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By Dave Ragland

The SDSU tunnel and underground station are the first of these type facilities to be constructed by the Metropolitan Transit Development Board. Because there is no previous experience, and because tunneling activities are associated with some risk, he MTDB has undertaken a very proactive and wide reaching program to identify and control risks during construction. Finally, because the tunneling activity and underground station is on the San Diego State University, MTDB is working closely with their staff to identify construction impacts and mitigation’s, and thus ensure a quality project for both agencies.

Jan 1, 2001

By O. MacIntosh

The Round Mountain gold mine, located 90 km (55 miles) north of Tonopah, Nevada began large-scale production in 1977. During 2008 Round Mountain Gold Corporation (RMGC) relocated the primary crusher facility approximately 300 meters (1,000 feet) to make room for the next phase of open pit mining activities. This facility was installed in 1988 and used a log-crib retaining wall and dump pocket RMGC selected Hilfiker Retaining Walls and Collins Engineers, Inc. to provide design and materials for a new 17 meter (56 feet) high Mechanically Stabilized Embankment (MSE) wall to support the haul trucks at the new location. The construction contractor was EarthTech West Ltd. of Norwood, Colorado. An MSE wall with a cast-in-place concrete face was chosen as a durable, yet less expensive alternative to the reinforced concrete dump pocket that was originally designed for the project. The arrangement of the MSE wall is of an unusual configuration to meet a variety of operational and maintenance requirements. This paper outlines the selection process, design, and construction of the MSE wall.

Jan 1, 2009

By F. F. von Glehn

There is no doubt that simulated ventilation networks must be adequately verified before they can be extrapolated and used for predictive purposes. There are two general approaches as to how the verification can be established and these are summarised as follows; The first approach is to measure all individual branches with trailing hoses or barometers to get individual pressure drop and flow per branch and then calculate individual resistance factors for input into the software. The simulator is run, checking that the output makes general sense (check some sensitivities if possible). The network is now considered as verified. The pressure drop to be measured is relatively small and thus it is inherent that the measured set of individual K factors will be imprecise no matter how much care is taken in the measurements and the resultant simulations will inherit the same problem. In the second approach, the network is assembled using estimated (Atkinson) K factors (based on physical features of airway, past experience and catalogued typical K factors). Only the main primary flow rates are measured and hence the relative distribution of the primary ventilation in the main airways is determined (probably about 10 off primary air flow measurements). Main critical pressure differentials at main and booster fans and across critical doors are measured (probably about 6 off primary pressure differential measurements need to be made). The simulator is run and the computer model is used to iterate and select an updated suite of K factors so that the flow balances and pressure differentials are correctly simulated (typically only 2 or 3 iterations are all that is needed). The network is now considered as verified. The pressure differences to be measured will be substantial in absolute terms and can be measured with high precision. Also, because only primary flows are measured, these will generally be measured at higher air speed points and hence improved relative accuracy. This leads to more accurate simulation results. This paper examines the advantages and disadvantages of the two approaches. 1 Background

Jan 1, 2009

By L. B. Hales

Image analysis for feed belts and flotation has been used for over 20 years. It has been shown to aid in the modelling and optimization of Sag Mill circuits, and any improvements in the image analysis result in improvements in the model for control. Using a laser to measure the height-profile of rocks on the conveyor has been shown to increase the accuracy of the size classification. We have developed a system using two cameras in a stereoscopic configuration to provide height-profile measurement without the added expense and safety concerns of using a laser. Additionally, we have developed a novel technique for calibration of the system, using artificial intelligence techniques to optimize the model fit by adjusting the image analysis tuning parameters to values resulting in the best classification.

Feb 27, 2013

By David L. Hill

Newmont Gold Company's Mill No. 4 is located along the Carlin trend, about 25 miles North of Carlin, Nevada. The plant consists of a primary grinding circuit using a 7.2 m (22 ft) diameter by 2.6 m (8 ft) long semi-autogenous mill along with a 2.3 m (7 ft) diameter cone crusher. Secondary grinding is performed in a 4.8 m (14.5 ft) diameter by 9.2 m (28 ft) long overflow ball mill in closed circuit with a set of 66 cm (26 in) diameter cyclones. The ground product is fed to a typical carbon-in-leach gold leach circuit. The grinding/crushing circuit operation and control scheme are the topics of this paper.

