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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 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

By E. M. Spokes

Starting in 1980, a committee of the National Research Council studied the question of why some underground coal mines are safer than others and what could be done to improve the ones with poorer performance. The results indicated that safety is improved by management commitment to safety, by cooperation between labor and management on safety matters, and by quality training of employees and managers. Younger miners have higher accident frequencies, but are less likely to be killed or permanently disabled by a lost-time accident. Methods for improving safety performance are proposed.

Jan 1, 1987

By T. Yegulalp, M. Castaldi

As global energy demands increase, there will be a critical need to employ fuels that have minimal environmental impacts. While hydrogen is considered the ultimate fuel for that purpose, hydrocarbon based fuels will be in use for a considerable time and will probably be the first major source of hydrogen for next generation power systems. The best fuel for this transition will be natural gas because of the high hydrogen to carbon ratio. Natural gas hydrates have the potential to meet the global energy needs for the foreseeable future. The amount of energy stored in natural gas hydrates is significantly more than that of all the other fossil fuels combined. However, most proposed techniques for recovering the natural gas from the hydrate require too much energy input, raise safety concerns or can only recover a fraction of the gas. This paper discusses the technical feasibility of a novel method of gas production in hydrate reservoirs. The method is an in-situ process that creates a point heat source in the hydrate formation. This method not only significantly reduces the energy input, but also has the potential to sequester as much or more CO2 than would be produced from combustion of the natural gas produced, thus making this in-situ methane production technique virtually carbon neutral. Simulations using FEMLAB™ show that the method offers an energy efficient and environmentally friendly way to produce natural gas from hydrate reservoirs. Preliminary results indicate that it is possible to have an energy efficiency of nearly 90% for land based reservoirs for hydrate loadings of 20%. The simulation results also suggest that alternatives to a point source can be employed which may improve the process efficiency.

Jan 1, 2007

By D. R. Dolinar

Geogrids can be used as surface control on both the roof and rib in underground mines to prevent the fall of small pieces of rock and material from between the primary supports. The use of screen material such as geogrid can significantly reduce the number of ground fall injuries caused by these small rock falls. Because of the potential for reducing injuries through the use of screen, the National Institute for Occupational Safety and Health (NIOSH) has conducted tests on screen materials including geogrid to determine their support characteristics and identify parameters that can affect their performance with respect to maintaining broken or failed rock. A specially designed test frame installed in the NIOSH Mine Roof Simulator (MRS) has been used to evaluate the load and stiffness characteristics of the screen material. Two types of geogrids with various designs have been tested-a polyester yarn and a polypropylene grid. The load-displacement characteristics of these grids were determined and the load capacity and stiffness were calculated through 20in of displacement. The load capacity and stiffness of the geogrid in general are shown to be related to the ultimate tensile strength of the screen material.

Feb 27, 2013

By L. R. Moore

Arsenic is among the list of major contaminants in mining aqueous waste streams. Though the elemental form is toxic, the aqueous oxyanions are more so. The most common forms of arsenic released during mining processes are arsenate and arsenite. The common treatment technologies to date can be summed up in these major categories: oxidation, coagulation, absorption, and media filtration. These methods can often involve many expensive processing steps that may also be limited by variables, such as total dissolved solids, other cations and anions, and the oxidation state of the arsenic. An innovative technology, falling in the absorption category, was developed that can successfully reduce such aqueous forms to a level below the EPA recommendations. This new technology offers a unique and viable solution which is transparent to the above mentioned limitations.

Jan 1, 2012

By Leeming. J. R.

