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By Nathaniel Arbiter

Flotation’s earliest patent was issued in 1860. However, the process was first applied commercially in Australia until 1904, and in Montana in 1911. Major advances followed both in reagent treatment and in cell design, with resulting process improvements. Mechanical cells have seen the widest use and with the major increases in plant capacities (Fig. 1) their volumes have also increased (Fig. 2). In 1991, the principal use for the process was to produce copper concentrates for smelting. It was applied to 243 Mt (268 million st) of copper ore. The total of all ores floated that year was 426 Mt (470million st). In 1997, US mines produced 257 Mt (284 million st) of copper ores for flotation, yielding1.75 Mt (1.94 million st) of copper.

Jan 1, 2000

By W. P. Diamond, S. L. Cario, F. Garcia, J. D. Byars, T. P. Mucho

The National Institute for Occupational Safety and Health (NIOSH) has been conducting research at a Pittsburgh Coalbed longwall mine to evaluate and optimize bleeder ventilation and gob gas venthole longwall methane control systems. Gas flow into these two methane control systems was investigated using a combination of Sulphur Hexafluoride (SF6)tracer gas studies and gob venthole pressure monitoring experiments. The insights gained from this research has facilitated the development of a longwall subsided strata methane control system conceptual model. This model provides the basis for design suggestions to increase the efficiency of the gob gas venthole system to permit the bleeder ventilation system to become a "safety net" for methane control.

Jan 1, 2000

By Kevin Sharman, Peri Mehling

A detailed assessment of acid rock drainage (ARD) potential was conducted at the Quintette Coal Mine site in northeastern British Columbia The site is unusual in that the coal seams contain low sulphur levels as compared to eastern coals (typically less than 0.5%), and the non-coal wastes generally do not to have the potential to generate acid on the basis of static ABA tests. The presence of small iron-stained seeps on the pit walls indicate localized sulphide oxidation, while the overall mine site drainage has remained of excellent quality with extremely low levels of metals after approximately 15 years of mining. Thus the site provides an excellent comparison to more problematic coal mine sites. For the Quintette assessment, static acid-base accounting (ABA) analyses of individual samples were compared to criteria for potentially acid generating materials developed for the U.S. Appalachian coal, as well as criteria developed in British Columbia for hard rock mines. Geologic units were characterized by the percentage of samples, or weighted thickness, that was deemed potentially acid generating (PAG). Links were then made to actual seepage and water quality emanating from geologic units around the site. Seeps at the site demonstrate a large range in pH (2.32 to 8.18). The few acidic seeps (pH < 4.0) were found to contain elevated levels of sulphates, dissolved iron, manganese and aluminum, consistent with the metals typically of concern in Appalachian coal mines. Other heavy metals that were detected in acidic seeps at Quintette included copper, zinc, nickel and cadmium. The use of simple ABA tests, and comparison of individual sample results with the Appalachian and British Columbia criteria, was found to be useful in predicting the probable sources of the small localized acidic seeps.

Jan 1, 2000

By T. R. Rehak

Blasting operations are an essential element in the recovery of our Nation?s mineral resources. The mining industry uses billions of pounds of explosives annually. The majority of blasting occurs in surface mining operations. Blasting results in the fragmentation and often the projection of rocks. Frequently, the rocks are thrown beyond the expected limits. Flyrock and failure to secure the blasting area dominate blasting-related accidents in mining, especially in surface mining. Blasting accidents in the mining industry tend to result in critical injuries or fatalities. Accident reports and information collected from the Mine Safety and Health Administration (MSHA) and other government agencies provide supporting evidence. According to the data collected, blasting-related accidents (in mining) were 11 times more severe than all other types of mining accidents. Blasting accidents are not unique to mining operations - the same situation exists in the construction field. In this paper the authors have compiled a list of the primary causes of flyrock and the failure to secure the blast area. In the next phase of this project, typical blasting scenarios will be reviewed which will highlight the main reasons flyrock and/or lack of blast area security occur. This will alert miners and construction workers to the current problems/hazards associated with blasting and to identify other safety measures to protect personnel.

