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By M. J. Sanzotti

This paper examines the potential for controlling longwall-induced subsidence by pneumatically backstowing the void created by mining with waste rock, and having the process scheduled as a unit operation of the mining activity. Based on a review of background literature, interviews with representatives of various mining companies, public-interest groups, and state and federal regulatory agencies, a hypothetical case-study evaluation of pneumatic stowing in a southwestern Pennsylvania mine site was conducted. The study indicated that current stowing technology cannot keep pace with the production potential of U.S. longwall systems. Further, at the case-study mine site, concomitant stowing would reduce subsidence by only 50% of that incurred during full longwall caving, the longwall coal production rate would decrease from 4000 tons per shift in the non-stowing case to 1500 tons in the stowing case, and a preliminary cost analysis reveals that pneumatic stowing would add $5.25 to $10.50 to the operating cost of producing a ton of coal at the case-study site.

Jan 1, 1995

By X. Song, Q. Zhang

"The development of fracture zones in surrounding rock mass has significant impact on the stability of underground mine roadways. Detection of the fracture zones is of compelling importance for maintaining roadway stability as well as for safe and speedy excavation of the roadways. This paper presents a study conducted at Dong Bao Wei underground coal mine, where the roadways were developed in diabase rock mass. The roadways suffered severe damages, including sloughing and excessive floor heaving. The borehole imaging technique was applied in the study to observe and detect fracture zone development surrounding the roadway openings. Based on the borehole imaging studies, new roadway support systems were proposed to improve the stability. INTRODUCTION At the Dong Bao Wei Coal Mine three main roadways of the west wing were excavated. The three roadways had semicircle arch cross sections and were at a depth of 650 meters, each being about 750 meters in length. The roadways were driven through a section of thick diabase intrusion, which was softened by water with reduced strength and may turn into powder form under weathering. Site investigation indicated that the roadways in diabase intrusion zone were badly damaged due to severe deformation, and very serious roadway sidewall sloughing and spalling accompanied by severe floor heave often occurred.(Figures 1 and 2) In order to ensure the normal use of the roadway, undercuts were excavated. However, this operation seriously affected the roadway construction progress and increased the amount of roadway support operations as well as the roadway maintenance costs. Furthermore, a roof fall accident occurred in nearby drilling site. The investigation indicated insufficient support provided for the roadways which imposed significant safety hazards and would have serious impact to mining production and subsequent mining activities.The support of the main roadways is a critical task and is the focus of the underground opening excavation work at the mine, since more than 40 years of service life is required from these main roadways. For these roadways, large cross sections with high degree of stability and minimal amount of deformation should be maintained. Therefore, providing sufficient and appropriate roadway supports is of significant importance to the coal mine. In this paper, in order to optimize the roadway supporting system, studies were carried out on the geological structures, lithological characters, roof bolt anchoring features and suitable anchoring layers. The studies were aimed at ensuring the stability of mine roadways, reducing the roadway maintenance costs and providing a safe mine passageway for orderly production and progressive development of the mine"

Jan 1, 2016

By Sadatoshi Ohmori, Simin Zhai, Devini Abeyawardena

A road tunnel is planned to be constructed in soft, high overburden ground of around 600 m in Japan by using the center drift advancing method. The dodging effect and early ring closure of the center drift were expected to reduce the displacement and deformation of tunnel and promote safe construction. The measurement result during construction was analyzed and those effects, which the displacement and deformation after the widening excavation decreased and its effect increased as the center drift radius increased, were confirmed by numerical analysis. Also, the effect of the early closure of center drift after widening excavation did not have much effect.

Jun 23, 2024

By W. E. Sabina

In the short period of one mans? career we have seen specifications for bulk material handling systems and equipment grow from two or three pages to as much as two or three volumes for a single contract. The old 'short form' described what the purchaser expected the equipment to do. The long form does the same but also includes nut, bolt, and lockwasher depth of detail. What are the events that led to this proliferation of verbiage, and does it benefit the buyer in the final analysis? Is there a better way to purchase complex equipment while ensuring the highest quality for the dollar spent?

Jan 1, 1986

By B. R. Green, Ms. M. H. Kotze

Ion-exchange fibres (IEF) were prepared by the ir­radiation grafting of styrene onto polypropylene, which was then subsequently functionalized. Strong- and weak-base exchangers were prepared and evaluated Tor their ability to extract gold cyanide selectively. The IEF prepared had loading capacities similar to those of the corresponding resins and they had good selectivities for gold cyanide when contacted with a mixed metal-cyanide solution. The expected advantage of IEF over granular exchangers, that of faster kinetics, was illustrated. The strong-base Iibre in particular seemed to be very effective for the extraction of gold cyanide from dilute solutions such as return-dam waters.

Jan 1, 1990

By Ernest L. Bradley

A positive pressure ventilation system, augmented by a dewatering well curtain and underground longhole drilling, provides effective ventilation and radon control at EXXON Minerals Company's Highland Underground Mine in the Southern Powder River Basin of Wyoming. Testing different types of bulkheads, sealants, and bleeder systems has led to improvements in the basic ventilation system. Continued testing of new or different materials and equipment is expected to lead to further improvement in the ventilation program. Effective training of both miners and supervisors is essential to maintaining and improving ventilation techniques. This paper addresses the ongoing ventilation program and experience to date at the Highland Uranium Mine.

