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By P. G. Shewmon

Radioactive MgZA has been used to study the rate of self-diffusion in oriented single crystals of magnesium in the temperature range 468O to 635OC. The diffusion coefficients parallel and perpendicular to the c-axis are: Dl, = 1.0 exp (—32,200IRT) cm2 per sec and Dl = 1.5 exp (—32,500IR T) cm Qer sec. The ratio Dl/Dll was found to vary from 1.13 at 468 to 1.24 at 575 C. Assuming a vacancy mechanism, an explanation of this aniso-tropy of diffusion follows from a consideration of the difference in the saddle points for diffusion in and out of the basal plane. RECENT discovery of radioactive Mg2"'-' has made possible the study of self-diffusion in magnesium. The experimental procedure and the results of a study of diffusion in polycrystalline magnesium have been described in an earlier paper.V he present work is an application of the same techniques to the study of self-diffusion in oriented single crystals of magnesium. In the general diffusion problem the diffusion coefficient is a second order tensor relating the two vectors, the diffusion flux, and the concentration gradient. In a hexagonal lattice, such as magnesium, the complete determination of the diffusion coefficient D as a function of direction in the lattice requires a knowledge of D,, and D,, i.e., the diffusion coefficients parallel and perpendicular to the c-axis, respectively. It can be proven quite generally that in a hexagonal lattice D is independent of direction in the basal plane, and that out of the basal plane it varies with 0, the angle between the c-axis and the direction of diffusion, according to the equation D(B) = D,,cos2B + D,sin2B. [I] The proof of Eq. 1 depends only upon the symmetry elements of the hexagonal lattice and upon the transformation properties of a second order tensor." Therefore, Eq. 1 holds for any mechanism of diffusion and any c/a ratio. Experimental Procedure The experimental procedure used with polycrystalline specimens can be briefly outlined as follows. Radioactive Mg" was produced by bombarding a NaCl crystal with 350 mev protons and was chemically separated from the target as MgO. The Mg" was then vapor deposited on a specially cleaned magnesium specimen by heating the MgO on a tantalum ribbon in a vacuum. During the diffusion treatment, oxidation and vapor loss of the radioactive material were minimized by annealing the samples in pairs with the active faces in contact, each pair being inside a magnesium container, which was in turn surrounded by an argon atmosphere in a sealed Pyrex tube. The distance-activity profiles were obtained by measuring the activity of thin sections cut parallel to the original interface with a lathe. The only technique which was peculiar to this work was the preparation and orientation of the single crystal specimens. The single crystals used in this work were grown by E. C. Burke of the Dow Chemical Co., using a modified Bridgman method, in which the furnace and specimen were stationary while the temperature gradient moved.' In growing these crystals the starting material was distilled magnesium, the crucibles were machined from Acheson electrode graphite, and the furnace atmosphere was tank argon. The crystals were grown from sublimed magnesium with the following analysis: 0.0002 pct Al, 0.0017 pct Fe, 0.0009 pct Mn, 0.0001 pct Ni, 0.0006 pct Pb, and less than 0.01 pct Ca, 0.0001 pct Cu, 0.001 pct Si, 0.001 pct Sn, and 0.02 pct Zn. The two crystals used were roughly lh in. diam and eight in. long. The c-axis made angles of about 7" and 78", respectively, with the specimen axes. If the values of D obtained by the use of these two crystals are taken equal to D,, and D,, respectively, the error introduced by this assumption is less than 1 pct. This can be shown by combining Eq. 1, the identity sin% + cos'8 = 1, and the experimental fact that DJDn in magnesium was always less than 1.25.

