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By L. Telfer

Summary During Palaeozoic time, there were deposited in the Canadian Rockies four beds of phosphate rock, ranging in age from Mississippian to Jurassic. Two of these beds are of probable economic importance if some means of separating the phosphate from the gangue can be devised. All the more important beds of phosphate rock so far discovered are just behind the front ranges of the Rocky mountains, within fifty miles of the prairie lands of Alberta. Mining conditions are favourable, with an abundance of timber and ample power available. The phosphate beds are all of the sedimentary type, and they all occur, apparently, at the same stratigraphic horizons over a wide area. The conditions necessary for deposition evidently occurred at several different periods in geological time, and were widespread. The most important factor appears to have been the condition of the land surface surrounding the basin of de-position. Both oolitic and nodular phosphate were laid down under nearly similar conditions. Introduction Following the discovery of phosphate rock in Idaho and Montana, search was commenced in Canada to determine whether formations of similar age in the Canadian Rockies carried similar beds of phosphate. The most widespread search has been that undertaken by the mines department of the Consolidated Mining and Smelting Company of Canada. The following paper will discuss some of the results of this exploration.

Jan 1, 1933

By W. H. MacLean, S. Liaghat

The Key Tuffite is a thick (0.3 m to 6 m) and laterally extensive (-10 km) cherty, sulfide-bearing tuff unit in Archean greenstones in the Matagami mining district in northwestern Quebec. It lies at the contact of the Watson Lake Group and overlying Wabassee Group volcanic rocks, and is host to major Zn-Cu volcanogenic massive sulfide deposits. The tuff component is highly altered and its volcanic precursors are not identifiable by petrographic means. The tuff is mixed with a volcanic exhalative component comprising chert, carbonate and sulfides (pyrite, pyrrhotite, and minor sphalerite and chalcopyrite). The normative mineral composition of the Key Tuffite is 33% quartz, 28% sulfides, 16% sericite, 8070 carbonate, 6% chlorite and 9% other minerals. In the vicinity of the Bell Allard and Orchan mines, the precursor tuff components are identified using immobile major and trace elements, as Watson Lake tholeiitic rhyolite (Zr/Y = 1.5 to 3.5, LaN/ybN = 1.7 to 2.8, SiO2 = 72.5 ± 1.2 wt %, and Wabassee calc-alkaline andesite (Zr/Y = 9, LaN/YbN= 4 to 8, SiO2 = 56% to 65%). Immobile element computation techniques were used to calculate mass additions and losses in the conversion of the tuff to the Key Tuffite. Average net amounts of FeP3 (27% total iron), Si02 (14%), Cao (8%), S and K2 (+ 2%), were added, Nap was removed (-2.8%), and MgO was over-all unchanged. Total net mass change was +63%, which comprises mainly exhalative additions, but also includes changes owing to hydrothermal alteration of the tuff component.

Jan 1, 1992

By François Baillargeon

Two types of ore deposit provide the bulk of the world nickel production. They are the hypogene magmatic massive sulfide deposits and the supergene lateritic deposits. Platinum group elements (PGE) are also extracted from magmatic sulfide deposits. Recent sky-rocketing price of palladium has prompted the mineral industry to seek alternative resources. In such a manner has emerged the Lac-des-Iles type of target, a very low sulfide-bearing bulk tonnage type of deposit. Furthermore, unconventional (e.g. non-magmatic) types of deposit are now sought more intensively (Wilde et al., 2003). Considering both this trend of the PGE Industry, and that only a few magmatic deposits account significantly for the world nickel production, someone may wonder if a diversification of the hypogene nickel resources base would not be needed in the near future. Laterites are residual deposits developed on ultramafic rock under wet tropical climate. Are all ultramafic protoliths equal to generate high-grade lateritic deposit? Are some preweathering processes important to generate favourable ultramafic protoliths? The mineralogical heterogeneity of some ?dry? lateritic nickel deposits renders their ore beneficiation difficult. Is the type of nickel-bearing mineral found in the protolith a significant factor influencing the laterite heterogeneity? To contribute to answer all these questions, we have undertaken a research project on the nickel occurrences of the southern Quebec serpentinite belts. Why choosing this specific region for such a project? First because, due to continuous mining of asbestos ore since 1870, the serpentinite belts of this region are among the best exposed and studied in the world. Secondly, this region host a complete spectrum of nickel deposits that have been described before in the scientific literature. Furthermore, this region is slightly to moderately metamorphosed which make it perfectly suited to study the departure from magmatic nickeliferous paragenesis through various metamorphic conditions. As a matter of fact two orogenic events affected this region, the Taconian, in Ordovician time, and the Acadian during the Devonian. The magnitude and the timing of these dynamo-metamorphic events vary considerably through the region (Gauthier et al., 1994). These variations are now well constrained due to precise age dating.

