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By S. Norman Kesten

The Resource Conservation and Recovery Act, commonly known as RCRA, which amends the previous Solid Waste Disposal Act, was signed into law on October 21, 1976. Members of the mining industry began their contacts with EPA in this area two to three years before the Act finally was passed, and that seemed and probably was all to the good. We reviewed and commented upon their studies and in general tried to acquaint them with the peculiarities and the uniqueness of the wastes generated by our industry, of which they were abyssmally ignorant. I suppose we thought that through the bureaucracy we might have some influence upon the provisions of the solid waste legislation that was being bandied about on the hill. Certainly the industry, in general, did very little direct lobbying, as I recall, and there were several reasons for that. For one thing we conceived that the legislation was aimed at the chemical industy and believed that if their people looked after their interests, ours would be safeguarded automatically. Also, the Federal Land Policy and Management Act (FLPMA) was heating up at the same time and, in fact, was signed into law on the same day. In addition, a great deal of lobbying activity was required by amendments of the Clean Air Act and Federal Water Pollution Control Act that were being put together in Congress. These were conceived to be of far greater importance to our industry than a bill to control mostly chemical wastes and, in fact, new bills in both areas became law the following year. Finally, the solid waste bill, RCRA, was patched together by committee staffs over one weekend and was reported out by a conference committee rather hurriedly. Some little goodies about mining were almost after-thoughts in this process.

Jan 1, 1981

By B. Moudgil, Hassen El-Shall

Particle shape and size distributions are among the most important parameters that affect the filtration efficiency of phosphogypsum in wet- process phosphoric acid production. Cost-effective enhancement in filtration rate is desired by phosphoric acid producers for higher plant capacity and lower operating costs. In this regard, numerous research efforts have been carried out in different laboratories as well as in pilot and plant testing. Nevertheless, changes in phosphogypsum crystal shape and size distribution deserve special attention. In this study, the results obtained in the presence of Crysmod and Hiflo-S5 surfactants are discussed. The influence of such additives on crystal morphology and size distribution are studied under different sulfate contents (supersaturation). The obtained data are correlated with process efficiency parameters such as filtration rate, digestion of rock, and recovery of phosphate values. Up to 60% increase in filtration rate is obtained. In addition, an increase in digestion efficiency and P205 recovery is achieved due to addition of surface active agents. The observed beneficial effects are explained in the light of the changes induced in crystal habit, size, and size distribution.

Jan 1, 1999

By R. C. Shodde, R. D. La Nauze

Major societal and industry changes over the last four decades have influenced the management of technology in the minerals industry. From the authors' experiences in both private and public sector R&D, the paper analyzes the range of strategic and structural changes and provides examples of some key technology delivery responses. For those charged with managing technology, the two key challenges facing them over the next decade are (I) moving technology development from a cost focus to a value focus (that is, from "how much long-term research can we afford?" to "identifying and capturing the value created from R&D”) and (2) the recruitment and retention of key talent. THE NEED TO ADAPT "Change is slow and gradual. It requires hard work, a bit of luck, a fair amount of self- sacrifice, and a lot of patience (Greene 1998)." Since the 1960s the world has changed and the minerals industry has had to adapt to the changing circumstances. In the '60s, minerals were there to be discovered and fortunes to be made; in Australia, the World War I1 embargo on exporting iron ore was lifted and the Western Australian iron-ore boom commenced, to be followed by the exploitation of the Darling Range bauxites; copper, lead, zinc and nickel were discovered and mines developed. The Australian dollar was worth US$1.11 whereas today it is around US$0.65. The oil crisis of 1976 sharpened focus on the sensitivity of the minerals industry on energy costs. By the late 1970s The Club of Rome was predicting the imminent demise of certain key metals-a prediction that has not been fulfilled-though the signs of the shift

