Search Documents

By P. Tukkaraja, K. Katzenstein

"Block caving is one of the most economical and efficient underground mining methods and has gained popularity around the world especially for extracting low grade and massive ore bodies. However, during the extraction of ore from the draw bells, gases trapped inside the cave could emit into the working areas; hence, ventilation plays a key role in operating block cave mines successfully where gas emission is a concern. To design an effective ventilation system for a block caving mine, given the dynamic nature of the caving process, it is necessary to develop airflow characteristic curves (P-Q) for a given cave. This study uses a 1:100 scale physical model with an exhaust fan system, and a Computational Fluid Dynamics model of a block cave to investigate the airflow behavior through the cave filled with broken rock material. From this study, it was observed that the cave airflow resistance increases with the decrease in cave porosity and the particle size.INTRODUCTIONThe block cave mining method is gaining popularity owing to its low cost and high productivity. This study considered a case where this bulk mining method is used for the extraction of an orebody that contains uranium mineralization. During the extraction of broken ore from the draw bells, radioactive gases trapped in the cave zone could be released into the production drifts and could create unsafe working conditions in the mine. Mine ventilation systems play an important role in regulating the migration of radon in working areas. One of the strategies to control radon migration in a block cave mine is to exert negative pressure on the cave zone by using an exhaust fan above the cave zone. In order to select an appropriate exhaust fan system, it is necessary to study the airflow resistance of the cave zone (Loring & Nelson, 2006).Extraction of broken ore via drawpoints creates a void volume inside the cave called the air gap. Air gaps with larger heights can lead to air blasts in a block cave mine should the cave collapse. Besides that, the air gap can also lead to decrease in ventilation system efficiency due to recirculation of air flow and associated shock losses. Air gap height can also have a profound effect on the variation of cave airflow resistance (Erogul et al., 2015, 2017). The knowledge of cave airflow resistance is also important for predicting the intensity of an air blast. Cave airflow resistance is a function of cave properties such as broken rock size, air gap, and porosity inside the cave zone (Baysal et al., 2017). Initially, a scaled experimental model with a forcing system was developed to investigate the airflow behavior through the cave, however, this model couldn’t provide an observable change in the airflow resistance when the cave properties were changed (cave porosity, and airgap) This was attributed to the difficulties associated with forcing system in terms of achieving lower porosity values with the available material (lightweight shipping boxes) for simulating broken rock inside the cave zones, and controlling air leakage from the model (Ajitha et al., 2018)."

Jan 1, 2019

By K. Sakai, M. Miyaue, T. Aoki, T. Tani, S. Tanaka, N. Kudo

In the planning stage of a tunnel, due to limited available technology in the geological survey and the financial restriction, tunnel supports are often designed from unsatisfactory information, and the tunnel construction is started. Therefore, "observational construction" is carried out in the construction stage, in which the design is rationally verified and modified by observations/measurements. Moreover, the ground conditions ahead of a tunnel face must be predicted for efficient and safe tunnel construction. The authors have examined effective prediction methods to the ground conditions ahead of a tunnel face under construction of a mountain tunnel (Aoki et al., 2010) in view of the established method (Schubert et al., 1995). Though the prediction method of Schubert et al. requires the displacement in the direction of tunnel axis, it is difficult to obtain its accurate data by the electro-optical distance meter. Then, we have proposed a method that uses tilt sensors installed at the tunnel crown near the face to obtain the slight tilting information. To measure inclination of the tunnel crown, this inclinometer was originally developed as a daily management measurement, such that the geological condition and its possible change behind the face could be detected early, and a steady advance and construction safety could be ensured. This paper describes the method of forward prediction mechanism and advantages of this proposed method. It then presents the typical results of a field demonstration test at a tunnel under construction. Lastly, the predictable range from the stratum boundary at which ground stiffness changes are discussed based on the results of three-dimensional numerical analysis.

