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By A Croll

A panel cave using LHDs for ore extraction came into production at Premier in 1990 at a depth of 630 metres below surface on the western side of the mine in the BA5 mining block. A post-undercut mining sequence was used with all development on both the undercut and production levels completed prior to the undercut being advanced over the pre-developed drawbells. Support and rock mass damage on the production level was extensive as the undercut moved overhead. Undercutting and coarse fragmentation created problems. The mining sequence was changed to an advance undercut with the minimum of development and support undertaken on the production level prior to the undercut moving overhead. Only once the abutment stresses had stabilised were drawbells developed and final support installed. The height of the undercut drill design was decreased from 18 to 13 metres. The changes resulted in markedly less rock mass and support damage on the production level. Lessons learned in the BA5 mining block on the 630 level were incorporated into planning and scheduling the BB1E mining block which came into production on the 732 metre level on the eastern side of the mine in 1996. An advance undercut mining sequence was planned, undercut height was minimised and undercutting parameters were optimised in terms of the BA5 experience. Numerous problems still occurred. As the undercut area increased in size severe spalling from the cave back resulted in vertical propagation of the cave to a height of 30 metres instead of the planned 13 metres. The resultant coarse fragmentation created secondary blasting problems and an excess of undercut ore that had to be loaded and trammed, slowed the rate of undercut advance. The planned mining sequence was compromised and considerable support and rock mass damage resulted on the production level below. Once these problems had been overcome the undercut advanced at the planned rate and continuous caving initiated at the predicted hydraulic radius. At a later stage the unexpected ingress of water hampered undercut drilling and slowed the rate of undercut advance in a section of the cave. Leads and lags between adjacent tunnels and the overall face shape could not be developed as planned. The rate of natural horizontal cave propagation exceeded the rate of undercut advance and three undercut drilling tunnels were extensively damaged. More tunnel development on the production level prior to undercutting than was planned resulted. The slow advance of the undercut and high abutment stresses caused extensive damage to installed support and the rock mass on the production level, 15 metres below. Experience in the BB1E mining block on the 732 metre level has taught that an advance undercut mining sequence reduces damage on the production level markedly. Extremely tight control on the rate of undercut advance, leads and lags between adjacent tunnels and overall undercut face shape as well as extraction ratio, tunnel development and support sequence on the production level below is required. Premier Mine plans to implement a block cave at a depth in excess of 1000 metres within the next decade. All the experience gained on current mining levels together with data collection and numerical modeling is being used to plan the proposed mining operation. The geotechnical challenge of mining at this depth in weak rock has been identified as the greatest risk to the project. Challenges centre around adopting the correct mining sequence, limiting the extent of rock mass damage associated with undercutting and effective support. The hydraulic radius needed to initiate caving, fragmentation, drawpoint spacing, secondary blasting and the possibility of seismicity are geotechnical concerns that are being addressed. Results to-date suggest that a pre-undercut mining sequence with all development and support on the production level carried out only after the undercut abutment stresses have passed overhead will have to be implemented.

Jan 1, 2000

By I. Benning

Since the dismal performance of the Rand Mines management was called to account by its shareholders in 1994, the waves of change have continued to ripple across the South African mining industry .The number of listings on the gold board of the Johannesburg Stock Exchange, that once numbered 40 or 50-odd, have now dwindled to no more than a handful as unprecedented restructuring has taken place. The redefining of the industry has not been limited to the gold sector, but across the base metal, coal, diamond, platinum and industrial mineral sectors as well. At the same time the Mining Houses began to reconsider their funding strategies. Originally established in the early part of the century to ensure the long-term sustainability of their group mining operations by providing substantial financial muscle and technical support, the Mining Houses were faced with a rapidly changing political environment, which proved to be a critical catalyst in giving momentum to the change. Furthermore, the significant development costs and increasing risk profile for new projects, coupled with pressure from shareholders demanding respectable returns, opened the door to opportunities for banks to begin providing external debt by the way of project finance. However, the provision of long-term debt to the South African mining industry had generally not been common since mining companies had financed new projects with equity, or with the cash flows from existing operations. Those banks that had the appetite for exposure to the perceived high risks of the mining sector rapidly built up specialist resource banking divisions capable of addressing the increasing demands of the industry. The application of project finance, the principles of which were developed in the 1970s specifically for infrastructure projects and privatization, is now commonly applied in the financing of greenfield and brownfield mining projects. This paper outlines the approach that lending banks would typically adopt when arranging or providing mining project finance, their usual areas of concern and the way in which the finance is structured to mitigate the many inherent risks.

