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Landslides are frequent occurrences in Ottawa, Canada because sensitive marine clays (also known as Leda clay or Champlain Sea clay) dominate the landscape. These landslides are often triggered by ...

Cemented paste backfill (CPB) has been extensively used in the mine industry to backfill underground mine cavities for ground support and/or tailings management. Once placed in mine underground cav...

Ground Granulated Blast Furnace Slag (GGBS) has been increasingly used as replacement of Portland cement (PC) at different proportions in cemented paste backfill (CPB) material due to its relative ...

The reactivity of sulphidic cemented paste tailings (CPT) is an indicator which can be used to assess their environmental performance and durability. However, the reactivity is influenced by severa...

This paper provides a comprehensive understanding and unique aspects of modelling cemented paste backfill (CPB) behaviour and performance under complex multiphysics conditions. Such modelli...

This paper presents the results of an investigation that aimed to evaluate the influence of sodium chloride (NaCl or salt) on the yield stress and evolution of the strength of a cemented tailings material (called cemented paste backfill, CPB) that contains ground granulated blast furnace slag (Slag-CPB) in sub-zero environments. About 200 CPB specimens with different NaCl concentrations (0, 5, 35, and 100 g/L) and cured at −6 °C are tested at different curing times (0, 0.25, 1, 2, and 4 h for yield stress measurement; 7, 28, and 90 days for uniaxial compressive testing). Moreover, microstructural analyses are conducted on cement-slag paste and Slag-CPB samples with various concentrations of NaCl. The results show that the addition of NaCl provides better flowability of the fresh Slag-CPB and significantly affects the strength development of Slag-CPB. The results presented in this study have significant implications for backfill practices in permafrost and cold regions.

This study offers new insights into two-lift deposition of mature fine tailings under atmospheric drying. The interaction of newly added lift and former lift(s) was evaluated using column experiments in terms of volumetric water content, electrical conductivity (EC), hydraulic conductivity, geochemistry and microstructure. Water content and EC followed the same trend and decreasing of water content appears to be responsible for significant reduction in EC. Evaporation on top of the column reduced the water content to almost zero. The obtained results support the coupling between the hydraulic and chemical processes that should be considered by active operators.

A pressure cell apparatus has been developed in this research work to study the long-term hydro-mechanical behaviour of cemented paste backfill (CPB) cured under applied stress. The samples are cured for 7, 28, 90 and 150 days and the evolution of their mechanical, hydraulic, physical and microstructural properties is studied. Also, the suction, temperature and electrical conductivity are monitored for a period of 150 days of curing. The testing and monitoring programmes are conducted in undrained conditions, with and without pressure application. The obtained results show that the curing stress affects the hydro-mechanical behaviour of CPB for up to 28 days. Within this curing period, the CPB exhibits enhanced hydro-mechanical performance. However, application of sustained excessive curing stress onto the CPB samples induces the propagation of microcracks in the backfill structure, thus causing lower mechanical strength and higher fluid permeability at the more advanced ages. Furthermore, the min...

A coupled thermo-hydro-chemical (THC) model has been developed to study the thermally and hydraulically coupled processes in hydrating cemented paste backfill (CPB). Afterwards, the THC model is validated against laboratory data (CPB made of Portland cement and CPB that contains mineral admixtures) and field CPB column studies (CPB cured in underground mine environments). In addition, the validated THC model is applied to simulate and predict the thermal (e.g. temperature development and thermal conductivity), hydraulic (e.g. water drainage, suction or negative pore-water pressure development and hydraulic conductivity) and physical (porosity) evolutions of the CPB columns under different conditions, such as various CPB temperatures and water-to-binder ratios. The presented outcomes can contribute to a better understanding of the coupled thermal-hydraulic processes that occur in CPB and the thermal and hydraulic behaviours of CPB structures, as well as a better design of stable, durable and cost-effective...

The aim of this study was to investigate the potential mutagenic activity of diesel engine exhaust in the Ames/Salmonella assay using a direct aerosol exposure system. So, TA 98 and TA 100 strains, with or without added S9 mix, were exposed to diesel emissions after varying degrees of filtration. Variants of these two strains, deficient in nitroreductase (TA 98NR and TA 100NR) or over-expressing O-Acetyl Transferase (YG 1024 and YG 1029), were also exposed to total (unfiltered) diesel exhaust to highlight the putative mutagenicity of any nitro-PAHs present in these emissions. Mutagenic activity of the diesel exhaust was demonstrated on Salmonella typhimurium, strains TA 100 and variants TA 100 NR and YG1029. The use of a particle filter did not modify the genotoxicity of the diesel emissions, indicating a major contribution of the gas phase to the mutagenicity of these diesel emissions. The prominent role of the particulate-associated nitro-polycyclic aromatic hydrocarbons (nitro-PAHs) claimed by some aut...

Cemented paste backfill (CPB) is extensively used in underground mine operations. Several studies have been conducted to investigate the mechanical properties of CPB. However, little attention has been devoted to the thermal conductivity of CPB. The knowledge of this thermal property is vital for the design of cost-effective and durable CPB materials. This article presents the results of a comprehensive laboratory study on the thermal conductivity of CPB. Influencing factors on the thermal conductivity of CPB were quantitatively investigated. The measurements of thermal conductivity were performed by using the KD2 Thermal Properties Analyser. Valuable results with regards to the effects of CPBs mix components, curing time and temperature, and water saturation degree on the thermal conductivity of CPB were gained. It is felt that the present study would contribute to the better optimisation of CPB mixtures and the design of more cost-effective and durable CPB underground structures.

Among the various technological proposals under consideration to limit diesel exhaust particles (DEP) emissions, the use of a particulate filter in conjunction with a fuel-borne catalyst is currently the primary focus and likely to be introduced over the coming years. One specific catalyst is a cerium-based compound Envirox™ developed by Oxonica (Kidlington, UK) and used as a fuel additive to reduce particulate matter (PM) emissions from diesel engines. Prior to any commercialization it is necessary to undertake an assessment of any potential adverse health effects resulting from exposure to cerium oxide particles especially via the inhalation route, i.e., on the lung. Since the composition of engine exhaust emissions from additized fuel might be different to those emissions from un-additized diesel fuel, the second phase of the current investigation compared the potential biological impact of engine emissions from cerium oxide additized fuel to that of a reference fuel. An experimental procedure develope...