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By R. J. Pine, J. S. Coggan

Distinct-element modelling has been used to study the mechanisms associated with observed deformation of the western face of the quarry. A complex failure mechanism involving distinct planar surfaces that was proposed for a slope failure in 1967 has been modelled and shown to be plausible. In addition, deep-seated flexural toppling may contribute to the slope instability. Modelling has confirmed the detrimental influence of a raised water-table on the stability of the slope and also indicates that the observed cyclic opening and closing of tension cracks may be attributed to seasonal rise and fall of the groundwater level

Apr 1, 1996

Numerical modelling was used to examine priming of bulk commercial explosives. Data for the HOM equation of state were calculated using a representative chemical composition, while Forest Fire model data were calculated, using a Pop plot which was estimated on the basis of existing sensitivity data, albeit for cap sensitive, small diameter explosives. The length and diameter of the primer, the location of the detonator in the primer and the shape of the primer form a set of parameters which are investigated. The effect of confinement and borehole diameter are also demonstrated, as reflections of shock waves create regions of high pressure in the explosive. The results are presented in terms of pressure and decomposition histories in the explosive and are interpreted in an engineering fashion to form rational suggestions for optimization of the priming process in the field.

Jan 1, 2002

By Yongbin Yang

Cathodic reduction of oxygen is a process involved in many fields. As is well known, the mechanism of oxygen reduction usually varies considerably with electrode substrates. In this paper, cathodic reduction of oxygen on gold electrode was studied by linear sweep voltammetry with regards to cyanide leaching of gold. As the results shows, the electron transfer number increases as potential shifted negatively and decreases as pH value increases. Besides, the increment of electron transfer number as a function of potential decreases when pH value increases. When pH increases to 13.0, the volt-ampere curve exhibits a relative flat section with currents approximate to the limit current density of a 2e process. By varying dissolved oxygen concentration, the electron transfer number was calculated for pH11.0 at different potentials, the results being 2.387e, 2.732e, 2.982e, and 3.227e at, -0.35V, -0.40V, -0.45V, and 0.50V, respectively. The calculated current densities are in good conformity with measured results.

Jan 1, 2010

Rockbursts continue to be a scourge in the mining industry, being responsible for accidents and damage to mining excavations. Although the problem has been present for more than a century, and although much research has been carried out, a solution is still elusive. Determination of, firstly, the demand on the support system imposed in the rockburst and, secondly, the capacity of the support system, cannot be carried out with any confidence, and therefore rockburst support cannot be designed using a conventional design approach. In contrast with the conventional approach, observations of rockburst damage in a mine have revealed a possible alternative approach to rockburst support ? sacrificial support. It was observed, in rockburst events, that a support system consisting of concrete panels restrained by grouted cables was destroyed, and the concrete panels were ejected. However, the rock behind the panels remained apparently undamaged and in place. This behaviour reignited the concept of sacrificial support, conceived more than 20 years ago, and which is described in this paper. The remedial solution implemented on the mine, involving cables wrapped over the panels and retained by grouting into boreholes, has been subjected to rockburst loading and has confirmed the validity of the sacrificial support concept. The concept of sacrificial support may be controversial, but is deliberately presented here with the aim of generating discussions and contributions, and with the ultimate aim of improving safety and reducing rockburst damage in mines. Keywords rockburst, seismicity, seismic waves, rock support, support design.

Jul 1, 2013

By Andre Zingano

The objective of this paper is to compare the behaviors of different types of roof bolts: (1) One-Step Bolt (OSB), (2) Fully grouted Bolt (RB), (3) Combination Bolt (CB), and (4) Torque tension Bolt (TB). Two dimensional numerical models were built for both bolted and unbolted roofs. The geological sequence and rock properties used in the numerical models represent the typical roof condition for Pittsburgh coal seam. Using the unbolted roof as a base case, a comparison is conducted by monitoring the roof vertical displacement at the center of the entry and at the bolt positions, the axial force in the roof bolts, and stress distribution in the bolted area. The grout/rock interface is assumed to be perfect. The estimated roof displacements showed that the differences among the four types of roof bolts are small. The major differences are in the shear stress at the grout/rock contact and in the shear stress along the immediate roof bedding interface as well as in the bolt axial stress. There is less axial stress for the OSB compared to RB and CB as the diameter of the OSB is much bigger and the contact area between grout and rock is twice as large as for RB and CB. The higher strength of the OSB contributes to keep the bedding planes in the roof closed.