Jan 1, 2000

By J. S. Y. Wang, R. C. Trautz

A 9-meter-long drift was constructed in the unsaturated-fractured tuff at Yucca Mountain to evaluate the potential for water seeping into an underground opening. Forty seepage tests were performed by releasing a finite volume of water at a constant rate into short test intervals located in boreholes positioned above the drift. The seepage threshold flux, defined as the liquid-release flux at and below which water will not drip into the opening, was determined for 10 test intervals. The seepage data, observations, and model results indicate that a seepage threshold exists because a capillary barrier diverts water around the opening.

Jan 1, 2000

By Jack Hayes

The design and construction of deep foundations involve many uncertainties. For the designer there are uncertainties regarding soil and ground water variability, regarding sampling and lab testing, regarding analytical techniques and regarding construction technique. The latter being the uncertainty over which the engineer has least control and which may have the greatest impact on capacity. Foundations with a high design factor of uncertainty can be very costly. Foundations designed with a high factor of uncertainty may have a low factor of safety, which can be even more costly.

Jan 1, 2000

By Jean-François Boucher, Ernest K. Yanful, Mei Lin Shelp, Lionel J. J. Catalan

Shallow water covers for preventing acid production in tailings are based on the principle of minimizing oxygen availability. Resuspension of material from the tailings bed may result in increased oxidation and metal releases since dissolved oxygen is at near saturation levels in the water cover. Resuspension can be caused by waves and currents strong enough to mobilize the surface of the tailings bed. Tailings resuspension was measured with sediment traps in the Upper Cell of the Heath Steele site near Mirarnichi, New Brunswick Canada. Although significant amounts of resuspended tailings were collected in all traps, analysis of resuspended solids and bed tailings suggests that for the observed wind conditions resuspension did not occur at locations where the water cover depth was greater or equal to 1.0 m. Currents were likely responsible for the transport of resuspended tailings from shallower areas to locations where the water cover was deeper than 1.0 m.

Jan 1, 2000

By Y. Mori, K. Kawanaka

The permeability changes during the sintering of the feed for the Imperial Smelting Process (ISP) were investigated using an experimental sintering pot, as well as with a mathematical model. The results obtained were as follows. The blowing resistance in the sintering bed changes as the sintering reaction proceeds. It increases at the beginning of the reaction when the temperature of the bed is still low. Then it decreases as the reaction continues, accompanied by an increase of the bed temperature. The increase of the blowing resistance in the bed during the sintering process mainly occurred in the drying zone, and was comparatively small in the reaction and cooling zones. Based on Erugen's equation, the change of the permeability during sintering is explained by the decrease of the apparent fractional void volume in the drying zone of the bed.

Jan 1, 2000

By Vaughan R. Voller

"Over the last ten years an increasing number of heat and mass transfer models of solidification processes have been presented in the literature. A key component in these models is the coupling between thermal and solute fields. This is achieved by developing relationships based on the behavior at the microscopic scale in the casting (typically a secondary dendrite arm space). An important class of models in this respect are models that describe the local scale redistribution of solute alloy components-collectively referred to as microsegregation models. This paper explores this class of models.IntroductionModeling takes a key role in processing materials for properties. This is particularly time in solidification processes where current computer techniques allow for a detailed treatment of the critical macroscopic phenomena. Typically these macro scale models consist ·of three main coupled components.1. A model of flow in the melt and solid + liquid mushy region.2. A model of heat transfer.3. A model of solute transport.The focus of this paper is the solute transport component, in particular the manner in which process scale transport is coupled to transport ·at the local scale of the solid-liquid interface. This step requires a modeling of the redistribution of solutes at the scale of the secondary arm spaces in the dendritic mushy region-a process referred to as microsegregation. Basic microsegregation models use the limit assumptions of no mass diffusion in the solid (Gulliver-Scheil [l]) or complete diffusion in the solid (equilibrium lever rule) in a fixed and space. Recently, however, more sophisticated microsegregation models that account for finite mass diffusion and coarsening of the arm space have been developed [2-19]. In this paper governing equations for a general microsegregation model for a multi-component alloy in a coarsening and spacing _are introduced. From these general equations various models for a binary system are developed and tested"

Jan 1, 2000

By Geoffrey Birch

A skilled and efficient workforce is a pre-requisite for the success of modern construction companies. The drive for improved performance, innovation and best value must be matched by the enhanced skills of the construction personnel. Training has been accepted as one of the essential cost effective elements to achieve these goals. The foundation industry demands particular specialist skills and requires focused training for its dedicated operatives. The introduction and development of specific training qualifications for the foundation sector is providing significant benefits.

