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By Otto Braach, Wolfgang Frietzsche, Erdogan Gürkan

The Westerschelde Tunnel is located in the south of the Netherlands and links the two parts of the Provinces of Zeeland, Zeeuws-Vlaanderen and Zuid-Beveland, which are separated by the Westerschelde. Road traf?c has up till now taken the detour via Belgium or crossed by ferry. This unsatisfactory transport link signifies major economic disadvantages above all for Zeeuws-Vlaanderen. The first fixed link for road traffic between the communities of Terneuzen and Borsele are to be created by means of the two 6.6 km long tunnel tubes down to 65 m below sea level.

Jan 1, 2003

In this paper, a number of novel hypotheses that provide a fresh perspective on the characterization of strata movements associated with longwall mining are developed by analyzing subsidence measurements with an influence- function-based computer program. With this influence-function technique, easily obtained surface displacements can be used to determine some of the complicated, expensive, and difficult to measure movements of the immediate roof strata in a longwall panel. The primary hypothesis developed by this analysis proposes the existence of an area of partial roof caving near the edge of a panel called the "edge effect." A second hypothesis, interrelated with the first, promotes the importance of the effect of gate-entry closure on the observed strata movements. Both the primary edge effect hypothesis and the secondary hypothesis concerning gate-entry closure are justified and quantified in an extensive analysis of surface subsidence that uses supporting information from related theories, design criteria and insitu measurements. Next, the edge effect and the gate closure hypotheses are extended further and used to provide an explanation of the complex subsidence interaction of adjacent longwall panels in what is termed a "redisturbed" effect. Finally, in the conclusions of this paper, the importance of accurately understanding these longwall strata movements for proper subsidence prediction or gate design is stressed.

Jan 1, 1986

By C. W. Matthews

Introduction Screening is defined as a mechanical process which separates particles on the basis of their size and their acceptance or rejection by a screening surface. The key element in this method of particle sizing is obviously the screening surface, the medium that contains the apertures for the passage of the undersize material. This surface must be strong enough to support the weight of the material being screened, flexible enough to yield to the vibrating force applied to it, yet light enough to provide a reasonable ratio of open area to attain a practical through- put. To balance all of these factors is difficult enough. The problem is compounded, however, because screening media are made in a great variety of types, shapes, sizes, and materials of

Jan 1, 1985

By W. Ghyoot, J. Boonstra, H. Dijkman, C. Buisman, M. Picavet

Paques and Umicore have demonstrated the feasibility of biological treatment of the highly complex Hoboken wastewaters in a1 m3/h pilot plant at Umicore Precious Metals, Hoboken, Belgium. In the first step arsenic was precipitated from copper smelter effluent as As2S3using biogenic produced H2S. Other metals such as copper, lead and cadmium were also removed as MeS to concentrations well below the discharge levels. Subsequently, sulfate and nitrate were removed to low concentrations (<300 mg/l and < 5 mg/l respectively) in high rate engineered bioreactors. Sulfide produced in the sulfate reduction process was recycled to step 1 for metals precipitation. Selenite/selenate was partly removed in the sulfide precipitation step, whereas the excess was biologically reduced and removed as selenium to concentrations <0.2 mg/l.

Jan 1, 2003

&apos;IM existing predictive methods were chosen for evaluation; an influence function (Bals Theory) and a profile function (hyperbolic). These ere applied to several field measured subsidence profiles over United States coal mines. The effect of homogeneous versus non-homogeneous overburden on surface subsidence is demonstrated and the utilization of Bals Theory as a subsidence predictive method for both types of overburden is examined. The major factor affecting subsidence profile characteristics is the migration of the inflection point toward the centerline of the longwall panel. A computer program was written to aid in the analysis.