Jan 1, 1993

By R. M. Imhof, M. J. G. Battersby, G. Ciernioch

Pneumatic flotation is rapidly becoming accepted in the main stream of flotation techniques. Imhoflot is a pneumatic flotation process that in recent years has undergone progressive development. It combines short flotation times with excellent selectivity by employing intense pre-aeration and dispersion. K+S GmbH (K+S), Germany, has installed a complete Imhoflot flotation plant at its Sigmundshall plant. The plant treats hard salt consisting of sylvine, halite, anhydrite and kieserite. The reason for selection was that Imhoflot achieves the required grades of plus 60 weight percent K2O whilst offering lower operating costs than conventional flotation installations.

Jan 1, 2002

By L. A. Weakly, D. A. Weiss, R. B. Crookston

A presentation of experience gained from using mechanical and conventional equipment for excavating shafts, raises, tunnels and other openings in various Colorado oil shale mining properties.

Jan 1, 1983

By Lisa Morrison

The 11th Annual Mineral Economics and Management Society (MEMS) conference was held April10-12, 2002, in Montreal, Quebec. It consisted of a series of technical sessions. Each paper addressed the economic issues that are related to the changes that many people believe are now required in the mining industry. Some of the papers were directed at how the mining industry will handle the changes that will be required in its philosophy and operations management. Of equal importance was whether the industry possesses the toolkit necessary to effect these changes and emerge stronger from its challenges.

Jan 1, 2002

By Magno Rodrigues Ribeiro, Alexandre Cabral Stelzer, Cacio José da Silva, Leonardo Nogueira Ferri, Marcelo Ciminelli Mendes, Christophe Bouché, Marco Aurélio Soares Martins, Evenilson Soprani Lopes, José Xavier da Silva Filho, Sérgio Luiz Dalvi

Since 2001, CVRD is carrying out a modernization project in it’s pelletizing plant’s automation systems, that comprehends instrumentation, control and information systems. In addition, the project includes implementation of advanced control systems, using artificial intelligence techniques, including fuzzy logic, expert systems and dynamic physical models, to increase production, reduce fuel and energy consumption and improve quality. This paper reports CVRD’s experiences in carrying out an optimization project.

Jan 1, 2005

By P. Ashayer, J. Curran

Introduction Rockfalls occur when rocks or boulders detach from mountains or hills and tumble down. They can pose significant hazards to infrastructure such as highways, buildings, and mine open pits, and they sometimes result in personal injury or death. Prediction of rockfalls is a difficult task. Slopes that are at risk of rockfall have highly variable geometries. The location, mass, and shape of the rocks that might dislodge and fall are uncertain. Moreover, the materials that make up a slope can vary considerably from one section to another. Furthermore, the relevant material properties are usually not well known. Performing probabilistic simulations of rockfalls, combined with proper statistical analyses, has proven to be an effective and acceptable method for dealing with these difficulties [1, 2, 3]. The movements of a falling rock can be classified as freefall, bouncing, sliding, toppling, or rolling. The falling trajectory is controlled mainly by the geometry of the slope, the block shape, and the energy dissipated at each contact of the block with the slope. A rockfall model is evaluated based on its ability to efficiently predict the velocity, frequency, height of bounce, and run-out distance of falling rocks. With this information, the engineer can design remedial measures such as restraining nets and ditches. Most of the existing rockfall simulators are based on particle models that consider the falling rock as an infinitesimal particle with a mass, called the lumped mass or stereomechanical models [1, 2, 3, 4]. Other models involve hybrid methods relying on simplified assumptions. The most common hybrid methods are based on contact searching for the movement of a dimensionless object and incorporate some aspects of rigid body impact for bouncing [5, 6, 7]. There are also some rigid body models in the literature that employ simplified versions of rigid body models [8, 9]. This study applies a more sophisticated rigid body theory based on rigid body impact mechanics (RBIM), which was developed by Stronge [10, 11, 12]. The new theory captures all modes of rigid body movement. Due to the importance of the rock geometry, single impacts of ellipsoidal and prismatic rocks with rectangular cross sections are investigated. The effect of rock slenderness on rebound velocities and energies is also investigated for ellipsoidal rocks. The correspondence between the model parameters and the data from the rockfall literature data will be discussed.