Jan 1, 2007

Rock mass classification systems are extensively used in rock engineering design work, and mine design is no exception. Among the systems most widely used for mining-related design work are the NGI 0-system (Barton et al., 1974), the RMR system (Bieniawski, 1976), the MRMR system (Laubscher and Taylor, 1976) and, more recently, the GSI system (Hoek et al., 1998). Classifying the rock mass is widely seen as being the fieldwork required to characterize the rock mass and enable the application of empirical design methods associated with the different classification systems. This paper argues that it is fundamentally important to recognize the distinction between rock mass characterization and rock mass classification. These two processes should, in most cases, be separated from each other. Rock mass characterization should be used to determine the intrinsic properties of the rock mass independently of the application; i.e. independent from the infrastructure to be designed, the size, shape, and orientation of the excavation(s) or pillar(s), etc. Rock mass characterization should also be compatible with most classification systems and empirical design methods to be used. Rock mass characterization is the background fieldwork required to perform rock mass classification and/or engineering design work. Rock mass classification is the subsequent step to the characterization, and an integral part of the design process. Parameters that vary according to the design, such as the relative orientation of geological structures compared to the opening or the mine-induced stresses, should be calculated as part of the rock mass classification and design process, rather than during the rock mass characterization process. The failure to distinguish between rock mass characterization and rock mass classification can lead to major design errors and poor results.

Jan 1, 2012

By AIME AIME

AMERICAN participation in the World Engineering Congress in Japan will be generous. Nearly seventy papers have been prepared and for- warded for printing and the A. I. M. E. is well represented in the list. At our San Francisco meeting four of these will be briefly reviewed by the authors for the benefit of those who are unable to go on to Tokyo. They constitute a group dealing with the present economic status as seen by engineers of the world's iron, coal, petroleum and non-ferrous metals. Messrs. Leith, Smith and Tryon, Requa, and Probert have written papers that constitute a notable series. Messrs. Jeffries, Sweetser and Kinney, and other Institute members have written papers dealing more closely with technologic progress. The latest list of delegates and members is printed below, names of A. I. M. E. members being set in italics.

Jan 1, 1929

The efficiency of water sprays in suppressing airborne colliery dust depends on many variable factors. A survey of previous work in this field shows that swirl spray nozzles are the best dust suppressors.Investigations carried out in an experimental dust chamber show that, in spite of limitations to the application of water sprays in underground use, promising dust suppression efficiencies in mechanised mining can be obtained with swirl spray nozzles.INTRODUCTIONA dust hazard has always been associated with coal mining, and the recent growth of mechanisation has resulted in a greater production of fine coal and dust, thus increasing the hazard. A better knowledge and appreciation of the medical aspects and dust explosion factors has led to practices reducing the seriousness of the problem. However, the dust hazard still exists and its control is basically an engineering problem.Dust, as with any atmospheric pollution, may be removed from the, mine by ventilation, which is an indirect method of control. Direct methods, in which the dust is prevented from being produced and from becoming airborne, should be employed where possible. Of these direct methods the most significant is the use of water sprays.THE DUST HAZARDAn appreciation of the physical nature of the more important dust hazards is necessary before considering the removal of the hazard. The main hazards associated with colliery dusts are the health hazard and the explosion hazard. "Dust" comprises solid particles of size minus 20 mesh Tyler (833 microns).

