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By Eddie Woods, Jon Hurt, Roger May, Paul Watson

The Channel Tunnel Rail Link (CTRL) will be Britain’s first major new railway for over a century—a high-speed line running for 109km (68 miles) between St. Pancras station in London and the Channel Tunnel. The new line has been under construction since October 1998 and the first phase will open in October 2003. The project includes22km of twin 7.15m ID TBM bored tunnels under London and the River Thames, and the 3km North Downs Tunnel, the first major NATM tunnel to be constructed in the United Kingdom since the collapse of the Heathrow Express Tunnels in 1994. This paper will discuss the design of these tunnels and describe the construction progress to date. The discussion will include details of segmental lining design, TBM specification, and sprayed concrete lining design.

Jan 1, 2003

By M. G. Bakker, D. D. Murphy, D. R. Spears

The US Bureau of Mines studied the mechanism of shear flocculation of silica with stearic acid. At pH 6 and 12, shear flocculation of silica was not observed with the addition of up to 4.5 x 10-4 M (5 lb/st) stearic acid. However, in the presence of 0.1 M NaCl at pH 6, shear-flocculation was observed at stearic acid concentrations = 10-4 M (22.5 lb/st). Adsorption of stearic acid on silica was studied using stearic acids spin-labeled with a doxyl group. The presence of the spin-labeling group did not greatly affect the shear flocculation properties of stearic acid. Adsorption of labeled stearic acid on silica was measured as a function of surfactant concentration with electron paramagnetic resonance (EPR) spectroscopy and gas chromatography (GC). The GC results indicated that the stearic acid was predominately adsorbed on the surface at concentrations above 10-4 M. From the EPR spectra, the formation of aggregates of stearic acid was apparent at concentrations of approximately 10-5 M (22.5 lb/st). The results are discussed in terms of a possible mechanism for shear flocculation.

Jan 1, 1995

By Peter M. Turcic

A Mine Safety and Health Administration (MSHA), National Institute for Occupational Safety and Health (NIOSH) and Bureau of Mines (BOM) interagency task group was established to assess the health and safety implications of the use of diesel-powered equipment in underground coal mines. The objective of the group was to conduct an assessment to identify areas of concern, to evaluate the adequacy of existing methods for addressing the identified concerns, and to recommend agency approaches for addressing inadequacies. The interagency group concluded its work in April 1986 and presented a report to the Assistant Secretary for Mine Safety and Health. The report included the conclusions reached by a group and recommendations for regulatory action by MSHA. This paper will present the methods and approaches used by the interagency task group and will discuss the findings, conclusions and recommendations of the group. The paper will attempt to meld together the technical and policy aspects of the issues involved with diesel equipment in coal mining.

Jan 1, 1987

By T. H. Combs, G. T. Lineberry

Increased productivity in the US underground coal industry has taxed pre-existing conveyor belt haulage systems. The usual remedies are costly and can disrupt production. A reduction in the belt feeder discharge rate on shuttle car sections results in more uniform loading and reduces spillage vulnerability. An investigation was made to determine the effect, if any, on shuttle car discharge time arising from lower feeder discharge rates. A five-section, underground mine is modeled, and belt spillage is introduced. The sectional feeder discharge rate is progressively lowered until spillage is precluded. At each level, the simulated spillage is measured and compared to the loss in face production. Methods for predicting the loss in face production from lower feeder discharge rates were investigated.

