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By E. G. Kelly

Because of the nature of the breakage in the Barmac vertical spindle impactor, the 80% reduction ratio is very small, so that when the energy efficiency is calculated by Bond's method, it appears to be very low. However, the product size distribution contains a high proportion of fines. It is argued that the production of these fines accounts for the high energy consumption, and Bond's method is modified to account for this, by considering the crusher to be, effectively, a number of smaller crushers in parallel, each having a different reduction ratio.

Jan 1, 1988

By T. J. Close

On September 10, 1991, Secretary of the Department of Interior Manuel Lujan deleted the Silver Peak Range North Wilderness Study Area from the list of U.S. Bureau of Land Management lands in Nevada to be considered for wilderness designation. This decision was based in part on the U.S. Bureau of Mines mineral investigation of the wilderness study area which found that it has indications of precious metals resources. The following is a summary of the results of that mineral investigation. The study area lies between the Silver Peak and Dyer mining districts of west-central Nevada. The Silver Peak mining district, to the east, has a long mining history dating back to 1907 when precious-metals-bearing veins were discovered. The major producer in the Silver Peak district was Sunshine Mining Company's Sixteen-to-One silver mine. During the Bureau's study the Sixteen-to-One mine was operating; it has since been idled due to low silver prices. Precious metals-bearing veins were discovered in the Dyer district, to the west of the study area, in the 1860's. Mineral activity in Dyer district consisted mainly of prospecting. The Silver Peak study area itself has no mining history and contains only a few mining claims, but the Bureau examined 13 mineralized sites, most previously unknown and unclaimed. These sites are along two zones that cross the study area from the Silver Peak to the Dyer mining district. The two zones transect a volcanic center of fractured and altered rocks that contain epithermal veins of quartz, calcite, and jasperoid with gold, silver, and base metals. At the surface these veins are poorly defined and poorly mineralized. The more than forty veins examined in the study area are as thick as 17 feet and as long as 1,000 feet. Samples from surface exposures of these veins contained as much as 0.02 ounce per ton gold, 2.1 ounces per ton silver, 1.0 percent copper, 2.6 percent lead, and 0.4 percent zinc. Analyses of the Bureau data disclosed no vein large enough or of high enough grade to be classified a mineral resource. However, most do have indications of silver-and gold-bearing resources at depth. Subsurface exploration had to be done on the vein at the Sixteen-to-One mine to outline reserves (a vein averaging about 22 feet thick and containing 6-to 7-ounces per ton silver); the same is true of veins in the Silver Peak Range North Wilderness Study Area.

Jan 1, 1993

By J. R. Palmes

Three coal samples, selected out of eight with well characterized surface properties, were used in flocculation tests and synthetic mixture of coal and silica was used in the selective flocculation experiments. Coal wettability and flocculant type were found to have a strong effect on the flocculation results.

Jan 1, 1993

By Qingwen Shi, Yun Zhao, Brijes Mishra

The effect of discontinuities on the fracturing and mechanical behavior of shale has been extensively investigated on a laboratory scale in previous works. It is well agreed that the lamination properties, including discontinuity and lamina properties, affect the behavior of shale. However, it is still unclear how the lamination properties are affecting the stability of the shale roof in an underground coal mine entry. This paper investigated the effect of lamination properties using the discrete element method on a mine-scale entry model as an extension to the previous work conducted on laboratory scale models.

Jan 11, 2022

One of the most important parameters in mine ventilation planning is the friction factor (K). Accurate values of friction factors are critical especially when carrying out mine ventilation simulations. No computer simulation of a mine ventilation network is meaningful if the airway resistances are not accurately estimated (when planning a new mine) or measured (for an existing mine). However, in the first case not many reliable values of friction factors exist in the international literature. This paper presents the results of a research project carried out in the province of Quebec where ventilation friction factors were measured in all underground metal mines. These friction factors are statistically analyzed and tabulated. A friction factor database was created that also includes the friction factors measured in the past by other people. This database can help the mine engineer to accurately estimate ventilation friction factors according to the specific conditions. This database offers several values of friction factors typical for hard rock mine conditions typical of modern underground metal mines.