Jan 1, 2000

By H. L. Ehrlich

Marine manganese nodules harbor a mixed population of manganese-oxidizing and -reducing bacteria, as well as bacteria that do not act on manganese. They also host phagotrophic protozoa. Out of several laboratory studies, one line of investigation indicates that some kinds of bacteria found on nodules can catalyze the oxidation of Mn2+ bound to Mn(IV) oxide at the surface of nodules at in situ temperature and pressure. In the absence of appropriate bacteria, the rate of oxidation of the surface-bound Mn2+ is significantly slower. How Fe(III) is incorporated is still unclear. Base metals such as Cu, Ni and Co, which are usually found in marine nodules in various quantities, may be incorporated through scavenging by Mn(IV) oxide. Laboratory evidence shows that some other bacteria on nodules can reduce the Mn(IV) oxide to Mn2+ in the presence of an appropriate source of reducing power in the form of organic carbon. The reduction of Mn(IV) oxide mobilizes manganese and trace metals such as Cu, Ni, and Co in the nodules. These bacteria reduce Mn(IV) whether oxygen is present or not. They could be harnessed in the bioleaching of nodules. The manganese(IV)-reducing bacteria and the bacteria that neither oxidize nor reduce manganese are thought to keep the organic matter in the nodule environment sufficiently low to favor bacterial manganese-oxidation, which in laboratory tests is inhibited by excess organic carbon. The preying by the protozoa on the different kinds of bacteria is thought to control the bacterial population on nodules and ensure continued growth of the manganese-oxidizing bacteria and the nodules. To eliminate interference from seawater salts in the bioleaching of Mn, Cu, Ni and Co, it may be more advantageous to use terrestrial Mn(IV)-reducing bacteria than the Mn(IV)-reducing bacteria resident on nodules. The terrestrial bacteria would allow bioleaching in fresh water. Unlike the marine bacteria, most terrestrial bacteria studied to date reduce Mn(IV) oxide only anaerobically. A general outline for an anaerobic bioleach process of marine nodules with freshwater bacteria is discussed.

Jan 1, 2000

Syncrude Canada produces a large part of Canada’s crude oil supply. The company processes about 225,000 bbl/day. The oil produced is used for jet and automobile fuel, home heating oil, plastics and other consumer synthetics. Crude oil is produced through a process of mining, extracting and upgrading bitumen. A rich supply of bitumen is contained in the Athabasca oil sands deposit in northern Alberta. Tailings from the bitumen processing are sent to a settling basin.

Jan 1, 2000

By C. Rodgers, E. (Ted) Warren

"LocationThe Key Lake operation of Cameco Corporation is located at latitude 57°N in northern Saskatchewan, within the southem boundary of the Athabasca formation. The nearest city is LaRonge, located 240 km to the south. Access to the mine is by all-weather road and by private airstrip.Description of OperationThe mill was designed to produce twelve million pounds of uranium oxide (U3O8) a year from a feed grade of 2.4% U3O8. Current production is fourteen million pounds from 2.0% feed.Following grinding, the uranium is leached using sulphuric acid and oxygen in autoclaves. An eight thickener counter current decantation (CCD) circuit is used to separate the uranium-bearing solution from the solid waste residue. The uranium in solution is further purified in a solvent extraction circuit. The purified uranium is then precipitated using ammonia, calcined at 840°C, and packaged in drums for shipping to refineries. There is a crystallization circuit to recover excess ammonium sulphate produced in the process, and a waste treatment circuit.HistoryUranerz Exploration and Mining discovered the Gaertner and Deilmann orebodies in 1975 and 1976, respectively. Between 1975 and 1977, Uranerz conducted laboratory studies and delineated a process for the Key Lake ore known as the ""Bonn process."" In 1977, Sherritt Gordon Mines Ltd. was retained to conduct further studies in cooperation with U ranerz. The technical feasibility of the Bonn process was generally confirmed. Howeve1~ alternative processing methods also appeared feasible, and over the period 1978-1979, a detailed research and development program was conducted to finalize the processes to be used and to provide data for design of the plant."

Jan 1, 2000

By D Pilone

The Tyrrhenian micro-nodules, findable at low depths (200/600 m under s l) are a reasonable reserve of manganese. They can be easily and cheaply recovered but do not contain valuable metals as in the case of oceanic nodules. In this work a hydrometallurgical process for manganese recovery from Tyrrhenian nodules is presented. The studied treatment includes the following operations: magnetic enrichment, reducing leaching, leach liquor purification and electrowinning . The study shows that the most important step in the process is the preliminary manganese enrichment. It can be done directly on the platform reducing not only the transport cost, but also the residue mud in the metallurgical plant. The leaching parameters such as status and size of nodules, temperature, composition of leaching solution and S/L ratio have been investigated. After purifying the leach liquor by iron precipitation as ammonium jarosite , the conditions to electrowin manganese have been investigated. The yields of both manganese leaching and iron precipitation together with current efficiency and specific energy consumption in the electrowinning step are given.

