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Placing a detonating explosive inside a volume of rock is an efficient method of rock fragmentation. The explosion generates internal tensile stresses in the rock, and because rock is a brittle material, this brings about crack propagation and fragmentation far more efficiently than does application of explosive on the surface. To get the explosive inside, we drill a pattern of boreholes and charge the explosive into the holes. This is really the one and only purpose of making blastholes in mining: to give access for the explosive to the interior of the rock. No matter how big and expensive a drilling jumbo we stand up in front of a rock face, and no matter how many boreholes we let it drill, the rock does not fall apart by itself without blasting. It is the action of the explosive in the boreholes that does it. When we consider that we need a pound or two of explosive for every cubic yard of rock to be fragmented, and a pint of borehole volume for each pound of explosive, we see that the process of blasthole charging is an important element in the whole process of rock blasting.

Jan 1, 1975

By K. A. Natarajan, K. S. N. Murthy

Growth of Thiobacillus ferrooxidans on pyrite mineral surfaces and in 9K leach media was studied through estimation of bacterial protein in the different phases. Bacterial attachment was found to be governed by particle size of the mineral, period of incubation and by stationary or agitation conditions used during incubation. Increased bacterial growth in the liquid as well as on the solid phase was observed with decreasing particle size and increasing incubation periods. Increased bacterial attachment to pyrite mineral surfaces was observed to promote iron dissolution.

Jan 1, 1993

By Norm Greenwald

The Environmental Protection Agency ("EPA") has been attempting to develop a federal regulatory program for mine waste under Subtitle D of the Resource Conservation and Recovery Act since 1986. Recent regulatory and legislative events are now bringing this goal closer to reality. This paper discusses the mining industry's perspective on a number of the issues currently being addressed at EPA's Policy Dialogue Committee and in Congressionally-sponsored negotiating sessions.

Jan 1, 1992

By Chris J. Conway, Bruce W. Atkinson, Graeme J. Jameson

The flotation of coal in the fie and coarse particle size ranges presents particular problems. Fine or ultra-fine coal less than 100 microns presents a challenge to conventional flotation machines because the rate of capture of the coal particles can be very low, so longer residence times are needed. Also, conventional mechanical cells are not normally designed with froth properties in mind. Froth drainage may be inadequate, leading to excessive entrainment of ash. The upper limit of flotation of coal is normally put at about 500 um (30 mesh). It appears that, in mechanical cells, coarser particles tend to be torn away from bubbles in the turbulent environment created by the impeller. In this paper, results are presented from plant trials of a high-intensity flotation column of novel design, namely the Jameson cell. Extensive trials have been conducted on coal slurries with a top size of around 1 mm. Size-by size analysis shows that it is possible to achieve high yields of low ash product over the whole particle size range.

Jan 1, 1995

By L. J. Drew

The plate tectonic setting, regional geology, and certain aspects of the economic geology of the iron-rare-earth-nio-bium ore bodies at Bayan Obo, Inner Mongolia, China, were studied by a team of geologists from the Tianjin Geologic Research Academy and the U.s. Geological Survey between 1987 and 1989. These ore bodies were formed by hydrothermal replacement of Middle Proterozoic dolomite in an intracontinental rift setting. A variety of veins and/or dikes that have a carbonatite-like mineralogy cut the footwall clastic rocks and migmatites. A stockwork of veins occurs at several locations in the footwall. The hanging wall is a shale that has been converted to a K-metasomatite and has microcrystalline potassium feldspar as its principal constituent. This shale served as a sealing caprock that contained the chemical solutions that reacted with the dolomite and that created the enormous concentration of mineralized rock in an 18-kilometer-long syncline. The rocks that host these ore bodies and the associated mineralized areas occur today as roof pendants in granitoid rocks of Pennian age that were emplaced during a continent-to-continent collision during that period.

Jan 1, 1991

By Rolando V. Cuaño

For geostatistical applications, heterogeneous spatial phenomena are better modeled as mixtures of populations. However, the modeling of the constituent populations can become complex. The alternative mixture model offers a simplified approach to the w modeling problem. The model is applied and tested on the Walker Lake data set. Compared to the univariate ordinary kriging model, the alternative model generates less biased block estimates.

Jan 1, 1996

By Yuting Xue, Xin Li, Ihsan Berk Tulu, Gaobo Zhao, Deniz Tuncay, Mindi Ruan

Most coal mine roofs in the Appalachian region consist of laminated shale, which is prone to brittle failure. Accurate modeling of shale roofs is vital for studying cutter failures of these shale roofs, and ordinary and formational bedding planes play a significant role in the response off the shale roof to mining-induced stresses. This paper presents a robust method for constructing three-dimensional shale roof models using limited borehole cores and leveraging image processing techniques. The approach begins with image extraction from shale cores. Then, we extract the portions that feature the core and employ image-stitching techniques to merge them seamlessly. Once the images are stitched, they are duplicated horizontally and merged to create a cross-sectional plane image representing a shale roof. This roof cross-sectional plane image serves as an input to our proprietary Digital Image Processing (DIP) algorithm, which is adept at extracting ordinary bedding planes (interfaces that represent color transitions between a single shale unit). The extraction process involves transforming discrete core points (ordinary bedding plane pixels) into continuous lines representing ordinary bedding planes. Finally, extending this method into the third dimension, the model is further extrapolated to form a comprehensive three-dimensional shale roof. Through this process, the geometry information of ordinary bedding planes can be extracted for each type of shale in cores, including sandy shale, gray shale, dark shale, etc. This work bridges the gap between limited core data and comprehensive 3D geological modeling, offering valuable insights into identifying and quantifying the variations in different shale roof geologies.

