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By F. L. Thompson

MAN has been using lubricants of one type or another for at least four thousand years, and probably for a much longer period. We have learned from the inner wall of the tomb of Tehuti-Hetep, on which is a decoration illustrating the method of moving a great stone statue, that as early as 1650 B.C. lubricants were used to facilitate the movement of heavy loads. The Egyptians had available nearly every animal oil and fat, as well as at least thirteen vegetable oils, of our time, all used for food products and in the arts. Examination of the deposit on the axle of a chariot from an Egyptian tomb of 1400 B.C. showed it to consist of animal fat, quartz, sand, iron, and compounds of aluminium and lime-indicating a manufactured lime-soap grease made with lime-soap and possibly tallow. This would not be a bad lubricant for the axles of chariots which had to travel over sandy soil in hot weather. As to the method of grease application, it is remarkable that, from the time wheels were first used in the far distant past up to the present day, no one has ever thought it necessary to design a seal to keep the lubricant in and the dirt out. While time certainly marches on, we have today, in waggons throughout the world, exactly the same form of lubrication as was used in the earliest chariots. From the early days of the chariot until shortly before 1800 A.D. (when the steam engine was introduced), the main heavy equipment required for mining purposes, for machines of war, etc., was made of wood. The bearings were rough, but usually they had metal in the lower half. Light machinery was made of bronze, brass, or iron. Large clearances and poor alignment, plus the fact that speeds were much below present-day demands, combined to provide conditions that were quite satisfactorily met by the lubricants available. These were often produced locally by the machine operator. In northern countries, lard oil, prepared from the fat of hogs, was the universal lubricant employed in machine shop, as a belt and leather dressing, and for cutting operations. Sperm oils were used for light machinery, whereas beef and mutton tallow were more generally employed for the largest bearings. For the early steam cylinders, a slug of heated beef tallow was injected wherever the cylinders gruntingly complained of a lack of lubricant. Southern countries, however, resorted to the use of vegetable oils-olive, cocoanut, etc.

Jan 1, 1940

By J. W. Choung, T. Fu, Z. A. Zhou

An on-line visualization technique and methodology was developed to investigate the role of fine sphalerite (< 10 um) aggregation in flotation. The images of particle aggregates under different operating conditions were recorded and analyzed. The effect of impeller design on particle aggregation was demonstrated. This difference was not mainly due to the energy input into the system, but due to the resultant hydrodynamic conditions created by the impeller and their effect on particle interactions. The recorded image showed that adding fine silica (- 5 um) did not interfere with fine sphalerite aggregation, thereby showing no effect on the sphalerite recovery. Effect of the enlarged aggregate size on increasing flotation recovery was confirmed. Although Malvern Mastersizer produced consistently lower estimates of aggregate size than those by the image analysis, both methods responded to the changes in operating conditions in the similar trend. It was shown from this study that on-line visualization technique is a powerful tool for studying fine particle aggregation and morphology in the context of diagnosis for the flotation separation.

Jan 1, 2004

By W. W. Cummings

The Mineral King Mine, owned and operated by Sheep Creek Mines is located in the Purcell mountain range of southeastern British Columbia. Production of lead and zinc concentrates commenced in 1954 some 60 years after the initial discovery. Low cost mining methods have been employed to extract 16,0C'O tons of ore monthly from large ore bodies formed by replacement in limestone. Extensive areas in the limestone are yet to be explored and success in the search for new ore bodies is anticipated.