Jan 1, 2015

By A. Mortazavi, H. Nasab

"The storage of petroleum products on surface is associated with difficulties and limitations. Accordingly, a viable alternative is to excavate underground space in rock and provide a safe way for oil storage. Soft rocks such as salt domes provide good conditions from environmental and operational points of view. The potential for high-volume storage and low permeability are encouraging aspects for oil storage in salt domes. The complicated shape of oil storage caverns, the complicated behavior of salt rocks, and boundary conditions associated with large underground openings are important challenges in the design of oil storage caverns. The aim of this paper is to delve into the stability and deformation mechanisms of storage caverns created in salt domes. A parametric study of effect of the cavern size, orientation, and depth is carried out as a function of ground stress regime. The stress field and deformation mechanisms are calculated for each case aiming at providing design guideline.INTRODUCTIONOne of the most popular soft rock that is used for underground oil storage is salt rock (halite). Salt rock has particular characteristics which makes it suitable for oil storage. Salt rock has several advantages for oil storage, these are: high production rate, high degree of availability, short filling period, high level of safety and low permeability [1]. The low permeability is due to the fact that halite deforms in a plastic manner over a wide range of pressures, temperatures and rates of deformations. This property prevents joints or gaps opening up in the formation, thus preventing the escape of liquids and gases. The state of stresses around the cavern in salt domes depends on the depth of the cavern (initial stresses and rock mass temperatures are increasing with depth), the in-situ stress state within the rock mass, and the internal oil pressure in the cavern. Furthermore, the salt creep behavior and the cavern geometry are influencing stress redistributions during loading and unloading phases.Rock mass structure, cavern geometry, material behavior and cavern operation patterns require complex physical models to describe the load-bearing behavior of the geomechanical structure. The determination of stress, strain and deformation in the rock mass due to cavern construction and operation are complex problems which can be evaluated employing numerical tools such as the Finite Element Method (FEM) or Finite Difference Method (FDM). In this study, the finite difference method was used to evaluate the behavior of oil storage cavern in salt rock."

Jan 1, 2015

By Wouter Bleeker, Isabelle Cadieux

"Abstracts of theses related to mineral deposit studies and exploration, completed at geology or earth science departments of Canadian universities, have been compiled for the period 1991 to mid-l993. Part I, presented in the June 1994 issue of the CIM Bulletin, gave a listing of thesis titles. Part II, which consists of edited abstracts of these considered to be of direct application to mineral deposit studies and exploration, is presented under various themes as follows;A. Kimberlites, Other Alkaline Intrusions and Related Studies;B. Volcanogenic Massive Sulphide Deposits and Related Studies;C. Mineral Economics;D. Mesothennal Gold Deposits, Other Gold Deposits and Related Studies;E. Magmatic Nickel-Copper, Platinum Group Element, and Chromite Deposits and Miscellaneous Platinum Group-related Studies;F. Granite and Pegmatite-related Deposits and Porphyry Deposits;0G. Diverse Hydrothermal Deposits, Sediment-hosted Copper Deposits and Mississippi Valley Type Lead-Zinc Deposits; andH. Uranium-related studies, Evaporites and Exploration GeophysicsAbstracts related to themes A. B and C are presented in this issue; the remaining abstracts will be presented in future issues."

Jan 1, 1994

By L. Chunpongtong

ABSTRACT Oil sands production occurs on a massive scale, making orebody estimation a challenge. In rainy conditions, operators can have difficulty accessing ore at the mapped location. Without enough inventory as a buffer, the high-cost stockpile is depleted quickly, necessitating the removal of significant amounts of overburden and interburden to meet plant feed requirements. The inventory curve—a plot of ore inventory on a period-by-period basis—plays an important role in selecting an appropriate scheduling scenario. This paper presents a programmable method for creating an inventory definition by using a pit optimization tool.

Jan 1, 2014

By Yusuke Yamamoto, Mineo Asano

"The present study investigated the texture transition during secondary recrystallization in the AA5182 sheet. During the initial stage of annealing, the texture showed a weak Cube orientation as the primary recrystallization texture. During the secondary recrystallization with abnormal grain growth, the area ratio of the {hkl} <011> orientations increased by consuming the other orientations. The texture transition was calculated by the 2-D Monte Carlo simulation with the misorientation dependency. When the higher grain boundary mobility was set in the specific range of the high angle misorientation, the orientation preferential growth of the RW {100} <011> orientation was reproduced. However, other {hkl} <110> orientations could not be well reproduced by the misorientation dependency.INTRODUCTION Crystal orientation and texture are important factors for aluminum sheet products from the standpoint of mechanical property, formability and isotropy. The recrystallization texture results from the orientation preferential growth from the rolling deformation microstructure and the texture (Alvi, Cheong, Suni, Weiland, & Rollett, 2008). Texture development has been a topic of intense research for decades with advances in analysis methods, e.g., orientation mapping (OIM) and computer simulations (Fjeldberg & Marthinsen, 2010; Ivasishin, Shevchenko, Vasiliev, & Semiatin, 2006). The grain boundary characteristic is considered to be a key for the orientation preferential growth. In the case of the recrystallization from the deformed microstructure, not only the grain boundary characteristic, but also the dislocation density and the subgrain size affect the nucleation and the grain growth (Engler, Löchte, & Hirsch, 2007). On the other hand, in the case of secondary recrystallization, the dislocation density and the subgrain size can be ignored and the effect of the grain boundary characteristic can play a significant role in the grain growth. There is intense research about the texture development during secondary recrystallization in aluminum alloys and it was reported that coarse {hkl} <011> grains were formed during the secondary recrystallization (Suk, Shin, & Huh, 2006; Rios, & Gottstein, 2001). However, the mechanism of forming the {hkl} <011> grains has not been fully clarified. In the present study, the effect of the grain boundary characteristic on the orientation preferential growth was investigated by EBSD analysis and Monte-Carlo (MC) simulation."

