Search Documents

By Kevin Connor

During 1984, minerals exploited in Burundi included gold, kaolin, lime, and peat. Over 1,100 troy ounces of gold was extracted and traded during the year as a result of the lifting of the Government ban on gold mining in mid-1983 and the establishment of an artisan mining program and licensed trading counters. Almost 2,000 tons of kaolin was mined for the manufacture of insecticides. Lime production was for domestic fertilizer applications. Amoco International and the Government signed an accord late in the year for a petroleum exploration program covering 600,000 acres of Burundi's onshore Ruzizi Plain and part of northeastern Lake Tanganyika. Amoco was expected to begin the exploration program by mid-1985. Anticipated program costs could run as high as $200 million.2 The Finnish company Ekono Oy completed its peat industrial energy development studies for the Buyongwe peat deposits of northern Burundi by the end of the year. The project assessed the quantity and fuel quality of 13,000 hectares of peatland and was part of a larger study for developing the Musangati lateritic nickel deposits of Burundi, estimated at 3% of the world's reserves of nickel. The Buyongwe peat would fuel dryers and an electrical generating plant for supplying power to nickel ore processing facilities. Briquetted peat would also be used as a substitute for wood and charcoal, presently the main sources of rural energy in the country and rapidly depleting because of deforestation. The study also evaluated the most economical methods to harvest the peat bogs. The study was financed by the International Development Association (IDA), United Nations Development Program (UNDP), Finnish Aid-Finnida, and the Burundi Government.

Jan 1, 1986

By Robert J. Watters, Peter C. Kelsall, Joseph G. Franzone

Two separate studies investigated the compressive strength of basic igneous rocks and its relation to index properties such as porosity, density and soundrave velocity. The rocks tested were weathered dolerite from S. W. England and vesicular lavas from California. In both cases strength was affected considerably by porosity. In the dolerite, strength was also affected by fissures (microcracks) which were formed in the parent rock by shearing and later accentuated by weathering. While test results show that porosity, density and sound velocity are not reliable indices of rock strength, these properties are useful in interpretation of strength test results. Index testing can be used to classify samples according to similar behavior and to recognize the influence of fissures.

Jan 1, 1986

By J. Bowders

A case study describing the expansion of Marion County landfill is presented. The exapansion area is located on a deep mined area. Finite element analyses were used to predict the surface subsidence and associated tensile strains on the landfill liner of the expansion site. A synthetically reinforced liner system is recommended to minimize the impact of the subsurface movements on the integrity of the liner system.

Jan 1, 1986

By D. L. Passmore, J. D. Bennett

The degree of injury and days lost from work due to an injury are examined for selected electrical sources, occurring in conjunction with falls of the injured miner or with selected machinery, that could have been eliminated by use of diesel equipment. Although the number of preventable electrical source injuries is small relative to the total number of injuries during the period examined, many lost-time injuries could have been precluded and thousands of days lost from work could have been avoided.

Jan 1, 1986

By A. K. Gangopadhyay, J. J. Moore

The effect of grinding media composition, mineral type, and slurry environment on the wear rate of various grinding media (balls) are discussed. Sufficient wear data have been obtained and correlated. Modes of wear were determined from examination of the ball surfaces using scanning electron microscopy. Five modes of wear have been identified to be operative under certain slurry conditions for the various ball compositions studied.

Jan 1, 1986

The Electricity Generating Authority of Thailand own and operate an opencut mine supplying coal to on-site power stations at Mae Moh, 600 km North of Bangkok. The mine is being expanded from an annual production of 1.5 million tonnes per year in 1982 to over 9.5 million tonnes per year by 1991. The mine will be amongst the largest open pit operations in the world. It is technically difficult to operate and plan due to complex geology, weak strata and surface constraints including reservoirs, forests and traditional villages. This paper presents a case study of mine planning for the above project including associated collection and processing of geological and geotechnical information. The existing operation is described, as well as the strategy adopted for the mine at expanded production. The planning covers various phases of mine planning including a Conceptual Study, a Definitive Study and detailed short term planning. Each stage incorporated new information and reflected a higher level of confidence in the data and resulting plan. Sophisticated computer techniques were required including geological modelling, calculation of volumes, geotechnical analysis, scheduling and costing. The planning was undertaken on site by a team of Australian and Thai Engineers as part of the Thailand-Australia Lignite Mines Development Project which is a four year programme of assistance funded by the Australian Government.

