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By Werner Burger

Earth Pressure tunnel boring machines are tackling difficult ground conditions that five years previous were not considered feasible. The technology has evolved that allows EPB TBMs to cross into areas that with the latest in conditioning and special design considerations are now possible to mine. This paper will review the various recent developments and those projects where these new techniques have been applied.

Jan 1, 2008

By N. Loganathan, Tan Boon Tee, Joe O’Carroll, Richard Flanagan

In recent years, tunnelling activities in Singapore have increased considerably with the construction of extensions to the existing sub-surface transport system, a deep tunnel sewerage disposal system, and tunnels for the laying power cables and other utilities. These tunnels are excavated through urban areas, adjacent to high-rise buildings, depressed road structures, beneath other tunnels, and buried services. Earth pressure balance (EPB) tunnel boring machines (TBM) have been used extensively in Singapore with great success. The risk associated with soft ground tunnelling, including tunnelling through Old Alluvium, can be minimized with an understanding of the geology, geotechnical parameters, and the tunnelling-induced behaviour of Old Alluvium (OA The purpose of this paper is to present some design and construction aspects of EPB TBM tunnelling through Old Alluvium.

Jan 1, 2005

By Craig Bournes, David Chapman, Michael DiPonio

Historically, boulders are a frequent source of problems in soft ground tunneling. During tunnel construction, the need to manually break and remove boulders as obstructions causes delays to the project. Repairs to a tunnel boring machine (TBM) can also be a source of delays. Managing these problems is difficult since normal soil investigation techniques do not accurately predict the presence or frequency of boulders. This has lead to considerable number of claims for extra costs and delays during the construction of soft ground tunneling projects. These issues are exacerbated in pressurized face tunneling systems where there is limited access to the TBM cutterhead for obstruction removal and/or cutterhead maintenance. The project team that built the Big Walnut Augmentation/Rickenbacker Interceptor (BWARI) Project for the City of Columbus successfully managed the design and construction of a 4,267 mm (14 ft) diameter soft ground tunnel with high boulder concentrations in a complex geologic setting. The management of the boulder issue tookplace during several phases of the project.

Jan 1, 2007

By Laura McNally

In 2006 McNally International Inc. in a Joint Venture partnership with Aecon Constructors was the successful bidder on two York Region Tunnel Projects: Bathurst Collector/Langstaff Trunk Sewers; and YDSS Interceptor Sewer 19th Avenue Project. These projects comprise a total of 13 kilometres of 2.74 meter finished diameter tunnels and are both part of the York Durham Sewer System (YDSS). Both contracts require the use of EPB tunnel boring machines with a precast concrete segmental liner. The following provides an overview the two projects.

Jan 1, 2008

By Hiroshi Yamazaki

The paper describes prediction, control and validation of face pressures, and special TBM features for the bored tunnels of the New Metro Rail City Project, Perth, Australia. The selected EPB-TBM passed below a heritage bridge and the operational Perth Railway station in ground conditions consisting of fully saturated uniform sand combined with shallow overburden and a horizontal alignment radius of only 135m. Therefore, strict control of volume loss, TBM operations and ground movements was vital requiring continuous evaluation and adjustments to TBM operation parameters. The paper discusses the effectiveness of applied TBM face pressures and the used foam/polymer soil conditioning which was measured against achieved volume loss and the predicted range of ground settlements.

