Search Documents

By Nicola Della Valle

The Singapore Land Transport Authority (LTA) is currently expanding capacity by extending their Metro system from South of the city to the North East end of the island. The scope of Contract 704 involved excavating a long reach of tunnel which had a complex rock/soil interface comprised of fresh granite overlaid by clayey sand. Two 6.5 m diameter Earth Pressure Balance (EPB) TBM’s were used to bore the tunnels. These machines were designed so that both hard and soft rock could be excavated. The cutter head was equipped with a combination of both rippers and disk cutters. Soil conditioning was achieved by delivering foam through a multiple port injection system. This very irregular profile of the interfaces posed many challenges to the equipment and the people.

Jan 1, 2001

By Paul B. Queneau, Barry J. Hansen, D. Erik Spiller

Most lead and zinc secondaries are recycled pyrometallurgically. However, many problems encountered in secondary smelters have been solved by addition of physical concentration and/or hydrometallurgical processing steps, with resulting important environmental benefits. U.S. secondary lead and zinc operations are described, covering conventional smelters, EAF-dust treaters, and zinc sulfate/fertilizer producers, including plant capacities, technologies, and outputs. During the past two decades, remarkable advances have been achieved by recycling spent lead-acid battery components. Interaction between primary and secondary zinc producers, the fertilizer industry, and the zinc chemical industry has substantially decreased waste generation.

Jan 1, 1993

By Carl (Original by) Hrovatic

Land is a precious resource and should be treated as such by all members of our society. The soil covering this earth is only a very thin outer layer, varying in thickness from a few inches to a few feet and covering the rocks and minerals lying beneath the surface. The wise use of this valuable commodity is the responsibility of everyone. Many everyday activities disturb e earth's surface. Examples are highway construction, housing and commercial developments, agriculture, and various types of mining. This chapter discusses the relationships of the environment to land as it applies to surface operations in the coal industry. Mining by surface methods disturbs, for a brief period of time, thousands of acres of land annually. In addition, refuse piles, slurry ponds, abandoned mine structures, unprotected mine openings, and unsightly cleaning plants can also adversely affect land unless properly handled.

Jan 1, 1981

By Wolfgang Güter, Paolo Romualdi

Current extensions of the European railway network require long TBM drives in the diameter range of 10 m under critical and varying rock conditions. In view of that and in particular for a 7 km long high-speed railway tunnel in Spain to be started in mid-2003 a new design for a hard rock Double Shield TBM has been developed by SELI (Italy) and Jäger (Austria) in collaboration with Mitsubishi (Japan)and Robbins (USA). Due to the new design and operational features that new type of TBM has been named Universal Double Shield TBM with a further extended area of application. Special attention has been given to outstanding torque and thrust capacities combined with the shortest possible length of an innovative shield arrangement, different advance modes in various ground conditions and further developed exploration and treatment facilities.

Jan 1, 2003

By E. Medina, W. Callupe, R. Sharon

Slope stability in Barrick’s Pierina Mine open pit is significantly influenced by the structural geology, the variably argillized rock mass, and locally by perched groundwater. Development of an extensive surface water diversion network continues at Pierina, which is necessary to minimize highwall and adjacent natural landslide movement and erosion during the wet season. Slope movements are effectively monitored using optical survey methods, strobe light extensometers, gap monitors, and piezometers. The slope stability program at Pierina is focused on improving the understanding of the stability mechanisms in order to ensure continuous safe operating conditions. Priorities are placed on developing an accurate detailed engineering geological model, enhancing groundwater depressurization, and optimizing highwall controlled blasting procedures.

Jan 1, 2003

By Robert J. Mac Kinnon

A moving grid finite element model for the analysis of transients in a rock mass surrounding an underground coal conversion cavity is presented. Major model components are outlined, including a special element formulated to account for internal discontinuities. A numerical example is described.