Jan 1, 2004

By Markus Thewes, Mario Galli

"INTRODUCTIONProject-related studies showed that lab tests are a helpful tool for the planning of EPB tunneling and soil conditioning in cohesionless soils. This type of ground commonly represents the extended application range for EPB shields, which demands for a treatment with additives. Considering soil conditioning with foam, so far, approaches exist for the investigation of the foam quality and of the conditioning behavior of soils (e.g. (EFNARC GUIDELINES 2001 2003)), but not any standards for testing procedures related to soil conditioning. State-of-the-art research on the topic is and was conducted for example in Bochum (Germany) cf. (Budach 2012; Maidl 1995), in Lyon (France) cf. (Quebaud et al. 1998), in Oxford and Cambridge (Great Britain) cf. (Borghi 2006; Peña Duarte 2007), in Delft (Netherlands) cf. (Bezuijen and Schaminée 2001), in Turin (Italy) cf. (Borio 2010; Peila et al. 2013; Vinai 2006), and in Aachen (Germany) cf. (Vennekötter 2012). Additionally, applied science is reported by the tunneling practice and suppliers of conditioning agents. Although the research focus in all these and further studies varied, similar test methods and test series were applied. A standardization of essential properties and testing methods (setup and procedures) however did not take place. The results from laboratory testing can only function as index values for practice because in the studies, production and application of the conditioning agents mainly takes place under atmospheric conditions. Nevertheless, the tests enable basic understanding of feasibility as well as processes and interactions going on during soil conditioning. For recommendations for standardized and reproducible testing see (Budach 2012; Budach and Thewes 2015).The most extensive investigations on the flow behavior of soil-foam mixtures have been performed by using the slump test from concrete engineering, cf. (DIN EN 12350-2 2009-08), which originally is applied on evaluating the workability of fresh concrete. Although this test does not describe the actual flow behavior, it rather represents an index on the workability, very much experience exists with this test method. Besides others, the workability – or flow behavior – of the EPB support medium certainly is a major factor of influence on the properties of the material in the excavation chamber and thus, for effective tunneling with EPB shields, cf. (Galli and Thewes 2014). For a summary of various investigations on the workability of conditioned soils using the slump test and resulting recommended slump ranges see (Budach 2012; Vinai 2006). Thereof, slumps between 10 and 20 cm have been reported as suitable workability for EPB applications. However, there is actually not much known about the real flow behavior of soil-foam mixtures related to rheological properties such as the viscosity (?) or potential yield stresses (t0). These physical values are necessary for a realistic determination of face pressure, for the design of required torques, and for an evaluation of the material flow at different locations in the excavation chamber, in the screw conveyor or on the conveyor belt. To generate a linear pressure distribution at the tunnel face, as it is assumed a priori, a low-viscosity fluid is favorable, whereas in the screw conveyor, a high-viscous fluid is needed for a controlled pressure decrease. On the conveyor belt, yield stress plays an important role preventing deliquescence and spilling from the belt. Attempts in characterizing the actual flowing of soil-foam mixtures have so far only been made by few researchers, the application of rheometry is rare."

