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By S. E. Younis

The mining industry is currently looking to better understand, anticipate, and be able to mitigate business and operational risks in order to deliver the rewards of risk taking, and to minimize the frequency and impact of risk on the downside. Assessing risk works from the premise that the identification and management of existing risks can be very challenging, especially when threats are not easy to detect, the likelihood of occurrence is difficult to gauge, and/or the consequences are uncertain. Some approach this as a ?check the box? task, even though fire and safety incidents continue to occur and investigations often find the hazard analyses did not properly identify the cause or consequence. You cannot engineer protective designs and safeguards for causes and consequences that have not been identified appropriately. For the mining industry, risk management is an important tool for making critical decisions and, in some cases, meeting regulatory requirements. Providing high-quality documentation that meets both regulatory and corporate requirements is critical for maintaining safe, uninterrupted mining operations. Risk management is a five-part process: 1. Identify the hazards and their causes, 2. Determine the hazard consequences, 3. Calculate the frequency of occurrence, 4. Quantify the risk associated with the system, process, or procedure, and 5. Provide feasible solutions for the risks

Jan 1, 2012

By J. Drzewiecki, J. Kabiesz

Coal mining using longwall methods of mining can lead to intense disturbances of undermined roof strata. The disturbances may extend beyond the extraction area and the resulted rock mass deformations will appear differentiated. In the case of stiff and undermined roof strata, the energy stored in these rock masses may be frequently dissipated in the form of high-energy seismic tremors. Such events can occur if these strata should fail or „free themselves” either from the constrainment of rock environment or from adjacent strata. It has also been found that the amount of the stored energy closely depends on the size and/or slenderness of these strata. Thus, it would be possible to apply specific preventive measures to reduce the energy of mining – induced seismic tremors. The methods are based on artificial disintegration of the structure of energy – storing strata. One of the most efficient methods is a method of directional hydraulic fracturing, which is regarded as an alternative solution from the traditional blasting and hydraulic methods.

Jan 1, 2003

By David A. Jack

The Mission Valley Viaduct is located in San Diego, California. This structure is the intersection of Interstate 8 and 805. The project consists of the main viaduct, 8 connecting ramps, and one highway overpass. This job was originally built back in the 70's. After the Loma Prieta Earthquake in 1989, Caltrans began an aggressive program to seismic retrofit all of its bridges throughout the state. Most retrofit designs required major upgrades to the existing footings. These footing upgrades consisted of either driven or drilled shaft piling. The existing footings of the Mission Valley interchange were supported on driven H pile. The soils throughout the site were dense sands and gravels, cobbles, occasional boulders with a dense sandstone bearing strata, which varied through out the site. It was this sandstone strata that the engineers designed their pile tips around. High ground water in sandy soils created a high probability of liquefaction in all of the upper stratas.

Jan 1, 1998

By Arthur Lieu

The mill effluent treatment circuit (Bulk Neutralization (BN)) in the Cameco Key Lake Operation was modified in 2008 to enhance the removal efficiency of selenium (Se) and molybdenum (Mo) from the mill process water. This modification was completed in part due to increased knowledge of the effects these elements have on biota. In addition, legacy effects from the historical operation of the Key Lake mill in regards to Se and Mo were shown to have an effect on the regional biota in the downstream receptors. This was a challenging initiative as there was no off the shelf technology available and the removal process had to be incorporated into an existing (brownfield) process. These modifications have resulted in significant reduction in the concentration of these elements in the Key Lake mill effluent. The removal efficiency for Se and Mo in the modified circuit has increased to 95% and 75%. As a result, concentrations of Se and Mo are now consistently less than 0.4 mg/l and 0.02 mg/l. In addition, the Se and Mo precipitates formed were extensively studied to ensure long-term geochemical stability in the Key Lake in-pit tailings facility. This presentation will provide additional detail on the hydrometallurgical removal mechanisms and process modifications required in the Key Lake BN circuit to remove these elements to trace levels.

Aug 1, 2010

By Glen A. White

The level of impact and mitigating measures that are forecast in an environmental assessment (EA) for a new, or significantly modified, metallurgical processing facility or mine are taking on increasing importance during the subsequent life of the facility. The basic premise is that one is authorized to operate within the envelope defined by the approved EA. Operations inevitably change as they develop and mature, and at some point, one is faced with the prospect of re-doing the original EA work. This can lead to significant development delays. Cameco Corporation (Cameco) has played a major role in developing the northern Saskatchewan uranium mining industry over the past decade. Through the EA process, the company has developed ideas on what works well in generating approvals that give the operator some future flexibility. Early introduction of concepts for potentially different mining and processing methods, as well as contingency plans if things do not work out exactly as predicted in the original EA, can make subsequent regulatory approval for change a more efficient process. One must also preserve the principles of open consultation upon which the EA process was originally based. As such, involvement and support from local communities and other stakeholders is required to ensure the long-term success of the EA process.

