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By Robert B. Parsons

"The customary onslaught of government budgets this spring offers lots of interesting reading to the mining industry.While the favourable changes tend to get all the fanfare, there are some ""sleepers"" in the host of proposed changes which will be bitter pills for some mining people to swallow.IntroductionOn a scale of one to ten, the Canadian mining industry will probably give this year's federal and provincial budgets a score that is pretty close to five. Although some budgetary proposals are generally perceived to be favourable to the industry, there are other provisions (and lack of provisions) which are considered to be negative.This month, Tax Notes examines in a summary manner the principal features of the 1985 federal and provincial budgets which are of particular interest to this country's mineral industry."

Jan 1, 1985

By Farzad Mohammadi, David Kratochvil, Patrick Littlejohn

"With more rigorous regulations being enacted in the mining industry, a need exists for cost effective and environmentally compliant technologies to remove selenium from mine impacted waters to ultra-low concentrations. Existing selenium treatment methods have high life cycle costs, introduce risks of acute fish toxicity, and produce biological waste residues that represent future liabilities. Furthermore, achieving selenium discharge limits of less than 4 ppb is a challenge for existing technologies. Selen-IX™ is a technology developed by BioteQ that selectively removes selenium from mine impacted waters to less than 1 ppb. The technology is purely physico-chemical and takes advantage of the basic principles of ion exchange and electrochemistry. Unlike conventional electrocoagulation that removes suspended solids and breaks emulsions or oxidizes heavy metals, the electrochemical process employed by Selen-IX™ relies on creating conditions where iron acts as a highly effective reducing reagent transforming selenium from a dissolved species into elemental selenium bound in a solid phase. The iron-selenium by-product of Selen-IX™ is an inorganic, non-hazardous and chemically stable solid. Due to their high iron content, the solids produced by Selen-IX™ are of interest to the steel making industry as a low cost feedstock. This offtake potential can not only reduce the life cycle cost of selenium removal by reducing disposal costs but more importantly, eliminate the risk of future environmental liabilities. In this paper, the basics of Selen-IX™ technology are presented along with results of successful piloting on streams from coal and copper-gold deposits.INTRODUCTIONVarious contaminants are released into mining wastewater during the extraction and processing of metals. One such contaminant is selenium. A naturally occurring element found in rocks and minerals, mining activities accelerate its release into the environment. Selenium in trace quantities is essential to all life forms but at higher concentrations it can be harmful, especially to aquatic life where selenium bioaccumulation can lead to reproductive deficiencies."

Jan 1, 2016

By W. B. Boggs

Part 1 Originally, the copper produced at the Noranda ?smelter was shipped in the form of blister bars to the Laurel Hill refinery of the Nichols Copper Co., New York. In 1930 a refinery was built at Montreal East for the purpose of refining Noranda copper and copper from the Hudson Bay Mining and Smelting Co., at Flin Flon. After investigation of the probable costs of making anodes at Noranda and at Montreal, it was decided to make them at Noranda rather than to continue to make blister bars there. Fuel is a major item of expense in making anodes: and since less fuel would be required in making anodes from molten copper than in making them from blister bars, a lower anode furnace cost could be expected at Noranda than at Montreal. Further, the expense connected with making blister bars at Noranda would be eliminated. The cost of treating anode and wire bar furnace slags is a serious item in a refinery, and it was found that the cheapest method would be to ship such slags back to Noranda. With the anode furnace at Noranda, much less anode furnace slag would be made at the refinery. Against these savings which would be effected by making anodes at Noranda must be set the high operating cost of an anode furnace at Montreal, using only tank-room scrap and the Flin Flon copper. This furnace would be handling a comparatively small tonnage and would have a high cost per ton. The usual equipment for making anodes from. liquid copper consists of either a stationary reverberatory furnace or a tilting Tacoma-type furnace together with an anode wheel of the Clark or Walker type. The reverberatory type of furnace has been developed from the furnace used in the old Welsh process of smelting and refining copper, while the tilting furnace is a development of the holding furnace, which is essentially a Peirce Smith converter without tuyeres and provided with burners.