Jan 1, 2007

By D. G. Klaren

Self-cleaning fluidized bed heat exchangers are conquering the world for reason that they are able to solve any severe fouling problem in indirect heat transfer due to the circulation of cleaning particles through the tubes of vertical shell and tube exchangers. In most cases, these particles consist of chopped metal wire. Moreover, self-cleaning fluidized bed heat exchangers perform with excellent heat transfer at very low liquid velocities, which makes completely new designs of shell and tube configurations possible. Further, self-cleaning fluidized bed heat exchangers show a strong shear thinning effect in non-Newtonian liquids. All the above characteristics make the self-cleaning fluidized bed heat exchanger an ideal tool for the indirect heating of laterite nickel slurry in High-Pressure-Acid-Leach (HPAL) plants. Preliminary tests and evaluations of these heat exchangers have shown that the performance and price of these heat exchangers used for the production of nickel and cobalt from a laterite slurry, cannot be matched by existing conventional heat exchange systems. This article explains the principle, design, lay-out and enormous advantages of the self-cleaning fluidized bed heat exchange technology in a plant suitable for an annual production of approx. 45,000 ton nickel and 4,500 ton cobalt from laterite slurry through high pressure'acid leaching.

Jan 1, 2002

By Cathleen J. Webb, Arden D. Davis

The Homestake Gold Mine at Lead, South Dakota, has been proposed as the host site for the Deep Underground Science and Engineering Laboratory. The laboratory will house neutrino experiments in mine workings at the 7400-foot depth, as well as research in geomicrobiology, rock mechanics, and ground-water flow. Initial plans for the laboratory were developed in 2000 after Homestake Mining Company announced the closing of the underground gold mine. Homestake’s owner, Barrick Gold Corporation, had agreed to donate the mine for a laboratory if it could be protected from environmental liability. That initial agreement was delayed, and Barrick turned off the mine’s pumps in 2003, allowing lower levels of workings to begin to flood with water. In early 2004, the Governor of South Dakota signed an agreement with Barrick that would indemnify the company and eventually transfer ownership of the mine to a state laboratory authority. South Dakota’s governor also announced plans to ask the state legislature for funds to help in the initial construction of the laboratory. A consortium of scientists from several states is currently preparing a detailed laboratory proposal for the National Science Foundation.

Jan 1, 2005

By F. L. Pirkle, D. L. Pirkle, E. C. Pirkle, W. A. Pirkle

Heavy minerals have been mined from the sands of the United States’ Atlantic Coastal Plain since the early part of the twentieth century. Production of ilmenite from beach sands near Mineral City (Ponte Vedra), Florida, began in 1916. The first reported large-scale recovery of zircon in Florida was reported from this deposit in 1922 and of rutile in 1925. These operations ceased in 1929. Today the Ponte Vedra Country Club and Golf Course is situated in the center of the former mining site. In 1942 heavy-mineral operations were established on 202 hectares of land situated in Duval County, Florida. The location is about 16 kilometers east of the center of Jacksonville, Florida, in an area known as Arlington. This operation demonstrated that low-grade sand containing only 2 to 3 percent titanium minerals could be concentrated economically with the Humphreys spiral and that the oxides could be separated from the heavy silicates by electrostatic methods. Much of this area is now covered by a large mall and is a major retail- commercial center. Between 1958 and 1964 the Skinner tract, a deposit about 4 kilometers south of the above deposit, was mined. Today the area of this deposit is known as Deerwood, a gated country club community on the southside of Jacksonville. Further inland, E.I. du Pont de Nemours and Co. has been mining heavy minerals from a physiographic feature known as Trail Ridge since 1948, and a deposit near Green Cove Springs, Florida has been in production since 1972. Since the start of heavy-mineral mining in the southeastern United States, nine heavy-mineral ore bodies either have been or are being exploited in Florida and Georgia. Other deposits either have been lost to mining or are yet to be mined. These deposits have different origins. Some formed along shorelines at the heights of marine transgressions while others formed on regressional beach ridge plains during periods of temporary stillstands or slight transgressions. These different origins are reflected in the chemical and physical characteristics of the deposits. Ilmenite in older, more western deposits has a higher TiO2 content than ilmenite in younger, more eastern deposits. TiO2 content does not very with north-south direction. Garnet and epidote are absent or rare in the older Trail Ridge deposits, but progressively become common in the younger Duval Upland, Crestal Pamlico, and Holocene deposits. Grain size is coarsest for Trail Ridge sediments and finest for sediments in Duval Upland and Crestal Pamlico deposits. The average grain size for Holocene deposits is intermediate between Trail Ridge and Duval Upland deposits. The two models for the origin of the heavy-mineral deposits – deposits formed at the height of major marine transgression; and deposits formed during periods of temporary stillstands or slight transgressions that occur during a general marine regression; - are consistent with known sedimentological data and depositional trends.

