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By J. LaForest, R. Riggle

In today’s challenging mining environment, everyone is focused on minimizing cost per ton. With haulage costs approaching up to 45% of the overall mining costs, and loader performance driving production, optimizing payload on the truck is a big opportunity. This paper will focus on technology’s role in loaders achieving the truck target payload. There are constantly new innovations in technology, but not everyone uses them correctly. Technology is intended to help achieve the next level of performance, but still requires the right people and processes to effectively utilize the benefits. In today’s mining business, miners, engineers, trainers, supervisors, and managers have ever increasing roles and responsibilities as never seen before in past decades. Technology can make these roles more efficient, but fully relying on the technology can detract from optimization. Sometimes the old-fashioned method of loading to a consistent pass match will provide a lower cost per ton. Before blindly trusting your technology feedback, know these three areas discussed in this paper: (1) Prerequisites to utilize technology in payload management; (2) Types of payload management technology; (3) How to use the data to manage operator behavior. The objective of this paper is to provide low-cost recommendations to efficiently increase production. INTRODUCTION Whether miners claim to have been around and experienced it all, or they are the data-driven new generation on the mine site, miners are expected to execute the mine plan at the lowest cost possible. So why is it so difficult to execute this task? Shouldn’t supervisors just have to staff the equipment, tell operators to have a safe day and tally up the numbers at the end of the shift? Let the technology system do the rest; what could go wrong? Lots. Having examined numerous mining operations that use the latest loading technologies over the past several years, one common denominator is the opportunity to improve loader operator performance. Mining companies seek help from consultants, training departments, performance reporting systems and an arsenal of resources. Armed with all this information, but the improvements don’t happen, what could have gone wrong? It comes down to people, not managing the resources to drive the right behavior and as a result, the mine’s performance is not where it should be. Understanding how to make “Great Miners” out of these people is critical to this constant struggle to move more with less and get the costs down. Extraction CPT (Cost-Per-Ton) is most sensitive to optimizing loader production which can be generalized into 3 categories of influence: machine specifications, cycle timing, and continuous management using technology. After establishing a basic production machine configuration, utilizing technology to manage cycle times, operator efficiency and payload can be advantageous. Prerequisites to Utilize Payload Management Technology It is important to begin with the primary considerations that enable the use of technology to continuously manage loading productivity. All systems are interdependent in mining, but these are divided into the simplest terms to remember. First, fix your timing and geometry.

Jan 1, 2019

By Ray W. Ballmer

Historically, Bingham is a rail pit, starting with steam locomotives in 1906 and converting to electric locomotives in 1923. Ore production was maintained through an effective utilization of available rail equipment. From time to time as it became necessary to deepen the pit and as stripping ratios increased, various studies were made on alternate material haulage systems. Utilization of diesel locomotives, conveyor belts, and trucks have all been subjects of study, however, conversion from rail haulage utilizing electric locomotives could not be justified. Because of the gradual decline in ore grade, a program was approved in 1963 to raise ore production to 108,000 tons per day. This was designed to return copper production to the 1950 level. Attainment of this production level by expansion of the rail system had definite limitations and built-in inflexibility. Track and trolley wire relocation causes shovel down time in excess of that required for normal maintenance. Instability of the dumps and the resulting additional track maintenance increases greatly as the volume of waste material to be handled daily expands.