By Tapas Kumar Mukherjee, Sujit Kumar, Sanjay Kumar Singh

This paper dwells on the epic blast conducted at Tata Steel’s captive coal mine in India and the insights drawn from it. Optimal blast design parameters had to be ascertained for operating benches (6.56 yards (6 meters) to 16.40 yards (15 meters)) where shovels and mining pay-loaders are deployed. Better fragmentation and suitable muck profile with controlled vibration levels were the pre-requisites. The landmark blast was carried out at Quarry-AB, West Bokaro on 17th March 2017. The colossal blast was done with 275 US ton (250 tonnes) of explosives poured down 1074 drill holes of 6.5 inch (165 mm) diameter. This blast is unique from the perspective of vibration control as it was conducted near local villages situated beyond 546 yards (500 meters) but within 601 yards (550 meters)) from the blast site. The entire array of preparatory activities had been successfully and impeccably executed within the same day. The optimization was achieved through meticulous coordination between TSL team, M/s Solar and M/s IEL. When a rock is blasted, numerous interactions occur among granular particles which are impacted by rock mass properties, explosives properties, blasting geometry and the detonation timings. Optimized use of resources requires a better understanding of these interactions. Extensive field studies have shown that blast fragmentation and suitable muck profile influences the performance of downstream processes in a mine. Consequently, profitability of whole mining operation can be greatly improved through optimized fragmentation. For arriving at the best blast geometry, several blasts were conducted with differing ‘burden and spacing’ design and charging pattern at various loading benches of the mine. Eventually, the largest ever blast was successfully carried out. This accomplishment is the culmination of the insights derived, confidence built, and expertise evolved through a progression of larger blasts conducted earlier (202 US tons (184 tonnes) and 143 US tons (130 tonnes) respectively) by the same team. All blast parameters were within the recommended level and no adverse impact on nearby structures was evidenced. In-the hole VOD of different explosives was determined and placement of boosters was standardized. The signature blasts were conducted to optimize the delay interval between the holes in a row and between the rows. Blasting parameters were fine-tuned in alignment with the desired fragmentation level and muck pile profile conducive to smooth and expeditious loading and hauling by mining HEMM. Rock fragmentation analyses were carried out using photo-analysis system. The insights gained from this blast would serve as the cynosure for planning and carrying out more such blasts with highly optimized parameters in the future with the intent of improving mining efficiency and productivity

Jan 1, 2019

By KOKOWSKI J., RUDZIŃSKI Ł.

The LUMINEOS network was established in 2013 to monitor mining-induced seismicity in Legnica-Głogów Copper District (LGCD), located in south-western Poland. Since the starting time, the network was improved and today consists of 17 seismometers and 10 accelerometers. Up to now, the strongest recorded earthquake in the region had Mw4.0. Both raw seismic data and earthquakes catalog for events recorded by the LUMINEOS network are fully open and available on the EPISODES platform (https://tcs.ah-epos.eu/#episode:LGCD). During the last 7 years, the network improvements gave us a possibility to increase location accuracy for shallow mining events. This accuracy is influenced by factors such as the configuration of seismic stations, noise level at seismic stations, and the influence of the velocity model. Here we encountered two main issues which are worth to discuss. The first one is the low detection threshold of two seismic stations and their significant impact on the location errors. The second one is the large uncertainty in the S-wave picking. Even though S-waves are not so clearly visible on seismograms, they are very helpful in the estimation of source location and strength of seismic events in the region. In our work, we present the history of LUMINEOS network and corresponding improvement on location accuracy as well as the influence of noisy stations on the error distribution and how it is connected with location results. We also investigate the effect of the S-wave phases and how they are related to the accuracy of the earthquakes locations in the network.

Apr 26, 2022

By James D. Bennett, David L. Passmore

The Coal Mining Section of the National Safety Council has selected hand and finger injuries of coal miners as a major topic for safety policy analysis [Tinney, 19851. So that facts about hand and finger injuries can be used to guide the Committee's work and the work of policy-makers, we present in this paper detailed analyses of the following factors related to hand and finger injuries received by coal miners between 1975 and 1983: occupations of the injured miners; activities of the miners when injured; machines involved; objects, substances, exposures, or bodily motions that produced or inflicted the injuries; principal physical characteristics of injuries; and events directly resulting in the injuries. We analyze hand injuries for underground and surface mines separately because of the remarkably different production methods and hazards evident in these two operating environments. We do not, however, provide information about hand and finger injuries that occurred in surface operations at underground sites (such as yards, shops, or tipples), auger mining operations, culm banks, dredging operations, mill or preparation plants, offices, or laboratories. The most comprehensive information about the safety of coal mining in the United States is assembled by the Health and Safety Analysis Center (HSAC) of the Mine Safety and Health Administration of the United States Department of Labor. Mine operators in the United States report to HSAC all injuries as required under Part 50, Title 30, of the Code of Federal Regulations (mandated by Section 103 the Federal Mine Safety and Health Amendments Act of 1977, Public Law 95-164). These regulations stipulate that injuries must be reported within ten days of their occurrence on a United States government data collection form, Mine Accident, Illness and Injury Report (MSHA Form 7000-1). HSAC maintains these data primarily to produce federally-mandated reports. HSAC resolves injury reports that are incomplete, checks for errors in data coding and handling, and corrects inconsistencies in data submitted by