Jan 1, 1960

Over five decades ago Kitchener et al. in England and La Mer and Healy in the US were advancing our understanding and application of flocculants, primarily related to water treatment and filtration of sludge. This paper identifies the beneficial uses of flocculants in the mining industry and revisits some less common applications. Flocculants are used in unique ways in the mining industry: (a) to increase the effectiveness of sediment ponds to achieve discharge compliance; (b) to eliminate air emissions and costs associated with concentrate drying; (c) to reduce soil loss by applying a flocculant to erodible soils, and reducing wind and water erosion; (d) to remove/thicken metal precipitates in acid rock drainage treatment; and (e) to enhance clarification and thickening in mineral processing. The mechanism of how flocculants, coagulations and potentially-determining ions function is described and how their use can be controlled and optimized. The potential toxic effects of flocculants and coagulants when used to achieve effluent permit discharge compliance for suspended solids is discussed. A review of numerous best management practice (BMP) guidelines for the design and operation of sediment ponds treating mine site runoff to remove total suspended solids (TSS) and turbidity revealed an absence of a predictive methodology to address regulatory discharge compliance for TSS concentration, turbidity and flocculant-induced toxicity. An essential component of pond design is the need to determine whether flocculants and/or other settling aids are required based on the site-specific soil particle size distributions upslope of the pond. Procedures are provided to predict the need for settling aids and estimate pond discharge quality and downstream impact for TSS, turbidity, toxicity and sub-lethal toxicity. The need to develop BMP guidelines are discussed for (a) the application of flocculant to surface soils to reduce erosion, (b) the application of flocblocks to increase the ?sediment control? aspects of erosion and sediment control, as part of the mine site erosion control plan strategy and (c) the application of flocculant to silt socks to treat mine site runoff.

Aug 1, 2013

By P. C. M. Knops, K. Rijnsburger, R. M. Santos

To overcome the challenges of mineral CO2 sequestration, this work utilizes a unique proprietary Gravity Pressure Vessel (GPV) reactor technology, and focuses on reaction products of high economic value. The GPV provides intense process conditions through hydrostatic pressurization and heat exchange integration that harvests exothermic reaction energy. Here, laboratory-scale tests of the envisioned process was performed in tubular and continuously stirred tank reactor (CSTR) autoclave reactors. The mineral used was Olivine (~Mg1.6Fe2+0.4(SiO4) + ppm Ni/Cr), although asbestos, steel slags and oil shale residues are also under investigation. The effect of several process parameters on reaction extent and product properties was tested: CO2 pressure, temperature, residence time, additives (buffers, lixiviants, chelators, oxidizers), solids loading, and mixing rate. The products (carbonates, amorphous silica and Chromite) were physically separated (based on size, density and magnetic properties), characterized (for chemistry, mineralogy and morphology) and tested in intended applications (e.g. as pozzolanic carbon-negative building material). Economically, it is found that product value is the main driver for mineral carbonation, rather than, or in addition to, the sequestered CO2. The approach of using a GPV and focusing on valuable reaction products could thus make CO2 mineralization a feasible and sustainable hydrometallurgical process.

Jan 1, 2015

By Douglas H. Brown

Cadmium and other &apos;minor&apos; metals in Canada tend to remain inconspicuous given the prominence of the country&apos;s massive production of other minerals. This same reality is reflected in the accuracy and deficiency of quantitative data concerning the sources of supply and demand for these metals. It is the intent of this paper to identify the nature of some of these difficulties and to reconstruct a more accurate description of Canada&apos;s production and consumption of cadmium, based on the results of recent surveys undertaken by the Mineral Policy Sector of Energy, Mines and Resources Canada and Noranda Sales Corporation Ltd.

Jan 1, 1978

By P. R. Goad

"Kidd Creek is a large volcanogenic base metal sulphide deposit, located near the west end of the Abitibi greenstone belt, 27 km north of Timmins, Ontario. The rhyolite geology is characterized by a NNE-striking and steeply east-dipping package of rhyolite volcaniclastics upon which has been imposed a strong ESE-striking and north-dipping structural fabric . Massive rhyolite units with grey-black. chloritic cores and yellow, sericitic margins intrude as dykes into the stratigraphic footwall and as sills higher in the stratigraphy. Massive rhyolite units positioned near the top of the felsic pile exhibit an extensive marginal development of hydraulic fracturing and are termed crackle-brecciated rhyolite.The stringer sulphide zone is positioned in a lobate blanket of crackle-brecciated rhyolite at the top of the felsic pile. The stringer sulphide zone is characterized by a mature chemical alteration, being specifically depleted in alkalis and enriched in iron-rich chlorite. with accompanying silica, sericite and carbonate alteration. A suite of trace elements characterizes this mature alteration. The massive rhyolite units, which intrude lower in the rhyolite volcaniclastics, exhibit a core of weak chlorite alteration and strong marginal sericite alteration. Tight or unfractured massive rhyolite units are essentially devoid of sulphide mineralization and exhibit a suite of trace elements characteristic of this immature alteration. It is interpreted that the massive rhyolite units intruded into an already evolving system and ""choked-off"" active conduits carrying hydrothermal fluids and subsequently acquired an immature alteration signature. Rhyolite units positioned higher in the pile developed intense hydraulic fracturing and a mature alteration coincident with the formation of the stringer sulphide zone. In summary, a model, based strictly upon the rhyolite geology, is reviewed to assist in the exploration for volcanogenic base metal sulphide deposits."