Jan 1, 1965

By William Lyman

GENERAL DESCRIPTION Shrinkage or shrinkage stoping refers to any mining method in which broken ore is temporarily retained in the stope to provide a working platform and/or to offer temporary support to the stope walls during active mining. Since ore "swells" when broken, it is necessary to shrink the muck pile a corresponding amount by draw¬ing some of the broken ore out as the stope is advanced-hence the name. Broken ore retained during stoping is drawn out after the stope has reached its limits. The stope may be left empty or may be filled with waste contemporaneous with, or subsequent to, the final draw. Traditionally the method implies conventional overhand stoping methods with miners working between the muck pile and the stope back, in a space which advances updip with mining and is maintained by balanc¬ing "swell" with "shrink." The shrinkage classification is also applicable to so-called "semishrinkage" methods in open pillar-supported stopes where broken ore is temporarily retained as a working platform but offers no wall support; and to various blasthole shrinkage methods which utilize broken ore temporarily retained in the stope for wall support, but which do not require miners to work from muck pile in the stope. The method is generally applied to steeply dipping veins of strong ore between strong walls. APPLICATION Geometry The geometry of a shrinkable vein is described in terms of dip, width, and regularity along dip. Overall strike and dip dimensions and irregularities along the strike generally impose no restrictions on the method. Dip is ideally 1.2 to 1.5 rad (70 to 90°). As dip falls below 1.2 rad (70°), the shrinkage draw begins to strongly favor the hanging wall side, thus leaving a poor working platform for conventional overhand work. This is particularly true in relatively wide stopes. The sup¬port afforded to the hanging wall also diminishes with decreasing dip, reaching nil as the dip approaches the repose angle of broken ore. Dips below 0.78 to 0.87 rad (45 to 50°) are not generally shrinkable except by open stope "seinishrinkage" methods. Minimum mining width is fixed by working space requirements in the stope-generally about 1 m. Shrink¬age in narrower veins requires that waste rock from one or both walls be broken with the ore and the attendant dilution accepted to achieve the minimum width. Nar¬row stopes are less suitable, encouraging hang-ups and bridging of broken ore, with the attendant problems of erratic draw and incomplete recovery of broken ore. Maximum practical width may be 3 m or less to over 30 m, depending upon the competency of the ore and its ability to stand unsupported across the stope back. This is a vital safety consideration in conventional over¬hand stopes, but is much less of a factor in blasthole shrinkage methods. Very wide veins and massive ore bodies have been mined by transverse vertical shrinkage panels separated by transverse vertical pillars which are either abandoned or recovered later by other methods. Regularity along the dip is a prerequisite of shrink¬age as there must be no serious obstruction to the flow of broken ore downward through the stope to the sill level. Gentle rolls along the dip are acceptable if the local footwall dip everywhere exceeds 0.78 to 0.87 rad (45 to 50°). Off-dip hanging wall and/or footwall splits can generally be mined selectively from a conventional shrink stope as they are encountered without ad¬versely affecting subsequent continuation of shrinkage mining updip on the main vein. Vertical offsets or major rolls along the dip which cannot be "smoothed over" generally require that a sublevel be established with new draw control development. Blasthole shrinkage methods are much less flexible (and thus less selective) in their ability to accommodate any of these irregularities. Ground Conditions The wall rock must be strong enough to stand with the minimal support afforded by the dynamic mass of broken ore in the stope. During active mining, local sloughing from the walls is restrained, but the broken ore affords little, if any, useful resistance to closure of the stope walls. Such squeezing, if present, may bind up the stope and cause the loss of much ore. Pillars left between and/or within stopes are effective in preventing closure but reduce overall recovery. Walls may be re¬inforced by bolting after each stope cut in conventional shrinkage but not in blasthole shrinkage. Ore in place must be strong enough to stand with no natural support across the stope width, although tem¬porary artificial support or reinforcement may be used locally in conventional stopes. Some spalling or sloughing is permissible in blasthole shrinkage as men are never present in the stope. Physical and/or mineralogical characteristics of the broken ore may impose restrictions on stope design and/or operational plan¬ning, and may even preclude the use of shrinkage al¬together. Examples include: ores which, when broken, are cohesive or which tend to pack or cement together under the influence of ground water, wall pressure, and/ or chemical reaction. Such conditions precipitate er¬ratic draw during mining and often result in difficult and/or incomplete final draw; pyritic ores which oxidize very rapidly in the stopes and may generate heat, imposing a fire hazard by spontaneous combustion; sulfide ores which oxidize sufficiently in the stopes to adversely affect mill recovery by flotation; and ores (es¬pecially those containing uranium minerals) which ex¬ude radon gas and thereby impose ventilation constraints on stope design. In most cases these problems can be minimized by limiting the size of stopes, by minimizing the duration of mining activity in each stope, and by promptly drawing each stope empty following comple¬tion of mining.

