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By Thierry Bernard

Considering rock fragmentation by explosive as the ultimate goal in mines and quarries, vibrations are definitely one of the main drawbacks faced by the Industry. If we can accurately predict vibrations level and frequencies, taking into account the whole set of the involved parameters, this will bring a major benefit to each of us, in our daily production process optimization effort. The model presented in this paper answers to this need thanks to a "holistic" approach of the vibration mechanism. By holistic, we mean that we approach the vibration effect (wave propagation) as a whole, by understanding all of the mechanisms that contributes to the process and comprehending how they are connected.

Jan 1, 2009

By Marvin V. Damm, Lloyd C. Venburg, Dan Sokol

Analytical and computer models are used to evaluate information obtained from existing data and investigation programs so mine water control systems can be designed and developed. These models allow the geohydrologist to predict the amount of groundwater inflow and the impact of dewatering and stream diversion on the hydrologic regime, and to determine the schedule and equipment needed for mine dewatering. This article describes uses of the model and the essential components necessary to construct an effective and practical one. Hydrologic models are constructed to determine the extent that mining activities will affect the ground water and surface water hydrologic regime. These models range from basic analytical, mathematical models to the more sophisticated finite difference and finite element groundwater models. Many factors determine the degree of sophistication, including the mining stage, the complexity of the hydrologic regime, the mining process, and regulatory requirements. Model Uses The geohydrologist and engineer construct models so the entire ground and surface water handling and supply system can be integrated and optimized. These models can provide the following data: • Information for water balance studies-the entire hydrologic regime for the area, including precipitation, transpiration, evaporation, infiltration, runoff, and the effect of geologic features. • Data on seepage rates during mining. • Information to design the depressurization and dewatering system, including water well spacing, location of sumping systems, need for grout curtains, and possible horizontal drain and underdrain locations. • Data needed to schedule dewatering and mining operations. • Prediction of initial and long-term impacts of mining and dewatering, including local and areal drawdowns, effects on existing wells, and modifications to the surface-subsurface hydrologic regime. Potentiometric surface maps and hydrographs can be prepared from these data. • Prediction of the effect of discharge from the water control system on the surface hydrology and data input to design systems for water discharge, storage, recharge, or reinjection. The results of a computer study that illustrates the effect of dewatering and reinjection into an aquifer to confine the cone of depression are shown on the accompanying figure. • Information to forecast potentiometric surface recovery after mining ceases. The accompanying figure shows the pumping and reinjection rates in a program that is adequate to dewater a mine and permit the recovery of potentiometric levels to approximate premining levels after mining ceases. • Documentation and design information for monitoring systems to be installed during all mining phases. • Water quality predictions and geochemical changes, including the possibility of brackish or saline water intrusion because of extensive dewatering or depressurization operations. • Documentation and data for acquiring permits from regulatory agencies. Model Input Program For any model to be effective, detailed hydrologic and geologic data must be gathered from a review of existing information and from an investigative program. These data should cover entire model limits. Data updating, revising, and refining should occur as new information is received from the investigation and monitoring programs, and from the mining operation as it progresses through the pre-mining, mining, post-mining, and reclamation

Jan 8, 1982

By W. A. Koehler, W. L. Eaton, Reynold Q. Shotts, M. E. Hinkle, M. R. Geer, Ralph M. Hunter, H. F. Yancey, Andrew B. Crichton, E. Zimmerman, S. H. Ash

