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By B. Caro Vargas

The Toulon South Tunnel in France is the second part of a project started 20 years ago. After the problems and delays suffered during the construction of the North Tunnel, due to a complex geologic context of highly fractured and soft rocks under a highly urbanized environment, a very dense automatic monitoring system was implemented to control the settlements of surface (more than 1000 points), the structures adjacent to the tunnel alignment and the underground galleries being constructed. The latest automatic instrumentation systems were installed, using for example AMTS capabilities in terms of ?automatic prismless settlement monitoring?. All the data (geotechnical, structural and geological) was gathered in a global automatic data acquisition system and continuously available on a web based interface. Three different threshold levels (notification, anomaly, alert) were set up, each one with a differential and an absolute value for settlements. Depending on the actual geological site conditions and the actual monitored settlements, different supporting systems and excavation techniques were used. Furthermore, the monitoring data was also used to predict and anticipate the future settlement, by comparing it continuously with the theoretical Peck settlement curves. This method allowed a better risk management by limiting the settlement on existing structures and helped to secure the Works progress schedule, for a project that lasts from July 2007 to March 2011. The implementation of this observational method application is presented in this paper.

Jan 1, 2012

Face and pillar bursts, bumps and bounces are violent failures that occur in underground coal mines in response to a complicated interplay of face and pillar geometry, seam depth, coal properties and interactions between roof, seam and floor strata. Additional complications arise from the presence of gas, mainly methane, and associated pressure and flow that vary with time and are further influenced by the rate of face advance. Where gas plays a dominant role, the term outburst is often used; where stress concentration is primary, terms such as burst, bump or bounce may be used. Hargraves [1983] presents an often cited review of outburst phenomena with emphasis on Australian conditions. Beamish and Crosdale [1998] indicate outbursts have occurred for over a hundred years and present tabulations of outburst numbers in major coal basins throughout the world. A central consideration is the rate of depressurization that occurs in the course of mining. Outbursts are not limited to coal seams and adjacent strata; they also occur in salt and potash mines [Molinda et al 1988]. Stress concentration and gas pressure act in consort, so the combined action is important to understanding the mechanics of bursts or outbursts and to the development of measures to reduce the associated hazard. Gas flow is a complicated phenomenon associated with diffusion of gas from micro-pores and the flow of gas along cleats. Laboratory measurements indicate both are dependent on stress and pressure [Harpalani and Ouyang 1998]. Moreover, gas permeability in porous media is often many times water permeability [Klinkenberg 1941]. However, there is also evidence that gas and water permeability are similar at elevated stress and follow Darcy?s law [Dabous et al]. Gas flow is also of importance to mine ventilation. Price et al [1973] in cooperation with personnel of the former U.S. Bureau of Mines developed finite difference models to estimate methane emission in mines in the Pocahontas No. 3 and Pittsburg seams using a premining pressure of 4.69 MPa (680 psi) and Darcy's law implying laminar flow. However, the effects of stress were not taken into account. In this regard, mine measurements of permeability are usually based on Darcy?s law [Peide 1990]. Early models of gas flow with stress effects were one-dimensional in space and time (x,t) and were developed with the goal of estimating the gas pressure profile from the face into the seam as time passed [Schlanger and Paterson 1987, Zou and Yu, 1999]. A zone of high permeability adjacent to the mining face was recognized in these early models. Later models based on the popular finite element method allowed two spatial dimensions (x,y) and variation in time (t) and for coal seam heterogeneity [Tang et al, 2002]. Zhu et al [2007] formulated a set of nonlinear equations involving a complicated stress-pressure-permeability relationship for application to coal seam gas flow and concluded the coupling was important but failure of coal should also be considered. Wold et al [2008] used a hybrid finite difference - finite element model interleaved with a reservoir simulation model to study outbursts based on extensive mine and laboratory measurements. An important feature of the modeling was the use of spatially variable material properties and Monte Carlo simulation to obtain quantitative estimates of outburst conditions and probabilities. Connell [2009] used the same reservoir simulation model as Wold but used the popular finite difference code FLAC3D for hydro-mechanical responses to evaluate two permeability relationships, one depending on porosity and the other on stress, and concluded that permeability changes with gas production were more complex than computed by either permeability model. Gadde [2010] in an integrated laboratory and field study of coal pillar strength explored the effect of spatial variability and concluded that design based on average strength was acceptable in some circumstances, although gas pressure was not an issue. Liu et al [2011] also applied a FLAC code to analyze two-dimensional gas flow and deformation of layered but homogeneous strata in a Chinese coal mine using a strain-softening model and concluded that damage and gas pressure were important to strata safety relative to the case without gas.