Jan 1, 1964

By T. M. Barczak

Stoppings are required to resist lateral forces on the face of the structure to control pressure differentials created by ventilating air. The design criteria in other parts of the world, including Australia, exceed this requirement by specifying over pressurization control to as much as 14 kPa (2 psi) in the active sections and 35 kPa (5 psi) in the main ventilating control areas. This is done to provide protection to the mine workers from explosive or air blast events within the mine that can create this over pressurization. The National Institute for Occupational Safety and Health (NIOSH) has been conducting research to develop a new testing protocol for rating mine ventilation stoppings. The premise of this work is that arch-loading conditions more accurately reflects the transverse load capabilities of stoppings in underground coal mines than the freestanding flexural strength test specified in the current Code of Federal Regulations (CFR). This work clearly shows that the transverse load capabilities of dry-stacked, mine ventilation stoppings are dependent upon the material strength of the block and the height and thickness of the wall, none of which are part of the current CFR criteria based on ASTM E-72 specifications. This paper compares the transverse load capabilities of several block materials and wall dimensions commonly used in stopping constructions based upon simulated three-hinge, rigid-arch loading tests of half-wall constructions in the NIOSH Mine Roof Simulator. The results indicate a wide-range of transverse load capacities, ranging from as low as 21 kPa (0.3 psi) to as much as 117 kPa (17 psi) for the conditions evaluated in this study. The current CFR criteria do not distinguish between applications of these stopping designs despite their wide variance in transverse load capabilities, which is not conducive to employing ventilation control strategies that isolate certain sections of the mine to prevent injury to mine workers.

Jan 1, 2009

The objective of this study was two-fold: 1. To perform a world literature search pertinent to the analysis, selection and design of hoisting systems and their components and to codify the search into a literature compendium. The search resulted in a technical data file of over 1500 hard copy items. The compendium index was also suitable for establishing a comprehensive computer-loaded data base on the subject. 2. To develop a comprehensive system of guidelines to cover salient aspects of analysis, selection and design of electrical, mechanical and structural components of a hoisting system with a view to establish parameters for maximum safety and efficiency of operation, installation and revision of the system. 3. Considerations in the mine shaft layout, design, sinking, outfitting, testing and commissioning are set forth against the background of requirements of applicable parts of Code of Federal Regulations, Title 30.

Jan 1, 1988

By G. M. Cresswell

The 2 360 t/h two module Phola coal preparation plant represents anew era of large plant in the Witbank coalfield designed to extend its life to 2020 and beyond. The plant uses the optimum processing model for Witbank coals, receiving a feed coal size of -50 mm, wet screening it into coarse and small coal fractions 50 x12 and 12 x0.63 mm before processing them in parallel through two primary DM cyclone sections, in order to make a 27.5 MJ/kg export floats product. The sinks are processed through a common high density DM cyclone section to produce a 21.5?23 MJ/kg thermal coal middlings product. The plant design incorporates the largest size DMS equipment used to date in South African coal preparation plants, i.e. 1 150 mm large diameter pump fed DM cyclones and 4.2 m width banana screens. The fine coal is conventionally processed by spirals, whereas the raw coal slimes are filtered using automated plate and frame filter presses and added to either the middlings or discards depending on its quality. The paper describes the database, innovative design concepts, construction, and commissioning.