May 1, 2004

The heap leaching of base metal ores can be applied within a number of different scenarios, each requiring its own set of parameters to be determined during the metallurgical testwork programme. The occurrence of acid-gangue reactions and its concomitant precipitation reactions is a factor common to all cases, and requires that the optimal irrigation acid strength be found that optimises the combination of extraction kinetics, acid consumption and possible premature blinding of the heap due to precipitation reactions. For the heap bioleaching of base metal sulphide ores the oxygen requirement needs to be determined for the design of the aeration system, and the operating conditions employed need to also facilitate bacterial growth over and above the acid strength optimisation mentioned above. For the heap bioleaching of chalcopyrite, the need to preserve heat in the heap becomes yet a further parameter of critical importance. For the heap leaching of uranium ore a choice is required between either chemical or bacterial oxidation, based on economic and processing factors. Frequently the operating parameters need to be determined for a circuit in which heap leaching is combined with tank leaching and/or pressure leaching. The processing implications and metallurgical testwork approach for each case is discussed.

Jan 1, 2007

By K. Awuah-Offei

The objective of asphalt mix design is to produce a mix with optimal performance using available aggregate stockpiles. Often, this process does not take into consideration aggregate plant stockpile inventories or the cost of aggregate in the mix. This is due to the lack of tools that enable the lab technician or the engineer to optimize the mix for good performance while reducing the cost of aggregate and managing the stockpile inventory levels. The Bailey method provides useful guidance on aggregate gradation selection for optimal performance. This work presents a linear programming model of the asphalt mix design problem. The algorithm is implemented in MATLAB as an Asphalt Mix Design Optimization (AMIDO) program. The program is successfully validated with real-life data. The results show that AMIDO can be used to successfully produce any mix design with known Bailey method ratios. Also, RAP can be included in a design easily by making use of the Bailey method ratios and AMIDO. This work improves the state-of-the-art in asphalt mix design for dense graded mixes and could potentially be modified for other mixes.

Jan 1, 2009

By S. Underwood

The tracer gas method of conducting ventilation surveys is a means of determining air quantity in underground mines with knowledge of the concentration of the tracer in the atmosphere and the flow rate at which the tracer is being released. The technique is useful in inaccessible areas of underground mines and areas where traditional point measurement of velocity is not practical. Sulfur hexafluoride (SF6) is the industry standard tracer(Kennedy 1987) used in underground mines because it is safe, stable, and not naturally occurring in the mine environment. The implementation of a second tracer will increase the versatility of the tracer gas technique allowing for simultaneous releases for the study of interrelated ventilation circuits, and for conducting multiple experiments in less time. This paper will detail the selection of perfluoromethylcyclohexane (PMCH) as a novel tracer with sensitivity, physical properties, and analysis characteristics similar to SF6. Methods for the release of liquid PMCH into underground mines will be recommended, and the vulnerabilities of sample loss due to condensation of vapor PMCH will be explored. Finally, the benefits and implications of using PMCH as a second tracer will be discussed.

Jan 1, 2012

By P. E. Halbach

On June 26, 1988, the Jade Hydrothermal Field was discovered in the Okinawa Trough by the German RV Sonne. This research cruise has taken place within the scope of a German-Japanese cooperative project. The Okinawa Trough, located between the Ryukyu Island Chain and the east coast of China, is an active backarc-basin formed by extension within the continental lithosphere. The Ryukyu arc consists of a nonvolcanic outer arc, forming the main island chain and representing compressive highs of the Asian continental margin, and an inner arc with present-day volcanism in its northern part (Sibuet et al. 1988). The valleys and ridges of the trough are cut across by transverse faults, giving rise to younger volcanic intrusions. The Jade Hydrothermal Field was detected in a caldera-like structure. It is. located at about 27°15,0'N and 127°04,5'E with a maxi- mum water depth of about 1650 m. Data of heat flow measurements show a high anomaly in the cauldron basin with values ranging from around 100 to 800 mw/m2 (Halbach et al. 1989). The hydrothermal vent area was discovered in the northern part of the inside northeast slope of the cauldron in a water depth between about 1300 and 1500 m. We identified different varieties of hydrothermal

Jan 1, 1989

By James P. Stewart

This case history describes the engineering design and construction for the Contractor of a 35-ft-deep excavation for an 800-square-foot addition to an existing sewage pump station. The site posed unexpected geotechnical complications that included deep gravelly soil, a history of local construction difficulties, groundwater consisting of heavy salt brine, and the need to underpin the existing pump station. The project took an interesting twist when the Owner issued a change order limiting the dewatering discharge to a fraction of that required to lower the water table. This documents the interesting circumstances of this job and documents the unusual subsurface conditions in the Syracuse, NY Lakefront area.

Jan 1, 2003

By Corry Goumans, Dwayne Wallace

"On July 1, 1997, a rockslide occurred on the I-40 in Hayward County, North Carolina that completelyblocked all lanes and disrupted traffic flow in the region. Remedial measures were undertakenimmediately in order to open traffic, however on-going geotechnical investigation revealed stabilityconcerns that necessitated closing the highway to ensure public safety. Access to the top of the slope was available only from the bottom of the slide on the Interstate I-40. Excavation and trim blasting started from the top and along the west slope of the failure, however, additional geotechnical evaluation indicated that slope stability remedial measures were required to support the western rock slope mass."