Jan 1, 2009

By Richard L. Bullock

Believe it or not, mine evaluation and feasibility studies are as old as the industry itself. In the first recorded writing on mining by Agricola (1556), he gave several clues as what to look for in evaluating a mine, to determine if it was economically feasible. Below is the guidance from Agricola, with my interpretation of what he would include today. Now a miner, before he begins to mine the orebodies must consider seven things, namely: ? The situation (the geography/topography). ? The conditions (the geologic/mineralogic and mining conditions). ? The water (availability, hydrology and ownership). ? The roads (plus the railroads, power lines, all other infrastructure). ? The climate (the weather-rainfall/environment). ? The right of ownership (the land and legal entitlement). ? The neighbors (the social environmental concerns of the area). It is amazing how much of his guidance has not changed in 455 years. Yet Agricola gives no guidance on determining the correct cost, or determining the correct commodity pricing. But he does give a few words of caution on the related ethics involved on buying mineral properties: ?A prudent owner, before he buys shares, ought to go to the mine and carefully examine the nature of the vein, for it is very important that he should be on his guard lest fraudulent sellers of shares should deceive him.? Three hundred years later (1866), to further amplify this point, in the most famous thing that Mark Twain never said, as an introduction to a lecturer to an audience of gold-miners at Red Dog, CA, the famed author/humorist allegedly described a mine as ?a hole in the ground owned by a liar? (Farrar & Rinehart, 1935). So, one might conclude that between these two dates, the mining industry did little to improve its reputation. Unfortunately, since Mark Twain allegedly made those remarks, we have not done near enough to gain accountability for the mineral industry.

Jan 1, 2011

By C. A. Oestreicher

For sulfide minerals, the presence of dissolved oxygen in the water phase is an influencing factor for separation by flotation. Klassen and Mokrousov(I:217l distinguish three stages of oxygen adsorption; namely, reversible adsorption, activated adsorption and, finally, surface oxidation. While contraversial, limited adsorption of oxygen is believed to improve the interfacial reactivity between collector and mineral. Intensive surface oxidation of sulfide minerals usually results in unsatisfactory flotation with collectors of the xanthate type. The influence of dissolved oxygen in the water phase has received consideration for sphalerite, galena, chalcopyrite, arsenopyrite, chalcocite, and covellite(2,3,4,5,6). However, the nature of surface oxidation products of sulfide minerals has received very limited investigation(6,7). Lightly oxidized galena promotes the adsorptive reaction of surfactant (xanthate or dixanthogen). Tolun and Kitchener(8) state that limited interaction occurs between galena and xanthate under relatively reducing conditions. And, that exposure to oxygen raises the electrochemical potential of the galena to that required for reaction with xanthate or dixanthogen. In the latter condition, the galena has an "effective flotation surface". On the other hand, intensive oxidation of galena reduces the chemical reaction with xanthate collectors (9) . Complete flotation with xanthate-type surfactants with increasing oxygen content in the water phase has been determined to have the following sulfide mineral sequence(3): galena, pyrite, sphalerite, chalcopyrite, pyrrhotite and arseno-pyrite. The work of Cusack(4) suggests that some threshold amount of oxygen is necessary for flotation to occur, but heavy oxidation hinders flotation with xanthates. According to Tolun and Kitchener(8) catalytic oxidation of xanthate to dixanthogen occurs. From infrared studies, Poling and Leja(IO,II) found that in the absence of oxygen in solution, xanthate ions do not adsorb either on

Jan 1, 1972

By Kwangmin Kim, Junnhyeok Park, Taehee Lee, Minkyu Kim

Mine tailings storage facilities (TSFs) can be a significant source of fine, respirable dust. This dust poses concerns, especially for nearby communities, because of its detrimental impact on respiratory health. To address these concerns, this study examined the effectiveness of commercially available polymers, known for their biocompatible and environmentally friendly features, to prevent dust generation from upstream-type TSFs in active mining operations. It focused on two areas in TSFs: the tailings beach and slope/dike surfaces. Two types of polymers—polyethylene glycol and poloxamer—were selected, and their effectiveness was evaluated in a series of phased laboratory and field tests. The lab tests investigated the moisture-retention capacity of the tailings after treatment with the polymer solutions as well as the ability of these solutions to reduce dust emissions. Polymers were applied to a tailings bed surface in the lab and dust was generated from this surface using a wind tunnel. PM10 and PM2.5 concentrations were measured using laser-diffraction dust sensors, and the polymers were found to have reduced dust emissions up to 95%. Small-scale wind-blowing tests were conducted in the field (specifically, in a controlled environment at a TSF) to evaluate polymer effectiveness on the tailings beach and slope/dike areas. The tests revealed that the AP could efficiently suppress approximately 80% of PM10 and PM2.5 dust emissions at both types of areas. Finally, 1000 gallons of AP solution were discharged at the top of tailings beach and slope/dike areas, respectively, and found to be effective. The results of these tests showed the high potential of the biocompatible polymers to be a feasible solution for reducing the respirable dust emissions from upstream TSFs in arid and semi-arid regions.