Jan 1, 1982

23.1-SOURCE, POWER-SYSTEM ELEMENTS A. J. T HUM Basic considerations in providing power for mine production and collateral operations are: 1. Mining operations of any size normally use electric motors for driving all equipment except mobile service units. 2. The electricity for power may be purchased or self-generated, depending on the location, size and specific operating circumstances of the individual property. 3. The major elements of the power system will be the source, either an incoming transmission line from a utility in the case of purchased power or the power plant if self-generated. Energy for the power plant may be water, hydrocarbon fuels, waste heat or nuclear, which will govern the type of prime mover selected. 4. The electricity normally is generated in the form of alternating current and must be distributed to the points of usage. This usually requires a primary substation for transformation to suitable voltages and secondary substations at points of usage throughout the operations, The power is delivered from the primary to the secondary substations over transmission lines or cables, depending on distances, voltages and local conditions. 5. At the points of use, there will be starting and protective devices for each motor. In some instances, direct current will be needed and rectifiers of various types can be used to provide it. 6. The entire electrical system requires suitable switching and protective devices to prevent damage to the equipment in case of power failues or faults; also, in most cases, sufficient metering to establish the demand and amount of electrical energy consumed. 23.2-PURCHASED POWER A. J. THULI 1. Where public-utility or government-generated power is available, it usually is advantageous for the mine owner to purchase rather than generate. Purchased power generally will be cheaper and more reliable than operating a small generating plant except in some cases where waste heat is available as the source of energy and can be used to supply all or a portion of the power requirements. 2. If it is decided to purchase power, the owner usually must participate in the cost of constructing the connecting line from the closest existing utility line to his point of usage. If the connected load is less than 1,000 lip, it probably is best to let the utility provide the primary substation. For larger connected loads the owner can obtain a more favorable "primary voltage" rate if he provides the primary substation to receive the incoming power and transform it to the distributing and usage voltages. 3. The cost of purchased power usually is made up of a demand charge, deter¬mined by the maximum amount of power the customer takes during any 15-min period throughout a month, and a graduated energy charge for the kilowatt-hours consumed-that is, so much for the first block of energy based on the demand,

Jan 1, 1973

By Neil S. Fishman

Tabular uranium ore in the Grants uranium region, New Mexico, occurs as tabular layers of a urano-organic mixture suspended within host sandstones of the Morrison Formation. The intimate urano-organic association points to the organic material as the main ore control. Petrographic evidence indicates that the organic material was postdepositionally introduced into the host sandstone, probably as humic acids; however, the mechanism by which these acids precipitated from solution remains uncertain. A model, the cation scavenging model, is proposed in this paper to explain humic acid precipitation. The model, supported by evidence from regional alteration studies of the host sandstones, proposes that cations responsible for humic acid precipitation were scavenged from framework grains which altered during passage of the humic-rich fluids through the host sandstone. This process, coupled with the affinity of organic molecules for each other, caused flocculation of humic acids into tabular zones. The precipitated humic substances then continued to concentrate uranium to form the orebodies. The cation scavenging model requires only one solution, the humic-bearing solution, in the precipitation process. All cations necessary for humic acid precipitation originated in the host sandstones. This model contrasts with a previously proposed model--the brine interface or two solution hypothesis--in which it was proposed that a cation-rich brine introduced into the host sandstones provided the cations necessary for humic acid precipitation. The brine hypothesis has several drawbacks, one of which is unrealistic hydrologic reconstructions necessary to accommodate mineralization at various stratigraphic horizons in the Morrison Formation. Moreover, no mineralogic evidence exists to suggest a brine occupied the host sandstones at the time of mineralization. The proposed cation scavenging model for humic acid precipitation not only readily accounts for humic acid precipitation, but also is consistent with geologic observations and regional alteration studies.

Jan 1, 2013

By S. S. Klima, H. Jiang, T. W. Beck, Y. Zheng

Researchers at the National Institute for Occupational Safety and Health (NIOSH) performed a series of lab tests to evaluate the respirable dust removal capacity of an industrial air-cleaning fan. Limestone and coal dust were tested separately in NIOSH’s full-scale drill table simulator at the Pittsburgh Mining Research Division (PMRD). Gravimetric samplers with Dorr-Oliver Cyclones and 37-mm filters were used at two upstream and four downstream locations inside and outside of the drill shroud chamber. There were six tests performed for both the limestone and coal dust experiments. In the limestone tests, an average respirable dust concentration of 98.86 mg/m3 was achieved upstream of the air-cleaning fan. The filter results show that the averaged respirable limestone dust reductions were 7.84%, 8.81%, 10.94%, and 18.02% at the four sampling locations downstream of the fan. In the coal tests, upstream samplers achieved an average of 129.03 mg/m3 of respirable coal dust. The averaged dust reductions were 9.54%, 9.83%, 18.54%, and 19.21% at the four downstream sampling points. The results indicate limited cost benefits of using this technology because of the relatively low dust reductions determined from this laboratory study.

Feb 1, 2023

By F. D. Wicks

This paper summarizes the direct operating cash costs for the Barrick Mercur open pit gold mine. A comprehensive, detailed system of cost management has been in effect for the life of the Mercur operation. This system provides the basic data for operations control and is the basis for drafting budgets as well as analyzing impact of change on operations costs. The ore body is complex geologically and metallurgically, requiring operators to pay close attention to mining and processing costs. The cost history provides data which enables analysis of changes in production levels, aging of the mine production fleet, and the impact of specific cost changes through time.

