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By K. Cybulski

Coal dust explosions still remain the main hazard in the coal mining sector, notwithstanding their relatively wide recognition compared to other hazards and the development of effective methods of prevention. Coal dust explosions are still the cause of numerous catastrophes, often leading to fatalities. Fortunately, they rarely occur, and it is for this reason that their hazardous impact is often underestimated. This problem in Poland is being exclusively solved by the Central Mining Institute, Experimental Mine Barbara. Here, basic research on the phenomenon of coal dust explosions and prevention methods is carried out, as well as investigations into the causes and circumstances of past accidents. After 15 years of no coal dust explosion accidents in Poland (1987?2002), a few coal dust explosions have recently occurred, with tragic consequences. These events have taken place not only in hard coal mines, where the presence of dangerous coal dust is the result of common production cycle, and safety measures against coal dust explosions are subject to specific regulations, but also in coal-fired power plants. This is of special concern because prior to 1987, such accidents had been been reported only for coal mines and not for coal-fired power plants. In recent years, two dust explosions occurred in Polish power facilities: the Dolna Odra and Turow power plants. In both cases, coal dust explosions occurred in the fuel supply system, but biomass dust was also involved. The explosions caused significant damage to the systems and buildings. This paper gives description and schematics of the regions of catastrophic coal dust explosions that have occurred in recent years in Poland, as well as the results of post-accident investigations, presenting the coal dust explosion hazard at the accident scene The results specify in detail the state of safety measures against coal dust explosions in light of the relevant regulations in force, including amount of deposited coal dust, content of incombustible matter in coal dust, free moisture content in coal dust, state of coal dust explosion safety zones, and state of explosion barriers. The conclusions from the site inspection and post-accident investigations presented enable us to determine locations of explosion initiation, probable ignition sources, range of explosion flames, and explosion barrier performance. A complete elimination of coal dust explosion hazard at the site of dust deposition is practically impossible to achieve. Similarly, a total elimination of ignition source, which may be related to the occurrence of other natural hazards, equipment malfunction or human errors, is impossible. The examples of tragic events that took place in Polish coal mines and coal-fired power plants highlight shortcomings and mistakes made in terms of assessment and prevention measures taken against the coal dust explosion hazard.

Aug 1, 2013

By M. Souley, G. Armand, M. Ghoreychi, D. Seyedi, J. -B. Kazmierczak

"An anisotropic constitutive model is proposed in this paper accounting for both structural anisotropy and induced anisotropic plasticity. It is assumed that the rock is composed of a matrix and of potential planes of weakness. The matrix is assumed to be linear, transversely isotropic and the plasticity is described by a non linear yield function where the parameters are deduced from the nonlinear Hoek-Brown envelopes in pre- and post-peak, and derived from the laboratory characterization. A non-associated flow rule is used with a distinction between compression and extensional stress paths, as well as the absence of volumetric strain beyond large plastic distortion.The planes of weakness are considered as known a priori or assumed to be oriented perpendicular to the direction of the current minor principal stress. An elastic-perfectly plastic behavior according to the Mohr-Coulomb criterion is assumed in the planes of weakness; while the elastic part is considered as linear and transversely isotropic.Finally, the proposed model was implemented in FLAC3D and used to simulate triaxial compressions to provide a verification of the implementation. The applicability of the implemented model to reproduce damage (pre-peak) and/or failure developments around a circular opening is checked. The GCS drift, one of the mine-by experiments set up at the main level of the Meuse/Haute-Marne Underground Research Laboratory, is selected for this first application."

Jan 1, 2015

By N. Golchinfar

Tunnels in deep mines are subjected to high stresses. Fracture and failure of the rock mass around an opening can occur when mining-induced stresses are high. In burst-prone grounds, mining-induced seismicity can cause additional dynamic loading which can further increase the stress around the tunnels. When the dynamic stress reaches the rock mass strength, fracturing can occur and rockburst may happen (depending on loading stiffness around the failed rock mass). Rock support installed in the tunnel must be capable of dissipating dynamic energy and holding the failed rocks. Hence, it is important to estimate the depth of failure for rock support design. This paper focuses on how to model depth of failure under dynamic loading. In the modeling, two scenarios of rock failure are considered. In the first scenario, rock failure occurs under static loading and subsequent dynamic loading further increases the depth of failure. In the second scenario, no failure occurs under static loading but in the subsequent dynamic loading, failure around the tunnel is created.

