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By M. A. Trevits, M. R. Thibou, A. Ozment, A. C. Smith, J. B. Walsh

The Excel No. 3 Mine is a room-and-pillar mining operation owned by MC Mining, LLC, a subsidiary of Alliance Resource Partners, LP, which produces coal from the Pond Creek Coalbed in Pike County, Kentucky. Late on December 25, 2004, a fire was discovered near the bottom of the slope and, after an unsuccessful attempt to fight the fire underground, it was decided to address the fire remotely from the surface. The mine operator developed a plan to fight the fire that called for the installation of temporary seals at the slope and mine shafts to eliminate the inflow of oxygen. In addition, the plan called for drilling and completion of vertical boreholes into select areas of the mine workings to monitor the mine atmosphere and inject nitrogen gas and gas-enhanced foam. Over the next 9 days, nitrogen gas was injected almost continuously and gas-enhanced foam was injected periodically as deemed necessary. On January 7, 2005 it was determined that the fire was successfully suppressed. This paper presents a discussion of the fire-fighting approach and an analysis of the results of the application of gas-enhanced foam technology.

By C. A. Young

Cyanide is a fast-acting, highly toxic substance but, at the same time, is deemed essential for sustaining life as well as our standard of living. In this manuscript, the facts about cyanide are presented beginning with a brief history and definition and ending with a discussion on cyanide alternatives. Other topics include speciation, physical characteristics, toxicity, manufacturing, cyanogenics, cyanide cycle, separation, destruction, and markets including those outside the mining industry. Emphasis, of course, is placed on gold production by leaching and how it is influenced by ore type, mineral characteristics and economics as well as its advantages and disadvantages.

Jan 1, 2001

By B W. Riddol1s

The 1983 Energy Plan calls for an increase in North Island coal production from both underground and opencast sources from the 1982/1983 production of 843 000 tpa to approximately 3.4 Mtpa within the ten year period to March 1993. This increased production is scheduled to come from the following sources: Huntly West No 1 underground mine reaching full production of 1.26 Mtpa. Huntly East underground mine increasing production to 750 000 tpa. The proposed new Huntly West No 2 mine producing 100 000 tpa in its first year of operation û 1992. The proposed Ohinewai opencast producing 920 000 tpa for supply to the steelmaking plant at Glenbrook, replacing Weavers opencast which will be worked out in 1990. Rotowaro opencast producing at 220 000 tpa (currently being achieved). Two additional sources of supply which are not scheduled to begin production for at least ten years, and both of which have been designated for coal fired thermal power generation, are the Maramarua and Mokau coalfields. It was originally envisaged that development of both coalfields would be a combination of underground and opencast mines. The form of development is yet to be confirmed by detailed feasibility studies. The location of the Maramarua, Ohinewai (Waikare Coalfield) and Mokau deposits is shown on Figure 1. Worley Consultants Limited, in conjunction with their partners Rheinbraun Consulting GmbH (Germany) and Longworth McKenzie Pty Limited (Australia) have been involved with investigations and mining assessments for the Maramarua, Mokau and Ohinewai prospects. The Maramarua and Mokau studies form part of the New Zealand Coal Resources Survey programme of updating information to the Pre-Feasibility Mining Assessment level before proceeding to detailed feasibility studies. The Ohinewai study was commissioned directly by Mines Division to investigate the feasibility of mining coal by 1989 before reserves at Weavers opencast are depleted. This paper describes typical studies which are now being commissioned by Mines Division to investigate large-scale mining development and the effect geotechnical-conditions may have on coal recovery. The magnitude of these projects is reflected in the proposed outputs û up to2 Mtpa from individual mines û and the introduction of new continuous mining systems for both underground and opencast mines on a scale which has not previously been contemplated.

