Search Documents

By Donald Koch

The project investigated regional impacts of mining on the ground water system of the Powder River Basin by: 1) establishment of a regional ground water monitoring network. and 2)development at a set pit digital computer models to simulate ground water flow and quality, ground water contributions to surface water flow and quality (i.e., baseflow), and watershed run-off and recharge. Over 100 wells were monitored for physical and chemical parameters. Data were used as input to the models and for the development of a comprehensive data base. The basin was modeled on a regional and subregional scale using a finite -difference model employing an alternating difference technique. Two water-shed models were evaluated fur their ability to provide runoff and recharge inputs to the basic ground water model. Application of the regional and subregional models using conservative mining scenarios showed that drawdowns may extend west from the mines as far as ten miles but that impacts would be insignificant on a regional scale. The watershed model could be effectively applied to small watersheds only.

Jan 1, 1982

By AJ Rorke, JD Botes

Presplit blasting in strip mines is aimed at creating a safer wall to work under during the coaling operations. Good quality presplits are also necessary for effective throw blasting and drainage of the blast block. A less obvious but important function is full coal recovery. Optimum Colliery has been experiencing rock freezing against the presplit highwalls. The rock formed in patches along the highwall and trapped coal beneath it. The material that was &ozen comprised the rock between the back row of holes and the presplit and was often up to 3 m thick (the stand off distance between the back line and the presplit). The cozen rock formed predominantly along the bottom halfor bottom two thirds of the highwall. Along the top portion of the highwall, the presplit crack was usually well formed with visible barrels. This problem, or similar variations of it, is common on many South African strip-mine operations. Investigative work was carried out at Optimum Colliery to correct the problem. This paper presents the information and measurements that were made and discusses the solutions that have been applied to solve the problem. It was found that there were two independent causes for the tiozen material, with each contributing more or less to the frozen rock along the highwall. It was found that the presplit was not forming properly in places, especially closer to the bottom of the highwalls. The reasons and the solutions are presented. The second cause was found to be associated with reduced detonation velocity in the back line holes coupled with low confinement from long delay periods. Emulsion explosive that is sensitised with air bubbles was found to be prone to this phenomenon near the back of high-energy blasts. A change in the explosive formulation in the back-line holes, together with reduced delays in the back line, has resulted in significant improvements. The details are presented in this paper.

Jan 1, 2000

By Michael S. Wieland

Charge malfunction problems result from rather universal damage mechanisms and are widespread throughout surface and underground delay blasting. Recent refinements in instrumentation technology reveal a range of charge performance difficulties, not just outright misfires. This report focuses on the U.S. Bureau of Mines research regarding desensitization and malfunction of delay detonators and cap-sensitive explosives, utilized in underground coal mining. Delay blasting generates tremendous shock waves and rifting forces that fracture and heave the surrounding stratum. The shock waves from charge explosions propagate outward in all directions through the coal, impacting neighboring charges with later delays. The impact phenomena have debilitating effects, causing degrees of reduced charge performance ranging from misfires or weak detonations to out-ofsequence detonations. Impaired charges react poorly. fracture less coal, and produce fumes with higher toxicity. Coal-mine, underwater, and simulator tests were conducted to m3re thoroughly understand the shock-wave and rift-compression damage mechanisms. Recently the U.S. Bureau of Mines partially resolved the malfunction problem by demonstrating the feasibility of formulating a rugged explosive, which could pass the requisite tests for certifying an underground coal-mine explosive. The charge formulation was not certified only because it lost initiation sensitivity too quickly from natural aging and had to be rebatched to finish the testing.

Jan 1, 1994

By Sean Gallagher

The vast majority of ergonomics research has addressed the demands of work in standing or sitting postures, and understandably so. However, many workers (for example, underground miners, aircraft baggage handlers, plumbers, agricultural workers, mechanics, and others) are often required to adopt postures such as kneeling, stooping, squatting, or lying down for significant periods of the work day.

