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By F. Maciosek, D. Denton, J. Johnson

Researchers from the Spokane Research Laboratory of the National Institute for Occupational Safety and Health and personnel from Coeur Silver Valley, Wallace, ID, conducted tests using rock strain strips and Split-Set rock bolts instrumented with strain gauges to monitor wall rock strain at the Galena Mine, Osburn, ID. The objective of the test was to identify whether strain on the rock bolts increased prior to a rock burst. Although results were inconclusive, researchers learned that the Split-Set rock bolts yielded in stick-slip fashion in the highly jointed walls of the stope. The bolts were also bent as stress was redistributed following blasting and subsequent movement along joints in the wall rocks.

Jan 1, 2004

The Bega granite at Whipstick, N.S.W., consists of a granite metasomatically altered to leucogranites and a spessartite-granite. The ore occurs in pipes controlled by jointing and shows evidence of post-depositional tectonic forces.The principal ore minerals are molybdenite and bismuthinite, with minor amounts of uraninite, pyrite, gold, bismuth, joseite A, joseite B, tetradymite, chalcopyrite, arsenopyrite, and skutterudite. The gangue minerals are microcline, albite, quartz, muscovite, and spessartite, with fluorite, chlorite, magnetite, and biotite as accessory minerals.The intrusion of granite was followed initially by ascending metasomatic fluids which penetrated along joints to be trapped in the domed roof of the intrusion to form the leucocratic granite. Iron-manganese-rich fluids metasomatically altered the granite to a spessartitegranite which is associated with the later deposited ore.Quartz veins and dykes of varying composition post date the ore deposition.

Jan 1, 1968

By David Meadows, John Starkey

"As part of the ongoing project development for the Tenke Fungurume Copper-Cobalt Project in the Democratic Republic of Congo, Phelps Dodge Corporation has examined methodologies for determining the size of grinding mills to support a 7000 mtpd operation. Six samples were tested by Hazen Research, Inc. (HRI) to obtain the JK parameters using the JK Drop Weight Test, standard Bond crushing, and rod mill work indices, abrasion indices and by Dawson for Bond Ball Mill Work Index tests using crushed feed, and Standard Autogenous Grinding Design (SAGDesign) Tests, patented by Outokumpu. (See reference 8 below).The comparison of these results gives context to how the various measurements relate to each other and how they can be used to obtain an accurate design for the grinding mills required for the Tenke Project. This is the first published direct comparison between JK Drop Weight, standard bond work indices, and SAGDesign test results. The SAGDesign test includes a SAG test followed by a Bond BM Wi test done on SAG ground material.INTRODUCTIONAfter the presentation of the paper “SAGDesign Testing – What It Is and Why It Works” at the recently concluded SAG 2006 Conference in Vancouver, a question was asked about how SAGDesign ore hardness measurements compared with other comminution tests, specifically the JK Drop Weight Test and the parameters that are derived from such testing. At that time it was noted that a paper was being prepared for the CMP Conference in January to show how various ore hardness measurements compare with each other when done on the same samples.This paper will therefore present the first such comparison using test results from the Phelps Dodge Tenke Fungurume Project where six composite samples were examined by the tests noted below. A seventh sample was tested at Dawson but not at other labs. The tests were done at four different laboratories listed below and included the tests shown."

Jan 1, 2007

By K Belanger, J. Mclachlan, F. Stober, G. Norval, B. Snider, A. Munsch, T. Koehler, E. Piantino, J. Carlos Queiroz