Jan 1, 1982

By A. S. Kastrinos

There are many concepts of preventative maintenance. The basic objective of all maintenance organization, however, is the efficient (accomplishment and control of all) inspection, repair, overhaul, material and preventative maintenance functions necessary to maintain facilities and equipment in a condition that will meet operating requirements at a level consistent with low costs and high availability. To formulate a preventative maintenance program requires sound judgment and the ability to apply in a practical manner a system that meets Plant operation requirements, based upon organization, experience, conditions, design and historical data. A maintenance program must be divided into to categories consisting of: 1. Scheduled tasks to be accomplished at planned intervals. The objective of these tasks is to maintain reliability and prevent as much as possible abnormal failures. 2. Non-scheduled tasks that result from periodic reports and which can be scheduled to fit in conveniently with other routine work. The non-scheduled work items may include long-range preparation for lenghty shutdowns requiring Engineering and Shop services.

Jan 1, 1975

For all the attention given to mining activities in Central and South America, Mexico, Indonesia and Papua New Guinea, it is sometimes easy to forget the activities taking place in one of North America's most important and largely untapped regions -Alaska. The Alaskan minerals industry employed about 3,406 people during 1995. That is a 23% increase from - - 1994. It also contributed about $719.8 million to the state's economy during 1995, a 10% increase. During the past few years, Alaska has seen significant increases in exploration and mining activity. Fairbanks Mining, an arm of Cyprus Amax, began producing gold during 1996 at its Fort Knox Mine, as did Nevada Goldfields' Nixon Fork gold mine. Kennecott's Greens Creek lead-silver-gold mine also reopened and USMX began operations at its Illinois Creek gold mine. In addition, several impressive exploration projects were under way in Alaska. Placer Dome reported good results at Donlin Creek project in southwest Alaska. Likewise, Newmont Exploration is getting serious about its True North gold project. And Nerox is nearing production at its Jonesville coal project in Alaska's interior. In November, about 400 miners gathered in Anchor- age for the Alaska Miners Convention. Throughout the conference and exhibition, attendees listened to updates on these precious- and base-metal and coal exploration and mining operations. They also learned that the state wants more miners to head north and help develop its natural resources. Alaska is ripe for a smelter The mining industry -Alaska's miners in particular - has a powerful ally in Sen. Frank Murkowski (R-AK). He is the chairman of the Senate Energy and Natural Resources Committee. During his luncheon address, Murkowski said it appears that it is economically feasible to extend the Alaska Railroad to northwest Alaska, taking advantage of the large coal and hard-rock mineral tracts in the Ambler mining district. He also renewed his push for building a major smelter in Alaska to process ore that would come from the Ambler mining district. Murkowski believes that Alaska's economy can be expanded by extending the railroad from Nenana to the Point Lay coal fields to open coal development. Along the way, the railroad would pass through the Ambler district, helping to develop the hard-rock deposits. An outgrowth of this additional mineral development, Murkowski said, could be a new smelter in Alaska. It could use power from the Tyee hydroelectric facility near Wrangell or from the Makushin geothermal project near Unalaska. Either site, he added, offers access to plentiful, relatively low-cost power, at tidewater to facilitate ore deliveries to the Pacific Rim. The Congressional Research Service has determined that there are enough mineral deposits and coal beds to make it possible to finance the extended railroad, he said. The 1,200-km (744- mile) rail extension would cost about $4.2 billion. The North Slope of Alaska contains up to 3.6 Tt (4 trillion st) of coal, Murkowski said, that contains less than 0.25% of sulfur and less than 4% moisture. It aver- ages 12,300 Btu in heat content. "That is a tremendous resource," he said. The Ambler mining district, meanwhile, has at least eight identifiable hard-rock deposits, Murkowski continued. These contain zinc, lead, copper, nickel, chromium, tin, barite, gold and silver. "All eight of these can generate ore concentrates at rates similar to Red Dog's cur- rent 725 ktla (800,000 stpy)" of zinc, he said.