May 1, 2003

By H. Wotruba, J. Heizmann

"The use of shotcrete is a mandatory means for rock support and therefore for safety in many underground mining operations. If shotcrete gets into the flotation feed though, it can negatively influence the flotation process. This especially occurs when sublevel stoping, cut-and-fill or room-and-pillar methods are applied because as the mining face moves on, formerly applied shotcrete layers are mined together with the ore.As shotcrete does not differ significantly from fluorspar ore in its physical properties it gets moved through the comminution process and is fed to the flotation plant like the ore. To prove the influence of shotcrete on the flotation process, a laboratory test series was conducted at the Unit of Mineral Processing (AMR) of the RWTH Aachen University. The shotcrete grade of the flotation feed was varied between 0 and 10% through addition of pure shotcrete. Flotation parameters and also reagent dosage were held constant apart from the addition of the pH regulator, which was dosed to reach a constant pH of 8 at the flotation start. Results showed that with increasing shotcrete grades in the flotation feed the fluorspar recovery as well as general mass recovery decreased. The enrichment factor of Fluorspar also decreased with increasing shotcrete grades in the feed.In an effort to eliminate the shotcrete contamination of the flotation feed, a feasibility study for use of sensor-based sorting prior to the comminution process was conducted. Rock sorting not only reduces the bad influence of shotcrete on the flotation process, but also reduces comminution costs. INTRODUCTIONShotcrete is used in underground mining on a regular basis. It is used for rock support and therefore to increase safety in the underground mining environment. In mineral processing the presence of shotcrete can cause difficulties for example in the concentration processes. In flotation the highly sensitive reagent mixtures can be disturbed by the chemical activity of shotcrete and therefore recovery rates and selectivity of the process can suffer.Shotcrete is a special form of concrete which is applied pneumatically with high velocities and is compressed by its impact energy. Since the process is especially suitable for work in difficult environments and overhead areas, it is established in underground mining for many years. Shotcrete is not only applied in pre-processing of the mines, but particularly of use for cut and fill, as well as room and pillar mining methods. There it is used to secure excavation chambers. When the mine face is secured with shotcrete and subsequently the mining continues, the applied shotcrete will automatically be mixed with the ore."

Jan 1, 2016

By Greg Gosson

"Early efforts to develop formal reporting systems to quantify and classify mineral deposits date back over 100 years. (e.g. Hoover 1909: “Proved, Probable, Prospective Ore”). This was at first driven by mine operators’ need for reliable estimates of what their mines could produce. Disruption of transportation routes by world wars prompted western governments to recognize the need for assessments of strategic sources of metals and minerals that could support domestic industry during times of crisis. Categories were created to quantify mineral potential which were additional to those of mine reserves. Terms such as hypothetical and undiscovered resources entered the lexicon. Capital markets serving the mining industry were traumatized during the latter part of the 20th century by undisciplined and fraudulent disclosure by exploration companies of mineral deposit potential. Government securities regulators pressed for the development of credible reporting codes (e.g. SEC Industry Guide 7: 1981; JORC 1989; SAMREC 1994, CIM 2000). Representative organizations from the major western mining countries generally agreed that there should only be three categories of mineral resources (measured, indicated, and inferred) and two categories of mineral reserves (proven and probable). This was formalized in 1997 with the “Denver Accord”. Acceptance of the standard terminology may have been the easy part, because the challenge for the 21st century is to get general industry acceptance and agreement of the principles behind the definitions of each category. There has been noticeable movement towards this objective in the last few years. This is reflected in part in the updated reporting codes by JORC 2004, CIM 2005; SAMREC 2007; SME 2007; and PERC 2008, and the development of the CRIRSCO International Reporting Template 2007."

