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By D. Harrington

The record of fatalities from mine explosions in the United States during the fiscal years 1934 to 1937 wars the best in the history of the mining industry; that for the fiscal year 1939, however, is not so favorable, since nearly as many men (170) were killed by explosions in 1938 as were killed during all of the previous 4 years (182). In spite of the large increase in fatalities from explosions during 1938, the average for the past 5 year period (70.4) is less than one-half the average (13) of the preceding 5 year period. The reasons for the large increase in the number of explosion fatalities during the 7 past year as compared with the previous 4 year are not entirely clear; it is: evident, however, that in some instances there has been laxity in the enforcement of State minim laws, and also that come of our coal-mining people, including workers and operating officials, have failed to carry out tine known precautionary measures to prevent explosions.

Jan 1, 1939

By Samuel S. M. Chan

Rock surrounding mine openings frequently is an impermeable type such as shale or granite. Most rock, however, has joints, bedding planes, cleavage planes, or other potential discontinuities. Permeability to fluids (gas or liquid) may exist via natural joints or fractures in an otherwise impermeable rock. In the mining situation, tectonic and induced tensile and shear stresses may be great enough to cause joints to open or fractures to develop in previously solid rock. The rock, as a result, becomes less self-supporting and may - require artificial support such as rock bolts or timber. Simultaneously, as fractures develop, permeable paths may be created. If fluid can be injected into a previously solid and impermeable rock mass, a logical conclusion is that a fracture (crack) flow path must be transmitting that fluid. The U.S. Bureau of Mines Laramie (Wyo) Energy Research Center has been evaluating results of in-situ oil shale fracturing (hydraulic or explosive) and retorting experiments by. a fluid (air) injection , and borehole air flow profile logging technique since 1956 (1, 14, 15). In the oil shale case, it is imperative to know the location and flow capacity (permeability) of natural fractures, if they exist, and induced fractures that inter-connect vertical wellbores at depths of fifty to several hundred feet. By injecting air into one wellbore in a system of several wells and measuring input volume and pressure while simultaneously measuring the output of other wellbores, the minimum areal extent of interconnecting permeable fractures can be determined. Exact locations (depths) of fractures and individual fracture flow capacities between wellbores can be determined by air flow profile logging (14, 15). Knowledge of fracture locations and permeability is essential to rational experimental in-situ retorting design.

Jan 1, 1973

By Richard R. Marston, Scott Herr, Steve Pries, Donald L. Jr Ewart

The purpose of this paper is to identify and examine alternative methods (other than shovel/truck stripping) of effecting the pre-stripping of consolidated overburden, in conjunction with dragline stripping operations, at surface coal mines. The analysis will be case study oriented with practical mining considerations and comparative economics being evaluated. Alternatives that will be examined include blast casting, dozer push, and multiple pass dragline sequences.

Jan 1, 1992

By F. Castelli

A simplified non-linear method to predict the behaviour of a single pile and/or pile group under horizontal loads is presented in the paper. The evaluation of the non-linear lateral deflection is based on a procedure taking into account the decrease of the model stiffness with the increasing of the applied load. The solution derived firstly for the single pile, was extended to the case of a pile group introducing the p-multiplier (fm) concept proposed by Brown et al. (1988).

Jan 1, 2006

The Tertiary gold deposits of the Hauraki area are predominantly epithermal vein types containing mineral assemblages of quartz, calcite, pyrite, sphalerite, galena, chalcopyrite, acanthite and native gold (electrum). Sulphosalt, telluride (eg hessite), seleniferous sulphide and selenide minerals are important locally. Studies of wall rock alteration mineralogy, fluid inclusions in gangue minerals, and sulphur isotopes of sulphide minerals indicate that the ore forming fluids had the following parameters: pH, near neutral at depth but acidic near surface; temperature, predominantly 320 - 270¦C for base metal dominated assemblages, 280 - 200¦C for precious metal dominated assemblages and generally below 200¦C for late stage barite; apparent salinity, six to zero equivalent weight per cent NaCl; and CO2 concentration, generally around one mole per cent CO2. There is fluid inclusion evidence for boiling during mineralisation in some deposits. Moderate values off S2 and FO2 are indicated for base metal and mixed base metal û precious metal assemblages of most deposits by the predominance of pyrite + chalcopyrite over other iron-bearing phases; primary bornite is absent, whereas pyrrhotite, hematite and magnetite rarely occur in the veins. The largest gold û silver deposits formed from solutions in which the sulphur species in solution were predominantly reduced. Near surface environments and some deep, predominantly base metal, deposits were formed from solutions with approximately equal concentrations of oxidised and reduced sulphur species.