Jun 25, 2024

By X. Wu

A quantitative damage evaluation caused by ground motions associated with strong roof caving is presented. The strong roofs are modeled as either cantilevering or bridging beams over continuous elastic foundations subject to an exponentially distributed vertical stress. Major factors influencing roof caveability and strain energy buildup are identified and investigated. A methodology to evaluate the strain energy accumulation caused by overhanging roof is presented. The potential for mine tremors is determined in terms of the local Richter magnitude ML which depends on the seismic energy transformed from the stored strain energy released when the roof fails. A particle velocity model is applied to estimate the damage area associated with roof collapse. A case study from a Utah coal mine shows that estimations of bump severity and damage area agree well with the field observations.

Jan 1, 1995

By Myron W. Mellor

Our efforts at McNally, to find a better way to mechanically separate particles from liquid in a slurry have led to the development of two new centrifuges. The first unit utilizes a slotted opening screen as the filter media and retains all plus 200 Mesh and most of the 200 by 300 Mesh particles. The second unit is a solid bowl centrifuge with a novel method of removing the solids and delivers an effluent containing as little as 300 PPM solids in suspension. The first unit was designed to separate particles in the range of about 1 MM x 0 or smaller top size from the liquid slurry and produce solids having low surface moisture content, and a liquid concentrate containing a low percentage of solids. A prototype of this unit has been in the field undergoing tests for over two years. A few of these test results are shown in Tables I & 11. Testing has been mostly limited to the field of coal, how- ever this does not mean that the machine would accept only coal slurries. The machine has produced a dewatered product having as low as 5.5% surface moisture, and an effluent containing as low as 1.4% solids and handled slurries containing from 15 to 50% solids by weight.

Jan 1, 1975

By Hans Breuer

The new regulations for the bituminous coal mining industry, issued by the mining authorities of the Federal Republic of Germany, are aimed at reducing to a feasible minimum any development of the coal workers pneumoconiosis (CWP) by lowering the admissible dust exposure of mine workers. Additional and improved measures of dust suppression and job assignment control *) are required for the purpose In this connection two basically different demands are placed on dust measurements: As far as dust suppression is concerned, the causes of dust development and the effectiveness of methods applied to reduce dust concentrations have to be identified, whereas with regard to the control of job assignment, the dust exposure of mine workers has to be depermined. Demands placed on dust measurements -- specifically for determining dust exposure -- are liable to become more severe since the threshold limit values were considerably reduced in these last years and since any additional dust suppression measures as well as a purposeful job assignment to certain mine workers are dependent on relevant measuring data. Therefore, research work has been carried out with the objective of measuring and evaluating, in terms of their effect (i. e. their incidence on the development of a CWP), size distribution, concentration, and specific noxiousness of any prevailing dust conditions.

Jan 1, 1980

In this paper, the logic and the capabilities of a long term production planning method for open pit mining are presented. The method is the first attempt in obtaining simultaneous solutions to the four interrelated parameters of open pit mining; 1) the mine life, 2) the specific blocks to be mined each year, 3) the amount of ore and waste to be mined each year, and 4) the ultimate pit limits. An efficient cutoff grade can also be obtained through a sensitivity analysis. None of the existing methods can bring such a comprehensive solution to the problem. A production plan for a real life gold deposit is given to illustrate the logic and the capabilities of the method.

Jan 1, 1993

By Saurabh Rastogi, Vikram Shishodia, B. Pitchumani

Comminution is a unit operation which consumes major part of energy in mineral processing industries such as fertilizer production. Ball mills are widely used for size reduction of a given ore to the liberation size that is required in further beneficiation processes. In grinding of materials much effort is concentrated on control of top size of the product and this results in production of fines, also creates secondary problems of pollution due to the difficulty in the collection of fine particles. The present work has been carried out to control product size distribution for rock phosphate grinding in an Industrial Ball Mill of 600 TPD. The plant data are taken for a given feed distribution and mill operating conditions. The information at various Ball Size distributions are collected. The comminution functions such as specific rate of breakage and breakage distribution functions are estimated by back calculation technique to solve the mass balance equation. A simulation program is written to study the product size distribution obtained for various ball size distribution.

