Search Documents

By Miguel Angel Ibarra

This paper describes the results of a digital computer simulation study in which the impact of the proposed truck dispatching on the overall mine productivity was investigated for an operating open pit mine. In the study, the existing operation was first simulated for a one-month period, using both the actual time study data and the computed cycle times. By adjusting certain input parameters to the simulation program, the actual one month production was first duplicated through simulation. Afterwards, the operation was again simulated in a dispatch mode. Comparison of simulation results under the dispatch mode, with the initial base case simulation results, showed a definite improvement in overall productivity with dispatching; i.e., approximately 10% gain for the operation. As expected, the results also showed that the extent of possible improvement did vary with the particular pit configuration being investigated.

Jan 1, 1980

By Duport. P. J.

INTRODUCTION In February 1981, the Canadian Institute for Radiation Safety (CAIRS) initiated a routine Personal Alpha Dosimetry service for personnel of the Canadian uranium mining industry. This service is based on the use of the [Personal Alpha Dosimeter] developed by the French Atomic Energy Commission (CEA). The origins of personal alpha dosimetry and its rational are briefly described. Technical and organizational aspects of a routine personal alpha dosimetry service are outlined in this paper. HISTORICAL BACKGROUND International recommendations (1) and Canadian regulations have established Maximum Permissible Exposures (MPE) for each source of radiation exposure. Uranium workers in mines and mills are exposed to external radiation ( [y] rays) and to internal radiations ( [B] and [a] particles) which are delivered to the respiratory track by airborne alpha emitters (Rn and Th daughters and Long Lived Dust). To date, dosimetry for uranium workers has been performed by area monitoring/collective dosimetry. In North America the concentration of radon daughters is routinely measured by grab samples taken at the work place and by on-site gross alpha counting. The concentration of potential alpha energy is then calculated (usually by Kusnetz method) and expressed in Working Levels (WL). The time spent by each worker at a given work place is determined from his time sheets and used to calculate the individual monthly exposures to airborne alpha emitters, which is then expressed in Working Level Months (WLM). The uncertainties attached to such a procedure are obvious even in the case of frequent grab samplings and can be expected to lead to an underestimation of individual doses. Among fifteen possible sources identified in a mine situation, (2) four may stretch the standard deviation of the measurements' distribution, nine may lead to an underestimation and two may lead to either an underestimation or to an overestimation. To improve this situation, in 1971 the Atomic Energy Commission began studying the use of personal alpha dosimeters to determine individual exposures from the airborne alpha emitters encountered in the uranium industry environments. Criteria for a Personal Alpha Dosimeter In order to minimize the difficulties encountered in determining exposures received by uranium workers, the CEA in co-operation with the Atomic Energy Control Board of Canada (AECB), has developed a set of criteria for personal alpha dosimeters. Exposures may be determined easily and accurately using this criteria. Autonomy The dosimeter must operate for at least 10 to 12 hours. Excess time spent in the mine or in the facility may possibly be related to an accidental situation causing unusual levels of radioactivity. Since the dosimeter may be needed in non-underground settings where a cap lamp is not used, full autonomy is desirable. Maintenance, Periodicity of Reading In order to complement other dosimetry systems, the personal alpha dosimeter should be read monthly when the filter should also be changed. Routine air flow checks can be made according to local conditions (e.g. diesel loading). Radioisotopes Identification Since the exposure unit (WLM) is based on the concentration of potential alpha energy in the air, the personal alpha dosimeter should be capable of identifying each short lived alpha emitter included in the calculation of the WI, and WLM. Permanent Exposure Record Three points may be considered here: 1. In many countries, lung cancer in uranium workers is a compensable occupational disease. In some instances, compensation is awarded when it can be proven that the worker has received an exposure above a certain limit. The present uncertainty of the individual exposure makes the compensation procedure difficult. 2. By design, a personal alpha dosimeter must representatively sample all airborne particles, ranging in size from the unattached fraction to the upper limit of respirable aerosols (0.001 to 5 µm). The dosimeter must offer minimal resistance to the penetration of these aerosols. While the mining/ milling environment presents harsh conditions which may accidentally contaminate the dosimeter, it is important to be able to distinguish these cases of contamination and still obtain accurate readings. 3. A dependable dose register is most valuable for further epidimiological studies. The dependability of such a data base increases with the possibility of a second assessment of the dosimeters' reading (filter, film).

