Les effets des processus de traitement sont discutes et evalues. [Traduit par la Redaction] Mots-cles: residus, consolidation, epaississant., Introduction Oil sands tailings have been produced for 50 years and now cover an area of 220 km2 (AESRD 2014). The volume of fluid fine tailings (FFT) stored in tailings [...]

The oil sands in northern Alberta have been mined to produce bitumen over the past five decades. Since the 1980s, technical advances have been made in mining, material handling, and bitumen extraction. However, acquiring practical methods to control and reduce the fluid fine tailings build-up has been an ongoing challenge. Recent regulatory changes have driven the industry to review current tailings-management techniques and investigate numerous alternative technologies and processes to manage and reclaim fine tailings. Many of these fine tailings-management techniques involve some form of polymer or chemical addition to promote dewatering and strength gain to meet the regulatory requirements. Based on the reported data, the chemically amended fine tailings deposits have the characteristics of sensitive, metastable deposits, necessitating additional mitigative measures by oil sands operators beyond the regulatory requirements. This paper explores the geotechnical aspects of meeting regulatory strength performance criteria by employing flocculation-based dewatering of fluid fine tailings. Key words: mature fine tailings, oil sand tailings, flocculation, dewatering, sensitive clay, polymer. Les sables bitumineux du nord de l'Alberta sont mines pour produire du bitume depuis cinq decennies. Depuis les annees 1980, des avancees techniques ont ete realisees dans les domaines du minage, de la manutention et de l'extraction du bitume. Cependant, l'acquisition de methodes pratiques pour controler et reduire l'accumulation de residus fins fluides demeure un defi. Des changements recents dans la reglementation forcent l'industrie a revoir leurs pratiques actuelles de gestion des residus et a etudier des technologies et procedes alternatifs pour gerer et restaurer les residus fins. Plusieurs de ces techniques de gestion des residus fins impliquent l'addition d'un polymere ou d'un produit chimique pour ameliorer le retrait de l'eau et l'acquisition de resistance afin de repondre a la reglementation. Selon les donnees presentees, les depots de residus fins amendes avec des produits chimiques ont les caracteristiques de depots metastables sensibles, qui necessitent des mesures d'attenuation additionnelles par les operateurs des sables bitumineux, au-dela des normes reglementaires. Cet article explore les aspects geotechniques impliques dans les procedes de retrait d'eau des residus fins fluides bases [S.sub.uR] la floculation servant a atteindre les criteres de performance en resistance demandes par la reglementation. [Traduit par la Redaction] Mots-cles: residus fins matures, residus de sables bitumineux, floculation, retrait de l'eau, argile sensible, polymere., Introduction Mining and extraction of oil sands to produce bitumen has been underway in northeastern Alberta for over five decades. The Canadian oil sands deposit contains an estimated 170 billion [...]