Jan 1, 1984

By A. Ebrahimabadi

Roadheaders are very versatile excavation machines used in tunnelling, mine development, and mine production for soft to medium strength rock formations. Performance prediction is an important factor for successful roadheader application and generally deals with machine selection, production rate and bit consumption. Among many different parameters, brittleness is also one of the material properties related to breakage characteristics and can be used as a cuttability parameter from a mechanical excavation point of view. The main objective of the research study is to contribute the brittleness of rock excavated to construct a new empirical equation for predicting the performance of roadheaders in different material and operational conditions. In this regard, a new performance prediction model for medium duty roadheaders based on a brittleness index (BI) is presented. In this study, rock mass brittleness index (RMBI) is defined in order to investigate the influence of BI on roadheader performance. RMBI is an index which can be used to relate the intact and rock mass characteristics to machine performance. Results demonstrated that RMBI is highly correlated to instantaneous cutting rate (ICR) (R²=0.94). Moreover, through the further analysis and normalization, the pick consumption index (PCI) was introduced as a parameter having a good relation with pick or bit consumption rates (PCR) (R²=0.79). Finally, the new predictive models for ICR and PCR showed very good correlations with the actual measured values. Keywords Performance prediction, roadheader, brittleness index, mechanical excavation.

Jan 1, 2011

Project cost control procedures and computer systems have enjoyed a successful and simple relationship over the past decade, thanks primarily to the proliferation of portable computers or PC's. Prior to the introduction of this technology, project control was largely a manual and somewhat onerous task of historical data compilations, with little time available for dynamic forecasting, staged planning, or pre-emptive cost control. Automated systems developed during this era were resident on "Heavy Iron" or mainframe computers and were expensive to maintain and operate. Use of these early systems was limited to large engineering, construction, and industrial concerns with the economies of scale and funding required for their successful application. Systems were either designed for critical path analysis or task scheduling, but rarely integrated with the other, much less cost control.

Jan 1, 1990

1. Paper1?Identification and enumeration of asbestos fibers in the mining environment: mission and modification to the federal asbestos standard Arthur M. Langer Asbestos-related disease is increased with cumulative exposure (the concentration of asbestos in the air and duration of exposure). The maximum duration is assumed to be a working lifetime so federal agencies control cumulative exposure by limiting the airborne concentration of asbestos fibers equal to or greater than 5 lm in length. Air samples are collected in the environment of interest by entraining the airborne particulates including fibers on membrane filters and then counting the number of fibers using phase-contrast light microscopy. In addition to length, the fibers must have a length to width ratio of at least 3 to 1. This ratio is also referred to as the aspect ratio. Some counting strategies placed an upper limit on the fiber width restricting the counting to respirable fibers. Airborne asbestos is controlled by monitoring a sub-population of the airborne asbestos. No asbestos fibers shorter than 5 lm or fibers of any length having widths less than the resolution of the light optical method are counted. In the non-occupational environment, the Environmental Protection Agency requires the use of analytical transmission electron microscopy and fibers and counting fibers with lengths of 0.5 lm or greater and aspect ratios of 5 to 1 or greater are counted. The permissible exposure limit for asbestos has been reduced by more than 120-fold since 1969, when the standard was 12 fiber/ml and the current monitoring methodology was developed. The manufacturing and mining worksites are regulated by two different federal agencies and the asbestos exposure limit was higher in the mining environment until recently (Mine Safety and Health Administration 30 CFR Part 56, 57, and 7, Federal Registry, February 29, 2008). Currently the permissible exposure limit (PEL) is the same in both types of workplace and it is 0.1 fibers per milliliter (fiber/ml) over an 8-h shift as a time-weighted average (TWA). A milliliter (ml) is equivalent to a cubic centimeter (cc) and sometimes this standard is reported as 0.1 f/cc. As the phase-contrast methodology was used to monitor lower exposures and environments, other fibrous mineral particulates were incorrectly characterized as asbestos. These occurred in talc deposits and taconite ores from the Eastern Mesabi Range.