Jan 1, 1957

By H. H. Rachford, D. W. Peaceman

A system of partial differential equations describing miscible displacement of fluids in porous media is derived The system takes into account the influence of gravity, the spatial distribution of permeability, diffusion, and fluid viscosities and densities. A numerical procedure for approximating solutions to the differential systems has been tested for a horizontal two-dimensional geometry. In end-to-end displacements of oil with less-viscous solvents, the numerical solutions exhibited fingering qualitatively similar to that observed in laboratory models. Small random spatial variations in permeability about the mean value are sufficient to initiate fingering. Quantitative comparisons of computed results with laboratory data show good agreement. INTRODUCTION Miscible flooding of oil by solvent is receiving increasing consideration for field use.1-4 Unfortunately, such floods potentially present severe problems in loss of recovery through the by-passing of oil by expensive solvent. Consequently, their economic evaluation requires sound techniques for predicting recovery. The purposes of this work are to present a finite-difference method for calculating the multidimensional displacement of oil by solvent and to investigate the validity of the method by comparing results of calculations with data from displacements in laboratory models.5 The formulation of the method to simulate the model experiments treats a case of limited scope in the description of solvent flooding in the reservoir. The model experiments were carried out with fluids that were assumed to form an incompressible, ideal, two-component system with constant diffusivity. Establishing the validity of the method even in its present form provides a major step toward the goal of quantitatively evaluating individual solvent flooding projects. First, it demonstrates the fea- sibility of calculating the course of displacements which are dominated by an inherent macroscopic instability, i.e., viscous fingering. In addition, the method provides almost the only practical means of examining the effect of the size and extent of reservoir inhomogeneities on the development and propagation of the fingers, taking into account the important influences of diffusion and gravitational segregation. It might be inferred that such studies cannot yield results of practical value because in displacements dominated by macroscopic instability the pattern of finger development and the resulting performance should depend critically on small variations in the geometric distribution of reservoir inhomogeneities. The present method offers the capability inherent in computational techniques of predicting performance reproducibly with any arbitrary distribution of reservoir properties and, as such, provides a means of evaluating the sensitivity of behavior to uncertainties in reservoir definition and, thus, assessing the reliability of prediction of performance. THE PHYSICAL PROBLEM DATA USED FOR QUANTITATIVE TESTS OF CALCULATIONS In this work, a calculation for treating the miscible-displacement process is tested by comparing calculated results with experimental data. The experiments chosen for comparison have been described in detail,5 and the quantitative features are summarized in a later section. Briefly, oil was flooded by solvent of equal density from a thin rectangular channel in Lucite packed with uniform Ottawa sand. Under these conditions, two-dimensional geometry is considered adequate to represent the process. Inasmuch as the present work is concerned with testing of the method by comparison with specific two-dimensional data, the system of equations presented in the succeeding section will be oriented to defining the physical system specifically. THE DIFFERENTIAL EQUATIONS Suppose x, y to be a Cartesian co-ordinate system and define h(x, y) to be the height of a point above a horizontal reference plane. It will be assumed

By Marshal Scherba

Coal seams approximately 7 feet, 9 feet and 20 feet thick at depths of 250, 600 and 1,000 feet respectively were detected using high resolution seismic reflection techniques. Investigation of seismic profiles indicates that good data are required to delineate faulting with only 20 feet of throw but that faulting with 50 feet of vertical displacement can be detected with poor data. Data acquired from dynamite charges fired in water saturated media were clearly superior to that acquired using charges dry tamped in 10 and 20 foot holes.

Jan 1, 1977

By M. Suzuki, M. Dobashi, M. Kahata, T. Yoshida

Almost 30% of steel in Japan is produced by electric arc furnace (EAF) treatment of iron scrap. EAF dust includes approximately 20 wt % of Zn and 3- 5 wt % of CI and is treated by the pyrometallurgical processes to recover Zn as Zn oxide. Direct hydrometallurgical processing is one of the most effective methods to recover high purity Zn. In this case, CI in the EAF dust is dissolved in the liquid phase by leaching, and the CI anion in electrolyte attacks anodes which are commonly made of a lead base alloy. Several processes have been proposed to remove CI anions from acidic sulfate solution. In this study, an electrolytic process was examined to eliminate CI anions from Zn sulfate electrolyte. From our study it can be said that the elimination rate of CI anion depends on the anode material ( i.e., the elimination rate is Pb-Ag alloy == Pb > DSE== Pt). In industrial Zn electrowinning process, the electrolyte contains Mn, which means the influence of Mn should be considered in the elimination of Cl. Mn dioxide deposition on an anode plate reduces the efficiency of CI removal. A periodical reverse current electrolytic system was examined to prevent this efficiency decrease, and deposited Mn dioxide could be removed very rapidly when the current is reversed. More than 95% of CI anion could be removed by this method in a shorter period than direct current method.