Jan 1, 1986

By Ashis Bhattacherjee, Bijay Mihir Kunar

A literature review on quantitative analysis of mine safety studies revealed that investigators use a wide range of statistical techniques for the analysis of mine injury data. Researchers have addressed the various issues of accident causation and prevention through analysis of mine injury data collected from mines. These studies are generally based on historical accident/injury data without considering the injured person/population at risk. In this paper, a public health approach, based on scientific methods of epidemiology, is presented to address mine safety issues. Epidemiology is the scientific study of disease and injury patterns among populations in time and space. Originally, epidemiology was concerned with epidemics of communicable diseases. Then it was extended to non-communicable diseases. Safety researchers found that epidemiologic methods are the best tools for injury research, because the occurrences of injury and the occurrences of disease are quite similar. As a result, some researchers started applying this concept to injury research. This paper presents some of the techniques used in epidemiologic studies and illustrates the application of a case-control study design to evaluate the role of some risk factors associated with injuries in underground coal mines. In this study, the injured persons were identified and, simultaneously, interviews were conducted to find the significant risk factors responsible for occupational injuries in coal mines.

Jan 1, 2011

By A. A. Ruitenberg, S. C. Johnson, L. R. Fyffe

"Several types of stratiform and epigenetic gold deposits have been found in New Brunswick, It is the purpose of this paper to describe and classify the epigenetic deposits and demonstrate their relationship to tectonic evolution. The stratiform deposits are mostly volcanogenic massive sulphide deposits that are described elsewhere (Davies et al., 1985).The auriferous epigenetic deposits include quartz-carbonate veins and stockworks, polymetallic veins, contact metasomatic, porphyry copper and volcanic breccia (epithermal) deposits. These epigenetic deposits are concentrated in major fault zones that define or are close to the boundaries of tectonostratigraphic terranes or terranes and cover sequences. The host rocks of the deposits were subjected to extensive crustal thickening resulting from thrusting and/or high angle reverse faulting.The gold deposits north of the Avalon Terrane occur indilatent structures related to mainly dextral wrench faulting that postdated the episode of crustal thickening. The deposits along the southern margin of the Avalon Terrane occur in structures related to late phase thrusting."

Jan 1, 1990

Results of laboratory studies on the flotation of marmatite (zinc sulphide) with new reagents, which were developed to avoid the use of copper sulphate, are presented.Episulphides were chosen as the basis for the reagents because of their reported special chemical affinity for zinc and cadmium. Attempts were made to solubilize and introduce functional groups to episulphides with organic and inorganic acids, ammonia, phenol, aniline, diethylamine, and pyridine. As a class of reagents, the episulphide-amine combination was generally found effective in zinc sulphide flotation to a greater or lesser degree. Best results were obtained with ethylene sulphide-aniline combination. Although anilino-ethyl mercaptan is the reported reaction product of aniline and ethylene sulphide, it was concluded that the effective zinc sulphide flotation with ethylene sulphide-aniline combination is not entirely due to the formation of the mercaptan.The economics of the possible usage of ethylene sulphide-aniline reagent are discussed.

Jan 1, 1974

By O. T. Rämö, E. Suikkanen

Episyenites are sub-solidus, quartz-depleted alkali-feldspar-rich rocks. They form veins and lenticular bodies in granitoid rocks and migmatites in a late- to post-orogenic or anorogenic setting. Leaching of quartz is usually a response to a flux of weakly saline hydrothermal solution in circulation cells above cooling intrusions, where sufficient fluid-rock ratios and thermal gradients are achieved. Fluid Si-undersaturation is achieved by rapid cooling within the field of retrograde Si solubility or by temperature and pressure increase outside retrograde conditions. Some quartz may also be consumed in metasomatic reactions and in response to pressure fluctuation in sealed episyenite bodies. The small size and overall rarity of episyenites imply that conditions for episyenite formation are not commonly encountered in the crust. In addition to quartz depletion, episyenites record complex histories of metasomatic alteration and hydrothermal mineral growth. Nearly all episyenites have undergone Na-metasomatism, which may have led to the formation of nearly monomineralic albitite, and which is occasionally followed by late K-metasomatism, phyllic alteration, and argillization. Depending on the effectiveness of later compaction, recrystallization and vug-filling episyenites may preserve the macroscopic porosity formed by quartz dissolution and brittle deformation. Vuggy episyenites can act as significant sinks for metals carried by crustal fluids and host many significant U, Sn, and Au deposits worldwide. Rare earth-critical syenitic fenites around alkaline intrusions share mineralogical and genetic traits with episyenites.