Jan 1, 1997

By Nolan B. Aughenbaugh

Zoning and environmental restrictions on land usage now make open- pit quarrying more and more difficult, especially near urban areas. One option for quarry operators is to go underground for mineral production. While underground-mining costs are higher than those for open-cut work, there are several compensating advantages. In many cases it is possible to produce the same material underground without affecting land values, and the surface is preserved for industrial, residential, or agricultural purposes. Proper planning can yield underground sites which have great potential value for industrial plants, warehouses, or other business uses. It is essential to plan underground mineral extraction using a three-dimensional modular-room architectural concept to fully exploit secondary space utilization. Prior to the start of underground mining an operator must make a careful geological engineering study to deter- mine the suitability of the deposit and must prepare a plan for safe and economical mining for the purpose of converting to secondary usage.

Jan 1, 1974

By Ramamritham Sridhar, Vaikuntam I. Lakshmanan, Dan A. Macki

Historically, introducing new technology to the mining industry has been problematic. In general, the industry is reluctant to take risks with new technology because it is already heavily tied to risk, even using existing technology. Risk in the orebody itself can be substantial. The company is dependent on drill hole patterns that are expected to define what is underground, and process test work is often based on drill cores and other samples, which occasionally produce surprises. And even well-proven processing techniques can blindside the producer, resulting in embarrassing and costly difficulties. But if the industry is to grow in knowledge and become more efficient, new ideas must be introduced. How to introduce new technology is the essence of this paper.

Jan 1, 2001

By S. Mason

Many organizations are realizing that continual improvement in health and safety relies on addressing the potential for various forms of human error. Of these, rule violations are often the most frequent form associated with accidents. These occur when an individual (or individuals) deliberately contravenes established and known safety rules. They have been associated with up to 90% of the accidents and other incidents in some industries, and yet they rarely receive the systematic attention they deserve in the promotion of safety. This paper presents underlying motives that cause violations. These can vary significantly from mine to mine and from job to job. Managers need some measure of the attitudes of the violators to determine the underlying motives behind the violations if they are to determine effective strategies for promoting safe behavior. Questionnaires form the starting point to address attitudes and the motives behind rule violations. The choice of the most suitable questionnaire, how- ever, will vary from organization to organization. Guidelines on the choice of questionnaire are offered.

