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By Frank van der Meer, Jorge Portocarrero, Alexandra Gruendken

"The number of High Pressure Grinding Rolls (“HPGRs”, also called Roller Press) installations instead of tertiary crushers is rapidly increasing. The technology has been largely accepted in the minerals industry and benefits, such as superior energy efficiency and a lower overall operating cost compared to alternative technologies, have been demonstrated at a number of operations throughout the world.This paper focuses on coarse hard ore operations and reviews the successful installation of the first Roller Press installed instead of a tertiary crusher at the Los Colorados Plant of CMH (Chile) in 1998. It details the experience obtained over the past ten years of operation from commissioning to the present day. It highlights examples of further developments made in the design to improve machine maintainability and availability as well as wear life of the grinding surfaces.A second focus lies on procedures to derive from small scale testing material properties such as wear life, flake formation and strength and their application to industrial size machines to optimize circuit design, especially when Roller Presses are used in closed circuit with screening.INTRODUCTIONRoller Presses (also known as HPGR, High Pressure Grinding Rolls) are considered today state of the art for the preparation of pellet feed. They are also gaining wide acceptance in coarse ore operations. One of the first successful operations in which a roller press was used to replace a conventional tertiary and quaternary crusher is the Los Colorados plant of CMH in Chile.When the Roller Press at Los Colorados was commissioned in 1988, there were 169 Humboldt Wedag roller presses in operation throughout the world. Of these, 14 were installed in the minerals industry. However, these were installed mainly for grinding pellet feed to increase the Blaine value. Up to that time, only three KHD roller presses had been applied for crushing coarse ore in specialized circuits. Moreover, the installation at Los Colorados was the first Roller Press ever to replace a conventional tertiary and quaternary crusher in a hard ore application."

Jan 1, 2009

By Conné Spangenberg

Contents ?Introduction ?Metal accounting environment ?Problem statement ?Investigations & Achievements ?Metal Accounting ?Principles ?Standards ?Audits ?Questions

Jan 1, 2005

By E. C. Morton

The Western Australian School of Mines (WASM) has developed a facility for the static testing of large scale ground support elements. The samples are loaded using a mechanical screw feed jack. Instruments measure the displacement and the load being applied. Methods have been developed for testing of mesh, shotcrete and membranes. Mesh samples are restrained on all sides and loaded centrally. A new large scale punch test method has been developed to evaluate shotcrete and membranes. These products are sprayed on to a sandstone substrate containing a centrally located isolated disc. The sprayed product is loaded by displacing the disk. The different test methods are described in detail. The test program involved two types of mesh, several shotcrete mix designs with different curing times and one membrane product. The force-displacement responses are used to directly compare the products. The implications for implementation of the different ground support products are discussed.

May 1, 2009

By P. Kluge

Mining engineers frequently encounter complex design problems for which the critical components of the design are difficult to quantify or compare. Teams of people typically work on these designs and human perceptions and judgments play a strong role. To assist with this process, the analytical hierarchical process (AHP) as a decisionmaking tool is described in this paper. Although the technique is used in many other disciplines, it is currently not widely used in mining engineering in South Africa. To use the AHP process, the problem should be treated as a hierarchy that defines the goal, the alternatives to reach it, and the criteria for evaluation of these alternatives. Pair wise comparisons are conducted on the criteria of the hierarchy to establish priorities. The value of the technique is that it is simple to test for consistency amongst the pair wise comparisons to ensure that the answer obtained is better than that provided by a random selection. To illustrate the technique, the use of a backfill support system in a platinum mining project was investigated. Ten design parameters, which will be impacted by the use of backfill, were identified and weighted according to their relative importance. The result of the AHP evaluation was that the use of a backfill support system should be preferred to a conventional support system at the mine.