Jan 1, 2000

By Melvin I. Esrig

Lime Cement column stabilization of soft clay and sand in Salt Lake City, Utah and in San Francisco California is described and discussed. Stabilization permitted the construction, in a single stage, of a 14 m MSE wall on "medium" clay in Salt Lake City. It was used to mitigate the potential for liquefaction in San Francisco and to stabilize the Young Bay Mud beneath the BART extension to San Francisco Airport. These applications are described and the field measurements of performance are reported.

Jan 1, 2000

Laboratory tests were conducted to study the effects of thrust or pull-down force and rotary speed on the vibration signatures of a particular drill in a known rock type, and to determine how the vibration signatures could be used to assess bit wear. The vibration signatures were analysed using a Wavelet Transform analysis technique, which decomposes the signals in multi-bands of frequency and presents the results simultaneously in time and frequency domain. Results show that as the bit wears, large fluctuations in amplitudes in the high frequency ranges occur, and prominent peaks in the low frequency ranges were observed for a worn bit. The Wavelet Transform technique provides an appropriate and effective metrics for monitoring and evaluating the state of wear as drilling progresses through the post-processing of wavelet coefficients. This study provides a basis for the development of an on-line detection technique of bit wear in rock drilling through Wavelet Transform technique or time-frequency analysis that can be used in real time.

Jan 1, 2000

By S. S. Chabot, S. E. James

A recent survey of CEOs from major steel companies worldwide revealed the importance of recycling zinc units from EAF dust, mill scale, blast furnace dust, and other zinc containing streams in their plants. Many processes were developed and installed in response to this challenge. The most successful approach involves the production of a crude zinc oxide and selling it to primary zinc producers to recover the metal value. The problem with this process is the high concentration of halides in the crude oxide. This type of material cannot be processed directly in an electrolytic zinc plant because of corrosion problems it will cause in electrolysis. In 1999, BRZ installed a zinc oxide receiving and washing plant to minimize the impact of halides to its circuit. A description of the washing plant and initial operating results are included.

Jan 1, 2000

By Mehmet F. Taner

"Abstract - "Les Mines Selbaie" is a large, generally low-grade, polymetallic (Zn, Cu, Ag, Au) "giant" volcanic-associated ore deposit in the Harricana-Turgeon belt, which is part of the northern Abitibi Subprovince of Quebec. Economically recoverable mineralization occurred in three zones: the A1 (open pit), A2, and B Zones (underground). The pre-mining resource was 54.9 Mt, including 8 Mt of sub-economic, locally silver-rich massive pyrite. In the Selbaie region, calc-alkaline andesitic volcanics form the "basement." The Brouillan Volcanic Complex formed within an islandarc setting on this regional basement. Evolution of this complex involved the formation of a felsic magma chamber and the development of a large caldera structure over the Brouillan batholith. Second- order linear and sub-parallel faults and rifts developed as a result of back-arc rifting/extension. The edges of these rifts were feeders for linear felsic volcanism (similar to fissural volcanism). During felsic volcanism, the feeder zones acted as conduits for hydrothermal fluids with associated pervasive potassic alteration. The alteration is characterized both vertically and laterally by well-defined quartz, sericite, K-feldspar and/or, locally, biotite halos, to produce a mushroom-shaped morphology. This K-feldspar alteration is not common in most other volcanic-associated ore deposits. Mafic dikes cut all of the geological units and appear to occupy earlier synvolcanic structures. Regional greenschist- assemblage metamorphism and pervasive deformation affect all units. Thrust faults moved part of the Brouillan batholith and basement units over the Mine Sequence. Although there is no relationship between the earlier mineralizing events and these late thrust faults, the thrust faults probably played an important role in location of ore lenses. Three types of mineralization are present: 1) copper-rich veins and hydraulic breccias; 2) disseminated and stringer, low-grade and high volume zinc-copper mineralization; and 3) finely laminated, massive, locally silver-rich pyrite mineralization within structural basins. At the bottom of these basins and at the contact of welded acid tuff (WAT) units, massive pyrite zones are locally enriched in zinc, and contain the possible vestiges of black smoker-like material. The ore metals were probably derived from leached basement andesitic volcanics in a hydrothermal system powered by one or more heat sources within the Brouillan Volcanic Complex. The Selbaie deposits are mainly characterized by: (1) the presence of small volcano-tectonic subsidence basins, which host chemical sediments and volcaniclastic materials; (2) pervasive potassic alteration; (3) locally high-grade silver mineralization (up to 1-2 kg/t Ag); and (4) the presence of random zones of Pb mineralization. The Selbaie deposits can be closely compared with the copper-rich Murgul deposits, which belong to the eastern Pontides metallogenetic province in Turkey. If conventional classification criteria for the volcanogenic massive sulfide deposits (e.g., Noranda, Mattabi types, and recent subsea floor deposits) are taken into account, the Selbaie deposits still exhibit many differences in terms of alteration assemblages, physical volcanology and some styles of mineralization (low-grade and large volume). Consequently, the "Selbaie" deposits belong to a new sub-type of volcanic-associated sulfide deposit, which may be used in future exploration programs."