Jan 1, 1995

By Paul G. Schmidt

Exxon Minerals Co. was exploring for mineral deposits in Precambrian terranes of the US portion of the Lake Superior region in the late 1960s. Exploration drilling and other activities had been concentrated on massive sulfide prospects in northeastern Minnesota, but general exploration studies and competitor scouting were conducted in other areas of the region. These activities drew attention to Wisconsin in 1969 when it became apparent that Bear Creek Mining Co. had made a discovery near Ladysmith in the northwestern part of the state. Observation of their drill hole pattern suggested that a massive sulfide deposit, since named the Flambeau deposit (Schwenk, 1977), had been found. With this background, Exxon initiated an exploration program for Precambrian massive sulfide deposits in northern Wisconsin in 1970 (Figs. 1 and 2). Northern Wisconsin is extensively mantled by Pleistocene glacial drift and bedrock outcrop is sparse. Other than iron mines in the extensive iron formations along the Wisconsin-Michigan border and Jackson County, no significant mineral deposits were known in the Wisconsin portion of the Precambrian Shield until the discovery of the Flambeau deposit. Until the mid-1970s, the only specific published literature on the Wisconsin Precambrian consisted of old outcrop locations and descriptions in journals of the Wisconsin Geological and Natural History Survey (Chamberlain, 1882; [ ] Weidman, 1907; Hotchkiss, 1915) and the summary maps of Dutton and Bradley (1970).

Jan 1, 1991

By Simon D. Handelsman

Technical co-operation activities of the Department of Technical Co-operation for Development of the United Nations Secretariat have included the introduction of electronic data processing techniques in mineral sector projects for several years; computers have been provided to countries in Africa, Asia and Latin America. Advisory services are provided to interested developing countries at their request concerning applications for various uses in mineral sector activities. They include advice on appropriate hardware and software depending upon the requirements of the particular Government. The Department's activities in this area are described. The input from a Group of Experts on this subject convened by the United Nations, and their conclusions and recommendations, are also discussed.

Jan 1, 1986

By Jan Walaszczyk

The paper concerns the calculation of stresses and displacements in working area of room-and-pillar mining system of cooper ore mines. A three-dimensional rock mass model based on the finite element method has been developed. The complete strain-stress characteristic for pillars has been applied, but for the purpose of modeling the curve has been approximated by three segments of lines: - the first represents a behavior of pillar before a failure, -the second corresponds to a progressive pillar failure phase, - the third represents the part of the curve, where the increase of strains do not cause the stress changes, and it is called the residual strength. The criterion of model stability has been derived, which can be useful for predicting rockmass stability. The programs have been built, which allow to calculate stresses in bar elements, displacements in plate nodes, and estimate the stability of the model, which consists of plate elements and one-dimensional elements with a segment strain-stress characteristic. The programs were used to consider two different problems, which are connected with mining design and the exploitation systems.

Jan 1, 1992

By Judith A. Marks, Deane K. Smith, Jan M. Mutmansky, Maria Klimkiewicz

The mechanical mining of coal seams where roof, partings, and floor rock are extracted along with the coal often introduces large numbers of quartz particles into the mine atmosphere. This study concentrates on the quartz properties in situ and in the airborne dust to determine how they are released from the source rock and whether they are fractured by the mining machinery. Three mines using drum-type continuous miners from different geographic areas were sampled to provide a data base. The roof and floor rocks were primarily siltstones containing 5% to 25% quartz measured by the X-ray powder diffraction (XRPD) method. Much of the work presented here is based on the morphologies of the mineral grains determined by the scanning electron microscope (SEM). The study concentrated on particles of 0.2 to 10.0 µm and on particles containing > 75% Si. Mechanically-crushed quartz particles were also examined for comparison purposes. Particle shapes from the airborne samples suggested that fractured quartz particles were rare. Particle statistics also show that the average size of quartz particles in the airborne samples were similar to the average size of all particles. The conclusion is that very few quartz particles from the source rocks are fractured during mining due to their small initial size and the protection of the associated clays.