Jan 1, 2016

By R. Schuerch, C. Cimiotti, G. Anagnostou, J. Nickerson, P. Perazzelli

"This paper presents experiences gained from the construction of the Lake Mead Intake No. 3 project. The 4.7 km long tunnel was excavated with a hybrid TBM (able to operate in both closed and open mode). The tunnel crossed metamorphic and sedimentary rocks under a hydrostatic pressure of about 14 bar. During the excavation of the tunnel the TBM encountered difficult ground conditions caused by a combination of high water pressure, poor ground quality and locally low depth of cover. The adverse conditions required the TBM to be driven in closed mode at very high support pressures (10 – 15 bar) for approximately 60% of the tunnel length. The paper summarizes the main problems encountered during TBM excavation and analyzes the evolution of the TBM parameters over the entire tunnel length. INTRODUCTION The Lake Mead Intake No. 3 project is located approximately 30 km away from the city of Las Vegas in Nevada, USA. The project consists of the construction of a deeper third intake for the biggest reservoir in the United States, which is formed by the Hoover Dam. The construction of the new intake was required due to the constant drawdown of the lake level (more than 40 m in the past 20 years) and the consequent risk that the shallower intakes 1 & 2 may run dry. The project included the fabrication and positioning on the lake bottom of an intake riser, the excavation and lining of a 185 m deep shaft and construction of a 4.7 km long tunnel. One peculiarity of the project is that the water table is located about 140 m above the tunnel elevation (i.e. corresponding to a hydrostatic pressure of 14 bar at the current lake level). The tunnel was constructed using a tunnel boring machine (TBM) able to operate in both open and closed mode (Mc Donald & Burger, 2009). The present paper focuses on the TBM tunneling experience gained from the Lake Mead Intake No. 3 tunnel. The TBM excavation started on December 27, 2011 and finished on December 10, 2014 with the breakthrough to the intake structure at the bottom of Lake Mead. GEOLOGICAL CONDITIONS The assessment of the ground conditions encountered during construction was mainly based upon qualitative descriptions of the tunnel face conditions (during open mode operations) and analysis of the extracted muck (during closed mode operations)."

Jan 1, 2016

By Stanislaw Wasilewski, Zdzislaw Krzystanek

The CMC-3 new generation system for continuous methane monitoring enables on-line measurement of methane concentration within the range of 0-100% CH4 with a great autonomy of operation. In principle the system has been worked out in the asspect of hazard detection in mines endangered with rock and gas outbursts. But after last crash in the Halemba colliery, according to the recommendation of the after-accident committee, the system was directed to this colliery for operational tests. The paper describes construction and functions of this system and gives some results of tests conducted at the Halemba colliery. The results point out the necessity of using monitoring equipment of continuous operation in mines of high dynamics of methane emission. INTRODUCTION Commonly used in Polish coal mining the methane monitoring systems of CTT/63/46 Up or CMM-20 and CMC-1 type are based on cyclic measurements with 4-minute repetition of measurements. This period has been stated sufficient from viewpoint of methane emission dynamics under normal exploatation. In these systems, automatic switching-off electrical power is performed by the surface station, i.e in case of detecting exceeded concentration value the station generates control pulse signal which actuates the switchng-off devices CRA and IZZO. Such a way of disconnection causes a considerable time delay, up to several minutes, in electric power break at hazardous areas. In the methane monitoring system with the new CMC-3 station, the different phylosophy of operation has been applied. Measurement of methane concentration is performed in a continnous way. In case of exceeding the alarm value, immediate control of the IZZO unit directly by methane monitor follows and consequently energy break without necessity of communicating with the surface station. Alarm values are set directly in methane monitor. The system ensures central powering of underground equipment from the surface, and in case of power failure the methane monitor equipped with battery operates autonomously for about 12 hours. Such an extention of the methane monitor funtionality has been achieved thanks to the use of internal microprocessor controller. The system with the CMC-3 station has been worked out in the aspect of methane hazard detection in mines exposed to gas outbursts. But after last gas explosion, according the desicion of the After-accident Commitee, the system was installed in the Halemba coliery where it underwent operational tests. Besides

Jan 1, 1993

By L. Alan Weakly

At a time when the US mining industry is struggling to emerge from a lengthy recession, the burden of new, unnecessary regulations could shorten the life of, or be fatal to many domestic mining companies. The possibility of new restrictions on the use of diesel equipment operating in underground mines is one example of unnecessary regulations. These could cause serious harm to the economic health of many mining companies. Whether future health-related Mine Safety and Health Administration (MSHA) regulations restricting the use of diesel equipment are unnecessary, depends on whether these restrictions are supported by fact or created in a political environment. The mining industry has benefited from the use of diesel equipment in underground metal-non-metal and coal mines for more than 50 years. Since first introduce to underground mines in the early 1940s, the use of diesel equipment has grown in numbers and size. During this time, the mining industry in America has achieved much higher productivity rates and improved safety. Although all these gains cannot be attributed to the greater use of diesel equipment, a high percentage can be. I began my professional mining ca¬reer in 1970 working in the Missouri lead mines. At that time, the use of diesel equipment was well established in metal-non-metal mines throughout the United States and many parts of the world. As director of mining research for St. Joe Minerals Corp. (now The Doe Run Co.), I was involved in research to improve mining productivity and safety. This involved investigating the better and safer use of existing or new mining methods, products, equipment and people. Within this group, diesel equipment had the single largest positive impact.