Jan 1, 2000

By K Karmawan, T Casten

The PT Freeport Indonesiaæs Deep Ore Zone (DOZ) copper deposit is located in the province of Irian-Jaya, Indonesia. Currently, a block cave mine is being developed around this deposit. Production is scheduled to start the fourth-quarter of year 2000 and to ramp up to 25 000 tpd by year 2003. The air quantity requirement for this mine is equal to 780 m3/s. To supply this quantity, the mine will require five centrifugal fans (one 450 and four 750 kW fans). This study summarises the technical aspects related to the installation and commissioning of two of these fans. The fans were installed on the surface in parallel arrangement with two others. Each has a design capacity of 240 m3/s of air at 2.2 kPa of static pressure. The study presents the installation details from the underground shaft excavation and portal development through fan testing and commissioning. It also presents the results of a monitoring system that was installed to determine the fan duties.

Jan 1, 2000

This surveillance report summarizes data on work-related fatal and nonfatal injuries, illnesses, and hazardous exposures in the mining industry for the 10-year period 1986-1995. The term ?surveillance,? as used in public health, may be new to many readers of this report. With regard to occupational safety and health, the goal of surveillance is to describe the occurrence of work-related injuries, illnesses, and known hazardous exposures; to identify new hazards that may occur due to the introduction of new technology or other factors; and to assess the effects of preventive measures designed to improve worker safety and health. Surveillance provides an overall picture, which can be used to focus resources on areas most in need of prevention programs or further research. Surveillance generally requires the use of multiple sources of data, all of which have their own strengths and limitations. Surveillance in the U.S. mining industry is complicated by the fact that U.S. national data systems that provide information on mining are based on two different definitions of the mining industry. One is established by the Mine Safety and Health Administration (MSHA), the other by the Standard Industrial Classification (SIC) System [Office of Management and Budget 1987] and the 1980 U.S. Bureau of the Census (BOC) Classification System [U.S. Bureau of the Census 1982].

Jan 1, 2000

By Michael L. Nave

Mining belt conveyor elements are becoming larger and more expensive. Conveyor reliability requirements are rising. Conveyor condition monitoring can aid maintenance, reliability, and risk management in conveyor system operation. This paper examines the application of condition monitoring in coal mining belt conveyor systems. Types and form factors of condition sensors are described. Example costs are included. Suggestions for OEM developments are examined. Application problems are discussed. Two simple cost case studies are presented.

Jan 1, 2000

By P Cundall

Three-dimensional DEM (Distinct Element Method) simulations were conducted in order to examine the performance of screw conveyors, which are installed to transport bulk materials as parts of many industrial machines, including mining and construction machinery. To apply the DEM to the analysis of screw conveyors, we added a spiral object and cylinder objects, which correspond to the helical screw, the casing pipe, and the driving shaft of a screw conveyor. These objects are represented analytically to enhance the precision and efficiency when calculating the interaction between objects and particles. Simulations were conducted for some real applications: inclined and other types of screws, as well as the basic types (horizontal and vertical). Results were compared with previous work and empirical equations. It is concluded that this method is sufficiently well-developed and useful to analyse various kinds of screw conveyors.