Jan 1, 1986

By M. G. Ayat

A novel tracing technique employing specifically prepared trace particles has been applied to coal preparation separatory systems. The technique employs individually prepared trace particles representing specific known sizes and densities of coal particles. These trace particles are injected into the feed, to the processing circuit, and are then detected at locations in the coal product and refuse streams. It is anticipated that on-line input of the generated partition data will be linked with computer technology to provide rapid analysis of the processing efficiency, and to allow for process control. This tracing technique can revolutionize many processing operations from the diagnostic viewpoint as well as from the coal processing standpoint.

Jan 1, 1986

By Harry W. Campbell

During 1983, the U.S. Bureau of Mines conducted a mineral survey of 19,700 acres that included the Fish Creek Mountains WSA (Wilderness Study Area), 15 miles southwest of the Salton Sea. Two United States Gypsum Co. claim groups in the WSA have more than .20 million tons of inferred gypsum reserves. These high-grade, surface and near-surface gypsum deposits are an extension of a gypsum bed that has been mined continuously since 1922. The Waters prospect in the central part of the WSA has large quantities of limestone suitable for many commercial uses. Sand and gravel is plentiful in the WSA in alluvial fan and ancient shore-line deposits. Limestone and alluvial deposits are not economic because similar material is closer to potential markets. No evidence of energy minerals or geothermal resources was identified in the WSA. A portion of the eastern Fish Creek Mountains WSA is leased for oil and gas exploration. United States Gypsum Co. holds eighteen unpatented placer claims in the northwestern part of the WSA. No other mining claims or mineral leases were identified in the study area. No mineral production is known from within the WSA.

Jan 1, 1986

Consolidated Rutile Limited's (CRL) operations incorporate the exploration, mining, processing, marketing and distribution of mineral sands. This paper outlines the current scope of CRL operations in vegetated sand dunes on North Stradbroke Island (NSI), Queensland. Included are some specific comments relating to design and construction of high capacity dredges which float in artificial ponds and are an integral part of mining high dune ore reserves. Three floating cutter suction dredges with combined sand throughput capacity in excess of 7000 tph are used in mining operations on NSI. Initial processing is by gravity and magnetic methods on large wet concentrators also floating in the artificial ponds. Spiral sluices are used exclusively in the newest concentrator, which has the highest recovery of heavy minerals.

Jan 1, 1986

By Thomas A. Phillips

This publication is an economic evaluation of the Bureau of Mines electrolytic process for recovering lead from scrap lead-acid batteries. In this process, scrap batteries are crushed and separated into metal and sludge fractions. The metal fraction is cast as anodes and electro- refined. Lead in the sludge fraction is converted to lead carbonate by reaction with an ammonium carbonate-ammonium bisulfite solution. The lead carbonate is then dissolved in a fluosilicic acid electrolyte from which pure lead metal is electrowon. A cost estimate is presented for a plant capable of processing 10,000 scrap batteries per day. The fixed capital cost for this plant is estimated to he $14 million on a fourth quarter 1984 basis. Operating costs are estimated to be $0.15/lb Pb recovered. Assuming a lead selling price of $0.17/lb, the interest rate of return on investment after taxes is 11 pct. A lead selling price of about $0.21/lb is needed to obtain a 20-pct-interest rate of return.

