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By William A. Ribich, Hans A. Hug

INTRODUCTION Providing sufficient thrust, particularly in the proper manner, is one of the major problems of conventional hardrock drilling and tunneling machines. For instance, with tunnel boring machines, massive jacks, mechanisms, and structures are required to generate and transmit the forces to the cutting head. One pays for this massiveness both in terms of material (dollars per pound) and in the attendant difficulties of transporting and maneuvering such machinery. The effect of an efficient thrust generation method on system size is evident when one considers conventional shaft drilling equipment. Raise borers are small enough to be used underground, while conventional big hole drilling equipment requires large amounts of space, personnel, and support. Proper application of the force is another problem, even with smaller holes such as blastholes. While one can load most tricone blasthole bits to their limit with such drill rigs as the Bucyrus Erie 61R or the Gardner Denver 120D, transmitting very large forces through the relatively flexible mast and drill pipe leads to large vibrations, fatiguing of the mast structure, and impact loads on the bit. In the following, a new method of generating the required rock fragmentation force is presented. Furthermore, the force is generated and applied in such a fashion that not only can the equipment size and weight be reduced, but also the cutter and equipment life can be increased.

Jan 1, 1974

By Bruce W. Cavender

During the last few years, the minerals industry has been confronted by increasingly stringent environmental regulations that are significantly altering the economics of the industry. Heightened media attention, threats of litigation and decreasing support by the general public have exacerbated the industry's difficulties. Regardless of their merit, environmental issues present a serious threat to the continued viability of mining companies. Firms have reacted to these regulations by escalating their environmental activities to meet the new requirements. They have simultaneously adjusted their corporate schedules to reflect the substantially longer time periods required to obtain construction and operating permits and ensure compliance with legal requirements before mine abandonment. Companies have also been forced to adapt to a considerably greater amount of uncertainty and expense associated with the development of mineral projects. This has resulted in a significant erosion of the profitability of some mining companies. Most of the changes in corporate environmental activities have been reactive. Pending regulations present formidable but uncertain technical requirements for compliance, and future regulatory developments are difficult to predict. This problem is aggravated by depressed market prices for many mineral commodities. Past expansions of environmental standards have led to the closure of mines and processing facilities due to economic hardship, as occurred in the smelting segment of the US copper industry in the 1980s (Cro¬zier, 1992).

Jan 1, 1994

By Jamai Rostami

Mining, perhaps more than other industries, has been under pressure to achieve higher productivity, while reducing costs and environmental impacts. This has encouraged a move toward large-scale operations and greater integration and automation of systems. Mechanization is being used increasingly to raise production and reduce labor requirements. Yet, while transportation, ventilation and other activities have benefited from this trend, mechanization of rock excavation (for development and production) has lagged. The switch to a mechanized excavation system can be complex, requiring a thorough study of operational and cost benefits to be successful. To justify the high capital cost of mechanical mining equipment, production rates and the true costs of machine mining must be accurately estimated. To evaluate the cost effectiveness of mechanical mining for a particular operation, the total production cost (capital and operating) must first be estimated. This requires a reliable estimate of the production rate of the candidate mechanical excavator. Previously, the variable nature of rock caused performance prediction of these machines to be more an art than a science. Additionally, some of these machines are highly sensitive to operator skill. They all depend on their backup systems. The effects of interaction with the overall mining operation can be difficult to forecast. And a new system must surmount psychological barriers before it can become truly operational.