By Gilbert Sauriol

The mining complex, which the Mines Gaspé division of Noranda Mines Limited has operated in Murdochville since 1954, includes open pit and underground mines, two mills, one leaching plant and a smelter. The under- ground mining uses predominantly a large scale room and pillar method, rooms 15 m wide, 30 m high and 300 m long being common. Ore production is effected by 4.5 m3 front-end loaders and 32-tonne trucks powered respectively by 225 and 325 kW diesels. Daily dust and gas readings show that air quality can be maintained at an acceptable level with much less ventilation than that normally specified. This paper emphasizes the point that air requirements should be based on Air Quality Standards, thus allowing an operation to benefit from favourable conditions or from improvements such as exhaust treatment, fuel alteration, etc.

Jan 1, 1983

By Adil Jamali, Taufiq Hidayat, Imam Santoso, Zulfiadi Zulhan, Indah Suryani

The study investigates the segregation of iron and titanium in iron sand concentrate pellets reduced using coal under an isothermal-temperature gradient profile. The results show that metallic iron migrates to the surface while titanium and other oxides move to the center of the pellet. The study provides insights into the reduction process and the behavior of iron and titanium during heat treatment.

Mar 2, 2022

By H. M. Park

Risk is a major factor in all mining activities, arising from many internal and external variables. The authors? research has resulted in a systematic method for the quantification of risk in mining projects (Park, 2012), and this research is being presented in a series of papers. The first paper (Park and Nelson, 2013a) identified the variables associated with risk in mining projects, and their effects and was published in the October issue of Mining Engineering magazine. The second (Park and Nelson, 2013b) discussed methods of assessing the overall risk associated with those variables (published at www.me.smenet.org), and presented a statistical model based on a survey of 31 experts. This paper will present an evaluation of the statistical model, using data from previous mining investment decisions in which the authors have been involved.

Oct 1, 2013

By M. J. Sapko

The design requirements for mine ventilation seals have undergone a radical transformation in recent years, and these revisions have greatly increased the cost of the seal designs and their construction. For example, in the past two years, new federal regulations have increased the minimum design requirement to withstand explosion pressures from 138 kPa (20 psig) to 345 kPa (50 psig) or 827 kPa (120 psig), depending on whether the sealed mine volume is monitored continuously or not. Moreover, there is still a possibility that under certain conditions (such as detonations) even higher pressure requirements may be necessary. The ability of a monolithic, stand-alone mine seal to reliably withstand the full range of current and future pressures is becoming increasingly difficult and expensive. In an effort to develop a practical alternative, the West Virginia Office of Miners? Health Safety and Training (WVOMHST) and the National Institute for Occupational Safety and Health (NIOSH) have collaborated in a research effort to develop a practical, economic, and safe mine sealing technique that can enable mines seals to meet the full range of new explosion pressure design requirements. The basic idea is to use a barrier of common mine gob and rubble in combination with a conventional mine seal so that the pressure resulting from a gas explosion is reflected, absorbed, and attenuated, so the pressure on the ventilation seal is reduced. This paper discusses some concepts and preliminary test results for a ?Passive Mine Blast Attenuator? (PMBA) that can provide a useful alternative to increasingly larger and stronger stand-alone mine seals. Numerical models and full-scale experiments conducted at the NIOSH Lake Lynn Laboratory Experimental Mine (LLEM) show that the use of a PMBA can signficantly reduce the blast pressure and impulse on conventional ventilation seals. DISCLAIMER: This information is distributed solely for the purpose of pre-dissemination peer review under applicable information quality guidelines. It has not been formally disseminated by the National Institute for Occupational Safety and Health (NIOSH). It does not represent and should not be construed to represent any agency determination or policy.