Jan 1, 1993

By Z. Jin, D. DePaoli, P. Zhang

"Phosphate beneficiation in Florida generates more than one tonne of phosphatic clay, or slime, per tonne of phosphate rock produced. Since the start of the practice of large-scale washing and desliming for phosphate beneficiation, more than 2 Gt of slime has accumulated, containing approximately 600 Mt of phosphate rock, 600 kt of rare earth elements (REEs) and 80 million kilograms of uranium. The recovery of these valuable elements from the phosphatic clay is one of the most challenging endeavors in mineral processing, because the clay is extremely dilute, with an average solids concentration of 3 percent, and fine in size, with more than 50 percent having particle size smaller than 2 µm, and it contains nearly 50 percent clay minerals as well as large amounts of magnesium, iron and aluminum. With industry support and under funding from the Critical Materials Institute, the Florida Industrial and Phosphate Research Institute in conjunction with the Oak Ridge National Laboratory undertook the task to recover phosphorus, rare earths and uranium from Florida phosphatic clay. This paper presents the results from the preliminary testing of two approaches. The first approach involves three-stage cycloning using cyclones with diameters of 12.4 cm (5 in.), 5.08 cm (2 in.) and 2.54 cm (1 in.), respectively, to remove clay minerals followed by flotation and leaching. The second approach is a two-step leaching process. In the first step, selective leaching was conducted to remove magnesium, thus allowing the production of phosphoric acid suitable for the manufacture of diammonium phosphate (DAP) in the second leaching step. The results showed that multistage cycloning with small cyclones is necessary to remove clay minerals. Selective leaching at about pH 3.2 using sulfuric acid was found to be effective for removing more than 80 percent of magnesium from the feed with minimal loss of phosphorus.IntroductionFlorida phosphate ore, or “matrix,” as it is called locally, contains three different mineral groups that have to be separated from each other: (1) phosphate minerals, (2) clay minerals and (3) quartz, or sand. As mined, the phosphate and sand particles are embedded in compacted mud, or clay-balls. Before separation can begin, all of the particles must be liberated from the matrix of mud. The very first unit operation in the beneficiation process is to disaggregate the various particles. This actually starts while the matrix is flowing through the multimile pipeline from the mine to the beneficiation plant. While in the pipeline, the matrix is exposed to shear forces as it passes through the various centrifugal pumps along the pipeline. These intense shear forces cause a significant percentage of the sand and phosphate particles to be liberated from the clay-balls by the time they arrive at the plant. Once they reach the plant, the first goal is to finish disaggregating the clay, and follow that by making a size separation at 1 mm. This processing is conducted in the washer, consisting of a large rotating trammel screen and a few stages of log washer, screens and hydrocyclones. In all of the currently operating beneficiation plants, the washer is a large structure that receives the matrix, screens it and then discharges a pebble phosphate product sized larger than 1.0 mm and a slurry of liberated clay, sand and phosphate particles that are smaller than 1.0 mm."

Jan 1, 2017

By Rob Robertson

The problem of fine coal slimes has been addressed in a unique way at A. T. Massey Coal?Company. Several plants have employed two-stage classifying cyclones to separate the minus 1 mm raw coal into 3 sizes. Larger cyclones make the initial cut at approximately 150 µ (100?mesh) sending the underflow to a cleaning circuit (usually spirals) while the overflow is pumped to a secondary cyclone circuit using smaller cyclones. The small cyclones make a cut at near 70 µ (200 mesh) and produce an underflow that is a des limed flotation feed. The overflow is discarded to refuse due to its high ash and superfine size which would produce a high moisture product even if suitably recovered.