Jan 1, 1981

By James S. Browning

This article describes research conducted by the University of Alabama's Mineral Resources Institute on removing sulfur from coal using a combination of gravity concentration and flotation methods. The research used the gravity and centrifugal force capabilities of Humphrey's spiral to remove part of the pyritic sulfur and ash. Flotation of the Humphrey's spiral coal concentrate removed additional sulfur and ash. In addition to obtaining good recoveries of high quality coal, the tests demonstrated that pyrite in the wastes could be isolated as enriched flotation products by the combined gravity-flotation approach. Domestic coal production in 1980 reached a record 757 Mt (835 million st). Forecasts are that coal production and use will approach 907 Mt (1 billion st) by 1985, with much of the increased production being used for electrical generation. Of current production, it is estimated that about 454 Mt (500 million st) of coal nationwide are subjected to some degree of cleaning, ranging from crushing and screening to gravity concentration and flotation. With expanded coal production and more rigid controls placed on coal combustion, it is reasonable to assume that the tonnage subjected to some form of preparation will increase, with time, thereby adding to the burden of coal rejects being generated. A major problem associated with increased coal use for electricity generation is the need for utilities to conform to emerging federal air quality standards for sulfur oxide emissions from power plants. To a lesser extent, other industrial operations burning coal face a similar situation. Controlling sulfur oxide emissions by using low-sulfur coal or resorting to stack gas desulfurization are two recognized approaches, but removing sulfur from the coal, if possible, by physical beneficiation before combustion is preferred because of its simplicity and lower cost. Reducing the inorganic sulfur in coal to tolerable limits by physical beneficiation, including flotation, as now practiced, is still relatively inefficient and has not kept pace with the more sophisticated physical beneficiation approaches generally employed by the nonfuel minerals industry. As one phase of a broad program conducted by the Mineral Resources Institute at the University of Alabama on sampling and evaluating impounded fine size waste coal, tests were made using samples from two impoundments to determine the quality of coal recoverable by a combination of Humphrey's spiral concentration and flotation. Particular attention was given to organic and inorganic sulfur deportment and distribution in the various products. Another objective was to determine if pyrite in the waste could be recovered for possible marketing. The use of Humphrey's spirals to concentrate fine coal was practiced as early as 1947. At that time, the Hudson Coal Co. used spirals to concentrate anthracite fines. In 1950, spirals were used to treat fine-size bituminous coal and later, in 1976, spirals were reportedly used for removing pyrite from fine-size coal. More recent investigations have discussed the use of Humphrey's spirals for treating fine-size waste coal in Alabama. Samples Description Washer waste samples were obtained from two impoundments. One sample was representative of waste generated during washing steam coal from the American, Pratt, and Nickel plate seams in Alabama. The other sample represented metallurgical coal washer waste from processing coal from the Carter, Johnson, and Milldale seams. Partial samples analyses are shown in Table 1, and screen analyses of the samples are given in Tables 2 and 3. Screen ana¬lyses showed that one sample contained about 4% of material coarser than 2 mm (10 mesh) and the other contained about 13% of plus 2 mm (10 mesh) material. Also, the analyses indicated that ash and sulfur increased as the material's particle size decreased. Experimental Laboratory Tests Sink and float tests using a heavy liquid (1.4 specific gravity) were made on the different screen sizes shown in Tables 2 and 3 to determine the effectiveness of gravity concentration for separating coal from pyrite and other gangue constituents. Tests indicated that gravity separation, under optimum conditions, could be expected to yield coal products containing 10-12% ash, and 0.2-0.3% pyritic sulfur. Good coal recoveries could also be expected. Using sink-float tests as a guide, tests were made in a Humphrey's spiral by a procedure in which a 90-135 kg (200-300 lb) portion of the