In the UK, powered supports are normally salvaged from longwall faces on completion of production, for reuse on the next unit. Where a spare set of supports are held, the salvaged supports are often stored in underground roadways awaiting installation. One mine in the UK extracts a 5m section, and holds two sets of 2x950t powered supports, each weighing approx. 35t and having closed dimensions of 8m long, 2.5 high and 1.75m wide. As the first set would not be required for over 12 months, and because of space limitations below ground, it was decided that the supports would be left in situ, the district sealed, and reopened at a later date for support salvage. The paper described the decision making process, and the inertisation of the sealed district utilising nitrogen generated on the mine surface and piped to the point of use. The re-entry and re-ventilation of the district are also described. The paper then goes on to describe in more detail the discovery of a spontaneous combustion event that occurred in the waste behind the powered supports, and its treatment and control using extra nitrogen brought to the mine by tanker and introduced at strategic locations along the faceline via boreholes, leading to a successful salvage and re-sealing.

Jan 1, 2009

By A. Martin

Detailed porewater profiles of arsenic and other interstitial metabolites were used to assess the relationship between trophic status, sediment redox chemistry and arsenic mobility in a historic tailings repository. The results demonstrate that in eutrophied systems which exhibit greater sediment oxygen demand, the depth of the Fe(III) redoxcline, and hence depth of arsenic release, may lie in close proximity to the sediment-water interface. As a result, arsenic scavenging mechanisms are significantly reduced, resulting in a greater flux of arsenic to the water column. Such considerations have important implications for the management of pit lakes, tailings ponds and contaminated lakes which may consider: 1) the discharge of sewage to the water body during operations; and/or 2) post-closure fertilization as a remediation strategy.

Jan 1, 2002

By K. Burke, K. L. Myers, R. Espell

Barrick Goldstrike’s (Goldstrike) AA Heap Leach Pad is an HDPE lined facility used for gold recovery from low grade ores using conventional cyanide heap leach technology, operated from 1987 through 1999. Goldstrike prepared a unique reclamation plan for the AA Leach Pad Facility to provide for a cost-effective, environmentally sound facility closure and to fulfill the State of Nevada’s closure requirements. Traditional Nevada leach pad closure has involved rinsing to reduce cyanide concentration to an acceptable level, followed by reclamation. However, certain metals and compounds are not typically reduced by rinsing and some constituents may increase in concentration with rinsing. A closure scenario to effect limited infiltration through installation of a capillary cover for the leach pad was developed. The capillary cover was constructed by placing a fine-grained layer above the coarse-grained spent leach material to create a capillary break. In an arid climate such as Nevada, the fine-grained layer will rarely reach full saturation and the cover will be able to store water during precipitation and allow removal of water through evaporation and transpiration (ET) during the growing season. A 1.22 m (4 ft) cover thickness was selected as the optimum design cover thickness. The drainage network on the surface of the re-contoured AA Heap Leach Pad was specifically designed to enhance the revegetation, reclamation, and sediment yield control aspects of the AA Heap Leach Pad closure, while resulting in a natural looking surface, compatible with the surrounding topography. Adjacent natural topographic features were used to establish target design parameters for re-contouring and erosion control design.

Jan 1, 2001

Ceremonies for the induction of five mining industry pioneers into the National Mining Hall of Fame are scheduled for Saturday, Sept. 25, 2004 at the Las Vegas Hilton in Las Vegas, NV. The 17th Annual Mining Hall of Fame Induction banquet will begin with a reception at 6 p.m., followed by the dinner and program at 7 p.m. The five inductees are Georgius Agricola, David William Brunton, Herbert E. Goodman, David Ray Mitchell and Robert Peele. Georgius Agricola (1494-1555) wrote De ReMetallica, an original and valuable work that discussed everything known about mining during the first half of the 16th century. In De Re Metallica, Agricola reviewed practical means of finding ores, methods of surveying and mining, the assaying of ores, types and uses of mining machinery, smelting, mine administration and more. David William Brunton (1849-1927) is best know