Jan 1, 2000

By Stanley W. Ivosevic, Mark E. Emerson

Introduction Metals exploration activity is moderately intense in the US despite the 1981-82 recession in the mining industry. Although exploration expenditures are significantly less than the 1981 peak, quality and goal orientation of current exploration are high. Major foreign and domestic mining companies as well as nonmetal companies had been attracted to invest in minerals in the US. Its capital markets, political stability, and open-door policy are attractive for hard mineral explo¬ration, particularly in the West. The approach was to either acquire fully or partially developed ore bodies through merger and acquisition, or to fund large scale exploration programs in search of bulk-tonnage deposits. The acquisition avenue has not proved the panacea envisioned for overcoming lack of substantive mineral development. Nor has the decentralized approach to exploration that was adopted proven cost-effective. The emphasis on gold, to the exclusion of all other commodities, raises questions regarding the direction of exploration in the US for the rest of the 1980s. Overview More than 300 companies are active in metals exploration in the US. These range from established, well-known domestic and foreign corporations to hurriedly incorporated, unknown companies financed by having promoted mineral prospects or occurrences of questionable quality. Junior companies tend to be oriented toward property entrepreneurship, rather than the development of minerals resources. These companies have helped maintain mineral lands from prospect to production by holding blocks of property intact during periods of exploration inactivity. This was done through promotional efforts, even though few properties that attracted major venturers proved to have real merit. Exploration objectives of senior and junior exploration companies currently embrace only a few commodities. Arranged in approximate descending order of priority, these are: precious metals; base metals in monometallic or polymetallic deposits; strategic metals, such as tungsten, tantalum, and tin; unconventional commodities, such as diamonds; ferrous metals; and commodities such as beryl, zeolites, and barite. Prospectors are important in searching for these targets. In the US, where they have been financed by major and junior companies, prospectors have proven a useful and low-cost means of locating gold prospects (e.g. the Alligator Ridge property in Nevada). The tenacity and persistence of independent prospectors have been factors in discovering properties rejected or overlooked by professional geologists (e.g. Lornex mine in British Columbia). This has been realized by the provincial government that grubstakes bona fide prospectors. Exploration interest in commodities has always been cyclic with price. Gold is one of the few metals that has experienced a price increase of such magnitude to warrant attention. The potential for realizing adequate operating margins for the Nevada open-pit "no-see-um" gold deposits is great. The present declining gold price, however, may indicate that this emphasis on gold, to the exclusion of other commodities, is shortsighted. Mining companies have been the last to react to price increases, opening new mines based on unrealistic market expectations. A scenario could develop where plummeting gold prices bring recession to the gold industry, as lately occurred in uranium, molybdenum, and copper. US Exploration Climate The US is attractive for exploration due to its strong mineral po-

Jan 4, 1984

By M. Cambridge

The design process must anticipate all construction and operational conditions and make an allowance for all eventualities. Prevention of failure during operational life, and in some cases post abandonment, requires that a risk assessment is undertaken during the design stage which defines not only the factors of safety to be used but the criteria for the structure during its operating life. These operating criteria should clearly identify the at-risk structures and the inspection and monitoring routines required to ensure compliance with the design objectives. On a mine site, it is the role of mine management to ensure that the operating rules be applied throughout the mine life and that a system of inspection and monitoring procedures be instigated. Where the risks are significant, high-level auditing by an independent engineer will also be required. Within the inspection and auditing framework, the designer needs to incorporate instrumentation to enable the operators and management to confirm that the facility meets the requirements of safety, stability and environmental compliance whilst continuing to meet its operational function. This paper reviews the use of inspection and monitoring to prevent failure and provides, in summary, examples of where monitoring has been undertaken and prevented failure. A tabulated review of legislation, regulations and technical guidance generated as a result of previous failures or untoward events is provided.

Jan 1, 2005

By M. J. Klishis

This paper presents the findings of a study on roof bolter's hazard exposure. A "microanalysis" of accident data was combined with ergonomic observations of roof bolter operators to categorize bolting-related injuries, and, from this, a checklist was constructed. Bolting-related problems were identified as situations that could expose bolter operators to hazards. Approaches to avoid these situations were applied at six mining operations to evaluate specific problems in root bolting operations. The research emphasized the importance of analyzing worker behaviors in the context of mining situations and equipment-design problems that lead to human-error accidents.

Jan 1, 1996

By Hal McVey

Introduction The role of marketing in the minerals and mining industry takes on different degrees of importance depending on the commodity, but nowhere are sales and marketing more important than in industrial minerals. This article compares industrial minerals marketing with the marketing of other mining and mineral products. Marketing in Mining Some broad generalizations on the marketing of industrial minerals in relation to other mineral products can be made without getting bogged down with exceptions to generalizations. Two totally different areas of mineral production are crude oil and natural gas, and metals, including ores and concentrates. Although these commodities are the basis for two completely different industries, they share two things in common from a marketing standpoint: • Their value per unit volume is usually high enough so that they can be transported great distances. • Their specifications are readily definable and, therefore, the quality of a standard product from a production run can be communicated by stating certain chemical and physical features. This permits sales to be consummated by telephone, telex, and letter, without the need to pretest the products under use conditions. In regard to the first item, industrial minerals, as opposed to oil, gas, and metals, are in most instances site specific. Location of the point of production in relation to the point of use is of paramount importance based on a generally lower unit to volume value. This means that transportation is a major factor, with the cost of getting the mineral to market commonly exceeding its f.o.b. value. Coal marketing has many characteristics in common with industrial minerals. Coal sales can es-