Jan 1, 2005

The stability of surfactant-free foam films was studied using the thin film pressure balance (TFPB) technique. In pure water, it was not possible to produce foam films due to weak film elasticity and strong hydrophobic force. In the presence of NaCl, however, the hydrophobic force was sufficiently dampened to allow metastable films to form. At 10-5 M NaCl, the equilibrium film thickness reached a maximum of approximately 130 nm at pH 6.0-7.3. The thinner films obtained on either side of this pH range was due to the increased ionic strengths associated with the HCl and NaOH additions for pH control.

Jan 1, 2009

To build an effective entry roof beam, a roof bolting or supporting system must be of the ability of providing a clamping force to the bolted roof strata. Currently, two roof bolting systems are widely used to serve the purpose of providing such a clamping force. They are resin and mechanical anchorage bolting systems. Both numerical modeling and double shear testing results indicate that a greater pre-installed load or pretension of a roof bolting system is very critical for effective beam building. Although it?s generally accepted that a mechanical anchorage bolting system can provide a greater pretension than a resin anchorage bolting system does (Su and Poland, 2007 and Peng, 2008), no published field data are available to support such a conclusion. This paper analyzes the results of our field tests on both roof bolting systems, explains why one roof bolting system is better than the other under a typical roof condition, and finally discusses the effective means for coal mine operators to determine the best roof bolting system for their roof conditions.

Jan 1, 2011

The management of risks associated with slope instability is an essential process in the safe and economic operation of open cut mines. The ?slope stability radar? (SSR) has been developed to better manage those risks. The SSR remotely scans rock slopes to continuously measure any surface movement and can be used to detect and alert users of wall movements with sub-millimeter precision. The high level of movement precision and broad area coverage of the rock face can allow for a better understanding of the geomechanics of slope deformation, including magnitude of potential failures and additional warning time of impending instability. Additionally, radar waves adequately penetrate through rain, dust and smoke to give reliable measurements, 24 hours a day. SSR systems have been deployed in many metalliferous and coal mines throughout the world. Over 80 systems are currently being used with current operations in 17 countries. Greater than 200 rock slope collapses and waste dump failures (from several to millions of tones) have been monitored, with ?warning? precursor movements recorded by the SSR. This technology enables a radical change in the management of risks in open cut mining. This paper will present recent case studies of the SSR operation in coal and metalliferous mines. Slope Stability Hazards and Rock Slope Monitoring in Open Pit Mines Surface mining often creates excavation boundaries which are steeper than those would be created under natural processes in the same rock type. They are also undertake quite rapid stress changes during mining and are influenced by significant external forces such as blast vibrations and changes in groundwater. These conditions are likely to allow some degree of instability to develop in the pit slopes. The hazards associated with this instability of pit slopes can be extremely variable in character; ranging from small cobble sized rocks dislodging and falling from mine benches to complete collapse of entire pit walls. It is usually the position of mine geotechnical or geological staff to assess these hazards for mine operations. The assessment of hazards due to unstable slopes can be done by visual observation of precursor signs such as fracturing or rilling of loose material. A more reliable indicator of instability involves the quantitative measurement of outward movement and acceleration of material as an instability mechanism develops. There is strong evidence that small precursor movements of a rock wall occur for an extended period prior to rock slope collapse (Hoek and Bray, 1981). Development of a monitoring system, adopting acceptable slope deformation criteria coupled with warning systems and design of stabilization or risk reduction measures if appropriate has become a standard method of dealing with slope instability. Framework for Slope Hazard Management using the SSR A framework for the management of slope hazards is shown in Figure 1 (discussed in detail in Harries, 2007). Although this framework is specifically for use with the Slope Stability Radar, a similar framework could be developed for other monitoring technologies for monitoring slope deformation. An important point to consider is the sequential nature of the hazard management framework from selecting the context ? identifying hazards ? analysing hazards ? evaluating hazards ? treating hazards. [ ] Once the context of the system has been developed (for example ? to monitor for rapid bench scale collapse), the identification of hazards is the next stage in hazard management. Identification of slope hazards can be relatively straightforward due to the visual nature of the information that the SSR system produces. The areas of excessive wall deformation are highlighted in color maps of the mine slope with a co-aligned photographic image to review the actual site of interest. The responsible personnel must then analyses this data, usually reviewing the deformation style and rate, as well as the size of area that appears to be failing. This information can then be evaluated against organisation protocols (for example it may be only a small sub-bench failure that will be ?caught? by existing benches and hence can be categorized as a lower risk). Once these hazards are evaluated they can then be treated if required. Two major options are available to reduce the risk during this treatment option. We can reduce the likelihood of failure ? for example by buttressing the failure or de-pressurising of water pressures in a slope. However, the most likely plan of action is to reduce the consequence of the failure. One of the most successful opportunities to reduce the consequence of a slope failure is to ensure that no personnel or mining equipment is present at the location of a slope failure when collapse finally occurs. This has been the major benefit of the SSR system to the different mining operations around the world. SLOPE STABILITY RADAR TECHNOLOGY OUTLINE Slope Stability Radar system specifications and capabilities: ? Measurement precision +/- 0.1mm (std.) ? Perforated dish and other features enable it to operate in high wind conditions ? Measurement range is 1700 metres ? Scans 270 degrees horizontally and 120 degrees vertically ? 1 ? 30 minute repeat rate for area scans (varies according to area being scanned ? RF exposure (<0.05mW/cm2) is a factor of 200 below the acceptable limit for the general population (1 mW/cm2) ? Tolerant to vibration and mining equipment ? The system weighs approximately 1500 Kg ? Remote area power supply enabling unmanned, continuous 24/7 monitoring ? Real time monitoring