Jan 1, 2011

Greymouth River Dredge û Birchfield Minerals Ltd Blackwater Gold Mine û Macraes Mining Company Ltd Globe Progress Gold Mine û Macraes Mining Company Ltd

Jan 1, 1996

By David E. Thompson

This paper describes the full-scale field load testing of three deep foundation units using the Osterberg Load Cell. The load tests were completed on three separate projects, two in Massachusetts and one in New York. The Massachusetts projects involved the load testing of two 18-inch O.D. concrete-filled steel pipe piles over water for railroad bridge reconstruction projects in Revere and Saugus/Lynn. The New York project involved the load testing of a 24-inch diameter drilled shaft socketed into sandstone on land for a building foundation in Rochester. The 18-inch O.D. piles were loaded to failure at jack pressures of 142 to 215 tons. The drilled shaft was loaded to failure at jack pressures of approximately 450 tons. The loading testing procedure is described and the results of the three tests are presented. The advantages and disadvantages of the Osterberg load cell for load testing of deep foundations are discussed.

Jan 1, 1989

The only simple sulphide mineral of antimony of importance is stibnite, SbS3, containing 71·8% antimony when pure. It is lead-grey, has a densityof 4·5 to 4·6 and melts at 546°C. It is both friable and sectile (Hardness 2 on Moh's scale) and, as a result, slimes very readily during milling.It is commonly associated with pyrite and arsenopyrite other minerals occurring with stibnite in minor quantities are chalcopyrite, galena, and scheelite. The latter mineral occurs in sufficient quantity at the Yellow Pine Mine, Stibnfte, Idaho, to justify the production of a scheelite concentrate.Stibnite mayor may not contain gold. Other minerals such as pyrite or arsenopyrite may contain gold. At Wiluna at the main mine nearly all the gold is asociated with arsenopyrite the stibnite being almost free from gold, whilst at the Moonlight Mine both arsenopyrite and stibnite carry gold.The mineral, tetrahedrite, which is a complex sulphide of copper and antimony; must also be considered an economic source of these two metals.Part of the copper may be replaced by iron, zinc; silver; or mercury, whilst part of the antimony is often replaced by arsenic.CLASSIFICATION OF ANTIMONIAL GOLD ORESFor the purposes of this paper antimonial gold ores may be conveniently classified as follows: CLASS 1. Ores from which a satisfactory gold extraction may be obtained by fine grinding, followed by cyanidation and which contain insufficient antimony to justify tIie production of an antimonial concentrate.CLASS 2. (a) Ores in which a satisfactory gold extraction may be obtained by straight cyanidation, but which contain sufficient antimony to justify the production of an antimonial concentrate.CLASS 2. (b) Ores from which the gold extraction by straight cyanidation is unsatisfactory. This type of ore requires the production of an antimonial concentrate for reasons which will be considered later.In deciding whether an ore belongs to class 1 or 2 (a) it should be remembered that the normal price of star antimony is about £1.00 sterling per ton and that the value of each 1% of antimony recoverable as metal is worth about £1 per ton.The antimony content of antimonial gold ores is liable to be considerably...

Jan 1, 1944

This paper deals chiefly with the preliminary examination, when a decision has to be made as to whether a prospect has a chance of developing into a mine or not. At this stage it is important to have a fairly clear conception of what is expected of the prospect, andjust what type of mine is sought. Much money can be wasted testing a prospect suitable for a prospector or small syndicate, but which never looked like becoming a mine of sufficient size to interest a company. When undertaking an inspection, therefore, it is necessary to have a broad outline, at least, of the policy of the principals for whom the report is intended.At this early stage it is frequently necessary to form an opinion of the prospects of a property on very meagre data. When new to this type of work one's first reaction is often th~t it is impossible to pass an opinion on the data available. It. is absolutely necessary,however, that an opinion of the possibilities and chances of favourable development be given; The report should strive to convey this information, making quite ::lear the risk involved, how complete are the data on which this opinion is based, and the possible magnitude of the prize. A Preliminary report has to state whether a property has sufficient prospects to warrant testing.The following procedure is suggested in order to make best use of the data and minimise hasty conclusions influenced by preconceived ideas-an ever-present danger.Examination.The first stage is the examination. This should aim at collecting all available significant data, but avoid clouding the issue with detail which, at this stage, will not affect the decision. The following points are considered to be the main ones for which to look:-Geological Environment.As good a working knowledge as possible'of the geology of the area should be obtained. Government Geological Survey reports and maps, if available, will be a big help. A detailed knowledge of the regional geology is not necessary a,t this stage, but a broad outline of the geological setting of the prospect under review, and also of any other important mines in the district, is often helpful in the final decision.The Nature of the Ore-Body.Any facts concerning the nature or occurrence of the lode should be noted as, coupled with experience of similar bodies, they affect the ultimate decision.Structural Control.This is probably the most important factor, in the light of present geological knowledge. Its chief importance is due to two facts:-(a) Structure plays one of the prime parts in ore deposition.(b) Geological knowledge, of structure is somewhat in advance of knowledge of other factors influencing ore deposition.