Jan 1, 2003

By R. MacRosty

The demand to increase production levels in smelting furnaces has driven the increase in the power levels. Consequently, greater cooling capacity of the furnace shell has been necessary, resulting in the widespread use of water-cooled elements to protect the refractory linings. Since water ingress into the furnace is an explosion hazard, monitoring and maintenance of the water-cooled elements is of key importance. Some of Hatch's recent research and development efforts have been focused on methods to provide an increased level of monitoring of water-cooled furnace elements; this paper focuses on two technologies developed for this purpose. The first involves the installation of a fibre optic temperature sensor in a water-cooled tapblock. The sensor is capable of providing high accuracy temperature measurements with a fine spatial resolution throughout the tapblock. Hatch has already developed a diagnostic system that uses multivariate statistical analysis to interpret the large quantities of data generated by the sensor. A second technology under development is concerned with enhancing the operating integrity and safety through detection of leaks in the water circuits. A successful leak detection strategy requires minimal maintenance and the ability to detect minute leaks. An instrument that meets these criteria has been investigated and is currently under development. This paper focuses on the technology and results from the test work that has been completed to date.

Jan 1, 2007

By G. Marchand, R. H. Hay, E. C. Pearson

"AbstractA polishing .technique is described together with two anodic etching methods for aluminum and its alloys. Some of the optical and structural characteristics of the film formed by •these etching methods are discussed and it is shown to what degree these properties of the film are related to the crystallographic orientation of the metallic substrate. Applications to the study of recrystallization and twinning phenomena and to the study of plastic deformation, banding, and texture estimation are discussed. Micrographs are shown .to illustrate the manner in which the technique is particularly well suited to the study of such phenomena.IntroductionThe physical metallurgist is constantly faced with the problem of polishing and etching of metallic sections. Mechanical polishing is tedious, time consuming, and not applicable whenever a surface entirely free from plastic deformation is required. Etchants are generally required to reveal the grain structure in order to determine its size, shape, and regularity, or to bring up constituents. In the case of aluminum, the .most common etchant to reveal grains is a mixture of three acids: HC1, HN03, and HF. This etchant is fairly satisfactory on certain alloys and for certain metallurgical conditions but in general fails to give a good definition of the grain on castings, on highly alloyed products, and whenever the grain is smaller than 100 microns in diameter. Besides size and shape, a grain, or crystal, has an orientation and may be endowed with several types of imperfections."

Jan 1, 1952

By Deni Pageau, Deni Caron

"This paper describes the operations of the open pit and emphasizes particular aspects of Les Mines Selbaie. The open pit as well as its related services were incorporated into a complex which includes an underground mine and a concentrator. The equipment was chosen with the objective of auto-sufficiency during each phase of mining. The paper outlines the organization and the methods used in each step of mining, notably: drilling, blasting, loading, transporting and crushing. The responsibilities of the Engineering Department are also outlined from the conception of the open pit to the latest follow-up methods. A short resume of the results which have been obtained as well as suggestions for improvement are provided.Layout in Consideration of Main SiteThe A-I zone deposit is located I km from 8 zone. Open pit mining of A-I zone required the regrouping of different services to those already existing.I. The crusher was placed in an area close to the concentrator in order to minimize the length of the conveyors and to provide space for the crushed ore reserves (50000 tonnes).2. The location of the service building (warehouses, mine offices, maintenance, engineering and geology) raised a few problems. Because of the multiple services provided therein , it was impossible to fulfill all the requirements, and the garage in itself is located a fair distance from the pit. Added to this inconvenience is the fact that heavy equipment regularly travels throughout the main yard.3. The storage of explosive magazines has been changed to obtain more surface space and meet government regulations.4. A space has been provided for minor repairs in the garage used during exploration. A trailer was installed next to the garage to provide a lunch room for the employees working at the open pit."

Jan 1, 1990

By S. A. R. Keneti

Predicting the geomechanical response of the shale gas material during hydraulic fracturing operation in the field needs better understanding of their geomechanical behaviour under laboratory testing. Anisotropy is considered as a critical factor during investigation and analysis of deviated boreholes, borehole stability, stress-strain and strength behaviour, generation and propagation of fracture and fluid flow. In this study, compressive elastic modulus (Ec) of the Montney shale has been investigated in two perpendicular directions: unconfined compressive strengths test was conducted on the Montney sample to measure its Ec in the vertical direction. This value then was compared to the Ec value in the horizontal plane (i.e. foliation plane) which was previously measured throughout a Brazilian test by Keneti and Wong (2011). From the results, the representative values of Ec in the vertical and in the horizontal directions were found as 25 GPa and 40 GPa, respectively. Computer tomography technique was also employed for the experimental data interpretation.