Jan 1, 2008

By Y Xiao, C Lei, C Shu, W Wang, K Wang, J Deng

To investigate the effect on coal spontaneous combustion with high geo-temperature, an experimental apparatus was developed to measure characteristic parameters of two kinds of coal samples at different temperatures: one was 40°C (G coal sample) and the other was a rising temperature from room temperature (C coal sample). Based on the relationship between CO concentration and the temperature variation, a calculation model of the apparent activation energy of coal was established. The results indicated that the oxygen consumption rate, the generation rate of CO and CO2, and heat release intensity of G coal sample were higher than C coal sample. This trend was more and more obvious as the temperature increased. Furthermore, the apparent activation energy of G coal sample was lower than C coal sample, especially at low temperature stage, which demonstrated that the more the oxidation and exothermic reaction of G coal sample was enhanced, the less energy was required to break the barrier of oxidation reaction. Under the same condition, the speed of oxidation reaction was faster for the coal in the high geo-temperature environment, which was more liable to spontaneous combustion.CITATION:Lei, C, Deng, J, Xiao, Y, Shu, C, Wang, K and Wang, W, 2017. The effect of high geo-temperature environment on spontaneous combustion – an experimental study, in Proceedings Australian Mine Vent Conference 2017, pp 137–142 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

A subsurface study of the Maria Lode and associated hydrothermal alteration of andesites within the Karangahake epithermal gold-silver deposit defined the local evolutionary sequence in the once active geothermal system.   Some implications for mining of epithermal deposits arise as a result.

Jan 1, 1984

This paper highlights the agricultural sector's primary concerns with mining in New Zealand: the information gap, land rehabilitation and compensation. It suggests how these issues can be resolved between the competing land uses in the interests of New Zealand.

Jan 1, 1981

By C. W. Smith

The U.S. Bureau of Mines conducted research to determine the effect of ground water control on the dewatering of phosphatic clay wastes. Two storage impoundments were constructed. One impoundment was surrounded on three sides with a series of well points (shallow vertical wells) to lower the ambient water table and the second impoundment served as a control. Ground water was pumped from the area surrounding the test impoundment for a period of 490 days. A constant pumping rate of 60 gal/min resulted in a water table drawdown of 13 ft, approximating the bottom of the impoundment. At the end of the test period percent solids in the test impoundment was 35 pct, while in the control impoundment percent solids was only 26.8 pct. Percent solids of greater than 30 pct is required for capping and final reclamation using fertile overburden.

Jan 1, 1989

By I. H. Wong

The large diameter caisson foundations and their construction methods for three 50 to 60 storey high buildings in Singapore are described. The caissons are 5 m to 8 m in diameter and 40 m to 100 m deep, excavated either by hand or mechanised excavators or by drilling and blasting. Performance of the 50 storey DBS Building is described.

Jan 1, 2010

By H. Jalkanen, L. Holappa

The main role of slag in oxygen converter processes is to absorb the non-volatile oxidation products of hot metal impurities, Si, P, Mn, Ti, V, etc. The importance of converter slag as deP and de Smedia has ceased with implementation of special pre- and post-converter treatments. The transfer from top blowing (LD) to combined blowing converters has decreased the amount of slagged iron that, together with the tendency towards lower silicon and manganese contents, has decreased slag to steel ratio. Still the control of slag forming and behaviour during the blow is of great importance. In this paper the thermodynamics of the slag forming reactions, the role of slag in the modern oxygen converter process for impurity elimination, splashing, lining wear, dust formation and post combustion are discussed on the basis of common knowledge and experience of Finnish steel plants.

