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By Y. P. Chugh, J. Ma

Higher production, better safety standard, and potential for automation are some of the benefits of longwall mining. Today, longwall face advances at a faster rate exposing many diversified rock layers in a short period of time. It is now a serious challenge to cope with ground control problems such as roof falls, face and floor failure, and excessive shield loading as fast as possible to minimize production and monetary losses. In Illinois coal mines, the existence of weak floor strata blow the coal seam may pose additional problems related to floor heaving, shield base punching, and associated roof and face falls. In this study, the effects of weak floor on longwall ground control are analyzed using two-dimensional finite element models. A two-leg 635.6-ton (700-short-ton) yielding capacity shield is included in the models to evaluate the effects of different thickness and material properties of the weak floor. The study indicates that the thickness and material properties of weak floor have significant effects on shield loading, the distribution and intensity of front abutment stress, failure zones in the surrounding strata, roof-to-floor convergence, and floor punching by the shield base.

Jan 1, 2000

By David Shatwell

Recent epithermal gold discoveries in Chile and Bolivia provide increasing evidence of a belt of intermittent, epithermal, precious metal mineralization east of the main Andean porphyry copper belt. This relationship may be the result of an easterly decrease in the age of magmatism and erosional levels, in¬crease in depth above the underlying Benioff zone and consequent changes in magma chemistry, or some other unrecognized factor. Examples are: • The Choquelimpie gold-silver mine in Chile and numerous other epithermal prospects (such as La Riviera, Bolivia) in late Tertiary volcanics along the Chile-Bolivia border. These lie east of the belt that contains the Toquepala, Quellaveco and Cuajone porphyries in southern Peru and the Cerro Colorado, Copaquire and Quebrada Blanca porphyries in northern rhila

Jan 1, 1990

By B. M. Das

Several laboratory model test results for the determination of the ultimate uplift capacity of single and group metal piles embedded in near-saturated clay have been presented. Based on the uplift test results for single piles, the variation of the adhesion factor with the undrained shear strength of clay has been determined, and an empirical correlation for estimation of the adhesion factor in soft and medium clays has been presented. The group efficiency of piles under uplifting load depends on factors such as embedment ratio, undrained shear strength of clay, the number of piles in a group, and the center-to-center spacing of the piles.

Jan 1, 2010

By Charles L. Kimbell

On the basis of world production data alone, 1985 appears to have been a year in which the world's mineral industry took another step upward in its recovery from the very poor years of 1981, 1982, and early 1983. Despite a drop in the output of crude oil, which was the single most significant crude mineral product from the viewpoint of value, the estimated value of world crude mineral production advanced by 3.4% to about $1,054 billion constant 1983 dollars, with output increases logged for nearly two-thirds of the commodities and forms of commodities for which the U.S. Bureau of Mines calculates a total world output. However, the economic well-being of any industry or group of industries cannot be measured solely in terms of the volume and/or value of its production, and examination of statistics reflecting other aspects of mineral industry performance shows that 1985 was a less than ideal year in many respects. In the case of consumption of mineral commodities, although there were gains registered in diverse sectors such as iron and steel, aluminum, fertilizer materials, solid fuels, and gaseous fuels, there were also proportionally small but notable declines in use among the older major nonferrous metals (copper, lead, tin, and zinc) and in the all-important liquid fuels. In the case of international trade in mineral commodities, although comprehensive data for 1985 were not yet available, there were indications that the value may well have fallen below the estimated 1984 level of $632 billion, although the volume may have increased slightly. This, if true, would be chiefly the result of declining prices of mineral commodities, and indeed, price declines were noted for a number of significant materials in terms of current dollars, and even more would register declines if calculated on the basis of constant dollars, adjusting for inflation.

