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By Y. Chengxian

Many factors about the HIC (hydrogen-induced cracking) resistance of pipelines are discussed in this paper. The main factors that influence the ability of HIC are environmental and material factors. The chemical compositions, non-metal inclusions and microstructure are discussed in detail, while a group of tests on HIC resistance are done according to varying C, S, Mn and P contents in pipeline steels, different experiment time and different strength to the coupon. It is concluded that decreasing the amount of C and S can obtain good HIC resistance; the test time has an effect on the different microstructure of X70; microstructure is the most sensitive factor for the initiation processes of HIC.

Jan 1, 2005

By Farzaneh Abedini, Narain Hariharan, Lucas C. McFarlane, Nikolas A. Romaniuk, Tiffany Thayne

The use of dewatered mine tailings as backfill material (commonly referred to as ‘paste’ backfill), is the most practiced form of backfill in Canada providing significant environmental benefits by reducing the size of external tailings facilities and improved economics through enhanced resource recovery. Paste backfill operations reuse filtered mine tailings with a cementitious binder and water to create a slurry that is hydraulically transported to refill underground stopes, later forming a structural network of cemented tailings in the mine stopes. Unlike typical structural applications that utilize General Use (GU) Portland cement; modern paste backfill operations maximize strength performance by blending Portland cement with ground granulated blast furnace slag (GGBFS) or other supplementary cementitious materials (SCMs). GGBFS and other SCMs offer key performance benefits and carbon reductions; however, the availability of these SCMs is rapidly dwindling in today’s carbon-constrained economy. This paper examines the development of an alternative binder system that provides similar performance and carbon reduction to that of GGBFS for mine backfill operations. The binder utilizes the chemical reaction between a reactive source of aluminosilicates and available calcium from calcium oxide or calcium hydroxide to replace between 50 to 100% of GGBFS. The performance of the binder is examined with insights into the hydration mechanisms that generate mechanical strength in the cemented paste network. Paste backfill slurries require precise engineering to create a material that maintains flowability during pipeline transport and generates enough strength to meet operational targets once placed in the stopes. Engineering of such slurries requires large amounts of water to be added to the binder-tailings matrix, far exceeding the typical water to binder ratios used in concrete mix designs. This characteristic of paste backfill warrants great emphasis on understanding the hydration mechanisms of the binder used in the paste backfill system. GU cement is typically composed of 50-70% tricalcium silicate and 15-30% dicalcium silicate.  The hydration mechanisms of these compounds consume 4 to 6 units of water to mineralize into calcium silicate hydrate cemented phases that result in compressive strength development. Cementitious aluminate and aluminosilicate phases make up 5-20% of GU cement and aid in secondary performance characteristics such as set time. Certain calcium aluminate hydrate phases such as monocarboaluminate and ettringite mineralize 10 to 32 units of water into their crystalline structure. Hydration products such as ettringite are traditionally avoided in construction applications due to their propensity for volumetric expansion after cement setting, leading to micro-fissures and subsequent strength degradation (known as ‘sulfate attack’). This paper proposes that such hydration products benefit the strength development in paste backfill slurries with the aforementioned characteristics due to their greater potential to mineralize free water. The newly developed calcium aluminosilicate binder is designed to replace 50-100% GGBFS or other SCMs used in paste backfill systems and meet operational strength requirements by providing exceptional hydration characteristics through cementitious reactions. Additionally, the aluminosilicates used have a minimal carbon footprint and a secure supply outlook, thereby allowing mine operators access to a low-carbon binder option throughout the mine’s lifespan.

May 4, 2025

Several inorganic reagents and organic polymers were tested as depressants in the single mineral flotation of ultrafine iron oxide and hydroxylapatite with Dowfroth 250 as a frother. It was observed that the inorganic reagents and the low molecular weight polymers generally caused dispersion of the ultrafine particles, and consequently their recovery into froth products more or less equaled the recovery of water. On the other hand, the high molecular weight polymers caused different degrees of flocculation of the ultrafine particles, and their recoveries were much lower than the recovery of water. These observations pointed to a need to re-define flotation depressants in fine particle flotation. The traditional definition of a flotation depressant, i.e., to make particle surfaces hydrophilic by forming a hydrophilic film and/or by removing collector and activator coatings, is sufficient for relatively coarse particles. However, to prevent fine and ultrafine particles from floating, a successful depressant should not only make the particles hydrophilic, but also enlarge the particle sizes so that they do not enter the froth product by mechanical entrainment. Polymeric depressants are ideal for these purposes. The different schemes to use polymeric depressants in the selective flotation of fine and ultrafine particles were discussed These schemes involve the integration of the polymeric depressants into other size enlargement processes such as shear flocculation, oil agglomeration, etc., for hydrophobic particles.