Jan 1, 1998

By D. G. Krige

I read the paper “The jackknife approach” with interest. There appears to be a widespread misunderstanding of the kriging variance as a measure of the error variance of the kriged grade estimate of an ore block. Virtually all mineral deposits display skew frequency distributions and are subject to the well-known proportional effect. Thus, it is usual to find in an ore body, when subdivided a really into subpopulations, that the variances of the grades (or the total sills of the variograms) for the subpopulations will be correlated with the corresponding mean grades (usually linearly with the squares of the mean grades). Thus, the variogram will be stationary.

Jan 1, 1996

By Chaitanya "Teny" Mittal

INTRODUCTION A team effort by the Owner, Engineer, and Contractor can help avoid serious problems on a construction project. It can save cost and time for both Owner and Contractor, as illustrated in the following case history of the West Zone and Siouf Keblia Collector System in Alexandria, Egypt (Contract 02-AID-83/84). Under the bilateral agreement made in 1980 between the United States of America and the Arab Republic of Egypt, the United States, through the Agency of International Development (USAID), gives approximately $1 billion per year as a grant to Egypt for various development projects. The Alexandria Wastewater Management System was selected in 1981 as one such project. The Egyptian Government Agency responsible for this work is the Alexandria General Organization for Sanitary Drainage (AGOSD). A joint venture of two U.S. consulting engineering firms, CH2M HILL, Inc., and Metcalf & Eddy, Inc., called Wastewater Consultants Group, along with two local subconsultants, Engineering Consulting Group and Warith Engineering Co., were selected by AGOSD to study the sewer system and develop a plan to serve the immediate and long-range sewage disposal needs of Alexandria. Wastewater Consultants Group is currently involved in Phase I of the Master Plan. This initial step in providing Alexandria with an operating sewerage system for the current and near-term population (year 2000) consists of the design and construction management of 140 kilometers of collector and force main pipelines (including 9 miles of pipe jacking and tunneling in very soft clay), five new pumping stations, extensive rehabilitation of two treatment plants (built in the 1960s but never operated successfully), and installation of a sludge handling system. Phase I is scheduled to be completed by the end of 1991 at a total cost of around $250 million (US) plus 250 million

Jan 1, 1989

By D. M. Hausen

The role of applied mineralogy in mineral beneficiation begins with early prospect evaluation, and continues through stages of amenability testwork and pilot plant studies to the ultimate development of viable processes for mineable orebodies. After plant construction, mineral products from various locations, i.e., grinding circuits, flotation cells, gravity circuits, kilns, smelters, etc., require quick identification and control monitoring for optimum efficiency and recovery. Ore/gangue minerals are identified, quantified, and textural associations investigated by microscopic, spectrographic, and electron-optical instruments. Mineralogic analyses of large numbers of samples have required the development of sophisticated computer systems that merge analytical and mineralogic data into useful diagnostic data bases

Jan 1, 1991

By George Fumich

The Office of Coal Research has been supporting the development of processes for producing synthetic pipeline gas from coal since 1964. .Some of this work has also been jointly supported by the American Gas Association. The work has progressed through laboratory investigation, to bench scale, to pilot plant. It was far from a crash program, generally being fund-limited.. As of one year ago, we had reached the following position: 1. The Institute of Gas Technology HYGAS. process pilot plant in Chicago, Illinois, was in the process of being finally completed. This plant is designed to produce about 1,500,000 cubic feet of pipeline-quality gas per day from 75 tons of coal. 2. The Consolidation Coal Company, CO2 Acceptor Process pilot plant in Rapid City, South Dakota, was well._ on its way to completion. This plant, designed primarily for lignite and subbituminous coals, has about one-half the design capacity of the HYGAS plant. Additionally, the initial construction did not provide for cleanup and methanation; only the preliminary synthesis gas is produced. 3. The Bituminous Coal Research, Inca, BI-GAS pilot plant was in a preliminary design stage. A site had been selected near Homer City, Pennsylvania, to build this plant, planned to consume 120 tons of coal per day. Meanwhile, as you are all well aware, a natural gas shortage was developing in this country. Much has been published about it, so I will not. bother you with further details. Suffice it to say that the reserve-to-production ratio has been steadily declining, because we have been using.-as-faster than we have been find-