Jan 1, 1987

By J Howard

Following discovery in October 2004, commencement of development in February 2007 and first ore production in mid 2007, the Trident gold deposit, located in the Eastern Goldfields of Western Australia, has now been successfully mined for over three years. Three years of operational history has enabled the performance of the Trident underground mine to be reconciled against the mine plan and strategy proposed for the original feasibility study.The Trident deposit, initially based on two lode systems known as the Eastern Zone and Western Zone, has been continuously drilled, interpreted and re-interpreted over the period and as a result the addition of the Athena, Apollo and Artemis lode systems as well as numerous smaller scale lodes has been realised. The first three years has seen the Trident underground mine quickly move up to its 1 Mtpa design production rate. The mine plan and strategy used in the initial feasibility study and subsequently implemented, required sufficient flexibility to enable modification and optimisation to mine plans as ore zones were further defined. The ability to modify the mining plans has enabled Avoca to achieve its mining targets at Trident. With over 250 000 ounces gold produced to January 2010, the company is well positioned to achieve its ten year vision associated with the Higginsville Gold Project.This paper offers an account of operational experiences whilst providing comparison to assumptions and methodologies used in the original feasibility study. The paper is a sequel to a paper presented at the Tenth Underground Operators’ Conference held in Launceston, Tasmania titled Development Strategy of the Trident Underground Gold Mine.

Mar 21, 2011

By F. F. von Glehn

There is no doubt that simulated ventilation networks must be adequately verified before they can be extrapolated and used for predictive purposes. There are two general approaches as to how the verification can be established and these are summarised as follows; The first approach is to measure all individual branches with trailing hoses or barometers to get individual pressure drop and flow per branch and then calculate individual resistance factors for input into the software. The simulator is run, checking that the output makes general sense (check some sensitivities if possible). The network is now considered as verified. The pressure drop to be measured is relatively small and thus it is inherent that the measured set of individual K factors will be imprecise no matter how much care is taken in the measurements and the resultant simulations will inherit the same problem. In the second approach, the network is assembled using estimated (Atkinson) K factors (based on physical features of airway, past experience and catalogued typical K factors). Only the main primary flow rates are measured and hence the relative distribution of the primary ventilation in the main airways is determined (probably about 10 off primary air flow measurements). Main critical pressure differentials at main and booster fans and across critical doors are measured (probably about 6 off primary pressure differential measurements need to be made). The simulator is run and the computer model is used to iterate and select an updated suite of K factors so that the flow balances and pressure differentials are correctly simulated (typically only 2 or 3 iterations are all that is needed). The network is now considered as verified. The pressure differences to be measured will be substantial in absolute terms and can be measured with high precision. Also, because only primary flows are measured, these will generally be measured at higher air speed points and hence improved relative accuracy. This leads to more accurate simulation results. This paper examines the advantages and disadvantages of the two approaches. 1 Background

Jan 1, 2009

By M. Newton

Optimization and sensitivity analysis of mineable economic volumes have been standard practise for open pits for many years now, and more recently software has become available to apply techniques for delineating mineable reserves for underground mines. In general these techniques have been applied to a single resource model to quantify mineable tonnes and grade for underground mining. However by using multiple conditionally simulated models both the risk associated with the mining parameters and the risk associated with variations in grade, tonnes and profit can be quantified. Using suitable software the mine planner can then easily and quickly define and compare alternative designs to assess and improve the robustness of and the confidence in the final design.

Jan 1, 2007

Due to deposit shape and dimension, narrow vein makes reserve modeling, geological control, stope design, drill and blasting more challenging. It needs high standard quality control as errors can be created easily, which could cause significant amount of ore loss or dilution. From channel sampling, survey control, reserve modeling, drill hole design, blasting, communication with underground drillers to backfill, this paper illustrated every step and its quality control of a long hole stope mining. Compared to other narrow vein mining methods (cut and fill and shrinkage), long hole stoping means higher production, less labor, and significantly lower cost when deposit characteristics allowed.