Jan 1, 2009

In its April 1991 issue, MINING ENGINEERING published a salary survey form asking for information relating to engineering and management jobs in the minerals industry. 1038 of these forms were filled out and returned, most of them being received in the magazine&apos;s offices at SME headquarters before the end of June 1991. An SME volunteer took on the task of tabulating and analyzing data from the forms, but the press of other business interfered with this work, and publication has been delayed until this issue of MINING ENGINEERING. Appreciation is extended to SME members who took the time to fill out and return the salary survey forms, and our apologies go to MINING ENGINEERING&apos;S readers for the delay in publication. Of the total number of forms received, more than 97% were from SME members. The geographic distribution of the respondents closely mirrored that of SME membership as a whole, about 50% being from the Society&apos;s Western Region, 19% from the Central Region, and 23% from the Eastern Region. About 8% were from outside the US. Average salaries for each of the four geographic areas ranged between $55,000 and $60,000, with the highest average in Eastern Region (Fig. 1). Respondents were asked to answer a number of questions formulated to determine if there are significant differences in salaries based on the type of organization for which they work. As indicated by Table 1, salary averages at mining companies do not vary markedly with the size of the company: • Large companies, defined as those having more than $1 billion in annual sales, accounted for just over 16% of the returns. Their average salary was $61,840 per year.

Jan 1, 1992

By S. A. Abdel Sabour

Conventional methods for selecting a production plan for an open pit mine is based on the assumption that ore grades throughout mine life as well as market variables are known with certainty. Another important issue that is also being ignored in the conventional procedure is the value of management flexibility to revise operating policy with time according to the arrival of new information. Based on this oversimplification of reality, an optimum mine plan that is thought to be maximizing net present value (NPV) of the project is selected. Given the multiple sources of risk affecting the estimated NPV, there is a high probability that the actual value will be different from that estimated. This could mislead decision making process regarding selecting an optimum mine plan. This paper proposes a multi-criteria ranking system for selection between alternative mine designs under both geological and market uncertainties. The system is based on integrating multiple market and geological uncertainties as well as the operating flexibility to revise the ultimate pit limits using a Monte Carlo-based real options valuation (ROV) model. To compare the methods, the article applies the proposed system, along with the conventional NPV-based method, to rank possible mine designs for a copper and a gold mine. It has been found that, considering multiple risk analysis measures while integrating uncertainty and operating flexibility results in selecting a mine design that is different from that selected by the conventional method.

Jan 1, 2009

By Christian Maguire

The presence of hydrogen sulphide in sewerage systems leads to severe concrete corrosion. Acid causes breakdown of the concrete matrix, and attacks reinforcement. Older sewer systems under acid attack are often found to be acutely corroded, sometimes after short operational periods. Consequently secondary liners are now almost always used. Polymer concrete is extremely acid resistant and if used in segmental linings can forgo the need for a secondary lining. Combined with fibers and/or GFRP rebar Polymer Concrete can produce a very strong acid resistant lining, saving considerable time in the installation of additional liners. This paper explains the problems and advantages of using Polymer concrete in segmentaly lined wastewater tunnels, addressing areas of design, cost, and programming.

Jan 1, 2008

By M. Schafer

The 20 foot diameter cast-in-place tunnel lining for Phase 3 of the Mill Creek Tunnel (MCT-3) has been completed. This paper will summarize aspects of liner design and address the construction approach in placing the liner in areas of tunnel that experienced crown overbreak. Tunnel lining production rates, installation procedures and form buoyancies experienced during concrete placement will also be presented.

Jan 1, 2008