Jan 1, 2018

By A. L. Valdivieso

"The correlation obtained by plotting pH of maximum adsorption of dextrin versus the isoelectric point of involved metal hydroxides can be used to predict the depressing effect of dextrin on flotation in ""pure"" sulfide mineral systems. Sulfides are strongly depressed by dextrin whenever their surfaces are coated by the corresponding metal hydroxide. The efficiency of dextrin as a depressant is affected by the adsorption of the sulfhydryl collector. Hydrolyzable cations modify this relationship in flotation of sulfide ores. This type of deviation of the real-life systems from the predictions based on the behavior of the pure systems shows the possible ways that could be followed to further improve the obtained correlations. Advances in Mineral Processing Science and Technology Proceedings of the 48th Annual Conference of Metallurgists ofCIM Sudbury, Ontario, Canada Edited by"

Jan 1, 2009

By L. S. Almeida, U. A. Courbassier, C. T. Guimãaraes, M. N. Souza, V. L. Silva, H. P. Dias, G. A. Bicalho, B. S. Rocha, P. N. Rodrigues, A. Carnevale

During primary aluminum production the anode changing is a very important task. So improvements on it will be essential to avoid disturbance and have a better operational control. After anode changing a good current distribution will be guaranteed using a cavity cleaner and precise anode setting. Albras switching a manually anode setting to an automatic one solved the setting problems. In this paper it will be shown some pot line results and the improvements on workers ergonomic and safety conditions. The device was developed in a partnership between Albras and Pesto.

Jan 1, 2006

By K. E. Prince, S. Burling, R. J. Ring, M. K. Maley, W. R. Taylor

Vanadium occurs as a component of carnotite, which commonly occurs in calcrete type ores, and in association with uranium in some sandstone-hosted deposits. Increasing demand for vanadium, which is used in high-strength steel and Vanadium Redox Flow Batteries (VRFBs), is offering some uranium producers a potential option for by-product vanadium recovery to improve project economics at a time when uranium prices are low. This paper presents the results of recent optimisation studies on the Bigrlyi deposit for the recovery of both uranium and vanadium. The impact of carbonate leaching conditions on uranium and vanadium extraction from a range of carnotite-in-calcrete ores is also examined, with vanadium extraction limited by the proportion of non-carnotite vanadium present in the ores. The findings are particularly relevant to developing projects as results show that elevated vanadium content in ore does not necessarily equate to a high vanadium extraction in leach.

Jan 1, 2020

By S. Uddin

Microsegregation manifests its effect on microstructural evolution of cast or welded alloys which in turn influences their important mechanical and electro-chemical properties. In the above context, mathematical models of microsegregation have proven to play an important role in estimating the nature and predicting the effects of this phenomenon in wide varieties of solidification processes. Microsegregation models are useful in designing new commercial alloys, in estimating the homogenization time for the post-process heat treatments and in many other practical applications. In this study, two semi-analytical models of microsegregation were developed to predict the concentration field of solute in the liquid and solid regions for dendritic solidification of binary metallic alloys. Both models assume that the growing dendrites are cylindrical in shape. This assumption is more realistic compared to the common assumptions of plate like dendrites that most of the earlier researchers employed in their microsegregation modeling study. The solute redistribution profile, in the developing solid layer, necessary to determine the back diffusion parameter was derived from Fick&apos;s second law for the model without coarsening. The application of this parameter in a wide range of conditions and the use of its basic form in the model with coarsening has been verified. The concept of coordinate transformation and enhancement of back-diffusion Fourier number were used in deriving the model which took into account the coarsening of dendrites. The models are then extended to deal with rapid solidification and peritectic transformations and the results were compared with relevant experimental data for Aluminum and other alloys. A good agreement between model predictions and experimental results was found.