R. Maize and H. P. Greenwald presiding) E. T. POWELL*-I would like to ask either Mr. Ash or Mr. Eaton if they know of any place where the Mine Inspectors' for¬mula has been used that water has flowed from one colliery to the other. W. L. EATON (authors' reply)-We have made considerable study but we have not gotten around to very many of the barrier pillars. I would not say that any or all of them have been designed to the strict figures of this formula. Most of those ex¬amined will not hold back the water that they are supposed to hold back. E. T. POWELL-If the pillar remains ac¬cording to the Mine Inspectors' formula? W. L. EATON-We have not found very many where the provisions were followed. E. T. POWELL-Where the Mine Inspec¬tors' formula has been fully complied with, have there been failures or not? W. L. EATON-I cannot say. Most of these barrier pillars probably were designed in accordance with this formula, but most of them, if they were so designed, are not in that shape now because a large number of them will not hold back the water; they have been reinforced, and they are punc¬tured in various places. Holes have been driven through them to relieve the hydro¬static pressure to avoid a failure. They do not dare to have a failure. In many instances, the barrier is punc¬tured to avoid a failure. In order to mine their coal safely, many companies must pump water from mines that were aban¬doned many years ago. R. MAIZE-That is true, Mr. Eaton, but do you know of any case where a barrier pillar actually failed and flooded an ad¬joining mine when the pillar had been left in accordance with the Mine Inspectors formula?

Jan 1, 1948

The modern Golden Cross mine entered the production phase in January 1992. The project is designed to produce over 100 000 oz/yr of gold and over 300 000 oz/yr of silver during a mine life of eight years. An open pit and an underground mine are operated producing around 850 000 t/yr of ore, to feed a conventional carbon-in-leach processing plant. Golden Cross is owned in joint venture by Coeur Gold New Zealand Limited (80%) and Viking Mining Company Limited (20 %).   Since the start of production several major aspects of the design have altered. The underground mine began as a mechanised cut and fill operation. The cut and fill stoping progresses in 3.3 m flatback lifts with maximum stoping width of 6 m. Where the ore zone is wider than 6 m a post pillar cut and fill method is used. In 1993 a new bench mining plan was introduced between the 270 and 260 levels. Flatbacking continued in the footwall drives in anticipation of variability of the ore width and orientation. The development of levels below the main service 200 level has indicated a possibility of bulk mining the ore block rather than flatbacks. This could lower mining costs but also introduce higher dilution rates. Development is in the advanced stages for trialing this method.

Jan 1, 1994

By James A. Finch, Stéphanie Gélinas

"A colorimetric technique, originally developed for methyl iso butyl carbinol (MIBC) based on the Komarowsky reaction, has been extended to a wide range of common mineral flotation frothers. The procedure, which is briefly described, is shown suited to on-site determination in a series of industrial campaigns. Some frother observations are described, including: concentration evolution down a bank, distribution between pulp and froth phases, and a mass balance around a circuit. Minute amounts of frother in recycle water were also measured.The contribution of frother and alcohol by-products in the analysis was generally additive for plants using aliphatic alcohol type frothers and decoupled for systems using glycols. Typically, U250C (polyglycol) was used at higher concentration (>10 ppm) than MIBC (aliphatic alcohol) (<10 ppm) or F-150 (polyglycol) (<3ppm).The ability to monitor frother easily will help interpret gas dispersion behaviour and should permit further optimization of flotation cell hydrodynamics and chemistry. The capability to directly measure should help optimize the type, amount and location of frother addition, and to assess frother recycled with reclaim process water.INTRODUCTIONOwing to the lack of analytical methods, the task of determining frother concentration in plant flotation circuits is not routinely performed. Industrial sites seldom outsource analyses that are both costly and inconvenient, due to the necessity of shipping freeze-dried samples to remote testing facilities. A more direct colorimetric method has recently been demonstrated for the laboratory characterization of common industrial frothers (Gélinas and Finch, 2004). The approach, based on the Komarowsky reaction (Penniman et al., 1936; Coles et al., 1942; Duke, 1947), was previously described by Parkhomovski et al. (1976) for methyl iso butyl carbinol (MIBC). The reaction involves the interaction of the OH group of a higher alcohol, concentrated sulphuric acid, and salicylaldehyde, to yield coloured solutions with intensities that can be analyzed by UV-visible spectrophotometry."