Jan 1, 2005

By A. R. T. Denues, A. P. Rowles

"INTRODUCTION Summarized data developed by J. E. Crawshaw and E.J. Murphy, 4/of the Explosives Division of the Bureau of Mines, suggesting marked variations in oxygen condition in three permissible explosives, have been reported 5/. Such variation is of interest in other work, it having been shown, for example, that the oxygen condition may have marked effect upon the products 3/ and the propulsive strength 7/ of explosives. It seemed that a more detailed presentation and more usual statistical analysis of these data might be of considerable general interest and not complemented in the literature.This report presents both the original data developed by Crawshaw and Murphy and the results of a simplified but seemingly acceptable statistical analysis of these data. The logical ground for this analysis might seem somewhat questionable because of the lack of systematic information concerning the extent of errors in the analytical procedure but the data show that there are several cogent and seemingly unequivocal indications of real heterogeneity in the explosives."

Jun 1, 1942

By D. S. Choi

This paper describes an improved source location technique for microseismic events related to coal mining. A system of non- linear distance equations is solved with the use of the Newton-Raphson method. This computational method is- advantageous when the number of geophones is limited. In addition, this paper includes the results of the analysis of data from several instruments which characterize both mine seismicity and environmental noise such as vehicle traffic. Analysis of the mine seismicity has contributed to a better understanding of caving above a longwall gob and of what constitutes stable ground conditions.

Jan 1, 1990

By David Caiden, Petros Fortsakis, Alan Hodgkinson

"1. INTRODUCTIONDo contractual practices affect project outcome? Can better contractual practices improve the likelihood of project success? The consensus amongst experts is that better contractual practices really do improve project outcomes. With this in mind the members of the International Tunnelling Association (ITA) Working Group 3 on Contractual Practices (WG3) pooled their collective knowledge to publish in 2011 the document entitled The ITA Contractual Framework Checklist for Subsurface Construction Contracts (ITA Working Group 3, 2011). Written for projects involving significant subsurface works, e.g. tunnels and caverns, the ITA Framework Checklist explains the major contractual issues that must be considered to ensure a successful project. Its goal is not to specify how each issue should be resolved, but rather to highlight the issues and give recommendations on how they should be addressed. The Checklist is compatible with, and provides guidance for reviewing, standard contracts such as FIDIC and NEC. One of the authors is a co-author of the Checklist and has contributed to previous papers describing the Checklist and its applicability to hydropower projects (Hodgkinson & Wilson 2014, Hodgkinson & Wilson 2015). The Checklist identifies a series of issues that should be contractually defined, which can be summarized as follows: •,Methods for dealing with geotechnical uncertainties should be defined in the contract •,There should be an appropriate level of geotechnical/geological investigation •,Sufficient mobilization periods should be allowed •,Sufficient time should be allowed for testing and commissioning •,Procedures for timely dispute resolution should clearly defined •,Quality and performance requirements should be clearly defined and measurable •,Provision should exist for cost consequences of unforeseen circumstances •,Dispute resolution processes should be clearly defined •,Payment processes should be fair and clearly defined •,Risk should be clearly allocated and parties should be able to bear the risks they carry •,There should be a mechanism for adjusting payments according to conditions •,The risk management approach should be clearly defined •,Admeasurement or unit price approaches are recommended •,The responsibilities of each party must be clearly defined •,The consequences of non-performance should be clearly defined •,The construction programme (schedule) should be realistic."