Jan 1, 1993

By Lok W. Home

INTRODUCTION Today, raise drilling (boring) has become the stan¬dard method of raising throughout the Western world. It is estimated that the majority of raise footage com¬pleted in 1977 was accomplished by the raise drilling method. Extensive replacement of the drill and shoot system by mechanized raise drilling has occurred be¬cause users have recognized one or more of the follow¬ing advantages. In a direct cost per meter comparison, mechanized raise drilling is economically more attractive than drilling and shooting. Mechanized raise drilling offers improved personnel safety over the drilling and shooting method. Mechanized raise drilling is a faster and more predictable method for excavation than is drilling and shooting. The raise cost per unit of length becomes less as the raise length increases, offering greater flexibility in the overall design of mines. Mechanized raise drilling provides a substantial reduction in labor requirements. 6) Mechanized raise drilling improves the working environment. 7) Mechanized raise drilling improves the rock in¬tegrity of round, unblasted raises. Increasing acceptance of the raise drilling technique is enhanced by continuing equipment development. Today, a wide range of machines and capabilities is available, machine drive systems have been improved, reliability has been increased, and cutter technology is being improved quite rapidly. Table 1 lists the four major manufacturers of raise drilling machines, cutters, and reamers, together with the approximate number of machines that each company had in operation at the end of 1977. Although Reed and Smith are major suppliers of reamers and cutters, they do not manufacture the drilling machines. Four or five other relatively minor suppliers have built machines, reamers, and cutters for raise drilling, but they did not have a substantial num¬ber of machines in the field at the end of 1977. MACHINES FOR MECHANIZED RAISE DRILLING There are three principal arrangements for making machine-bored raises. They include the use of standard raise drills, reversible raise drills, and blind-hole or box¬hole raise drills. Standard Raise Drills The standard raise drilling machine is set up on one mine level or on the surface, and a pilot hole is drilled from that level or surface to a level below. When the pilot hole has been drilled, the raise then is reamed back from the lower level to the upper level or the surface. This arrangement is illustrated in Fig. 1. Reversible Raise Drills The reversible raise drilling machine is set up on a lower level of the mine, and a pilot hole is drilled up¬ward to a higher level. The raise then is reamed back from the upper level to the lower level. This arrange¬ment is illustrated in Fig. 2. The machines used for this type of raise drilling normally are capable of being used as standard raise drills. Blind-Hole or Boxhole Raise Drills The blind-hole or boxhole raise drilling machine is set up on a lower level of the mine, and a full diameter raise is bored to a higher level without the use of a pilot hole. This type of machine is illustrated in Fig. 3. Drill Recommendations If access to upper and lower mine levels is equal, the standard raise drill should be used. The complexity of the equipment and associated handling procedures for boxhole drilling far outweigh any mechanical advantage or reduction in the number of operations, provided that access to an upper level is available. If there is good access to a lower level but only limited access to an upper level, the use of a reversible raise drill should be considered. If there is no access to an upper level, a blind-hole or boxhole raise drill is the only practical mechanized system. MACHINE SELECTION There are six major considerations in selecting a machine for raise drilling. These include operating range, cutter loading, machine structure and main¬tenance, drill string configuration, drive system, and automated controls. Operating Range As shown in Table 2 and Figs. 4 through 6, raise drilling machines are available for a wide range of hole sizes. Standard raise drill ratings range from raises of 0.9 m (3 ft) diam and 120 m (400 ft) length up to raises of 3.5 m (12 ft) diam and 900 m (3000 ft) length. Boxhole raise drilling machines are available for raises ranging from 0.9 m (3 ft) to 2 m (6 ft) diam with lengths up to 90 m (300 ft). Table 2 lists, among other criteria, the torque and thrust of typical machines; torque and thrust are the main criteria for analyzing the capacity of a machine. The raise sizes shown in Table 2 assume a condition of medium hard to hard rock formations and optimum cutter loading. The recommended raise size for a given machine can be exceeded when raising softer rock formations or when the operator is willing to accept a lower level of performance; the performance is related directly to the 1093

Jan 1, 1982

By A. A. El-Midany, R. M. Farag, A. M. Salem, S. E. El-Mofty

Bentonite is one of the main players in the stability of drilling mud. Its particle size and particle size distribution significantly affect drilling mud’s rheological properties. Although the Specifications for Drilling Fluids Materials report on Oil Companies Material Association (OCMA)-grade bentonite states that the API recommended powder having 2.5 percent mass fraction as the maximum value of residue of diameter greater than 75 μm, there is no other information on the specific size distribution for API bentonite. It was found that API bentonite has a specific size distribution with specific mixing weights. It is important to investigate why that mixture represents the optimum properties of drilling mud and how each individual size fraction has a specific function in the mixture. To clarify the effect of individual size as well as the collective effect of the size distribution, API bentonite was classified into different size fractions, with each tested separately for controlling properties such as filtration loss, plastic viscosity, gel strength, cake thickness and packing density.