Jan 1, 1991

By J. H. Lalor

The Olympic Dam deposit was discovered in July 1975 with the intersection of 38 m (125 ft) of 1.05% copper in diamond drill hole RD 1. A further eight holes were drilled with only marginal encouragement to November 1976 when RD 10 cored 170 m (558 ft) at 2.12% copper and an economic discovery was confirmed. The discovery of Olympic Dam is an excellent example of the application of broad-scale scientifically based conceptual studies to area selection combined with the backing of an exploration management willing to support its exploration scientists in testing their ideas with stratigraphic drilling. It also illustrates the persistence required in mineral exploration. The project began in 1969-1972 with the development of a conceptual model for the formation of sediment-hosted copper deposits. This model suggested that the alteration of continental-type basaltic rocks could release copper into solution from which it could be concentrated in favorable stratigraphic positions. In mid-1972, this concept was applied to a review of the Proterozoic and Lower Paleozoic rocks in South Australia aimed at defining targets for stratigraphic copper deposits.

Jan 1, 1991

By J. L. González-Chávez, A. Ballester, M. L. Blázquez, F. González

In recent years, the bioleaching of sulfidic raw materials has been of great interest. However, the application of this biotechnology is now very limited for many different complex reasons. The mechanism of the chemical and electrochemical reactions taking part in the process is not well understood. The application of electrochemical techniques is useful in its elucidation. Among the common sulfides, galena has been studied very little with respect to its behavior during bioleaching. Therefore, the electrochemical evolution of massive electrodes of lead sulfide in the presence and absence of' a mixed culture of mesophilic microorganisms was investi¬gated by the application of potentiometry, anodic and ca¬thodic polarization and cyclic voltammetry. The agitation rate, the use of pH control and the composition of the nutrient mediums did not have any significant affects on the oxidation of galena. However, the temperature (25 'to 45 °C), the scan rate (4 to 100 mV/s) and the acid used to adjust the pH were significant variables that influenced sulfide oxidation. There¬fore, the peak (600 to 1,000 mV) corresponding to the oxida¬tion of sulfide ions from the mineral was only detected in the presence of a complexing anion of lead. In the presence of bacteria, the peaks corresponding to galena oxidation de¬creased and, at the same time, new peaks appeared both during the oxidation at -300 mV and during the reduction of the mineral surface at 150 and -300 mV. These signals were more important when the attack time increased. The rest potential of bioleached mineral increased with an increase in leaching time, which was related to the electrochemical transformation of the galena surface.

Jan 1, 2000

By G. A. Plakhin, A. V. Luganov, V. A. Luganov, G. V. Gorbatenko

In order to extract gold from the complex sulphur-arsenic bear­ing raw materials and to remove arsenic and sulphur from the process in an ecologically safe form we have studied oxidizing roasting of highly arsenic gold bearing concentrates with soda, leaching of cinders, processing of the obtained solution and extraction of gold from the cake. There were processed concen­trates containing from 5 to 28% of arsenic, 12-20% of sulphur in the form of pyrite and arsenopyrite. The content of gold in the concentrates was 4-75 git. The roasting temperature was changed in the range of 773-l 173K, the consumption of calcined soda was 75-200% of stoichiometric necessarily for bonding of arsenic and sulphur into the water soluble compounds, the dura­tion of the process was varied in the range of 10-120 minutes. Under roasting in optimal conditions up to 97% of arsenic and 95% of sulphur go into water soluble compounds. The out­put of cake is 65-70% of the concentrates. The extraction of gold from the cake is higher than from the raw concentrates. The technology has been tested on a pilot plant scale

Jan 1, 1996

By R. Y. Wan

Newmont Gold has advantageously used the capabilities of mineral oxidizing bacteria to develop a process for the pretreatment of low-grade sulfidic and carbonaceous-sulfidic refractory gold ores. The biooxidation process results in the oxidation of the sulfidic minerals with increased exposure of gold for subsequent gold recovery. The biooxidized carbonaceous-sulfidic ores cannot be heap leached with cyanide because of the preg-robbing characteristics of the carbonaceous matter in the ores. Therefore, an alternative heapleach process using ammonium thiosulfate was developed to extract gold from these preg-robbing bioaxidized ores. The ammonium thiosulfate leach process was successfully applied in both laboratory and pilot plant tests. Satisfactory test results were achieved, encouraging the continuation of process development.