Jan 1, 1979

By B. Hagemeyer

The trend to higher solids paper coating and to neutral/alkaline papermaking is causing an above average growth in the use of calcium carbonate as both a paper coating and a paper filling pigment. These developments are expected to continue well into the 1990s. Thus, calcium carbonate will account for a somewhat larger percentage of total paper pigment volume. Nevertheless, overall growth in paper tonnage coupled with an increase in filler pigment percentages will create a demand for larger quantities of other pigments as well. Kaolin will continue to be the dominant paper pigment by far, with continued growth though at a somewhat slower rate than calcium carbonate.

Jan 1, 1986

By H. Kempton

New methods for remediating metals-contaminated groundwater include in-situ emplacement of highly adsorptive substrates to permanently retard solutes. Substrates are introduced by sequential injection of soluble components that precipitate in the aquifer, forming a permanent high-retardation zone. This method overcomes the factors that limit pump-and-treat remediation; i.e, long-term source loading and slow desorption. Column tests demonstrated efficient substrate emplacement, increasing retardation coefficients of Cr(VI) by 20 and As(V) by 40. Similar effectiveness is expected for other heavy metals. Simulations using a coupled advective-geochemical model accurately matched substrate emplacement and arsenic attenuation, allowing extrapolation to other constituents and larger-scale applications.

Jan 1, 1999

By C. Sun

The Leeville underground mine has been in operation since 2006 and currently produces 2,903 t (3,200 st) of ore per day, with an average gold grade of 0.4 opt. The mine’s horizontal extent is large, 762 by 152 m (2,500 by 500 ft), while its vertical extent is 6 to 61 m (20 to 200 ft). A high density of joints occurs within the host rock. Based on rock mass rating and field observation, the ground conditions at Leeville can be characterized as poor to very poor. As such, heavy ground support is required for its mining operation. Ore zones with a height in excess of 10 m (35 ft) are considered for longhole stoping. A typical stope measures 6 m (20 ft) wide, 30 to 55 m (100 to 180 ft) long, depending on the ground conditions, and 10 to 30 m (35 to 100 ft) high, depending the thickness of the ore body, yielding 9,100 to 18,000 t (10,000 to 20,000 st) when completed. Narrow ore zones, less than 10 m (35 ft), are mined using cut and fill. Drifts at the Leeville Mine are 4.6 m (15 ft) wide by 4.6 m (15 ft) high. Because of poor ground conditions at this mine, the establishment of a ground control monitoring system is key to operating both safely and successfully. This monitoring system is composed of comprehensive instrument design and installation. Instruments include multi-point borehole extensometers (MPBX) and “stretch measurement to assess reinforcement tension” (SMART) cables. The monitoring system covers the mining zones and infrastructure openings. After about two years’ application and measurement, useful data has been collected and continues to be collected; this information will be used to design future stopes and infrastructure. The system makes engineering and operation teams able to do their job with more confidence and efficiency.

Jan 1, 2009

By J. C. Willett, J. R. Sanfilipo, S. M. Podwysocki, P. D. Warwick

The U.S. Geological Survey is concluding an assessment of the major coal regions of the country. In this program, the quantity and quality of coals that are expected to be mined during the next 30 years are characterized. For the Gulf Coast region, the evaluation includes reviews of the stratigraphic setting, coal resources, and the quality of the Cretaceous to Eocene coals in four coal-producing areas. The coal-bed methane potential for these areas will also be evaluated. The results of these efforts will be a series of digital maps, text, and tables that will be published in a CD-ROM format.

Jan 1, 2000

By A. P. Chaves, A. Gomes

The cyanidation and adsorption processes at Fazenda Brasileiro mine were studied with the aim of increasing hydrometallurgical recovery. Technical evaluation of the processes consisted of (i) quantitative mineralogy of ore samples collected in different points of the circuit, and (ii) comparison of plant performance in the original (designed CIP) and in the modified (current CIP/CIL) circuits. An empirical correlation between process variables and gold grades in the cyanidation tailings was established. The suggested modifications in the circuit and in the operation conditions led to an increase in gold recovery, from 91 to 93.5%. Annual revenue is expected to show an increase of approximately US$ 1 million.

Jan 1, 1998

By S. Acar, P. Somasundaran

Results of selective flocculation of natural ores containing two or more minerals and of synthetic mineral mixtures do not usually agree with what is expected on the basis of the results from single mineral tests (Acar and Somasundaran, 1985). This is mainly due to the ionic species released by the minerals, which act differently under different pH values. The objective of this investigation was to study 1) the surface chemical composition of selected sulfide minerals-natural chalcopyrite and pentlandite and synthetic covellite, millerite, and pyrrhotite-and 2) the changes brought about by the dissolved mineral species. Electron Spectroscopy for Chemical Analysis (ESCA) was used to perform the surface analyses.