The deformation, failure, and filling characteristics of a caving roof in the initial and normal mining stages of a pitching oblique longwall mining area are analyzed using large-scale threedimensional physical-similitude experiments and numerical calculations to study the characteristics of roof fracture and migration in a steeply dipping seam. The results show that the roof fracture development has evident sequential and spatial characteristics. Among them, immediate roof breaking in different parts of the mining area shows difference in time and space. The failure sequence of the immediate roof in different areas changes with the mining; unique regional stability evolution characteristics are observed in the suspended immediate roof simultaneously, resulting in its significant regional stability on the goaf filling.

Jan 7, 2020

By T. L. Conley, J. J. Rozek

The $2 billion (A$) Melbourne City Link Project is one of the largest and most important metropolitan road developments ever undertaken in Australia. The project involves two three-lane vehicular tunnels totaling 5 km, constructed as deep as 65 m underground. The 3.4 km Burnley tunnel is one of the world&apos;s longest three-lane tunnels. The project is being delivered under a DBOOT [design-build-own-operate-transfer] process and all design and construction is performed to ISO 9000 standards. Tunnel excavation began in May 1996, and the tunnel will open to traffic in 1999. This paper focuses on the range of construction techniques utilized during construction.

Jan 1, 1999

By W. G. Pariseau

A study of coal pillar strength was done at the Beehive Mine during a three year period, 1974?1977, in a cooperative effort involving the University of Utah, RE/SPEC, Inc., and the American Coal Company (Pariseau et al, 1977). The Beehive Mine is located in the Wasatch Plateau coal field in central Utah near Orangeville, Utah, where mines are developed from outcrops between steep canyon walls with topographic relief of a kilometer or so (3,600 ft). Coal is found in Cretaceous sediments that dip gently to the west. Detailed geology of the Wasatch Plateau is described by Doelling (1972). Mining was done in the Blind Canyon seam. An earlier Deseret Mine worked the Hiawatha seam that is lower in the stratigraphic column by about 36 m (120 ft). Mining progress and ownership changes occurred in time with mine mergers and name changes eventually to the collective Des-Bee-Dove label. At the Beehive Mine, depth varied with topography but was approximately 360 m (1200 ft) on average; seam thickness varied from 1.5 to 6 m (5 to 20 ft) and usually required two passes of the miner. The mine was eventually closed and finally reclaimed in 2003. Semborski and Oakley (2006) present a brief history of the mine and describe the reclamation work in some detail. Figure 1 shows the surface topography in the vicinity of the mine that is in the center of the figure.

Feb 23, 2014

By U. Thorley

Management of mine and tailings reclamation activities by surface mining oil sands operations in Alberta, Canada is experiencing increased national and international attention. Of particular concern is the ability of existing mines to execute and fund reclamation activities. Concern stems from a lack of demonstrated tailings reclamation technologies, perceptions of a poor track-record of reclamation activity by industry, and a lack of transparency with respect to the potential cost of reclamation activities relative to the monies secured in Alberta?s Environmental Protection Security Fund (EPSF). Limited information is publicly available regarding reclamation costs and technologies. Available data typically comes from disparate sources. This paper examines the expected costs of oil sands reclamation activities through a study of corporate Asset Retirement Obligation (ARO) liabilities, the Province of Alberta?sEPSF, and published data relating to reclamation costs.Issues relating to current liability funding are introduced.

Jan 1, 2011

By Martin Herenknecht, Michael Knabe, Ulrich Rehm

In Switzerland at present, the longest railway tunnels in the world, the Gotthard(57 km) and the Loetschberg base tunnel (34km) are under construction. For thischallenge six high-tech HERRENKNECHT Hard Rock Tunnel Boring Machines (TBM)are applied, which have to excavate approx. 80 km at the Gotthard and 20 km at the Loetschberg Tunnels. The machines being used are of a single Gripper-TBM type, which are equipped with the latest rock support techniques, in order to optimize the quality of the working conditions for the personnel which have direct impact on the quality of the tunnels. The different requirements of the projects based on different speci?cations within the tender documents led to completely different TBM concepts which will be reviewed in detail in this paper.