By O. T. Rämö, E. Suikkanen

Episyenites are sub-solidus, quartz-depleted alkali-feldspar-rich rocks. They form veins and lenticular bodies in granitoid rocks and migmatites in a late- to post-orogenic or anorogenic setting. Leaching of quartz is usually a response to a flux of weakly saline hydrothermal solution in circulation cells above cooling intrusions, where sufficient fluid-rock ratios and thermal gradients are achieved. Fluid Si-undersaturation is achieved by rapid cooling within the field of retrograde Si solubility or by temperature and pressure increase outside retrograde conditions. Some quartz may also be consumed in metasomatic reactions and in response to pressure fluctuation in sealed episyenite bodies. The small size and overall rarity of episyenites imply that conditions for episyenite formation are not commonly encountered in the crust. In addition to quartz depletion, episyenites record complex histories of metasomatic alteration and hydrothermal mineral growth. Nearly all episyenites have undergone Na-metasomatism, which may have led to the formation of nearly monomineralic albitite, and which is occasionally followed by late K-metasomatism, phyllic alteration, and argillization. Depending on the effectiveness of later compaction, recrystallization and vug-filling episyenites may preserve the macroscopic porosity formed by quartz dissolution and brittle deformation. Vuggy episyenites can act as significant sinks for metals carried by crustal fluids and host many significant U, Sn, and Au deposits worldwide. Rare earth-critical syenitic fenites around alkaline intrusions share mineralogical and genetic traits with episyenites.

By R M. Briggs

Kapowai Caldera Complex (KCC), located 10 km west of Tairua (eastern Coromandel Peninsula), is a late Miocene composite collapse caldera, formed during eruption of several small and large volume andesitic rhyolitic ignimbrites. Numerous epithermal Au-Ag mineral deposits and associated alteration zones at the KCC are related to caldera (rhyolite lava domes, intracaldera faults) or regional structures (faults). The main epithermal deposit exposed in the central KCC is associated with an E-W striking structural boundary fault that cuts the Welcome Jack rhyolite dome. Propylitic (calcite - chlorite) and sericitic (quartz - sericite) alteration haloes surround this deposit. Sporadic zones of sericitic alteration are also exposed within and on the margins of the Bulls Run rhyolite dome complex. Epithermal systems post-dated emplacement of these rhyolite domes, but were controlled by them. Propylitic alteration of ignimbrite in the floor of the Kapowai and Kauaeranga valleys is related to the major NE-trending Kapowai Fault which extends SW to south of Thames. Alteration along this fault pre-dates alteration associated with the rhyolite lava domes. Numerous sericitic and propylitic altered welded ignimbrite, rhyolite and andesite lava lithic fragments have been sampled from intracaldera ignimbrites, and although no direct source is known, they infer the presence of buried epithermal systems. Repeated epithermal activity at the KCC is inferred by the exposed epithermal deposits/alteration zones and the older buried geothermal systems. Silicic caldera volcanoes are considered to be critical volcanic environments for epithermal Au-Ag mineralisation in Coromandel, but are highly variable and need detailed stratigraphic, structural, petrologic, and geophysical studies to characterise them.

Jan 1, 1999

Geological models for the exploration and evaluation of epithermal Au and porphyry Cu-Au deposits rely upon a classification of different deposit styles and an understanding of the evolutionary processes of deposit formation. These models guide the interpretation of subsurface deposit anatomy in order to target drill testing and assist the explorationist to focus on the more prospective projects. It is important for the explorationist to distinguish between different styles of magmatic arc Au deposits as each style displays distinctive characteristics with exploration implications. Magmatic arc Au deposits are distinguished as porphyry Cu-Au formed at depths of 1 - 2 km at the apophysis to larger, buried, magmatic sources which are also the ultimate metal sources for the varying styles of shallower level epithermal Au deposits. Low sulfidation epithermal Au deposits characteristically develop from dilute circulating meteoric waters and are distinguished as the group with a closer relationship to intrusive source rocks, and slightly higher sulfide contents (still generally