Feb 27, 2013

By T. Weatherwax

As part of a strategic research initiative at UBC to design and evaluate integrated underground mining and mineral processing systems, work has been done to determine how to utilize the coarse rejects of pre-concentration in the underground environment. An amenability study for nine orebodies from four of Xstrata Nickel?s Ontario operations evaluated both processing and waste disposal methods. The utilization of the rejects as a high quality backfill with minimal binder requirements has been identified as the preferred disposal method. Fill mixes utilizing the rejects in combination with classified tailings, full tailings, and cement were developed based on the geotechnical properties of the rejects. The mix designs were examined for both strength and rheological properties. The paper will present the results of the pre-concentration testwork, the design and strength testing of various mix designs for rejects from the nine ores and presents a conceptual design for an underground pre-concentration system based on this test work.

Jan 1, 2008

By G. S. Takenaka

When Bridger Coal Company transformed their operations from surface mining to an underground longwall operation their plans included not only the addition of new mining equipment but also surface fans for a blowing (supply) air ventilation system. The original system concept included a propane gas fired air heater to preheat the intake air during cold weather and a dual parallel fan and duct system. One fan operated to ventilate the mine while the other fan was for stand-by emergency operation. Equipment proposals were submitted in March, 2005 based on the dual parallel fan system. Discussions conducted during the equipment selection process revealed that several alternative system design concepts were available. The alternative concepts included innovation features that not only saved space and cost but also reduced operating expense as well. Many of the features were incorporated into the final design of the system. A comparison of the original system concept and final installation design are presented in the paper in addition to details of the features and the derived benefits.

Jan 1, 2009

By Douglas R. Cook

Exploration record In preparing this paper, a list of world class discoveries prepared in 1983 has been updated. In both surveys, the following criteria were used in the definition of world class discoveries: • deposits that are continuously operated and consistently return a profit even in periods of low metal prices; • deposits large enough to significantly affect a medium sized corporation's profits; and • these deposits should be in the lower one-third cost per unit of metal produced for all similar deposits. Only 70 discoveries in the last 40 years qualified as world class deposits using these criteria. Unfortunately, this restricted population was too low to develop meaningful trends. The numbers were therefore enlarged to include all significant discoveries. The principal feature of a significant discovery is that its size and grade would yield more than $500 million in revenue using average metal prices for the last five years. A significant deposit should also meet some of the standards for a world class deposit. A tabulation of these deposits are shown in Table 1. The number of discoveries increased to 166 from 70 using the revised classification. The relationship between the number of discoveries per year and their location by continents was prepared from these data. Figure 1 shows the number of discoveries per year for the nonCommunist world. It also shows estimated and actual nonCommunist world exploration expenditures per year and the commodity price index. These data show that modern exploration started in the late 1940s, with the tempo picking up rapidly in the 1950s. The maximum discovery rate occurred in 1962. Thereafter, the discovery rate gradually declined to the present. This occurred despite a real increase in expenditures from about $200 million/a in 1955 (1982 constant dollars) to more than $900 million/a in 1980. Thus, these data suggest a significant decrease in the exploration success ratio (total exploration expenditures a year divided by the number of significant discoveries) in the last 20 years. As an example, $70 million was spent for each significant discovery in the early 1960s as compared with $225 million in the late 1970s (expressed in 1982 constant dollars). However, with the general declining trend of discoveries, one can perceive a more pronounced drop in 1973 and then a sudden increase in 1974, 1975, and 1976. This increase is probably related to the inflation of the 1970s that in turn created an environment for the explosion of commodity prices, as shown by the commodity price index on Fig. 1. Thereafter, the decline in discoveries resumed in 1975 until the present. Exploration performance by regions North American discoveries are shown in Fig. 2. The graph shows three pronounced high discovery peaks in 1962, 1975, and 1980-81.