Jan 1, 2003

By R. J. Roman

The results of column leaching tests on 3 different mixed oxide/sulfide ores from a Chilean deposit are presented. The 3 samples contained different ratios of oxide copper minerals to chalcocite and chalcopyrite. The results of the column leach tests are interpreted in light of the shrinking core model for coarse particle leaching. The copper recovery from the oxide minerals and the sulfide minerals each conforms to the shrinking core model with the total recovery equal to the weighted average of the individual minerals. The use of column test results to predict field heap leaching results using the multi-mineral shrinking core model is discussed.

Jan 1, 1993

By Marshall D. Himes, Erich U. Petersen

The Sheep Creek deposit near White Sulfur Springs, Montana, is a middle Proterozoic stratabound and strataform sediment- hosted massive sulfide containing 4.5 million tonnes (5.0 million tons) averaging 2.5% copper, and 0.1% cobalt in the upper sulfide zone (USZ) and 1.8 million tonnes (2.0 million tons) averaging 6% copper in the lower sulfide zone (LSZ). Mineralization is hosted in lower Newland shales and debris flow conglomerates in the graben controlled Helena Embayment of the Belt Basin. USZ mineralization is characteristically high in Cu, Co, Ni, Ba, As, Pb, and Ag. Mineralogically it consists of barite, pyrite, chalcopyrite, and tennantite with minor amounts of marcasite and various cobalt minerals. By contrast, the LSZ is higher in Cu, Ni, and Au and lower in Co, As, Pb, and Ag. Mineralogy of the LSZ consists of dolomite, pyrite, and chalcopyrite. In both zones significant amounts of cobalt, nickel, arsenic and copper are incorporated in pyrite rims. Tennantite controls the abundance of numerous trace elements in the ores. Fluid incluison data from hydrothermal USZ barite suggests that mineralization took place at temperatures in excess of 250°C, under relatively oxidizing conditions (f02 = 10-32+1) from moderately saline (1.1-3.5m), metal rich brines. The absence of barite in the LSZ suggests mineralization under more reduced conditions (f02 = 10.38+2). Mineralization was initiated following basin subsidence in excess of 400m. Contemporaneous with movement along a growth fault(s) was upward migration of hot metal-bearing fluids which permeated the loosely consolidated sediments and may have vented on the sea floor. The differences in the two zones may be explained by the effects of variations in local basin morphology and solution chemistry.

Jan 1, 1990

By R. B. Krog

Airflow patterns in longwall bleeder systems are affected by gob permeability and porosity and the condition of the gateroad entries after mining. As longwall panels are mined, areas of the caved zone and portions of the remaining gateroad entries become inaccessible, making direct ventilation measurement impossible. Mine operators are left to estimate direction and amount of airflow in the gob and the surrounding gateroads. The most readily available locations are where air enters the worked-out area, approved measurement point locations (MPLs) and/or evaluation points such as bleeder evaluation points, intake evaluation points, and the outer bleeder entry. Ventilation models (network or Computational Fluid Dynamics, CFD) can model the gob and the surrounding bleeder system but calibrating these models is difficult without field data. NIOSH installed a tube sampling system ahead of a longwall face and, as the face retreated, released a slug of tracer gas (SF6) to determine transportation times and flow rates in the inaccessible gateroads. The data was used to calibrate both network and CFD ventilation models for a longwall panel. Both model types were used to predict the airflow patterns in the gob and to determine the airflow rate from the longwall tailgate corner back to the bleeders.

Jan 1, 2011

By J. Herbst, C. C. Harris, G. Poling

The modern flotation machine is the result of decades of adaptation to a changing environment. In response to falling ore grades, and rising demands, tonnages, and costs, attempts are now underway to expand machine capacity by about an order of magnitude, while at the same time maintaining metallurgical performance and if possible reducing power requirements per unit throughput. Empiricism and rule-of-thumb have guided flotation machine design and scale-up, and a current need is for the development of a fundamental understanding of the subject. Design features of current and some obsolete machines are discussed in an attempt to outline those principles of flotation machine design which are known, and to delineate topics needing investigation. Attempts are made to distinguish between essential machine features required by the physics of the process, those features resulting from speculative theories on the flotation mechanisms, and features which are essentially styling variations. Topics discussed include: flotation mechanisms; tank and impeller/ stator design and dimensions; impeller speed; aeration; power consumption; particle suspension and dispersion; capacity; correlation of design parameters and operating variables; scale-up and scale- down; materials flow; problems in machine design. Design details and operating data for several current machine families are provided in Appendices.

Jan 1, 1976