Jan 1, 2004

By L. Bratek, K. Jaworek, M. Czaplicka

Methods for arsenic compound removal from aqueous solutions include processes such as: coagulation, adsorption, membrane techniques, electrochemical and biotechnology techniques. Advanced oxidation using both UV radiation and strong oxidizing agents such as ozone and hydrogen peroxide may also decompose these compounds. It is known that effluents from metallurgical processes contain inorganic arsenic compounds in addition to the organic compounds such as: dimethylarsinic acid and phenylarsonic acid. This paper presents the conditions that lead to the formation of deposits containing mainly arsenic, such as pH, the wavelength of the radiation and the type of oxidant, for this type of effluent.

Jan 1, 2014

By Y. Chengxian, F. Yaorong, Xinzhe. L.

Many factors about the HIC (hydrogen-induced cracking) resistance of pipelines are discussed in this paper. The main factors that influence the ability of HIC are environmental and material factors. The chemical compositions, non-metal inclusions and microstructure are discussed in detail, while a group of tests on HIC resistance are done according to varying C, S, Mn and P contents in pipeline steels, different experiment time and different strength to the coupon. It is concluded that decreasing the amount of C and S can obtain good HIC resistance; the test time has an effect on the different microstructure of X70; microstructure is the most sensitive factor for the initiation processes of HIC.

Jan 1, 2005

By Robert Yobou, Jacques Naho, Benjamin A. Allou, Jacques Carignan, Huan-Zhang Lu, Jayanta Guha, Koffi Pothin

"Résumé - Les seules productions de columbo-tantalite en Côte d'Ivoire sont effectuées dans les éluvions, colluvions et alluvions d'Issia, au Centre-Ouest de la Côte d'Ivoire. Même si un lien direct avec les roches granitiques est suspecté, aucune attention particulière n'a été accordée à l'étude de la minéralisation primaire en relation avec l'évolution de ces granites et des pegmatites associées. Ces granites, qui sont en intrusion dans les roches sédimentaires du Protérozoïque inférieur, comprennent: le granite orienté à deux micas (type Lobo), le granite orienté à muscovite dominante (type Bitapia) et le granite porphyroïde non orienté à muscovite dominante (type Issia). Les résultats de cette étude indiquent que les pegmatites à Nb-Ta-Be-Li sont liées au granite de type Issia. Les observations de terrain et les analyses sur roche totale montrent que: (1) les trois principaux granites de la région sont de type-S et peralumineux dans leur composition, (2) ils ont été formés pendant la période tardi- à post-Éburnéenne, (3) le granite de type Issia fut le dernier à se former.Les pegmatites liées au granite de type Issia ont été classées en quatre types : A- pegmatites stériles; B- pegmatites à Be; C- pegmatites zonées à Nb-Ta-Be; et D- pegmatites zonées à Be-Nb-Ta-Li. Les pegmatites zonées comprennent les zones suivantes: I- zone à aplite; II- zone graphique; III- zone à albite, microcline, béryl et columbo-tantalite; IV- zone à microcline massive; V- zone à quartztourmaline. Ces pegmatites présentent une zone d'altération métasomatique externe.La minéralisation de Ta, Nb, et Be est liée à la zone III des pegmatites de types C et D, la minéralisation de Li est associée aux greisens qui peuvent être observés n'importe où dans les pegmatites de type D. Les données de terrain et de laboratoire indiquent que le granite de type Issia est la roche parentale des pegmatites à éléments rares de la région. Les pegmatites minéralisées sont distribuées seulement autour du granite de type Issia et les patrons des terres rares des granites et ceux des pegmatites à éléments rares sont très similaires. Les analyses de la composition totale montrent un lien génétique entre le granite de type Issia et les pegmatites à éléments rares. Il est suggéré que les pegmatites ont été formées durant le transport et la cristallisation fractionnée du magma. Les éléments rares sont restés dans le liquide résiduel jusqu'à ce que les conditions favorables à leur précipitation soient atteintes.L'établissement de ce lien génétique ouvre des voies pour des nouvelles stratégies d'exploration."