Jan 1, 1972

By Aditya Rana, A. K. Mishra, M. M. Singh, N. K. Bhagat

Many cases of derailments, train accidents and traffic interruptions due to the slope failure and rockfall have been reported in the past on Konkan Railway trackline because of unstable rock slopes. The authorities installed stability enhancement measures such as wire netting, rock bolting and shotcreting which were found insufficient. The failed geotechnical measures prompted authorities to excavate the unstable slopes. Rock blasting is generally not preferred for the excavation of slopes along the transportation route. Stabilisation and widening of slopes by blasting need closure of the route for a considerable time. Discontinuing traffic on Konkan Railway route was undesirable as it connects two important port cities Mumbai and Mangalore. The paper presents an innovative directional controlled blasting (DCB) technique for excavating three unstable slopes (i.e. cuttings) in hilly terrain without disturbing the traffic. New empirical formulae for small geometry blasting to estimate burden and throw have been developed. A unique sequence of firing and excavation with powder factor varying between 0.04 and 0.39 kg/m3 irrespective of the actual free face was used for rock blasting. The process controlled the throw of blasted material over the track and resulted in a smooth and stable wall. The slope angle has been changed from 80 to 82° to 45–47° and probability of wedge, planar and toppling failures was eliminated. About 100 such accident-prone slopes (52 km cumulative length, 7% of total route) situated at discrete locations along Konkan Railway route were stabilised using the technique. No incident of rockfall and slope failures along these slopes has been observed after the stabilisation.

By Nikhil Dhawan, Amit Barnwal

The present study reports a processing route to recover metals from integrated circuits of discarded random access memory (RAM) units containing ~ 66% printed circuit boards and ~ 33% integrated circuits. The integrated circuits are manually separated, grounded, classified, and subjected to water fluidization for the effective separation of metals. The significant separation was achieved via water fluidization, and the underflow fraction was magnetically separated. The magnetic fraction was thermally exposed in a muffle furnace, and the process optimization was carried out using a Box-Behnken statistical design. The detailed characterization at subsequent steps significantly aids the understanding of metal-plastic separation and enrichment. A concentrate containing 97% metals (Fe-59%, Ni-9.5%, Cu-7.7%, Sn-13.4%, Pb-5.6%, Ag-1.6%) with 96 wt% recovery can be recovered from discarded IC units. The process pursued is simple, adaptable, and environment-friendly, and the product can be used in conventional smelters.