Jan 8, 1982

By Marreros D. Oscar

La perforación y la voladura son mecanismos que suministran material adecuadamente roto al equipo de carguío. La efectividad de ambos depende de la evaluación de la perforadora y de los explosivos a utilizar. En esta perspectiva, el presente trabajo describe los parámetros necesarios para evaluar los requerimientos de perforadoras en una mina nueva. El proceso de selección y evaluación conlleva una optimización económica del equipo de perforación para cumplir el plan de minado, asegurando la producción t reduciendo los riesgos financieros. Asimismo, se presenta el análisis de inversión con la técnica de flujo de caja descontado.

Aug 26, 1988

By A. Mahmoudkhani

Primary cementing is the process of placing cement in the annulus between the casing and the formations exposed to the wellbore. Portland cement was first used in 1903 in the Lopoc Field in California for well cementing. Since then, the major objective of primary cementing has always been to provide zonal isolation in oil, gas and water wells, i.e. to exclude fluid(s) in one zone from another zone in the well. To achieve this objective a hydraulic seal must be created between the casing and cement and between the cement and the formations, while at the same time preventing fluid channels in the cement sheath. This requirement makes primary cementing the most important operation performed on a well. Without complete isolation in the wellbore, the well may never reach its full producing potential. The industry knowledge on cements relies heavily on empirical data, but the chemistry, physics and structure of cement are not fully understood yet. The strength of concrete can be increased essentially by reducing its porosity through optimizing the size distribution of its components and filling the residual porosity of the hydrated cement phase with inorganic fillers. This approach has successfully utilized in different ways and several technologies for placing high performance oil and gas well cements have been developed over the last few decades. There are reasons to believe that the next source of improvement will lie in the fine-tuning of the hydrates themselves and of the different parameters that drive short (ionic?covalent bonding) and long (ionic correlation) interactions.

Jan 1, 2012

By Ciro Manolo Alegre Huamán

El presente texto describe la metodología para el desarrollo del planeamiento de minado subterráneo a través del software minero y de técnicas matemáticas modernas. Así también es importante la base de datos geológica que servirá como soporte para generar los modelos geológicos y geotécnicos a partir de los cuales, se obtiene el modelo de recursos mineros y, consecuentemente, las reservas mineras, que es donde se soporta el planeamiento de minado para una operación minera subterránea.

Jun 1, 2012

By M. L. Goble

"Inco Metals Ltd. (Manitoba Division) operates a mining, milling, smelting and refining complex, 500 miles north of Winnipeg in central Manitoba. The Thompson Mill is presently operating at 12,000 S.T.P.D. on ore from both underground and open pit mines. The ore is treated in two separate milling and flotation circuits utilizing a common crushing system which is located inside the main mill building. The milling facility employs approximately 43 operating employees, 30 maintenance employees and 20 staff in supervisory or process development roles.In recent years an increasing awareness of the potential hazards of contaminants in the work place has made it mandatory that all employers maintain careful and accurate records of the work environment to which each employee has been exposed during his working career.The importance of this record keeping and general observation of the work place cannot be over emphasized. Proper monitoring of the work place provides an accurate and complete record of the contaminants and physical agents to which an employee is exposed during his work career. This can aid in studies which might be conducted in the future and can also be used as a basis for instituting improvements to the workplace."

Jan 1, 1980

By Burton H. Boyum

The paper generally reviews the iron ore occurrences and regional geology of Western Australia, but features in particular the mesa deposits of PJasic Materials - Cliffs International. Initial production is planned from a aeries of mesa deposits of Eocene-Oligocene age. The ore is oölitic to pisolitic goethite and hematite. Source of the iron in the mesa deposits is thought to be from the Precambrian iron-formations. The geology and occurrences of the mesa iron ore deposits are summarized and illustrated.