Jan 1, 2007

By D. Turk, P. Lefebvre, J. Sargent, K. Major

"Stillwater Mining Company recovers platinum and palladium from their Nye Montana operations. Mining first commenced at Nye in 1987 at a milling rate of 455 t/d (500 stpd). The plant was expanded in 1995 with the replacement of the ball mill and the addition of flotation capacity to increase mill throughput to 1820 t/d (2000 stpd). The applications for platinum and palladium have increased in recent years particularly in the automotive industry and the supply of the metals has remained fairly constant with prices for both platinum and palladium increasing and remaining very stable. In 1997 Stillwater initiated the expansion of their operations to increase production of platinum and palladium. Projects were initiated to expand production at the Nye operations, increase smelter and refining capacities at the Columbus facilities and to develop the extension of the orebody at the East Boulder site. This paper will discuss the changes at the Nye concentrator which were completed to increase production from 1820 t/d (2000 stpd) to 2730 t/d (3000 stpd) and eliminate some of the process bottlenecks.IntroductionStillwater Mining Company is mining the only significant primary source of PGMs outside of South Africa. The J-M Reef is an extensive mineralized zone containing PGMs that has been traced over a strike length of about 43 km (27 miles) in the southwest region of Montana. Stillwater controls the entire PGM mineralized zone.Johns-Manville geologists discovered palladium and platinum in the early 1970’s. In 1979, a Manville subsidiary entered into a partnership with Chevron, USA to develop the project. In 1 987, operations at the Stillwater property near Nye, Montana commenced."

Jan 1, 2000

By Alan T. Nelson, Ronald D. Mariani

The Tilden concentrator was originally constructed in 1974 for the processing of low grade hematite. Flotation is a key concentrating process in the operation, and therefore flotation optimization has been a major concern since the plant startup. This paper will discuss some of the modifications made in the process to achieve optimization. The conversion that now enables the plant to process magnetite as well as hematite also will be discussed. INTRODUCTION The Tilden Mine, located in Ishpeming, Michigan, is managed by Cleveland-Cliffs Iron Company and is owned by Cleveland-Cliffs and two Canadian steel makers. It was constructed and started production in 1974 and expanded in 1979 for processing a low grade, fine-grained hematite iron formation for which there was previously no technology available. Several papers have been written describing the unique character of the concentrating operation. The hematite plant consists of 12 grinding and concentrating lines, which utilize two stages of autogenous grinding with crushing of an intermediate sized product. The ground product is deslimed in a highly dispersed alkaline environment to reject silica. Corn starch, the flocculant, has a high affinity for iron at the operating pH range of 10.5 to 11.0. The ore is upgraded from 35% to 45% iron in the desliming step. The deslime thickener underflow is the feed to flotation. Each flotation line consists of a bank of 10 rougher cells, followed by four scavenging banks incorporating 5, 4, 3, and 3 cells each. The Wemco flotation cells are each 14.1 cubic meters (500 cubic feet) in volume. A total of 12 flotation lines are available. [ ] A reverse flotation process is employed, using a straight-chain, 8 to 10 carbon primary ether amine silica collector. At the levels used in the circuit, the amine also serves as a frother. A final concentrate is produced in the rougher cells. The concentrates from the four scavenging steps are combined and recirculated to the feed end of the roughers, with the fourth scavenger froth being discarded as a final tailing. Upgrading to about 65% iron is achieved, with control of the circuit based on final concentrate silica grade. Starch is again used, this time as a depressant for iron. During the years of operation, several key areas of the flotation process have been targeted for optimization. The most significant improvements have been realized in the following areas: *Grade Control Automation *Control of Water System Chemistry *Flotation Spray Water This paper will focus on these areas, but other minor improvements also will be briefly discussed.