Jan 1, 1997

By Huimin Lu, Qiang Li, Jingbo Xu

"The smelting reduction of V-Ti bearing beach placer by combined rotary hearth furnace and direct current arc furnace was studied in laboratory. It takes the aid of back propagation (BP) neural network theory to build the nonlinear mapping relations between the crucial process variables such as content of carbon, temperature and time and the degree of reduction. Then by the integrating BP neural network and genetic algorithm (GA), the optimized process parameters for the high degree of reduction were searched. The comparisons between experiment results and neural network simulation results show that GA-based on BP method can predict the degree of reduction with higher prediction accuracy. Calculations show that the integrated energy consumption of new technology is 580kgce/tHM, less than the current existing blast furnace.IntroductionThese V-Ti bearing beach placers (VTBBP) are secondary Fe-rich minerals formed by rivers, ocean waves, ocean tides and ocean currents on beach zones, their useful minerals are V-Ti magnetite ores. On Asia Pacific zone, such as Japan, China, Philippines, Indonesia, Australia and New Zealand, the VTBBP have large reserves and wide distribution. But so far, the VTBBP are not still comprehensively utilized. Therefore, in this paper, a combined rotary hearth furnace technology and arc furnace smelting method is studied for comprehensive utilization of the VTBBP. The main objective of this paper is to find optimum operation conditions for the production ofV-bearing iron and titania-rich slag from the VTBBP by means of the laboratory testing.Recently, neural network (NN) expected to be able to provide an effective tool because of its advantages, which describe nonlinear mapping relations. With the characteristics of strong selflearning, self-organization, robust error toleration and accurate nonlinear relation approximation, artificial neural network can be applied to nonlinear process modeling based on sufficient training. Back-propagation (BP) training algorithm is probably the frequently used one in practical application. Genetic algorithm has parallel search strategy and global optimization characteristics, which makes the trained neural network being higher classification accuracy and faster convergence speed. So it is necessary to combine neural network and genetic algorithm. The nonlinear relationship between input and output presented by NN and the global optimal function of GA are abroad applied in the engineering and scientific research [1, 2]. So these methods supply an efficient path to solve the above problems. At present, it is common to study the optimization of process parameters by orthogonal experimental design, the method combining neural network and genetic algorithm is a novel and better method than orthogonal experimental design. Tills study organized the above advantages to optimize the process parameters for comprehensive utilization of the VTBBP."

Jan 1, 2012

By Richard H. De Voto

The McDonald gold project and two satellite gold deposits near Lincoln, MT were discovered in the early 1990s. They contain at least 307.9 t (9.9 million oz) of gold and 933 t (30 million oz)of silver. The McDonald gold deposit alone contains 223.9 t (7.2 million oz) of gold reserves that can be open-pit mined and processed by cyanide heap leaching at a projected cash operating cost of $6.10/g ($190/oz). The deposit is predominantly oxidized with no chance of acid production. It can be mined, operated and reclaimed with minimal permanent environmental disturbance other than the creation of an open-pit filled with a fresh-water lake that would support trout.

Jan 1, 2000

By E Heath, F McDermott, S Turner, P van Calsteren

U-Th isotope studies of recent volcanic rocks may be used to evaluate the depths and rates of melt generation beneath midocean ridges and ocean islands. Island arc rocks exhibit a similar range in Th isotopes to that seen in both MORB and om, but while those with high (230Th/232Th) tend to have excess 238U, many of those with low (230Th/232Th) are in isotope equilibrium. The excess 238U is attributed to the preferential mobilisation of U in hydrous fluids from the subducted slab within the last 100 000 years, whereas the low Th isotope ratios in the higher-K arcs are primarily due to the introduction of subducted sediment. Preliminary results from mineral separates from lavas on Soufriere on the island of St. Vincent indicate that some of the minerals crystallised up to 50 000 years prior to eruption.