Jan 1, 1994

By Gary W. Hausler

Bergbau AG Niederrhein, a subsidiary of Ruhrkohle AG; Essen, Germany, is working coal mines on both sides of the Rhine River. The Prosper Mine in the City of Bottrop has a production of about 13,000 tons per day and has been in operation since the turn of the century. Mining has moved to the north as coal deposits south of Bottrop are exhausted. To facilitate ventilation, material handling, and transportation new shafts are being constructed in the northern coal fields. The Prosper 10 shaft is being sunk to develop the Prosper - Haniel coal field which has reserves of 280 million tons. In October, 1976 Bergbau AG Niederrhein awarded the shaft sinking contract for the 1047 m deep, 8 m inside diameter Prosper 10 shaft to Gewerkschaft Walter; Essen, Germany. Construction costs will amount to about 40 million DM with construction completion scheduled for 1981. GEOLOGY The shaft, located near the town of Kirchhellen north Bottrop, is being sunk in the Grafenwalder Horst between two faults on the south west flank of the Kirchheller Anticline. 270 m of upper cretaceus sands and marls overlay sandstone bedrock at the shaft location. The upper 124 m of this section contain highly saturated sands interspersed with marl. In order to successfully sink the shaft through this section, ground stabilization by freezing was used.

Jan 1, 1979

By B. K. Mishra, R. K. Rajamani, P. Songfack

Primary grinding in SAG mills is gaining more importance with respect to the conventional crushing, rod and ball milling operations. This is due to the reduced operating costs generated by lower steel consumption. However. SAG milling is inherently susceptible to more severe risks and problems since it attempts to combine several stages of the conventional crushing and grinding into a single stage. This paper analyzes the SAG milling operation by predicting the motion of rocks and steel balls. The well-known discrete element method (DEM) is used to calculate the trajectories of individual entities, and their collision with one another. A computer code previously used for studying the motion of grinding media in ball mills is enhanced to handle the interaction between heavy spherical steel balls and light chunks of rocks, usually ellipsoidal in shape. The DEM based software called MILLSOFT can animate the charge motion for different design of liners. A case study of a 9.75-m diameter SAG mill is presented and the effects of lifter bar height and configuration on the overall dynamics of the charge are discussed. Also the effect of spacing between liners on lifting the charge is presented. This new approach has a large potential because it shows in detail the effect of each design or operating parameter on the performance of SAG mills.

Jan 1, 1998

By Peter Fordham

A Norbridge review of 25 top mining companies highlighted financial problems for many firms. To better understand these results, Norbridge benchmarked 17 mining companies to understand the problems that companies face, the methods being used to improve performance, and the results that have been achieved. The study indicates that many mining companies in three sectors-coal metals, and non- metallic minerals-have implemented new strategies to improve performance. Many of these strategies supplement traditional initiatives with two types of process improvement efforts, facility-specific and company-wide, to help generate performance gains. The study compares the results of these strategies in each sector. INTRODUCTION imes are tough in the mining industry. Norbridge reviewed financial results of 25 top mining companies for the past 2 years-seven coal companies, twelve metals companies, and six non-metallic minerals firms.*The study found that 40% lost money in 2002, and * Coal companies include Alliance Resource Partners, Arch Coal, Consol Energy, Massey Energy, North American Coal, Peabody Energy and Westmoreland. Metals producers include Barrick Gold, Cleveland-Cliffs, Coeur d'Alene, Falconbridge, Freeport McMoran, Grupo Mexico, Inco, Newmont Mining, Noranda, Phelps Dodge, Placer Dome, and Teck Corninco. Non-metallic firms include Florida Rock, IMC Global, Martin Marietta Materials, Oglebay Norton, PotashCorp and Vulcan Materials. Information is from public sources, e.g., annual reports, company Web sites.

Jan 1, 2004

By Gerhard Sauer, Heimo Gold

The main advantage of the New Austrian Tunneling Method over conventional drill and blast techniques, TBMs and shields is its outstanding flexibility. Many different support concepts help to cope with all but the most adverse conditions. A considerable variety of unique additional support measurements provide a functional tool when dealing with particularly difficult conditions or restricting requirements. The resulting adaptability of NATM with respect to geometric and geologic changes is a cornerstone to providing an economic design and to a safe and unhindered execution of the tunnel work. To take best advantage of this flexibility and to emphasize its cost-saving capacity, NATM explicitly extends the design period into the construction phase. In accordance with corresponding ground classes or other anticipated conditions, a number of basic support categories and an array of additional support measurements are established during the actual design phase. The decision for applying a particular support category at a specific location and for necessary additions to the given support scheme, however, is regularly made on site after each advance, and is determined by the key persons involved in the construction. Contract documents must reflect this approach to facilitate the execution of the work and to curtail construction costs. Biased distributions of risks, however, can adversely effect the envisioned benefits. Consequently, the respective responsibilities of engineer, contractor, and client need to be redefined.