Jan 1, 2004

By A. Supomo, A. Partanen, M. Mular

Although many SAG operators may agree that on-line measurement of SAG feed-size is an attractive notion, applying this information in a control strategy that recovers the investment, engineering time, and maintenance is not necessarily straightforward. The P. T. Freeport Split-Online system was justified based on the assumption that SAG feed-size could be used in a feed-forward control strategy either at the regulatory or expert system control level. Something like “as the feed size changes adjust the throughput to avoid under or overloading the mill” was envisioned. However, following installation and calibration, Cluster Analysis showed that such an approach would not be successful. However, the sensor has been successfully integrated into Freeport’s grinding control strategy other ways. It provides an input to the Kalman filter parameter estimator used in a model-based control strategy that optimizes throughput and grind. The Split sensor also provides a characteristic feed size parameter for use in an on-line work index estimator. This paper describes the calibration and installation of the Split SAG feed-size analyzer, and reviews the evolution of its use in the Freeport C3 grinding circuit control strategy.

Jan 1, 2001

By S. E. Phillipson

The Late Miocene San Cristobal Ag-Zn-Pb deposit represents syngenetic and epigenetic mineralization with low- and high-sulfidation characteristics. Geology is characterized by barren dacitic ring fracture domes, mineralized resurgent rhyodacite domes, strongly altered and mineralized tuffaceous lacustrine sedimentary rocks, and an extensive crystal-lithic tuff debris apron. The ore body is hosted by intra-cauldron sedimentary rocks and breccias. Fluid inclusions suggest that silver, lead, and zinc were transported as chloride complexes and precipitated by cooling in veins from <5 wt. % NaCl eq. fluids at 170°-215° C. Silver associated with resurgent rhyodacite was transported as a chloride complex and precipitated by increased H2S activity or increased fluid pH.

Jan 1, 2001

By Paul Lynch

"Since being reported to the 2012 UMI in Shanghai, the Cook Islands has been steadily developing for the commencement of it Seabed Minerals sector in its large Exclusive Economic Zone which contain a vast and unique Manganese Nodule resource, estimated at 10 billion tonnes1. At the 2013 UMI in Brazil, it was reported that the Seabed Minerals Act had commenced and all the necessary complex Technical aspects of this developmental work was being undertaken. At the 2014 UMI in Portugal, full details of the final developments leading to the opening of the Tender of Exploration Blocks in the Cook Islands EEZ will be presented in a brief but comprehensive method, using Poster displays, Powerpoint and active Website interaction. This will show the drafted Regulations, prepared on best international standards, to address both Licencing and Environmental requirements, to give clarity and security to the Resources Owner, industry and stakeholders. This work in being coordinated by the Cook Islands Seabed Minerals Authority, with the valuable collaboration of many international, regional and national stakeholders, including the Cook Islands NGOs, Marine Resources, Marine Park and National Environment Service."

Sep 1, 2014

The support of the roof in coal mines remains a critical safety issue with 3 fatalities from roof falls in 2007 and 430 injuries from roof falls in 2006. A snapshot survey by the authors of room design and support details as well as unplanned falls of ground in the industry revealed some useful data concerning support use, seam details, fall dimensions, bolt lengths and spacing and the stand-up time.

Jan 1, 2009

By Hugh Douglas

In the past two years recent increases in silver prices over levels that prevailed for many years have changed supply/demand patterns. On the supply side, a silver mining boom is in progress in the United States and elsewhere. On the demand side, traditional uses of silver by individuals are dropping while industry is conserving. These changes will alter the supply/demand balance and bring about more moderate rises in silver prices, which in turn will impact the mining industry.

Jan 1, 1981

By Leslie Burnside

Homestake Mining Co. set out to complete final reclamation at a former open-pit gold mine in west central Nevada. The goal was to exceed regulatory standards by satisfying the company&apos;s own high corporate standards for successful reclamation. Homestake&apos;s completion requirements challenged available technology due to the unsuitability of heap material as a growth medium, the harsh environmental conditions of the site and the region&apos;s lack of native growth medium. Accomplishing these goals required enlisting a multidisciplinary project team to develop, test and implement appropriate and cost-effective revegetation alternatives.

