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By Ruilin Yang

This paper provides a theoretical analysis of shockwaves in an air-deck induced by detonation of an explosive charge and shows that the initial shock pressure in the air-deck at the interface with the explosive charge is only about 1% of the detonation pressure. A rarefaction wave with the low pressure travels back into the explosion detonation products greatly reducing the post-CJ detonation pressure. Additionally, AUTODYN modelling shows that the pressure attenuates further during shockwave propagation along the air-deck. Although the pressure increases at the bottom of the blasthole due to shock reflection, the overall pressure in an air-deck does not increase and is still around 1% of the detonation pressure which is too low to break most rock.

Jan 1, 2016

By B Young

Variable bench heights, interaction with underground workings and a steeply dipping orebody are challenges faced daily by geologists at Xstrata Zinc’s Black Star Open Cut (BSOC) Zinc/Lead/Silver mine in Mount Isa, Queensland.BSOC has been in operation since late 2004 and was developed to extract the surface extents of the Zn/Pb/Ag mineralisation mined in the underground lead mine. To date many large scale stopes and extensive development drives have been intersected and successfully mined. The stratigraphically hosted orebodies strike in a north-north westerly direction, dipping ~75° west. Ore production from the pit is currently at 4.5 Mt/a.Historically, sampling was conducted using a multiple spear technique from blasthole cuttings. This method proved to be relatively reliable when blasting benches at a consistent height, but a requirement to vary bench heights to safely collapse and then mine through underground workings reduced sample representivity to unacceptable levels.The purchase and commissioning of a production rig which had been converted for reverse circulation (RC) has allowed for the flexibility of a small rig, with the capacity to easily drill 48 m holes while ensuring sample quality. Sample quality is not the only benefit of introducing RC grade control. By collecting grade control data well in advance, informed decisions can be made by planning, drill and blast and mining departments weeks beforehand, rather than hours before firing. Additionally, seeking operational value to offset higher drilling costs has proved positive with benefits including increased confidence in orebody wireframes, accurate tonnage and grade for proceeding five benches along with the ability to representatively test metallurgical response on a tight grid spacing.

Aug 22, 2011

By Raja V. Ramani

Productive and beneficial use of reclaimed surface-mined land is a concern of industry, government, and the general public. An investigation was conducted of current mined-land planning practices to aid in the development of a procedure for evaluating postmining land use potentials. This investigation considered both the industry and public planning approach to mined-land planning. It included a detailed review of the impact of regulation, factors that determine land use, and current site planning methods employed by the mining industry. The methods of this investigation included three in-depth case studies of surface mines in the eastern, central, and western United States. A site planning pro-cess has been developed and applied to the surface mine case studies to evaluate the economic, environmental and social impacts of postmining land use alternatives. In add it ion, guidelines are proposed to enhance the cooperation between local land use planners and surface mine planners, as well as to improve comprehensive planning with regard to mineral resources at the local and regional level.

Jan 1, 1983

By S. Ajima

The Naoshima Smelter and Refinery is the most important copper operation of Mitsubishi Materials Corporation. There are a Mitsubishi Continuous smelter and a conventional type of copper tankhouse. The continuous smelter with 240,000 mtpy of anode production was commissioned in May 19914 replacing two existing smelters, i.e an original Mitsubishi Process line and a conventional reverberatory furnace line. In July 1992, the copper tankhouae was expanded for the purpose to close the gap of production capacity between the smelter and the tankhouse. The cathode production capacity was increased from 13,800 to 15,800 mtpm. By these plant modifications, the distribution of minor elements was significantly changed and the impurities load is getting on increase reflecting recent shortage of clean copper concentrates supply. The paper discusses the distribution of minor elements and the impurity control strategy at the smelter end the refinery.

Jan 1, 1995

By John D. Wiebmer

First, a definition of a small scale miner is in order. The US Bureau of Mines classifies him as one who produces 360 t/d (400 stpd) of ore or less. In Canada, he would be refered to as a "junior company." Mexico identifies the small scale miner as one whose gross income from operations is less than $880,000 per year. A small surface mine in India employs less than 400 people, and a small underground mine employs less than 150. Peru considers a small scale miner one who produces less than 54 000 t/y (60,000 stpy) of ore. Obviously, the term is relative. What may be a small mine in one country is a medium or large mine in another. This lack of agreement is understandable since small scale mining does not often cross national boundaries. Rather, its effects are felt at the regional and local levels within each nation. Its importance doesn't lie with any huge contribution to the GNP or balance of trade. Instead, its value is as a local employer and as a frontrunner in geologic exploration.