Jan 1, 1964

By S. G. Ozkan

An investigation was carried out into the effect of physical parameters, such as particle size of the sample, residence time, solid/liquid ratio and impeller speed in the flotation cell, on the solubility in soft tap-water of colemanite (calcium-bearing borate) from Emet, in Turkey. Solubility increased steadily with residence time from 5 to 20 min but only minimally thereafter. There was a similar increase with impeller speed from 500 to 1 500 rev/min, beyond which a solubility of around 1.05 g/l was again established. There was a slight decline in solubility as the solid/liquid ratio was increased from 1 to 30%, with stable values around 1.05 g/l at a 20% ratio, while a sharp decrease was observed with decrease in size down to the -20 micrometre fraction. The effect of solubility should be taken into account if the application of a wet-processing method is being considered for the ore, while it can also result in losses of material during handling and storage

Jun 21, 1905

Coal bursts are one of the least understood yet the most critical hazards in underground coal mines. The ground motions induced by seismic events can trigger unstable failure of coal and rock mass and degrade the surroundings of an excavation. Therefore, the characteristics of ground motions should be fully investigated for an improved burst risk management. This paper analyzes ground motion features of a longwall panel from a typical underground burst-prone coal mine in China. The results showed that most of the ground motions on roadways were hardly initiate coal bursts due to insignificant energy input to the damage. The intensity of ground motions in near-field zone were nearly 20 times higher than those in far-field zone. The strongest vibration on roadway was induced by a coal burst with energy of 28,600 kJ, which can cause ground motion of 0.77 m/s and equivalent dynamic stress of 14.69 MPa. The findings of this paper can improve the assessment of seismic risks and its management.

Jan 7, 2020

To improve communications between mine workings and surface locations during emergency situations and for administrative purposes. The Approach: Development of a device for interconnecting phone systems which permits two-way communication between a public telephone and a mine pagerphone by authorized personnel. How It Works: The system, developed by personnel at the Bureau's Pittsburgh (Pa.) Mining and Safety Research Center, makes connections between the public phone line and mine pagerphone line. As shown in Fig. 1., incoming calls are sensed by the ring detector (4) and the system "answers" the call electronically. To reach the pagerphone system, the caller inserts an audible tone of fixed frequency through the microphone of his telephone. This tone is produced by a miniature, pocket-carried tone generator and is detected by a tone recognition circuit (5). When this hap-pens, relay, switching, and logic circuitry (6) closes the connections between the two phone systems. Simultaneously, a page activator (9) places a DC paging voltage on the mine phone line.

Jan 1, 1974

By L. M. Sekhukhune

The atmospheric leaching of copper-bearing matte by acidic ferric chloride solution was studied at the laboratory scale. The aim was to achieve maximum copper and nickel recovery by investigating the mechanisms of leaching, as well as identifying the effect of temperature, and concentration of ferric chloride and oxygen. Djurleite (Cu1.96S), hazelwoodite (Ni3S2), and Ni alloy were the primary phases detected in the matte. The quantitative composition of the matte was Cu 31%, Ni 50%, S 13%. Fe and Co constituted 2%, with platinum group metals (PGMs) accounting for 0.5%. A maximum nickel extraction of 98% was achieved using two-stage oxidative leaching at 90°C and 11 g/L Fe3+ as compared to 65% under non-oxidative conditions. A copper extraction of 99% was achieved in the first 45 minutes using two-stage non-oxidative leaching, and copper was recovered from solution by cementation. Three processes took place simultaneously throughout the leaching process, namely: dissolution, cementation/ metathesis, and oxidation. The leaching process was found to be diffusioncontrolled.