Jan 1, 2009

By Malcolm T. Wane

The subject matter of this paper, "Applied Rock Mechanics?," has its genesis in a recent field trip taken by the author. A more or less standard question asked at the mines visited was "How are you using the principles of Rock Mechanics to assist you in maintaining an efficient, safe, and competitive mining operation?" The question was couched in a number of different forms, but the intent was to determine whether or not a general theory based on reason and the scientific method was applied or whether the alternatives of tradition, intuition, ?common sense', revelation, ?shotgun methods' or authoritarianism were invoked. Perhaps two responses to this query will be illustrative of the general nature of the replies. At operation XYZ an extension to the known ore body has been found. The extension is of large enough size and grade that a mining scheme using load-haul-damp techniques is envisaged. Since this represents a departure from the present mining scheme, questions have arisen regarding pillar sizes, room and entry sizes and possible support requirements. A task force has been set up to expeditiously plan for these things and write the necessary specifications and requirements. The fundamental question was posed to members of this group.

Jan 1, 1971

By Staff

Minerals contribute to U.S. gross domestic product (GDP) at several levels ? from mining and processing to the manufacturing of Anished products. In 2009, the estimated real GDP of the United States decreased by 2.4 percent compared with, and the estimated nominal GDP was about $14.2 trillion (Table 1). Trends in various sectors of the domestic economy are often reflected in mineral production and consumption rates. In 2009, the continued decline of the housing market was reflected in reductions in the production and consumption of cement, clays, construction sand and gravel, and crushed stone (those mineral commodities that are used almost exclusively in construction). Production of mineral commodities associated with the manufacture of goods for the housing market, such as ceramic tile, heating and air conditioning equipment, paint, plumbing and sanitaryware, roofing, wiring and wallboard also decreased. Declines in auto-mobile manufacturing resulted in reduced production

May 1, 2010

By R. H. Moore, B. D. Breitenstein

INTRODUCTION The United States Uranium Registry (USUR) tissue program was funded in 1978 by the United States Department of Energy (DOE) through its Human Health and Assessments Division, and registrant enrollment began in 1980. It is operated by Hanford Environmental Health Foundation (HERF), Richland, Washington, with support provided by Pacific Northwest Laboratory (PNL).** The USUR tissue program is the first systematic effort to contact and gain assistance of workers occupationally exposed to uranium and to seek and study uranium deposition in human tissue. This paper describes the program objectives, populations selected for study, procedures for enrolling workers in the program, types of tissue to be studied, and analytical procedures to be used. PROGRAM OBJECTIVES The objectives of the USUR tissue program are to: 1) Determine the distribution and concentration of uranium, if any, in the tissues of occupationally exposed workers. 2) Compare bioassay measurements of exposed individuals with the results of analyses of tissues obtained at autopsy. 3) Seek evidence of histopathologic changes related to any uranium deposition that may be present. 4) Conduct analyses of whole bodies, when available, to obtain more precise data on the uranium burdens, if any, in the body and organs, and especially the distribution in parts of the body, such as the skeleton, that are not usually accessible for sampling. 5) Develop data that will assist in evaluating a) the accuracy of current in-vivo measurement techniques, b) the propriety of existing regulations, and c) the adequacy of current protection programs. SELECTION OF POPULATIONS FOR STUDY Selection of the populations for the USUR tissue program was based on studies of the United States Uranium Registry described elsewhere (0c81). Potential populations for study were quite varied because of occupational exposure to different chemical forms of uranium, different levels and eras of exposure, varying ability to identify populations exposed in the past, and the general interest and cooperativeness of the populations. Nevertheless, certain identifiable populations emerged that were both willing to participate in the study and likely to provide useful information. Among the targeted populations are individuals who were exposed to uranium prior to the existence of modern exposure standards. These individuals are presently being enrolled by the USUR. The reliability of concentration and distribution data and the demonstration of effects are more likely in such individuals than in those who have received less exposure. However, the targeted groups also include individuals who Have been exposed to permissible levels of uranium, and reference employees in uranium plants who have not worked with uranium. The lesser exposures are of immediate interest because of the rarity of heavy exposures under current standards. The sampling of potentially exposed individuals with negative in-vivo measurement results may serve to check the adequacy of in-vivo measurements in the detection of deposition. [ENROLLMENT PROCEDURE] The enrollment of participants follows three patterns. 1) Presently employed workers are enrolled by the cooperative efforts of USUR staff with the medical, industrial relations, and/or health physics personnel of the uranium facility. Volunteers may be enrolled by medical personnel at the time of their physical examination or by health physics personnel at the time of a bioassay or lung counting procedure. Follow-up after initial contacts with currently employed uranium workers is carried out by on-site personnel, but subsequent follow-up is the responsibility of the Registry. 2) Retired workers are contacted by mail, with a covering letter from their former employer supporting the principles of the study but leaving participation in the program on an entirely voluntary basis. 3) An alternate method of enrollment is to obtain a USUR autopsy consent after death from the next of kin. As part of enrollment in the program, permission is requested for access to the individual's medical and exposure data, and a short occupational history is filled out. The autopsy permission agreement signed by the individual is for an initial period of 5 years; the USUR ordinarily seeks renewal of the agreement upon its expiration. While this agreement provides