Jan 1, 2005

By C. B. Mapes, E. C. Dowling Jr.

"To reduce concentrate dewatering and drying costs, the Concentrator Division at Phelps Dodge Morenci, Inc. investigated available filtration technologies. Numerous methods were explored, including: drum, disk, belt, pressure, hyperbaric, and ceramic media filtration. An economic evaluation of the individual filtration technologies indicated the advantages of ceramic media filtration for Morenci concentrates. This paper discusses the technological development culminating in the first full scale application of ceramic media disk filters in North America. Low moisture contents are obtained at high production rates and greatly reduced operating costs.INTRODUCTIONPhelps Dodge commissioned the Morenci Concentrator Filter Plant in 1942 with four 8'6"" Dorr-Oliver cloth disk filters. That year, the filter plant processed 265,537 tons of concentrate grading 20.5% Cu. The filter cake production averaged 9.3% moisture. In 1944, the Extension Filter Plant commenced operation with three additional 8'6"" Dorr-Oliver cloth disk filters. This coincided with the expansion of the concentrator. Production that year totaled 451,567 tons of concentrate grading 23.8% Cu. Moisture averaged 9.4%.Through the years additional filter units have been added in response to increased concentrate production. An Eimco drum filter was installed on the extension side and an additional Dorr-Oliver disk filter was installed on the original side in the 1950's. In 1961, two 8'6"" Peterson disk filters were installed, one on each side to replace two worn-out DorrOlivers. The installation of four 10xl2 foot Peterson drum filters was completed in 1974, coinciding with the Metcalf Concentrator startup. An Eimco belt filter was installed later.The greatest change to concentrate dewatering at Morenci occurred in 1963 with the addition of a 10x60 foot rotary gas fired dryer. The installation also included a number of conveyors to deliver filter cake from both plants to and from the dryers. Other ancillary systems included dust scrubbers and their slurry pumps. The commencement of drying was undertaken due to the rapid increase in cake moisture as a result of the LPF process and the recycling of acid plant scrubber dust slurry from the smelter. In 1972, a second dryer system was installed to increase capacity."

Jan 1, 1993

"Option pricing is used in finance for valuing options to buy (or sell) shares at some future date because it provides a convenient framework for quantifying values subject to uncertainty. As one of the main sources of uncertainty in mining is the price (sales) of the metal, this approach can also be used for valuing mining projects.The first part of this paper reviews options and option pricing; the second part presents the approach developed by Brennan and Schwartz (1985) for using option pricing to value natural resources. Several applications of this methodology have been published; these are described. From a mining point of view, the assumptions made by Brennan and Schwartz are too simplistic. The weaknesses are discussed with a view to improving an apparently promising new way of assessing the value of projects. IntroductionThe collapse of the British merchant banking group, Barings, has highlighted the risks that can be incurred by speculators and arbitragers in the futures and options markets. But this negative attention on futures and options should not make us forget their positive aspects. They can provide producers and consumers of metals with more predictable sales prices. The introduction of the new traded average price options, TAPOS, by the London Metal Exchange in January 1997 is a response to this need. Equally important, the theory that the finance industry has developed for valuing options provides an interesting framework for valuing mineral projects as well. While this paper was being revised, the South African gold mining house, JCI, announced that it was using a methodology based on option pricing for valuing the mineral rights to deeplevel gold resources (see Box 1)."

Jan 1, 1997

By X. Cao, A. Birur, R. R. Chromik, J. Cuddy, P. Wanjara, J. Gholipour Baradari, T. Shariff

In this study, 3.1 mm thick Ti-5553 (Ti-5Al-5V-5Mo-3Cr) butt joints were autogenously welded using a 4 kW continuous wave Nd:YAG laser. The effect of welding speed and defocusing distance on the weld quality was investigated in terms of the surface morphology, welding defects, microstructure and hardness. Welds with full penetration were achieved at a defocusing distance ranging from -1 mm to 0 mm and welding speeds from 2.25 to 6.0 m/min. Underfill and porosity were the two main defects most frequently observed but within the optimum process window these defects could be maintained to meet aerospace specification tolerances. The fusion zone (FZ) consisted entirely of retained beta with a refined dendritic morphology. Compared to the bimodal alpha (a) + beta (ß) microstructure of the base metal (BM), the dissolution of the a phase was observed in the heat affected zone (HAZ), which led to an 11 % decrease in hardness from the BM to the FZ. To determine the tensile properties of the welded samples, an automated 3D deformation measurement system was used to measure the local strain in the weld region. The yield strength (YS) and ultimate tensile strength (UTS) increased with increasing welding speed with a highest joint efficiency of 75 % being achieved, albeit with a concomitant reduction in the ductility.