Jan 1, 1989

By B. K. Parekh

The International Symposium on Comminution was organized at Camborne School of Mines, Cornwall England. Papers covered the fundamental and practical aspects of comminution in the mineral industry. Although comminution equipment design has not changed fundamentally during the last 50 years, methods of control and optimization have improved considerably. A simulation model for batch ball milling in the rotating mill was developed as a step toward continuous simulation of ball and autogenous milling. New concepts in jaw crusher technology design and the concept of a 1.6- x 2.1-m (66- x 84- in) jaw crusher with open feed throat has resulted in power savings. The use of cone crusher technology in comminution circuits with particular reference to machine design, plant flowsheet and control figuration has been reported by Boliden Allis, of Sweden. The Whiten steady state crusher model form has been used to develop a quantitative model of 2.1-m (7-ft) cone crushers. This was done by incorporating liner age (wear) and liner length as variables on the selection of particles for breakage and thus on the product size distribution. Another paper by Lira and Karetsky discussed the development of a model based on a multisegment ball mill developed by Whiten and Kavetsky. It is capable of simulating the performance of a coarse grinding ball mill of a given diameter, ball size and mill speed.

Jan 1, 1991

Two years ago, about the only US mining ventures that could turn even marginal profits were precious metals. In 1986, the price of gold dramatically increased, as did earnings from precious metals, mostly gold mines. First quarter results for 1987 show that gold will again be the most profitable type of mining in the US. All this money being made in gold resulted in many new mines being opened and hundreds of old workings being re-evaluated. The Society of Mining Engineers has put together a technical program to aid in developing precious metals mines. Small Mines Development in Precious Metals will take place Aug. 30-Sept. 2, 1987 at Bally's Hotel, Reno, NV. For registration and hotel information see page 426 or contact Meetings Department, SME, P.O. Box 625002, Littleton, CO 80162-5002, 303-973-9550. Topics at this meeting will include Problems Facing Small Miners; Understanding Geology and Ore Reserves; Mining-Production Options to Maintain Competitiveness; Processing for Precious Metals; Financing and Economics that Work for Small Miners; and Understanding the Environmental and Permit Maze. Problems facing the small miner The small miner has found and started most of the productive mines in the world, says Alfred G. Hoyl, of Coal Fuels Corp., Rollinsville, CO. Hoyl will state his case for small mines development in the opening session of the program. He will make the point that government regulations must never restrict the small mine or miner. And the mining industry must be careful not to crowd out the independent miner. "To restrict small mining is to say to our young men and women entering the mineral industry `There is no place for you as an independent.' Small is a relative term and we must never feel that starting small will restrict our possibilities of becoming big." In the same session, David J. Starbuck, Starbuck Minerals Management, Mayer, AZ will take a look at why smaller precious metals mines are profitable. Mining companies have changed their perspective on reworking previously mined properties. They are looking at abandoned properties in older mining districts. The attitude is that smaller operations in these districts can be profitable with the present economic climate, more advanced technology, and better management. Small, independent mining companies may not have the same resources to draw from as the majors. But there are affordable technologies available that fit into the independents' budget. Betty Gibbs, of Gibbs Associates, Boulder, Co will explain how a personal computer can help a small operation to analyze data more effectively and respond quickly to changing conditions. Scenarios will be developed that will describe how PCs can be incorporated into all phases of an operation. Financial institutions are becoming more willing to consider venture capital for small precious metals mines, according to Stanley Dempsey, Denver Mining Finance Co., Denver, CO. This may be in the form of equity or debt, he says, but they want to receive assurances of the quality of the resource. And they will ask about the ore reserves. Next, the potential lender will want to know about the mining method and en¬vironmental regulations. Dempsey will discuss these requirements. Once a high grade gold mineralization is located and reserves proven, it must be evaluated to determine which recovery process is best suited for this deposit. Robert Martinez, Amselco Minerals, Ely, NV will evaluate processes for such a deposit located in Mexico. Heap leaching, vat leaching, and a carbon-in-pulp circuit are all viable options, he says. He will explain which recovery process proved to be the most economic. Other papers in the introductory session include How to Best Use Consulting Firms to Accelerate the Development Process, by H. Schreiber and R.P. Fronk, both of Behre Dolbear-Riverside, New York, NY. And W. Mayrsohn of Asamera Minerals, Denver, CO will present Marketing Fundamentals that Work for Small Mines. Understanding geology and ore reserves In the current scheme of fast-track exploration and mine development, insufficient time and thought is given to understanding the geology of a deposit as it relates to controls of mineralization and subsequent mine development, say D.S. Bolin and J.W. Rozelle, of Pincock, Allen & Holt,