The project to rebuild the smelting furnaces at the Anglo American - Barro Alto ferronickel smelter, located in Goias, Brasil, was initiated in September 2013. To optimize the capital cost, while maximizing furnace integrity and robustness, a design basis giving flexibility to ore composition variation was developed in order to ensure sustained nameplate production. The resulting capital efficient, fasttracked project execution was accomplished through the creation of an integrated project team of Anglo American and Hatch through FEL 3 and FEL 4 phases of the project. The integrated team addressed the project challenges through a cooperative and versatile approach, created by access to knowledge, experience and systems in both Anglo American and Hatch. The team could operate at an optimized speed of execution, as demonstrated in the FEL 3 and FEL 4 completion durations, as well as efficiently mitigating any risks of increasing cost or delaying schedule by utilizing lessons learned and team knowledge from Anglo American on the original green-field project and Platinum smelters and Hatch on similar reference ferronickel furnace rebuilds. Other critical drivers of project cost minimization and revenue loss/generation (considering production revenue of each furnace) are scheduled durations for construction, commissioning and ramp-up. The integrated team commenced construction, commission and ramp-up planning almost one year in advance of the shutdown and this paper will discuss the strategies developed to reduce risks and optimize the construction schedule to mitigate revenue loss and optimize ramp-up time to sustained operation at nameplate capacity.

Jan 1, 2015

By JOHN G. RAYNER

An examination was made of the filtration characteristics of a haematite slurry using a range of polyacrylamide based flocculants in solutions containing up to 3 per cent sodium chloride. The polymers used were "high" and "Iow" molecular weight and had from 0 to 40 per cent charged groups.Increasing charge density tends to reduce the dose required to achieve optimum performance measured by filtration rate and by cake moisture. In general increased salt addition tends to increase the dosage required to achieve these optima. Both these observations result from the change in polymer extension and accord well with the bridging theory of flocculation.The dose required for optimal cake moisture is up to three times greater than that required for optimal filtration rate. This effect is reasonably consistent for all polymers studied and appears to be non-linearly dependent on salt concentration, with the difference being small at 0 and 3 per cent but quite significant at 1 per cent.

Jan 1, 1987

By J. E. Nesset

"Significant progress has been made over the past few years on characterizing and understanding the hydrodynamic properties of frothers and collectors and their effect on flotation performance. This new understanding of the relationship between chemistry and hydrodynamics has dramatic implications for how flotation circuits should be controlled and optimized. Previous work has shown that choosing a frother of the right ‘strength’ is critical to the optimization process, and the work and discussion presented here serve to strengthen the argument. In addition, we know that collector chemistry will also influence hydrodynamic properties and needs to be taken into consideration. To achieve the desired outcome, the overall system of reagents and operating parameters must be considered. This paper describes and discusses some of the findings from recent research on frother and collector chemistry effects (on hydrodynamics), and how this knowledge can be used to improve flotation performance. Examples from plant experience are discussed.INTRODUCTIONFrothers perform various functions in flotation but the primary ones are control of bubble size in the pulp zone and stabilization of the froth zone. Laskowski (2003) was among the first to try to capture both roles in characterizing frothers in order to provide a basis for frother selection for a given duty, as well as to explore the link between function and frother chemistry (structure). The method he used requires bubble size data and a frothing index; the procedure has been simplified by Cappuccitti and Finch (2008) using gas hold-up to substitute for bubble size, and froth height (without overflow) as the froth stability metric. The gas hold-up/froth height relationship will be referred to as ‘hydrodynamic characterization’. Essentially, the gas hold-up parameter reflects the sum of the hydrodynamic conditions in the pulp phase (water in this case), i.e. the effect of bubble size plus the apparent impact of the water surrounding the bubble due to the frother (Finch, Nesset and Acuna, 2008). Similarly, the stable froth height parameter reflects the sum of hydrodynamic conditions in the froth, i.e. the effect of bubble size undergoing coalescence plus the influence of the water in the lamellae and Plateau borders between bubbles. It could be argued that the gas hold-up/froth height relationship is a superior one to simple bubble size/froth index for discerning differences in frother behaviour"

Jan 1, 2010

By P. B. Leavenworth

Development in the Upper Texas Gulf Coast during 1945 resulted in the discovery of 23 new fields; one Miocene, eight Frio, three Cockfield-Yegua and eleven along the Wilcox trend. The Wilcox trend appears to he the most active at this time. Producing depths of the new Wilcox discoveries range from 2050 to 10,050 ft. Drilling along the Frio trend has been, for the greater part, projected to the deeper downdip sands. Eighteen of the new discoveries are classified as oil or condensate and five are gas discoveries.