Jan 1, 1993

By C. M. G. Wortley, N. Randolph, I. Ralston, R. D. Beck

The ?AMIRA Metal Accounting Project? had its origin in a workshop held in Cape Town on 1 August 2001, with the title ?Challenges in Metal Accounting and Information Management?, which was organised by the Western Cape Branch of the South African Institute of Mining and Metallurgy. This workshop identified the lack of an accepted set of standard procedures for metallurgical accounting as an industry-wide problem. Discussions which followed this workshop led to the initiation of the AMIRA Project P754, ?Improving Metal Accounting?, in 2003. The primary objective of the project was to provide tools for improving the auditability and transparency of metal accounting from mine to product and to facilitate good corporate governance. The planned deliverables of the project were a series of research projects into aspects of metal balancing in different types of metallurgical operations, a Code of Practice on Metal Accounting, and a textbook on the subject which could serve as a guide for metal accounting practitioners and students studying the topic. An additional planned deliverable was the provision of a new variety of professional experts in metal accounting, through successful completion of the research projects. Researchers were engaged at the Universities of Cape Town, Queensland and Stellenbosch and the project was sponsored by five mining companies, including three of the largest global mining groups. Research Program Eight research projects were undertaken as part of the P754 project and these are described briefly here to indicate the scope of the project. University of Cape Town ?Development of a methodology for measurement network design for metallurgical accounting at Namakwa Sands?. This project was based on the Namakwa Sands Separation Plant, with a data rich environment, and involved the investigation of measurement network design through the use of heuristics and the analysis of complex processing circuits. An industry-wide survey of current practice to facilitate the development of an expert system for plant accounting measurements was carried out. ?Metallurgical accounting design at the Waterval UG-2 Concentrator?. The objective of this project is to develop a model for predicting metal recoveries from the different components of a blended ore feed to a plant. ?Optimal measurement network design for metallurgical accounting at Zincor?. This project provided a hydrometallurgical test case for the design and evaluation of a semi-automated optimal measurement network. University of Queensland ?Quantifying the relationship between mine and mill?. This project involved a case study at North Parkes Mine, in which copper and gold ore is tracked from the pit source to the product, as well as a stockpile modelling study. University of Stellenbosch

Jan 1, 2007

By Q Zhuo, P C. Pistorius, M N. Al-Harbi

A likely increasingly important pathway for future low-carbon ironmaking and steelmaking is the combination of gas-based direct reduction with electric furnace steelmaking (DRI-EAF route), or with electric smelting (DRI-ESF route). In the DRI-EAF route, the gangue that is present in the iron ore is fluxed and removed as slag in the melting (steelmaking) step. This is in contrast with integrated steelmaking, in which the gangue is removed as part of blast furnace ironmaking. For DRI-EAF steelmaking, the amount and composition of slag depend on the iron ore composition, flux additions and iron yield. Slag volume and composition affect phosphorus removal, foaming behaviour and the process energy requirements. In this work, heat data from a year of DRI-EAF production was analysed to test whether the expected relationship between slag volume and electricity consumption for EAF steelmaking was observed. The data include slag analyses (one sample per shift), and heatlevel information on all inputs, final steel temperature and dissolved oxygen concentration, electricity consumption, tapped steel mass and tap-to-tap time. In analysing the data, the slag volume was estimated from the assayed slag CaO concentration and CaO inputs to the EAF. The expected effect of slag volume on steelmaking energy consumption was calculated with a mass and energy balance, considering the heat of mixing of the slag. The calculated energy requirement of slag formation is in line with previous estimates reported in the literature.

Aug 21, 2024

By D. J. Pyra, J. Kudelko, Korzekwam W.

Polkowice region (Lower Silesia, Poland) is an area, where the copper mining activity started about 40 years ago and new technologies were applied. There are 3 underground mines, 3 processing plants, tailings pond (the biggest one in Europe), pipelines for flotation waste transport, railways. Although new technologies were applied during the copper ore exploitation, the environment in this area were polluted mostly by dust containing copper, lead, zinc and arsenic. Estimated values of heavy metals in polluted soils were compared to the natural contents of this metals. The geochemical background for Polkowice area was defined. The pollution zones occur around mining facilities. Copper ore exploitation and processing is planned for the next 20-40 years depending on market situation. After mines and other facilities closing the most important problem will be sustainable development of this area. To evaluate the scope of revitalization activities the analysis of recent soil environment condition will be necessary as well as forecasts for pollution migration. Geostatistic methods used also in mining will be very helpful for this task.