Jan 1, 1950

US 4,134,944-Production of iron oxide ore pellets of uniform size and excellent strength. Small pieces of ore are rolled into nuclei in a first pellet-rolling circuit in the presence of a binder, the nuclei sized and hardened by sintering or cold-bonding of the binder, the nuclei rolled in additional ore to form product pellets, the pellets sized, the suitable size fraction taken as product, and undersize pellets returned to the rolling operation. P. A. Ilmoni and R. Drugge, assigned to Luossavaara-Kiirunavaara AB Jan 16, 1979. 5 pp. (264-37) Filed- 5-25-77 (800,278) Priority: Sweden, 6-2-76 (76/06,¬241). Same British 1,553,763, dated Oct 10, 1979. US 4,145,210-In the induration of pellets of iron oxide ore or iron works dust or sludge, a charge of dried pellets and 2-20% by weight of coke having a size range of from 5 to 30 mm, a drum index of more than 70, a reactivity index of less than 50, and a tumbler index of more than 50 is charged into a rotary kiln The charge is heated and passed through the rotating kiln to indurate the dried pellets without burning the coke Powder-coated coke is recovered from the kiln for reuse. Ring formation in the kiln is substantially prevented. K. Kato and K Kadota, assigned to Sumitomo Metal Industries, Ltd, and Sumitomo Heavy Industries, Ltd. Mar 20, 1979 10 pp (75-3) Filed- 2-22-77 (770,947) Priority: Japan, 2-24-76 (51/19,754) US 4,145,211-Method of cooling hot metallized iron oxide ore agglomerates from a direct reduction furnace Agglomer¬ates ranging from 3/a in to 41/2 in in cross-section and at a temperature of 1000-2000°F are formed into a moving bed while at rest relative to each other Air at ambient tempera¬ture is passed through the bed at a velocity sufficient to cool the agglomerates rapidly to a temperature no greater than about 500°F without substantial reoxidation of the metal in the agglomerates and by using air as the sole cooling gas. C A Czako, A Berzins, and M J Greaves, assigned to Arthur G McKee & Co Mar. 20, 1979 15 pp. (75-34) Filed: 7-18-77 (816,467)

Jan 1, 1980

By William M. Dowall

The recently completed in-pit crushing and conveying project at Phelps Dodge's Morenci Mine is rated among the world's leading materials handling projects. The operation involves the crushing and transport of more than 109 kt/ d (120,000 stpd) of copper ore, using regenerative conveyors capable of providing more than 5.5 MW (7000 hp) of equivalent electrical energy. The Morenci Mine is located 330 km (200 miles) east of Phoenix, AZ. Phelps Dodge Corp. owns an 85% interest in the mine. The remaining 15% is owned by Sumitomo Metal Mining Co., Ltd. and Sumitomo Corp. Copper has been continuously produced from the Morenci district since the late 1800s. Until 1989, run-of-mine ore was transported from active mining faces to the Morenci and Metcalf concentrators by truck and rail haulage. In that year, a system of in-pit, semi-portable crushing plants and overland conveyors was commissioned. This substantially reduced truck haulage and effectively eliminated rail haulage in the pit. The system used two semi-portable, in-pit crushing stations equipped with 60/89 gyratory crushers. The crushed ore from both plants reported to the first of two overland belt conveyors, arranged in series, for transport from the pit to a coarse ore stockpile. The system was "backed-up" by existing locomotive rail haulage.