Jan 2, 1979

By P. G. Dempsey, J. R. Heberger, J. P. Pollard

During a mine disaster or emergency, underground air can quickly become contaminated. In these circumstances, all underground mine workers are taught to don breathable air supply units at the first sign of an emergency. However, no contemporary oxygen consumption data is available for the purposes of designing breathing air supply equipment specifically for mine escape. Further, it would be useful to quantify the oxygen requirements of breathing air supply users for various escape scenarios. To address this need, 14 participants crawled a distance of 305 m each while their breath-by-breath oxygen consumption measurements were taken. Using these data, linear regression models were developed to determine peak and average oxygen consumption rates as well as total oxygen consumption. These models can be used by manufacturers of breathing air supply equipment to aid in the design of devices that would be capable of producing sufficient on-demand oxygen to allow miners to perform self-escape.

Jan 1, 2015

By G. Akdogan, T. P. Kekana, Q. G. Reynolds

The DC arc plasma gasifier concept is currently under development at Mintek for testing the feasibility of producing syngas from waste coal fines and dry steam. The technology is intended for the valorisation of low-grade discard coals into market-quality syngas, which may then be used for largescale electrical power generation to address current grid supply challenges in South Africa. Other potential applications include feedstock for petro-chemical plants, fuel for transportation vehicles, domestic and industrial heating, and others. The proposed concept of a DC arc plasma gasifier was developed based on a plasma torch, metallurgical-based and entrained flow coal gasifiers. The principles of design and operation of the proposed gasifier are based on the concept of the Westinghouse Plasma Corporation (WPC) gasifier where the torches are substituted by graphite electrodes from which electric arc plasmas are generated. The DC section of the gasifier will be designed considering Mintek’s experience in the sealing of the furnace as carried out in the Mintek Thermal Magnesium Process. As part of the building blocks of a full conceptual design, the feasibility of the DC arc plasma gasifier was investigated through testing and modelling of its critical elements as proof of concept. The main activities of this work included pilot scale evaluation of the arc behaviour in the presence of dry steam, modelling of the temperature distribution within the reactor and explosibility studies on three different coal dust samples. Keywords: DC arc plasma gasifier, explosibility index, lower explosion limit, minimum ignition energy

Jan 1, 2020

By Kahmmelly Mathildes Pimenta Coelho, Felipe Dantas, Jaine Ribeiro de Souza, Augusto Ferraz, Carlos Roberto Campos Junior, Davi Bastos Martins de Oliveira

The Carajás Iron Mine, recognized as the largest iron ore province in the world, is notable for its continuous efforts to improve operational efficiency and safety. In response to these objectives, a QA/QC (Quality Assurance and Quality Control) Program was implemented and integrated with Blastscout Probe technology to optimize drilling and blasting processes. The program supports the standardization of operational parameters, the execution of regular audits, and real-time data analysis, facilitating precise and timely adjustments. The implementation led to significant improvements, including an 80% increase in operational compliance, a 49% reduction in drilling depth deviations, and a 30% enhancement in Jaspelite fragmentation. This study presents the methodology employed, the outcomes obtained, and the positive impacts observed in both operational performance and environmental management.

Jan 26, 2026

By Russell R. McLellan

Under the Heavy Metals Program, investigations were conducted at the old Badger dill placer mini in Nevada County California to collect data and information regarding drilling and sampling methods and deposit characteristics. The studies contributed to a team effort by five Bureau of Mines research groups to develop new or improved placer mining technology in the Tertiary gold-bearing channel gravel of northern California. This report describes the techniques used and the results obtained in the sampling and drilling stage of deposit delineation studies that were conducted by the Denver Mine Systems Engineering Group. Sampling included the collection and processing of 400 tons of largo and small volume samples from drill holes, underground workings, surface pits, and blast hole rounds. A total of 355 samples averaging 2,296 pounds per sample provided reasonably accurate data for analysis of the gold distribution. These studies indicate that the bulk of the gold is within 40 foot of bedrock in stacked, lenticular zones of cemented gravel that are largely confined to the relatively narrow, meandering course of the deepest portion of the bedrock channel. Drilling studies involved the testing of three types of truck-mounted drills including rotary, bucket and vibratory, none of which proved to be a completely versatile tool for sampling quickly and reliably both consolidated and unconsolidated gravel.