Jan 1, 1986

By S. C. Bandis, N. Barton

During drilling of deep boreholes, local mechanical failures of the wellbore walls may occur due to the inability of the incompetent overburden and reservoir rocks to withstand drilling-induced changes of the stress environment. At present, borehole failure mechanisms in three-dimensional stress fields are poorly understood. Our experimental investigations based on 3-D physical models demonstrate the stabilizing effect of the intermediate principal stress. The latter may play a dominant role in maintaining the integrity of the stress relieving failure zone around the borehole. However, this will depend on the stress anisotropy, the angle of hole deviation and on the angle of internal friction. Our tests also indicate that the failure zone can accomodate high extensional strains. Finally, relations between the physical models and closed-form elasto-plastic solutions are discussed.

Jan 1, 1986

By William H. Sutherland

INTRODUCTION Coal workers' pneumoconiosis and sili- cosis are only two of several diseases which are rlassed as pneumoconiosis. These are respiratory diseases caused by dusts which are inhaled and accumulated in the lungs. The individual particles of dust cannot be seen by the human eye. They are so small that they escape the natural cleansing mechanism of the nose and air passages and make their way down to the terminal air sacs of the lung where they injure the cells and cause the formation of scar tissue. Consequently, if there is exposure to high concentrations of dust over a period of time - usually, a number of years - the amount of scar tissue increases and begins to impair breathing. As a result, the miner develops shortness of breath, coughing and wheezing ad-if exposure continues - this progresses to permanent disability and frequently to death. Death is often due to pulmonary heart disease, the effect of stress on the heart 2s it tries to compensate for the weakened lungs. Specifically, silicosis is an occupational lung disease caused by the accumulation of free silica (quartz) in the lungs. Silicosis is considered the most important form of pneumoconiosis, not only because of its seriousness as a respiratory crippler, but also because of the large number of workers who risk contracting it in a variety of occupations. Quartz is one of the most common substances of the earth's crust, estimated at about 60 percent. Silicosis has been found in coal, metal and granite miners, as well as in other workers, such as sandblasters and pottery makers. Silicosis is also known to predispose the lung to tuberculosis and to increase the chances that a worker will contract chronic bronchitis and emphysema. The seriousness of silicosis was tragically brought to public attention about 50 years ago. During 1932-34, workers were involved in digging a tunnel through rock at Gauley Bridge, West Virginia. While their exposure time was relatively short, they developed silicosis because of the high concentrations of quartz. By 1936, 476 workers had died of silicosis and about 1500 were believed to have the disease (Washington Post, 1982). It is difficult to tell how many coal miners have silicosis. Because x-rays and breathing function tests do not show the difference the type of pneumoconiosis is generally diagnosed by the miner's work history. For example, if a worker

Jan 1, 1986

By R. E. Thill

An ultrasonic, pulse-immersion apparatus and method are described for determining the effects of moisture on the dynamic elastic properties of rock. The method provides an alternative approach for assessing the moisture sensitivity of rocks. Ultrasonic wave velocities are continuously monitored in immersed rock samples as a function of water absorption and time up to saturation. Moisture effects on compressional wave velocity vary as a function of the type of rock and the time and amount of water absorption. Regression analyses are used to curve-fit plots of the data and to derive empirical expressions for compressional wave velocity as a function of water content for different categories of rock. Results indicate that compressional wave velocity can be used to predict both the moisture content and its effect on strength and deformational properties of rock. These results have potential for detecting or monitoring bad roof conditions in situations where the mine rock exhibits strength degradation with moisture absorption.