Jan 1, 1997

By S. K. Das

A detailed strata-mechanics investigation and examination was carried out in the E2 Panel (ML-II/7) of the XVI Bottom coal seam, which is located in the Moonidih Colliery of B.C.C.L., Jharia coalfield, India. Above this panel, the XVI Top coal seam was previously worked out by a longwall panel. Based on intensive field study and on experiments in a number of longwall panels located within various Indian coal mines, the actual behavior of the coal roof strata was evaluated and new strata-mechanics concepts around the longwall panels were developed. These concepts resulted in new methodologies concerning the behavior of roof rocks, caving characteristics, etc. within longwall panels and in the area of strata mechanics. Based on these new strata-mechanics concepts, a very simple, but realistic, model was developed to determine the optimum capacity of the powered supports. This model considered the combined loads resulting from the detachment of strata and composite layer blocks from the face and, also, loads due to the deflection of strata and composite layers situated above the detached roof rockmass. This formula, along with the other related formulas by the author, prompted the determination of the optimum capacity requirement for the powered supports to be used in the XVI Bottom coal seam, located under the worked out area. This new concept in strata mechanics and capacity requirements of the powered supports in a longwall face may be an aid to Mining Engineers.

Jan 1, 1997

By A. W. Khair, S. S. Peng

Background The mine is located in Ebensburg, Cambria County, PA. Cambria County is located within the Allegheny Mountain section of the Appalachian Plateau Province. The geologic structures in the mine area included folds, faults, joints and cleats in the coal. These geologic structures seem to have genetic relationships with the Allegheny Front (lannacchione and Puglio, 1979). The mine's geologic structures have been influenced mainly by Ebensburg Anticline and Wilmore Syncline (Watson, 1979). Current longwall panels lay along the western limb of the Wilmore Syncline oriented south 30° west. Surface topographic relief in the area is less than 152 m (500 ft) and overburden thickness varies from 183 to 244 m (600 ft to 800 ft). The coal seam in the mine is part of the Lower Kittanning Formation. The thickness of the B-seam is the subject of discussion. It varies from 1.2 to 1.5 m (48 to 60 in.) and consists of two parts. The lower part is 1.1 to 1.2 m (44 to 48 in.) of soft coal and the remainder is bony coal. The coal seam dips slightly from 0° to 6° to the east-south direction. Panel entries are driven 61 m (200 ft) wide, consisting of three 5.5 m (18 ft) wide entries and two pillars 24.4 x 30.5 m (80 x 100 ft) centers. The mine has a history of cutter roof problems in the entries (Fig. 1) that has delayed the advance rate of entry development considerably and the cost of maintaining those entries is very high due to the requirement of very heavy artificial supports (Fig. 2). Due to excessive convergence in the headgate, installation of additional support and often resetting of steel beam, to provide enough clearance, in these entries imposed additional delay during the retreat of the longwall face, as the shearer cuts coal adjacent to the headgate and shield support at the headgate needs to advance under the steel beams (Fig. 3). Methodology Extensive underground observation indicated that roof cutter [ ]

Jan 1, 1992

By R. D. Hagni, R. T. Brandom

An ore microscopic study of the Boss-Bixby, Missouri, copper-iron deposit has shown that the mineralization formed as a simple sequence of oxides followed by cobaltian sulfides, copper-iron sulfides, and then oxides. The hypogene ore minerals found by this study are magnetite, hematite, ilmenite, rutile, chalcopyrite, bornite, covellite, cobaltian pyrite, carrollite, sphalerite, clausthalite, galena, electrum, scheelite, wolframite, and a Pb-Bi-Se-Te mineral. Textural evidence indicates that some of the early oxides were original constituents of the host syenites and oxidized during cooling. The remainder of the mineralization formed as breccia fillings and replacements. Subsequent partial oxidation has formed martite, covellite, rutile, and anatase.