Jan 1, 1993

By Rakesh Raghavaraju, Bibhu Mohanty

Prediction of fracture and fragmentation characteristics of a rock mass subjected to dynamic loads, such as in blasting remains a major technical challenge. The present study is aimed at characterizing the shock transmission properties in controlled experiments in small scale in a well-characterized granitic rock, under varying borehole coupling conditions. Single blast-hole tests were conducted in a granitic rock sample of 145 mm (5.7 inches) diameter and height. The boreholes (in two diameters: 6.4 mm (1/4 inch) or 9.5 mm (3/8 inch)) were loaded with detonating cord of varying charge weight (5.3 g/m or 25 grains/ft to 31.8 g/m or 150 grains/ft of PETN). The effect of explosion gas penetration into the target rock was eliminated by inserting a thin-walled copper liner along the borehole wall. Embedded carbon composite resisters were employed at varying distances from the borehole to measure transmitted shock pressure for two coupling conditions (i.e. air and water) at distances of 1x to 9x the borehole diameter. The paper analyzes the decay of shock pressure as a function of distance from the borehole, and its implication on shock-induced fracture properties of the target rock as the first step in predicting fracture and fragmentation behaviour in a well-characterized rock.

By Michael H. Wysockey

The load test program for the pile foundation at Soldier Field included static and dynamic load tests at four locations around the site. The dynamic tests were run with no knowledge of the static results, and comparison between the two is very good. It was necessary to use a special testing hammer (not the production hammer) to demonstrate capacity with dynamic testing. Over 90% of the piles were HP14x89 with a design load of 230 tons (18 ksi). The load tests showed a capacity in excess of 590 tons for all tests where sufficient set up time was allowed. The remainder of the piles were mostly HP 12x53 with a design load of 100 tons (13 ksi). The measured capacity of these piles was typically about 250 tons. One experimental HP12×74 pile with a nominal yield of 65 ksi held 730 tons (67 ksi) before failing.

Jan 1, 2002

By G J. Corbett, T M. Leach

Approximately 42 t of mercury were produced from Puhipuhi from the late nineteenth century until the end of World War II, with no significant gold or silver production. Sinter, eruption breccias and veins, mined for mercury at Puhipuhi and essentially barren of gold, are inferred in many geological models to represent the surficial levels of adularia-sericite style low sulfidation gold-silver systems. These systems may contain economic gold-silver mineralisation at depth. Conceptual geological models have been employed at Puhipuhi in the search for buried gold mineralisation. Homestake Mining utilised a McLaughlin model for exploration from 1982 to 1987, targeting mainly the vicinity of the sinter deposits. From 1987 to 1989 BHP sought deeper structurally controlled gold mineralisation within the basement greywackes, utilising models derived from studies of Round Mountain, USA and Hishikari, Japan. Macraes Mining Company Limited have accessed the previous work and applied a conceptual geological which invokes a north-south structural control for the emplacement of high-level felsic intrusions at depth. Dextral movement on these structures associated with oblique convergence facilitated the formation of a pull-apart basin in which lacustrine sediments overlie basement greywackes and are in tum overlain by Pliocene basalts. Continued activation of the NS structures created a series of inferred NE-trending dilational structures, which are targeted as fluid upflow centres for the surficial outflows. Upflows occur as eruption breccias (e.g., Plumduff) and outflow as silica sinters (eg Mt Mitchell, Williams) which are also partly obscured by the basalt cover. Argillic alteration and mercury mineralisation occur at elevated crustal levels (eg Puhipuhi mine). Modelling from structure and alteration zonations have targeted a fluid upflow in the vicinity of Bush Hill, which was not accessed by previous workers. This target was subsequently supported by surface geology and multi-element soil geochemistry.