Jan 1, 2012

By R Austerberry, S Green

The discovery of the Cuffley Lode at Mandalay Resources Costerfield Operations provided an opportunity to extend mine life via mining the offset depth extension of the previously worked Alison Mine. Access from the existing Augusta Mine placed the initial Cuffley underground workings at approximately 250 metres depth from surface. As the new orebody transitioned towards production, a secondary means of egress needed to be established. The depth of the initial capital development presented a challenge in establishing a secondary means of egress that could be confidently relied on. The availability of land to locate a surface shaft collar further reduced available options and geotechnical drilling further limited suitable shaft locations. Time limiting factors such as permitting and having a secondary means of egress in as soon as possible, further highlighted that an innovative secondary means of egress was needed. A consideration of using an emergency gig lowered by a suitable sized crane supplied by an external crane contractor was investigated and found to be a suitable outcome. This Emergency Gig was deployed via the Cuffley Return Air Raise. When trialled, the emergency gig was found to provide a reliable, repeatable extraction method with an acceptable level of risk. Issues discovered during such trials further improved the process to a point where this extraction method became the adopted secondary means of egress for additional lodes that existed at depth. When assessing possible methods of secondary means of egress, the use of a third-party crane and custom designed and fabricated emergency gig should not be discounted. Where a crane can be sourced within an acceptable timeframe, the emergency gig extraction method provides a reliable safe and cost-effective means of secondary means of egress, especially when multiple shafts are to be developed. Local laws may negate the ability to employ such a system, although it is believed with good communication and well-constructed risk assessments, this system can be safely deployed.

Mar 15, 2021

By C. G. Anderson

Industrially proven and applied nitrogen species catalyzed (i.e. NSC) acidic pressure leaching has been utilized to treat a number of ores, concentrates and recycled materials. This versatile technology offers many advantages including low temperatures, low pressures, low capital costs, low operating costs, faster throughput and less costly materials of construction than conventional pressure oxidation. This paper will elucidate the application of this technology for production of gold, silver, palladium, rhodium, zinc, germanium, gallium, cobalt, copper and nickel. Recycled material applications will also be elucidated. In addition, details of an application for treatment of a refractory chalcopyrite copper and gold bearing ore will be presented and pertinent economics discussed.

Jan 1, 2004

By Henry G. Granger

NOTHING in this paper is to be understood as even suggesting a moment's suspension of the splendid work now going forward on the Isthmus of Panama, except so far as it is related to the proposed locks. All the work already done, and all material purchased or ordered, would be available for the plan herein proposed. The situation and the problem concerned may be summarized as. follows : The scheme of a lock-canal through the Isthmus of Panama was adopted, as is well known, on two principal grounds-namely, the greater expense of a sea-level canal, and the longer time required for its construction. Of these, the latter is believed to have been the more influential. But further developments have diminished the weight of both, so that a reconsideration of the question is warranted. It is the purpose of this paper to advocate such a reconsideration-emphasizing the importance of certain objections to the lock-canal not mentioned or not duly appreciated in the report of those members of the International Board of Consulting Engineers who favored this form; showing the nature and bearing of the new facts developed; and, finally, proposing a combination of well-known methods and apparatus, which would, in my judgment, effect the construction of a sea-level canal in less time, and perhaps at no greater cost, than will be required for the remaining work on the lock-canal. I. OBJECTIONS TO A LOCK-CANAL. 1. Earthquakes. Two centuries ago Panama is said to have been destroyed by an earthquake. In 1882 a rather violent earthquake was felt at the southern end of the Isthmus. In 1898 I felt a slight shock near the present border-line of Colombia. In 1900 I felt three shocks at Quibdo, the head of navigation of the

Jan 1, 1909

By P. J. Colbassani

Samples of mine atmospheres collected by Federal coal-mine inspectors during their inspections and investigations of coal mines, in accordance with provisions of the Federal Coal Mine Safety Act (66 Stat. 692; 30 U. S. C., sees. 451-483) are analyzed routinely by chemical methods at Bureau of Mines laboratories. When samples collected in open workings of nongassy coal mines at points not less than 12 inches from the roof, face, or rib contain 0.25 percent or more methane, the act requires the operator, during operation of such mine, to comply with the provisions of sec. 209, Title II, of the act, which pertain to gassy mines. The methane con-tents of such samples are determined by a physical method based on infrared absorption spectrometry to provide an independent check on analytical results obtained by chemical methods. This information circular describes the equipment and procedures used by the Bureau for determining low concentrations of methane in coal mine atmospheres by infrared absorption spectrometry. ACKNOWLEDGMENTS The authors are indebted to Dr. R. A. Friedel, Chief of Spectrometric Section, Branch of Coal-to-Oil Research, Bureau of Mines, for suggesting the analytical method and for furnishing valuable advice and assistance, and to J. A. Queiser of his staff for making exploratory measurements by this method; to Dr. M. G. Zabetakis of the Division of Explosives Technology for his assistance during the conduct of preliminary experimentation; and to L. B. Berger, Chief, Branch of Health Research, under whose guidance the equipment was procured and the work conducted.