Jan 1, 1984

By Jorgen Elbrond

The calculation of open pit operations' capacities has been the subject of many studies using computer simulations. The common problems of simulation are that if one desires a realistic picture of an operation the programming work becomes long and expensive and that the program requires a large computer and long time to run. The method presented in this paper overcomes these problems by using a straightforward calculation procedure. It is based on the queuing theory's simple formula for waiting time in a closed circuit and uses a system of correction factors, which reflect the loading, travel, and dumping times' relative variabilities and which have been found by 1) mathematical analysis and 2) simulations of basic circuits. The method includes the main parameters of the operation: numbers, sizes and operational availabilities of trucks, shovels and dumping point, distribution of the production over shovels, trucks' loading, travel (loaded and empty) and dumping times as well as their variabilities, shift's composition. The procedure models: the average duration of a complete truck cycle during stationary and non-stationary periods during the shift as a function of the number of trucks in the circuit, the composition of the average 100% operated shift, the simultaneous probabilities of operationally available shovels and trucks and the distribution of shovels and trucks according to production and cycle times. The procedure can be programmed for a small computer and requires only short computing time, which makes extensive studies of various parameter combinations practical to carry out. The development of the method is an extension of previous work by Morgan and Peterson {1}, who by simulation established the relation between the match factor (which is the ratio between the sum of one loading time pr truck in the circuit and the complete net cycle time) and the shovel's efficiency, and by Hayes, Splaine and Whitaker {2}, who established this relation from a large number of observations in the Nchanga pit in Zambia. The present method establishes this relation by a straightforward calculation procedure. Theoretical solutions to some situations are found in the litterature on the queuing theory. The papers {3},{4} and {5} give solutions to situations, which fall outside those encountered in the shovel-trucks circuit. These solutions together with simulations of in-termediary situations have been used to establish an interpolation procedure for the correction factors to be applied to the waiting time formula in order to cover the situations encountered in practice.

Jan 1, 1977

By A. W. Fahrenwald

"About two years ago the Bureau of Mines, Department of the Interior, and the University of Idaho undertook an investigation of classification in its relation to table concentration of Idaho ores. The cooperation of the management of the Bunker Hill & Sullivan Co. in placing at our disposal their West Mill and facilities as desired, offered an unusual opportunity for studying the field of hindered classification in its practical and economic relation to table concentration.It has been shorn theoretically, and demonstrated experimentally, that ore products are more easily and economically concentrated on tables if the natural feed, consisting of various minerals and of all sizes of particles of each mineral, be classified or grouped into a series of products in which the mineral particles of greatest density are small in diameter relative to the diameter of the mineral particles of lesser density. Products in which the maximum difference in diameter of light and heavy minerals occurs are to be obtained only by true hindered settling classification. To our knowledge there has never been a really good hindered settling classifier used in practice and the present tendency seems to be to by-pass any attempt at such classification.After a careful study of the nature of hindered classification and of the requirements for hindered settling in practice, a classifier has been developed that takes fullest practical advantage of the widely known, but generally only meagerly understood, condition of hindered settling so well analyzed a number of years ago by Dr. Richards.The present paper presents briefly some of the more important practical results accruing through the investigation."