Jan 1, 1997

By John Wise

Significant movement to an existing slurry wall which serves as a retaining wall on 'O' Street in Southeast Washington, D.C. initiated the Department of Public Works for the District of Columbia to invite specialty contractors to propose a rehabilitation and stabilization for the failed slurry wall. Nicholson Construction Company proposed and was awarded a contract for the construction of an anchored precast lagging and soldier pile wall to be located approximately 4 feet in front of the existing structure with granular fill placed between the new and existing walls. Stabilization of the existing slurry wall also included drilling horizontal weep holes and demolishing the failed panels down to the existing ground surface. A new and improved drainage system was also constructed to increase the amount of water directed toward the existing storm sewer system running along 'O' Street. This paper provides a detailed account of these construction activities.

Jan 1, 2003

By M. Beth McClenaghan

This paper summarizes diamond exploration techniques used in glaciated terrain, focusing on indicator mineral and geochemical methods applied to glacial sediments. Understanding the ice flow history, depositional history, and stratigraphy of glacial sediments are essential to successful sampling, interpretation and follow-up of indicator mineral and geochemical anomalies related to kimberlites. Kimberlite indicator minerals survive glacial transport over long distances and the relative abundance of each mineral in till is a function of the primary mineralogy of individual kimberlites. Indicator mineral distributions observed at a regional scale define the net effect of glacial dispersal, often along different ice flow directions. Local-scale distributions define individual dispersal trains. The medium sand (0.25 to 0.5 mm) fraction of heavy mineral concentrates prepared from glacial sediment samples is best suited for indicator mineral surveys. The application of till geochemistry to diamond exploration is increasing because it is significantly cheaper than indicator mineral analysis and it can be performed quickly. The <0.063 mm (silt+clay) and 0.5 to 2.0 mm (coarse sand) fractions provide the best geochemical contrast between background and kimberlite-rich till. Kimberlite pathfinder elements that provide good contrast include Ni, Cr, Ba, Co, Sr, Rb, Nb, Mg, Ta, Ca, Fe, K, Ti and REE, the relative importance of which will depend on kimberlite composition as well as that of the surrounding bedrock.

May 1, 2002

First Session BRASS Wednesday, A.M., Nov. 29 Co-Chairmen: CARTER S. COLE, Staff Engineer, A.S.T.M. E. A. ANDERSON, Chief of Metals Section, Research Div., New Jersey Zinc Co. (of Pa.) Second Session BRASS Wednesday, P.M., Nov. 29 Co-Chairmen: D. K. CRAMPTON, Director of Research, Chase Brass and Copper Co., Inc. A. W. TRACY, Metallurgist, The American Brass Co. Dinner and Technical Session Wednesday Evening, Nov. 29 Toastmaster: N. L. MOCHEL, Manager Metallurgical Engineering, Westinghouse Electric Corp. Talk on "How Do Things Look Today and For the Future" RALPH KELLY, President, Baldwin Locomotive Works Technical Paper on Stress-Corrosion Cracking E. H. Dix, JR., Assistant Director of Research and Chief Metallurgist, Aluminum Company of America Third Session BRASS Thursday, A.M., Nov. 30 Co-Chairmen: W. B. PRICE, Director of Research, Scovill Manufacturing Co. A. L. JAMIESON, Associate Metallurgist, Frankford Arsenal First Session LIGHT METALS Thursday, P.M., Nov. 30 Co-Chairmen: L. L. WYMAN, Metallurgist, General Electric Co. M. A. HUNTER, Professor of Metallurgical Engineering and Head, Dept. of Metallurgical Engineering, Rensselaer Polytechnic Institute Second Session LIGHT METALS Thursday Evening, Nov. 30 Co-Chairmen: R. T. WOOD, Chief Metallurgist, American Magnesium Corp. J. D. HANAWALT, Director, Metallurgical Dept., Dow Chemical Co. First Session STEEL Friday A.M., Dec. I Co-Chairmen: H. S. RAWDON, Chief, Division of Metallurgy, National Bureau of Standards A. L. FEILD, Director of Research, Rustless Iron and Steel Corp. First Session MISCELLANEOUS METALS Friday P.M., Dec. I Co-Chairmen: E. A. ANDERSON, Chief of Metals Section, Research Div., New Jersey Zinc Co. (of Pa.) CARTER S. COLE, Staff Engineer, A.S.T.M.