Jan 1, 2005

By Jun Xiao, Jianwen Yang, Yanhong Dong, Daixiong Chen

"MANGOTE Surface oxidizied mine is a gold-bearing deposit in Congo's Mai-Ndombe Province. In the past decades, the ore has been exploited in a crude way by local farmers, which directly causes the severe processing difficulty and lack of economy of cyanide leaching. Hunan Research Institute for Non-ferrous metals (HRIM) is currently investigating options to recover gold through understanding the mineralogical characteristics of MANGOTE surface oxidized ore. Chemical analysis , X-ray diffraction(XRD) and Quantitative Evaluation of Minerals by SCANing electron microscopy (QEMSCAN ) were conducted on samples from mine site. The bulk analysis results showed that gold separation of gold from gangue minerals was feasible after grinding the ore samples to 86.53% -74µm and adjusting the pulp specific weight at 100g/L, and gravity separation was conducted with using spiral chute after grading of fine particles. The research results highlight relationship between mineralogical characteristics of abandoned ore and economy of comprehensive utilization that might be directive experience to similar cases. INTRODUCTION The occurrence state of gold in natural gold minerals determines the basic recovery and recovery effect of gold(Komnitsas, C., & Pooley, F. D. 1989). The occurrence of gold in the ore refers to the form of gold in the ore.Generally the existing state of gold can be divided into four major categories according to the viewpoint of the dispersion system: independent minerals and gold, a coarse dispersed system;colloidal gold, a colloidal dispersion; solid solution gold, is atomic ion dispersion; adsorptive gold, according to the adsorbed particle is the micelle or ion, respectively is a colloidal dispersion or ion dispersion(Mao, S. D., & Yang, R. S. 2009; Liu, J. J. et al. 2007; Horisberger, M., & Rosset, J. 1977; Li, Y., & Audétat, A. 2013).With the increasing technology of comprehensive utilization of resources,varied plants can now process different gold ores with various occurrence states(Neesse, T. 2014; 7. Ogundare. et al.2014)."

Jan 1, 2018

By David W. Wisecarver

The U.S. Bureau of Mines, in cooperation with U.S. Borax and Chemical Corporation and the Kennecott Copper Corporation, has investigated the use of the microseismic method to evaluate the stability of large, open-pit slope walls. The method is based on the phenomenon that stressed rock normally emits subaudible rock noises, and the number of rock noises per unit time (noise rate) and the magnitude of the rock noises (amplitude) increase as the stresses in the rock approach the failure stress of the rock. Therefore, the detection and recording of those rock noises serve as a semiquantitative method of predicting the incipient failure of rock. This report briefly describes the three different types of microseismic apparatus, the procedures, and the results of microseismic investigations in the slope walls of the Boron Mine near Boron, California, and the Rimbley, Liberty, and Tripp-Veteran open-pit mines near Ely, Nevada. Microsesimic noise rates in stable inactive mining areas are between 0 and 10 noises/ hour; the rates in stable active mining areas are between 10 and 50 noises/hour; and the rate in unstable areas is as high as 2500 noises/ hour. High microseismic noise rates in the Liberty Pit correlate with the time of nearby earthquakes, indicating that the earthquakes affected the slope wall. The results provide evidence that the microseismic tech¬nique is applicable to large pit walls, and that the wide band, wide range microseismic equipment appears to be suitable for open-pit investigations.