Jun 1, 1924

By A. Berry, N. R. Banerjee, C. S. Finnigan, M. Fayek, N. J. Bridge

Lac Cinquante is a mineralogically simple, vein-hosted uranium deposit in Archean basement rocks (Angikuni greenstone belt) that originally were unconformably overlain by Proterozoic sedimentary and volcanic rocks of the Baker Lake Group (BLG). Basement rocks are mainly pillowed and massive tholeiitic lavas (N-MORB) with interbedded tuff; overlying sedimentary rocks comprise a basal talus/fault breccia that grades upward into fluvial sedimentary rocks and subaerial, trachytic volcanic rocks; granite and porphyry dikes (Hudson and/or Nueltin granitoids) intrude the basement rocks. A typical section through the Main Zone comprises 1) laminated ‘tuff’, 2) altered (carbonate-hematite-chlorite) schistose ‘tuff’, 3) a pitchblende-bearing, breccia-vein, 4) altered ‘tuff’, and 5) laminated ‘tuff’. The vein comprises brecciated chlorite, hematite, and pitchblende with carbonate cementing the breccia. Graphitic ‘tuff’ with sulfide-stringer veinlets locally overlies or underlies the vein. Pitchblende also occurs in the altered rocks and in gash veins that cut basement rocks. U-Pb ages on pitchblende fall into two groups: one at 1828 } 29 Ma reflects primary uranium mineralization, and a second at 1437 } 31 Ma represents resetting. Pb-Pb chemical ages show other resetting events at 1260-1321Ma, 895 Ma, 741-813 Ma, and 660-706 Ma. One possible genetic model for the Lac Cinquante deposit involves leaching of uranium from granitoids and the BLG by basinal brines that migrated to depositional sites where graphitic rocks acted as a reductant. A second model requires that uranium was sole-sourced from the BLG and that granitoid rocks provided heat to drive the hydrothermal system, which leached and ultimately precipitated uranium. The deposit has characteristics similar to vein-type uranium deposits in the Beaverlodge District of Saskatchewan

Jan 1, 2013

By S. Kline

The compositions of metamorphic minerals of the south limb of the Dore Lake Complex have been determined by microprobe techniques. Mineral assemblages typical of the greenschist facies occur in Mg-rich bulk compositions, but in Fe-rich rocks albite-epidote amphiboli te facies assemblages occur. Low oxygen fugaci ties and a general paucity of metamorphic fluids prevailed in most of the complex, but a higher oxygen fugacity is indicated near the Chibougamau Pluton, and a local abundance of C0z and Cl in fluids near the pluton is suggested by the presence of scapoli te. The metamorphic gradient overprinted on the complex near the Grenville Front is apparent in mineral chemistries as well as by the appearance of garnet. Chlorite becomes richer in Mg, and iron is fractionated more strongly into hornblende. The amphibole also increases in Alz03.

Jan 1, 1984

This paper describes the methods of constructing timber barricades against pillars of ore in the South Mine, property of Broken Hill South Limited, Broken Hill, N.S.W., and discusses the behaviour of the various types of barricade alongside trucked sand filling and hydraulic stowed sand filling.Since the introduction of hydraulic stowing, cut and fill and overhand square letting methods have been used in mining the pillars. Such methods could not be used where the pillars had failed badly. The filling used is partially deslimed concentrating millresidue containing among other gangue minerals, calcite and a small amount of pyrrhotite and pyrite.The author is indebted to the mine superintendent of Broken Hill South Limited for permission to publish this paper.OLD METHODS OF CONSTRUCTING BARRICADES.Square Set Stopes.Before filling each stope the outer row of legs was lined inside with 10 in. x 2 in. boards spaced 2 in. apart. It was usual to tie the row of legs and caps together with timber dogs. As the space between the barricade and ground varied from nil to several feet, it was general practice to fill behind the lining boards. No provision was made to retain this sand during subsequent pillar stoping, consequently a run of sand right up the barricade could cause adilution of ore and serIOUS dIstortion of the barricade.

Jan 1, 1946

By J. Baicker

A two-inch diameter probe containing an intrinsic germanium detector, a canister-type solid cryogen cooling system, cooled FET preamplifier, linear amplifier, high voltage supply, analog-digital converter, microprocessor, buffer memory, bidirectional cable link, and all power supplies has been designed, assembled and tested. A surface support vehicle was designed, built and outfitted. A mini-computer system was constructed and preliminary software developed and tested. A special handling system for a Cf-252 neutron source was designed and has been ordered. The entire system (less the neutron source) is ready for its first field tests. Lab description of the system is presented.