Jan 1, 2000

By Hiroaki Nakano, Kenji Hara, Shunsuke Kawano, Takeshi Ohgai, Michiaki Ikeda, Hisaaki Fukushima, Shinji Yamashita, Tetsuya Akiyama, Hisayuki Kaku

"Ni-Fe alloys have an inverse magnetostrictive effect (Villari effect) in which its permeability varies according to the ·applied strain. This alloy film has a potential for application as force sensors such as torque sensors, tension sensors and so on. Electrodeposition is promising as a technique for preparing Ni-Fe alloy film because of its convenience and economy. In this paper, the effects of electrolysis conditions on the magnetic properties of electrodeposited Ni-Fe alloy films were investigated. Hysteresis loops of Ni-Fe alloy films on copper substrates from sulfate bath were measured by a vibrating sample magnetometer (VSM). The films of low coercivity, which were preferred when used as a force sensor were obtained by introducing certain additives to the sulfate type bath.INTRODUCTIONNi-Fe alloys show an inverse magnetostrictive effect (Villari effect) that their permeability varies depending on the applied strain. The films of this alloy have a potential for application as force sensors such as torque sensors, tension sensors and so on. The authors et al. tried to prepare Ni-Fe alloy films using the sputtering technique, and produced a prototype of Ni-Fe alloy torque sensor [I]. The sensitivity was higher in the torque sensor thus produced than the strain gauge type one, and this torque sensor enables non-contacted detection. It showed excellent durability and reliability. However, the formation of Ni-Fe alloys by sputtering requires higher costs and brought an another problem that the shape of the substrate on which the film was formed was considerably limited. This causes a hindrance to the wide-range application of the force sensors. Electrodeposition is promising as the technique for preparing Ni-Fe alloy films because of its convenience and economy. In this paper, the effects of the conditions of electrodeposition on the magnetic properties of Ni-Fe alloy films were studied."

Jan 1, 2000

By Robert Seal, James J. Rytuba, Michael P. Hunerlach, Roger Ashley, Dean Enderlin

Cessation of open pit mining in 1996 at the McLaughlin hot-spring type gold deposit has resulted in the development of two pit lakes that will be managed as permanent lakes with a total storage capacity of 10,000 acre-feet. The south pit lake developed from alkaline ground water infiltration and had an initial pH of 7.2. It contained high concentrations of boron and chloride, indicating that it consisted of a mix of meteoric and evolved connate waters. Numerous carbon dioxide gas vents were present initially in the shallow south pit lake, but as the pit lake increased in depth, gas venting ceased and carbon dioxide is retained in the lower layer of the chemically stratified lake. Continued increase of dissolved carbon dioxide in the lower layer increases the potential for a limnic eruption. A chemocliie occurs at a depth of 47 m. The upper layer of the lake has lower pH, temperature, and conductivity than the lower layer. Effluent from ore and waste rock piles directed into the south pit lake has contributed to high levels of antimony, arsenic, cobalt, copper, mercury, nickel, and zinc. Iron oxyhydroxide is abundant in mine effluent that enters the pit lake and adsorption onto this phase has lowered the arsenic and antimony concentrations. The north pit lake formed primarily from winter surface runoff. The acidic water, pH 4.56, initially had high concentrations of cobalt, mercury, and nickel derived from weathering products of pyritized serpentinite and shales. Buffering by wall rocks has established a slightly alkaline pH of 7.62. The concentrations of trace metals in the north pit lake have substantially decreased due to continued dilution of the lake by surface runoff and remediation of parts of the pit walls that have been covered by backfill.

Jan 1, 2000

The functional design of a pavement relates to the selection of appropriate wearing course materials which optimise the trafficability of a pavement. Trafficability is dictated to a large degree by the choice, application and maintenance of locally available wearing course materials. Poor functional performance results in decreased safety and operational efficiency and increasing road and vehicle maintenance requirements. An optimal functional design will include a certain amount and frequency of maintenance (watering, grading etc.) and thus maintenance itself can be planned, scheduled and optimized within the limits of required road performance and minimum vehicle operating and road maintenance costs. Since no wearing course material selection guidelines, tailored to the specific needs of surface mines, were available, there was the need to identify appropriate selection guidelines for the range of materials commonly encountered for road building on South African mines. The aim of this paper is to present an overview of the functional design method for mine haul roads and, through an analysis and quantification of existing wearing course material performance, to recommend appropriate wearing course material selection guidelines. The functional design technique has been applied at a number of mines and is illustrated by an application case study which demonstrates the potential reduction in total transportation operating costs associated with the optimal functional design.