Jan 6, 1987

By Ted T. Biddle

The world energy crisis has created a greatly expanded exploration program for energy fuels. The demand for materials required for drilling operations such as barite, which is the primary component of drilling fluids, has increased proportionally. As in the case of many other minerals, existing high grade barite mines are no longer capable of producing the required tonnage. Consequently, exploration and development of lower grade ore bodies has been increased. The need to produce a high quality product at maximum recovery rates, along with the ever changing economics affecting both selling price and production costs has triggered accelerated research programs toward more sophisticated and efficient beneficiation methods. Taking into account the specific gravity differential between barite (4.5) and the normal gangue minerals such as silica and calcite (2.7), gravity concentration methods are the prime consideration with flotation as a scavenging process. Greater emphasis on particle size liberation, size reduction and concentration is also indicated. In order to accomplish these objectives, it has been necessary to revert back to the old adage, "Recover your minerals as soon as they are free."

Jan 1, 1980

By A. L. Hannaford

Previous production at Spektakel was undertaken during the periods 1854 - 1888 and 1892 - 1901. During this period a total of 41,7 kt of ore grading 32% Cu was hand-sorted from 270 kt to 360 kt of ore mined. Initial open-pit mining was followed by underground mining, access being by means of an inclined shaft to the 85 fathom level. During the period 1946 - 1952 cement copper equivalent to 5,452 kt of blister was produced by leaching of oxidized ore. The Spektakel ore-body branches and coalesces both in plan and in cross-section which accounts for its remarkably complex configuration. Constituent rock-types are andesenite and various varieties of biotite diorite and of ?norite? (biotite-hypersthene diorite). Closely related spatially, and possibly genetically, but predating the above-mentioned basic rocks are bodies of biotite-bearing monzoritic rocks, locally termed shonkinita.

Jan 1, 1981

The United States is being invaded... by foreign capital: marks, francs, pounds, yen, lire, riyals, you name it: On almost any given day the Wall Street Journal will contain a new report on a department store, newspaper, bank, hotel, agricultural land, supermarket chain, et a1 being bought into by overseas investment. Xenophobic reaction to this revised national condition has begun to set in. Several farming states have and are introducing legislation to monitor foreign land buying. In Congress a mandatory reporting requirement for foreign purchasing is currently under study. In a relatively short period the country has reverted from world leader- ship in overseas acquisition and involvement to become itself one of the prime investment opportunities in existence. Interestingly enough, one of the industries where this changed status has become most apparent and pronounced is within that small/regional/segmented/low value-to-weight bulk commodity enterprise ranked as the backbone of the nation's construction activity. U.S. cement making is not only undergoing internationalization in its ownership, but also in its product, equipment, and engineering expertise.