Jan 1, 1932

By D. H. Whiting, A. J. Sinclair

"The San Antonio gold mine, in the Archean Rice Lake Greenstone Belt, was in continuous production from 1932 to 1968, during which period the mine yielded 1.35 million ounces (41 985 kg) of gold and 195,000 ounces (6065 kg) of silver from 4.88 million tons (4.44 Mt) of ore for average grades of 0.28 ounces per ton (9.0 g/t) gold and 0.04 ounces per ton (1.3 g/t) silver. After the 1968 closure, several publications appeared implying that gold grade of ore decreased with increasing depth.Recent observations by the authors show that the relatively low grades in the middle levels of the mine are controlled geologically. However, the reduced average are grade in the lower levels of the mine was due to inadequate mining control that led to a high level of dilution. The similarity of geological factors such as vein styles within structural domains, variations in mining control, recent ore muck sampling results and lithogeo chemical profiles all indicate the similarity of ore in both upper and lower levels.Strict mining control should yield improved grades of gold for future production from the lower levels at San Antonio, in contrast with the production grades of the late 19605that represented extensively diluted ore. High-quality production records are an essential component in re-evaluating a past producer, particularly where workings are accessible. Poorly founded conclusions which cannot be checked by access to workings can have a negative impact on the evaluation procedure."

Jan 1, 1990

By R. A. Payant, J. A. Finch

Under certain conditions of air and moisture, sulphide materials can spontaneously heat, or selfheat. The reaction mechanisms of self-heating are not well understood. Most previous work has involved pyrrhotite because it is the most reactive sulphide. The current work investigates the self-heating behavior of sulphide mixtures composed of sulphides other than pyrrhotite. The four studied sulphides were pyrite, chalcopyrite, sphalerite and galena. The rest-potential was measured for each. Binary mixtures formed as a 1 : 1 weight ratio were pyrite-galena, chalcopyrite-galena, pyrite-chalcopyrite and chalcopyrite-pyrite. The four sulphides and the binary mixtures were subjected to standard self-heating tests. The four individual sulphides did not self-heat. However, mixtures of pyrite-galena and chalcopyrite-galena with rest-potential difference (?E) >0.3 volts did self-heat while the mixtures of pyrite-chalcopyrite and chalcopyritesphalerite with rest-potential differences (?E) = 0.1 volts did not self-heat. The results demonstrate that when certain non self-heating sulphides are combined they can self-heat. A possible explanation based on galvanic interaction and formation of hydrogen sulphide as an intermediate product is discussed.

Jan 1, 2009

Fault detection and identification are major challenges in process engineering and manufacturing and the key component of abnormal event management systems. Timely detection, diagnosis and rectification of abnormal or faulty process conditions can lead to savings of billions of dollars in equipment damage and lost productivity, not to mention the prevention of injury and loss of human life associated with industrial accidents. A major contributing factor to current losses in industry is the reliance on human operators to interpret high-frequency samples from hundreds or thousands of variables simultaneously. As a result, the automation of fault detection and diagnosis is seen as crucial to the successful implementation of abnormal event management, the need for which is becoming all the more urgent given the increased complexity associated with modem industrial plants. In this paper, a methodology for process monitoring that uses support vector methods to extract nonlinear features from data is discussed and applied in the diagnostic monitoring of an industrial liquid-liquid extraction column.

Jan 1, 2005

By D. C. Reid

This paper describes the latest results in research and development currently being undertaken by the CSIRO Mining Technology Group to advance the automation capability of continuous mining equipment in underground coal mining operations. This research delivers enabling technologies that are essential in achieving increased roadway development rates as well as providing a safer working environment for underground mine personnel. Details are presented on technical developments and results of large-scale above-ground experiments conducted under field-realistic conditions. These experiments demonstrate the performance of the ?self-steering? capability which will enable a continuous miner (CM) to automatically maintain a given mining heading and mining horizon under production conditions. A primary technical requirement of this automated functionality is the means to accurately determine both the location and orientation of the CM in real-time. Test results of a high performance navigation system utilising vehicle motion aiding technologies are presented. This system combines high performance inertial sensors, and custom-developed radar to achieve a navigation-grade guidance system. Comprehensive performance evaluation has been conducted using a scale skid-steer mobility platform operating autonomously through a typical roadway development mining pattern with a total path length of 2700 m and mission duration of 112 min. Results from this evaluation demonstrate that the sustained accuracy of the navigation system exceeds the original project expectations and is well suited to the requirements for this underground mining application. There are presently no known alternative methods for providing a practical and accurate three-dimensional guidance solution in this application. This achievement represents a significant milestone in delivering a step change improvement in underground coal mining roadway development.