Jan 1, 2010

By S. Downing, T. Grammatikopoulos, N. Hoffmann, C. Gunning

"Most deposits display a high degree of geological and mineralogical complexity that can affect metallurgical processing. Therefore, the proper characterization of the ore and gangue minerals requires a multi disciplinary approach combining geology, mineralogy, geochemistry and processing. However, mineralogy to a large extent informs the metallurgical process. Automated methods can be used throughout the mining chain from advanced exploration through to production.In this presentation we discuss actual case studies where automated mineralogy has been applied in a geometallurgical framework at a pre-feasibility to feasibility level. These include examples from a strongly serpentinized magmatic Ni deposit (Dumont) and a magmatic Cu-Ni deposit (Maturi). Mineral speciation and ratios, e.g., chalcopyrite, cubanite, and pentlandite/pyrrhotite are critical to model the Cu-Ni magmatic deposit. In the serpentinized Ni ore, automated mineralogy is used to speciate the Ni minerals into sulphides, alloys and refractory Ni in the silicate matrix.The mineralogical results are linked to the metallurgical test work in order to model the geometallurgical domains. These case studies will illustrate how mineral quantification and improved understanding of inherent mineralogical parameters in relation to metallurgy reduce technical risk in both exploration and flowsheet development.INTRODUCTIONGeometallurgy is a cross-discipline approach combining geology, metallurgy and mine planning (e.g., Dunham et al., 2011). It is aimed to improve the understanding of geological, mineralogical and metallurgical parameters of an ore. Informational gaps among the different disciplines are often apparent. Automated mineralogy is shown in many studies (e.g., Eppinger et al., 2013, Philander and Rozendaal, 2013) to constitute the link between geology and metallurgy. The geometallurgical approach can provide specific data to geology, mining and mineral processing development and plant operations. The scope of the automated mineralogy is to illustrate how mineral quantification can improve the understanding of inherent mineralogical parameters in relation to metallurgy, and reduce the technical risk in both exploration and flowsheet development."

Jan 1, 2016

By P. A. Riveros, R. Molnar, F. J. Baša

"An acidification circuit was installed and operated at the Agnico-Eagle Silver Division refinery in Cobalt, Ontario, for treating ~300 m3 of a concentrated cyanide waste solution with the purpose of recovering its cyanide and metal values. The acidification circuit was designed from parameters determined experimentally at CANMET. Available refinery equipment was assembled according to a flowsheet developed by Agnico-Eagle Mines. The process produced a regenerated cyanide solution containing >15 g/L of free cyanide, which was used for leaching gold ore at another Agnico- Eagle operation. It was estimated that the value of the recovered cyanide offset the treatment cost. BackgroundThe Silver Division of Agnico-Eagle Mines needed an economic and effective method for disposing of ~300 m3 of a concentrated cyanide waste solution that had remained in the plant after the operation was shut down in 1989. As a result of extensive recycling and evaporation, the solution had become practically saturated with metals, cyanide, thiocyanate, sulphate and other components, and was, therefore, an environmental liability for the company. A partial analysis of the solution is presented in Table 1. Initially, the use of cyanide destruction methods was considered by Agnico-Eagle, but the estimates indicated a considerable cost with no credits to be gained. A research project carried out by CANMET showed that a simple procedure consisting of acidification, filtration and reneutralization was the most attractive option, because it enabled the recovery of a substantial portion of the cyanide. Furthermore, the metals would be recovered in the form of a solid precipitate. The research showed that conventional AVR was not applicable because of excessive cyanide degradation and low HCN volatilization obtained with this particular solution (Riveros et al., 1996). This paper describes the procedure used to treat the concentrated cyanide waste solution and the operating practices of the large-scale acidification circuit run at the Agnico-Eagle refinery."