Aug 1, 2013

By V. Loya

Metallic foams (MF) are relatively new materials with a combination of attractive properties (permeability, high surface area, thermal and chemical stability, etc,), They can be produced from different materials and can be manufactured using various processes, Due to their unique properties, they find applications in different sectors of engineering, such as energy absorption, filtration, heat dissipation, etc, For many applications, the permeability is an important parameter to characterize and optimize, Most of the recent literature on the subject studied the permeability in the low velocity range. The present study was carried out to have a better understanding of permeability for greater velocity ranges, An equipment was designed and built for this purpose, Pressure drop measurements were made across the thickness of open-cell nickel foams, Pore and window sizes were measured by image analysis on SEM micrographs, The experimental results are in relatively good agreement with the Hazen-Dupuit-Darcy model (R2>98%), The permeability is affected by pore size, porosity and the normalized projected area of the connecting pores (ie. windows).

Jan 1, 2005

By Shuan-cheng Gu

Roof bed separation often occurred due to the deformation incoordination of surrounding rock following the excavation of mine roadway. Bed separation has effect on the bolts, and the estimation of the influence will directly affect the safety of support systems. In this paper, the hyperbolic function model to analyze the load transfer mechanism on the bolts was simplified as the exponential function form for easy calculation. An elastic-plastic analysis model of the bolt loading occurred by the bed separation was established. And the development low that the bed separation affected to the bolt loading was discussed. According to the parameters analysis of different separation values and locations, the influence law of the bolt loading caused by roof bed separation was summarized. Finally, the effects of bed separation were considered for the bolting design, it was able to provide a reference to the anchorage design of stratified rock.

Aug 1, 2013

By M. A. Clayton, D. Kinakin

The Mitchell Creek Landslide is a large, structurally controlled, complex bedrock instability located in northwestern British Columbia. Characterization of the landslide using aerial photograph, exploration geology, and geotechnical investigation data has been completed allowing the development of a three dimensional conceptual model of the landslide domains and slope behaviour. Three domains have been identified in the landslide, from top to bottom: the Sliding domain, a relatively intact slab slowly sliding into the valley; the Transition domain, located in the mid slope of the landslide and showing evidence of significant extension and continuing to subside and displace into the valley; and a Toppling domain, at the toe of the landslide in an area of overturned foliation. Movement is greatest in the Toppling domain, with long term estimated rates of movement up to 4 times that of the Sliding domain; the Transition domain exhibits the greatest range of displacement rates, with average long term values approximately double the slower Sliding domain. This paper documents the results of numerical modelling of the Mitchell Creek Landslide with variation in geomechanical properties, basal rupture surface configuration, structural fabric, and pore water pressure conditions. The locations of internal shear surfaces within the landslide have been estimated from surface scarps, structural fabric orientation, and borehole monitoring data. The performance of each numerical model was evaluated against observed behaviour of the landslide. The configuration and properties of the basal rupture surface were identified as critical to model behaviour, as was spacing and location of internal structures.

Jan 1, 2015

By G. P. Gu, B. Fang, R. W. Revie, M. Elboujdaini

Stress-corrosion cracking (SCC) tests were conducted in the near-neutral pH standard solution, NS4, and in an actual soil solution, using four-point bending at high a stress ratio and low frequency conditions very similar to those of operational pipelines. Pitting incubation appeared first and then pitting initiated and grew in both solutions although there were many more pits on the specimen tested in soil purged with 5% CO2 + 95% N2 than in the specimen tested in NS4 solution purged with the same gas. These observations show that samples in soil solution are more susceptible to pitting than those in NS4 solution. When the pit reached a critical size, the increased stress concentration around the pits, resulted in the transition to a crack.