Jan 2, 1986

By J. B. Gwiazda

S.S. Peng The highlights of this paper are : • The shield supports with lemniscate links will exert a tangential force on the roof strata, causing unnecessary and harmful roof movements, thus damaging the roof structure. The principal source of the tangential force is the horizontal movement of the point O, the pivotal joint between the canopy and the caving shield. When the support height is changed during setting, the point O will move along a curve upward and rearward toward the gob. As a result, it produces a vertical movement, causing the roof to move up a distance of ?d, and a horizontal movement toward the gob, creating vertical fractures in the roof. • The major purpose for employing the lemniscate-link system is to protect the hydraulic legs against the action of the bending moments induced by the tangential force that causes deformation or destruction of the legs. • Based on these two points, the author suggested that, in order to eliminate the harmful effects of the lemniscate-link system and strengthen its advantageous features, a shield support with a new design of that mechanism has been developed. With the new design, the conventional rigid lemniscate links are replaced by hydraulic rams. When the pressure inside the rams reaches a certain level, the ram will yield.

Jan 12, 1986

By A. B. Hazar-Yoruç

Ferrochromium produced by smelting chromite ores is an important alloying component in the steel industry. Ore, coke and fluxes are mixed and reacted in an arc furnace for a smelting process of ferrochromium. In ad-dition to this process, pre-reduction of chromite ore with carbon is an important industrial process. In all these processes, the mechanism and kinetics of reduction of chromite with carbon play an important role. In this study, the reduction of Turkish chromite ore with carbon was investigated. Chromite and carbon were ground to three different particle size groups. Chromite was mixed with carbon in stoichiometric and excess ratios. The samples were reduced under argon atmosphere at temperatures between 1,200° and 1,350°C. The formed phases and alloy compositions of reduced chromite samples were analyzed by optical microscopy, scanning electron microscope (SEM) with EDAX and X-ray diffraction analysis (XRD). Experimental results showed that the degree of reduction and the reduction rate increased with increasing temperature and decreasing particle size. The highest degree of reduction, 61.4%, was obtained at 1,350°C. The reduction took place in three stages: Stage 1: transformation of Fe3+ to Fe2+ and formation of metallic nuclei, Stage 2: formation of metallic crust around the particles and Stage 3: growth of the metallic crust and coalescence of the metallic phase.

Jan 1, 2007

By A. Moergeli

The Swiss are building the world’s longest tunnel, the 57-Kilometer (35-mile) long Gotthard Base Tunnel. Lot 252, Tunnel Amsteg: Two Hard Rock Tunnel Boring Machines (TBM) crossed hydro-thermally decomposed granite. While the East TBM advanced slowly but steadily, the West one got stuck for five months and had to be recovered by special means and methods. Both TBMs have finished their more than 11-Kilometer (7 miles) long drives successfully. Lot 360, Tunnel Sedrun: For the first time in tunneling, roadway support machines are used through most challenging, squeezing geology. They constantly advance in full face mode for about one Tunnelmeter/24 hours.

Jan 1, 2007

By David Hake, David Salisbury

The Drainage Services Department (DSD) of the Hong Kong SAR Government commissioned the design and construction of the West Kowloon Drainage Improvement, Stage 2, Phase 2, Kai Tak Transfer Scheme (KTTS) project in 2000 to relieve potential flooding in Mong Kok caused by the insufficient capacity of the existing storm water drainage system. The KTTS involves construction of a 1.5km,4.4m drainage tunnel and a 450m long box culvert, running from Waterloo Road near Hereford Road to the existing Kai Tak Nullah in San Po Kong. This paper describes the design and construction of; the bored tunnel through both hard rock and soft ground using a slurry Tunnel Boring Machine (TBM), six associated access shafts, a connection structure at Waterloo Road and the box culvert connecting the bored tunnel to the outfall at Kai Tak nullah. Details will be provided on the contractor’s alternative designs adopted during the contract including the use of fibre reinforced shotcrete as one-pass temporary and permanent support for three of the shafts and modifications to the Engineer’s design for the box culvert structure.