Jan 1, 2014

By Don Peel

Mineral aggregate, the most widely used mineral resource globally, has attracted little academic or public interest. Of all mining developments, the aggregate resource is seldom factored into resource management decisions. This lack of recognition to the strategic aggregate resource has significant economic, environmental, and social implications. Impact to the economics, the environment, and the community coincide with the key elements of the United Nations concept of ?sustainable development?. To build on the concept, the mining sector contracted the International Institute for Environment and Development to assess how mining activity contributes to sustainability. As a result, a useful assessment process was developed by the Mining, Minerals and Sustainable Development (MMSD) Task Group entitled ?Seven Questions to Sustainability: How to Assess the Contribution of Mining and Mineral Activities.? In Alberta, recent opposition to mineral resource development by community residents offers an opportunity to employ the MMSD?s assessment procedure. The public opposition to the mining activity was addressed through a stakeholder planning process initiated by the municipal council of Sturgeon County, Alberta. As a result the Calahoo/Villeneuve Area Structure Plan (CASP) was formulated and adopted. To measure the effectiveness of the CASP planning process in terms of sustainability, this paper applies the MMSD?s Seven Question assessment to the Calahoo/Villeneuve Area Structure Plan.

May 1, 2004

By Alan J. Lutenegger

Some years ago, a method was developed to incorporate a grout column around square-shaft helical screw-piles and anchors to increase shaft buckling resistance under compression loading. An additional benefit of this grouted shaft is to increase the load capacity in both compression and tension, depending on the geometry of the lead helical section and the soil conditions. Because of the unique construction procedure, the contribution of the shaft to the total capacity has largely been unknown. The behavior of grouted shaft helical anchors in clay was investigated by performing full-scale axial uplift (tension) load tests on a series of anchors installed at the University of Massachusetts Geotechnical Test Site. In order to isolate the contribution of the grouted shaft to the total load capacity, anchors were installed with a wooden dowel connection between the lead helical section and extension sections on three of the four anchors so that only the shaft resistance would be measured during the load tests. The grouted shafts ranged in length from 10 to 30 ft (3 to 9 m). Initial tests were performed approximately 5½ months after installation. Nearly four years after the initial tests were performed, the tests were repeated to evaluate any significant change in capacity with time and/or repeat testing (preshearing). The soil conditions at the site are presented along with the load-displacement curves for both the initial and repeat teats and a discussion of the analysis of the results. Repeat load tests showed an increase in capacity from the initial testing, however the percent increase was not the same for all depths. The results demonstrate that considerable shaft resistance can be developed in clays from the grouted shafts as might be expected. Depending on the L/D ratio of the shaft and the contribution of the lead helical section, at working loads the shaft capacity can dominate the behavior.

Jan 1, 2011

Ground support audits are sometimes necessary in ageing underground mines. Usually, the purpose of such audits is to assess the state of the ground support in various parts of the mine, identify areas that require attention and establish rehabilitation requirements. In 2005, Brunswick Mine, located in Bathurst, New Brunswick, Canada, completed a comprehensive mine-wide ground support audit. The areas examined included excavations in several mining blocks, as well as ramps, shaft stations, garages, shops, etc., throughout the mine. A vast amount of data was collected over a period of two weeks by multiple auditing teams. The audit was followed by a data digitisation exercise, and the creation of a data management system to store audit results and keep track of subsequent rehabilitation activities as they occur. One aspect of the data management system was the incorporation of a function for reporting on ground rehabilitation progress, along with the capability of updating mine level plans for easy visual presentation of this progress. This article describes the approach implemented at the mine to carry-out the audit, as well as the database constructed to manage the results.