Jan 1, 1985

By Euler De Souza

"Underground operation ventilation energy requirements constitute a significant portion of mine energy consumption (40–50%) and total energy costs (25–40%). In general, mine ventilation systems are energy inefficient; the author has found several systems that operate at efficiencies below 65%. This paper presents how engineering design principles can improve the performance and efficiency of ventilation appliances, resulting in reduced power consumption and operating costs. Case studies demonstrate that, by retrofitting ventilation appliances using proper engineering concepts, systems will operate at efficiencies well above common operating efficiencies, resulting in a drastic reduction in costs and base electrical and energy loads.RÉSUMÉ Les besoins énergétiques nécessaires à l’aérage d’une exploitation souterraine représentent une part considérable de la consommation d’énergie d’une mine (de 40 à 50 %) ainsi que des coûts totaux liés à l’énergie (de 25 à 40 %). De manière générale, les systèmes d’aérage d’une mine sont loin d’être écoénergétiques ; l’auteur a trouvé plusieurs systèmes fonctionnant à des rendements inférieurs à 65 %. Cet article présente les principes de conception technique qui peuvent améliorer la performance et l’efficacité des systèmes d’aérage, entraînant une réduction de la consommation d’électricité et des coûts d’exploitation. Des études de cas montrent qu’en les rénovant à l’aide de concepts techniques adéquats, les systèmes d’aérage fonctionneront à des rendements bien supérieurs aux rendements habituels d’une exploitation. Ces rénovations donneront lieu à une réduction considérable des coûts ainsi que des charges électriques et énergétiques de base.INTRODUCTIONIncreasing electricity supply problems in North America have encouraged an industry-wide evaluation of energy consumption, resulting in a more urgent emphasis on energy-efficient design and operation for all energy-consuming systems. Electricity is the main mode of energy supply and the mining industry is affected by the increasing cost of this commodity (Natural Resources Canada, 2017). Ventilation systems normally operate 24 hours per day, 365 days per year, and account for 25–40% of the total energy costs and 40–50% of the electrical consumption of a mine operation (De Souza, 2013). Ventilation engineers are under ever-increasing pressure to reduce ventilation energy consumption and be cost effective."

Jan 1, 2018

By F. A. McLean

The past decade has witnessed a rapid increase in the number and variety of uses found for internal combustion engines in mining operations. Gasoline engines are now widely used for operating core drills, pumps, compressors, small hoists, switching locomotives, tractors, boats, and other equipment. The heavy-oil engine is employed for operating compressors, generators, shovels, ore-milling machinery, and- in the iron, copper, and coal districts- in connection with that&apos; latest newcomer in modern railroading, the oil-electric locomotive. Each of these applications could well form a subject for a lengthy treatise in itself. This paper, however, will be confined to a discussion of some of the features of internal combustion engines as applied to mine compressing plants and mill drive. Perhaps at no time in the history of mining in Canada has the search for new mines been more vigorously carried on, more old properties rejuvenated, or more remote districts exploited than during the past three years. The mine operator of today has a far wider range of equipment and facilities at his disposal than had the pioneers of Rossland, Cobalt, or Porcupine. Each year now witnesses the hinterland driven farther and farther back as improved forms of transportation, machinery, and methods make possible the exploration of properties once considered too inaccessible to warrant serious attention. Howey, Sherritt-Gordon, Callinan-Flin Flon, Jackson-Manion, Picard Gold Mines, and a number of properties in British Columbia, afford excellent examples of work carried out on an extensive scale miles from a railway, or in comparatively inaccessible mountain regions.