Jan 1, 1945

"This paper describes some of the methods and equipment used for fine milling of minerals, and gives particular attention to the Vibro Energy system.In addition, the paper describes a specific application in the gold mining industry. This is the 200 tpd plant built by Anglo American Corporation at the President Brand Mine in South Africa in 1985, now a division of Freegold. This plant treats a gold bearing pyrite flotation concentrate which is finely ground to 15 microns prior to cyanidation and carbon-in-pulp (CIP). l .0 INTRODUCTIONFree milling gold ores are those that yield acceptable dissolution and recovery of the gold following grinding to what can be described as normal fineness, frequently between 50% and 90% passing 74 microns.Increasingly, gold metallurgists are faced with ores that are refractory. The traditiona1 treatment route for refractory gal d ores and concentrates has been by roasting, but for environmental reasons this is becoming less acceptable, or in some areas of the world, totally unacceptable. New methods of treating refractory gold ores are being developed and applied in practice. These new methods include pressure and biological oxidation. Higher gold liberation can also be attained by increasing the fineness of grind, although with conventional systems there are economic limits to this.In flowsheet development and test programs on new deposits, a standard procedure is to establish the relationship between the grind and subsequent go 1 d extraction. The normal situation is that gold extraction increases as the ore, or concentrate, is ground finer. Typically, this relationship is as shown in Fig. l, where the incremental additional extraction is very small once an optimum, or economic, grind has been achieved. This generally app1ies whether the material is free milling or refractory. The limits to grinding are set by the type of equipment which is commonly in use, usually ball mills. These mills have the obvious advantage of high capacity, however, they are increasingly inefficient as finer grinds are required. In general, ball mills are used to reduce ore to some agreed percentage passing 74, or possibly 53 microns."

Jan 1, 1988

The mining industry has recognised for some time the importance of supporting programs which serve to educate the Australian public about the socio-economic benefits of mineral resource development. More recently, industry leaders have realised that the future development of the industry will depend on attracting sufficient young people to commit to a career in the industry. Apart from lending support to the traditional education institutions in Australia, the industry now has the opportunity to participate in the development of education programs in museums. Whilst historic, mining-related theme parks such as Sovereign Hill and Coal Creek in Victoria serve very effectively the objective of relating past mining activities to the socio-economic development of Australia, there still exists the need to provide a facility which, under the same roof, excites interest in geology, mining, mineral processing and the role of minerals and energy in modern society. The redeveloped Geological and Mining Museum (the "Mining Museum"), which is located in The Rocks area of Sydney, meets this objective. With the central themes of formation and transformation this new Museum, which aims to be the best of its type in the world, will use modern museum exhibit techniques and the resources of the Minerals and Energy Information Centre to educate the community including teachers and school children. In the best tradition of museums, outstanding mineral and other collections will complement a comprehensive range of interactive, high technology exhibits which will include a number of exploratory "hands on" facilities. Australian companies are joining with Government to fund this exciting new museum. There is still a need for industry professionals to realise that a modern "mining" museum is no longer just a repository for objects of mining heritage but is also an important centre which serves as an important educational and public relations interface. The Education Section of the new "Mining Museum", which is linked closely with the new Minerals and Energy Information Centre, will be working closely with appropriate mining-related Tertiary institutions to develop specific career programs aimed at secondary students who wish to pursue a career in the mineral resource industries.