Jan 1, 1969

By R. N. Gow

Acidic treatment of enargite (Cu3AsS4) dissolves both arsenic and copper from the mineral and then attempts to separate them in the leach solution. The reactivity of enargite was examined in acidic solutions, over the pH range 1-7, to determine a potential range for co-dissolution.. Enargite mineral samples from Butte, MT and Quirivilca, Peru were used as working electrodes in a cyclic voltammetry corrosion cell setup, which were then cycled multiple times over -1000 to 1000 mV. Surface reactions and transitions were characterized using in-situ Raman spectroscopy, which were then compared to updated predominance diagrams for the copper-arsenic-sulfur system from a previous study done under alkaline conditions. The region of co-dissolution is limited to > 600 mV vs. SHE and pH < 1 under the proposed diagram.

Feb 23, 2014

By C. D. Woodward

PrioR to 1902, the tramming of ore from the stopes to the shafts, in the Butte mines, was done by man or animal power, but the demand for greater tonnage and the need for more improved methods of tramming the ore resulted in the installation of the compressed-air locomotive in a few mines. Some of the objections to animal haulage were thus eliminated, but this locomotive was not generally adopted, because of a number of limiting features. It was superseded by the electric trolley locomotive. The early types of trolley locomotives were not satisfactory from the operators&apos; viewpoint, but they had many economic advantages and after a number of years, in which improvements were constantly made in the structural details, they became dependable, so that the use of animals for main haulage in the mines has now been practically abandoned. There are now operating in the Butte mines of the Anaconda Copper Mining Co., 185 trolley-type locomotives, each of which has replaced five animals. It cost approximately $50 per month to keep an animal, hence the economies that resulted fully justified the expenditure of electrifying the haulage systems. The haulage conditions in this company&apos;s mines possess many advantageous features that arc not always found in underground mine workings. The drifts and crosscuts are large, approximately 5 ft. (1.5 m.) wide by 71/2 ft. (2.3 m.) high, and have curves of no less than 18 ft. (5.5 m.) radius; and the roadbeds of the drifts and crosscuts have a uniform grade of 0.5 per cent. toward the shaft, or in favor of the loaded trips. In all of the mines, except two, the track gage is 18 in. (45.7 cm.): and all tracks in the main haulageways are laid with 25-lb. (11.3 kg.) rails. The stations at the shaft are large, well-lighted, clean, and cool. The average temperature of the stations, however, is about 75" F. (24" C.), while the average temperature in some of the drifts and crosscuts is 92" I?. (33.5" C.). As the orebodies lie at varying distances from the hoisting shafts,

Jan 1, 1923

By C. D. Woodward

PrioR to 1902, the tramming of ore from the stopes to the shafts, in the Butte mines, was done by man or animal power, but the demand for greater tonnage and the need for more improved methods of tramming the ore resulted in the installation of the compressed-air locomotive in a few mines. Some of the objections to animal haulage were thus eliminated, but this locomotive was not generally adopted, because of a number of limiting features. It was superseded by the electric trolley locomotive. The early types of trolley locomotives were not satisfactory from the operators&apos; viewpoint, but they had many economic advantages and after a number of years, in which improvements were constantly made in the structural details, they became dependable, so that the use of animals for main haulage in the mines has now been practically abandoned. There are now operating in the Butte mines of the Anaconda Copper Mining Co., 185 trolley-type locomotives, each of which has replaced five animals. It cost approximately $50 per month to keep an animal, hence the economies that resulted fully justified the expenditure of electrifying the haulage systems. The haulage conditions in this company&apos;s mines possess many advantageous features that arc not always found in underground mine workings. The drifts and crosscuts are large, approximately 5 ft. (1.5 m.) wide by 71/2 ft. (2.3 m.) high, and have curves of no less than 18 ft. (5.5 m.) radius; and the roadbeds of the drifts and crosscuts have a uniform grade of 0.5 per cent. toward the shaft, or in favor of the loaded trips. In all of the mines, except two, the track gage is 18 in. (45.7 cm.): and all tracks in the main haulageways are laid with 25-lb. (11.3 kg.) rails. The stations at the shaft are large, well-lighted, clean, and cool. The average temperature of the stations, however, is about 75" F. (24" C.), while the average temperature in some of the drifts and crosscuts is 92" I?. (33.5" C.). As the orebodies lie at varying distances from the hoisting shafts,