Jan 1, 2005

By X. Xu, J. K. -W. Wong, J. -Y. Delenne, K. Soga

Hydraulic fracturing (HF) is a mulit-scale and multi-physics process which makes numerical modelling challenging. Conventional numerical models focus on multi-physics nature of HF but the multiscale nature is compromised by idealization of reservoir to be continuous, homogeneous and isotropic. However, natural fractures take a significant role in the success of HF for exploration of unconventional resources like Shale gas. Advancement in microseismic monitoring provides useful data for simulation in a much greater details. There is an urgent need to develop a suitable numerical tool for multi-scale threedimensional simulation to better understand the roles of discontinuities and heterogeneity in reservoir and its interaction with HF, especially to address the environmental concerns such as induced seismicity. In this paper, a simple discontinuum numerical method – Lattice Element Method (LEM) is proposed to model HF in a large scale three-dimensional model. A reservoir is modelled as a lattice network composed of 1D Hookean’s spring. Fracturing is modelled simply by removing lattices that meet a specified threshold as determined by the critical energy release rate of the rock. By introducing disorder in the model, mesh dependency in modelling fracture growth is minimized. Fluid flow is simplified as flow in pipe network and the permeability of pipe is related to fracture aperture by cubic flow law. Therefore, fracture flow and rock deformation are fully coupled. In this paper, four simulations of the same configuration except with different degrees of reservoir heterogeneity are presented. Fractures formed are diffusive and two groups of fracture are identified – connected fractures and isolated fracture without clear spatial correlation. The former forms a ‘fracture cloud’ and contributes to fluid flow and modeled by pipe network. The flow of fluid is highly tortuous and pipe network is sparely connected. The degree of reservoir heterogeneity controls the growth of ‘fracture cloud’ and pipe network. Microseismic monitoring often shows diffusive fracturing during HF on site and hence the outcome of the proposed model can be compared to such monitoring results.

Jan 1, 2015

By C. P. Moore, G. W. Taylor

Vertically dipping lenses of nickel-copper ore at Dumbarton Mines Limited are being mined by a modified blasthole stoping method. The principal access to the mine is provided by a 15-degree decline, which, in conjunction with the use of ramps and declines for secondary access, maximizes the accessibility and mobility of trackless mining equipment. Sublevels are driven in ore on 80-foot vertical intervals and subsequently the ore, ranging in thickness from 15 to 30 feet, is slashed to its limits by a procedure of face sampling and test holing. Two longhole drill jumbos are used to drill off 40-foot vertical slices above and below these levels. Following blasting, the ore falls by gravity to the 500-foot horizon, where it is removed from drawpoints by load-haul-dump units and transported by truck to the main orepass. The rock is crushed to minus 3-4 inches and conveyed to surface by a 30-inch-wide wire rope suspended conveyor. This is achieved in two flights, a lower one of 290 feet and a main flight of 2260 feet. All aspects of the mining operation are discussed in the paper, including ventilation, services and safety.

Jan 1, 1973

By D. A. Beattie

Three novel dextrin polymers of varying functional group chemistry but similar molecular weight have been used to depress talc in single and mixed mineral studies. The mixed mineral system was a model sulphide ore consisting of talc, pentlandite, and chalcopyrite. Adsorption isotherms for the three polymers on both valuable and gangue mineral phases were determined to give initial clues as to the ability of the polymers to depress talc. Flotation testing revealed a distinct hierarchy of effectiveness of the polymers in the depression of talc in the single mineral system (MP Dextrin > CM Dextrin > Dextrin TYM), reflecting the observed adsorption affinity and adsorbed amount of the polymers on talc. However, a different order of effectiveness was observed for talc depression in the mixed mineral system (CM Dextrin > MP Dextrin > Dextrin TYM). Competition between the valuable and gangue mineral phases for uptake of MP Dextrin is responsible for its observed decrease in efficiency in mixed mineral flotation. All three polymers were found to be reasonably selective in their action, although at high dosages the polymers began to affect the flotation of the valuable minerals.