May 1, 2009

By K. Goshtasbi

In this paper a genetic algorithm is used in a heavily jointed rock mass in order to investigate the critical circular slip surface and modification of slope surface. This method was applied to the southern wall of the 6th Golbini Jajarm bauxite mine. The mine is the largest bauxite deposit in Iran, located to the northeast of the town of Jajarm in the Khorasan province. Estimated reserve of bauxite in this deposit is about 160 million tonnes. Field and laboratory investigations were conducted in order to determine rock mass behaviour. A genetic algorithm code that uses the Simplified Bishop method as an objective function was developed for findingt he safety factor of circular slip surfaces. Sensitivity analysis was applied to determine the optimum values of the genetic algorithm variables, such as population size, selection method, crossover and mutation rates. After finding the critical circular slip surface, slope modification is carried out by removing unstable sections from marked critical slip surfaces, and this process is repeated until the last unsafe section is removed. Based on this code, modification occurred during 7 steps, by reaching a safety factor of 1.3 in the last step. Finally, the modified slope angle of the southern wall of the 6th Golbini Jajarm bauxite mine was determined to be 48.44 degrees. Keywords: Genetic algorithm, slope modification, circular slips surface, 6th Golbini Jajarm bauxite mine .

Jan 1, 2008

THERE are certain facts that the mining industry in Australia is faced with at the present moment which may be accepted as axioms. The industry is at a low ebb, as evidenced by statistics. Metals form the basis of all modern industries, and are necessaryfor the welfare of Australia. Mining is a wasting asset. Every ton of ore extracted is one ton less which c.annot be made good, and it should be our duty to get as much profit froin that ore as possible, otherwise there is a permanent loss to the country.The metal market cannot be controlled by Australia; it is more or less an international matter. Australia has not been thoroughly prospected. There are no mines being developed that are likely to replace those which are being depleted.Our mining engineers are as capable as those in other parts of the world, and have made good where they have been given a chance. There is no one cause for the present depression; there are several, more or less, interwoven. Of course, the war has had an adverse effect, but that has only dislocated things temporarily; it upset our markets, influenced the price of metals, and affected the labour market and cost of stores. Labour troubles made their appearance before the wave of unrest swept over the world. The cause of labour discontent must be investigated, and if possible removed. As each industry has .its·own problems, miners must inquire into their special problems, as there is no sovereign remedy that will suit all cases.It is obvious that we cannot mine ore if we do not know where it is; therefore, the first thing is to discover workable deposits.

Jan 1, 1919

By Y. Rama Murthy

Around 90% of the chromite resources of India are concentrated in the Boula-Nuasahi Sukinda belt of Orissa state. In order to conserve these valuable ore resources strategically, several companies established chrome ore beneficiation plants in this region. The general beneficiation process in these plants consists of gravity unit operations such as Floatex density separator, spiral, wet shaking table etc. Most of these gravity circuits suffer huge losses of valuable minerals in the tailing. Any attempt towards decreasing these losses would not only increase the limited reserves in India but also make the economics of the operations more attractive. Apart from the liberation phenomena, in many of the operating plants considerable quantity of values are lost in the tailings, due to inconsistent feed quality, inappropriate selection of operating and design parameters. Mineral engineers in this regard have to play a proactive and continuous role to improve the performance of all separating units by modifying even small changes based on tests conducted in laboratory under controlled conditions followed by attempts to make necessary changes in the plant. For such improvements, accurate data collection and proper data interpretation followed by making necessary change which is implementable in an operating plant play a very critical role in performance of the circuit. Databank collected over a period of time under various conditions would also help in overcoming the future problems related to either variation in the feed characteristics or specific demand by metallurgical industries. The above concept was adopted in one of the operating chromite beneficiation plant at Sukinda. The approach adopted and practical problems encountered during the study were reported in this paper. The result of trial campaign has shown that, an overall product assaying 30.2% Cr2O3 from the feed (18% Cr2O3 ) can be produced to in single stage. The final discards of the process contain 12% Cr2O3. Keywords: chromite, chromite beneficiation, chromite losses, gravity concentration techniques, plant operating data bank