Jan 1, 1986

This chapter contains the edited transcript of the "Gold Heap Leach Information Exchange" session that was held at the 1990 SME/AIME Annual Meeting in Salt Lake City, Utah. The exchange occurred on the afternoon of February 27, 1990. The session was intended to act as a forum for discussing some of the more prominent operating problems associated with heap leaching precious metals. The information exchange was very successful. The exchange consisted of several panelists introducing and discussing different topics, follow by a comment and question period. This transcript contains the panelists' presentations as well as comments and questions from the floor and the panel. Extraneous comments and remarks have been edited out. Some wording has been changed for clarity, but the transcript is basically an accurate account of what was said. At the end of the transcript are two papers submitted as part of the panel discussion

Jan 1, 1990

By G. Machiavelli, P. Bevilacqua, G. Ferrara, T. P. Meloy

During several years of operation in Europe, South Africa and other locations, the Tri-Flo process has demonstrated substantial improvements in dense-medium dynamic-separation systems. The reasons for this improvement are: • a high-sharpness separation due to the multistage system and the application of new concepts in the design of the regeneration circuit and in the control of the medium Theology, and • the possibility of performing two cuts at different densities using a single separation device and a single regeneration circuit. This paper discusses the above points in detail with particular reference to the multistage technology (based on the circuit analysis theory) and to the control of the medium rheology (based on recent work in the modeling and simulation of the rheological behavior of dense suspensions). Concerning the multidensity separation, information is given on the new three-stage separator where the high-density separation is performed by the first stage and the low-density separation is performed by the second and third stages. This configuration (already realized in two operating plants) was selected because no particular sharpness was required at the high-density separation, while high sharpness was required at the low-density separation. However, the configuration can be inverted or a fourth stage can be added (at very low additional cost) to provide two stages for each separating density. The importance of achieving a high sharpness separation is related to minerals (industrial minerals in particular) where the density difference of the phases to be separated is very low (as in processing of lithium ores, feldspar- and others). Information is provided on plants operating in South Africa and Canada, for the beneficiation of lithium minerals and on a plant under construction in Italy for the beneficiation of feldspar. Finally, the importance of making the separation at two densities is emphasized with particular reference to coal; i.e., producing a low-ash premium coal and recovering, in the middling, a by-product without losing heating value. Also, very important for some minerals is the production of a high-grade concentrate (at the first stage) suitable for sending directly to metallurgy (e.g., chromite ores) and the production of a low-grade concentrate that can be further treated. In this way, a higher overall recovery of the valuable mineral can be achieved, and, at the same time, a reduction of the treatment costs can be obtained. All of the above applications were once considered impossible.

Jan 1, 1995

By Georgios Kafantaris, Carsten Bonde, Nataša Katic

Within the investigation works for the Copenhagen Cityring metro, Geo/CMT have carried out 90 geotechnical boreholes. Together with the previously available investigation, this resulted in more than 15 km of vertical drillings and several thousands of laboratory tests. The design is made for 17 stations, four shafts and two parallel 16 km long tunnels. The geotechnical investigation and design have been carried out in several stages comprising appropriate refinement of structural design and design of excavation operations, including TBM break-in and launching operations at each station shaft. Acceptance of the solution and / or refinement of the investigation and design schedule in the next stage were based on the geological conditions, area availability at surface level, planning and cost-control criteria. The applied recursive design refinement is presented herein with an example of the Østersøgade shaft location.

Jan 1, 2016

From some of the largest tunnel projects in the some of the most vibrant cities, to smaller projects in remote corners of the globe, the Robbins Co. announced two tunneling projects in which its tunnel boring machines will be used. Robbins earth pressure balance (EPB) machines undercut Downtown Zhengzhou. Zhengzhou, a city of 7 million people, is set to become a crossroads for rail commerce in China. The country?s future main routes, traveling between Beijing and Guangzhou (North-South), and between Xuzhou and Lanzhou (East-West), will intersect in the city. The plan includes up to four rail lines in Zhengzhou itself, which will eventually link up to the national lines. Excavation of Zhengzhou Metro?s new Line 1 tunnels began on Sept. 28, 2010, when the first of two 6.3-m (20.7-ft) diameter Robbins earth pressure balance (EPB) machines was launched from a 16-m- (52-ft-) deep shaft.