Jan 1, 1995

By Dinesh Agrawal

Microwave energy has been in use for variety of applications for over 50 years. These applications include communication, food processing, wood drying, rubber vulcanization, medical therapy, polymers, etc. In the last two decades microwave heating has been also applied very effectively and efficiently to heat and sinter ceramic materials. Microwave heating is recognized for its various advantages, such as: time and energy saving, very rapid heating rates, considerably reduced processing cycle time and temperature, fine microstructures and improved mechanical properties, better product performance, etc. The most recent application of microwaves has been in the field of metallic materials for sintering, brazing/joining and melting. Several common steel compositions, pure metals and refractory metals have been sintered in microwaves to nearly full density with improved mechanical properties. Many commercial powder-metal components of various alloy compositions including iron and steel, copper, aluminum, nickel, Mo, Co, Ti, W, Sn, etc., and their alloys have also been sintered in microwaves producing better properties than their conventional counterparts by using a 2.45 GHz multimode microwave system. This work has been further extended to join and braze bulk metal pieces, especially super alloy based turbine blades. Further, in a specially designed microwave cavity, even the bulk metals can be made to couple with the microwave field and melted. The implications of these findings are obvious in the field of powder metal technology.

Jan 1, 2006

By Sue Xue, Carl C. Nesbitt

A project was completed which investigated the efficacy of recycling lead or lead monoxide from various fire assay wastes including crucibles, cupels and slag. The scope of the project was to determine optimal hydrometallurgical parameters so that direct separation and recovery of lead salts was economically feasible. A process was developed from the study which could use either acetic acid or nitric acid as a leachant, followed by several precipitation processes which could directly recover litharge (PbO) or other lead salts, such as lead carbonate or lead sulfate. The economics of the process is discussed. Analytical equipment such as the atomic absorption spectrophotometer and x-ray diffractometer supplied much of the information required for the study. However some novel analytical approaches using these instruments had to be developed to help in the determination of leaching kinetics and process quality control which are discussed.

Jan 1, 1999

By K. S. Krishnam, A. G. Guy

VOLUME 6 of the Transactions of the Baikov Institute of Metallurgy, Moscow, is devoted to the subject of "the experimental and theoretical study of the physical characteristics of dilute solid solutions,11 and summarizes work that has been done largely in the years 1958-9. In view of the attention that Soviet investigators have given to this subject, it seemed useful to carry out an independent experimental investigation in an effort to judge the scientific basis and practical significance of this field of study. The present note is a preliminary report of this investigation. The first property studied by the Soviet group was X-ray spectra of solid-solution alloys.' An anomaly observed at low concentrations (--0.05 at. pct) of the alloying element led to the theory that each impurity atom in a transition-metal base alloy is the center of a "block" of affected atoms with a radius of about 10"7 cm. This theory was further developed in a later paper.2 By this time similar anomalies had been found in diffusion coefficients3 and in thermal expansion.4 The entire development up to 1959 was reviewed in a comprehensive paper, and further theoretical ideas were also published at this time. Finally, the volume mentioned above was published in 19607 giving new experimental data on anomalies in optical properties and Hall constant, and a new theoretical treatment also appeared.' Although western scientists have done both theoretical work, summarized recently by Friedel,9 and considerable experimental work on dilute solid solutions, there is little support for the marked anomalies reported in the Soviet papers. Of the physical properties studied by the Soviet investigators, thermal expansion was chosen for the present investigation because of the relative ease of obtaining the necessary precision of measurement. A Leitz dilatometer was used for this purpose, and a special technique involving interchanging of the two specimens being compared permitted a precision of 0.05 x X in average thermal expansion over the range 27° to 600°C. The specimens were heated and cooled in vacuum or in a protective atmosphere at a rate of 50 °C per hr. Ferrovac E iron was used as the comparison specimen and in every case had a coefficient of expansion higher than (or equal to) that of the alloy. Since unintentional impurities are an important factor in studies of dilute alloys, special attention was given to the purity of the iron and the alloys used. The alloys were the same of those used by Abrahamson10 and by Michalak," and their preparation is described in these references. Chemical analyses of the Ferrovac E iron and of typical Fe-W and Fe-Mo alloys are given in Table I. The purity of the iron and alloys is undoubtedly higher than in the