Jan 1, 2005

As the 2009 George Fox Conference neared its conclusion, Arthur Silber, project chief of the Mass Transit Tunnel (MTT) project was able to pull away from the constant buzzing of his Blackberry long enough to give a short presentation and a significant piece of news to the record 318 attendees at the Graduate Center, City University of New York regarding the MTT project. ?As the former administration (The Bush administration) was leaving office, we were told that Congress was notified of the FTA?a (Federal Transit Authority?s) intent to issue final design construction approval to us,? Silber said of recent advancements concerning the $7.2-billion dollar project. It will add passenger rail service from New Jersey to New York City as part of the Access to the Region?s Core project in the form of the Trans Hudson Express Tunnel (THE tunnel). ?That 10-day waiting period ended yesterday (Jan. 26).? In days leading up the Fox Conference, those involved in the tunneling industry, and the MTT in particular, had a lot to be optimistic about. The MTT received environ-mental approval on Jan. 14 (see page 9) and, with the acceptance of the final design, the multi-billion dollar project moved that much closer to a ground-breaking ceremony. So close, in fact, that before leaving his office for the conference, Silber posted the contract documents and plans for the Manhattan Tunnel project online at www.arctunnel.com (an indepth look at the project from Silber is on page 22). While many were interested in the progress of the project, Silber also spoke about the new plans for the cavern complex at the New York Penn Station expansion. The original plans called for two lines that would come into a large cavern complex with a north and south cavern to access the trains. After numerous core samples were taken from the streets of Manhattan, it was deter-mined that this design was not feasible and changes were made that will include a deeper cavern under Sixth Avenue, with 14-m (45-ft) of cover with a 30-m (96-ft) wide cavern that resides entirely under 34th Street. The cavern was also moved 20 m (60 ft) to the west to remain at least 61 m (200 ft) away from New York City Water Tunnel #1. The new design will include three-over-three track arrangement. The mezzanine will be 46 m (150 ft) below street level at 8th Ave, Silber said.

Jan 1, 2009

The Mining Foundation of the Southwest (MFSW)promotes public understanding and education related to the mining industry. Towards this goal, the Foundation has funded several projects from donations and fundraising activities. The MFSW was incorporated in 1993 by combining the Mining Club of the Southwest and the Mining Club of the Southwest Foundation. The Mining Club began in 1971 as a social organization. It provided members of the mining community an opportunity to meet. The club also provided a means for public education about mining. In the early 1990s, the club’s efforts were directed mainly toward educational activities. And in 1992, discussions began concerning incorporation into a non-profit foundation to further the public understanding of mining. In 1983, the American Mining Hall of Fame was inaugurated to honor significant contributors to the industry and profession. The Hall of Fame serves to educate people about prominent persons associated with the mining industry, present and past. The honorees number 75. Plaques commemorate their induction and are on display at the Arizona Historical Society’s Museum in Tucson, AZ. The combined honors ceremony and banquet have remained one of the fund raising activities.