Jun 1, 2012

By K. Forsberg, A. Rasmuson, R. Rodriguez Varela, J. Martinez De La Cruz

"This study analyzes the separation of rare earth elements by means of a supported liquid membrane (SLM) with the final objective of recovering REE from an apatite concentrate (Alemrajabi, Forsberg, & Rasmuson, 2015; Mohammadi, Forsberg, Martinez de la Cruz, & Rasmuson, 2015). In this study, the feed phase consists of an aqueous phase containing REE, the membrane phase contains the organic solvent and carrier (D2EHPA and EHEHPA), and the stripping phase is a hydrochloric acid solution. An evaluation of mass fluxes, separation efficiency, and membrane performance is conducted. In order to analyze the suitability of liquid membranes in the extraction of REE, a deeper insight into the mechanisms causing instability is needed. In this study, surface tension is considered as the key factor of Marangoni instabilities and spontaneous emulsification.INTRODUCTIONThe demand of REE and their compounds has increased considerably due to their special physicochemical features that make them crucial elements for numerous high-tech applications, including wind turbines, hybrid cars, mobile phones, and defense technologies. They are also extensively utilized in traditional industries such as nuclear energy, petroleum, metallurgy, agriculture, and textiles (Xie, Zhang, Dreisinger, & Dyole, 2014; Zhang, Wu, Bian, & Zeng, 2014).Solvent extraction is widely used for the separation of REE (Xie et al., 2014; Zhao, Huo, Pan, Li, & Liu, 2014). Di-(2-ethylhexyl)-phosphoric acid (D2EHPA) and 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (EHEHPA) are two of the most effective extractants for the separation of rare earth elements among organophosphorus extractants (Gupta & Krishnamurthy, 2005). However, the difficulty in stripping loaded D2EHPA extractant, especially for heavy REE, has limited its utilization. Yttrium can be stripped at lower acidities in EHEHPA systems compared to D2EHPA systems (Gupta et al., 2005), but the extraction efficiency is lower. Conventional solvent extraction by mixer-settlers is restricted by its large solvent inventory and loading limits, and suffers from phase disengagement, emulsification, loss of solvent, and flooding problems (Swain, Jeong, Lee, & Lee, 2007). In this context, supported liquid membranes (SLMs) present a potential alternative due to their advantages, being low solvent inventory, process simplicity, low energy and operational costs, great enrichment ratio, and combination of extraction and stripping into one single step. A SLM is a system in which two aqueous phases are separated by an organic liquid membrane suspended in the pores of a porous support by capillary forces. One of the aqueous phases is the feed solution with the solute and the other is the stripping or receiving solution. The solute diffuses through the liquid membrane and then is extracted into the stripping solution (Kislik, 2010)."

Jan 1, 2016

By James R. Hein, Jane Reid, Robert W. Embley, Se-Won Chang, Randolph A. Koski

"Abstract - This is the first reported occurrence of an active hydrothermal field in an oceanic fracture zone setting. The hydrothermal field occurs in a pull-apart basin within the Blanco Fracture Zone (BFZ), which has four distinct mineral deposit types: (1) barite mounds and chimneys, (2) barite stockwork breccia, (3) silica-barite beds, and (4) silica, barite, and Fe-Mn oxyhydroxide in sediments. All deposit types contain minor amounts of sulfides. In barite stockwork, silica-barite beds, and mineralized sediment, Ba, Pb, Ag, S, Au, Zn, Cu, Hg, Tl, As, Mo, Sb, U, Cd, and Cu are enriched relative to unmineralized rocks and sediments of the BFZ. Fe and Mn are not enriched in the barite stockwork or silica-barite beds, but along with P, Co, and Mg are enriched in the mineralized sediments. Silver contents in deposits of the hydrothermal field range up to 86 ppm, gold to 0.7 ppm, zinc to 3.2%, copper to 0.8%, and barium to 22%.Mineralization occurred by diffuse, low to intermediate temperature (mostly <250°C) discharge of hydrothermal fluids through pillow lavas and ponds of mixed volcaniclastic and biosiliceous sediments. Bacterial mats were mineralized by silica, barite, and minor Fe hydroxides, or less commonly, by Mn oxyhydroxides. Pervasive mineralization of bacterial mats resulted in formation of silica- barite beds. Silica precipitated from hydrothermal fluids by conductive cooling and mixing with seawater. Sulfate, U, and rare earth elements (REEs) in barite were derived from seawater, whereas the REE content of hydrothermal silica deposits and mineralized sediments is associated with the aluminosilicate detrital fraction. Fe-, Zn-, Cu-, Pb-, and Hg-sulfide minerals, Ba in barite, and Eu in all mineralized deposits were derived from hydrothermal fluids. Manganese oxides and associated elements (Co, Sb, Mo, W, Cl, and Cu) and Fe oxides and associated elements (Be, B, P, and Mo) precipitated as the result of mixing of hydrothermal fluids with seawater."