Jan 1, 1987

By J. A. Herbst

Mineral liberation modeling can be traced back to the early work 0fA.M. Gaudin up through more recent population balance modeling by R.p. King, J.A. Herbst and G.T. Adel. A more micro-scopic look was taken at the University of Utah in the form of the J.E. Sepulveda and J.D. Miller Pargen model which permits the creation of an arbitrary shape, multiphase particle made up of discrete grains. Recent work on image analysis and tomographic analysis by J.D. Miller and C.L. Lin have laid the experimental ground work for model validation, but until now it hasn't been possible to include the necessary physics of the particle stressing process to allow the development of a 'ffirstprinciples"mode1 which does not presuppose a "mode” of liberation (e.g., random or by detachment). Recent developments in discrete grain breakage (DGB) modeling now make a generalized physics based model feasible. This paper describes current work that is being done to develop a physics based discrete grain liberation (DGL) model. Two-dimensional and three dimensional simulation results exploring the effects of particle size, phase properties and loading type are presented. Relationships between energy based liberation efficiency, degree of random liberation and material properties are identified.

Jan 1, 2005

By Normand Tassé

Reactive barriers, which consume oxygen, are prospective though unconventional alternatives to physical barriers for Acid Mine Drainage prevention. However, a reactive barrier implies a problem of duration. Pore gases were analysed in several wood waste piles in order to understand the factors which control wood degradation and help to determine the effective life span of such a cover. Long term efficiency seems to strongly depend on the degree of water saturation at the bottom of the pile, likely because the development of a microbial biomass in such an environment helps to keep the amounts of nutriments and readily metabolizable organic substrates at a high level, which in turn promotes oxygen consumption.

Jan 1, 2000

By Luis Dr. Sobral

In this study, the removal of zinc, cadmium and copper from an aqueous sulphate solution, derived from the biomass desorption process, was examined by using a reaction system with a three-dimensional high surface area electrode (RNiF). This reaction system was found to be extremely effective in reducing metal concentrations to the ppb range. The effect of cathode potential and flow rate were studied for three different nickel foam porosities. In addition, current- potential curves were recorded, at a rotating vitreous carbon electrode, to deter- mine the possibility of depositing the aforementioned metals separately.

Jan 1, 1998

By M. ]. [Mohkam

The paper describes the features of the problems encountered and the countermeasures taken for two different tunneling projects. Where, slurry shields were used to excavate, in soft heterogeneaous water-bearing grounds, tunnels passing at very low cover beneath existing foundations of H.T. electric pylons, underground structures and major utilities. In order to avoid any ground failure and/or damage to the existing structures, one option was ground treatement by grouting or freezing technics. However, it was judged that, based on previous experiences, excavation with slurry shield could be carried on securely using an appropriate slurry enriched with polymers and applying a well determined pressure at ground face. A three dimensionnal limiting equilibrium analysis model was used to determine proper confinement pressures. And, the appropriate slurry compositions were stabilished based on laboratory test results. The tunnels were excavated successfully, no ground failure was experienced, and the maximum settlement recorded (on pylons) didn't exceed 3 mm.

Jan 1, 1991

By Thomas Schultheis, William Heron, Paul Watson, Colin Warren

This paper describes the geology and geotechnics associated with construction of the Thames Tunnel, part of the UK’s Channel Tunnel Rail Link (CTRL). The 2.5km long twin tunnels run beneath the river Thames at depths of up to 40m and are currently under construction. They pass through varying geology comprising alluvium, terrace gravels and chalk with flints and are currently being bored using Herrenknecht mixshield slurry tunnel boring machines (TBM’s). This paper outlines the lithology and engineering properties of each geological formation and describes the geotechnical processes, potential hazards and difficulties experienced in the works. A summary is given into the extent of the investigative work in terms of route selection, tunnel design, TBM optimisation and further details are provided on the geotechnical aspects associated with the construction of the tunnel approach structures and the tunnels.

Jan 1, 2003