Jan 1, 2007

By M. Savich

A graphical method has been developed for the evaluation of the U.S. Occupational Safety and Health Act Noise Exposure Index and the Equivalent Continuous Sound Level. The method makes use of a noise survey form and a mechanical integrator with two sliders, and is less tedious and susceptible to error than alternative methods. The graphical method is adaptable to various codes for noise exposure and may be used with any instrument that measures noise level. One example of its application to a practical situation in a Canadian mine is given to demonstrate the procedure .

Jan 1, 1978

By M. Bavand-Vandchali, F. Golestani-Fard, S. Khalili, S. Rowshanfekr-Fallah

In the secondary metallurgy of steel, the availability of ladles plays an important role in decreasing the production cost. The refractory lining, therefore, should satisfy optimized quality to grant higher heats. This paper reports the results of an investigation carried out in Iranian Mobarakeh Steel Company in order to increase the lining life of ladles by employing different types of MgO C and Al203 - Mg° - C. The zoning concept was used in replacing the conventional refractories either in slag line or the lower parts of ladle. The number of heats could be improved to almost two times as before. The results are explained in terms of refractory quality as well as zoning approach. The economical impact of this improvement will also be analyzed.

Jan 1, 2004

By E. Paransky, M. Rigaud, G. Paschek, S. Palco

Some of the negative impacts of carbon addition on the strength of castables are yet to be overcome in order to fulfill its potential benefits for oxidation resistance. This paper reports the results of recent studies conducted at CIREP on the effects of different types of carbon additives on the thermo-mechanical properties of magnesia-based castables. Experimental techniques included measurements of the hot modulus of rupture (HMOR), hot modulus of elasticity (HMOE), as well as the wedge-splitting test (WST). The comparison of evolving microstructures was carried out employing scanning electron microscopy with microanalysis attachment (SEM/EDS) and X-ray diffraction (XRD). HMOR values of 12 MPa at 1300°C have been reached in MgO-Si02-C castables containing up to 7% carbon.

Jan 1, 2004

By R. W. Seedsman

In 1984 and 1985, two 7.6m diameter TBM tunnels were driven from the Donkin-Morien peninsula in Nova Scotia to access the Harbour coal seam. The design of the ground support was based on identifying zones of rock failure through the application of the Hoek Brown failure criterion and the early use of finite element analyses. In 1992, the mining project was abandoned and the tunnels allowed to flood. Monitoring data from the tunnel was subsequently used as a case study in the development of the concepts of brittle rock behaviour. In 2007, the tunnels were pumped out as part of a feasibility study into the reintroduction of longwall mining into the coalfield. There is a good match between observations of the collapse zones in the roof and sides of the tunnel and a simple elastic analysis using brittle parameters, a spalling limit of 5, and a low independent shear modulus. The brittle analyses form the basis of the design for the resupport of the tunnels.

May 1, 2009

The mining industry has generally been slow to apply ion exchange processes to hydrometallurgical applications even if ion exchange offers an ideal solution for a particular problem. Two notable exceptions are in gold and uranium recovery. The largest application of ion exchange in the metals processing industry has been the use of resin-in-pulp (RIP) for gold recovery as an alternative to activated carbon. Iron is a ubiquitous impurity in hydrometallurgical solutions. In many cases, bulk removal of iron from the process solutions is accomplished by precipitation. However, precipitation for iron control is often accompanied by losses of base metals by co-precipitation. Increasingly, the option of ion exchange for removal of smaller amounts of iron from process solutions has been favoured. A number of applications have been developed and proven at the commercial scale for the removal/control of iron from a range of metal processing solutions. This paper provides an overview of the application of ion exchange for iron removal from a range of metal processing operations, including Cu, Ni and Co solutions. A number of case studies are provided which review operational and resin regeneration strategies and the impact upon the commercial operation of metal processing with improved iron control.