Jan 1, 1986

A. Cook K.A. Grace's article advocates usage of the terms describing resources as defined by the US Bureau of Mines (USBM) and the US Geological Survey (USGS). Originally recommended in 1943, the terms were revised in 1976 and again in 1980. Mr. Grace further recommends that the term reserves should be severely restricted and that it should encompass mining and processing factors. The list of references quoted in the article does not, however, mention the study concerning reserves that was made over a period of almost four years by a joint Committee on Definitions. This committee was sponsored by three societies - the American Institute of Mining, Metallurgical, and Petroleum Engineers (AIME), the Society of Economic Geologists (SEG), and the American Institute of Professional Geologists (AIPG). Most of the detailed work was done by a working party appointed by the Society of Mining Engineers (SME) of AIME. After studying previous definitions in the US as well as in the United Kingdom, Canada, Australia, France, and other European countries, the following definitions were proposed and accepted in 1974 by the SME board of directors. (Ore reserve definitions in Rhodesia, South Africa, or New Zealand were not mentioned as having been reviewed. Table 1 lists definitions from MINING ENGINEERING, July 1975. Notice in Table 1 it was mentioned, under Resources, that the definitions of reserves were recommended for the purposes of commercial evaluation. It was further stated that the terminology adopted by the USBM and the USGS, as released to the public, covering resources, was recognized as such. Mr. Grace also recommends that reserve calculations should allow for future losses in ore tonnage, ore grade, milling, and smelting. Unfortunately, it might take years to develop a prospect after it has been discovered. Mining methods have to be tested before being finalized in order to know what tonnage of ore is going to be lost, or how much dilution is likely to occur. The same problems are present in concentrating or in smelting. Operating mines usually know how mined grade compares with ore reserve grade. They can usually predict fairly closely what their final metal recoveries are probably going to be. It is, however, expecting too much to have to delay quoting reserves from say a recently drilled prospect. Any responsible mining geologist or mining engineer (or company for that matter) should state several things about an ore reserve calculation: that it is or is not a preliminary estimate only; that estimated grades have not been diluted to allow for a future, as yet unknown, mining method; that metal recoveries are or are not only tentative, based perhaps on drill hole samples only or on no metallurgical testing at all. [ ] Reserves of a partially explored prospect are always quoted when it becomes necessary to raise capital. If they are described as preliminary only (really just tonnage and grade estimates and not true "reserves") in addition to being accompanied by some of the items just mentioned, nobody is going to be misled. If, on the other hand, a report by a member of the SME or SEG is intentionally misleading, the individual must be reported and eventually disbarred from his or her society. To summarize, let us stay with the definitions of ore, ore reserves, and related terms as recommended and accepted by SME. I might add that on occasion I have used a fourth category in my ore reserve calculations, namely Geologically Possible Ore. This category is more or less the same as Inferred ore defined by the USBM and USGS. I have never given a grade to this category, which may be based only on geological mapping, geochemical sampling, or geophysical traversing. ?

Jan 1, 1986

By Unver B

Longwall advance mining is still the predaninant system of coal extraction in the U.K., contribiiting to sane 70 % of underground coal production. Gate roadways providing access to a longwall advancing coal face are maintained adjacent to a rib pillar under high strata abutment pressures and the caving rock mass. It is very difficult to realistically model such access roadways using mathematical or numerical techniques and hence, predict roadway closure. For the past 15 years, a research group in Nottingham University has been engaged in the study of longwall gate roadway stability using observation methods. Gate roadway deformations have been measured in 224 gate roadways and a comprehensive data base has been established. The paper describes the statistical analysis of this database and presents sane. predictive equations which will enable a forecast of the gate roadway closure to he made. Further field work to validate these equations. is described together with an error analysis. The results are very promising and indicate that it is possible to predict gate roadway closure in the U.K. within practical limits of Accuracy.

Jan 1, 1986

By Peter N. Gabby

A mineral survey of 8,300 acres of the 24,980-acre Burnt Creek Wilderness Study Area (ID 45-12), was conducted by the U.S. Bureau of Mines in 1985 at the request of the Bureau of Land Management. The study area is located in Custer County, ID, 90 miles northwest of Idaho Falls. No mines, claims, or prospects are in the study area. The northern half of the study area and adjacent lands to the north, northeast, and east are or were recently under oil and gas lease, Basalt and latite-andesite of the Challis Volcanics predominate in the study area. Several hundred feet east of the study area is a quarry in talus of Mississippian-age limestone that was used for sized 100-pound rock fill in the Old Dry Creek Reservoir dam. Two samples, one taken at the quarry and the other at a limestone outcrop on East Fork Burnt Creek, have CaC03 content in the range of 90 to 95 percent, and is suitable as the limestone component of Portland cement, However, limestone outside the study area could supply foreseeable demand. Lead- silver mineralization has been observed in Paleozoic carbonate rocks elsewhere in the Lost River Range, but these rocks do not occur in the study area.