Jan 1, 2012

By Fei Chen, Lesley J. Gaydos, Laurence M. Demers, Douglas C. Kuhn

The fibrogenic effects of silica in experimental animals and humans has been extensively studied (I 7, 20). However, the pathogenesis and molecular mechanisms underlying lung injury and fibrosis resulting from silica exposure remain to be elucidated. It is well-documented that silica can stimulate monocyte-macrophage lineage cells to produce cytokines and growth factors, including interleukin-I (IL- I) (20), tumor necrosis factor-ex (TNF-cx) (I 7), insulin-like growth factor-I (IGF-1) (4), and transforming growth factor-P (TGF-P) (24). Consequently, it has been suggested that the fibrogenic effect of silica may be mediated by cytokines in the fater stages of silicosis. During the early phase of interaction between silica and the pulmonary alveolar macrophage, several direct and indirect lines of evidence suggest that reactive oxygen intermediates (ROI) may play a pivotal role in silica- induced tissue damage (2I, 22). One of the most important components of and contributors to ROI is nitric oxide (NO) produced from L-arginine and molecular oxygen under the catalytic influence of NO synthase (NOS) (I 9). At present, at least three NOS genes have been cloned: a constitutive neuron NOS, a constitutive endothelial cell NOS and an inducible NOS (iNOS) (16). A number of factors have been shown to differentially induce iNOS gene expression in different cell lines including bacterial cell products and foreign antigens. During inflammation, NO is a double-edged sword in terms of the host immune defense mechanisms and the physiologic response to an inflammatory insult. The macrophage is one of the major cellular sources of NO. During the early phase of acute inflammation, NO produced from the macrophage appears to facilitate the clearance of pathogens and promotes a local relaxation effect on the microcirculation of vascular smooth muscle. When the production of NO is left unattenuated, especially under oxidative stress, direct cytotoxic effects of NO can emerge through the formation of peroxynitrite as a result of a reaction between NO and superoxide (2).

Jan 1, 1998

By K. Heindlhofer

Estimates of the "plasticity" of a metal are commonly deduced from three types of test—tensile, torsion and impact. The several results have been more or less at variance, though this disparity has attracted little notice, largely perhaps because they have been expressed in different terms. The discrepancy between the results of the three tests becomes obvious when each is made at a series of low temperatures, for the temperature range within which the "plasticity" of iron largely disappears proves to be very different in the three types of test. The rather abrupt disappearance of "plasticity" of iron within a narrow temperature range cannot be due to any physicochemical change (such as a precipitation) taking place in the material at that time, because the original plasticity is immediately regained when the temperature of the material is brought above the sensitive range. Accordingly this difference in behavior shows that the "plasticity" of a metal depends upon the mode of action of the stresses which produce the deformation, and therefore upon the method of test. Analysis of the stresses leads to the conclusion that the observed plasticity of a metal is determined by the relation between its resistance to rupture by separation and its resistance to shear (slip), on the one hand, and between the effective normal and shearing stresses on the other; and that the relation between the two resistances does not in general remain constant with change of temperature, and may somehow be altered to some extent by the previous treatment of the specimen. This suggests the view that the results of none of the usual mechanical tests are directly comparable even for a single metal tested at a series of temperatures, or for a series of metals at one temperature, because the proportion of the total resistance of the metal to the test contributed by the