Aug 1, 2013

By J. L. Collins

"This paper deals with the quantitative analysis of mine maintenance records. Based on a case study of dozer engine records, the author suggests an easy method of deriving useful information for managerial decisions in a step-by-step manner.More specifically, the paper deals with the following topics:• determination of the most economical replacement time,• determination of reliability characteristics,• determination of the number of replacements, and• determination of the number of spares.IntroductionThe mining industry collects a lot of information about every aspect of its activities, an example of which appears in Table I. In Table I , the distribution describes the operating hours at failure of 56 different dozer engines used in severe applications. Besides calculating an average and possibly a standard derivation from the data, little else is derived, at least from a statistical point-of-view.More information can be obtained from these records that could help management in the decision-making process.To illustrate this point, the sample data appearing in Table I will be analyzed in detail by making use of well-known concepts in reliability engineering.Distribution of DataTable I represents a distribution obtained from the recorded hours cumulated from the operators' time cards. The operating hours have been divided into fourteen classes for each 1000 hours of engine running, e.g . all engines scoring an operating time of between 1001 and 2000 hours formed a class , those scoring between 2001 and 3000 hours another one, etc. Generally, the class interval should be a multiple of the equipment preventive maintenance check period.The minimum acceptable sample size should be large enough to ensure that the score in each class interval is at least one. Ideally, the score for each class interval should be at least five so that a chi-square test could be carried out if necessary.The average life of an engine can be found by adding the products of the frequency and the class mark (mid-point) values. Therefore:"

Jan 1, 1987

By A. G. Roach

IT IS generally stated that the gold ores of Nova Scotia are free-milling, and for the most part this is true. However, there is a certain proportion of the gold finely disseminated throughout the sulphides, notably arsenopyrite, and this gold is definitely not recoverable as 'free-milling' gold by amalgamation. The proportion of free-milling gold to total gold seems to vary widely in different localities in the Province and is lowest in deposits of the fissure-vein type. The problem of recovery of these relatively recalcitrant values is usually one of economics, in some plac.es a simple gravity concentrate being of such low tenor that its extraction and subsequent disposal will not bear the costs involved. In other cases, such a high percentage of values escapes from the mortars and plates that concentration is definitely indicated. The size of the mining operation is also an important factor. In the large majority of cases, however, some concentrating step is warranted, even if the resulting concentrate is stock-piled until sufficient has accumulated to justify further treatment.

Jan 1, 1940

By D. Mraz

"In certain instances, rocks around underground excavations behave as a plastic mass. This paper offers several solutions to predicting the mode of plastic flow around cavities and designing mining pillars where plastic conditions exist.IntroductionWhen stresses around underground cavities exceed yield limits of the host rock, the material often behaves as a plastic mass. The best example of this phenomenon is the behaviour of salt rocks in deep salt and potash deposits (more than 500 m deep).However, many other soft rocks exhibit similar properties. For example, Jeremic(1) described certain types of coal yielding plastically under high pressure. Alder suggested that granulated rock behaves plastically.The object of this paper is to propose a de sign procedure for mining pillars exhibiting plastic flow due to the combination of rock properties and in-situ stresses.Prandtl(3) mathematically defined a concept of a generalized, perfectly plastic substance, not possessing the property of strain hardening (Fig. I). He had in mind, a solid with a quasi quasi-isotropic , polycrystalline structure having a well defined yield point, and he postulated that its material elements start and continue to deform plastically when the maximum shearing stress ""'MAX"" reaches a sharp limit, dependent on the mean value of the sum of the major and minor principal stresses:"

Jan 1, 1984

By B. Das

"Computers have been used extensively in the mineral industry in exploration, reserves calculation, mining technology, mineral processing, etc. With respect to coal mining, there are also various applications for evaluating rock slope stability of open pits, design of open pits, underground operations, mine ventilation, ground control, data processing and management information, operations control and certain technological applications. Mine ventilation appears to be the field in underground coal mining touched on most; on the other hand, underground coal mining methods evaluation is represented only sparingly.It is therefore essential to review the status of the computer in underground coal mining methods evaluation in order to define its scope for further application. The paper discusses the roles of the mining engineer, programmer, computer operator and analyst as well as that of the computer. The important parameters will be identified and discussed along with their application for different underground coal mining methods, with their individual unit processes. Mainly, longwall face operations have been covered. Although many models have been of academic interest, they can be considered as important steps in a transition stage which will be followed by more practical applications for computers for underground coal mining method evaluations in the future. This calls for a coordinated effort from all concerned."