Jan 1, 1999

By Raymond B. Ladoo

"The increasing realization of the fire hazards involved in the use of wooden shingles caused the National Lumber Manufacturers' Association to beginsome five years ago a search for a suitable fire-resistant paint. The problem was submitted to the Educational Bureau of the Paint Manufacturers' Association of the United States and work was started by Mr. Henry L. Gardner at the Institute of Industrial Research, Washington D.C. in collaboration with Dr. Herman von Schrenk, a timber expert of St. Louis.The results of this,work have been described by Heckel, in ""Asbestos"", (Heckel G.B., Asbestos in the Paint Industry, Asbestos, Vol. 2, July, 1920,pp.- 5-10).,,who gives the following formula for one of the colors as typical: It will be noted from this formula that ""asbestine"" forms 33% of the total liquid pigment by weight or 31.8% of the solid constituents. Hockel in the article referred to describes this paint,as ""asbestiform"" and assumes since ""asbestine"" is magnesium silicate it must be the chrysetile variety of ""Asbestine"", however, is not asbestos but is a trade name for a fibrous variety of talc mined in the Gouverneur district, St. Lawrence County, New York. This rather natural error persists through the article and credits asbestos with many desirable properties which are characteristics of talc."

Aug 1, 1920

By L. Yuan, A. C. Smith

To provide insights for the optimization of ventilation systems for U.S. underground coal mines facing both methane control and spontaneous combustion issues, a computational fluid dynamics (CFD) study was conducted to model the potential for spontaneous heating in longwall gob areas. A two longwall panel district using a bleeder ventilation system with a stationary longwall face was simulated. The permeability and porosity profiles for the longwall gob were generated from a geotechnical model and were used as inputs for the CFD modeling. In this study, the effect of methane emissions from the mined coal seam, including the longwall face and overlying rider seam reservoirs on the gob gas distribution was considered. The spontaneous heating is modeled as the low-temperature oxidation of coal in the gob using kinetic data obtained from previous laboratory-scale spontaneous-combustion studies. Unsteady state simulations were conducted, and the effects of the coal’s apparent activation energy and reaction surface area on the spontaneous heating process were also examined.1

Papers presented at two joint meetings of the Mineral Industry Education Division, Geophysics Committee, the American Geophysical Union and the Committee on College Curricula of the American Association of Petroleum Geologists, at the A I M E meeting in New York on Feb 17 and 18, 1941 At the first meeting, the Musing Geology Committee, the Society of Economic Geologists and the Committee on Applications of Geology of the American Association of Petroleum Geologists also took part [ ]

Jan 1, 1941

Papers presented at two joint meetings of the Mineral Industry Education Division, Geophysics Committee, the American Geophysical Union and the Committee on College Curricula of the American Association of Petroleum Geologists, at the A I M E meeting in New York on Feb 17 and 18, 1941 At the first meeting, the Musing Geology Committee, the Society of Economic Geologists and the Committee on Applications of Geology of the American Association of Petroleum Geologists also took part [ ]

Jan 1, 1941

By Y. Tao

The features of the teeter bed separator and its application in the coarse slime separation of Chengjiao coal preparation plant were discussed. The relationship between the coarse slime separation efficiency by TBS and the particle size were studied, and the influence of using TBS on dense medium consumption and oil consumption were investigated, it increased the clean coal yield and the comprehensive recovery of the whole plant, and brought huge economic benefits to Chengjiao coal preparation plant.

Jan 1, 2011

By W. J. Van Den Berg, J. G. Taylor

The paper discusses the introduction of blindhole boring on the South African gold mines of Anglo American Corporation. It covers the boring trials conducted, and outlines the progress made in the development of blindhole borers. The operating costs, and performances, of the latest 1,52 m diameter borer are given. Future trends and requirements In the application and design of blindhole borers are discussed, as well as factors that are of importance in the design of future machines.

Jan 1, 1978

By D. H. Gieskieng

E. H. BRONSON*—I find this paper very interesting, except that I am not able to understand the derivation of the so-called "realization factor." This factor is defined as the ratio of the size of square opening passing all the feed to the gape of the receiving opening. By this I presume the author means the size of rock feed to the width of crusher opening. So if we fed a 12 in. rock to a 16 by

Jan 1, 1950

The Western Australian Mineral Sands Industry has tried a number of different mining methods to efficiently exploit the potentially very large reserves of mineral sands in this state.The size of the operation, the location, the type and composition of the orebody contribute towards the choice of current mining techniques.The methods applied to these areas are described as well as reference made to other techniques which will . make possible the exploitation of lower grade reserves.

Jan 1, 1986

By Terry Quinlan

The financial evaluation of an orebody uses estimates for the grade of ore produced during each year for the life of the mine. Assay data from the Dolphin Scheelite Mine is used to estimate grades by the Polygonal, Ellipsoidal and Disjunctive Kriging Methods. The results are compared with simulated production data, to show the existence of a bias associated with each method. The affect of bias on the financial evaluation of a theoretical model ia assessed.

Jan 1, 1979