Jan 1, 2004

By G. Pantazopoulos, A. Vazdirvanidis

In this paper, a failure analysis investigation is presented concerning the intergranular cracking of three different diameter (Ø26.6, Ø10.8, Ø8.5 mm) high strength brass rods which failed after extrusion. Optical, Scanning Electron Microscopy and Electron Backscatter Diffraction are employed in order to reveal the mechanisms and the root causes of the failures. The microstructural characteristics, exhibited by the brass rods, pertaining mainly to phase, grain structure, size and distribution of intermetallic particles, are considered to exert a detrimental effect, impairing the mechanical properties, facilitating the environmentally-induced degradation and assisting the occurrence of brittle fractures. Revision of preheating and extrusion conditions could be further implemented in order to minimize the risk of such failure in the future.

Mar 1, 2018

By John L. Ellenberger, Gabriel S. Esterhuizen

Observations of pillar conditions in limestone mines showed that the presence of weak bands in the limestone can result in pillar damage at stresses that are lower than one would otherwise expect. The objective of this National Institute for Occupational Safety and Health study was to investigate the mechanism of failure caused by the presence of weak bands by using a series of numerical models based on realistic physical properties. The effect of the weak bands on pillar strength was also investigated by developing a series of pillar models with different width-to-height ratios and determining their strength by simulating a servo-controlled loading condition. The material properties of the bands and the limestone were varied and their effects on pillar strength were determined. Model results demonstrated failure development similar to the pillars observed in the field. The weak bands were seen to develop tensile stresses in the limestone as they extrude under increasing stress. The limestone fails in tension at a much lower stress than its expected uniaxial compressive strength. The results showed the load bearing capacity of the pillars can be reduced significantly by the presence of multiple thin weak bands. The degree of strength reduction is largely dependent on the compressive strength, the frictional resistance and the thickness of the weak bands. Single weak bands do not affect pillars as severely as multiple bands. However, the model results show that a single thick weak band, which comprises more than about 2 percent of the pillar height, can cause a significant reduction in pillar strength. The weakening effect of the bands become less severe as the pillar width-to-height ratio is increased. Field observation of spalling and failure associated with weak bands in limestone pillars show that the failure mechanism in the models resembles the observed failure. The model results provide insight into the important factors affecting pillar strength in the presence of weak banded materials.

By George H. Holmes

Beryllium deposits in the northern Virgin Mountains , Clark County , Nev . , and Mohave County , Ariz . , about 70 miles northeast of Las Vegas , were investigated by the Bureau of Mines . The investigation indicated a widespread occurrence of beryllium- bearing pegmatites within an extensive belt of mica - schist . Several deposits with significant beryllium mineral concentrations were encountered . Only a few of the samples analyzed contained more than 1 percent beryllium oxide ( BeO ) ; in many of the samples , no beryllium was reported . The average tenor of samples from the more important occurrences was 0.25 percent BeO . Chrysoberyl is the predominant beryllium mineral in the pegmatite sills ; beryl predominates in the more massive bodies . Minute quantities of cesium and lithium minerals also occur , but no columbium , tantalum , or other rare minerals were found . Ore dressing tests on a composite sample containing 0.28 percent BeO which was representative of the pegmatite sills , indicated an 85 percent recovery of the chrysoberyl ( 70 percent recovery of total BeO ) by gravity concentration in a concentrate containing 17.6 percent BeO .

Jan 1, 1964

By Mark K. Larson

A constitutive model for rock interfaces based on the principles of static fatigue is proposed. The model is applicable to weak rock or joints with cohesion. Friction and dilation are decreased as plastic work increases. At equilibrium, the creep time increases by one time-step interval, and interface cohesion at each node decreases according to a power function. A constant-load, direct-shear simulation showed that the model is cap- able of mimicking constant-rate and tertiary creep and predicting failure. Tests on core from a coal mine showed constant-rate and, sometimes, tertiary creep, but also weak transitory creep. The cohesion deterioration function may need modification to simulate primary-phase creep. If model parameters are known for a site, the model can predict the onset of tertiary creep and failure. Such predictions can help engineers make better entry design and support decisions, which will reduce the likelihood of roof falls and increase safety for underground miners.