Jan 1, 1986

By Richard A. Winters

In 1985, at the request of the U.S. Bureau of Land Management, the U.S. Bureau of Mines studied 49,875 acres of the 54,833-acre Big Jacks Creek Wilderness Study Area (ID-111-7C) in order to evaluate the mineral resources. The study area is located in Owyhee County, ID, about 15 miles southwest from Bruneau, ID. No mining districts are in the study area, but part of one placer claim, located in 1924, extended into it. The northern portion of the area was covered by oil and gas lease applications; all were cancelled prior to 1985. No economic concentrations of minerals were found in the study area. INTRODUCTION This report describes the USBM (U.S. Bureau of Mines) portion of a cooperative study with the USGS (U.S. Geological Survey) to evaluate mineral resources and potential of the Big Jacks Creek study area at the request of the BLM (U.S. Bureau of Land Management). The USBM examines individual mines, prospects, claims, and mineralized zones, and evaluates identified mineral and energy resources. The USGS evaluates potential for undiscovered resources based on areal geological, geochemical, and geophysical surveys. Results of the investigations will be used to help determine the suitability of the study area for inclusion into the National Wilderness Preservation System. Although the immediate goal of this and other USBM mineral surveys is to provide data for the President, Congress, government agencies, and the public for land-use decisions, the long-term objective is to ensure the Nation has an adequate and dependable supply of minerals at a reasonable cost.

Jan 1, 1986

By Christopher J. Bise

PRINCIPLES OF MINE PLANNING During the initial planning stages, all mining operations are analyzed and evaluated in a similar fashion. This similarity holds true because the mine-planning procedure can be reduced to a network of interrelated systems that are tied together by a common philosophy of mine planning: namely, that the resource is to be extracted in a manner which is safe, efficient, and profitable. The success of the mining operation cannot be guaranteed unless each of these three requirements is met. Fig. 1 shows a flowchart for the initial planning of any mining operation. Notice that there is a preplanning stage that leads to the planning of four interrelated systems. The preplanning stage includes property exploration, estimation of production and manpower requirements, and the establishment of construction timetables. The four systems, evaluated after the pre-planning stage, are broken down into the following: (1) Excavation and handling system, (2) Strata control system, (3) Operating support system, and (4) Service support system. The Excavation and handling system includes the selection of all the equipment for the removal of the resource from its in-place deposit (e.g., draglines, continuous miners, rock drills, etc.) and for the transportation of the mined material from the face (e.g., belt conveyors, trucks, etc.). The Strata control system incorporates all those considerations which maintain the integrity of the roof, ribs, floor, and overburden both during and after the extraction phase; typical considerations in this area include pillar sizing, artificial support of the immediate roof in mine entries, and subsidence protection. The Operating support system contains the "necessary evils" of mine planning; the system consumes a large percentage of the mining engineer's planning time but does not contribute to the actual extraction of the resource. However, if proper attention is not paid to the various components of the system, such as ventilation, drainage, and power, then the mining operation will not perform to its capabilities. Finally, the Service support system is composed of those operations which keep the mine running efficiently; typical examples of these include maintenance and sup- ply. One important concept that Fig. 1 is designed to emphasize is that the four systems are interrelated; typically, a slight alteration of one can affect the performance of another. If these interrelationships are ignored, the effects on the system can be disastrous. The mine preplanning stage and the four subsequent system evaluations constitute the Analysis portion of the mine planning flowchart. After this portion of the study is completed, the overall projected operation can be evaluated by techniques such as financial analysis. This last step in the study is referred to as the Synthesis of the previously calculated parameters into an overall plan. Much has been written about the overall evaluation of mining properties, but, over the past thirty years, very little has been written about the analysis of mine- planning systems in a coordinated manner. Further, those texts which attempted this topic have failed to give sufficient examples for successful implementation, thus supporting the operating engineers' lament that it is easy to discuss theories but difficult to show applications. This text is intended to bridge this gap. Examples of the various stages of the analysis portion of the mine planning flowchart shown in Fig. 1 will be covered in this text, with the exception of the Service support system, since this system is oriented more toward day-to-day planning than long-term mine planning. INTERNATIONAL STANDARDIZATION The benefits that can be derived from an international standardization of the units used in mining engineering calculations are numerous. The interchange- ability of equipment parts and the ability to analyze and compare performance and design specifications on an equal basis are just two of the goals desired by both manufacturers and mine operators. Unfortunately, conversion to an international standard has not been rapidly achieved by engineers in the United States, due to their training under the English system. The Society of Mining Engineers of AIME has made the commitment for the adoption of the Systeme International d'Unites (SI) in all mining engineering calculations. Since many practicing mining engineers and students in undergraduate programs still find difficulty in relating to SI units, the calculations in this textbook will use the English system, with Table 1 available for conversion into SI units.