Jan 1, 1928

By MacDonald W. L. F. C. A.

IN accordance with the usual approach to a participation in a panel discussion, this paper is, in some respects, intentionally controversial. I would suggest, how-ever that there is more than a grain of truth in many of the comments made. Before dealing with a particular problem. It is appropriate to set out a few of the more significant objective of an: accounting system: (1) The provision of historical data <•concerning past events, for the information of shareholders, tax authorities, etc. This data can also be used as a tool to predict the future. (2) The provision of a record to safeguard the company's assets and to form the basis of any claim for insurance or other damages. (3) The provision of an accounting framework in making an economic study of a proposed course of future action such as the development of an orebody or the outlay of a substantial sum for new equipment. ( 4) The

Jan 1, 1962

By T. Wajima

"A novel carbonaceous adsorbent for recovery of nickel from nickel plating waste solution was prepared from rice straw using sulfur impregnation. The rice straws were cut to 1 cm pieces, and then immersed in 0.01 - 3 M K2S solution to prepare sulfur-immersed materials. The immersed-materials were heated at 100-700 ºC in nitrogen gas to produce the sulfur-impregnated carbonaceous adsorbent by pyrolysis. The contents of carbon and sulfur in the adsorbent and abilities of adsorbent to recovery nickel from aqueous solution were examined. The contents of carbon and sulfur in sulfur-immersed materials are almost same as those in raw material. In pyrolysis, with increasing the heating temperature to 200 ºC, the contents of carbon and sulfur are almost constant, and then above 300 ºC those increase. The recovery for nickel using raw material, sulfur-immersed material and the product pyrolyzed at 100 - 200 ºC are almost same, and with increasing the heating temperature to 400 ºC, that of the product increases, and above 500 ºC that of the product decreases. In immerse step, with increasing K2S concentration, the carbon content of the product at 400 ºC gradually decreases, the sulfur content of the product increases, and the recovery for nickel using the product gradually increases and then above 1 M K2S decrease. The product prepared from material immersed in 1 M K2S solution at 400 ºC indicates a maximum recovery for nickel ion. The product can adsorb nickel ion in nickel plating waste solution coexisting with phosphate ion, and adsorbed nickel ion in the product was deposited as nickel metal after heating at 1000 ºC under N2 atmosphere.INTRODUCTIONRice is the second world’s largest cereal crop after wheat, but produces large amount of straw residues, of about 330 million metric tonnes. Rice is a widely grown crop in Asia, and rice straw is produced as a by-product of rice production. In most parts of rice fields, open-field burning of rice straw is commonly practiced in the region when there is limited time to prepare a field for the next crop. However, open-field burning of crop residues is an uncontrolled combustion process during which air pollutants are emitted into atmosphere. These air pollutants have significant toxicological properties and are potential carcinogens (Gadede et al., 2009). Although wildfires are prohibited in cultivation fields of most countries, farmers usually keep on burning their crop by-products. Biomass burning is an important source of aerosol particles which may affect local and regional air quality (Gao et al., 2011), and also contribute to global climate changes."

Jan 1, 2016

By C. W. Jr. Waterman

INTRODUCTION MY SUBJECT is one which would require several speakers and many hours of time for adequate presentation in all its many facets. Because of the widely varying market requirements and coal seams mined, the coal industry of the United States bas of necessity employed many types of preparation facilities to satisfy its needs. Predominance of Baum-type jigs, however, bas marked the mechanical cleaning installations since the early thirties, and these machines continue to hold the lead. CLEANING As a matter of record we find that, at the end of 1948, we had 480 mechanical cleaning plants in operation. Of these, 19 used air cleaners only,?400 used water washers only, . and 61 used dry and wet washers in combination . Due to the increased use of spray water underground on cutting and mechanical mining equipment, there has in recent years been a marked downward trend in dry cleaning installations. In fact, the moisture in dry-cleaned fines has been increased to such an extent by spraying that recent dry cleaning installations have incorporated thermal drying ahead of the dry cleaning units in an effort to overcome the varying and increasingly higher moisture percentages in their raw coal feeds. While on the subject of dry cleaning, it might be well to bring to your attention one of our most recent developments in this art. I refer to the McNally-Brusset vacuum jig.