Sep 1, 2012

By J. C. Allen, E. V. Herring

CHILE EXPLORATION CO's. oxide plant at Chuquicamata, the largest of its kind, started in 1915 with initial operations at the rate of 10,000 tons of ore per day. Anaconda Copper Mining Co. acquired the controlling interest in 1923 and in the next few years modernized the plant and mine, extending operations to a nominal capacity of 490 million lb of electrolytic copper yearly by 1942. Plant production averaging 495.7 million lb of copper per year was maintained for the eight-year period extending from 1941 to 1948 inclusive. During the World War II production reached its highest level when in 1944 the output was 531.8 million lb. The maximum production for any one month was 49.6 million lb, achieved in May 1947. E. A. Cappelen Smith, consulting metallurgist for M. Guggenheim's Sons, worked out the first process for the treatment of Chuquicamata copper oxide ore about 1913, and directed a staff of 20 young engineers operating a pilot plant at Perth Amboy, N. J., on three shifts for an entire year. The copper is extracted from the oxide ore by a hydro-metallurgical treatment described in detail by T. A. Campbell in AIME Transactions, Vol. 106, Copper Metallurgy, 1933. The Oxide Plant is divided into five main operations as follows: (1) Crushing, (2) Leaching, including dechloridizing and sulphur dioxide treatment, (3) Tailing disposal, (4) Electrolytic precipitation, (5) Smelting and melting. Crushing The present Primary Crushing Plant has been in operation 25 years, during which time 4,342,112 cars of 70 tons net capacity have passed through the dumpers. The ore as received from the mine is frequently blocky and up to 5 feet in section. It is reduced to 9-in. size by two 60-in. gyratory crushers, and transported to the east and west ore bins by 60-in. conveyors. In the secondary crushing operation the ore is first reduced to 2 to 3-in. size by five standard 7-ft cone crushers and two No. 10 gyratories. This product is then reduced to 3/8-in. size by fifty-two 48-in. vertical Symons disc crushers and is transported by belt conveyors to the loading bridges from which it is charged° into the leaching vats. Conveyor belt No. 14 which serves the eight vats in the east section of the leaching plant has transported over 125 million tons of ore, which is a record for any type of conveyor. This 60-in. belt travels at a speed of 600 fpm and carries loads up to 5500 tons per hr. Leaching The ore is leached in 14 vats, averaging 13,500 short tons net capacity each. These vats are lined with a natural mastic which adequately resists the sulphuric acid leaching solutions. The leaching process as presently conducted comprises soaking the ore with successive volumes of leaching solution and spent electrolyte and withdrawing successive volumes of enriched solution from the vat to a total of approximately 3.2 million gal. The first 1.6 million gal of this volume withdrawn is called strong solution and contains about 35 parts of copper per 1000. The balance of 1.6 million gal subsequently withdrawn is stored in a

Jan 1, 1952

By Lewis A. Martin

Researchers from the Spokane Research Laboratory, National Institute for Occupational Safety and Health, in cooperation with engineers from the Department of Mining and Geological Engineering, Montana Tech, Butte, MT, conducted tests to evaluate the tensile strength, fiber count, and adhesion of shotcrete applied to panels at the Chief Joseph Mine, a research and training facility operated by Montana Tech. The tests were conducted in the mine ramp 45 m (150 ft) inward from the access portal at a 15.25-m- (50-ft) long test area divided into five 3-m- (10-ft) long sections. The shotcrete was applied with an Aliva 240.5 machine fitted with a predampener. Different amounts of fiber were entrained for each panel. Background data for the tests were obtained from earlier tests in Nevada, where the typical amount of fiber in the shotcrete is 6.54 kg/m3 (11 lb/yd3). All shotcrete was applied to a minimum thickness of 76 mm (3 in). Cylindrical cores were drilled at the wall-rock interface, and adhesion was tested after 28 days of curing. The goal of this research is to reduce the need to install multiple supports at the advancing face by creating a safer mining system that limits the time miners are exposed to unprotected roof.

Jan 1, 2004