Jun 23, 2020

By T. Braun

In 1911, a young mining engineer named Bartlett Thane assembled a large claim block, 4 miles southeast of Juneau, Alaska. Across the Gastineau Channel on Douglas Island, the Alaska Treadwell Gold Mining Company had, by 1904, produced gold valued at more than three times the purchase price of Alaska in 1867 (Kelly, 2010). Thane knew his deposit was lower grade than other mines or prospects in the area; however, if the deposit was developed on a large-scale, the trend and size of the deposit made the project potentially economic. In 1911, Thane developed a business plan for the project and successfully attracted investor interest. In 1912, Daniel C Jackling visited the property at the request of an east coast investment group. Upon inspection of 5 years of production records for the Perseverance Mine, Jackling saw an opportunity to apply the low-grade/high volume milling technology which was widely adopted to the copper porphyry deposits of the southwestern U.S. With a design capacity of 6,000 tons per day (5,454 tonnes/day), Jackling’s innovative mill design would require high volume underground mining methods and the power of two new hydroelectric projects. By 1915, the Alaska Gastineau Mining Company was in full production. Between 1915 and 1919, the mine and mill set production records for haulage and throughput. The hydroelectric projects proved to be successful engineering marvels. Operational difficulties related to ore grade, refractory elements and labor shortages interrupted production on an increasing basis. In 1921, the mining company permanently shut down operations. INTRODUCTION The Juneau Gold Belt begins at Windham Bay near the southern end of Stephens Passage and extends approximately 100 miles north to Berners Bay (Figure 1). The first large-scale and sustained underground mine, operated by the Alaska Treadwell Gold Mining Company in the late 1880’s, established the Juneau-Douglas area as the regional hub for transportation and development. In the mid-1890’s, the combined population of Juneau and Douglas reached approximately 3,000 residents, largely driven by employment and support demands of several small to mid-size underground gold mines in the region. By 1904, the value of the cumulative gold production of the Alaska Treadwell was five times greater than the purchase price of Alaska in 1867 (Kelly, 2010). By the turn of the 20th century, economic growth in the Juneau-Douglas area relied on supplies delivered from the lower 48. Passenger and freight shipping lines required 3 to 4 days to make the one-way trip from Seattle to Juneau. Established shipping routes required experienced crews due to navigation hazards and adverse weather conditions. Even with precautions at the time, steam ships and freighter vessels experienced breakdowns or encounters with natural hazards that resulted in damage or in some cases, sinking. Interestingly, with no roads or railroads connecting Juneau to other communities in southeast Alaska, Juneau still relies on seaborn shipping in the 21st century.

Jan 1, 2019

By Lok W. Home

INTRODUCTION Today, raise drilling (boring) has become the stan¬dard method of raising throughout the Western world. It is estimated that the majority of raise footage com¬pleted in 1977 was accomplished by the raise drilling method. Extensive replacement of the drill and shoot system by mechanized raise drilling has occurred be¬cause users have recognized one or more of the follow¬ing advantages. In a direct cost per meter comparison, mechanized raise drilling is economically more attractive than drilling and shooting. Mechanized raise drilling offers improved personnel safety over the drilling and shooting method. Mechanized raise drilling is a faster and more predictable method for excavation than is drilling and shooting. The raise cost per unit of length becomes less as the raise length increases, offering greater flexibility in the overall design of mines. Mechanized raise drilling provides a substantial reduction in labor requirements. 6) Mechanized raise drilling improves the working environment. 7) Mechanized raise drilling improves the rock in¬tegrity of round, unblasted raises. Increasing acceptance of the raise drilling technique is enhanced by continuing equipment development. Today, a wide range of machines and capabilities is available, machine drive systems have been improved, reliability has been increased, and cutter technology is being improved quite rapidly. Table 1 lists the four major manufacturers of raise drilling machines, cutters, and reamers, together with the approximate number of machines that each company had in operation at the end of 1977. Although Reed and Smith are major suppliers of reamers and cutters, they do not manufacture the drilling machines. Four or five other relatively minor suppliers have built machines, reamers, and cutters for raise drilling, but they did not have a substantial num¬ber of machines in the field at the end of 1977. MACHINES FOR MECHANIZED RAISE DRILLING There are three principal arrangements for making machine-bored raises. They include the use of standard raise drills, reversible raise drills, and blind-hole or box¬hole raise drills. Standard Raise Drills The standard raise drilling machine is set up on one mine level or on the surface, and a pilot hole is drilled from that level or surface to a level below. When the pilot hole has been drilled, the raise then is reamed back from the lower level to the upper level or the surface. This arrangement is illustrated in Fig. 1. Reversible Raise Drills The reversible raise drilling machine is set up on a lower level of the mine, and a pilot hole is drilled up¬ward to a higher level. The raise then is reamed back from the upper level to the lower level. This arrange¬ment is illustrated in Fig. 2. The machines used for this type of raise drilling normally are capable of being used as standard raise drills. Blind-Hole or Boxhole Raise Drills The blind-hole or boxhole raise drilling machine is set up on a lower level of the mine, and a full diameter raise is bored to a higher level without the use of a pilot hole. This type of machine is illustrated in Fig. 3. Drill Recommendations If access to upper and lower mine levels is equal, the standard raise drill should be used. The complexity of the equipment and associated handling procedures for boxhole drilling far outweigh any mechanical advantage or reduction in the number of operations, provided that access to an upper level is available. If there is good access to a lower level but only limited access to an upper level, the use of a reversible raise drill should be considered. If there is no access to an upper level, a blind-hole or boxhole raise drill is the only practical mechanized system. MACHINE SELECTION There are six major considerations in selecting a machine for raise drilling. These include operating range, cutter loading, machine structure and main¬tenance, drill string configuration, drive system, and automated controls. Operating Range As shown in Table 2 and Figs. 4 through 6, raise drilling machines are available for a wide range of hole sizes. Standard raise drill ratings range from raises of 0.9 m (3 ft) diam and 120 m (400 ft) length up to raises of 3.5 m (12 ft) diam and 900 m (3000 ft) length. Boxhole raise drilling machines are available for raises ranging from 0.9 m (3 ft) to 2 m (6 ft) diam with lengths up to 90 m (300 ft). Table 2 lists, among other criteria, the torque and thrust of typical machines; torque and thrust are the main criteria for analyzing the capacity of a machine. The raise sizes shown in Table 2 assume a condition of medium hard to hard rock formations and optimum cutter loading. The recommended raise size for a given machine can be exceeded when raising softer rock formations or when the operator is willing to accept a lower level of performance; the performance is related directly to the 1093