Jan 1, 2016

By John F. Beesley

INTRODUCTION This paper discusses the design of the subsurface nuclear waste repository at Yucca Mountain, Nevada; and possible concepts for construction of the subsurface facility. Subsurface construction at Yucca Mountain is planned to last for 20 or more years, and may be accomplished using tunnel boring machines (TBM), drill and blast methods, raise bore machines, and roadheaders. The design of the subsurface facility includes approximately 107 km (66 miles) of tunnels and drifts. The vast majority of the repository will be excavated with TBMs. Design and construction concepts for the subsurface repository discussed in this paper are based on the License Application that was submitted to the U.S. Nuclear Regulatory Commission (NRC) by the U.S. Department of Energy (DOE) on June 3, 2008. The License Application was subsequently docketed by the NRC in September 2008. When a Construction Authorization is received from the NRC, notices to proceed with subsurface construction at Yucca Mountain will be issued by DOE. The Yucca Mountain site is located in the Mojave Desert approximately 150 km (90 miles) northwest of Las Vegas, Nevada. The site is on federal land in southern Nevada and is shown in Figure 1. Yucca Mountain is a ridge of volcanic rocks com-posed primarily of solidified volcanic ash. Previous underground construction work at Yucca Mountain included excavation of two tunnels using two different TBMs. The first tunnel, the Exploratory Studies Facility (ESF), is a 7.62 m (25 ft) diameter tunnel that is 7,877 m (25,843 ft) long and was described by Morris and Hansmire at the Rapid Excavation and Tunneling Conference (RETC) in 1995. The second tunnel, known as the Enhanced Characterization of the Repository Block (ECRB), was a TBM drive of 5.0 m (16 ft, 5 in.) in diameter and 2,681 m (8,796 ft) long. The second tunnel was excavated in 1998 and was described by Fulcher, Eastlund and Copeland at RETC 1999 and is named the East?West Cross Drift in that paper. (These previously excavated tunnels are shown in Figure 2.) In the volcanic rock formation where the vast majority of the planned repository will be con-structed, previous tunneling conditions were generally very good.

By Michael S. Contratto, Dave Marshall, Tom Brodersen

The European Union (EU) completed a new directive 2002/44/EC1 called the Physical Agents Directive (PAD) that establishes action and limit values for hand-arm and whole body vibrations. The directive specifies that: “…workers shall not be exposed above the exposure ‘limit value’.” 1 and “…once the exposure action values … are exceeded, the employer shall establish and implement a programme of technical and/or organisational measures intended to reduce to a minimum exposure to mechanical vibration and the attendant risks…” 1 The PAD limit value is effective for new machines starting July 6, 2007 and for used machines by at least July 6, 2010. These requirements apply to the users of machines, but machine manufacturers will be challenged to provide machines and information to help the users comply with the directive. Caterpillar manufactures machines with the goal of enabling our customers to comply with all regulations dealing with health and safety. Caterpillar designs all of our machines to provide a safe, comfortable and productive work environment. This study was to determine if seat suspensions could provide a reduction in the vibration environment experienced by operators of Caterpillar mid sized (<50,000KG) Track Type Tractors Methods Seat manufacturers were asked to provide seat suspensions that provide improved isolation over and above current seat suspension. Each supplier was provided with ride profiles and was asked to demonstrate the vibration reduction on a shaker table. Two suppliers provided suspensions that were compared with the current seat suspension in a field study. Three full factorial experiments were conducted. The first experiment was to evaluate overall suspension performance for four operations. The second experiment was to determine the benefit of the adjustable vertical damper at three different levels and the third experiment was to determine the effect of the fore/aft and side/side isolators. Six operators were used for the study. Acceleration was measured at the seat base and at the operator seat pad. Both the transfer function and the ISO 2631 RMS ride values were used to determine the seat suspension’s effectiveness of isolating the operator from vibration. A structured questionnaire was used to determine the operators’ subjective assessment of the seat suspensions. Results There was significant operator-to-operator variability in the vertical direction (>35%), however there was little variability in the fore/aft and side/side direction based on seat base

Jan 6, 2006

By Thomas M. Keevin, Gregory L. Hempen

Accurate assessment of blasting near an object (organism or structure) requires recording of the damage parameter for low-valued scaled distances. Seismograph recordings of particle velocity are a well established, common procedure for land-based blasting. Similarly, pressure recording of the absolute waveform needs to be a more common procedure for sensitive, underwater resources.