Jan 1, 2000

By James M. Cairns

Deep Sea Minerals Inc. (DSM) is a high technology marine minerals and biotechnology corporation. The corporation is currently engaged in a worldwide leasing program to acquire exclusive rights in specific Economic Exclusive Zones (EEZ?s) that DSM?s marine geologists have identified as prospective targets for seabed mines of copper, zinc, gold, and silver. In the last two years the corporation has assembled an international team, including some of the world?s leading marine research scientists and engineers, and has created strategic partnerships and alliances with world-class engineering and mining groups. Development of a marine mining venture has key requirements in common with most other mining ventures. These include financing, deposit location, property acquisition, deposit delineation, and permitting, as well as the collection, transportation, processing and marketing of the ore itself. DSM has made progress on all of these fronts, which is outlined in a general way in this presentation. Financing for the venture is clearly the first big hurdle to overcome. Deep seabed mining involves new technologies and significant up-front capital investment. Less than fifteen years ago, such financing would probably have impossible to achieve, given classical business models. However, with the spectacular success of high technology ventures in the areas of electronics, software, and biotechnology, new business models and investment strategies have evolved which put relatively high evaluations on intellectual property and exhibit relatively high confidence in new ways of doing things. DSM is taking full advantage of these changes in venture capital markets in its financial planning.

Jan 1, 2000

By R. D. Lawrence

Suggestions have been made that the appraisal of mining assets using discounted cash flow techniques should be based solely on proven and probable reserves in reliance upon the widespread international recognition of uniform resource definitions. Following a review of general accepted valuation principles, a survey of the literature and, most importantly, a review of real transactions in the open market, it is clear that valuators should not be constrained by the growing acceptance of modern mineral resource codes. On the contrary, valuation practitioners should be encouraged to examine all classes of mineralization and, after making due allowance for risk, to utilize all mineral resources as a basis for determining fair market value.

Jan 1, 2000

By Simon C. Dominy, Ian M. Platten, Garry F. Johansen, Alwyn E. Annels, Brian W. Cuffley

Abstract - Coarse gold-bearing veins are characterized by high grades that are localized and erratic. Effective sampling of coarse gold-bearing veins is difficult because of the low concentration and erratic nature of the gold particles. Diamond drilling is an effective measure of geological continuity, however, grade distribution can only be reliably obtained from underground development (including close-spaced sampling, bulk sampling, and trial mining). Comparison between surface and underground drilling, underground linear/panel and bulk sampling indicate that drilling and linear/ panel samples generally understate bulk sample grades. Bulk samples are likely to be the closest estimators of true grade. It is unlikely that anything above an Inferred Resource category can be estimated from surface drilling alone, and at best the grade will only be a global estimate. Underground development, in-fill drilling and bulk sampling/trial mining will be required to delineate Indicated and Measured Resources. Closely spaced development and bulk sampling is likely to be the only way to determine Reserves. The resource estimation process must driven by a clear geological model that should attempt to understand both geological and grade continuity. Traditionally, grade interpolation has been undertaken using classical methods, though more recently, computer-based block modelling techniques have been used with some success. Three case histories are presented, documenting the problems of estimating resources in coarse gold-bearing veins and the practical ways in which they were approached.