By Wilson D, Kirkland J

Compressed air energy storage (CAES) uses low cost off-peak energy to compress air and pump it into pressurised underground storage. Expanding the air through a modified form of gas turbine generates electrical energy when required. While generating power, a CAES station consumes approximately one-third of the gas required for the equivalent installed capacity of a conventional gas turbine. Air can be stored in underground rock caverns, caverns in salt domes, or in aquifers. Existing CAES power stations use caverns mined out of salt domes. Aquifer storage for CAES has been proposed, but not yet implemented. The groundwater in the aquifer would be displaced during air injection and when required the air would be extracted using the natural hydro-static pressure. Victoria has no salt domes, but has aquifers onshore in the Gippsland Basin with geological dome structures of suitable depth, discovery pressure, porosity, permeability and caprock for CAES development. Field tests costing several million dollars would be required to prove the suitability. The most suitable aquifer is near Seaspray, where several dome structures exist. The aquifer, comprising of coarse sands capped by coal and mudstone, is some 600 metres deep with a hydrostatic pressure of 6.3 MPa. Computer simulation of injection and extraction of air from the aquifer under various combinations of horizontal and vertical wells, permeability and tubing head pressures indicated the largest aquifer structure had the capacity to sustain a 300 MW station. A well field comprising of 24 directionally driven wells with a horizontal exposure to the aquifer would achieve the air flow rates required. Using plant similar to that recently installed at McIntosh Alabama USA, would mean high capital costs compared to standard gas turbine plant. However, a review of modem gas turbines indicated that they could be easily and economically adaptated to CAES duty. Adapting a 120 MW gas turbine would give 344 MW output. A separate air compression plant would be used. Economic evaluations indicate that, for gas prices above $1.95 per GJ, a 344 MW CAES plant is more economic for intermediate/reserve load duty than simple cycle gas turbines.

Jan 1, 1992

By Wu Jie Mei, Li Yao Liang, Franz-Werner Gerressen, Arthur Bi

Diaphragm walls (D-walls) are known as underground structural elements commonly used for retention systems and permanent foundation elements. In addition, they are also quite often used as deep groundwater barriers, called Cut-Off-Walls (COW). Shanghai ranks third among the most densely populated metropolises in the world. In 1990, only eight million people lived there. Today, Shanghai has about25 million inhabitants. The increasing demand to accommodate the infrastructure of growing megacities like Shanghai pushes the required depth for subway, sewage and foundation projects to the limit. Future projects will demand excavation depths of more than 100 m (328 ft) on a regular basis. Already carried out reference projects will be described and a general outlook for upcoming projects will be given. The paper also explains the installation process in general focusing on the use of trench cutter technology. INTRODUCTION D- walls are known as underground structural elements, commonly used as retention systems for excavation pits and shafts as well as permanent foundation walls or elements. It is anticipated that, with the increasing trend of utilizing more and more underground space to accommodate environmental considerations and urban/suburban development, there will be an increasing requirement for diaphragm wall usage in even more difficult conditions and with increasing depth. The trench cutter is the most important tool for performing this work. The hydraulic grab, a well-known and valuable excavation tool for d-walls reaches its limits in terms of depth and when cutting rock. Therefore the trench cutter technology will be in the focus of this paper. The trench cutter itself is a reverse circulation excavation tool. It consists of a heavy steel frame with two drive gears attached to its bottom end, which rotates in opposite direction around the horizontal axis. Cutter wheels are mounted onto the drive gears. As they rotate, the soil beneath the cutter wheels is continuously broken up, removed, mixed with the bentonite slurry in the trench and moved towards the opening of the suction box of the pump? A centrifugal pump located right above the cutter wheels conveys the slurry via a hose system up to a desanding plant. There the slurry loaded with soil and rock particles is cleaned and returned into the trench.