Jan 1, 1923

By Charles Stone, Hannes Lagger, Dru Desai

The design methodology of the planned Second Avenue Subway Project (SAS) led to development of the initial support design to estimate cost and quantities in the Preliminary Engineering (PE) stage. Careful selection of the cavern design rules that recognized the impact of rock quality, rock cover, excavation geometry, and excavation sequence helped to overcome the design challenges of large, shallow caverns for the initial ground support. In the course of the design verification process prescribed by the design methodology, the design team was continuously reviewing and updating the support quantities. The design procedure includes methods using different approaches of empirical, continuum, and discontinuum analyses, which are currently advanced in the Final Engineering (FE) stage. The paper is a continuation of the RETC 2005 “Trials and Tribulations” and focuses on the procedures that led to the changes in the initial support as a result of the ongoing design development.

Jan 1, 2007

By M. Mpofu, M. van Schoor, T. Kgarume, H. Grobler

The South African mining industry has committed to achieving a state of zero harm for its workforce, with a strong emphasis on worker health and safety. Among the major safety concerns are falls of ground, a leading cause of injuries and fatalities. Ground-penetrating radar, a non-destructive geophysical method, is recognised for its ability to image structures, fractures, and geological features within the rock mass. However, ground penetrating radar data is often acquired in local coordinates, posing challenges for visualisation in mine computer-aided design or three-dimensional visualisation software. This study explores the pivotal role of light detection and ranging data in transforming ground penetrating radar data from local survey coordinates to absolute mine coordinates. A comprehensive georeferencing methodology is presented, providing the stepwise progression from the initial georeferencing of ground penetrating radar data to the ultimate integration of ground penetrating radar and light detection and ranging datasets, resulting in the creation of a ground penetrating radar-light detection and ranging three-dimensional model. The proposed approach not only facilitates the integration of but also offers a practical means of visualising the integrated datasets within commonly used computer-aided design or three-dimensional visualisation software. An essential aspect of this integration is the adoption of non-proprietary data formats, specifically American Standard Code for Information Interchange text files, ensuring broader accessibility and compatibility. The potential for integrating diverse datasets to construct insightful models of the underground mining environment is illustrated. Integration of different datasets has the potential to offer a holistic understanding of the mining environment, providing essential information to decision-makers.

Jul 23, 2025

By C. S. Smith, Chih-Chung Wang

TURNBULL and his collaborators1,2 have developed the theory of homogeneous nucleation as applied, inter alia, to solidification of liquid metals. Vonnegut³ and Turnbull4 have shown that if a liquid metal is subdivided into small droplets a vast majority of them will undercool very considerably before solidification, generally to as low as about 0.8 of the freezing temperature on the absolute scale. The nuclei effective at small degrees of supercooling in bulk metal seem to be internal or surface heterogeneities, relatively small in number. If the metal is subdivided, those droplets that happen to contain such nuclei will solidify at a temperature not greatly below the true freezing point, but only a small part of the whole volume will be affected and the majority of the drops will under-cool to the much lower temperature at which homo- geneous nucleation occurs as a result of fluctuations. It occurred to one of the authors that an appropriate subdivision to give effective freedom from random nuclei is produced during the solidification of many alloys that contain a minor amount of a phase of low melting point, and that one might then expect marked undercooling of the distributed phase. Experimental: The alloys selected for initial study were copper with minor amounts of lead and bismuth, and aluminum with tin. In all these alloys, the major component freezes at a temperature not much below that of the pure metal, and there is little further change in constitution on cooling until the lower melting point constituent freezes in an almost pure state. Cooling curves were taken using the controlled heat flow method permitting approximate specific heats to be obtained. Chromel-alumel thermocouples were used, with the standard emf tables, since extreme precision was not needed. The crucible (3/4 in. id, 5/16 in. wall) was made of B & W K-20 insulating brick. It held about 10 cc of the alloy being investigated. The cooling rate was 2.5" to 2.9°C per min under a controlled temperature difference of 20°. Approximate specific heats were computed from the inverse rate curves together with data from a blank run and from a standard run with a copper cylinder of known heat capacity. The alloys for investigation were made from high-purity metals (99.99+pct) and cast into graphite molds. The castings were machined to fit the crucible and to provide a hole for the inner thermocouple. Cooling curves were taken after heating to a temperature about 50" above the melting point of the minor, lower melting-point, constituent. Results The lead phase in an alloy of copper with 5 pct lead did not undercool more than 3" below the melting point of lead (327°C) either as cast or after annealing to produce a new dispersion of the liquid phase. A copper-zinc-lead alloy with 23.75 pct zinc and 5 pct lead undercooled more but showed no thermal effect below 319°C. A cast alloy of copper with 5 pct bismuth undercooled to 249°C (M.P. bismuth 27l °C), but once solidification started it was completed at the same temperature. This was anticipated, since the bismuth forms a nearly continuous phase between the grains of copper, and a solid crystal nucleated anywhere would rapidly* con- sume the entire network of liquid, unless the physical continuity of the liquid were broken through volume changes, inadequate fluidity, or gas evolution. Similar arguments apply in the case of copper-lead alloys, where the lead-rich liquid forms a network along grain edges, though not grain faces. In both cases there would be a few isolated particles