Jan 1, 2000

By D. H. Flather, J. W. Hendry, K. Drover

Black Hawk Mining Inc. has completed a comprehensive program on the prediction and management of acid rock drainage (ARD) at their Keystone Gold Mine (Keystone) near Lynn Lake, Manitoba. The program, initiated in 1994, followed a phased approach utilizing initial acid-base accounting (ABA) results and subsequent laboratory kinetic testwork to define site-specific sulphide oxidation and neutralization consumption rates in waste rock. Net acid generating waste rock at Keystone was defined through the kinetic testwork as waste rock yielding a net potential ratio (NPR) of less than two. A preliminary waste rock management program based on blending of potentially acid generating and acid neutralizing waste rock was advanced. Subsequent refinement of the management program followed the analysis of over 1580 ABA samples collected from individual blast holes during the initial bench development phase of the Keystone pit. Uncertainties in actually achieving adequate blending within the dumps at a mining- scale resulted in the development of a revised waste rock management program based on segregation. Recognizing that any successful management plan requires that the ARD characteristics of the waste rock be identified prior to in-pit blasting, the extensive ABA database was utilized to develop a rapid characterization scheme. By implementing a characterization scheme based on total sulphur concentrations and fizz rating, waste rock could be quickly segregated without delaying the natural flow of ore from the pit. Interestingly, it also became apparent that gold values were strongly correlated with total sulphur, such that traditional fire assays were supplanted with a simple and more cost-effective total sulphur determination. The program highlights the importance and benefits of collecting and exploiting data beyond that necessary to acquire appropriate development permits.

Jan 1, 2000

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Jan 1, 2000

Just as geophysics, in the form of 3D seismic and wireline logging, plays a key role in petroleum reservoir management, so too will geophysics play an important role in mining of coal, metals, and minerals in the 21 st century. The commercial and social imperatives driving greater use of geophysics are reduced costs, increased revenues, and enhanced safety. In short, superior utilisation of capital and management of risks. In relatively undeformed sedimentary environments it is possible to adapt petroleum-style 3D reflection seismic to image mines. This has been demonstrated most impressively in the Witwatersrand. Anglo-American, for example, completed a $1 million 3D seismic survey at Western Deeps in order to site a new $300 million shaft with confidence. Likewise, 3D seismic has gained rapid acceptance at Australian coal mines in recent years. Encouraged by these successes, metalliferous mining companies are supporting research in Canada and Australia, as well as South Africa, to adapt 3D seismic for more highly structured, metamorphic terranes. Because the mining industry is far more diverse than the petroleum industry in terms of commodities and geological environments, 3D seismic is not always cost-effective. A plethora of other geophysical techniques can be applied, many of which are employed in mineral exploration. Mine applications of geophysics differ from traditional exploration applications in two main ways: time scales and length scales are shorter, and boreholes are more plentiful. Borehole geophysical techniques therefore play a more significant role, both for logging and imaging. Logging systems detail the variations of in situ physical properties down the borehole at scales measured in centimetres, while geophysical imaging techniques can map features located tens or even hundreds of metres from the sensors. While geologists tend to think of boreholes in terms of chips and core, geophysicists perceive them first and foremost as access paths for instruments. Borehole logging has been employed at iron and coal mines for decades, mainly to accurately define ore boundaries in delineation holes. In base metal mines, Outokumpu implemented logging widely for orebody delineation in percussion holes in the 1980s. The benefit was a direct cost-saving, arising from substitution of core drilling with percussion drilling plus borehole logging. The practice has since spread to other companies. INCO, for example, defines nickel boundaries in blast holes at Sudbury using conductivity logs. The benefits are in the form of reduced dilution and enhanced ore recovery, flowing from a more accurate mine model. Density, natural gamma radiation, magnetic susceptibility, and conductivity are the principal metalliferous mine logging parameters because they can be recorded in both dry and water-filled holes. Sonic velocity is the premier geotechnical logging parameter, given its sensitivity to rock strength, stress, porosity, and degree of fracturing. Sonic is recorded routinely in exploration and geotechnical holes at coal mines. With the advent of slimline dipmeter, full waveform sonic, and optical and acoustic scanner tools, the role of borehole logging in geotechnical evaluations is expanding. Monitoring of strain and micro-seismic activity enhances safety during mine production. While qualitative interpretation of logs is adequate for stratigraphic identification or definition of boundaries, a wealth of quantitative information, eg density, can be derived from properly calibrated, repeatable geophysical logs. Moreover, geophysical logs can sometimes serve as surrogates for geochemical assays, and not only for magnetite and uranium. At OutokumpuÆs Kemi chromite mine, for example, gamma-gamma logging provides the basis for grade control. By reducing reliance on assaying, three benefits can be realised: reduced reliance on core drilling; lower core handling and assaying costs; and shorter turn-around times. Conventional downhole EM and borehole magnetics are used for near-mine exploration, and for ground sterilisation. Inco has enjoyed considerable success with borehole UTEM in the Sudbury Basin, for example, and Geopeko has applied three-component borehole magnetics successfully in the Tennant Creek area. Electrical techniques such as applied potential and magnetometric resistivity (MMR) are also finding application at mines. For higher resolution, borehole seismic, radio imaging, and radar have been invoked, with varying degrees of success, to delineate orebodies and map structures, or to geotechnically characterise the rock mass and identify hazards. Success mapping nickel sulphide shoots with borehole radar has been reported by WMC at Kambalda. There are no universal geophysical panaceas, and each mine imposes different geological, logistical, and economic constraints. Geophysics will not always be cost-effective. However, the greatest single impediment to expanded use of geophysics at mines has been the low level of awareness of geophysics on the part of most mine geologists, engineers, and managers and, equally, the limited understanding of mine geology and engineering exhibited by the majority of geophysicists. This myopia will be remembered as a 20th century affliction! Blue Sky areas for mine geophysics in the next ten years include integration of geophysical data acquisition with drilling, enhanced grade estimation and rock mass characterisation, and the incorporation of geophysical information into mine models using geostatistical techniques. All these advances will be predicated on an expansion of petrophysical knowledge.