Jan 1, 1962

By Oliver Bololes

UNDER the able leadership of Samuel H. Dolbear, the Committee on Nonmetallic Minerals furnished a program of sixteen papers comprising three sessions. An outstanding accomplishment in technology presented at the first session by Benjamin L. Miller and C. H. Breerwood is the application of flotation to the purification of limestone used in cement manufacture. In place of selective quarrying to provide high-grade raw material, the quarry-run stone is pulverized and treated in froth flotation cells for removal of free silica and mica. Some advantages are cheaper quarrying, more complete utilization of quarry rock, avoidance of purchasing high calcium stone, lower fuel cost and improvement in the finished cement. Paul M. Tyler presented the general subject of milling methods as applied to nonmetal lies. He pointed out the importance of some of the more recent refinements in ore dressing, and urged the need of a wider appreciation of their possibilities. The gypsum industry of Canada was described by L. H. Cole. Crystal growth during the setting process was illustrated by moving pictures. The Coastal Plain and interior salt

Jan 1, 1935

By Enrique Ibarra, Manuel J. Mendoza

"Abstract: This paper describes the current state-of-practice for the design of cast-in-place drilled shafts in granular soils under axial loading, addressing recent advances that take into account the surrounding soil grain size distribution and their behavior. The important role of the gravel content in the shaft response under axial loading is emphasized. Usual design approaches in Mexico are described, and the results of load tests from different sources are discussed. The analysis emphasizes the primary contribution of the lateral area of shafts to their axial bearing capacity, raising doubts regarding the common local idea of “point bearing shafts”. Finally, some lines of research are noted to permit advances in the important field of deep foundations. 1 INTRODUCTIONIn Mexico, cast-in-place drilled shaft foundations are widely used to support various structures in the west area of Mexico City, where alluvial and volcanic deposits predominate. Deep foundations are also used in modern construction works located in other major cities of Mexico. In fact, the use of drilled shafts for tall buildings and overpasses in the center of Guadalajara as well as in transportation works related to the Metro and roadways in Monterrey is well known. It is worth mentioning that these same structures have been applied in road bridges throughout the country.Procedures for pile construction in Mexico have been basically the same for the past 20 years (Paniagua et al., 2005); however, modern equipment has been incorporated into the construction industry, including innovations in sludge-drilling technology, control and the quality of the castings. In addition, novel and efficient procedures such as construction with continuous auger displacement piles have been implemented (Auger Cast in Place, ACP) and have begun to be used locally with success (Schmitter and Paulin, 2006).However, it can be argued that the technological developments that have resulted in more efficient construction procedures have not included a breakthrough in the full understanding of the phenomena or basic mechanisms of load transfer from piles to the surrounding subsoil and therefore in supported, tested and practical design methods. This is particularly true when seeking to determine the unit side shear strength of shafts drilled in granular media with gravels, where it has been observed that the commonly used calculations developed for sands underestimate the load-bearing capacity by frictionin a most important way. Due to the above reasons, it seemed appropriate to present in this paper a review of the current stateof- practice in Mexico for the design of cast-in-place drilled shafts, particularly in granular media, highlighting some recent advances and research that takes into account the grain size distribution and behavior of granular soil."