Jan 1, 1999

By B. J. McKay, K. Schneider, H. B. Nadendla

"A series of experiments were conducted to assess the impact of zinc additions on the morphology and soundness of the interface of Al-Mg compound castings. It was found that high amounts of zinc (>15wt%) are necessary to affect the morphology and microstructure of the interface. At these zinc concentration levels, the formation of the zinc-rich phases t1 and ? were observed along with the Al-Mg intermetallic phases ß and ?. The micro hardness of all phases across the interface was found to be similar, ~200 Hv. This even hardness gradient is thought to avoid mechanical failure in the interface under load. In samples containing large concentrations of zinc (>15wt%), the formation of bubble shaped voids as well as the complete transformation of the aluminium alloy was observed. While the exact mechanism causing the voids has not been identified it thought to be connected to the Kirkendall effect. INTRODUCTION Conventional single material components are increasingly failing to meet the demands, in terms of cost and performance, of the transport industry. Compound castings have been identified as a promising alternative as they possess a number of benefits (Bührig-Polaczek, Röth, Baumeister, Nowack, & Sussmann, 2006). Compound casting is described as a process in which a metallic melt is cast around a solid metal shape. Preliminary research has concluded that for the stability of such a resultant hybrid structure it is imperative that both metals form a sound connection via form closure, force closure, or material bonding. A continuous material bond between the two metals is also highly desirable as the formation of a crevice between the metals could lead to galvanic corrosion, particular in a humid environment (Lao, 2013; Rübner, Günzl, Körner, & Singer, 2011). Even though Al-Mg compound castings could offer the biggest potential in terms of weight savings to date only a limited amount of research concerning such structures exists."

Jan 1, 2018

By D. M. MacLean

THE property of Howey Gold Mines, Limited, is situated at Red Lake, Ontario, one hundred and seventy-five miles east of Winnipeg and eighty miles north of the Canadian National railway. The mine has been a continuous producer since April, 1930, and, at present writing, a total of 3,042,690 tons has been hoisted, giving a production of $6,422,858.55, for a grade of $2.32 per ton. From 1,064,477 tons mined during the past two years, however, the yield has been only $1,389,607.03, or $1.41 per ton (gold at $20.67). Present output is at the rate of about 1,470 tons. per day. THE ORE-BODY AND WALL-ROCK: The Howey ore-body is part of a quartz porphyry dyke, which has. intruded an area of greenstone. The dyke strikes north 65° east, and its dip varies from 85° to the south at the surface to practically vertical below the. 1,000-foot horizon. Both along the strike and on the dip, the width of the dyke varies from 25 to 200 feet, the widest portion occurring below the 1,000-foot level. To the east of the ore-body, the dyke increases in width and finally splits into tongues of porphyry enclosed in greenstone, diorite, and congloJ11erate. To the west, it passes into the adjoining property, its width at the boundary being 100 feet. The rock in the ore-body is hard to drill, but, because of numerous horizontal slip-planes, it breaks well when blasted. This characteristic makes it possible to break large breasts or benches with a relatively small number of holes. The ore broken in this manner is consequently quite coarse, a large part of it requiring secondary breaking.