Jan 11, 1983

By Peter J. Conroy

Introduction Most subsidence monitoring to date has been surface monitoring to develop empirical relationships of the magnitude and extent of subsidence effects. Federal regulations are forcing a better understanding of subsidence. Empirical methods of subsidence prediction may not be adequate, since the empirical relationships may not be valid between or even within coal fields. A better understanding of the mechanics of subsidence is required in order to develop and verify analytical models. This paper presents some of the results of surface and underground monitoring in longwall faces of a coal mine. The seam thickness in these mines ranges from 5 feet to 6 feet at depths of 600 to 1100 feet.

Jan 1, 1982

By James W. Martin, Brad H. Droegmiller

As construction projects continue to get larger, greater demands are placed on systems to provide higher production rates at reasonable costs. This paper shows the application of dozer-trap loading versus other methods of moving bulk materials. Most conventional methods employ multiple types of heavy equipment to accomplish a single task. Trap loaders fed by dozers and discharging onto overland conveyors offer an alternative/economical means of high volume bulk material movement. This paper will discuss the process of trap loading to overland conveyors.

Jan 1, 1998

By James W. Babcock

Introduction Geologic ore deposit models are key to any exploration program. In the search for ore deposits, the geologist first tries to understand the genesis of known ore bodies. During reconnaissance and evaluation of a prospect, a valid exploration model of a known ore body can help the explorationist focus on critical geologic attributes of the target area. Exploration models can conserve exploration funds that might otherwise be spent collecting data not critical to delineating an ore body. This article examines the benefits of using models, factors to be considered in developing models, and examples of the way recent models have evolved. New exploration concepts and techniques are developed in response to increased competition in the mining industry. New techniques can give an exploration group a slight edge that may translate into a discovery. Mine geology staffs may find previously unlooked for extensions to the ore body by applying new genetic concepts. When all appropriate techniques are applied to exploration and mining efforts, greater efficiency and increased profits may result. Before the 1950s, scientists speculated on the genesis of ore deposits and other natural phenomena. But they presented their results as if universal and final, even though they applied to only a few deposits. Because it did not provide sufficient criteria to distinguish the genetic processes, the classic conflict between hydrothermalists, epitomized by Lindgren, and nonhydrothermalists did not help the minerals explorationist much. Important information about individual ore deposits, such as age of the host rocks and mineralization, composition of the mineralizing fluids, and separation of mineralizing and nonmineralizing events in the paragenetic sequence, could not be gathered with past equipment and methods. But these early concepts of ore genesis contained excellent empirical observations, perhaps the most useful parts of these hypotheses. Through the years, prospectors have found most of the ore deposits in the world using direct observations and their collective empirical wisdom - an empirical model. The geologist's contribution becomes increasingly important after the more obvious surficial ore deposits have been discovered. In Europe and North America that time has arrived. With the introduction of sophisticated equipment and matching techniques in the 1950s in geochronology, geochemistry, geophysics, remote sensing, and computers, many previously equivocal genetic questions can be resolved. This proliferation of highly technical data has allowed the construction of many well-founded genetic models.