Jan 1, 1999

By H. S. Rathor

NTPC (National Thermal Power Corporation), a multi-unit organization, is generating 26% of India’s total power. This power is produced from its 14 coal based stations and 7 gas based stations. NTPC is entering into the business of power-distribution, power-trading, setting up of coal mines and diversification in non-conventional energy sector as well. For achieving the goal of the country “Power for All” NTPC has taken a giant stride by entering into Hydro Power generation which is also the cheapest and the cleanest renewable source of energy. In its pursuit for excellence, 800 MW Koldam Hydro Power Project is NTPC’s first venture in hydro sector. In Koldam, hydropower potential will be harnessed by constructing a 163m high earth and rock fill dam in a narrow gorge at upstream end of Bhakra reservoir. The river diversion is envisaged through two parallel, 14m finished diameter ‘horseshoe’ tunnels of length 901m and 934m at village Kian on the right bank, where the river forms a 180° loop. The diversion tunnels are designed to accommodate a flood of 6500m3/sec, taking into account the maximum probable discharge of 200 years return period. The tunnels pass through dolomite and limestone rock formations. The excavation of tunnels was done with drill and blast method. The excavation was attempted from both inlet and outlet faces. During geological investigation a rock fault was located at the outlet area. The location of the fault was such that it was passing through the edge of the Tunnel-1portal and around 30m away from the face of the Tunnel-2 portal. The quality of the rock at Inlet was also poor. To save the portals from slips, excavation of the tunnels was planned to start after the completion of the open excavation and its support system both at inlet and outlet. The tunnel excavation at inlet was envisaged by approaching the tunnels’ portal by constructing a road through 540EL bench and meeting the inlet portals on the upstream end, which would have been ready by mid2003, only after completion of the open excavation and its support system. To save time and cost, it was felt necessary to modify the planning by starting the tunnel excavation simultaneously along with open works both at inlet and outlet. The excavation at the inlet face of the tunnels started in December 2002 after rerouting the approach road to inlet portals through haulage road on the downstream and similarly Tunnel-1 at the outlet was started in the low cover area before completion of open area works. Thus the tunnel—heading excavation was started nearly 06 months early with the change of methodology.

Jan 1, 2005

By R. Sharma, S. Svoronos, S. Gupta, N. A. Abdel-Khalek

This paper presents the results of column flotation of a fine feed sample of Florida phosphate. A central composite design is used to study the main and interaction effects of parameters affecting column efficiency. The statistical design is also used to determine the optimum conditions. The results indicate that, depending on the experimental conditions, it is possible to achieve a concentrate of high grade and recovery. A concentration of 15 ppm of non-ionic frother is found to be enough to maximize the recovery at the pH of 9.5.

Jan 1, 1999

By D. W. Olson

The estimated value of natural gemstones produced from U.S. deposits during 2004 was $12.9 million. This was a 3-percent increase from that of 2003. U.S. gemstone production included agates, amber, beryl, coral, garnet, jade, jasper, opal, pearl, quartz, sapphire, shell, topaz, tourmaline, turquoise and other gem materials. More than 60 varieties of gemstones have been produced commercially from U.S. mines. But commercial mining of gemstones has never been extensively undertaken in the United States. Most of the deposits have been relatively small compared with other mining operations. In the United States, much of the current gemstone mining is conducted by collectors, gem clubs and hobbyists rather than business organizations.

Jan 1, 2005

By T. Mills, M. Evatz

Newmont’s Lone Tree Mine, located in northern Nevada, is an open pit gold operation supported by a standard truck and shovel mine production fleet (Caterpillar 785Bs and Hitachi EXs). Newmont continues to search for ways to decrease capital expenditure and lower operating cost, hence the implementation of the Ultra Light Body (ULW) concept. The fundamental idea associated with the ULWs is the increased payload potential. Economic justification comes from successful achievement of additional payload, within the truck’s rated GVW, without changing its loading and hauling characteristics. The increase in payload capacity allows equivalent tonnage movement using fewer trucks.

Jan 1, 2001