Jan 1, 1998

By A. G. Pentland

MODELS of mines may be classified under three headings: (a) sheet models, (b) solid models, and (c) skeleton models. Sheet Models are made of sheets of glass, celluloid, or a transparent plastic material. The sheets are mounted in a frame which holds them in a parallel position, either horizontally or vertically. Mine plans are traced on the horizontal sheets; sections on the vertical sheets. The model may be illuminated by electric lights which are separated from the sheets by an opalescent screen. It is viewed from above or from the side in such a way that the plans or sections are superimposed. Sheet models are very useful for the illustration of mines with narrow, steep-dipping veins, but they do not give a satisfactory representation of a large mine with a flat-dipping vein. Large sheets of glass are difficult to handle and to support in a frame.? It is difficult to see through a considerable number of them. Solid Models are made of plaster, concrete, wood, or other material usually in the form of slabs in which the mine workings are indicated by properly dimensioned cavities in the model. The slabs are coloured to show the veins, country rock, faults, etc. The model is divided along selected sections in order to give access to the interior by the temporary removal of parts. Solid models may be used to illustrate large orebodies of the Sullivan type, but they are cumbersome because parts must be removed to study details of structure. Skeleton Models are ones in which the underground cavities are represented by metal, wood, plaster, or wax proportionately shaped and held in place by a frame. They illustrate the work which has been done but do not show the position of the veins, dykes, faults, etc., in the unworked parts. It is necessary to project by eye between workings in order to determine the location of these features. The essential difference between the skeleton model and the solid model is that the skeleton model represents the mine workings by solid forms and does not show the unworked parts of the vein, whereas the solid model shows the vein as a solid and the mine workings as cavities in it. The skeleton model lends itself well to the representation of a large mine with large stopes.

Jan 1, 1944

By R. W. Thompkins

MINE operators are concerned with temperature conditions in their mines, particularly the effects of high temperatures on the l1ealth and efficiency of tl1eir employees. This paper is written to focus attention on the variables of heat transfer between rock and air. It illustrates the difficulties of predicting the manner, and the extent, of heat transfer from theoretical concepts, prior to actual operation of a mine airway. There are ~1any sources of heat in mines. The most important is that of the rock surrounding the airway. This heat, in turn, is a product of the age of the rock, faulting, proximity to recent igneous activity, oxidation of sulphides, hot ground waters, etc. The sources of heat may be constant for any one mine, but they are far from constant when dealing with various mining districts or e1•en with a number of mines in the same district. A second source of heat is that produced by machinery in operation. Practically all the waste

Jan 1, 1962

By L. R. Plitt

A series of experiments were carried out in an effort to develop a universally applicable mathematical model of the hydrocyclone classifier. The design and operating variables studied were: cyclone diameter and height, the inlet, vortex finder and apex diameters, the feed pressure and the solids content of the feed slurry. The model consists of four basic equations which express the cut size ( dso), volumetric split between overflow and underflow, volumetric throughput, and sharpness of separation in terms of the operating and design variables. Although empirical, the model is nevertheless in general agreement with fundamentally derived models. The model clearly 1•eveals the effect of the major variables on the operation of a hydrocyclone. Because of its broad data base and the inclusion of all the major variables, the model may be used without experimental data to predict the operation of cyclones over a wide range of different operating conditions. With operating data, the equations may be modified to serve as an operational model.

Jan 1, 1976

By Martin Landwehr

"Dust samplers are based on different principles. The konimeter is based on the number of particles counted; mining applications are based on routine sampling; and the photometrical evaluation of samples is used after the pre-separation of particles above 5 micron by the mining konimeter. In special cases, the Draeger sampler is used for quantitative analysis. General trends are toward larger samples, concentration on a weight basis, fractionation into size groups by different techniques and an analysis of composition. Standards or TLVs already exist in all industries. Surface industries base their criteria on concentrations and quartz contents in particles below 5 micron. The mining industry uses the tyndalloscope routinely to determine concentrations; concurrent] y, the rock content, as deter-mined by ashing samples, is obtained by konimeter.Threshold limits are related to the rock content in respirable fractions and tyndallometrically determined concentrations. The TL Vs are based empirically on Landwehr's ""dust values,"" as agreed upon with the Mines Inspectorates. Recently, and in accurate sampling, dust samplers have been used that count the dust in two fractions -above and below 5 microns. Mineral composition is determined either for all minerais or just for quartz. In assessing the dust hazard by Landwehr's ""dust values,"" all minerais are taken into consideration; in coal dust sampling, however, only the quartz content is taken into account. Efforts are now being made to co-ordinate the different assessment methods, arriving at uniform MAC values in agreement with those of other countries."