Jan 1, 2014

By O. S. Tinkler, K. C. Sole

"Although the first large-scale application of copper recovery by solvent extraction took place in Zambia in the early 1970s, it is only in the last decade that this technology has become widely employed in this part of the world and is now a mainstay unit operation in copper hydrometallurgical flow sheets. The mineralogy of the ores of the African Copperbelt, and hence the characteristics of African leach liquors, differs significantly from those in Chile and the southwestern USA, where copper solvent extraction has had a long and successful history. These differences provide operators, metallurgists, reagent vendors, and engineers with many challenges: new approaches are needed to adapt solvent-extraction technology for successful implementation in this region. This paper examines typical operating practice in the African Copperbelt, discusses differences compared with other parts of the world, and looks at some of the challenges and opportunities presented by these flow sheets. IntroductionFollowing the success of the Rancher’s Bluebird and Bagdad solvent extraction and electrowinning (SX–EW) operations in Arizona in the late 1960s, the Tailings Leach Plant at Chingola, Zambia, became the first large-scale copper SX plant in the world, commissioned in 1974. Despite the equipment design now being outdated, this plant still continues to operate successfully, indicating the versatility and adaptability of this technology. Today, there are some 75 copper SX operations worldwide with cathode production above 10 kt/a. The top ten producers currently account for about 40% of the global 4.3 Mt/a SX–EW copper production. South America (predominantly Chile and Peru) is the largest copper cathodeproducing region, with annual production of some 2 Mt. The Central African Copperbelt (Zambia and the Democratic Republic of Congo (DRC)) is second, with cathode production of 1.2 Mt/a, and North America (USA and Mexico) third, producing close to 0.8 Mt/a Cu (Solvay Cytec data, 2014). The remaining 0.35 Mt/a comes from all other regions combined (referred to as ‘Rest-of-World’)."

Jan 1, 2016

By Kamran Esmaieli

This paper investigates the behavior of ore pass walls under impact loads caused by material transiting through an ore pass. In particular it considers the influence of foliation in the rock mass surrounding an ore pass as both a triggering and accentuating cause of degradation. Based on empirical observations in several underground mines a numerical experiment was designed to understand the influence of rock mass foliation on impact-induced damage on ore pass walls. The distinct element method, and in particular the Particle Flow Code (PFC2D) was used to simulate three different rock masses surrounding an ore pass. Each simulated rock mass has similar properties but was defined by distinct dominant foliation (70o, 80o, 90o) along the foot wall. The numerical experiments investigated different scenarios whereby the walls were loaded by a projected rock fragment striking the foliated walls at a constant impact angle and velocity. The damage inflicted by the projectile rock fragment, on the foliated rock mass, was quantified using the number of impact-induced micro-cracks initiated on the ore pass wall. The results of the numerical analysis indicated that the presence of foliation resulted in greater damage zones in the surrounding rock mass. In addition, the extent of impact-induced damage to the ore pass wall increased as the angle of interception between the ore pass wall and the rock mass foliations decreases. This is in agreement with qualitative field observations.

Jun 1, 2012

Flat jack stress determinations in selected colliery roadways have revealed a range of measured stress from 330 lb/sq. in. tension to 3,750 lb/sq. in. compression. Photoelastic examination of loaded plastic and actual rock model mine openings has shown that the primary horizontal stress required to attain these measured stresses would be from one to three times the superincumbent vertical load.Examination of roof movement with a borehole extensometer and a series of anchors at various horizons to 30 feet in a vertical roof borehole showed that when a standing face was advanced the roof movement was practically confined to the lower two feet. The majority of this movement occurred during the 36 hours after mining at this face commenced.The use of a radioactive isotope and a scintillation counter in a pair of parallel boreholes is a sensitive and accurate method of roof bedding plane crack detection.INTRODUCTIONA knowledge of strata stresses is required to understand the deformation of an underground opening and, in particular, the roof behaviour. It is the aim of investigations currently being conducted by Australian Coal Association (Research) Ltd. to determine the stress existing around mine openings and the location and magnitude of roof movement.STRATA PRESSURE MEASUREMENTMost measurements of strata stress are performed at the surface of underground openings and the majority measure the change of strain resulting from stress relief. The accuracy of the measured value of stress depends upon knowledge of the rock modulus of elasticity. The flat jack method has the advantage that strain relief is restored by a measured stress applied directly by the jack. The rock modulus of elasticity can also be determined.