Jan 1, 2004

By J L. Mauk

Low sulfidation epithermal deposits are important sources of gold and silver, and are considered the extinct analogues of modern geothermal systems. The aerial extents of alteration halos that surround twenty-two epithermal deposits range from 4 to 315 km2, with many less than 60 km2. Deposits with alteration halos <30 km2 typically have well defined limits, whereas deposits with alteration exceeding 30 km2 are commonly complicated by overlapping alteration centres related to adjacent epithermal deposits or other deposit types (i.e. high sulfidation, porphyry). Irrespective of the physical coverage of vein or alteration halos, both large (>60 km2) and small (<20 km2) deposits can contain large amounts of gold and silver. The size ranges for twenty-one analogous liquid-dominated geothermal fields from around the world have a restricted size range of 5 to 60 km2 and irrespective of physical size, commonly have multiple zones of focused fluid upflow. From an exploration perspective the comparison between epithermal deposits and geothermal fields provide the following four important points. 1) Alteration halos surrounding epithermal deposits as well as those for analogous geothermal systems show a range of sizes, although most are less than 60 km2. Therefore, where alteration exceeds 60 km2 multiple vein systems related to several paleogeothermal systems are predicted. 2) Multiple upflow zones are common in geothermal fields of all sizes (5 to 60 km2) and although difficult to demonstrate in epithermal deposits there is a strong possibility of discovering several discrete adjacent mineralised centres. 3) The orientation of veins parallels the principle orientation of the surrounding alteration and where alteration is wider than the vein strike length, this could suggest the occurrence of adjacent veins. 4) The physical size of both veins and alteration zones is not important in relation to amount of contained gold, as both large and small can contain large amounts of gold. These conclusions provide insight into the physical size limits and hydrologic structure of these paleogeothermal systems and highlight the potential for multiple mineralisation centres within a single alteration halo.

Jan 1, 2004

By V Poizat

In different parts of the world the term epithermal is commonly used for a variety of deposit styles. Using the redox state of the ore-forming fluid (inferred from mineralogy and alteration), the metal assemblage of deposits, and other characteristics, at least five different styles of epithermal deposit can be distinguished. Most of these different deposit styles appear to be related to magmatic fluids, with differences resulting from different compositions of source magmas. The most common style of epithermal deposit (low-sulfidation gold-silver deposits associated with calc-alkaline volcanic rocks) remains the most difficult to explain; the metals in these deposits may be derived by basement leaching without magmatic input, or they may come from magmatic volatiles, with contaminated I-type or S-type magmas as the most likely source.

Jan 1, 1995

By G. R. Wheeler

Epithermal gold exploration in the last decade has developed useful models for exploring previously overlooked ore districts in Oregon. In eastern Oregon, disseminated gold occurs in epithermal deposits that have been pervasively silicified and brecciated. Many gold prospects staked since 1980 are in fluvial and lacustrine sandstone and conglomerate deposits. Clay alteration products and disseminated pyrite may be present. Vein filling calcite and thin to thick quartz veins are common. Late stage quartz forms pseudomorphs after calcite in many prospects. Arsenic, mercury, and gold are geochemically anomalous but silver is usually not. The epithermal deposits are located in part of the Deer Butte formation or equivalent units. Exploration criteria include the presence -of Deer Butte formation or equivalent units and northwest structures cut by north-south basin and range structures.

Jan 1, 1987

By Corbett G, Iwai N

The Japanese gold mining industry has a long and productive history and is presently undergoing a period of revitalisation encouraged by the Hishikari discovery. Deposits exhibiting the characteristics of epithermal mineralisation are very widely distributed throughout the island chain and an encouraging number of these are large, seven containing gold in excess of one million ounces. All the important deposits are quartz vein type and contain extremely high grade, or "bonanza". Zones.

Jan 1, 1990

By Corbett GJ

Epithermal gold-silver deposits occur in young volcanic terrains where post-mineral cover commonly impedes the search for mineralisation. At the Togi Project in Honshu, Japan, a complex mineralised system is largely covered by post mineral volcaniclastics. A combination of high resolution electrical resistivity surveying and detailed airphoto interpretation has, with close geological control, enabled synthesis of structural and alteration characteristics of the Togi geothermal system, in turn permitting ranking of the prospects for drill testing.

Jan 1, 1990