Jan 12, 1984

By C. D. Mann

INTRODUCTION The sublevel stoping mining method is usually applied to a relatively steeply dipping, competent ore body, surrounded by competent wall rock. Ore is produced by drilling and blasting longholes, which can range from 50 mm (2 in.) to 200 mm (7% in.) diam, with lengths up to 90 m (300 ft). Longholes can be inclined in any direction, but the ring or pattern usually forms a plane, and the holes are blasted as a unit. Recently developed mobile drilling and loading machinery, as well as new explosives products, blasting techniques, and cemented sand and rock fill have made sublevel stoping a highly efficient and versatile mining method. When designing a sublevel stoping production sys- tem, it should be kept in mind that production rates from conventional sublevel stopes vary widely through- out the life of the stope. Early production is at a low rate, coming only from the drawpoints near the slot, but increases as new drawpoints are reached by the stope face. As the stope nears completion, again, fewer drawpoints are productive. Enough drawpoints must be available at any time to provide required production. Drawpoint availability should be compared to equipment availability; plan for more drawpoints than are needed at any one time. Accurate, realistic scheduling is essential to smooth production rates. Also, initial recovery of ore in a stope/pillar block is normally from 35% to 50% in sublevel stoping. Planning of pillar recovery, representing the majority of ore tonnage in a production block, must be done during early mine planning. Since much of the development already done for primary stoping (access for drilling, drawpoints, and haulageways), can be used for pillar recovery, early production from pillars is highly desirable. The following description of components of the system is an attempt to highlight some of the most important features and requirements of mechanized sublevel stoping methods. Similar comments would apply to the use of older equipment (column-and-arm drill setups, slushers, etc.) in similar methods. As in any good mining system, maximum economic recovery of the resource in the ground is the primary consideration. STOPE DESIGN CHARACTERISTICS Length and Width The following are some of the factors which affect sublevel open stope length and width dimensions: ore body geometry, principal stress directions, competence of stope back, optimum drill pattern, and drilling drift layout. In new mines initial stope layout design may occur before the ore body is actually intersected by mine workings. Stope dimensioning is a critical decision, and assistance from as many knowledgeable people as possible at this stage is essential. Operators with past experience in similar ore bodies, rock mechanics experts, and others with mine design experience should participate at this stage of stope planning. Height The following are some of the factors which must be considered in determining stope height: competence of stope pillar and stope/fill walls; slenderness ratio of adjacent pillars; ore body dip; ore body thickness; hole depth capability of the drilling machine; fragmentation characteristics of the ore; and level intervals in existing mines. In competent ground, drill-hole length and accuracy are the most important determinants of stoping height. Frequently entire drilling sublevels can be eliminated because of the depth capability of sophisticated drilling equipment, resulting in significant development cost savings. Drawpoint Location and Design Some of the most important considerations of a good drawpoint system are optimum spacing of draw- points, within the constraints of stope dimensions, for uniform drawdown and maximum recovery; excavations designed for stability for the life of the ore block to be drawn-primary stope ore as well as subsequent pillar ore; floor or roadway design including type of surface, reinforcing, grade for water runoff; orientation with respect to the main haulageway, for optimum loader maneuverability and ground stability at the inter- section; and length, to allow articulated front-end loaders to work in a straight configuration. Careful drawpoint design and construction are keys to successful production. Extra care in development, such as smooth wall blasting, rockbolts or grouted rebar, wire mesh, and shotcrete usually will ensure long draw- point life. Human exposure during production loading is of longer duration than during development or production drilling, and consequently preparation of draw- points is easily justified, particularly when pillar ore can be drawn through the same drawpoints. Secondary blasting of boulders can weaken drawpoints, also justifying good ground control techniques. A smooth draw- point floor of poured, reinforced concrete, on a grade of +3% or +4% toward the ore pile facilitates water flow out of the drawpoint, and ease of loader bucket penetration into the muck pile. Slot Raising, Slotting A slot or other space for rock expansion is necessary in conventional sublevel stoping where vertical rings or rows of holes are blasted. The slot can be started at a slot raise driven by conventional raising methods, raise boring, drop raising (predrilling and blasting a raise from the top, using small diameter-less than 200-mm (7%-in.)-holes for relief), or crater blasting (similar to drop raising, but without relief holes). The slot usually extends from the extraction level to the back of the stope. It is normally expanded to full stope width by