Jan 1, 1981

By G. R. Guillet

"Bricks made from local Paleozoic shales, and floor and wall tiles made from imported clays, both established record production volumes in 1985 and are the strongest segments of Ontario 's clay products industries. However, renewed interest in traditional materials also supports a good market for clay flower pots and flu e liners, and innovative processing studies are showing promise for possible new production of clay roofing tiles. This paper reviews the highlights of a comprehensive study of Ontario's clay products industries, completed in 1986. IntroductionFor some years now, Ontario' s clay products industries have been unspectacular in their attempt to cope with the recent recession and the impact of alternative materials. But a strong demand for bricks in recent years has done much to dispel the gloom.Bricks, drainage tiles, sewer pipes, flue liners, structural and partition tiles, and flower pots have been commonly referred to as ""heavy"" clay products, and they have been based largely on local clays and shales. To this list might be added expanded aggregate and mineral wool. Clay refractories, sanitary ware, electrical porcelain , art pottery, and floor and wall tiles are not considered heavy clay products, and are commonly made from a variety of ceramic materials, many of which are imported.Production facilities for heavy clay products often began in Ontario as small family enterprises, using whatever clay was available locally to supply the local market with building bricks and other clay products needed for construction. Improved road systems increased the market range for these plant s, and new technology and industry standards resulted in gradual"

Jan 1, 1988

By R. F. Engler

"IntroductionThe Coal Branch region of west-central Alberta has been the focal point for unprecedented exploration and development activities over the past ten years prompted by the renewed markets for high-quality thermal coal. Although mines were developed and operated extensively throughout the region from 1910 until 1960, information relating to the detailed stratigraphy of the coal measures and their areal distribution tended to be localized to individual mine sites. Continuity along trend was impaired by a paucity of outcrop restricting geologic mapping to stream bank and roadside exposures. Recent studies and subsequent publications by Jerzykiewicz and McLean of the Geological Survey of Canada (1978, 1980) have established a detailed sedimentological model and defined the stratigraphic nomenclature for the region . The term Coalspur Beds has been adopted to describe the coal-bearing sequence between the overlying Paskapoo Formation and underlying Brazeau Formation. Complete sections of the Coalspur Beds have been compiled from sub-surface borehole data and published by Manalta Coal Ltd ., Dentherm Resources Ltd. and Luscar Stereo Ltd. This paper is an attempt to correlate this information on a regional basis to illustrate trends within the Coalspur Beds."

Jan 1, 1986

By G. R. Guillet

"Bricks made from local Paleozoic shales, and floor and wall tiles made from imported clays, both established record production volumes in 1985 and are the strongest segments of Ontario's clay products industries. However, renewed interest in traditional materials also supports a good market for clay flower pots and flu e liners, and innovative processing studies are showing promise for possible new production of clay roofing tiles. This paper reviews the highlights of a comprehensive study of Ontario's clay products industries, completed in 1986. IntroductionFor some years now, Ontario's clay products industries have been unspectacular in their attempt to cope with the recent recession and the impact of alternative materials. But a strong demand for bricks in recent years has done much to dispel the gloom. Bricks, drainage tiles, sewer pipes, flue liners, structural and partition tiles, and flower pots have been commonly referred to as ""heavy"" clay products, and they have been based largely on local clays and shales. To this list might be added expanded aggregate and mineral wool. Clay refractories, sanitary ware, electrical porcelain, art pottery, and floor and wall tiles are not considered heavy clay products, and are commonly made from a variety of ceramic materials, many of which are imported.Production facilities for heavy clay products often began in Ontario as small family enterprises, using whatever clay was available locally to supply the local market with building bricks and other clay products needed for construction. Improved road systems increased the market range for these plant s, and new technology and industry standards resulted in gradual upgrading and consolidation of them as traced in Table I"