Jan 1, 2010

By I. J. Duckworth

Due to improved, stringent safety regulations, many modern road tunnels are statistically safer, per kilometer, than above ground roadways. However, the public perception and reaction in the event of a serious tunnel fire is very different to that associated with a surface incident. Vehicle fires in road and rail tunnels are recognized to represent an immediate and extreme danger to the patrons of those systems. Unlike workers in the mining and civil construction industries, the general public are neither trained nor equipped to fight fires or evacuate under deteriorating smoke conditions. Accordingly, for the majority of modern transportation tunnels the ventilation infrastructure is sized on the requirement to control the combustion products from worst-case fire scenarios and to provide a tenable evacuation route for the tunnel users. It is common for these same emergency ventilation systems to be employed, often in a reduced capacity, for other operating modes such as the dilution of pollutants during congested traffic conditions. This is one of the fundamental differences to mine ventilation, where primary ventilation systems are not typically sized based on fire scenarios. This paper presents an overview of the subject of fires in vehicular tunnels. This includes a brief history of major transportation tunnel fires followed by a discussion on the resulting legislation and standards that govern the design and operation of tunnel emergency ventilation systems. A summary is provided on the common criteria, theory, and design techniques that are employed during tunnel emergency ventilation systems design. Information is provided on fire detection and suppression, with a discussion on the growing acceptance of wet suppression as a means to mitigate major fires in road tunnels worldwide.

Jan 1, 2009

The risk associated with mining induced seismicity is one of the major threats to the safety and sustainability of deep underground mines. This paper describes techniques that allow site practitioners to efficiently control such risks in mines. The proposed approaches rely on ground support to strategically control seismic risk and re-entry time to tactically control this risk. The strategic approach is based on the detailed understanding of past seismicity to as certain the seismic hazard of individual sources throughout the mine. This approach also relies on assessing the potential damage that these sources can induce on nearby excavations using the excavation vulnerability potential (EVP) and rockburst damage potential (RDP) concepts proposed by Heal et al. (2006). It is then possible to investigate how to reduce the risk of experiencing damaging seismicity in mine drives by locally enhancing the ground support system. The tactical approach relies on a proposed methodology to estimate reliable re-entry times or exclusion periods based on the seismic decay following blasting. Some examples of how these techniques have been applied in Australian mines are given.

Jan 1, 2009

By A. T. Visser

"SynopsisAlmost 20 years have passed since the cutting-edge research by Thompson and Visser on the design and management of opencast mine haul roads was conducted in South Africa. This system is based on three principles, namely the structural ability to support the ultra-heavy truck loads, the selection of vehicle and environmentally friendly riding surface, and an appropriate level of maintenance to counteract wear and tear. Obviously, proper layout and geometry are essential.These principles have been implemented worldwide, and it is useful to review the lessons learned. The objectives of this paper are to present a critical review of the status of mine haul road design and management, and the impact that these principles have made on operations, particularly the cost-effectiveness. The paper briefly reviews the principles of the haul road design and management and the extent to which they are applicable. Case studies of a number of implementations are presented to demonstrate that the principles are sound and have been applied effectively. For example, at an international operation the transport cost of coal was 40% more expensive than anticipated in the feasibility stage, and this made the mining operation uneconomic. Correction of this problem resulted in a viable enterprise. Although designed for opencast operations, the principles are equally valid for underground operations, and initial development work will be discussed.The main conclusions are that the research approach is valid and its effectiveness has been demonstrated in a number of applications. The anticipated financial benefit has been derived, and has made the mining operations that used the principles more effective. Of major importance is the application of opencast haul road design principles to the future thrust of using driverless vehicles in opencast and underground mining, where the road quality is not negotiable as there is no driver that can avoid obstacles or severe road deterioration.IntroductionAlmost 20 years have passed since the cutting-edge research by Thompson and Visser on the design and management of opencast mine haul roads in South Africa (Thompson and Visser, 1996a, 1996b, 1998, 1999, 2000a). This system is based on three principles, namely the structural ability to support the ultra-heavy truck loads, the selection of vehicle and environmentally friendly riding surface, and an appropriate level of maintenance to counteract wear and tear. Obviously, proper layout and geometry are essential."