Jan 1, 1997

By Chen Xizhe

The caisson is adapted to the foundation of concentrated heavy building. As there are the flowing sand, boulder or cobble and other serious obstruction, the open caisson can&apos;t sink, the caisson can solve these problems easily. Especially for the stability of the neighour building, the merit of the caisson is outstanding. Therefore, there are the pier, the foundation of heavy instrument and the large water pumping station etc. using the caisson in China. This paper introduce several caissons and successful experience by author&apos;s investigation. It contains the feature and application of the caisson : the examples of caissons such as a huge pier of a bridge acrossing a big river, a large instrument foundation and a large water pump station beside a river; the problem of the design of the caisson and notice items during the caisson construction etc.

Jan 1, 1991

By W. M. Merritts

The control of coal dust created and released during the operation of continuous mining machines in bituminous-coal mines of the United States is a problem. The interest manifested in this problem indicates the seriousness of the hazards involved, particularly when the dust has not been abated at its source and has become air-borne. Officials of the Sunnyside No. 1 mine, Kaiser Steel Corp., were confronted with the problem of abating the coal dust created by operation of a recently installed continuous-mining machine, and they requested the aid of representatives of the Coal-Mine Inspection Branch, Bureau of Mines, United States Department of the Interior, in developing an effective method of allaying the coal dust at its source.

Jan 1, 1951

By Christophe Bragard, Brett Robinson

This paper reflects the challenges encountered during the construction of the light rail tunnels under Boyle Heights, in Los Angeles, California. Equipped with two state-of-the-art EPB TBMs, the construction team undertook the mining of twin bored tunnels in the Los Angeles alluvium. The gassy underground conditions dictated many aspects of the design of the tunnels, as well as the tools and means used for their construction. This paper will detail the challenges encountered during construction, as well as the means, methods and logistics used on the project. Discussion includes: EPB TBM machines with some very unique/specific features; complex assembly sequence due to limited shaft access; final precast concrete liner with double gaskets; NATM cross passage excavation in soft ground and below the water table; compensation grouting; mucking shaft arrangement.

Jan 1, 2007

By K. D. Mills, R. G. Robins, C. G. Anderson, L. G. Twidwell

Arsenic is a metalloid which has attracted great environmental scrutiny in recent decades. Moreover, its control and deportment is becoming increasingly important in the metallurgical processing of modern complex ores and concentrates. As such the authors of this publication have a combined professional experience of well over 100 years in the study and hydrometallurgical treatment of arsenic. Hence, this paper will cover arsenic fundamentals along with a review of technology for removal, fixation and stabilization. Finally, an application of industrial Alkaline Sulfide Leaching (ASL) of a copper enargite concentrate will be elucidated.

Jan 1, 2014

By V. Coetzee

Keywords: Pyrometallurgy, furnace, PGM, platinum, nickel, copper, electric smelting, six-in-line, Peirce-Smith, Impala Platinum In 1992, a paper was compiled highlighting a common-sense approach to electric smelting at Impala Platinum. Since then, the smelter complex has undergone considerable changes. Mineral economics, UG2 exploitation, and changing environmental legislation have enforced numerous process upgrades, yet a common-sense approach has always been adopted. This document details the major changes in the smelter complex at Mineral Processes (Minpro) over the past 15 years, and provides the rationale for the changes.