Jan 1, 1982

By E. A. Lauha

The Goldstrike Mine is in Eureka County, Nevada, U.S.A., approximately 23 miles northwest of the town of Carlin. The mine is at the north end of the Tuscarora Spur of the Tuscarora Mountains at elevations of 5,300 feet to 5,950 feet. It is part of the Bluestar/Goldstrike sub-district of the Carlin Trend, a northwest alignment of sediment hosted, disseminated gold deposits. The Carlin Trend includes over 15 major gold deposits with production, reserves and geological resources of approximately 65 million ounces of gold (Figure 1). In the Bluestar/Goldstrike sub-district, there are seven major deposits: Betze, Lower Post, Post, Genesis, Bluestar, Purple Vein and Deep Star, plus numerous smaller deposits (Figure 2). Production, reserves and resources for the sub-district are approximately 40 million ounces. Betze and Purple Vein are located on property controlled by Barrick Goldstrike Mines and Bluestar and Genesis on Newmont Gold property. Post, Lower Post and Deep Star occur both on Barrick and Newmont property.

Jan 1, 1993

By Matthew T. Mowry

As the mining industry continues to hire young professionals to supplant the growing number of retirees, a well-developed engineering curriculum, coupled with practical, real-world training, can prepare mining engineering graduates to make meaningful contributions in the industry. Successful companies can be measured not only by their reserve base and annual production but also by their retention of mining engineering graduates with zero to five years of operational experience. My personal experience in the industry during the last five years has been varied and rewarding. The knowledge and experience I have gained have taught me valuable lessons that prepared me for my current role.

Nov 1, 2013

By W. R. Reed, W. J. Archer, A. B. Cecala, J. D. Potts

The U.S. National Institute for Occupational Safety and Health (NIOSH) uses light-scattering real-time dust monitors (nephelometers) in its research to develop dust controls to reduce respirable silica dust overexposures in miners. Recently, the model 1500-pDR, an active nephelometer (i.e., with cyclone and pump configuration), was introduced by Thermo Scientific. Testing was completed to ensure compatibility with the metal/nonmetal mine dust personal sampling unit (M/NMDPSU). Results of testing demonstrated that gravimetric concentrations measured from the 1500-pDR are comparable to the gravimetric concentrations measured using the M/NMDPSU, without need for correction, under commonly observed dust loading conditions.

Jan 1, 2012