Jan 1, 2015

By S. D. D. Welsby

"A pilot-scale flotation column was used to evaluate four polyglycol frothers at Teck’s Highland Valley Copper Mine. The column was fed with flotation plant feed from the grinding circuit cyclone overflow. Frother dosage was changed by controlled addition to the column feed. Pulp, froth and metallurgical performance were assessed using gas dispersion measurements, water recovery and copper, molybdenum and gangue grades and recoveries. Ranking the frothers based on pulp and froth phase performance using gas dispersion measurements and water recovery yielded contradictory rankings. All of the frothers changed the froth structure in a similar manner such that, at the same structural conditions, they all gave the same degree of separation between water and entrained solids. The only difference between the frothers was what dosage was required to achieve a certain structure. Changes in pulp structure appeared to be related to the critical coalescence concentration (CCC) for each frother. Changes in froth structure were not completely described by the CCC and involved other factors, such as the hydrophobicity of particles in the froth. All of the frothers were capable of achieving the same metallurgical result, just at different dosages. Optimal dosages for the frothers were anywhere from the CCC, where copper and molybdenum grades were maximised, to 2 to 3 or 4 to 7 times the CCC, where copper and molybdenum recoveries, respectively, were maximised.INTRODUCTION Background Due to supply issues, Teck’s Highland Valley Copper (HVC) Mine replaced Dowfroth 250C, their auxiliary frother, with Huntsman Polyfroth W31. The primary criterion for selection was that the new frother gave the same performance as Dowfroth 250C, minimising disruption to the circuit. Frothers play a dual role in flotation, altering the bubble size in the pulp zone and the stability of the froth. A stronger or weaker frother, or a blend of both, will alter the balance between pulp and froth effects and, ultimately, metallurgy. Dowfroth 250C and Polyfroth W31 may not necessarily be the best frothers for HVC from a metallurgical standpoint. There may be a different frother or frother blend that could deliver higher recovery in the bulk roughers."

Jan 1, 2014

By Michael J. Rinker, P. A. Tibble, M. Wiseman, R. V. Nicholson

Tailings, from an active copper-zinc operation, containing about 10% sulphur were investigated to assess the onset of acid production and potential lime requirements for treatment of drainage. Oxygen consumption rates were measured over two years to verify spatial and seasonal variations in sulphide oxidation rates. Shallow cores were collected to assess the quality of tailings porewater and to characterize solids that had been subjected to oxidation and depletion of neutralization potential (NP) for several years. Oxygen consumption data were used to quantify rates of NP depletion and onset of acid drainage from the near- surface tailings. Based on measured oxygen consumption rates and identification of NP remaining in the tailings, future lime use in the treatment plant was expected to rise significantly without mitigation. Geochemical modeling calculations were calibrated with observed oxygen consumption rates and the model results agreed well with actual lime use in the waste water treatment plant during operations. The modeling also demonstrated the benefits of lower lime demands and treatment costs after closure as a result of construction a soil cover on the acid generating tailings.

Jan 1, 2000

By Xi Zhang

A technique for fabricating free-standing, high-aspect-ratio porous and pillar-type Ni structures has been developed using wet Si processing. A wafer of (100) Si was initially etched in HF solution to form deep pores with micron-sized diameter. The aspect ratio can exceed 200. By introducing the as-etched Si into a defined aqueous Ni2+ solution, Ni deposits grew rapidly onto the sidewalls and replaced the Si. Long-time immersion allows the Si sidewalls to be completely converted and thus form a metallic Ni structure with high-aspect-ratio pores. It is known that close-packed submicron Si pillars can be formed by oxidizing and subsequent etching of the macropore sidewalls. Treated in the same Ni solution, high-aspect-ratio Ni pillars were correspondingly emerged by replicating the original pillar-type Si structure.