Jan 1, 1979

By Reed J. Irvine

One normally does not find sudden and dramatic changes in the investment climate, barring the unexpected outbreak of-wars or revolutions. Asia has seen a fair amount of military action and revolt during the past year, not all of it unexpected There was the fighting in Laos, which resulted in the as yet unconcluded negotiations which will probably lead to the establishment of a neutralist regime. In April of 1961 another revolution occurred in South Korea, and the elected government was replaced by a military dictatorship.. Communist guerrilla activity in South Vietnam was stepped up, and uncertainty about the future of that area increased. Relations between Pakistan and Afghanistan became more strained, and while no fighting has broken out, diplomatic relations between the two countries were broken off. India was both the victim of further incursions of her territory by communist China and the perpetrator of the forcible seizure of territory from Portugal. Indonesia has been making preparations for an armed attack on the Dutch in New Guinea.

Jan 1, 1962

By H. G. Fleshman

?Wyoming bentonite? has become almost a world-wide trade mark for high quality sodium bentonite. Although bentonite is produced in more than a dozen U.S. states the largest producing area covers Wyoming and adjacent parts of Montana and South Dakota. Bentonite was originally known as Taylorite and later renamed Bentonite by Dr. Sam Knight, the State Geologist of Wyoming. The new name came from the Fort Benton shale member of the Mowry Formation. Bentonite is a clay consisting essentially of the montmorillonite group of minerals. Since bentonite has good ion exchange capabilities, various cat-ions are easily replaced. These cations are usually calcium and sodium; however, magnesium, lithium, potassium, and others can be exchanged. One way of classifying the clay is based on its swelling capacities when wet or added to water. Bentonite having sodium as the dominant exchangeable ion typically has very high swelling capacities and forms gel-like masses when added to water. Bentonite in which exchangeable calcium is more abundant than other ions has much lower swelling properties than sodium varieties.

Jan 1, 1987

By C. J. Hunter

Prior to the commissioning of the Sansu Sulphide Treatment Plant (STP), Ashanti Goldfields' treatment facilities were capable of producing some 700 000 ounces of gold per annum. Ore sources were underground refractory sulphides, surface oxides and old tailings dams. In order to increase the mines production to 1 million ounces per annum and to accommodate the change in ore sources as surface mining moved into fresh sulphides, a part of the strategy adopted was -the construction of a new sulphide treatment plant with a capacity to mill 2.2 million tonnes per annum and produce 400 000 ounces of gold. The STP has been designed, built and commissioned. and has been in operation since February 1994. The Plant boasts the world's largest Bio-oxidation facility which is capable of treating 790 tonnes of sulphide concentrate per day at a grade of 11.4% sulphur and is currently undergoing an expansion to increase its capacity to 1050 tonnes per day. The following sections describe the reasons for selecting the BioX® Process, the plant design, the commissioning experience and the plant performance to date.

Jan 1, 1996

By E. R. Hendrickson

About 1/3 of the world's supply of phosphate rock is produced in a relatively small area of the Florida peninsula east of Tampa. Until this past year, a circle with a radius of about 25 miles and centered on Bartow would encompass the major producing areas. During the past year producing areas have opened in North Florida which promise to vie with the Polk-Hillsborough County area in terms of proven reserves. In addition, new phosphate production is planned for counties to the south and west of the present fields. From the existing production areas, however, more than 19 million long tons of phosphate were mined in 1965. As mining engineers most of you probably are familiar with the methods of mining and beneficiating the pebble phosphate rock. You thus recognize that, although some water quality problems may arise from these processes, there is no potential air pollution problem. To make an economically useful product, however, further processing must take place. It is from this additional processing that potentially damaging materials may be discharged to the atmosphere.

Jan 1, 1966

By M. F. Vancas

The San Manuel oxide ore reserve ranges in depth from being exposed on the surface to lying 1000 ft. beneath a conglomerate layer all of which is confined in the subsidence zone of an active sulfide block caving operation. Present day recovery of the oxide copper values is either by open pit mining-dump leaching, or in-situ leaching of the oxide ore using dilute sulfuric acid solutions and solvent extraction/electrowinning processing of the pregnant leach solutions. Future plans are for continuation of leaching with expansion of reserves and increased processing rates. The state of the mining industry and copper in particular has not been good for a number of years. All of the producers that are still operating have made major adjustments in order to remain competitive. Magma Copper Co. is no exception.