Jan 1, 1978

By Susan B. Robertson, Gregory E. Hinshaw

Many injuries are caused each year by rock falls in coal mines. Most of these injuries are not caused by major roof collapses, but from falls of smaller rocks from the immediate top or roof skin. Various surface controls are used in mines to control this surface rock. One that has been found to be very effective is roof screening. Depending on the size of the screen, roof coverage approaching 100%can be achieved. Many mines are reluctant to use screen for primary skin control because of additional costs of time and materials, but others are having great success at both controlling costs and surface rock. Data is presented from two mines that show a dramatic reduction in roof skin injuries when screening is used. Much of this success is due to innovations in roof bolting machines. Four case studies of roof screen experience are presented along with associated costs of materials, impact on bolting advance rates, and potential ergonomic risks. The effects of roof screening on skin control and safety are also included. Finally, this paper will provide information about features of different roof bolting machines that affect production and safety.

By A. J. Rigby

Refractory linings in converters or anode furnaces used to over-oxidize the blister copper will suffer rapid deterioration, due to prolonged contact with copper oxide-rich slag. Nitrogen stirring with COP KIN porous plugs and use of SEMTECH OPC in converters and anode refining vessels can considerably reduce both refractory wear and processing times. In addition, careful control of the vessel atmosphere and the use of real-time optical process control minimize both slag volume and contact time with the vessel refractory.

Jan 1, 2005

As a result of early experiments in underground mine illumination, the Bureau of Hines recognized the need for additional experience with the underground lighting of coal mines having low seam thicknesses. There was already experience with tile illumination of coal mines having higher coal seams, and this contract with Ocean Energy Inc. (OEI) was undertaken to contribute to the "low coal" experience. For the purpose of this contract, a "low coal? mine is defined as one having less than 45 inches of overall headroom in the working places. As a practical limit, 26 inches was the minimum coal seam thickness to be encountered in this program. In one instance, the maximum coal seam thickness was eight to ten feet, however, this particular work was at the direction of the Technical Project Officer (TPO) by virtue of the unique type of lighting arrangement that was to be evaluated which would be useful for low coal. At the outset of the contract, three major tasks were established. The first two tasks involved the installation of permissible fluorescent lighting equipment at two low coal mines. The intention was to illuminate mining sections in each case consisting of one or more machines. The third task was to illuminate a variety or mining equipment including a longwall. For the purpose of this report, the fol-owing identifies the particular installations associated with each task.

Jan 1, 1976

By J. C. Barrett

Bureau of Mines research on the arc welding characteristics of titanium was initiated in 1948. Little was known about the art except that the easily contaminated metal required more protection from the atmosphere during welding than most other metals. Chambers were designed and built within which titanium could be welded with adequate inert gas protection. Welds were made and their properties studied, and prototype items were made successfully. This report, presenting a resume of the titanium arc-welding experiments undertaken by the Bureau of Mines, demonstrates that the process is successful if conducted under proper conditions and describes the welding of prototypes. INTRODUCTION The Bureau of Mines' first report on methods of joining titanium covered the subject of spot welding,4/ outlining the conditions necessary for producing spot welds in ductile titanium consolidated by powder metallurgy methods and describing the characteristics of such welds. This report embraces the field of fusion weld-ing of titanium and traces the development of suitable methods and equipment for producing such welds.

Jan 1, 1956

By M Olsson, U Nyberg, K Widenberg, P Svedensten, F Ouchterlony

During 2007 and 2008, the project Optimal Fragmentation in Blasting II was conducted at the Långåsen quarry of NCC Roads AB near Arlanda. The main goals were:an evaluation of the effect of using electronic delay detonators (EDDs) in quarry blastinga validation of the design curve concept introduced at the Vändle quarry.Five production blasts were monitored. After a first trial round, the remaining four rounds each had about 100 Ø89 mm holes in a 14–19 m high bench charged with site mixed emulsions. In rounds 1 and 2, a tighter pattern than normal was used in one half of the rounds, raising the specific charge there from 0.7 to 1.0 kg/m3. Non-electric initiation was used with two holes per 25 ms delay in-row and 67 ms between rows. In rounds 3 and 4, electronic delay detonators were used instead, with 10 and 5 ms in-row delays respectively.The monitoring encompassed drill hole collaring and alignment, in-hole deviations, the rock structure in the bench faces from 3D imaging, first row burdens, etc. Eleven 400 t samples were taken from the muck piles and sorted in the quarry and sieved in the laboratory (lab). The lab data made up a fines tail that was grafted onto the in-pit sorting data to form sieving curves for the test piles. These curves were then compensated for the absence of boulders to construct the sieving curves for the blasted muck pile.These have been used to derive fragmentation model formulas for the non-electric rounds, also called design formulas. They are based on blast geometry, charging data and the properties of the rock mass. The formulas may be used to estimate the effect of changing blasthole pattern, borehole diameter and stemming length for example.The use of EDDs gave several unexpected results. In comparison with non-electric initiated rounds with a somewhat lower specific charge the fragmentation was much coarser; x50 increased from 160 to 200 mm. The effect of raising the specific charge in the non-electric initiated rounds from 0.72 to 0.99 kg/m3 was a much finer fragmentation; x50 decreased from 160 to 120 mm.CITATION:Ouchterlony, F, Nyberg, U, Olsson, M, Widenberg, K and Svedensten, P, 2015. Effects of specific charge and electronic delay detonators on fragmentation in an aggregate quarry – building fragmentation model design curves, in Proceedings 11th International Symposium on Rock Fragmentation by Blasting, pp 727–740 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 24, 2015