Jan 1, 2006

By M. R. Julien, A. Maqsoud, J. Martschuk, B. Bussière

Acid mine drainage (AMD) from mine wastes is one of the most challenging environmental problems currently facing the mining industry. When mining wastes have the potential to produce AMD, the effluents produced have to be managed to meet existing regulations on water quality. The LTA impoundment (property of Barrick Gold Corp.) located near Malartic, Quebec, contains sulphide tailings that have the potential to generate an acidic leachate. The closure option selected by Barrick was to construct a cover with capillary barrier effects (CCBE), in which the moisture- retaining layer is made of non-acid-generating tailings. Since its construction in 1996, the cover has been monitored to evaluate its performance. For that purpose, various parameters have been measured, including the volumetric water content and matric suction in the different layers of the cover. This paper presents some of the main results from the monitoring program that started eight years ago. The results show that the cover is able to maintain a high degree of saturation in its moisture- retaining layer, acting as an oxygen barrier. The actual performance of the CCBE on the flat surface of the 60 ha site is better than expected at the design stage. The only concern with the LTA cover is the effect of slopes that can reduce the performance of the CCBE during dry periods. However, these effects appear only for short periods of time, and are limited to very localized areas, so that they do not significantly affect the overall performance of the CCBE and its ability to limit the production of AMD.

Jan 1, 2006

By G. G. Bowser

Introduction Flame shots are of very infrequent occurrence in the coal mines of Nova Scotia. Probably not more than one is recorded in three months. Many shot-firers have never experienced one, and many never will. As a consequence, although all such occurrences are very carefully investigated, information concerning the cause of flame shots is somewhat meagre. In the course of the years, however, something has been learned of the practices and conditions that are responsible for them. During the past ten? years, over seventeen million shots were fired in the coal mines of Nova Scotia and only fifty-two faulty shots were reported or investigated during that time. In thirty-nine of these, flames were reported; in five, sparks only; and in eight, smoke only. In eight of these occurrences, unburned explosive was found after firing. In one of these eight, flame was seen in the back part of the hole, and an accompanying hissing sound pointed to burning explosive. In four of them, there was no evidence that gas was not ignited. All samples of explosives from these faulty shots which were submitted for analysis were found to be normal, except two, in 1937, which contained excessive moisture. These two samples were from two following shots in the same room on the same day. The initial cause of trouble with all eight shots was one or several of the following: explosives in poor condition, separation of cartridges, incorrect priming, shot hole in poor condition or not properly cleaned. In the case of sixteen or seventeen of the thirty-nine shots which flamed, data are insufficient for conclusions to be drawn as to the cause of the flame.

Jan 1, 1947

By S. Malopheyev, I. Vysotskiy, R. Kaibyshev, S. Mironov

"In this work, the effect of pre-strain rolling on the annealing behavior of friction-stir welded 6061-T6 aluminum alloy was studied. To this end, the as-welded material was rolled to 10 or 20 pct. of thickness reduction prior to the standard post-weld T6 heat treatment. Three rolling directions were the 3-mm thick sheet were considered: along the welding direction, perpendicular to the welding direction, and at the angle of 45° to the welding direction. At relatively low pre-strains (10 pct.), the annealing behavior was found to be very sensitive to the rolling path, and rolling along the welding direction was most effective in suppressing abnormal grain growth. On the other hand, increasing the pre-strains to 20 pct. of thickness reduction inhibited abnormal grain growth irrespective of the rolling path.INTRODUCTION Heat-treatable wrought Al-Mg-Si alloys are widely used due to attractive combination of strength, ductility, excellent corrosion resistance and low cost (Polmear, 2006). To provide the optimal balance of mechanical properties, these materials are typically commercially available in appropriately work- and precipitation-hardened conditions (Polmear, 2006). During conventional fusion welding, however, the prior strengthening effect is totally lost due to elimination of the work hardened structure and dissolution of the strengthening precipitations. An innovative friction-stir welding (FSW) technology may partially overcome this problem. Due to the solid-state character of this process, which involves very large strains, the welded material is characterized by fine-grained microstructure with moderate-to-high dislocation density, and thus the prior work hardening effect may be preserved or even enhanced (Threadgill et al., 2009; Mishra & Ma, 2005). However, heat input associated with FSW inevitably leads to dissolution and/or coarsening of strengthening precipitates, thus giving rise to the undesirable material softening. In an attempt to restore the strength of the friction-stir welded material, the standard T6 post-weld heat treatment has been applied, but this approach was found to lead to abnormal grain growth (Malopheyev et al., 2016; Mironov, 2013, Mironov et al., 2015)."