Jan 1, 2006

By Valois R. Shea-Albin

Increasing pressure from State and Federal agencies to mitigate mining-induced subsidence damage to overlying structures has presented a unique problem to the coal industry in the western United States. Because sandstone escarpments are an environmental issue, millions of tons of coal reserves that underlie these escarpments risk being classified as unminable by regulatory agencies. At this time, the effect of subsidence on escarpments has not been well documented or characterized. The Bureau of Mines is using numerical modeling techniques to analyze escarpment response to longwall mining. Two- and three-dimensional finite element models have been constructed for a study area near Price, Utah, where longwall panels were mined near an escarpment. This status report includes preliminary results showing that the pattern of subsidence surrounding the escarpment can be simulated through numerical modeling. Models that include such structural details as joint and fracture patterns will better simulate subsidence patterns .and magnitude. By locating longwall panels strategically in relation to the escarpment, stability may be preserved throughout the mining process. Numerical modeling provides a method to analyze relatively quickly the effects of longwall panel location and resulting subsidence on escarpment stability. The goal is to provide a relatively accurate predictive tool for mine planning to determine if escarpment stability can be maintained while maximizing extraction of the coal reserves.

Jan 1, 1986

By Christopher J. Bise

INTRODUCTION The control of nuisance water in a mine is extremely important; left uncontrolled, nuisance water can have a severe effect on haulage, ventilation, production, and the health and safety of miners. To control water in mines, a four-step process is followed: (1) prevention, (2) collection, (3) transportation, and (4) treatment. This chapter will be devoted to the collection and transportation of mine water because prevention is usually dictated by pre-mining conditions and initial planning, while treatment is variable and highly site specific. A mine drainage system is nothing more than a collection of gathering points (sumps), machines that impart energy to the fluid (pumps), transportation ducts (pipes), and control devices (fittings, valves, etc.). A pump does not pull the fluid up the suction pipe; atmospheric or external pressure pushes the liquid up the suction pipe to the pump. All references in this chapter will be to centrifugal pumps, due to their popularity for mine drainage. PUMP CHARACTERISTIC CURVES The performance of a pump is plotted on a graph as an indication of its characteristic. To develop the data points, a test facility similar to that shown in Fig. 1 is established. The calibrated Venturi meter is used to measure quantity, the Bourdon gage measures pressure, and the wattmeter measures power input. Various discharge pressures are obtained by throttling with a gate valve in the discharge pipe. Quantity and power are measured at each of these pressure levels, giving the necessary data for plotting the characteristic curves. Fig. 2 shows a typical characteristic curve for a centrifugal pump. Notice that pressure is measured as so many feet of vertical water column above the outlet level, or head. Knowing the quantity (in gallons per minute), head (in feet), and power input (brake horsepower), the pump's efficiency can be plotted based upon the following relationship:

Jan 1, 1986

By E. Wasmund

"Sandfire’s DeGrussa Copper-Gold operation in West Australia is a new high grade copper sulfide mine, which includes a 1.5 Mtpa concentrator which was completed in 2013.Early after commissioning, it was identified that the flotation capacity in the all-mechanical cleaner circuit was not sufficient. In order to improve recovery, the tail from the cleaner scavenger was sent back to feed the rougher scavengers. Test-work was done on-site to evaluate the possibility of using a flotation column as a pre-cleaner. A CavTube™ sparging system was selected, which is especially effective for fine ore particle flotation. Test-work was conducted at site using a 150 mm diameter unit, and then confirmed on a 500 mm diameter unit. A 4250 mm diameter full scale unit was installed in Q4 2014 and commissioned in Q1 2015. This unit gave some significant advantages including a reduction in re-grinding requirements, elimination of a circulating load and increase in the recovery of copper in the cleaner circuit and overall circuit.In this presentation, the benefits of columns and cavitation sparging for floating fine particles and rejecting fine entrained gangue will be explained. Also, the results from a lab unit and a pilot unit will be compared against the results of the full-scale unit. The paper will demonstrate the scalability of flotation columns, and which phenomena and scale-up criteria must be considered to be successful. Finally, some general observations will be made about the importance of columns in copper cleaning circuits.IntroductionSandfire Resources’ DeGrussa copper-gold concentrator is located approximately 900 km north-north-east of Perth in Western Australia. The project area landscape is scrubby mulga lands with few notable features. The climate is arid with high temperature and heavy summer downpours."

Jan 1, 2016