Jan 1, 1951

By P. W. Billwiller

Abstract The Britannia Mining and Smelting Company, Limited, have replaced diamond drills with percussion drills and tungsten: carbide bits for most of their blast hole drilling operations and have thereby reduced ore breaking costs. Two-inch Carset bits .are used, with one-inch hexagonal Atlas Chippewa alloy steel in 3-foot .and 6-foot lengths. Locally made couplings of Atlas SPS 245 alloy steel connect the rods. The machines used are 31½-inch automatic leyners with lugged or anvil block chucks. For drilling holes below the horizontal, the lugged machines with special adapter rods made from 114- inch solid round Atlas SPS 245 are required. These rods are lugged at one end and a water hole is drilled for six inches into the other end. Over this rod is placed a water swivel which permits the water or air to be sent directly into the steel. A decreased cost per foot, increased footage per shift, and the use of standard equipment and crews are some of the main advantages of tungsten carbide drilling over diamond drilling. Introduction Long-hole drilling with percussion drills and sectional steel was introduced in several American mines some twenty-five years ago. It did not prove very successful, however, because the rapid gauge loss in steel bits necessitated the use of very large starter bits. This in turn rapidly fatigued the straight carbon-steel then in use, made it difficult to maintain the couplings, and resulted in a slow drilling rate. The introduction of the tungsten carbide insert bit and alloy drill still has changed this picture and opened real possibilities for the application of percussion drills to blast-hole drilling. If this type of bit had been perfected ten years ago, much of the research work and experimenting done to apply diamond drills to ore breaking would have gone toward developing the application of the tungsten carbide bit to this problem.

Jan 1, 1950

By M. E. Bilir

In this paper, we review cases in which dramatic and visual swelling problems are experienced in underground structures. Swelling rocks have caused many problems in underground engineering projects. They pose severe problems to the design, construction and maintenance of underground openings. If an appropriate integrated design procedure, which proceeds from exploration, tests, analyses and realistic assumptions of swelling behavior, is used during the design stage, the execution of the project can be completed without any serious delays or dramatic design changes. The case histories were subdivided into three classes that include tunnels, underground coal mines and others. For the evaluation of cases, the surrounding rocks, swelling minerals, water inflow, swelling test results and swelling problems were considered. The main purpose of this review is to inform the reader about potential problems with swelling phenomenon and to emphasize the rehabilitation and extensive cost which are encountered due to the lack of necessary integrated design approaches.

Aug 1, 2013

By J. McCreedy

"The addition of Portland cement to hydraulic sand fill has resulted in the production of stable and self-supporting cemented sand fill. The use of cemented fill in the mines of The International Nickel Company has resulted in substantial economies in timber requirements, de-creased dilution of ore and greater flexibility in mining methods.Coupled with special mining techniques, it has permit-ted mining by both cut-and-fill and shrinkage stoping methods to much greater depths than heretofore. The use of cemented sand fill has permitted revisions to undercut-and-fill mining which have significantly improved the efficiency of this method.Automated mixing systems have been developed for preparing cemented sand fill in surface sand plants on a continuous throughput basis. Control of cement-sand mixtures is obtained by the use of a mass flow measuring system and weighing cement feeders."