Jan 1, 2010

By Eugene R. Palowitch, Albert W. Deurbrouck, Thomas H. Parrsons

INTRODUCTION Hydraulic concentrators utilize the physical characteristics-size, shape, and specific gravity-of particles suspended in a fluid medium to effect a concentration of desired quality. Fine-coal concentrators include generally those devices which are used to clean roughly 3/4, in. (9.5 mm) top-size coals. While this size designation is somewhat arbitrary, it is consistent with current practice although some fine- coal concentrators can treat coarser coals effectively. A variety of devices have been and are currently being used to wash fine coals and include: dense media cyclones, wet concentrating tables, hydrocyclones, jigs, spirals, launders, and upward-current classifiers. As launders and upward-current classifiers have been replaced by more efficient devices, they no longer warrant consideration as fine-coal washers. And as fine-coal jigs were addressed with the Baum jig under Part 1, Section 2, and heavy media cyclones and hydrocyclones were addressed under Part 2, Section 1, of this Chapter, only the wet concentrating table and the spiral concentrator will be discussed here. WET CONCENTRATING TABLES History The current wet concentrating table evolved from continuous belt concentrators which utilized a flowing film of water to recover heavy metals. In these devices the heavier concentrate moved up the inclined plane of the belt while the lighter impurities were washed away by water flowing down the belt. The natural outgrowth of the continuous belt concentrator was the vanner, a vibrating endless belt which was first developed about 1860 by Hartwig. Later models of the vanner, such as the Frue, incorporated oscillation in a plane transverse to the direction of the water current. Excellent descriptions of these washers are found in The Cleaning of Coal, by Chapman and Mott.80 Further development of tables included the circular stationary table (Linkenbach), the multiple round table (Anaconda-Evans), the bumping table (Campbell), and finally the differential-motion table which is now used extensively for cleaning fine coals.

Jan 1, 1991

By Steven W. Hunt

"A paper called “Global Experience with Soft Ground and Weak Rock Tunneling under Very High Groundwater Heads” was presented at the North American Tunneling 2006 conference (Holzhäuser et.al 2006). It summarized global experience with earth pressure balance (EPB) and slurry shield tunneling on nine projects that encountered groundwater heads ranging from 6 to 11 bar. Since then, additional projects have been completed with groundwater heads ranging from 7 to 15 bar. Of these, the high pressure tunneling experience on the Lake Mead Intake No. 3 project in Nevada and on the Eurasia Tunnel (Istanbul Strait Crossing) had the greatest lengths of tunneling at face pressure over 7 bar. Experience with sustained pressurized face tunneling at groundwater heads over 7 bar and risk management observations are the focus of this paper. INTRODUCTION High groundwater head, particularly at 7 bar or more, is a major challenge when tunnelling in high permeability ground and on drives long enough to require cutter changes. It has a strong impact on design and operation of Tunnel Boring Machines (TBMs) in order to protect the main bearing from contamination, prevent excessive groundwater inflow, ensure face stability and enable access to the cutterhead and excavation chamber for maintenance. During the past 20 years, TBM manufacturers and suppliers have made tremendous improvements that allow tunneling at groundwater pressures to 17 bar or more. The most significant risk with high pressure tunneling is generally that of excavation chamber access and potentially the cutterhead for cutter changes, cutterhead repairs and TBM maintenance. Hyperbaric interventions are possible and safety variances have been approved for saturation dive interventions at pressures as high as 17 bar (Lake Mead Intake No. 3). While high pressure hyperbaric intervention equipment is available and safety approvals can be obtained at many locations, few contractors consider the cost and risk of hyperbaric interventions over 7 bar to be acceptable as the primary means of excavation chamber access. Experience with high pressure tunneling prior to 2006 was summarized in a paper entitled “Global Experience with Soft Ground and Weak Rock Tunneling under Very High Groundwater Heads” (Holzhäuser et.al 2006). That paper provided information on 9 projects: South Bay Ocean Outfall, San Diego; Channel Tunnel (French Side), France; Storebaelt Tunnel, Denmark; 4th Elbe Tunnel, Germany; Wesertunnel, Germany; Westerschelde Tunnel, Netherlands; St. Petersburg Red Line, Russia; Nara Prefecture Water Conveyance Tunnel, Japan; and Tokyo Wan Aqua Line Tunnel, Japan – see Table 1."