Jan 1, 1991

By Daniel W. Kappes

This paper examines the issue of heap leach cash flow based on some recent operational examples. After the first six months of operation, single-lift continuous heaps produce into salable bullion only 70% of the total recoverable gold stacked. This compares with "batch" heaps and lab columns which achieve 100% in two to three months. Multiple-lift heaps often experience a second cash flow depression as a result of the holdup of gold in the heap. Heap leach projects seldom fail based Oil technical pe1for111ance, but they often fail in the sense that they gmerate cash flow at a much slower rate than expected.

Jan 1, 2000

By Steven W. Hunt, Jane A. Kettler, Barry R. Doyle

A sewer tunnel being constructed through an urban commercial area was to pass the site of a former gasoline service station. The site was known to have contained leaking underground storage tanks. An environmental assessment of soils on the alignment was performed, and measures were implemented to handle expected contaminants. Despite these precautions, an explosion occurred in the heading when liquid gasoline was encountered. Four workers were injured. This paper presents the findings of an investigation into the cause of the explosion, and examines how concerted efforts by the parties involved failed to prevent it. The level of guidance provided by OSHA Code provisions for tunneling in gassy conditions is discussed.

Jan 1, 1997

By R. Milici

Current federal and State coal assessments estimate resources in the ground, resources available for mining, and economically recoverable resources. None of these assessments predict the amount of coal that may be produced from an assessed area in the near future (~20 years). Predictive assessments of coal production would be based on an understanding of the regional coal geology (coal systems), potential demand, and knowledge of the mining history of the region. The output of the predictive assessment would be a supply curve – a probability distribution of the amount of coal expected to be produced from current and new mines during the assessment period. I

Jan 1, 2004

By Lisa Shevenell

Three pits at the Getchell Mine contained water during a hiatus in mining activity (1968-1983). For this period, expected concentrations of As, C1, SO4 and TDS resulting solely 16om evaporative concentration were computed. Computed values are 1.6 to 2.3 times greater than those measured in local groundwaters. However, computed values fix As, SO4 and TDS are lower than measured values in the pit lakes. In some cases, the computed values are only 8% of the measured pit lake values, indicating a major control on water quality via water-rock interactions. In contrast, computed C1 values exceed measured pit lake concentrations.

Jan 1, 2000

By J. R. Johanson

In recent years the procedures for functionally designing bulk storage bins and hoppers have evolved from qualitative guess and try methods to a quantative method based on theory and tests of the bulk solid to be stored. This quantative method, developed and implemented by Dr.'s A. W. Jenike and J. R. Johanson as with any new design, must prove its effectiveness and validity in the actual operation of the finished equipment. How accurate are the theoretical predictions? Is it possible to extrapolate from bench size tests on a small ample of the bulk solid to the full scale bin design? Can the theoretical designs be economically translated into working hardware? In this paper the answers to these questions are discussed in light of actual bin operations.

Jan 1, 1968

By J. R. Sturgul

Computer simulation models of working mines can be of great benefit to the mining engineer. Such models have been used in mine planning (how many trucks/shovels to have, when to add new equipment, etc.), mine design (should a dispatch system be purchased, where is the optimum location for mine equipment, etc.). A simulation model can be thought of as a dynamic representation of the mine and can easily be changed to reflect a wide variety of different situation. Often a major problem for the engineer is how to present the results of the simulation study. Using PROOF(R) animation it is now possible to interface the results of the simulation and project them onto a computer screen in cartoon fashion.

Jan 1, 1993

By M. Jawed

Coking coal reserves in India are distributed geographically in Giridih, Raniganj, East Bokaro & Jharia Coalfields (J.C.F.). 97% of prime coking coal in JCF coming through underground mines is credited to Bord & Pillar mining systems inspite of the fact that it results in heavy mining losses. The cost of mining in B & P mines has been much higher due to various factors. In this paper, O.R. model has been discussed with case study for optimizing the cost of production in operational underground mines. Also, a computer algorithm has been discussed using a schematic flowchart, which provides the trend of mining-losses 'in different mining, systems with changing design parameters and finally selects, the optimum mining system for undeveloped seams based on economic appraisal criteria.

Jan 1, 1989

By Douglas J. Cork

Biohydrometallurgica1 processes in the areas of coal desulfurization (Hoffman, M.R., et al., 1981) and recovery of metals from metal sulfide ores (Lundgren, D.G. and Malouf E.E., 1983) are well known. In addition other areas of potential interest to the mining industries have been outlined (Spisak, J.F., 1979). For instance, scientists involved in this interdisciplinary field have endeavored to apply microorganisms to the problem of effluent sulfate disposal. This chapter assesses the feasibility of utilizing a particular two stage anaerobic microbial process to convert effluent sulfate to orthorhombic sulfur. Strong emphasis is given to the possibility of substituting this bioprocess for alternative gypsum synthesis and disposal methodologies commonly practiced by companies which emphasize sulfuric acid or ammonium sulfate leaching processes.

Jan 1, 1985