Jan 1, 1999

By M. R. Shahan, W. R. Reed, J. P. Rider

Roof bolter operators may be exposed to high respirable dust concentrations on continuous miner sections with blowing face ventilation when bolting is performed downwind of the continuous miner. One solution to reduce the high respirable dust concentrations is to use a canopy air curtain (CAC) to deliver clean air from a filtered blower fan directly to the bolter operators under the canopies. The influence of CAC installation in the airflow and dust dispersion around the location of the roof bolter operator can be evaluated by using computational fluid dynamics (CFD). This study, performed by the National Institute for Occupational Safety and Health (NIOSH), considers two scenarios: (1) a roof bolting machine in the center of the entry for installation of the fifth row of bolts from the face, and (2) a roof bolting machine positioned close to the face for the installation of the last row of bolts. In both scenarios, the bolting machine is placed in an environment which contains 6.0 mg/m3 of respirable dust and is ventilated by a blowing curtain with 3000 cfm (1.42 m3 /s) of air. This environment is used to simulate the roof bolter machine operating downstream of a continuous mining machine. Two operation positions are simulated at the same bolting location: dual drill heads in the inward position for two inside bolts and dual drill heads in the outward position for two outside bolts. The influence of the CAC on airflows and dust dispersion is evaluated with the CAC operating at 250 cfm (0.12 m3 /s).

By A. Broussaud, J. D. McKay

Benefits analysis of adaptive Expert control systems operating at plants in Africa and the United States are presented. Proper statistical tools and techniques are discussed. Technical and practical pitfalls of strategy comparison are also presented and illustrated with from published data. Advantages and disadvantages of a “Pay for Performance” approach to a project are reviewed.

Jan 1, 2001

By Amanda Elioff

Success of the Gold Line Eastside Ex-tension rail tunnels in Los Angeles, CA has prompted the Los Angeles County Metropolitan Transportation Authority?s (Metro) planning new rail lines to include underground alternatives. The Westside Extension Transit Corridor alternatives include up to 27 km (17 miles) of subway to be constructed in soft ground. The routes will require construction in Los Angeles? ?potential methane zone,? which was not considered for subway construction until recently. Slurry face tunnel boring machines (TBM) will likely be specified.

Jan 1, 2009

By T. R. Ellis

Minerals Appraisers/Valuers often find great difficulty or failure in attempting to employ the Sales Comparison Approach to the Market Value Appraisal of development and operating stage mineral properties. An important factor generally overlooked is a comparison of net operating income (NOI) margins on a per-unit-of-production basis between mineral properties, whether these be demonstrated or forecast margins. NOI margins can vary greatly between mines or quarries that are producing similar products. Ultimately, the expected NOI margin determines what a buyer is willing to pay for an income producing property. Common criticisms of the sales comparison approach by minerals appraisers are introduced. These are counterbalanced by raising some issues in the way the inputs for the Income Approach are usually derived by minerals appraisers, and by review of some conspicuous examples of the much too common misuse or abuse of the income approach in market value minerals appraisals. Example transaction analyses and sales comparison analyses are used to demonstrate the author?s methodology for adjusting units of resource in his transaction adjustment tables (see APPENDIX). The examples are used as the basis for discussion of ways to employ adjustments for operating economics and many other factors, while cautioning about the potential for double counting. The conclusions include a recommendation that minerals appraisers attempt to apply at least two of the three valuation approaches when appraising the market or fair value of development and operating stage mineral properties, the two being the sales comparison and income approaches.