Jan 1, 1958

By Kul Bhushan

This paper presents the results of lateral load tests on 0.61-m to 1.27-m (24 to 50-inch) diameter drilled and cast-in-place piers in San Diego area residual/formational soils. The test piers were installed and tested in the following soils: Decomposed Granitic Rock (Ktd), Stadium Conglomerate (Tst), and Friars Formation (Tf). Lateral loads of up to 845 KN (190 kip) were applied to the piers in residual granitic soils, and loads up to 1780 KN (400 kip) were applied to the piers in Stadium Conglomerate and Friars Formation. The tests were conducted by jacking against adjacent piers and monitoring the lateral load and lateral deflection at the ground line. Test results indicate that ultimate lateral pile capacities of up to 1800 KN (400 kip) can be obtained for 0.61 m (24-inch) drilled piers with penetration of 3 to 6 m (10 to 20 ft) in the residual/formational soils tested. Lateral load analyses using p-y curves for very dense sand significantly overestimate the observed lateral deflections. For lateral load analyses using dense sand p-y curves, p-multipliers that increase the lateral soil stiffness (p-y curves) by 2 to 8 times are required to match the load-deflection behavior measured in the test piles. When applied to the dense sand p-y curves, the p-multipliers provide a more accurate prediction of load-deflection behavior in the residual/formational soils, and can result in shorter required pier penetration and significant savings in foundation cost.

Jan 1, 2002

By J. Bilant, B. Carlson, N. Gow

"High-pressure grinding roll (HPGR) technology was evaluated to replace tertiary cone crushing at Coeur Rochester operations (Coeur Rochester Inc.) as an opportunity to improve silver recovery. In 2016 and 2017, onsite and third-party pilot programs were initiated to evaluate the impact on metallurgical recovery and heap leach performance of crushed product generated by an HPGR. In 2018, Forte Dynamics evaluated the HPGR laboratory metallurgical data from Coeur Rochester and all third parties to develop field-scale leach curves based on new crushing scenarios. The laboratory recovery test work data were consolidated and scaled to field conditions to determine projected heap leach performance. Based on the metallurgical testing conducted, the replacement of current tertiary cone crushers with HPGR technology has the potential to increase Coeur Rochester’s silver recovery rate by 8 percentage points, from 61 percent to 69 percent, and shorten the overall timing of silver recoveries from 20 years to just more than two years.The Rochester Mine, and associated valley fill heap leach facilities is an openpit silver and gold mine located in Pershing County, NV, approximately 42 km (26 miles) northeast of the city of Lovelock. In 2017, Rochester produced approximately 4.7 million oz silver (Ag) and 51,000 troy oz gold (Au). Ore mined at Rochester is either fed directly to the primary X-Pit crusher, crushed at an in-pit crusher system, or placed directly onto a heap leach pad as run-of-mine (ROM). Both crushing circuits are comprised of three stages of crushing to produce a nominal 3/8 in. ore. Primary crushing consists of jaw crushing while secondary and tertiary crushing are composed of varying cone crushers.Historical recovery rates of crushed Rochester ore averaged 61.4 percent Ag and 95.9 percent Au over a period of 20 years (Robinson et al., 2018). These rates were derived from third-party verification of in-house metallurgical test results, crusher production and heap leach production results from 1986 through 2004 in a private report for Rochester produced by KD Engineering Co., Inc. Recovery rates are regularly verified by compositing daily samples of ore delivered to each leach pad from the X-pit crusher, in-pit crusher and/ or ROM. A proportionate split of each sample is used to generate monthly composites for metallurgical analysis utilizing column leaching and bottle roll leaching. These tests are run in a manner analogous with production conditions and deliver test results that provide expected heap leach performance. As the Rochester oxide deposit has been mineralogically and metallurgically consistent, the gold and silver recovery trends have also been consistent over the life of the project."