Jan 1, 2000

By F. M. Doyle, C. V. Diniz, A. H. Martins

A proposed process for the direct production of battery¬grade Mn02 leaches manganese ore with HCl to remove heavy metals selectively. The acidic manganese chloride solution produced is contaminated with Cu, Ni, Co, Pb and Fe at levels that preclude immediate utilization. This paper reports on screening tests to measure the uptake of Cu, Ni, Co, Pb, Fe and Mn from acidic chloride solutions onto different chelating ion exchange resins. Dow M-4195, which contains the bis-picolylamine,functional group, showed promise for detoxifying manganese chloride process solutions. Column ion-exchange tests demonstrated the ability of this resin to produce pure manganese chloride solution from an acidic manganese chloride leach solution contaminated by Cu, Ni, Co, Pb and Fe.

Jan 1, 2000

By P Crorkan

Within the framework in which future exploitations for Codelco-Chile Divisi=n El Teniente are situated, regarding the deepening of its reserves and the geotechnical problems that affect their recovery, it becomes strategic to evolve with new variants, which make deep mining possible. Codelco ChileÆs Divisi=n El Teniente is progressing within its long-term planning the exploitation of a sector called Esmeralda, which includes its removal through the gravitational caving method (panel caving). It is planned to use pre-caving, which basically consists of developing and undermining the undercut level, without having developed the infrastructure of the production and transport levels. This is carried out in order to achieve a better redistribution of the stresses, thus obtaining higher quality in the infrastructure development of these levels as well as less risk. The extraction reserves for this area, estimated through the opportunity cost selection criteria, were determined at 348 million tons with an average grade of 1.014 per cent Cu. The project carried out geological and geotechnical studies in order to prevent the geomechanical risks of the sector to be exploited, which is a site conformed totally by primary ore. Lithologically, it occurs mainly in Andesite, located at the western limit by Brecha Braden Pipe. There are also varieties of porphyries and hydrothermal breaches of anhydrite. The Esmeralda Mine production program will increase from 4000 tpd (average) in 1998 to its 45 000 tpd rate of production estimated for the year 2005. The approved investment for the period 1995 to 1999 is $US 150 million, out of a total $US 213 million for the project. At feasibility study level and before the project, it showed a Net Present Value of $US 342 million, an Internal Rate of Return of 37 per cent and an IVAN indicator of 2.3 for a ten per cent discount rate and a copper price of 100 US cents/lb.

Jan 1, 2000

By Todd M. Ruff

An average of 13 mine workers are killed each year by being run over or pinned by mobile mining equipment. At surface mines, these accidents commonly involve large dump trucks that drive over a smaller vehicle or a person that is in the dump truck’s blind spot. One method of detecting a person or another vehicle in a blind spot is to use some type of sensor technology such as radar or radio-frequency identification (RFID). Researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health tested a number of commercially available and experimental sensors that monitor obstacles in a vehicle’s blind spots. None of the sensors had been previously applied to the specific problem of rigid-frame surface mining trucks. This report documents the procedures and results of tests conducted after RFID and radar systems were mounted on a 50-ton-capacity dump truck. It was determined that both RFID and radar technology show promise for detecting obstacles in the blind spots of mining equipment; however, more development work is needed to meet the unique requirements of mining equipment and the mine environment.

Jan 1, 2000

By L. I. Gyrskia, Y. V. Andreev, T. N. Greiver, G. V. Petrov

Traditionally, chromite ores are regarded exclusively as a monomineral raw material for extraction of chromium. The results of the investigations indicate a wide range of PGM in the Ray-Iz chromites, amounting to 1-3 ppm PGM. The study of products of primary gravity concentration from heavily and lightly disseminated ores (Tsentralnoe deposit, Ray-Iz block), showed that the platinum-group minerals are concentrated in the tails and slimes of the processed products, containing 10-30 ppm total PGM. Preliminary data make it possible to conclude that an in-depth study of the platinum mineralogy of the Ray-Iz block chromite ores is necessary to develop a process that will produce both chromium and the PGM.

Jan 1, 2000

By Arturo Ressi di Cervia

From the times when men in lacustrine environments drove wooden piles into the mud to elevate their dwellings, until the beginning of the twentieth century builders reacted to the conditions found in the location of their proposed structures by attempting to distribute their loads in ways that could be supported by the foundation's soils; or, if those were unsuitable, by moving the structure, whenever possible. While many major structures were built on stable ground (the pyramids were founded on rock), others were built on [ ]

Jan 1, 2000