Jan 1, 1946

By Rolf Birger Pedersen, Alden Ross Denny

"Synthetic Aperature Sonar (SAS) is a powerful tool for ultra-high resolution marine survey. The Kongsberg HiSAS system deployed on the HUGIN AUV has a rangeindependent resolution of 3x3 cm for sonar image and ~10x10cm for the interferometric bathymetry product [1]. This resolution is achievable for areas up to 50 km2 on a single survey mission providing huge multi-attribute datasets. This technology, originally designed for military and oil-industry applications, has the potential to revolutionize scientific seafloor mapping. The extreme resolution of this technique allows for deposit mapping in and around seafloor hydrothermal systems, including the discovery of extinct venting structures. By clearly distinguishing between volcanic and hydrothermal landscapes based on features below the resolution of conventional multibeam systems, SAS enables an entirely new level of hydrothermal deposit survey. Additionally due to the extreme resolution of this survey technology, repeat survey and change detection should allow centimeter-scale changes in deposit morphology to be routinely detected over an entire hydrothermally venting region. In collaboration with the EU funded MIDAS project, the Centre for Geobiology at the University of Bergen will deploy the HUGIN AUV this summer at two distinct shallow venting systems on the Arctic Mid-Ocean Ridge system. The AUV will collect repeat bathymetry at the Jan Mayen Vent Field, and extend the SAS coverage to include newly discovered venting sites. We will present the preliminary findings of this expedition, including the first deposit estimations made from full-resolution SAS mosaics."

Sep 1, 2014

By John H. Soule

Although known since 1902 , the Capitan iron deposits have not been mined mainly because of the low grade of the ore . A small amount of exploratory work carried on at an early date was reported . C. E. Johnson , district engineer of the Bureau of lines for New, Mexico , visited this propert , and as a result of preliminary sampling and mapping by the Bureau3/ and the Federal Géological Survey , an exploratory project was conducted during March , April , and liay 1944. Further mapping and logging of the vagon -drill samples was done by V. C. Kelly , geologist , of the Survey .

Mar 1, 1947

By W. W. Adams

Every man-hour of work performed in and about the coal mines of the United States had a 2-percent heavier death load from accidents in 1938 than in 1937. This is an unorthodox way of stating that the death rate per million man-hours of exposure or employment was 2 percent higher in 1938 than in 1937, increasing from 1.74 to 1.78. Thus the average miner had a 2-percent greater chance of being killed in 1938 than he had in 1937. The average quantity of coal resulting from 1 man-hour of work increased 3.6 percent -from 0.615 ton in 1937 to 0.637 ton in 1938. The production of the average ton of coal was accompanied by a slightly smaller loss of life in 1938 than in 1937, the accident rate being 2.793 per million tons in 1938 compared with 2.833 in 1937.

Jan 1, 1941

By B. Yu, N. Verbaan, A. Mezei

The recent 20 years witnessed a boom and bust in the nickel laterite industry. Most notoriously is the story of the first three Western Australian nickel laterite projects which all suffered major ramp-up issues. Many hard lessons were learned by the industry and it has been widely reported that the major contributing factors included insufficient testing as well as a limited understanding of the materials handling characteristics at the front-end stage of the flowsheet. This paper compares the current "race to production" in the REE industry to the laterite industry 20 years ago and addresses the fundamental question: ‘Have mining and exploration companies with rare earth projects learned from past lessons and are they doing sufficient and appropriate testwork to prevent failure’? The authors will provide the perspective of a commercial metallurgical laboratory that has gone through the laterite cycle and is active in the present REE cycle.