Sep 1, 2019

By Jincheng Hu, Honggang Zhong, Qijie Zhai, Congsen Wu, Cheng Zhang, Jingzheng Ye

"The influence of cooling intensity on the solidification structure and ferrite phase content of a new duplex stainless steel (DSS) was investigated by using a thermal simulation setup for continuous casting. The results showed that the characteristics of the solidification structure were similar to their industrial scale manufactured slabs, including chill zone, colunmar zone and equiaxed zone. And austenite morphologies were mainly primary and secondary Widmanstatten sideplates as well as intragranular Widmanstatten plates. In addition, it revealed that the ferrite content increased with an increasing distance from the chill surface and decreased at colunmar to equiaxed transition (CET) position, then the value remained relatively stable at equiaxed zone. Furthermore, the ferrite content presented the same trend with the cooling intensity ranging from 100 mL/min to 2000 mL/min with the values just varying in a slight range.IntroductionThe duplex stainless steel (DSS) is the kind of steel that ferrite phase and austenite phase occupy about 50% respectively, or the content of the fewer phase has to be more than 30% [l]. The success of modem duplex stainless steels is to a large degree due to their higher strength than austenitic stainless steels, higher toughness than ferritic stainless steels, good weldability and high resistance to stress corrosion cracking as well [2,3]. The cost of stainless steel production continues to soar in recent years due to the increasingly higher price of Cr. In order to decrease the production cost, a new type of duplex stainless steel was developed by Bao steel [4]. This newly developed duplex stainless steel had low Cr content compared with 2205 DSS, and was expected to be applied into automobile industry. However, this type of steel was still in the initial stage of development, and the influence of continuous casting process on its solidification process and structure was still unclear, which needed to be studied further. Several works published in literature presented the effect of continuous casting conditions on duplex stainless steel (DSS) 2205, 2304 [5,6]. It was discussed that the cooling intensity in the chill-side had little efficient influence on the phase transformation. In this paper, the effect of cooling intensity on the solidification structure and ferrite volume fraction of this DSS at a given cooling rate was investigated."

Jan 1, 2014

By David A. Monaghan

This report describes the results of a 2-year investigation of extensible face ventilation techniques and systems for use at the working face in underground coal mines. The goal was to provide a safe and convenient method of maintaining the extensible system within 10 feet of the face, thereby ensuring good ventilation. A summary of approximately 20 extensible ventilation systems proposed or tried in the past is included for reference, together with a detailed description of the design, construction, and underground testing of a new extensible brattice panel and a new fiberglass duct system. The extensible brattice system utilized a special panel which could be pushed forward as the miner advanced. Brief testing in three mines revealed some conflict with the mining cycle and led to recommendations for two improved designs. The extensible duct system was designed for a Goodman borer and utilized a telescoping tube on the left side of the roof, so that it could be extended without interfering with the miner operator. For mine sections with right-hand return ventilation, a special flat tube section is used to cross over the entry. Underground testing showed substantial improvement in face ventilation without interfering with production.

Jan 1, 1976

By E. K. Stanek

This report contains the results of an investigation into the feasibility of periodically measuring parameters of the insulation for a mine electrical power system in order to detect incipient faults. The variety of insulation parameters evaluated included insulation resistance, dissipation factor, power factor (vs. applied voltage), current harmonics, leakage current, infrared radiation, as well as certain circuit breaker parameters and tests. In order to augment field tests a program of accelerated life testing was also carried out. Apparent inconsistencies in data were identified as the result of environmental effects, primarily temperature and relative humidity. A series of environmental tests were conducted to develop correction factors that allow one to refer measured parameters to standard conditions. A portable data collector was develop-ed to aid in the accurate collection and analysis of laboratory and field data. The primary conclusion is that insulation deterioration can be measured and failure predicted with reasonable confidence. The secondary conclusion is that most of the tests are impractical in the field although useful in the laboratory. Infrared sensing, insulation resistance and dissipation factor are the best insulation field tests when portability is taken into account.

Jan 1, 1979

By William K. Cunningham

The investigation described in this report was begun as part of the Bureau of Mines progress to develop acid processes for the extraction of alumina from low-grade bauxite and. clays. A domestic shortage of high-grade bauxite sui table for treatment by the Bayer process became acute as a result of' World War II; an intensive search for a practical acid process using lower-grade alumina-bearing raw materials was therefore warranted. The laboratory development was described in a preceding Bureau of Mines publication wherein the basic theory for the design and erection of a pilot plant maybe found. A 2-ton-per-day continuous pilot plant was constructed and successfully operated at College Park, Md., which demonstrated conclusively the chemical and mechanical feasibility of a solvent purification process for aluminum sulfate. The estimated production cost of $38.64 indicates that under present market conditions the process would not be economically feasible.

Jan 1, 1948

By Jon G. Bredeson

A survey of electromagnetic noise reports was performed and a summary of the results are given. Industrial concerns were surveyed for techniques to minimize the effects of electromagnetic noise and are presented. The common types of communication links used in mines today are presented. A mathematical development was presented which determines the probability of bit errors versus distance for various types of communication links designed for in mine use. The probability of undetected errors for the protocols of the communication links is given together with burst error detection.

Jan 1, 1981