Jan 1, 2016

By Edwin Itzig-Heine, Daniel Traylor, Bernard Tarralle, Michael McKenna

This paper discusses the challenges associated with the design and construction of a dual-cell, “figure eight” shaped shaft in saturated, soft ground for the Northeast Interceptor Sewer project in Los Angeles. The shaft will be excavated to a depth of41 m and used to launch two EPB TBMs. The specifications required concrete diaphragm walls, embedded below the shaft invert, and a grout curtain beneath the wall. To control water pressure and basal stability without a grout curtain, wall panels were embedded deeper than required into a stiff, cohesive deposit. Details of wall panel excavation using a Hydrofraise are presented.

Jan 1, 2003

By I. Papadopoulos

Nowadays, geophysical prospecting is implemented in order to resolve a diversity of geological, hydrogeological and geotechnical problems. Though plenty of applications and a lot of research have been conducted in the country-side, only a few have been reported in the literature concerning urban areas, mainly due to high levels of noise present that aggravate most of the geophysical methods (e.g. electromagnetic, seismic, gravity etc.) or due to spatial limitations that hinder normal method implementation (e.g. electrical). Among all geophysical methods, electrical tomography proves to be the most rapid and urban noise insusceptible technique. This work presents a case study in the urban area of Hania (Crete I., Greece), where Electrical Resistivity Tomographies (ERTs) have been carried out for the detection and identification of possible buried ancient ruins or other manmade structures, prior the foundation of a building. Nineteen profiles were surveyed in a 20x40m grid using dipole-dipole configuration. The results indicate two areas of interest, that are interpreted as probable old wells, in the context of the existence, in former times and in the same area, of an olive oil plant. In the vicinity, near surface ancient ruins have been disclosed, but no such evidence provided this survey, for the particular area under study and the prospected depth. The collected ERT-data were processed by applying advanced algorithms in order to obtain a 3D-model of the study area that depicts more clearly and accurately the interesting subsurface structures.

Jan 1, 2005

By Thomas V. Mullen

Some 146 kt (4.69 billion oz) of gold have been mined throughout history. Of this, 70% has been mined in this century alone, with 17% produced from 1985 through 1996 (Fig. 1 and Table 1). Until the mid-19th century, placers were the chief source of gold. Advancements in mining, metallurgy and geological thinking have resulted in underground mining (first of veins plus stockworks and later of Rand-type deposits) becoming the principal source of gold. With the demise of the South African deposits and the move towards lower grade ores, the primary source of gold will be from disseminated deposits exploited through large, open-pit mines. For the past 200 years, there has been a fairly constant ratio of about 31 g (1 oz) of gold to each person alive. If this ratio is to be maintained, annual gold production will have to rise from about 2.3 kt/a (73.9 million oz/year) to more than 3.1 kt/a (99.7 million oz/year) by the year 2000. To effect this increase, an unforeseen breakthrough in exploration or metallurgy is needed. Barring this, there will be pressure for an increase in the price of gold. This article traces the historical production of gold from 4000 B.C. - the earliest record of gold mining - to today and relates this 6,000-year record to advances in geological thinking, mining engineering and extractive metallurgy. It also proposes that man's thirst for gold, reflected in the price he will pay for gold, and his ability to find, mine and refine gold have combined to effect an equilibrium based loosely on the historical ratio of 31 g (1 oz) of cumulative gold production per each man or woman alive.

Jan 1, 1998

By James R. Jones

The concern for air pollution goes back centuries as will be seen from this quotation : "Strife and coal, it seems, have a hand-in-hand historical relationship. It was thought by some . . . in the Middle Ages that burning coal filled the air with dangerous poisons. So great was the concern that in 1306 King Edward I of England passed the first and unquestionably the harshest air pollution legislation edict that history will record. His proclamation declared the use of coal an act punishable by death." As related to coal mining, the air pollution problem is primarily that of its customer when using the fuel. Thus the major impact relates to markets for coal rather than the actual mining operation itself. In the vicinity of the coal mine the problem is principally related to fugitive dust from roads, transfer facilities, loading facilities, crushers, etc., and particulate matter (dust or fly ash) from thermal dryers and air cleaning tables.