Jan 1, 2014

By Andre Vien, Jean-François Dupont

"Over the past several years, Svedala has developed a continuous charge monitor (CCM) for tumbling mills. It consists of a strain gauge embedded into a rubber lifter and associated electronics. This paper describes the installation and use of such a device on a SAG mill at the Holt-McDermott Mine. Comparison to measured static volumetric load and bearing pressure and inclusion of the measurement into a control strategy and its potential for condition monitoring is discussed. INTRODUCTIONWhile the measurement of load is very important in all kinds of grinding applications, the biggest benefits are expected from AG and SAG milling. This is what motivated Holt-McDermott to take a closer look at this problem, with a view to optimizing SAG mill performance.In many cases, the SAG mill control problem can be stated as maximizing throughput while avoiding a volumetric overload, with the other constraints (e.g. power, grind size, upstream/downstream equipment constraints, etc.) playing a less important role. This is certainly true at Holt-McDermott where the SAG mill is the production bottleneck about 90% of the time, and anything that can be done to increase SAG mill throughput will have a significant impact on operating profit.Although the goal of maximizing throughput while avoiding volumetric overload is simple to state, it has proven to be much more difficult to achieve. The mineral processing industry has expended a great deal of time and effort to devise control strategies in the pursuit of this objective. While much progress has been made, there is still room for considerable improvement. Across the industry it is probably fair to say that overloads occur relatively infrequently, but the real losses accrue as a result of the tendency to run rather conservatively."

Jan 1, 2001

By Jonas Olsson

"The picture of China as an antiquated continent is changing rapidly and fast-forwarding progress is a fact in most infrastructural fields. Mining is not an exception. China is today the largest producer of aluminum, coal, steel, zinc, tin, lead and manganese and the country’s mineral resources comprising approximately 12% of the global reserves ranks them number three in the world after US and Russia.In order to feed the growth industry is needed to take extra ordinary strides to improve supply of raw material and Chinese mines are continuously being upgraded with the latest western technology to meet the increasing domestic demand of base metals.In Anshan located in China’s northeast province Liaoning we find one of the fastest developing mining companies, Angang Iron & Steel Group Co. Ltd. With their six mines that together process approximately 60 M ton iron ore/year Angang Iron & Steel Group Co. Ltd is the largest iron ore company in China. The group’s thorough pre-studies and technical evaluations over the past five years have made them very successful in both plant upgrades of existing operations and green field projects.INTRODUCTIONWe live in a time when the world market is gradually acclimatising to the global consequences of “The China effect”. An effect caused by a formerly sleeping giant nation that during the last years has awakened and developed beyond comparison, primarily because of booming infrastructure projects and demand for capital and consumer goods"

Jan 1, 2006

"The mining industry uses many types of mineral and metallurgical plants to produce saleable product from ore mined. Plant design history has left current operations with a mixture of manual operation and various forms of automated process controls. Consequently, we typically see high variability in the continuous operations together with a shortfall in the attainment of full capacity, or higher utilisation of consumables.At a level of best practice, ‘Operational Performance Excellence’ focuses on process control, using automation and control systems to deliver process optimisation. This more sophisticated delivery is a great deal more difficult than the first stage of equipment selection / installation. It includes the appropriate selection of the right instrumentation, control system, key process knowledge, individuals with a solid control engineering background / experience, and the essential backing / support of the operations management team together leading to higher value delivery. Robust solutions can be realised, considerably minimising process variation, thus leading to process optimisation. This approach results in an easier, efficient and safer process while providing considerable returns for the plant owners.How variable are your processes, and do you maintain optimised process performance with dedicated resources, modern instrumentation, ‘best practice’ control systems and performance monitoring tools? In this paper, these questions and their possible answers are discussed."