Jan 1, 1938

By V. Barranco, K. Yliniemi, A. Hubin, B. P. Wilson, D. Janas, M. Lundström, P. Hannula

Typical copper electrorefining electrolyte contains tens of grams of copper, some nickel and a wide variety of impurities. Some of these impurities comprise trace amounts of dissolved precious metals like Ag, Pd and Pt that currently are not fully exploited. This study presents an electrochemical method to recover precious metals via a combined electrodeposition-redox replacement (EDRR) process, where energy is used only to deposit copper during the ED-step, while the RR-step relies on the spontaneous replacement of copper by the precious metals (i.e. cementation). In order to conduct the recovery successfully, process parameters such as deposition potential (EDE), deposition time (tDE), redox replacement time (tRR) and the number of cycles (n) was adjusted. Investigations performed in synthetic electrolyte (40 g/L Cu, Ag = 10 ppm) proved the possibility to recover a high purity silver. Short deposition times (tDE) were found to result in small Cu particles that provided a suitably high surface area for silver cementation. In addition, experiments performed in real industrial electrolytes containing 44 g/L Cu and 54 ppb Ag (Boliden Harjavalta, Pori), demonstrated that EDRR could attain Ag recoveries of between 46–67% in an energy efficient, additive-free manner. INTRODUCTION The raw materials used in the state-of-art primary and secondary copper smelters contain mainly base metals, but also notable amounts of Ag, Pt and other precious metals. These valuable metals distribute mostly into the copper matte during the pyrometallurgical treatment (Tirronen et al., 2017) and end up into the cast anodes. During the electrorefining stage, metals more noble than copper such as gold and platinum, are not dissolved but enrich into the anode slimes. In contrast, silver may dissolve slightly and thus, minor chloride addition is used to retain silver in the slime as sparingly soluble AgCl. Moreover, other metals less noble than copper may also dissolve, such as nickel. Therefore the electrolytes used in electrorefining typically contain substantial amounts of copper, nickel and even arsenic as well as minor metals such as antimony and bismuth. In the Boliden electrorefinery these were reported to be in the magnitude of 51.2– 60.4 g/L of Cu, 10.9–15.8 g/L Ni, 7.2–15.9 As, 0.2–0.4 Sb and 0.1–0.4 Bi with an associated sulfuric acid concentration of 139–155 g/L (Lehtiniemi et al., 2018). Copper is the most noble of the dominating base metals in the electrolyte and is thus deposited on the cathode as 99.99% purity LME-A grade. Anode slimes are collected and subjected to precious metals treatment e.g. via pressure leaching—selenium recovery— Doré smelting—Ag refining—Au/Pt/Pd leaching and reduction process (Ludvigsson & Larsson, 2003). The Pori refinery, operating in Finland since 1941, not only produces 133 000 t Cu cathode and 2300 t nickel sulphate annually but also 66 t silver, 4.6 t gold and palladium and platinum (in year 2017).

Jan 1, 2019

MR. J. F. MYERS, Consulting J3eneficiation Engineer, Greenwich, Conn.: In the written discussion contributed by Mr. F. C. Bond in item ( 2) (page 515), speaiking about the significance of the ratio of mill diameter to the make-up ball diameter, he states: "When this ratio exceeds 100 the power and capacity of the mill are de-creased"; and the paragraph ends with a reference to the 30 per cent ball volume "with some de-crease in mill capacity". I believe this broad statement is incorrect. When we are dealing with a non-cataracting mill, pre-ceded by a good rod mill, there is a slight increase in capacity, but the power does drop. The second point that I consider needs consideration is Mr. Bond&apos;s item (8), Proper Mill Speed (page 516). This paragraph should be qualified to cover single-stage mills only. It does not apply where a rod mill is followed by a non-cataracting ball mill. The statement as is, with no qualification, gives an erroneous idea of proper mill speeds.

Jan 1, 1957

By M. S. King

"A simple method is proposed for determining the long-term deformation behaviour of evaporites. The theory developed can be tested by measuring the change in diameter as a function of time of a vertical mine shaft opposite evaporite strata. Ultimate shaft closures predicted by the theory agree well with those calculated with the very much more complex theory of Serata (1968), provided that sufficiently high octahedral shear strengths are used in the former.An analysis of measurements made in an isolated opening in a Saskatchewan potash mine shows that the octahedral shear strength of the surrounding potash and halite was approximately 500 psi several years after the opening was mined. This value is less than that deter-mined experimentally for halite by Serata. The same data indicate, furthermore, that the in-situ octahedral shear strength is decreasing slowly with time.The current controversy regarding the actual deformation of evaporites will only be resolved by the cooperation of potash producing companies in releasing data on the long-term deformation of their mine shafts."