Jan 1, 1969

By Peter R. Drummond

THE paper consists of four sections: (1) a discussion of early work; (2) presentation of the results of a chemical investigation of Falcon-bridge nickel-copper blast-furnace matte; (3) application of the results of this investigation to mattes in general; and ( 4) a summary of conclusions. All general discussion will be confined to the fundamental system of ferrous-cuprous sulphides (FeS-Cu2S). Nickel-, lead-, and zinc-bearing mattes will be treated as minor varieties of the parent system. DISCUSSION OF EARLY INVESTIGATIONS Matte investigations may be divided into three classes: first, those treating the sulphides as alloys-theoretical studies of the system FeS-Cu2S, such as those of Hofman (ll)t or Carpenter and Hayward (2); second, chemical research on mattes made under smelter conditions, such as that carried out by Hawley (3) or Avetision ( 4); third, combinations of the . above, such as the investigations of Gibb and Philp (5) or Fulton and Goodner (6). Much research in the first of these classes, including determinations of . freezing points and of data for structure-composition diagrams of the system FeS-Cu2S, was carried out in the period 1890-1910. LeChatelier and Ziegler (1, 13) proved that FeS, when heated alone above its melting point, dissociated in part, and Friedrich ( quoted by Fulton, 6) showed the same for Cu2S. The reactions may be expressed by the following equations: [xFeS yFe + yS (volatilized)+ (x -y)FeS xCu2S )'Cu+ yS ( vohtilized) + (x -)')Cu,S ] Sulphur is lost by volatilization, leaving a melt of metallic iron plus ferrous sulphide in the one case, and of metallic copper plus cuprous sulphide in the other. If the mixed sulphides are heated far above their melting points, there results either an iron-rich matte containing Fe-FeS-Cu2S or a copper-rich matte containing FeS-Cu2S3-Cu, depending on the relative amounts of each sulphide in the mixture.

Jan 1, 1940

By O. Leuangthong, E. Schnetzler

"The McMurray formation in the Athabasca oil sands deposits of northern Alberta is part of the world’s second largest proven crude oil reserves. The formation is characterized by stratigraphic layers that correspond to three different depositional environments: Marine, Estuarine, and Fluvial facies. Resource estimation for oil sands has traditionally relied on polygonal and inverse distance schemes. These techniques are simple and straightforward in practice, but they do not permit reliable uncertainty assessment. This paper describes the modelling of the McMurray formation using modern geostatistical techniques.Geostatistical modelling should be performed within homogeneous geological facies. The methodology for geostatistical simulation within each of the identified facies involves: 1) assessing the most appropriate stratigraphic transformation for optimization of the correlation structure; 2) determining representative distributions with declustering and debiasing techniques; 3) modelling spatial continuity of the bitumen grade, fines grade, water saturation, and other petrophysical variables; 4) performing estimation and cross validation as checks against simulation results; 5) performing simulation for uncertainty quantification of bitumen and fines grade; and 6) model checking of simulation results against the input data, and comparisons against the kriged models. These steps are described in detail. The application of these models for uncertainty quantification in support of resource classification is also discussed."

Jan 1, 2006

By J. Ambrose, R. W. Zimmerman

"Shales are highly anisotropic in their mechanical behavior. The strength ( ??1) of anisotropic shales depends not only on the magnitude of the other two principal stresses ( ??2, ??3), but also on the bedding plane orientations (?) relative to the principal stresses. In this study, the role of the intermediate stress ( ??2) on the strength of shale is evaluated using new data from triaxial compression and extension tests. To understand the failure behavior of shales, we have carried out triaxial compression tests ( ??1 > ??2 = ??3) on two organic rich mudstones, at different confining stresses and loading angles. We first fit the triaxial compression data with Jaeger’s plane-of-weakness model, and find that the model is able to represent the strength behavior of anisotropic shales reasonably well. We then carried out five triaxial extension tests ( ??1 = ??2 > ??3) for a high strength-anisotropy shale, and two extension tests for a low strength-anisotropy shale. Results from the compression and extension tests for failure along the weak plane shows that the role of ??2 is not significant for weak plane failure. However, for the low strength-anisotropy shale, the failure strength of the intact rock (i.e., at ??= 0o and 90o) for compression and extension tests were significantly different. This indicates that for intact rock failure, the role of ??2 is important and cannot be ignored.INTRODUCTIONFor many years, various researchers have studied the roles of ??2 for failure of isotropic rocks. (Mogi, 1967 and 2007; Colmenares and Zoback, 2002; Al-Ajmi and Zimmerman, 2005 and 2006; Haimson, 2009; Ma and Haimson, 2012). The findings from these studies show that the effect of ??2 on the strength of isotropic rocks is generally significant, and cannot be ignored.Since the role of ??2 in the failure of isotropic rocks was recognized, other researchers attempted to extend some of these isotropic failure criteria to anisotropic rocks, but with limited success (e.g., Tiwari & Rao, 2007; Singh et al., 1998; Zhang and Zhu, 2007; Pei, 2008). Smith and Cheatham (1980), on the other hand, conducted true-triaxial experiments on the Green River Shale and used a J2-I1 type relationship to predict the strength behavior, but without considering the effect of the three-dimensional orientation of the weak plane on strength. Therefore, unlike for the case of isotropic rocks, additional studies need to be done to determine the role of 2 on the failure of anisotropic rocks."