Jan 1, 2014

By Elizabeth Varghese, Sanket Rawat, Prachuryya Kaushik, Ravi Kant Mittal

"Geo5 Software is gaining popularity worldwide due to its expediency in analysis and design of pile foundation. The analysis is based on various theoretical, empirical and semi-empirical methods available in existing literature and various country standards. Moreover, the ultimate resistance of pile in the software is based CSN 73 1002, Fellenius method, NAVFAC DM 7.2 and Tomlinson method. Due to the specificity in calculation of ultimate resistance, it becomes necessary to validate the results arrived using the software for better accuracy. Furthermore, the above-mentioned methods are not necessarily popular in every design offices. Therefore, an attempt has been made to predict the efficiency of Geo5-v15 software to analyze the pile foundation by comparing it with the results obtained using the analysis based on Indian Standard IS 2911:2010, performed with spreadsheet specifically designed for the same purpose. The accompanying outcome of the comparison and several shortcomings found in the design part associated with the software has been highlighted in the later part of the paper. Besides, the optimization tool present in the software is also described for the more efficient and economic design of pile foundation, hence contributing as practical aid to structural engineers.INTRODUCTIONThe analysis of individual pile foundation and pile in groups can be said to include the three main important parameters – Ultimate bearing capacity, Settlement and Structural Design. The first two parameters are to be evaluated to check the reliability of foundation against ultimate limit state and serviceability limit state. The third parameter includes the analysis of pile against both horizontal and vertical load. This parameter mainly intends to evaluate the size of foundation and the amount of reinforcement. Geo5 is a software which can expediently compute the above mentioned three parameters just by the mere input of the necessary factors. The ultimate bearing capacity analysis in Geo5 is based on various theoretical, empirical and semi-empirical methods available in existing literature and various country standards depending upon the drained and undrained condition of soil (Bowles, 1968; CSN 73 1002,1987; Felenius,1991; NAVFAC DM 7.2,1984; Tomlinson,1977). However, the method mentioned in IS 2911 (2010) is not the same and have slight variations in way of evaluating the parameters which affect ultimate bearing capacity. Therefore, it becomes necessary to evaluate the efficiency of Geo5 with respect to the value of ultimate bearing capacity and therefore, asserting the confidence in the software based method for the convenience of the designs in Indian Scenario. The present study aims to evaluate the efficiency of Geo5 v-15 software in predicting the ultimate bearing capacity of pile foundation. The results of the software are compared with the bearing capacity calculated using IS 2911 (2010) with the help of excel sheet. Moreover, as the software is frequently put under revision, therefore a comparison of this version has also been made with the latest version of Geo5 (2017) to check whether the latest revision has accounted for the discovered shortcomings. The design steps performed in the software is also shown. As Geo5 make use of IS 456 (2000) for the design purpose, hence it can be considered as reliable with respect to the estimate of the third parameter. Furthermore, the optimization process is also shown in the later part of the paper to emphasize the simplicity of the software in economizing the design cost."

Jan 1, 2017

By S Winter, G Klenowski

During longwall mining in the Bowen Basin, open tension cracks formed by overburden subsidence occur to a height of about 175 m above the mining horizon. Within this zone, water in aquifers or inundated workings will flow into the mine.At the Oaky Creek mines Aquila seam, open cut pits containing pit water overlie German Creek seam longwall panels at a height of about 105 m. The highly saline water is classified as contaminated and cannot be discharged off-site. Because alternative water storage facilities were not available, innovative water management solutions were needed to allow longwall mining to proceed without underground flooding.Computer modelling and underground inflow measurements have been completed to accurately determine inflow rates into longwall mines from overlying water sources at increasing overburden heights. Research work has also included determining cost-effective blanket treatment of final voids and reshaping spoil piles to minimise downward seepage.Ponded water overlying the Aquila low, Grasstree south and A6 pits required remedial works prior to longwall undermining to prevent flooding. In the Aquila low pit it was necessary to partition the pit and remove water overlying longwall 32. Two in-pit bridges were constructed by dozing and track compacting low wall spoil. The final void above the longwall panel was kept dry during undermining. Maximum recorded underground inflow rate was 30.0 L/s.The Grasstree south pit final void, part of the ramp and much of the spoil piles were inundated prior to undermining of 308 panel. A bridge and blanket were required to prevent ponding above the longwall. Maximum recorded inflow during undermining was 23.2 L/s.The pit A6 south final void, which contained dumped, saturated rejects and inundated highwall mining entries was undermined by longwall 36 at the Oaky No 1 underground mine. Because mapping of highwall entries was not available, the maximum calculated inflow rate of 73.0 L/s was based on all design entries being fully inundated. The actual inflow rate during longwall mining ranged up to 20.0 L/s.Water management improvements that have been implemented include greater use of contaminated pit water to wash coal, use of evaporation fans, and installation of a 6 ML/day reverse osmosis plant for water purification.CITATION:Klenowski, G and Winter, S, 2017. Inflows into longwall mines from inundated overlying workings, in Proceedings 13th AusIMM Underground Operators’ Conference 2017, pp 183–190 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Oct 16, 2017