Jan 1, 1981

By Alfred G. Hoyl

The author, in exploring a virgin area vertically in two known ore shoots requiring decline shaft sinking, drifting, crosscutting and diamond drilling, chose to use electric, electric hydraulic, and diesel rubber-tired equipment. A rebuilt hoist, and electric hydraulic shaft shovel (mucker), hydraulic sinking drills, single boom electric hydraulic jumbo, electric hydraulic LHD, and electric hydraulic diamond drill were used successfully. Slides of the equipment and its use are shown. The advantages and disadvantages of the equipment are discussed, together with costs and production.

Jan 1, 1984

By K. Oraee

Mining Ventures are considered as high risk projects and therefore managing the risks is inevitable. Risk assessment is an important part of the complex process of risk management, hence applying appropriated and practical methods for ranking the risks associated with projects, can help to perform a better risk management. In this research the applicability of using Techniques for Order Preference by Similarity to Ideal Solution (TOPSIS) method for risk ranking in an underground mine, extracting by block caving method, was studied. Via this method, the risk associated with reserve estimation ranked as the first while in conventional method (P-I Matrix method) located in the sixteenth. Also there were significant differences in ranks of the other risks. Considering the more criteria, with different weights, in comparison with conventional methods, the results comprised from TOPSIS method are more reliable. By implementing this method risks are ranked better and more realistic and consequently then will be managed more efficient.

Jan 1, 2011

By A. Taghavi, I. Hassan, A. Solecki

"The Eglinton Crosstown Light Rail (LRT) Project is part of an $8.4 billion investment to expand transit in the Toronto, Canada area and is the largest transit project initiated in Province’s history. Settlement control and impact to over 1400 adjacent structures due to tunnelling was identified early as a critical project risk. The ground conditions along the 10km tunnel alignment consist of water bearing soft ground deposits (clays, sands, silts) which required careful analysis and control during design and construction. This paper will describe the process used to analyze settlements along the numerous of adjacent structures and evaluate achieved settlement results to those used during design. The paper will demonstrate that with the appropriate design specifications, selection of modernized EPB machines, and contractor performance, settlement can be maintained well below typical industry (volume loss) standards, expanding the application and suitability of soft ground tunnelling in sensitive settlement areas. INTRODUCTION The Eglinton Crosstown Light Rail Transit (LRT) Project is part of an $8.4 billion (2010$ CND) investment from the Ontario provincial government to expand transit in the Toronto, Canada area. The project is being developed by Metrolinx, an agency of the Government of Ontario to provide 19 kilometers of dedicated LRT service connecting the City of Toronto from the west to east along Eglinton Avenue. Upon completion in the year 2020, the Crosstown will be the first LRT constructed in Toronto. It will link regional and local transit, cut travel time along the route by half and provide over a thousand jobs during construction."

Jan 1, 2016

By F. L. Jackson

The large scale transportation and storage of sulphur in the liquid state is a relatively new development, but is really only a logical extension of old mining and processing techniques, It is not known who the first person was to win a relatively pure sulphur from ore by melting, but this method was commercially used at least two hundred years ago in Sicily and is still in use today. The Frasch process of mining was invented over sixty years ago, and the development and improvement of-liquid sulphur pumping and handling techniques has paralleled the growth in the Frasch mining industry. During the last fifty years, improvements in the technology of using sulphur have included the premelting of sulphur prior to its being burned for acid production or conversion into CS2 and other compounds. Yet, until fairly recent times, sulphur produced as liquid has been solidified into large blocks at the producing point, broken down by blasting or with mechanical equipment, and shipped in bulk form as a solid.