By Benjamin W. Haynes

The Bureau of Mines, in cooperation with the National Oceanic and Atmospheric Administration (NOAA), has updated a 1977 NOAA report prepared by Dames & Moore entitled, "Description of Manganese Nodule Processing Activities for Environmental Studies." This updated report contains detailed flowsheets and descriptions of the five potential first-generation nodule recovery schemes now considered most likely to be used by industry; they are high-temperature gas reduction and ammoniacal leach, Cuprion ammoniacal leach, high-temperature and high-pressure H2S04 leach, reduction and HCI leach, and smelting and H2S04 leach. The first three processes are three-metal recovery schemes (Cu, Ni, and Co) with the option of Mn recovery from the tailings. The remaining two processes are four-metal (Cu, Ni, Co, and Mn) recovery schemes. All except the HCI process are assumed to use a nodule feed rate of 3 million tons per year (dry basis). Final metal products are Co powder and cathode Cu and Ni. A minor amount of Ni is also recovered as powder, and some Cu and Zn are recovered as mixed sulfides. Manganese in the four-metal processes is recovered as either manganese metal or ferromanganese.

Jan 1, 1983

By D. B. Stewart

This paper reports on an investigation undertaken to determine the exhaust gas temperatures of operating underground mining equipment. The effectiveness of platinum catalytic purifiers is discussed. From exhaust temperatures, it is concluded that LHD engines are highly loaded, haulage truck engines are moderately loaded and utility vehicle engines are lightly loaded.

Jan 1, 1979

By John E. Tilton

During the past several years — much to the delight of producing firms and countries — copper prices have surged from under $1 to more than $3/lb. Anyone familiar with the industry also knows that since the early 1970s the long-run trend in real copper prices has been significantly downward. This sharp contrast between short-run and long-run trends raises the issue of the forces behind these developments. What has been driving short-run prices up and long-run prices down? Simple economics suggests that it is all a matter of supply and demand. When demand is rising faster than supply, prices will rise and vice versa.

Jan 1, 2006

By E de Villiers

Several methods exist by which the capacity of a dense media separation (DMS) plant can be improved: 1) Increase the feed rate in spite of efficiency 2) Replace with bigger equipment 3) Add whole new module 4) Replace total plant 5) Change over to four shift/ seven days per week roster 6) Replace with alternative process 7) Increase the availability and utilization Options 1 ? 6 have varying degrees of cost implications. The seventh option would seem to be the easiest. Normally it is also the function of the plant operating and maintenance team to maximize this. Usually higher operating and maintenance cost are associated with an increase in these parameters. A general principle that is applicable to plants and systems is that as the complexity increases, the total availability decreases. By simplifying the flow line it may be possible to reduce cost while at the same time increase the availability and utilization. The typical standard DMS flow line contains components that compensate for the variance in pump performance or for the inefficient recovery of ferrosilicon with additional equipment. Things have changed though: 1) Advanced electronic control and monitoring is possible 2) More efficient magnetic separators are available 3) New more user friendly densifiers are available ORIGINAL FLOW LINE In principle the process consists of four flow lines or streams 1) Ore flow ? the feed is divided into a waste and product stream by means of the separating vessel

Jan 1, 2006