Jan 1, 1963

By A. K. Anyimadu

Ongoing development work on ultra-fine grinding for various applications at the Group?s concentrators has been conducted by Anglo Platinum over the last few years. Current potential applications for mainstream grinding and concentrate grinding are the subject of a group-wide research and development programme. The first 10 000-litre 2.6 MW IsaMill was jointly developed by Anglo Platinum, Xstrata Technology and Netszch for installation at the Western Limb Tailings Re-treatment project in Rustenburg, South Africa. The unit was commissioned in late 2003/early 2004,and has operated in an intermediate concentrate regrind application successfully since. This paper describes the operational performance to date, as compared with the original duty specifications and objectives. The first mainstream M10 000 IsaMill with a 3 MW drive will be operational in November 2006 at the Potgietersrus Platinum (PPL) ?Platreef? Sandsloot Concentrator in South Africa?s Limpopo Province. Keywords: Western Limb Tailings Re-treatment Plant, IsaMilling, Platreef, platinum, palladium, PGMs, tailings.

Jan 1, 2007

By Ralph M. Barnett

It is no longer a question of "If" mining operations will meet standards and regulations set by various governing bodies and the demands of citizen groups. Legislation is fact. The needs of citizens are becoming more of a integral part of mining company planning. "Open Planning", regardless of some frustrations it provides, is working. Climax, AMAX Chemical and AMAX Exploration are successfully employing several citizen involvement techniques in exploration and feasibility study phases of planning for potential new mines.

Jan 1, 1978

The minerals industry consumes billions of dollars in raw materials, equipment, tools, services and chemicals. The industry, though, has turned overmuch of the research and development (R&D) for these products to manufacturers and suppliers. Now the industry and its suppliers must decide how much R&D the mining industry should be responsible for and what role the suppliers should play. Promoting R&D As a result of the current environment in the mining and minerals industry, there has been a substantial decrease in R&D. Depressed prices, stagnant growth, cost cutting and rationalization are evident.

Jan 1, 2000

By Charles W. Daugherty, James P. Gould, Kenneth R. Ware

INTRODUCTION As illustrated in Figure 1, the Washington Metropolitan Area Transit Authority's (WMATA) rapid transit system (METRO) ultimately will comprise 100 miles of line divided among 10 routes. At this time about 46 per cent of the system is under construction or in operation. Planning and design of an additional 38 per cent is at an advanced stage. Of the 84 miles under development or construction, about 10.4 miles consist of soft ground tunnels, and another 1600 feet of mixed face. This paper describes most of the factors considered by designers in setting grades for such tunnels. It is hoped the paper will be a useful guide to planners and engineers in developing similar transit systems. The problems faced in Washington, including those related to geology, are not so unique that the solutions cannot be applied to other systems. The paper also may be of interest to contractors who have not perceived the logic behind the selection of a particular vertical alignment. An attempt is made to explain the background constraints that make most tunnel alignments a compromise among competing alternatives. Readers might assume that the choice of alignments is largely controlled by geological conditions. In fact this is merely one of many factors to be considered.

Jan 1, 1976

By F. G. Horino

The Bureau of Mines conducted compressive strength tests on model pillars of selected rock types with each pillar containing a critically oriented plane of weakness. The objective of these tests was to determine if a significant increase in the strength of the model pillar could be obtained by either (1) installing tensioned rock bolts through the pillar and normal to the plane of weakness, or (2) wrapping tensioned steel wire ropes around the pillar at uniformly spaced intervals along the pillar. Equations based on Coulomb's failure criterion are developed to predict uniaxial compressive strength of model pillars that are either rock-bolted or wire-roped. Laboratory compressive strength tests on unbolted and bolted model pillars of sandstone, marble, Indiana limestone, and oil shale containing a plane of weakness oriented at 45° showed that the bolted pillars are stronger than the unbolted pillars by 84, 31, 52, and 28 pct, respectively. Laboratory compres-sive strength tests on nonroped and roped model pillars of Texas limestone, sandstone, and granite containing planes of weakness showed that the roped pillars were stronger than the nonroped pillars by factors ranging from 1.01 to 2.41, depending upon the angle of the plane of weakness and the rock type. Rocks with a low Young's modulus benefited most by the wire-roping technique.

Jan 1, 1971