Jan 1, 1971

By H. Blaha, H. Wagner

"Room and pillar workings in salt mines are preferred sites for underground waste disposal. A critical issue in selecting waste disposal sites is long-term behaviour of such workings. The long-term behaviour of salt pillars is controlled by the pillar geometry, i.e. the height, width and length of pillars and the level of pillar stress. The latter has a strong influence on creep characteristics of salt pillars whereas the width to height ratio of salt pillars determines the strength of pillars and the deformation characteristics of salt pillars.Three different regimes of pillar creep behaviour of salt pillars can be distinguished, namely a stress level below which the rate of creep approaches a value of zero, a stress range where the rate of creep is constant and finally a stress level above which the rate of creep accelerates. Long-term stability of room and pillar workings can be assured only when the pillar stress level falls within the first stress regime. Strength and creep tests on model salt pillars have shown that at stress levels below 40% of pillar strength the rate of creep approaches a value of zero, between stress levels of 40% and 65% the rate of creep is constant but increases with stress level. Above pillar stress levels of 65% the rate of creep accelerates.Long-term measurements of pillar deformation and surface subsidence above relatively shallow room and pillar workings in salt mines have confirmed these observations. Long-term strength of salt was found that be between 60% and 65% of short term strength. The evaluation of salt pillar behaviour on the basis of critical pillar stress levels was found to be superior to the traditional factor of safety concept because it allows relating pillar deformation measurements to actual pillar conditions. The approach described in the paper was used successfully to evaluate the stability of room and pillar workings in a salt mine and to design strategies to stabilise critical pillar workings."

Jan 1, 2015

By Eric Poulin, Anthony Clapperton, Jocelyn Bouchard, Jaime Cristobal Rojas-Montes, Benjamin Legare

"Several grinding mill dynamic simulators have been developed in the last half-century. However, complete circuit simulations are mainly limited to academic investigations, and on-site applications for advanced control or real-time optimization are scarce. One particular issue that has certainly curbed a more widespread use is the time and efforts required for model calibration. This paper illustrates this challenge and presents a calibration method based on dynamic simulation using industrial data and laboratory testwork. The simulator models discussed originate from the work of Austin and Luckie (1972) for grinding mills, and Plitt (1976) for hydrocyclones. A two-stage approach based on a least squares minimization allows determining calibration parameters values. Firstly, laboratory testwork are required for characterizing breakage coefficients of the ore. Secondly, step change responses and their simulation— effect of ore and water feed rates on output flow rates and size distributions—allows identifying transport/mixing conditions. Simulation results are in agreement with actual process responses to variations of feed conditions obtained from a plant survey.INTRODUCTIONDynamic models for grinding circuits has been intensively studied since the 1970's notably by Austin and Luckie (1972b), Klimpel and Austin (1984), Rogovin and Hogg (1988), Napier-Munn et al. (1996), Liu and Spencer (2004), and King (2012) among others. The resulting models primarily serve in simulation applications for process equipment sizing, which incidentally also helps developing a better understanding of comminution operations. An obstacle curbing a more widespread and targeted use of grinding simulation for process control and optimization purposes is the time and efforts required for dynamic model calibration. It remains a cumbersome task that is typically not well detailed in technical papers. This could explain why dynamic process simulators are mainly confined to academic applications."

Jan 1, 2016

By Doug Milne

Linking Classification Systems with each other Similar Parameters between systems Different Rock Mass Properties Rock Mass Classification parameters and geology Different sources of data Commonly Used Rock Mass Classification Systems Q? = Q with SRF = 1.0 RMR? = RMR with no joint orientation correction RMR76 = 9lnQ + 44 RMR?76 = 9lnQ? + 44 RMR76 = RMR89-5 RMR?76 = GSI = RMR89-5 MRMR = ??MRMR

May 1, 2013

By Dallas Bienhoff

Boeing Study Team Participants Andrew Daga & Associates American Aerospace Advisors Hamilton Sundstrand Harris Honeywell ILC Dover Lunar Transportation Systems Oceaneering Orion Propulsion SICSA Thin Red Line USA LSSCA BAA Topic 2: MFHE Definition Minimum Functionality Habitation Element Deployable Habitat DHE Update The Path to Growth

May 1, 2013