Jan 1, 2018

By T. J. Langan, M. Ramajayam, T. Dorin

"6xxx-series Al alloys are the most commonly used alloys in the automotive industry as they have an appropriate balance of strength, corrosion resistance and formability. The main strengthening phase in these alloys is the ß’-Mg2Si precipitates. One opportunity to achieve stronger 6xxx-series Al alloys, without affecting corrosion and formability, is the use of Sc. The main challenge of using Sc in 6xxx-series lies in the heat treatment, which must be designed to allow for a fine precipitation of both Al3Sc and ß’-Mg2Si. In this work, two model alloys are used, an Al-Sc-Zr and an Al-Mg-Si-Cu-Sc-Zr, to explore the impact of the 6xxx-series key elements (Mg, Si and Cu) on the Al3Sc precipitates. Transmission electron microscopy and atom probe tomography are used to investigate the precipitates present in the microstructure after casting. We find that higher Si content results in the formation of dispersoids upon casting. The average composition of these dispersoids is (Al0.8,Si0.2)3 (Sc0.888,Zr0.024,Mg0.08,Cu0.008). A closer look at the solid solution reveals that most of the Sc and Zr is supersaturated after casting even in the presence of Mg, Si and Cu. We discuss the impact of these results on the design of a suitable heat treatment for 6xxx-series alloys with Sc.INTRODUCTION The most common strategy to strengthen aluminum (Al) alloys is by micro-alloying to form a fine distribution of precipitates (Gladman, 1999). Whilst precipitates enhance the strength, this is often done to the detriment of ductility and corrosion performance (Davis, 1999). The 6xxx-series Al alloys are heavily used in the automotive industry as they offer an appropriate balance of strength, ductility and corrosion resistance (W. S. Miller et al., 2000). The strength increment in these alloys comes from the formation of the ß’–Mg2Si and the quaternary Q’ phase (Chakrabarti & Laughlin, 2004; Polmear, St. John, Nie, & Qian, 2017). One opportunity to achieve stronger 6xxx-series alloys, whilst keeping good balance of corrosion resistance and formability, is the use of small additions of scandium (Sc). Sc is one of the most potent strengtheners in Al alloys (Dorin, Ramajayam, Vahid, & Langan, 2018; Røyset & Ryum, 2005). Most of the strengthening benefits from Sc come from the formation of fine Al3Sc dispersoids. The following strengthening mechanisms apply to Sc: 1) Solid solution strengthening, 2) precipitation hardening, 3) inhibiting recrystallization, 4) assisting nucleation of other strengthening phases (Dorin, Ramajayam, Lamb, & Langan, 2017). As compared to other dispersoid phases, Al3Sc dispersoids have good electrochemical compatibility with Al alloys and hence do not affect their corrosion resistance (Cavanaugh, Birbilis, Buchheit, & Bovard, 2007). The coarsening resistance of Al3Sc is often improved by adding zirconium (Zr), as it forms a Zr rich shell around Al3Sc which prevents Sc from moving across the interface."

Jan 1, 2018

By John Hansen

This paper has been written for presentation at the 103rd Annual General Meeting of the Canadian Institute of Mining, Metallurgy, and Petroleum, April 29 to May 02, 2000. The paper addresses blast pattern fragmentation and diggability versus the blasting technique used. RESUME The author is the Vice President for Thunderbird Mining Systems. In this capacity he manages the mine site installation of surface mining mobile equipment monitoring and navigation systems. These systems are onboard instrumentation and software systems designed to: ??measure and log mobile equipments? production and health; and ??direct the equipment operators via onboard displays that show comprehensive maps and engineering instructions. The author is a mining engineering graduate from the Royal School of Mines. His work experience includes front line supervisor and mining engineer for Hudson Bay Mining & Smelting, mining engineer for Teck Corporation, and mining consultant for PriceWaterhouseCoopers.

May 1, 2001

By Martin P. Raffield

Placer Domes? Campbell Mine, situated in northwestern Ontario, is undergoing an assessment of the efficiency of the operation which is necessitated by the low gold price and a reducing ore reserve grade. A decision has recently been taken to move away from a functional based departmental structure (underground, engineering, geology, etc.) towards a team-based system where crews, engineers, geologists and supervisors are responsible for the planning and operation of a particular area of the mine. The objective is to improve communication and understanding of the goals and achievements and to ensure a forum is available for the generation of ideas. It is intended to increase the accountability and decision-making ability of the teams in an effort to achieve the mines? safety and production targets. This paper presents a critical review of the progress of this organisational change process and its successes and failures at the time of writing.