Jan 1, 1982

By Paul D. Tomlingson

Will Rogers unwittingly commented on the essence of evaluations when he said: "We don't know what they don't know!" In so doing, he explained why managers have an obligation to verify that their personnel really know what is expected of them. Rogers further stated that "What we know may not be so!" Here, he suggests that managers must establish the correctness of facts on which they make decisions concerning the future of their organizations. Yet, there are some managers who may not have considered this basic wisdom. These are perhaps the ones who shun a solid, fact-finding evaluation. Instead, they trust to guesswork as a basis for attempting improvement. Without realizing it, they may be making incorrect decisions harmful to the very organization they are trying to improve. Unfortunately, an attitude of avoiding evaluations often permeates whole organizations when their managers fail to appreciate their importance. Recently, the following was found prominently displayed in the office of a maintenance manager. Regrettably, the facts of a subsequent evaluation established how imprudent his attitude was:

Jan 1, 1991

By Jack S. McPartland, Gene E. McClelland

It is advisable, for any heap leach project, to develop an historical metallurgical data base to predict production heap performance before ore is mined and placed onto the heap. A data base would include results from: interval assays, cyanide solubility tests, and bottle roll tests on exploration drill cuttings samples; and those results plus column leach test data on diamond drill core or bulk ore composites. Subsequent larger scale heap leach test data can then be compared to the historical data base, to blast hole composite data during mining, and eventually to production data. This paper does not discuss metallurgical comparisons between assays, cyanide solubility tests, and bottle roll tests on exploration drill cuttings samples, but does discuss metallurgical comparisons from bottle roll tests, laboratory scale column leach tests, and pilot scale heap leach tests on core and bulk ore samples with operating data for three U.S. commercially producing heap leach operations. Provided that representative core or bulk samples are used for evaluation, heap leach test results accurately predict or understate the success of the commercial operation and remove most of the uncertainty from the investment decision.

Jan 1, 1990

By Thomas G. Hayes

Track-type tractors remain one of the most cost-efficient stripping tools available to coal miners. Whether they are "sweetening up" a dragline operation with prebenching or serving as the primary tool, dozers are important in driving down mining costs. This article reviews the application zone of track-type dozers. It also provides suggestions for site setup, equipping tractors and machine operation. In recent years, the track-type tractor has become more of a production tool in mining. With the advent of bigger machines, bulldozers have become a typical component in mining operations, removing overburden down to the top seam of coal. Large tractors can also be teamed up with draglines and other systems to maximize the effectiveness of the mining system. Bulldozers remain the tool of choice for topsoil removal, spoil reclamation or any application that demands low ground pressure, or short distance. The introduction of the 523-kW (700-hp) track-type tractor to the mining industry has made the bulldozer a low-cost-per-ton means of removing overburden. The large tractors offer enough productive capability to be considered prime stripping tools. And they can lower mining costs by complementing other mining systems (dragline, cast blasting and loader/truck). Four criteria determine whether a track-type tractor is the right machine for a particular application: ? Production requirements - dozer may fit job requirements better than a second dragline. [ ] ? Product support - availability of parts, service and technical expertise. ? Labor situation - how much of the cost per ton goes to the operator. ? Resale opportunity - recover a percentage of capital cost. Mining efficiency is economically controlling the cost of any system. Most operations rate the most economical means of moving material as cast blasting, dragline and the track-type tractor. All three of these systems share one common value: They are all sensitive to distance. Regardless of the application, all mining systems have an economic range. Exceeding this distance will affect cost and productivity.

Jan 1, 1997

By Michael M. Donahue

"The public interest -- as opposed to the narrow interests of particular shippers -- will also benefit from the establishment of adequate revenue levels and the revitalization of the railroads. And this is particularly true with respect to the transportation of coal. "

Jan 1, 1981