Jan 1, 1935

By K. Heindlhofer

Estimates of the "plasticity" of a metal are commonly deduced from three types of test—tensile, torsion and impact. The several results have been more or less at variance, though this disparity has attracted little notice, largely perhaps because they have been expressed in different terms. The discrepancy between the results of the three tests becomes obvious when each is made at a series of low temperatures, for the temperature range within which the "plasticity" of iron largely disappears proves to be very different in the three types of test. The rather abrupt disappearance of "plasticity" of iron within a narrow temperature range cannot be due to any physicochemical change (such as a precipitation) taking place in the material at that time, because the original plasticity is immediately regained when the temperature of the material is brought above the sensitive range. Accordingly this difference in behavior shows that the "plasticity" of a metal depends upon the mode of action of the stresses which produce the deformation, and therefore upon the method of test. Analysis of the stresses leads to the conclusion that the observed plasticity of a metal is determined by the relation between its resistance to rupture by separation and its resistance to shear (slip), on the one hand, and between the effective normal and shearing stresses on the other; and that the relation between the two resistances does not in general remain constant with change of temperature, and may somehow be altered to some extent by the previous treatment of the specimen. This suggests the view that the results of none of the usual mechanical tests are directly comparable even for a single metal tested at a series of temperatures, or for a series of metals at one temperature, because the proportion of the total resistance of the metal to the test contributed by the

Jan 1, 1935

By Jeremiah Cohn, Rachel L. Bauer, Catherine E. Johnson

Water is frequently used in explosive applications to increase explosive performance and reduce air overpressure. Water tamping can enhance cutting abilities of shaped charges in demolition and increase impulse of kicking or breaching charges. In explosive disposal, water is used to suppress air overpressure and reduce noise. Despite its widespread use, the specific effect of water placement, whether in front of or behind the explosive, has not been studied. This work evaluates the directional effects of water placement on blast performance using 400-gram sheet explosive charges in five configurations: no water (control), rear-only water (tamped), front-only water (pushed), water on both sides (confined), and a thin front-and-rear water layer (low mass confined) to assess reduced mass effects. Water was sealed in plastic bags and held in position with custom 3D-printed cages to ensure consistent geometry and contact. A modified ballistic pendulum consisting of a hanging steel W-beam was used to evaluate impulse transfer, with high-speed video capturing swing velocity. Air overpressure was recorded using a seismograph microphone. Rear-only water (tamping) increased beam swing velocity by 69% over the control while confinement with water on both sides increased performance by 12% at a 2:1 water-to-explosive ratio and by 50% at 4:1, though it still underperformed the tamped-only configuration. Pushed water alone did not increase beam momentum and reduced tamping effectiveness by 19% when combined. Seismograph microphone data showed that pushed and low mass confined water configurations produced some of the highest air overpressure levels (up to 139.2 dB), while tamped and control charges produced lower levels (~134–136 dB), suggesting that pushed water may amplify, rather than mitigate, air shock transmission. These findings show that water placement has a strong directional influence on blast dynamics: water behind a charge enhances energy transfer to the target, while water in front provides limited or potentially counterproductive mitigation. This study advances understanding of water–explosive interactions and will lead to more effective charge designs for breaching, disposal, and demolition.

Jan 26, 2026

By Pedro Fuertes Velazco

El presente trabajo describe el desarrollo de la compañía minera de Caravelí (Arequipa) como mina modelo -en tanto genere alta productividad en las vetas, genere su propia tecnología, así como su responsabililidad con el ambiente y las comunidades involucradas.

Jul 31, 2003

By James A. Wasson

This report summarizes the results and conclusions reached by various investigators who have attempted to determine the extent to which hydraulic fracturing will affect the secondary recovery of crude oil by waterflooding. It also discusses the most advantageous use of this well-stimulation method in waterflood projects. A thorough search of the literature was made, and pertinent information was abstracted from appropriate reports. A carefully designed and controlled program of formation fracturing is an effective aid in waterflooding because it increases water-injection and oil- production rates. Generally, fracturing has resulted in little or no reduction in ultimate oil recovery, but under certain circumstances recovery has been substantially increased.