Jan 1, 1987

By L. R. Hossner

Chemical and physical properties of surface soils and overburden materials must be evaluated prior to strip mining activities. This information can be used to assess whether subsurface overburden can be equal in quality to the existing surface soils, especially when these soils are classed as prime farm lands. In Texas, materials from the Carrizo, Calvert Bluff, Simsboro, and Hooper Formations overlie the lignite. The Carrizo Formation consists of thick clean sands with poor water and nutrient retention capabilities. These materials are least suited for placement of the surface of reclaimed land. The oxidized, medium textured overburden from the Calvert Bluff and Simsboro Formations possess adequate water and nutrient properties and are better suited for sustained plant growth. Non-oxidized Calvert Bluff and Hooper sediments generally have acceptable properties for reclamation. However, caution must be exercised in vegetating these materials since they may contain acid forming sulfide minerals.

Jan 1, 1982

By J. M. Ekenes, C. A. Caro

"New approaches that increase hydrometallurgical recovery from refractory minerals in below mill cutoff -grade sulfide copper ore can add significant value, improve profitability and increase ore reserves. This paper describes the development and implementation of an engineered heap (EH) approach to leaching low-grade, chalcopyritebearing ore at Freeport-McMoRan’s mine in Morenci, AZ. The technical evolution of the engineered heap concept is described together with the challenges and benefits following implementation. Introduction The Morenci ore deposit, located in eastern Arizona, has been mined for copper for 140 years. Mineralization in the Morenci district consists of sulfides and oxides. To process these ores, Morenci operates concentrator and leaching circuits. Leaching accounts for two-thirds of the copper produced in Morenci. More than one-half of this leaching-derived copper production comes from run-of-mine (ROM) stockpiles. The largest category of material moved in Morenci is destined for ROM stockpiles and waste dumps. Materials that are not economic to mill or leach are designated “waste.” However, this designation can change based on improvements in extraction technology and commodity prices. Chalcopyrite does not leach well due to its refractory nature. For predominant chalcopyrite mineralized ore, copper recovery during a typical leaching cycle may be as low as 5%. For this reason, chalcopyritedominant ores below mill cutoff grade have historically been classified as waste. By incorporating advanced leaching technology to improve metal recovery from previously leach-resistant ore types such as chalcopyrite, the Morenci Mine has been able to reclassify substantial amounts of this “waste” to “ore.” Process chemistry Chalcopyrite copper extraction is temperature, oxygen and ferric dependent. The temperature is achieved primarily by pyrite oxidation (Eq. (1)) and secondarily by oxidation of chalcopyrite itself (Eq. (2)). The regeneration of ferric in solution can be enhanced by providing the appropriate acid and oxygen levels according to Eq. (3). In the absence of microorganisms, this reaction is very slow."

Jan 1, 2015

By Ben L. Seegmiller

The basic compression-yield concept of roof support for mine roadways requires that the mine roof be placed in a state of compressive stress. The compressive stress may be achieved using a support system such as an entry truss or other specialty truss device. Furthermore, the roof must be allowed to yield, but with great resistance when abutment loads are placed on the roadway. The resisted yielding may be provided using a new yieldable steel prop, known by the trade name, YIPP~. The yieldable steel prop can allow as much as 1.5 m[5 ft] of yield, or up to approximately 40% of the opening height, while providing a resistance in excess of 60 mt[66st]. More than fifteen mining operations including coal, trona and hard rock mines have field tested the YIPPI . Present results indicate that the yieldable prop provides a cost-effective alternative to wood cribs, concrete cribs, hydraulic props and other steel prop supports. The paper describes the YIPPI including its unique principle of operation, its applications and actual field performance.

Jan 1, 1992