Oct 1, 2001

By Turgut Yalcin

"In this study, potential benefits of focculant usage were explored in the processing of mill tailings by hydrocyclones. Tests conducted on copper-nickel mill tailings have demonstrated that, under suitable conditions, flocculation could significantly enhance solid-liquid separation in hydrocyclones. For example, at a feed pulp density of approximately 9%, focculant-assisted hydrocyclone produced an underflow with over 98% solids recovery, compared to a recovery of less than 53% with conventional hydrocyclone. However, feed pulp density was found to be a critical factor, and tailings with pulp densities of greater than about 15%required a two-stage hydrocyclone operation where the focculant-assisted hydrocyclone was employed at the second stage to process the overfow of a conventional hydrocyclone.The underflow and overflow products obtained from the focculant-assisted hydrocy-clone may be discharged into tailings dams in the same manner as those produced by gravity thickeners. The focculant-assisted hydrocy-clone would, however, provide a higher throughput."

Jan 1, 1996

By M. D. Evans

"Note: The views expressed herein are those of the author, not of the Government of CanadaThe mining industry has a significant opportunity to capitalize on past learnings to build better social relationships. The industry’s relationship with society is critical and under pressure. Rising levels of public opposition and social conflict are already having material impacts on operations around the world. The industry has an opportunity to shape the future direction of this social engagement, build public trust, and proactively respond to a material risk to operations, but first it needs to better understand the nature of the challenges and the urgency of addressing them.RÉSUMÉ L’industrie minière a actuellement une excellente occasion de tirer profit de ses expériences antérieures pour établir de meilleures relations sociales. Les relations entre l’industrie et la société sont critiques et elles subissent de grandes pressions. L’escalade de l’opposition par le public et les conflits sociaux ont déjà des impacts physiques sur les opérations partout à travers le monde. L’industrie a l’occasion de façonner la future direction de son engagement social, d’accroître la confiance du public et de répondre de manière proactive à un risque matériel aux exploitations, mais elle doit tout d’abord mieux comprendre la nature des défis et l’urgence de les traiter."

Jan 1, 2015

By F. Bosché

Previous research has shown that ?Scan-vs-BIM? systems are powerful to provide valuable information for tracking structural works (progress, quality, safety). However, the transferability of this capability to other construction areas such as MEP works has not been assessed so far. Comparatively, the construction of MEP systems, in particular pipes and ducts, tends to be more flexible with respect to the positioning of individual components, so that Scan-vs-BIM systems could be defeated when tracking MEP installation works. This paper presents recent results on the feasibility and performance of using a Scan-vs- BIM system to track MEP works. The approach followed is presented and then tested with two real-life challenging case studies were conducted simultaneously but totally independently in Canada and Italy. The results show that, as expected, pipes and ducts tend to be more loosely positioned than structural elements leading to a poorer performance of the Scan-vs-BIM system. Nonetheless, it appears that the system works well to assess the level of conformance of site installation works, providing valuable information for estimating emerging performance metrics like ?percent built as-designed?. In addition, the proposed system could also be useful to accelerate and thus reduce the cost of delivering as-built BIM models for in the case of new builds.

Aug 1, 2013

By H. Golzarpoor

Life Cycle Analysis (LCA) is a methodology for evaluating the environmental impacts associated with a product during its life cycle. LCA is identified as the most reliable method for verifying environmental impacts; however, current LCA-based approaches have certain limitations for environmental analysis of construction products. Integration of the LCA methodology with Discrete Event Simulation (DES) provides a sound framework for modeling and analysing the environmental impacts of construction products. LCA and DES is one possible combination for analysing the cause and effect of various scenarios where time, resources, and randomness of input variables affect the outcome and, therefore, has the potential to address the shortcomings of LCA in construction. Recent studies in disciplines other than construction such as manufacturing systems have revealed positive effects on evaluation of environmental metrics while integrating LCA with DES; however, this integration has not yet been applied for environmental analysis of construction products. By implementing LCA data in a DES model, this research proposes an environmental model of earthmoving operations in a case study. Environmental variables are simultaneously assessed with production variables in the same simulation model and the integration of DES and LCA is discussed.

Aug 1, 2013