Jan 1, 1988

By R. R. Stone

"This paper will examine the role of debt and equity in project financing and will illustrate the impact on the return to the project sponsor of each type. Conventional debt sources will be examined, as will product purchaser advances, foreign export-import bank loans and lease financing. The paper will review guarantees, charges against the project, dividend restrictions and other commitments. It will also discuss various features of sales contracts and the degree to which they can assist in securing financing. IntroductionThe cost of bringing new mining projects on stream is escalating significantly more rapidly than general rates of inflation. Reasons for this include the higher costs of safeguarding the environment and ensuring the health and safety of workers. The need to develop properties in more remote areas is also a significant factor. These higher costs have not been matched by increases in metal prices, making the task of financing these projects ever more difficult. At the same time, the imagination of borrowers and lenders seems boundless, and innovative schemes for financing projects are constantly being unveiled.It is probably safe to say that no two projects have ever been financed in precisely the same way and the number of financing options for any project is limited only by the imagination of the sponsors themselves. The objectives of the project sponsor represent the most important factor in determining the scope of possible financial arrangements. For example, the sponsor may wish to maximize over-all company leverage by isolating each of its projects in separate companies. In so doing, it hopes to facilitate more ventures than would otherwise be the case. These objectives point toward true project financing. Additional objectives may be to develop a number of its properties by joint venture and to reduce the amount of debt on the sponsor's balance sheet. Those sponsors whose objectives include minimizing over-all financing costs will wish to increase the number of financial options and, as a result, will not be so concerned with effecting true project financing. This approach may also provide ""greater certainty that tax benefits are utilized quickly."

Jan 1, 1980

By R. K. Singhal

"On the mining side the Canadian oil sands industry has become proficient in excavation and disposal of ore and overburden. Nearly twenty years of mining experience is now behind this industry. While local improvements to existing mining systems and practices will continue, it is believed that some further gains in productivity can be achieved by selectively introducing new ideas from other mining and non-mining industries. This type of technology transfer is vital for over-all cost-effective technology enhancement of oil sands mining operations.Discussed in this paper are the issues of mining equipment, equipment sizing, microprocessor and computer based technol¬ogy as applied to mine-wide data management, automation and remote control and a projection of likely mining systems in the year 2000!This paper reviews the ""state-of-the-art"" in selected surface mining systems and attempts to evaluate the forthcoming technology and its application."

Jan 1, 1989

By Wenbin Zhang, George W. Poling

"Prior or simultaneous addition of ammonium sulphate can, not only enhance the activating effect of hydrosulphide ions on xanthate flotation of malachite but it can also eliminate possible detrimental or depressing effects of excess residual hydrosulphide . Use of relatively inexpensive ammonium sulphate appears to reduce the consumption of the much more expensive sulphidizing agent for optimal flotation recovery INTRODUCTIONOxidized copper minerals float poorly with conventional thiol-type collectors. This is believed to be due to the nonadherent character of the collector coating, which is readily re- moved by particle abrasion. Rosas and Polingr reported emulsion flotation seemed capable of resisting abrasion during the flotation of non-sulphide copper ores. It appears that the most common flotation technique for oxidized copper minerals comprises sulphidization with Na .S and subsequent treatment by sulphydryl collector. The principles of this method are available . Malghan recently reviewed the studies on the role of sodium sulphide in the flotation of oxidized copper, lead and zinc minerals.It is well known that in the sulphidized flotation of malachite, the activation process depends strongly on the concentration of the sulphidizing agent, i.e., insufficient sulphide gives poor recoveries because of inadequate sulphidization; excessive sulphide also causes poor recoveries due to the depressive effect of the residual hydro-sulphide ions in solution. A major difficulty in sulphidization, especially with a varying feed nature, is to establish and maintain the optimum sulphide concentration in solution. In plant practice, vigorous control of sodium sulphide is required and stepwise addition of the reagent is recommended to improve the efficiency of the process. Soto and Laskowskim have found that malachite, depressed by an excess of sulphide ions, can restore its floatability if air or oxygen is introduced to the pulp. They attributed this to the oxidation of the HS - ions on the surface of the mineral. Jones and Woodcockuvi showed that a sulphide ion selective electrode could be used to optimize the conditions (e.g . amount of hydrosulphide, sulphidization time, flotation time) more readily and precisely than existing methods in the flotation of oxidized copper ores."