Jan 1, 1989

By H. Lyn Bourne

This is the fifth annual tabulation of mineral royalty information. This tabulation, like the previous editions, includes all of the earlier data. There are also 60 new entries. In addition to royalty information, some entries show the cost of purchased reserves. Two articles relative to the evaluation of minerals reserves appeared in December, 1986. R.H. Paschall (In the Aggregate, ME, p 1139) wrote a good article, although it lacked specific royalty data. However, this author takes exception to two ideas in Paschall&apos;s column. Paschall contends that the royalty rate does not affect the mineral appraisal. This present author could not disagree more. Paschall also claims the location of an industrial mineral deposit is the only serious or practical caveat in comparing royalties. Comments received here from readers helped make the list of caveats that are cited each year. The readers will decide which factors influence the mineral value for their commodities of interest. Paschall&apos;s point about the relationship of the parties who are negotiating a royalty agreement is important and very well taken. The other article, written by William Vernon (Pit and Quarry, December 1986), gives a step-by-step process on how to conduct a mineral appraisal. The article cites three reasons for an appraisal: transfer rights; collateral for a loan; and taxation. A fourth reason is to establish adequate compensation for reserves lost through condemnation. This author has appeared in several court cases where compensation for loss of mineral reserves through condemnation required a mineral appraisal. Royalty rate becomes an important factor in the appraisal process, although the Pit and Quarry article refers to that part of the valuation equation as "profitability." Both articles were well written and are recommended reading for those interested in mineral valuations. The same caveats that have appeared in previous columns relative to factors that influence the value of reserves are restated. The data in the table serve as a general reference and are not intended to present an absolute scale of reserves costs. Several factors influence the value of any mineral commodity. The factors include: • location/transportation - especially significant for most industrial minerals; • market conditions both for the commodity and the company acquiring the right to mine; • quality or grade of the deposit as it reflects the amount of processing/beneficiation necessary to produce the finished product; and • legislative restrictions and conditions for mining a given material at a given site. These and other factors will significantly influence the cost of reserves. The table shows the range of royalties and the variations in the basis of computing the fees. In a few instances, it gives the cost of acquired reserves based on purchase price and quantitative estimates of the material in place. The table lists the commodity in column 1, and the subsequent columns give: • the location by state, US geographic area, or Canadian province ; • the cost - R for royalty and P for purchased cost; • the year in which the lease or purchase agreement occurred; and • comments or footnotes for more information. The cost column requires more explanation. The units may refer to cubic yards (/cu yd), cubic feet (/cu ft), short tons (/T), or acres (/A). 1 cu yd = 0.76 M2 1cuft = 0.28m3 1 st = 0.9072 t 1 acre - 0.4047 ha or m2

Jan 7, 1987

By D. A. Trotter, G. J. Goddard

"This paper describes a method of deciding on various design parameters for a sublevel caving layout. Layout design curves are obtained from the output of a computer optimization program. The program uses mathematical relationships derived from the theory of gravity flow of material to optimize the large number of interdependent design variables which are involved.IntroductionIn the design of an efficient sublevel caving mining system, a large number of interrelated variables need to be considered. Although many papers discuss individual variables, very little exists in the literature to show how these variables interact to achieve optimum results. This can lead to trial and error in sublevel caving design, which can prove costly, particularly because sublevel caving is a mining method which requires integration with sublevels above and below. With no pillars being left, experimental stopes cannot be isolated for study. Unfortunately, the complexity of layout design and the costs associated with trial and error have caused many planning engineers to choose more tried and tested mining methods.Sublevel caving works best to extract low-value ore surrounded by incompetent rock. All phases of the mining method can be highly mechanized, allowing low operating costs and high production rates. Good safety records are achieved, as workers are always in &apos;good&apos; ground and the method is regular, making it comparable to an industrial process."

Jan 1, 1981