Jan 1, 2018

By Barton K. Cross

The objectives of this effort were to: 1) Develop and validate start-of-shift operational inspection procedures to be used by operators of mobile, self-propelled equipment used in surface mining operations; 2) Evaluate user acceptance of the developed procedures; and 3) Recommend methods and media for presentation of the developed procedures to the user population. Mobile, self-propelled surface mine equipment requiring start-of-shift inspection was identified. Subsystems amenable to operational inspection were identified. The procedures addressing all safety critical subsystems on each equipment type were then developed and validated. The inspection procedures developed were those that could be performed largely from the operator's station. User acceptance was evaluated during on-site data collection visits to surface mines. Representatives of the user population reviewed the procedures and were then interviewed. Recommendations for the methods and media of presentation to the user population were developed from information obtained in: 1) Review and analysis of instructional technology literature applicable to this area; 2) On-site data collection; and 3) Analysis of the working environment and characteristics of the user population.

Jan 1, 1977

By H Aral

A rotating magnetic field can be produced in a magnetic separator by using a magnet rotor fitted with alternate north-south magnetic poles, similar to the rotors currently used in modern eddy current separators. Rotation of the magnetic field causes ferromagnetic particles to rotate during magnetic separation. The particle rotation can then be used simply to remove entrapment during a conventional attraction magnetic separation (RMF lift separation), or it can be used to roll particles away from non-rotating particles, and to move them out of the separator under their own rotation (RMF rotation separation). RMF (rotating magnetic field) separation is a separation for ferromagnetic particles. These particles have a very ordered magnetism that is locked into directions of easy magnetisation in the crystal. As a result, if the external field rotates, the particles attempt to rotate with it. RMF separation uses this fact to rotate the ferromagnetic particles in a rotating field. In contrast, paramagnetic particles have a magnetism that can point in any direction with almost equal ease, and these will not rotate in a rotating field. By making use of this difference in magnetic properties, RMF rotation separation can separate ferromagnetic particles from paramagnetic, even when the particles have similar susceptibilities. Some particles such as both chrome spinel and ilmenite can contain ferromagnetic regions within a paramagnetic matrix. These ferromagnetic regions can vary from very small regions dispersed throughout the crystal, through thin lamellae, to larger more bulky regions. Although most natural ilmenite is ferromagnetic and generally has a higher magnetic susceptibility than paramagnetic chrome spinel, the susceptibility ranges for the two minerals overlap considerably (Allen, 2000a) due to the presence of these ferromagnetic elements, frequently making the conventional magnetic separation of these two minerals impractical. It is known that roasting a mixture of ilmenite and chrome spinel particles increases the magnetic susceptibility of the ilmenite while leaving the spinel susceptibility substantially unchanged. This makes the use of conventional (susceptibility attraction) magnetic separation more practical for the separation of these two minerals. However, very little is known about the effects of roasting on the response of ilmenite and spinel particles to a rotating magnetic field. For example, although the optimal ilmenite roasting conditions for conventional magnetic separation are quite well established such conditions may or may not be optimal for RMF rotation separation. Low intensity conventional magnetic separation on the basis of magnetic susceptibility can be made more accurate if it is carried out in a rotating field, because the rapid spinning of the separating particles prevents the formation of magnetic flocs, and reduces entrapment and entrainment. Medium intensity RMF rotation-only separation (no attraction component) has the ability to separate rotating (ferromagnetic) from non-rotating (paramagnetic) particles, irrespective of their relative magnetic susceptibilities. RMF rotation separation is of particular interest in this case because ilmenite particles generally rotate much better than the mainly paramagnetic chrome spinel particles, and roasting could enhance this difference further. Further information on the use of RMF to separate minerals can be found in Allen (2000a; b and c). The aim of this series of tests on a number of Australian ilmenites was to compare some different oxidising and reducing roast methods and to establish whether the use of RMF rotation separation improves the chrome spinel rejection.

Jan 1, 2001