Jan 1, 1966

By R. L. Alexander

"Madawaska Mines Limited, incorporated in 1975 is the successor to Faraday Uranium Mines Limited. The history of the latter's mine development and corporate changes are outlined. This paper describes the geology of the Bancroft area and the rock types found in the mine, particularly the pegmatite which is the host rock for the uranium. The structure, mineralogy and distribution of the ore shoots are described with the method of grade control and mine development. The paper concludes with a summary of the production and mineral reserves.Location, Access, and PropertyMadawaska Mines Limited is located in Faraday Township, Hastings County, Ontario. The mine is in the N.T.S. quadrant 31 F/ 4, Bancroft sheet and near 46 degrees 01 minute latitude, 77 degrees 46 minutes longitude. The mine is one-half mile north of Highway 28, five miles (8 km) west of Bancroft, and is accessible by various highways from Toronto, Ottawa, Peterborough, and Belleville. (Fig. 1). A landing strip for small aircraft is located at the northwestern edge of Bancroft. Bancroft is a modern community with a population of 2,400. The company has the mineral rights to 2982 acres (1207 hectares) surrounding the mine workings and plant which are situated in the north parts of Lots 16 and 17, Concession XI, Faraday Township."

Jan 1, 1986

By W. de Klerk, M. B. Thorpe

Golden Star Resources Bogoso operates in Ghana’s Western Region. The gold recovery plant includes; a flotation circuit producing a concentrate for the BIOX® process that oxidizes sulphides before a CIL circuit; and a dedicated CIL circuit. BIOX® uses bacteria, therefore water from the BIOX® and CIL plants remained separated; CN water could not be introduced into the flotation / BIOX® circuit. The operation built a process water inventory with high TDS and installed a process water treatment plant (PWTP). Water was released in compliance the permits but containing some thiocyanate. The PWTP brine was returned to the TSF, further exacerbating the TDS. The operation experienced a drought removing the traditional water sources; the team evaluated the options to maintain production - various water streams were laboratory tested provided options for water use. The paper presents the story (treatment chemistry and process chemistry) of continued operations by treating stored water and PWTP discharge water with peroxide; brine usage within the CIL circuit, which increased gold recovery (laboratory testing) and reduced the TDS. Water flows were further modified to include hydraulic tailings re-mining to a CIL circuits. Details of the recovery, basic chemistry and costs savings are provided.

Jan 1, 2014

By G. H. Montgomery

THE PROPERTY of Aunor Gold Mines, Limited, consists of eleven claims, located in Deloro township, approximately three miles southeast of the town of Timmins. Production began in 1940 and currently the mine is operating at a rate of 485 tons per day. GEOLOGY AND MINE DEVELOPMENT The ore zone at Aunor occurs in altered lavas bounded on either side by soft talc-chlorite schist, locally known as &apos;soapstone&apos;. The zone has a strike of N.80°E, dips 60° North, and varies in width from 0 to 250 feet. Within this zone the main orebody has a westerly plunge, away from the No. 1 shaft area (Figure 1). The mine is developed by a vertical three-compartment shaft from surface to the 3,082-foot horizon. Working levels are spaced at 125- foot intervals from the 625-foot to the 1,625-foot horizon, from which to tl1e 2,125-foot level the interval is 250 feet.

Jan 1, 1957

By A. G. Roach

MILLING of Nova Scotia gold ores began in 1862 with arrastras and wooden stamps and has progressed to heavier stamps followed by tables and other forms of concentration for the recovery of the sulphides. Chlorination and cyanide leaching of the concentrates has been practised, and in 1936 the combined amalgamation and all-sliming cyanidation plant of Seal Harbor Gold Mines was built. It has since been found that it is not necessary to cyanide the full tonnage and now only the concentrates are being so treated. From his experience in this enterprise, the writer presents the accompanying flow-sheet and supporting comments. While he has not the temerity to maintain that it is the best or only flow-sheet for Nova Scotia gold ores, he feels that it warrants thoughtful consideration by members of the milling fraternity of the Province. THE ORE The gold in Nova Scotia ores occurs both free and intimately associated with sulphides-chiefly arsenopyrite. Much of the free gold is quite coarse and crystalline. This is especially true when it occurs in white quartz. When in the slate, it is usually in thin plates and scales, frequently coated and discoloured. The values bound up in the sulphides are not amenable to amalgamation and must be recovered by other methods-concentration, followed by smelting or fine grinding and cyanidation. While high freight and treatment charges apply on concentrates shipped from the Province to smelters, a considerable quantity has been so disposed of in the past. However, it is hoped that a customs cyanidation plant will soon become available to producers of these auriferous concentrates in Nova Scotia.

Jan 1, 1938

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