Jan 1, 1981

By Thibaut Pannetier, Damien Rogat, Catherine Larive, André Regnard, David Chamoley

"INTRODUCTION For several decades, the use of fibre-reinforced sprayed concrete (FRSC) has been becoming increasingly widespread, either as a replacement for or in addition to traditional reinforcements. Macro-synthetic fibres appeared on the market at the same time as metal fibres (in the 1980s), but their use has developed more recently in France, starting in the early 2000s. While their properties are attractive for underground operations, their long-term performance remains the subject of some controversy, particularly with regard to the phenomenon of creep [1-5]. Unfortunately, the many differences of protocol among the studies carried out (materials, metering, spraying equipment and test methods, etc.) mean that, in general, the results cannot be compared. Although several methods have been developed to assess the bending creep behaviour of fibre-reinforced concrete, the majority of them test notched beams resting on isostatic supports. There are currently no standardised test methods adapted to FRSC on hyperstatic supports (as is the case for FRSC used for underground support). The Asquapro association has thus developed a new test specially designed for this type of concrete. Slabs of thickness 10cm, measuring 60 x 60 cm in plan have been sprayed and tested under bending stress according to a test procedure inspired by the standardised test of energy absorption capacity (NF EN 14488-5). An experimental campaign was launched in October 2014 to study the behaviour of seven types of sprayed concrete, manufactured using the same concrete matrix: six of them were reinforced with different metal or macrosynthetic fibres and the seventh with a welded wire mesh. Fourteen slabs were sprayed for each type of concrete and also for the non-reinforced concrete with the same matrix. The types of mechanical performances measured were the compressive strength and energy absorption capacity (at seven and twenty-eight days), in addition to the creep behaviour of these seven types of concrete, placed under stress on the seventh day. This article follows on from that published in the WTC 2015 congress proceedings [6]: the programme and the test methods are briefly described here and the results available at the time of writing are presented and discussed."

Jan 1, 2016

By D. R. Babich, E. R. Bauer

Noise-Induced Hearing Loss (NIHL) continues to be a concern of the mining industry. A new noise standard (30 CFR, Part 62) is aimed at reducing NIHL in mining through engineering and administrative noise controls. However, the difficulty and expense of implementing engineering controls can make administrative controls an attractive alternative for reducing worker noise exposure. Over the last three years, the National Institute for Occupational Safety and Health (NIOSH) has conducted worker noise exposure surveys in underground and surface coal mines and coal preparation plants. The surveys revealed numerous possible administrative controls and an approach to implementation and analysis. The surveys have shown that worker dosimetry, time-motion studies, and equipment noise profiling are important aspects of effectively utilizing administrative controls. A description of the approach for selecting, implementing, and evaluating administrative controls, and a list of administrative controls, are reported.

Jan 1, 2004

By G. T. Adel, J. D. Miller, C. L. Lin

In view of the success of recent laboratory studies using X-ray computed tomography (CT) to determine coal washability and with the availability of high-speed CT systems, it now seems possible to design an on-stream washability system for the control of coarse coal-cleaning circuits. Design features for such a system are examined and possible control strategies are discussed for different applications.

Jan 1, 1995

By A. P. Grippo, L. B. Phelps

Many coal mining companies have potential surface mine reserves that either are known or suspected to have had prior drift mining activity on them. In many cases, there is no documentation on these mines or, at best, very fragmented records. These undocumented abandoned underground mines are creating engineering, financial, and environmental difficulties and concerns for both surface coal mine operators and regulatory personnel. This paper examines the use of resistivity techniques in detecting entries of abandoned drift coal mines. The detection of such a drift mine entry would confirm the presence and orientation of an abandoned underground coal mine.

Jan 1, 1987