By Forrest T. Moyer

[The safety record of the nonmetal mining industry during 1965 way worse than that of 1961 in all general measures s of injury experience except for a slight improvement in the number and frequency rate of nonfatal injuries Work fatalities in 1965 totaled al and occurred .it a frequencyrate of 0.29 and a severity rate of 1,711 per million man-hours of worktime. The fatality total was seven oven higher than to 1964 and the injury ratess increased d 32 and 28 present, respectively Thin total. of 2,172 nonmetal injuries u- in 1965 was 3.4 less than in 1964 and the frequency rate per million ion man-hours worked declined percent to 22.73 from: 23.14 in 1964. However, the 1965 nonfatal severity rate of 1,339 per million man-hours worked was 15 percent our the: d.96,1 rate of 1,160, This increases was largely attributable to two more permanent total and nine more permanent partial injuries. in 1965 than in the proceeding year. The average severity all injuries in 1965 was 132 days, 1-I. or charged per injury or 25 days more than in 1961. Injury experience in the nonmetal mining industry, including and excluding officeworkers, for the a-year period 1961-65 is shown in table 1. The average number of men working, on active days in 1963 was 48,429, or 635 fewer than in 1961. However, mines and mills, wore active an average: of 5 days more for a total of 277 in 1965, and each worker averaged 2,245 hours compared to 2', 190 hours in 1961. As a result, aggregate worktime of 108.7 million man-hours increased 1 percent over the 1964 total of 107.4 million hours.]

Jan 1, 1970

"At a current mining rate of 3,750 tons per day, La Mine Doyon is currently the largest gold mine in Canada. La Mine Doyon is an open pit gold mine located in the Abitibi area of Northwestern Quebec. The project is a joint venture between Soquem, a Quebec Crown Corporation in the resource development field and Lac Minerals Ltd., a publicly-held, resource development company. Lac Minerals is the managing company and operator of the project.Doyon went into production in 1980 on a very limited basis at 600 tons/day, and has seen a step wise increase to the current rate of 3,750 tons/day. Initially, all the ore was processed at Noranda Mines, Horne Division as flux for the copper smelter. The East Malartic Mill in Malartic was then upgraded and began processing Doyon ore. The third step in the progressive increase of throughput was the commissioning of the Doyon mill in November of 1982. Doyon ore is currently being processed at all three locations.During 1983, an exploration ramp was driven to explore the ore below the ultimate pit depth. Current plans indicate the sinking of a shaft and the commencement of underground mining during the next 2 or 3 years.Since its humble beginning, La Mine Doyon has always been a success; ore reserves have been extended to the east and the west and will soon be confirmed at depth, the mining and processing rates have been increased 6 fold, and the recovery has been increased from a designed recovery of 85% to over 95%. The intent of this paper is to trace the history and reasons for these rather dramatic improvements."