Jan 1, 1986

By F. Touboul, M. Thiercelin, K. BenNaceur

Introduction The need to develop accurate predictive hydraulic fracturing simulators arises from the consideration of vertical containment for the fracture. Fracture height growth from a pay zone into adjacent layers has been shown (see Cleary [I]) to depend on three sets of parameters for the different strata: - elastic properties, - closure stress variations, and, -fracturing fluid leak off, and poro-elastic stresses. Qualitative analysis of the effects of these parameters has been reported in the literature. The first effects were described by Van Eekelen, using simple elasticity considerations [2]. The effect of stress variations was described numerically by Simonson and a1. [3] and experimentally by Thiercelin [4]. Effects of back stresses induced by fluid invasion on fracture propagation were considered by Cleary [5]. In order to couple these effects, a numerical code al- lowing the simulation of three dimensional growth of a hydraulically induced fracture has been developed with the ability of representing the effects of heterogeneities on fracture lateral and vertical extension. The model is based on a new variational formulation of the boundary integral representation of three-dimensional elasticity. The fluid flow and elasticity equations are solved using a moving mesh representation which offers enough flexibility to enable the simulation of any closure stress distribution. Simpler models representing fracture height growth (P3DH models) have been developed [6] [7] that approximate the fracture by a series of one dimensional segments, and the limitation of such approaches is examined in this paper. 1 Description of the model 1.1 Fracture Geometry Hydraulic fracturing simulations involve the coupling of solutions to elastic deformations, fluid flow in the fracture, and fluid leak off into the formation. Since the use of direct solution techniques (i,e,,3D finite elements) is prohibitive, the method used in this study is baaed on a boundary integral representation of the 3D elasticity equations. 1.2 3D Models The classical representation of the problem of a fracture in an infinite medium by boundary integrals is [8]: [ ] where u is the unknown displacement field, r n is the traction operator, I? is the fracture surface, and K is the Kelvin tensor of fundamental solutions to the elasticity operator. Using the notation: [ ] for the displacement discontinuity (or fracture width), one can attempt to solve the boundary integral relation using surface integrals (91 or the displacement discontinuity technique, first introduced by Crouch [lo], and extended to three-dimensional problems [Ill. However, numerical problems arise since the Kelvin tensor has a singularity in

Jan 1, 1986

By Fabjanczyk MW, Aziz NI, Hii J

The paper presents the results of a series of pull out tests performed on roof reinforcement systems currently being adopted in mines in Australia 7mm wire, dividag bar, 15.2mm strand cable, and birdcage cable. The study also investigated the load deformation chara- cteristics and the various design parameters controlling the effectiveness of a cable-grout system. Suggestions for continued work are Highlighted.

Jan 1, 1986