Jan 1, 1962

By Francis S. Kendorski

INTRODUCTION Caving offers the lowest cost per ton of any large-scale mining method, but its successful application demands an ore body that conforms to several rigid requirements. The deposit must be of wide areal extent, massive and not spotty in ore values, and insensitive to ore dilution. It must also be a rock mass that breaks up readily. There are only three active caving operations in the US-Climax, Henderson, and San Manuel-but caving methods have recently taken on new importance as deeper lower grade mineral occurrences and ore bodies are found. These deposits are too deep for surface min¬ing methods, and too low grade to support any type of underground mining except a bulk method such as caving. Announced discoveries or indications that may be amenable to caving include: Climax's Mt. Emmons molybdenum discovery in Colorado; Molycorp's Goat Hill molybdenum prospect in New Mexico; the Phelps Dodge molybdenum deposit in Beaver County, UT; Arizona copper occurrences such as Asarco's Sacaton, Hanna's Casa Grande, Noranda's Lakeshore, and Ken¬necott's Safford; Anaconda's suspected deep copper de¬posit in Butte, MT; Anaconda's Carr Fork, UT, deposit; and perhaps others. CAVABILITY'S ROLE IN FEASIBILITY STUDIES Caving is a system of underground mining which removes support from underneath an ore body. As a result, the rock mass fractures, fails, and flows vertically downward by gravity to be collected in previously ex¬cavated funnels. Types of ore that have been mined by caving include molybdenum, copper, iron, nickel, as¬bestos, and diamonds (Julin and Tobie, 1973). It is primarily a large-scale method, with production rates of more than 45 300 t/d (50,000 stpd) having been achieved. However, the initial capital investment before return is very high, often in the hundreds of millions of dollars. The cavability of an ore body or mineral occurrence is a critical item in the feasibility study of a proposed mine, not only from the point of overall minability, but from the point of impact on other costs such as blasting, loading, hauling, crushing, and grade recovered. Aside from the often-asked question of, "Will it or will it not cave?" the real questions are, "Can we afford to make it cave, carry the rock away, and extract the mineral?" The last is not a topic of this chapter, but the first two are. The cavability of an ore deposit or mineral occur¬rence is based on many things, but clearly, if a large enough area is undermined, any rock mass will cave. The result could be a violent collapse as occurred at Urad, CO (Kendrick, 1970), or perhaps the rock mass will cave beyond the ore boundary. Another unfavor¬able result could be ore blocks that are too large for the equipment and orepasses to handle without considerable secondary blasting. Weak rock with numerous fractures may produce a very fine ore when it caves, resulting in dilution and ground control problems. DETERMINING STRUCTURAL DOMAINS It has long been recognized that the geologic nature of an ore body is important to cavability (King, 1946). Such items as weak rock material, intensity of fractur¬ing, and severity of faulting all contribute to the success of a caving operation, and information regarding these is required as a minimum for the cavability determination. In practice, the rock mass-defined as the blocks of intact rock together with the intervening fractures, joints, faults, bedding planes, and other discontinuities-that contains the ore body, as well as the surrounding and overlying rock, must be examined in a systematic and detailed fashion. Surficial geology maps must be pre¬pared, exploration holes drilled, and core logged for en¬gineering information. The fracturing of the rock mass must be studied to ascertain the three-dimensional dis¬tribution of fractures and their characteristics, and faults must be located and described. The strength and other mechanical properties of the rock material, the fracture surfaces, and the fault filling materials must be tested and reported for later use by designers and planners. With this basic information and an understanding of the geologic setting, the rock mass can be divided into one or more structural domains which tend to behave similarly in response to engineering activities (Robertson and Piteau, 1970). One must keep in mind that the determination of the structural domains goes beyond the geologic units present. Several lithologic units may be lumped together, while a single lithologic unit can be divided into multiple domains. Major faults often form their own domain, and the direction of engineering ac¬tivity-for example, cave advance to the north rather than the south-may alter rock mass behavior, resulting in different domains. As an example of the detailed rock fracture map¬ping required for such studies, the structural domain determinations at the Climax mine (Kendorski, 1973) are shown in Fig. 1. The circles are Schmidt equal area projections of the three-dimensional attitudes of frac¬tures (Ramsay, 1967) mapped in detail at various rock exposures. The attitude of fractures is important to the cavability determination since it dictates the directional behavior of the rock mass as it fails, and determines the effectiveness of arching, keying, and rock block inter¬locking. Low-angle fractures must be present to allow movement of the rock in the vertical direction during undermining (Mahtab and Dixon, 1976); if low-angle planes of weakness are absent, the rock mass may arch with a keystone effect, rather than moving vertically downward.

Jan 1, 1982