Jan 1, 2000

By N. S. Yet

This paper shall present the design and construction of bored pile and diaphragm wall for the proposed MHA complex in Singapore. The work was carried out by L&M Foundation Specialist Pte Ltd and PWD Consultants Pte Ltd was the consultant for this project. A brief description of the project is first presented to illustrate the scope and scale of the work involved, which includes the construction of bored piles and diaphragm walls and installation of steel stanchions in the bored piles. This is followed by a description of the methodology used to analyse and design the wall and bored piles. As both towers in this project are supported on bored piled foundation and are constructed by top down construction method, the analysis of the wall has taken into consideration the sequence of work phase by phase and this was carried out by means of a commercial finite element program called CRISP. Modelling of the problem will be briefly described and the findings from the numerical analysis will be presented. This is followed by a description of the structural and geotechnical design aspects of bored piles. The paper shall then describe the difficulties encountered for this project and solution used to solve the problem. The subsoil condition will be described with special mention on the encounter of very strong granitic rock at depth above the maximum excavation level of the basement at certain locations, hence necessitating the drilling of rock for a considerable depth for both bored piles and diaphragm wall. At this juncture, the construction method used to drill through the rock will be briefly described. For construction of bored piles, penetration of rock was carried out by chiselling or drilling using reverse circulation rigs. For construction of diaphragm wall, it requires the employment of Bauer hard rock cutter which uses cutting wheels fitted with roller bits and are capable of excavating into granitic rock of compressive strengths more than 100 MPa.

Jan 1, 2000

The excavation of ramps and tunnels often requires high-speed development with (or without) the use of high-energy mining equipment such as loaders, dump trucks, TBMs and roadheaders. This high-speed development creates a challenge in terms of providing a safe and productive working environment. For example, heat from continuously exposed surrounding rock, heat from broken rock, heat generated by mining equipment, potential in flows of hot ground water, pollution from associated diesel equipment and the distance of the advancing face from fresh through-ventilation all have to be taken into account when designing ventilation systems for high-speed ramp and tunnel developments. This paper discusses methods of achieving acceptable environments at the face and along the length of the tunnel. The methodology has been successfully implemented in the development of long (up to 20 km) TBM drives in the Lesotho Highlands Project and in mining projects in hot rock using drill and blast methods as well as mechanized methods using continuous miners and roadheaders. The determination of heat loads includes calculation of the heat flow within the surrounding rock, evaluation of the operating cycle of the equipment and the contribution to the overall heat load of the broken rock as it travels out of the tunnel. The determination of heat loads from surrounding rock in new tunnels required a modification of the algorithms generally used for established excavations. The paper also examines the use of, for example, mobile duct and fan systems to ensure that fresh air is delivered to the specific areas where workers are located.

Jan 1, 2000