Jan 1, 1989

By P. K. Kaiser, F. Amann

"Rock mass characterization for deep underground construction and mining offers many challenges. This paper first describes some of the key challenges when characterizing highly stressed brittle rocks and then offers some guidance on how to arrive at reliable rock mass strength parameters for deep mining applications. Focus is placed on characterization for rock mass strength determination. It is illustrated how the common use of currently available rock mass characterization systems tend to underestimate the strength of rock at depth. Modifications to currently adopted approaches, i.e., the use of Geological Strength Index GSI for rock mass strength determination, are presented.INTRODUCTIONFor green fields projects, the first challenge of rock mass characterization stems from a lack of access to examine the rock mass at scales larger than typical core sizes (i.e., ~63mm in diameter) until late in the mine design when the flexibility for making changes is constrained. Hence, rock mass characterization often has to rely on information derived from boreholes alone (e.g., core, logs, etc.). This challenge is lessened when mines are expanded from existing operations. A second challenge is related to changing rock mass behaviour with increasing depth and stress. At depth, the rock is highly stressed, thus closer to failure, and often highly confined which leads to a higher interlocking with elevated strength but more brittleness. The goals of rock mass characterization are to be tailored to the technical goals of an investigation. For example, for cave engineering, the workflow includes the assessment of five key engineering aspects (Brown, 2007): Caveability; fragmentation; cave performance; extraction level stability; and mine construction (rock support). Each engineering aspect has to address specific engineering questions and each design component is influenced by different rock mass behaviour aspects and thus is dominated by different rock mass properties, e.g., the vulnerability to stress fracturing (spalling), the bulking characteristics for flow control and support selection, and the confining stress impact on pillar or support design. An effective rock mass characterization program, including logging, mapping and laboratory testing, thus has to collect and interpret features that are relevant for the above listed purposes. Some of the predominant factors are: block volume of defected and non-defected rock; spalling strength; tensile strength of defects; rock mass modulus; and rock mass strength parameters for application to low and high confinement design aspects."

Jan 1, 2015

By S. K. Paul

"This paper briefly describes the underground crushing and conveying system at Sherritt Gordon Mines' Ruttan Mine. A series of three steel-cord belted conveyors, with a total length of 2J55 metres and a total vertical lift of 407 metres, convey the muck from the underground crushing station to the mill at the surface. The maximum size of the crushed rock is 6 in. All the conveyors are provided with numerous safety and fire suppression devices. IntroductionThe Ruttan Mine of Sherritt Gordon Mines Limited is located 20 km east of the town of Leaf Rapids, 760 km north of Winnipeg. The orebody is multilensed, with lens width varying from 6 to 45 m. Ore production started in 1973 with the opening of a 10,000-tpd open-pit mine. Initial development of the underground mine was started in 1972 with the driving of parallel conveyor and access declines at minus-2507o gradient to the I 220-m level, and then the access ramp was further extended to the 1160-m level. Exploration drifting was done on the 1280-m and 1160-m levels from the access ramp. The final development plan for the underground project was approved in January 1977, and full-scale development and constructionwere resumed.At present, Ruttan Mine is in a period of transition from open-pit to underground mining. Ore production is now coming from both operations. By mid-1980, open-pit production will cease and all production will come from the undergroundmine.The underground mining method at the Ruttan Mine is sublevel open stoping with delayed backfilling. The orebody is divided along strike into a series of 27-m-long stopes and 15-m pillars, both 60 m high."

Jan 1, 1980

By C. Gravel, A. Fathi, P. Rivard, G. Ballivy, Z. Moradian, M. Quirion

Numerous schemes have been proposed in the past to evaluate the shear strength of rock discontinuities based on in situ and laboratory testing. Due to scale effects, in situ testing is the most reliable way to assess the shear strength parameters. However, practical reasons often impede this kind of testing. This is unfortunate because advances in theoretical rock mechanics are still dependant on qualitative experimental works. This paper presents a mobile high capacity shear apparatus developed for in situ direct shear testing of discontinuities along with testing methodology. The apparatus has the advantage of being simple, although of high capacity, and can be moved to different site locations for other tests. The in situ test was performed on a natural rock outcrop of schist with subvertical schistosity. A concrete block 50 x 50 cm with a base layer of high strength mortar was cast on the rock surface. Prior to the test, the concrete block was lifted and repositioned to have an unbonded joint but with interlocking asperities. The shear load was applied perpendicularly to the schistosity direction. The test was conducted in a constant normal load (CNL) condition. Both normal and shear loads were applied manually. The instrumentation consisted of two load cells for shear and normal loading, eight displacement laser extensometers for shear, normal, and lateral displacements and fourteen acoustic emission sensors for monitoring evolution of asperities’ degradation during the test. The friction angle obtained is 72° for the peak and 58° for the residual. The high values of friction angle indicates that first-order roughness and good interlocking of the joint surfaces can result in high shear strength parameter values in a rock generally regarded to have low values.

Jan 1, 2015