Jan 1, 1984

By D. A. Singer, J. C. Griffiths

"One of the most useful approaches to a complex problem is to model the system which gives rise to the problem and to perform simulations through the model to find appropriate solutions. The Engel Model may be used as such a simulator to investigate the problem of the exploration for natural resources.The Engel Model is based on a two-stage search procedure in which a known area (A) which contains m prizes is subjected to search by n coverings. During the first-stage search the sensor system records signals which may be a response from prizes (that is, true signals) or may be false. Signals tend to cluster around a prize and a cluster size consists of s signals. If a circle of radius R is drawn around each signal some will overlap and the overlap from s signals contains a prize. The cost of a single covering in which each point of the area comes under observation once, is designated E1. Second-stage detailed search is expensive and is confined to areas of overlap of s circles; it leads to the location of prizes. Second-stage search of the whole area costs Ea units. The expected value, V, of a prize is known and its development cost is E3 units.The sensor system characteristics are defined by the circle of radius R around a signal, which should be small compared with the total area A and enters the model as a parameter a x R2/A. The probability of a false signal during a single covering of a circle of radius I is a known constant, A.This model was applied to the search for uranium ore bodies using two different types of occurrence. In the first, the Wyoming Basin type, the area is relatively large (A = 1 496 square miles) and a few (m = 4) large prizes occur (expected value V = $30 million). In the second area, which represents the Ambrosia Lake region of New Mexico, the area is smaller (A = 212 square miles) and contains many (m = 200) smaller prizes (expectedvalue of a prize V,$2 million). The three costs, E1, E2, E3, are adjusted to the different circumstances in the two areas.Simulations were performed using n = 1 to 40 coverings with cluster sizes s = 0 to 19; the radius R was varied from 0.52 to 3 miles (and, therefore, a = 0.002 to 0.133 0, respectively, dependent on the area of interest). The value of A was varied from 0.01 to 0.10.Profitable programs were found over a wide range of the parameters; the two areas required different strategies to achieve maximum profit. In the Ambrosia Lake region a few passes (n = 4 to 6) with small cluster sizes (s = 2 to 6) are more profitable, whereas in the Wyoming Basin region a large number of passes (n = 35 to 40) and cluster sizes of s = 5 to 10 are most profitable.As pointed out by Allais (1957) the larger prizes are the most important in deciding the successful outcomes of exploration programs, and the profit margin in the search for a few large prizes is sufficient to yield success over a wide range of programs. Such programs require very large investments if they are to be successful.To refine the Engel Simulator as a decision-maker in selecting the most profitable exploration programs it is necessary to obtain firm estimates of the sensor system characteristics, that is, of R, a and ? (lambda)."

Jan 1, 2014

By Kenneth E. Hay

Researchers from the U.S. Bureau of Mines conducted a field study to assess the safety of remotely controlled mobile roof supports (MRS) in a retreat pillar mining operation, Data were collected to provide the Mine Health and Safety Administration with criteria needed to develop guidelines for MRS use and to determine if precursors could be identified that would alert miners to imminent roof falls. Two test sites at which two different support methods-MRS's and posts were used and were monitored to obtain information on entry stability. Pressure transducers and string pots were installed on all four MRS's to obtain loading and displacement information. and roof bolt load cells. sonic probes, extensometers, and survey targets were installed in the surrounding entries to obtain information on ground behavior. Results showed a larger increase in roof bolt loading and roof movement when MRS's were used, especially in the intersection area. Roof bolt loads in the entries showed decreases in load when the MRS's were set and increases up to 11,1 kN (2,500 lbf) when the MRS's were unloaded. Unloading of one MRS in a pair did not significantly increase load on the other. MRS's I and 2 usually had the higher loads, with these loads increasing as the pillars on each side were being mined. MRS 3 normally had lower loads than I and 2: however, it also experienced some very high loads when in the last position near the pushout. MRS 4 usually had the lowest loads, primarily because it was located near the solid pillar that was not being mined.

Jan 1, 1995