Jan 1, 1951

By S K. Ray

Open fire in a mine gallery causes large-scale damage to property and sometimes precious lives. Such fires produce two distinct effects, the throttle effect and the buoyancy effect. These effects disturb the ventilation system of the mine. To understand the complex dynamic phenomenon of open fire and its effect on ventilation systems, a mine fire model gallery has been designed and constructed at Central Mining Research Institute, Dhanbad. Two sets of experiments at air velocities of 1 and 1.5 m/s were conducted in the gallery using coal samples from the Dobrana seam of the Raniganj coalfields. After about an hour of development of fully-fledged fire, heavy backlash, with smoke and fumes, was observed. At the time of backlash occurring the gallery was divided into two zones. In the region of the gallery from the base up to 1.4 m the airflow was normal, in the remaining upper portion the airflow was the reverse. Air quantity reduced substantially, while pressure dropped across the fire zone, the products of combustion (POC) and temperature increased during the period of the throttle effect. It has been revealed from these studies that with an increase in airflow, pressure drops across the fire zone, POC, temperature and reduction in airflow increases. This paper addresses the important design features of the gallery, the instrumentation system, the experimental procedure and assesses the effect of open fires on mine ventilation systems.

Jan 1, 2005

By S. J. Aresco, A. A. Orning

This paper presents a scheme for determination of precision for the various steps in coal sampling, sample preparation, and analysis. It also gives resulting data on 100 American coals from various coal fields covering all ranks from lignite to low-volatile bituminous. The variances of the various steps of the process are studied as a function of the coal preparation, the top size of coal as sampled, and the ash content. To understand the variables that control the overall precision of coal sampling, sample reduction and analysis, there is need for measurement of the variances due to successive steps of the process. The purpose of the present paper is to study these variances as a function of the coal preparation, the top size of the coal as sampled, and the ash content. The sampling data included are from 100 individual preparation plants from various coal fields in the United States and cover all ranks of coal from lignite to low-volatile bituminous; various types of preparation; deep, strip and auger mines; and, in many instances, mixtures from two or more coal beds or types of mines. The collection of data is continuing, but sufficient work has been done to draw some important conclusions. Since the work was done in conjunction with the Bureau of Mines sampling of coal, the time that could be spent at any one preparation plant was limited. This, in turn, limited the number of samples that could be taken for each coal. For this reason, the results from various plants were pooled in blocks. Two major blocking categories were "raw" and "washed!&apos; The raw coals had no preparation other than crushing and/or screening. The washed coals were prepared further by some combination of wet or dry mechanical cleaning. The categories were further divided ac-

Jan 1, 1965