Jan 1, 2011

By H. R. Butler, J. F. Church, A. T. MacGibbon

Introduction Inco is the major North American nickel producer. Initially based in Sudbury, Ontario, its past exploration activity was directed toward finding new nickel deposits. New nickel sulfide discoveries outside Sudbury have included Thompson, Manitoba; Shebandowan, Ontario; and Widgiemooltha in Western Australia as well as a host of nickel laterite deposits. The company is currently diversifying into other commodities, including gold. Inco's exploration department participated in uranium discoveries in Saskatchewan and chromite discoveries at Tiebaghi in New Caledonia. In addition, it found new gold deposits at Lupin, Northwest Territories; Crixas, Brazil; Hoyle Township, Ontario; and Casa Berardi in Quebec. Crixas and Casa Berardi are currently being evaluated by underground exploration. Figure 1 shows some Canadian Shield gold locations where Inco is or was an active participant. Base metal developments Base metal exploration in shield areas has been greatly eased by applying scientific studies. Archean nickel sulfide deposits have been found using komatiitic-flow models (Fardon, 1971). Volcanogenic massive sulfide model has been applied to copper-zinc deposits (Sangster and Scott, 1976). Such deposits were subsequently seen developing on the sea floor through black smokers (Spiess, MacDonald, and Atwater, 1980). Sedimentary processes were recognized early as important in ore formation, particularly in the southern hemisphere (King, 1976). And many ore deposits are now regarded as a simple part of the geological column (Stanton, 1960 and 1972). Petrographic work on alteration patterns in and around ore bodies was used to develop standard porphyry copper models (Lowell and Guilbert, 1970). Epithermal models for precious metals followed. Stratigraphic zonation patterns have been formulated for base metal deposits, including keel facies, ore facies, and cap or distal facies. Gold developments The work on base metal deposits naturally spilled over into precious metal exploration when the gold price was allowed to float on world money markets. Early work on elements associated with gold deposits, especially arsenic, tellurium, selenium, and mercury, pioneered more detailed geochemical work (Bagby and Berger, 1985; and Groves, Ho, and Houstoun, 1984). Geochemical patterns have been recognized around microfine gold deposits. And the study of gold precipitation patterns in modern geothermal systems has helped understand gold deposition. In the late 1960s and early 1970s, it was noticed that numerous Archean banded iron formations contained anomalous gold values. From this and other observations, the syngenetic exhalite gold model has developed. Gold deposits also occur along shears in some plutons such as the Belmoral mine in Quebec. This indicates the importance of epigenetic processes in ore formation. Shield ore settings Initial studies recognized that the major gold camps in the Canadian Shield were mostly in greenstone belts and found along "breaks," especially zones of faulting and sedimentation. Gill (1948) wrote, "Only recently, as a result of detailed mapping, has the importance of major schist zones such as the Larder Lake, Cadillac, Porcupine Creek, and Destor Breaks been recognized. These zones of persistent adjustment mark broad belts favorable for ore occurrence." The importance of shearing in ore location and regional greenstone stratigraphic position close to late sedimentary packages was clearly understood. And structural models have been further developed for some Canadian ore deposits (Hubert, Trudel, and Gelinas, 1984). In the Beardmore-Geraldton camp of northwest Ontario, the importance was soon recognized of fold noses in banded iron formation, as localizers for gold ore. This importance had also been recognized in Western Australia,