Jan 1, 2015

By E. Brouillette

Difficult operating and mining conditions such as low visibility, difficult roadbeds, fast cycling, small openings, and sharp corners create high demand for LHD manoeuvrability and operator dexterity. Operator experience and patience is especially solicited to fill the bucket rapidly and efficiently and performance can be particularly affected by the skill level of individual operators. Teleoperation and automated loading are viewed as options to improve overall equipment and operation performance in certain mining conditions. Comparative statistical measurements of autoloading performance in different production environments at Noranda demonstrate an increase in bucket filling efficiency and a reduction in filling variance, allowing LHD operation to be more consistent and within manufacturer specifications. Consequential cost savings and productivity increases are demonstrated to be transferable to other mining situations.

May 1, 2003

By James Kear, Romain Prioul, Robert G. Jeffrey, Andrew P. Bunger, Dimitry Chuprakov

"Unconventional gas and geothermal reservoirs are typically naturally fractured and therefore the challenging problem of hydraulic fracture (HF) growth through naturally fractured rocks is an important issue especially for the development of accurate predictive HF models. This paper presents results from laboratory experiments in which HFs have been created in both sandstone and crystalline (gabbronorite) rock specimens such that they impinge either orthogonally or at an oblique angle on an unbonded, machined frictional interface. Depending on the conditions of each experiment, the fractures either cross or are blunted at the interface. The growth behavior was ascertained for these experiments based on a synthesis of the injection pressure record, active ultrasound monitoring, and direct post-experiment inspection of fractured specimens. From these experiments we observe: 1) A contrast between direct crossing and crossing with an offset for orthogonal and oblique intersection, respectively, 2) Apparent independence of crossing/blunting behavior on the friction coefficient for orthogonal intersection, 3) Dependence of the stresses required to promote crossing on the intersection angle between the HF and NF, 4) Existence of cases in which the hydraulic fracture crosses but then essentially ceases propagation such that all fluid is diverted to the interface. INTRODUCTIONHydraulic fracturing is a vital technology used to increase the productivity of oil, gas, and geothermal wells. Predicting hydraulic fracture (HF) growth is, in turn, critical to design of hydraulic fractures that grow to the desired length, accept the desired amount of proppant, and remain contained in the reservoir without unwanted height growth into surrounding layers (e.g. Economides and Nolte, 2000). The importance of HF modeling has prompted 6 decades of research during which simulators have become more efficient, more accurate, and have addressed a growing range of complexities (see review of e.g. Adachi et al., 2007).One of these complexities is the interaction between HFs and mechanical discontinuities such as natural fractures (NFs). Efforts in this area have been mainly driven by development of unconventional (i.e. low permeability) oil and gas resources because essentially all viable low permeability reservoirs, including shale gas/oil reservoirs, are naturally fractured to some degree (King, 2010). One of the most important questions for developing effective HF stimulation strategies in these reservoirs is whether the hydraulic fracture(s) is/are expected to be single-stranded or whether interaction with the NFs will lead to network-like growth. The basic building block for numerical simulators that can address this question (such as Kresse et al., 2013 and Weng et al., 2014) is whether an HF that intersects an NF will cross the NF or whether its growth will be captured by the NF so that additional fluid injection pressurizes the NF but does not generate ongoing growth of a new HF. These scenarios, including subcategories such as crossing with an offset, have been recognized for several decades (Daneshy, 1974; Warpinski and Teufel, 1987, and as recently reviewed and expanded by Chuprakov et al., 2013)."

Jan 1, 2015