Jan 1, 1963

By Verya Nasri

The Silver Line Phase III Project is the final one mile underground segment of the new Bus Rapid Transit in downtown Boston. The project is expected to significantly reduce existing and anticipated traffic congestion. The twin one-lane tunnels and two station platforms will be built by NATM in Boston saturated soft clay, sand and till layers in proximity to several historical buildings, underpinning two existing cut and cover subway stations and several major utilities in densely built urban area. This paper presents the analysis and design of the NATM tunnels and stations detailing the excavation sequence and support system and various ground improvement and pre-support techniques used in the preliminary and final design of the project

By Mats Keisu, Bengt Niklasson

The Sofia project has increased the level of knowledge and technique within tunnelling, drifting and contour blasting.

Jan 1, 1992

By Juan Lucero

Como consecuencia de los factores externos e internos, las empresas mineras necesitan ser más eficaces a través de la implementación de nuevas tecnologías e informática. En este sentido, la compañía minera Milpo disminuye los costos de hardware para así generar un control de operaciones más minucioso, automatizado y oportuno. Los principales logros obtenidos son el control detallado de las operaciones, los sistemas operativos son la base para obtener los costos operativos, una mejor formulación y control presupuestal, control de servicios de terceros y el de los sistemas integrados.

Sep 13, 2001

By Gungor Tuncer, Ali Kahriman, Abdulkadir Karadogan, Umit Ozer, Kagan Ozdemir

In the condition that drilling and blasting technique is inevitable depending on the rock mass and material characteristics on mining activities, the fragmentation rate and particle size distribution of the muckpile after blasting has important influences on the performance of subsequent mining activities such as loading, hauling, crushing, grinding etc. and the total costs of that mine. Drilling and blasting is an important step in this process chain and it's results such as fragmentation, muckpile shape and looseness, dilution, damage and rock softening effect the efficiency of downstream processes. There is an increasing body of blasting research indicating significant impacts in these downstream processes.

Jan 1, 2007

By Mark X. Haley

Foundation design and construction in Boston has changed dramatically during the past 10 years. Prior to 1985, the primary foundation element in Boston, where deep foundations are required, was driven end-bearing piles. Since 1985, drilled or excavated high capacity foundation elements have been utilized more frequently. This paper will provide a historic perspective of their use and a summary of design parameters for elements installed and founded in the bedrock. TOPOGRAPHY Boston was founded in 1630 by the Massachusetts Bay Company of John Winthrop and his hearty band of Puritans. The settlement was chosen for: ? its safe harbor, ? abundant source of fresh water, and ? peninsula setting offering protection of the ocean on almost all sides with high ground for fortification. These three factors were a direct result of past geologic processes that created the Boston Basin by erosion of the soft bedrock underlying this area as compared to the harder granite rock to the north, west and south. As the glacial ice sheets melted and moved northward, various soil types were deposited. During ice sheet re-advancement the hills and islands of Boston took on their precolonial shapes. The Trimont, consisting of Beacon, Mt. Vernon and Pemberton Hill, rose to 150 ft above sea level with the smaller Copps and Fort Hill to the north and south.

Jan 1, 1994

By Don C. White

The Vulture mine near Wickenburg, Arizona was a major gold producer from 1863 to 1942, having yielded about 11t(12.1 st) Au and 8t (8.8st) Ag. Gold occurs as coarse native metal and electrum in quartz veins and also finely dis¬seminated within a quartz monzonite sill and its silicified wall rock. The sill is semi-conformable within a Proterozoic volcaniclastic-dominated sequence, all dipping north about 35°. Early mining focused on the vein-hosted gold, particularly in the immediate hanging wall and footwall of the sill. Later efforts included some open-pit mining of the outcropping sill and adjacent altered and mineralized rock. Two sets of post-mineral faults have complicated the orebody geometry. The sill is a 350 m (1148 ft) long apophysis from a quartz mozonite stock to the west of the mine area. The stock has been dated at 85 my and contains abundant lesser gold occurrences in its core and about its margins. The Proterozoic rocks are notably lean in precious metals except where altered in proximity to the Creataceous stock and sill. Circumstances dictate an interpretation of epigenetic mineralization related to the Laramide intrusion.

Jan 1, 1990