Jan 2, 1987

By S. Lolon

Spontaneous combustion in underground coal mines has become a serious problem particularly in the caved area (gob). Recent statistic has shown that approximately 17% of total 87 underground coal mine fires in the United States are attributed to spontaneous combustion (De Rosa, 2004). Spontaneous combustion results from a self-heating process in exothermic conditions. The accumulated heat, if not removed, is conducive to the rapid increase of temperature and may result in mine fires or explosions. It is well accepted that the interaction between oxygen and coal substances is the main cause for spontaneous combustion, while other factors such as pyrite, moisture, and bacteria play a secondary role to the self-heating of coal. Therefore, only coal oxidation is considered in this study. Coal oxidation occurs as coal comes into contact with air. This process involves complex phenomena in terms of heat transfer, chemical surface absorption, and energy balance related to inherent properties of coal (Wang et al., 2003). For simulation purpose, overall reactions can be simplified as suggested by Mitchell (1990): C + O2 CO2 + heat [65°- 94°C] (1) CO2 + C 2CO + heat [100°- 150°C] (2) Stoichiometric reactions (1) and (2) show that 2.66 grams of oxygen are required to oxidize 1.0 gram of carbon. Once the temperature exceeds 100°C, the reaction has little chance to stop. The crucial step in reducing spontaneous combustion risk is locating the ignition point of spontaneous combustion (hot spot). This information is useful in the effort of developing a preventive method effectively. In this study, this was conducted based on the best gathered information: ventilation surveys conducted in an existing longwall mine located in the western US; the laboratory experiments performed on a physical gob model; and the CFD models to investigate the flow behavior in the gob, the oxidation of coal, and heat transfer phenomena. The hot spot location is determined as a function of oxygen concentration and gob temperature. The critical values are the following: 5% (by volume) for oxygen and 100°C for gob temperature. CHARACTERISTICS OF GOB MATERIAL AND MODELS Permeability Concept Permeability is one of the key parameters in any study dealing with porous medium. This is determined by particle size and the ratio of void volume to the total volume (porosity) of porous medium. This relationship is known as the Carman-Kozeny equation (Scheidegger, 1957) and is given mathematically as [ ] where k* = theoretical specific permeability, m2 dm = the mean particle size, m n = porosity However, permeability tests with various particle sizes were carried out at the University of Utah?s ventilation model (Figure 1) to verify this relationship. These tests indicated a necessity to modify this theoretical relationship. A factor of 0.898 was obtained to make up the different between theoretical permeability and the experimental one. The modified version of (3) is given by: [ ] This equation is used to determine permeability of the simulated mine gob throughout the study. [ ] Mine Gob Material The gob is represented by zones filled with material of given size distribution. For physical measurements and CFD simulations, the material used were crushed rock and coal. Due to compaction, three different characteristics of gob material were used in the model: unconsolidated, semiconsolidated, and consolidated. In the real condition, the largest coal-rock particles are more likely to be located in the area behind the shields. This material is freshly broken and unconsolidated. The size of these broken particles is based on a study carried out by analyzing images taken from the area behind the shields in three coal mines in the United States (Pappas and Mark, 1993). The results have shown that the mean size of materials behind the shields is about 1.22 m. The permeability associated with this size was then obtained from (4) and permeability tests. This was 4.68 x10-7 m2. For semiconsolidated and consolidated zones, due to the lack of experimental data, these were determined through CFD simulations. These simulations were designed by assigning a permeability of 3.15 x 10-8 m2 for consolidated zone and 7.98 x 10-9 m2 to the other zone. The airflow pattern in the gob assigned with given permeabilities was expected to follow the experimental distribution (Brunner, 1985). The mean particle sizes for the semi-consolidated and consolidated zones were 0.02 and 0.006 m, respectively; smaller than those of the unconsolidated zone. Figure 2 shows the 3D view of permeability changes in the gob.

Jan 1, 2009

By K. Severin, B. Flanigan, P. Marion

“Plutonic-related” gold deposits in Interior and SW Alaska (Tintina Gold Belt) vary significantly in size, grade, vein/deposit morphology, depth of emplacement, distance from causative pluton and metal association. Metal associations such as Au-Bi and Au-As-(Sb-Hg) are a good empirical indicator of depth of emplacement and distance from causative pluton and have been used successfully in exploration. Results from a variety of analytical techniques also suggest a phenomenological cause for these metal associations, e.g. gold and bismuth have linked metallogenesis at high temperatures and thus are best correlated at deposits that are deep and/or close to causative intrusions.

Jan 1, 2000

By Thomas P. Kwiatkowski, Joginder S. Bhore, Christopher D. Orlandi, Jose Velez

Three case histories of successful TBM tunneling for New York City Water Tunnel No. 3 are presented. The tunnels, costing about one billion dollars total, are the 5-milelong, 18'-11" OD Brooklyn Tunnel; the 5-mile long, 23'-2" OD Queens Tunnel, and the9-mile long, 12'-4" OD Manhattan Tunnel. The three tunnels are the first major tunnels constructed in New York City rock utilizing the TBM method of construction. This paper describes and compares the three tunnel projects in terms of geology, construction methods, TBM’s, rock and groundwater behavior, rates of advance and other performance data, and challenges and solutions encountered during the projects.

Jan 1, 2007

By Richard B. Stein

Section 25 has been assembled to give the geological, mining, or metallurgical engineer an overview of some of the important downstream operations that typically follow mining activities. This subject is obviously too broad and complex to be covered in detail within this Handbook. However, the engineer will be interested to learn about the basic fundamentals, and especially how they might affect the economics of the total project from prospecting and mining through to metals recovery and marketing. In this way, it is hoped that the engineer will have a better overall appreciation for the technical and commercial prospects of a mining and metal-producing project.

Jan 1, 2008