Jan 1, 2006

By Jim Cooney

Background ?1990s saw massive changes in South African mining industry ?over 100,000 jobs lost as the industry restructured; ?1999 ?Placer Dome purchased a 50% interest in South Deep (WAL), a mine located just outside Johannesburg ?This was the first major post-apartheid foreign investment in the South African mining industry The Situation ?Placer Dome decided to lay off 2560 mineworkers (one third of the workforce) from the South Deep Mine to restore the mine to economic viability. ?Unemployment in South Africa was over 25%, and the retrenched mineworkers had few skills with which to make a living. Policy Context ?Placer Dome was committed to: ?global corporate policy of Sustainable Development, ?demonstrating that its business contributes to the economic and social progress of host jurisdictions. ?Government of South Africa was committed to ?attracting foreign investment to its mining sector with a view to modernizing and enhancing its economic and social viability, ?ameliorating the negative social consequences of structural change without arresting the necessary process of restructuring. ?National Union of Mineworkers was committed to: ?working with the mining industry and the government in implementing a Code of Good Practice on Dismissals and a Social Plan to assist retrenched mineworkers (1999).

May 1, 2006

By Lizelle Glaner

An investigation was carried out by Mintek to investigate the influence of additions of gold to ?Fecraloy?, alloys based on Fe-Cr-Al. The aim was to try and improve the oxidation resistance of the ?Fecraloy? alloys at elevated temperatures over extended periods of time. The ?Fecraloy? alloys are very oxidation resistant alloys already employed in industry as substrates for metallic catalysts in auto-catalyst systems for high performance cars. Since their life and durability is limited by the slow, but steady, oxidation of the substrates, any change in the growth or stability of the oxides could be an improvement.

Oct 1, 2003

By Shugang Li

Coal and coal-bed methane are valuable energy resources. If they can be extracted simultaneously and safely, the triple purposes of mine safety production, new energy resource supply and environmental protection can be fulfilled. After mining, the mining induced fissure distribution feature and methane delivery behavior in overlying strata were closely related to the relieved methane degasification. Using physical simulation and numerical simulation, it was explained that the distribution feature of mining induced fissure was the Elliptic Paraboloid Zone (EPZ) in three-dimensional space. Based on the key stratum theory, the types, parameters, characteristics and dynamic evolution behavior of the mining induced fissure EPZ were analyzed. Applying environmental fluid mechanics and the mass transfer theory, the relieved methane floating-diffusion equation of the EPZ was established, and the corresponding transport process was analyzed. Using the field practice of relieved methane degasification in Tianchi Coal Mine, it explained that the mining induced fissure EPZ was the storage and delivery area of relieved methane. The degasification effect will thus be useful if the drainage system is laid in the EPZ. Such studies can provide the theoretical basis and technical support for the safe simultaneous extraction of coal and methane.

Aug 1, 2013

By Seong-Taek Lim

Recently, 7xxx aluminum alloys have been evolved into new variants for thick semiproducts which have low amount of 2nd phases and low quench sensitivity. Commercial 7xxx alloys, especially in the thick forgings made of big ingots, often entail microstructural inhomogeneities and concurrent poor mechanical properties due to limited heating ranges and slower quench cooling. In this study, high strength aluminum alloy 7175 and 7050 are adjusted as an attempt to control the equilibrium phases (M-, T- and S-phase) to have optimum microstructure for the thick forging applications. The effects of the relative content of (Zn, Mg, Cu) on the evolutions of the coarse equilibrium phases, hardening response and resultant mechanical properties are investigated. Equilibrium phases (M,T,S) are evolved depending on the constitutional effect, primarily the change of Zn:Mg ratio, and cooling rate following solutionizing. The formation of the T- and S-phases is effectively controlled, and M-phases are homogeneously precipitated in the adjusted (dilute and high Zn:Mg ratio) alloys. It provides extended heating range and lower quench sensitivity than conventional alloys. The attempts ensure the microstructural homogeneity and improved properties, and is expected to be uniquely applicable in 7xxx thick forgings.

Jan 1, 2004

By W. D. Madeley

Synthetic minerals were made from pure starting materials and galena samples were doped with the title metals. Microscopic, microprobe and X-ray examination confirmed that the dopeants were in solid solution. Paired flotations in a Hallimond-tube apparatus were performed to determine relative flotation response using Aerofloat 238 promoter. Results of these tests show that silver-doped galena floats more readily than pure galena and that galena doped with bismuth floats less readily than pure mineral to a 95% confidence level. Galena doped with both silver and antimony as AgSbS2 shows no detectable effect. Antimony-doped galena followed the expected trend, but not to 95% confidence. The results are consistent with the theory that flotation by thiol-type anionic collectors is enhanced by p-type semiconduction.

Jan 1, 1978