Jan 1, 2006

By N. Ahmed

The collection of hydrophobic particles in the froth phase in flotation has been studied. A continuous flotation cell was developed, in which the froth phase could be isolated from the pulp zone. Hematite particles, d80 = 87 µm, were floated in the pulp, using a conventional oleate collector, while glass spheres of similar diameter, d80 = 82 µm, were introduced in wash water added to the froth. Four samples of glass spheres, with contact angles between 0 and 82 degrees, were used. The results indicate that the efficiency of collection of the hydrophobic particles in the froth can be very high. The process is strongly influenced by the hydrophobicity of the particles and the surface area available for attachment in the froth. Recommendations for the flotation of particles in the froth phase are made, especially regarding the desirable hydrophobicity as reflected in the contact angle, the froth depth, the solids concentration in the feed to the froth, the air rate and the wash water rate.

Jan 1, 2001

Bacterial Leaching of Complex Polymetallic Sulfide Ore The work described here concerned the study on bacterial leaching of complex sulfide minerals and polymetallic ores operated in shaken flasks and small-scale columns. The bioleaching of jamesonite was not accessible. The iron extraction in pyrrhotite leaching reached 98.2 per cent after 23 days. After 26 days, the zinc extraction of marmatite reached 92.3 per cent while the iron extraction only reached 13.6 per cent. The pulp density had effect on the metal extraction of pyrrhppite and marmatite. For complex polymetallic sulfide ores, after 10 days in shaken flasks, 97.1 per cent zinc extraction was achieved. While after 60 days in small-scale column, the zinc extraction only proceeded to 7.8&nbsp;per&nbsp;cent; By SEM and EDXA of experimental samples and their leaching residuum, the bioleaching mechanism was discussed.

Sep 13, 2010

Measurements from an old survey are being machine processed as a pilot project in the development of a computer-assisted method of structural mapping in shield areas. The key element in the system is a field data sheet which requires the geologist to determine a textural hierarchy in each exposure. The pilot system is limited to orientation analysis and utilizes a prior textural analysis, but this would not usually be a problem in utilizing the system ab initio for exploration. A data processing system of this general type offers promise of considerably increased productivity of field geologists by reducing compilation time and improved technical supervision through centralization of processing, and would make structural analysis an economically viable tool in mining exploration and development.

Jan 1, 1969

By V. M. Troughton

Large diameter bored piles with grouted bases have been adopted for the foundations of the majority of the buildings at Canary Wharf in London&apos;s Docklands, including a deep basement car park. The piles are founded in the Thanet Sand which forms part of London&apos;s aquifer where water levels are reported to be slowly rising. A special pile test has been carried out to determine the effects of both the basement excavation and a possible long term rise in the groundwater level on the performance of base grouted piles. These effects were simulated by injecting water around the pile toe and thus reducing the vertical effective stress. In this paper the test layout and procedures are described and the results are presented. The test results showed that the reduction in pile base resistance under increased water pressures was less than predicted by conventional design methods based on vertical effective stress. The end bearing resistance was found to be proportional to the mean effective stress.

Jan 1, 1989

By M Pernechele, U König

Most of the operating steelmaking capacity currently relies on conventional, coal-based steelmaking processes. Currently, direct reduced iron (DRI) is only produced in regions where energy is available at low cost. To align with net-zero emissions goals, steelmaking capacity must transition to loweremissions steelmaking technology. Direct reduction of iron ore will get one of the preferred methods in the future due to its high technology readiness. New reduction technologies include hydrogenbased direct reduction processes. To ensure optimal efficiency during DRI production and to cope with newly developed technologies, processes need to be monitored more frequently and accurate. Traditionally quality control of raw materials and DRI has relied on time consuming physical testing, wet chemistry or the analysis of the elemental composition. The mineralogy of DRI that defines its properties is not frequently monitored. Process monitoring and quality control of DRI is possible by using modern X-ray diffraction (XRD) methods. In addition to the metallic iron content (Femet), metallisation (Metn) and the total carbon content (Ctot), XRD analysis also identifies the overall mineralogical phase composition. This allows additional information about the reduction process and enables fast counteractions on changing raw material mixtures. The benefits of the quantitative determination of the phase composition and the calculation of process critical parameters to produce DRI will be demonstrated with a case study

Sep 18, 2023