Jan 1, 1993

By Glenn J. Phillips, Debra L. Musick

The operating mine is dynamic, everchanging, and a continuous moving target. The only way to effectively manage such a creature is to be able to evaluate the cost of operation over short enough time periods that rapid effective controls can be implemented before loss can erode the marginal profits in todays market place. Such short term evaluations can provide the basis for the long range planning that can keep an operation healthy in the future. The spreadsheet programs on small computers (PC's) offer the possibility of such evaluation by accumulating data in a useable format, providing timely cost reporting and providing a tool for use in evaluating the day to day alternative choices of the real mining world.

Jan 1, 1987

By W. L. Staker

The Bureau of Mines investigated selective extraction of Au and Ag from a low-grade Au ore containing Hg. Gold and silver were extracted from the ore in cyanide slurries, and Hg extraction was suppressed with sodium or calcium sulfide. Maximum Au extraction and minimum Hg extraction were obtained using solutions containing 0.34 lb NaCN/ton of solution. Increasing the cyanide concentration increased Hg extraction without increasing Au extraction. Mercury extraction from the ore was suppressed with 0-5 to 2.9 Pb CaS/lb Kg in the ore. Gold-to-mercury ratios of 100:1 to 400:1 were obtained in the leach solution, and on the activated carbon in a CIP circuit.

Jan 1, 1983

By W. H. Strickland

The research reported here characterizes ultrasonic ranging sensors for autonomous navigation on underground mine mobile equipment. Because ultrasonic rangers are inexpensive, have no moving parts, have no lenses to clean, are small and unobtrusive, and can measure distances in dusty environments, they are especially sui ted to underground mi ne environments. The investigation began with laboratory tests of field of view, angle of incidence, intersensor variation, and ranging accuracy of individual rangers and a ring array of 24 sensors. The results showed the sensors have good accuracy and low variability. Additional experiments at AHAX' s Henderson mine Showed the sensors could accurately and reliably measure rib features, convex and concave corners, and drift intersections. The results showed that when used and analyzed properly, the sensor data may be used reliably for underground mobile equipment navigation.

Jan 1, 1990

By L. H. E. Weyher

A mine is essentially a vast materials-handling system. All other systems found in the mine exist to one degree or another to support the materials-handling functions, from the cutting at the face to the hoisting in the shaft. In this chapter computerized planning of underground materials-handling systems will be examined by dividing this function into: (1) the planning of the production section, and (2) the planning of underground rail or belt haulage from the production section to the shaft, slope, or surface. While alternative divisions might focus on the different materials- handling functions, i.e., production, supply, and manpower transportation, historical computer analysis has focused on the various systems rather than functions. The emphasis in this chapter is directed toward coal mine applications; however, most of the programs and methods are equally applicable to other underground mines. Markedly different methods are encountered in each system, and moreover, marked differences exist in the nature and the degree to which the materials-handling subsystems in each interact with the environmental or support systems. The most intimate interaction exists at the faces where geologic, human, and machine performance factors are closely related and constantly varying. In view of this, the planning of the materials-handling systems for the face will usually stress flexibility, while the outby materials-handling systems will generally place decreasing emphasis on flexibility and more on system reliability, capacity, and cost effectiveness. Thus, hoisting and main haulage systems are generally designed and constructed as permanent installations and cannot be readily changed, whereas secondary haulage systems and face operations are relatively mobile. These differences may have considerable significance for the mine planner in making technical and financial comparisons of alternatives to provide the scheduled mine production.

Jan 1, 1979

By A. V. Castelli

Since the record year of 1981 through 1985 the tonnage of weighting materials (barite and other heavy minerals) used in drilling fluids has decreased an estimated 49%. As in the past, barite still makes up over 90% of the minerals used for weighting materials in drilling fluid. Domestic production of barite has decreased 69% since 1981 and imported barite has made up over 50% of the total barite consumed since 1982. See Figure 1 for usage of barite. The number of operating grinding plants has decreased from 69 in 1982 to 39 at the end of 1985. With the decrease in demand of weighting materials for drilling fluids and an over capacity of grinding existing, prices for weighting materials have decreased dramatically. Although the American Petroleum Institute has not changed any of the specifications for barite, some users have initiated their own new specifications and have proposed to have them included in the API specifications. The exploration for and development of oil and gas dictates the level of weighting material used in the drilling fluids industry. Most forecasters do not foresee (or predict) increases in the level of drilling until the 90's. The primary or unground barite produced in the U.S. mines has a difficult time competing with imported barite due to the location of the mines. These mines are located in North Central Nevada, with small tonnages being produced in California, Missouri, Illinois, Montana and Washington. The major reason, is the difference in transportation costs from the mines versus ocean freight rates from the foreign ports to the major area of use, the U.S. Gulf. Since 1981, the production of primary barite has decreased from 2,849,000/ST (2,584,596/MT) in 1981 to an estimated 890,000/ ST (807,403/MT) in 1985(1). If it were not for the use of unit trains by some producers the production of primary barite in the U.S. would have probably declined another 20% in 1985. During the same period, of the total amount of barite consumed in the U.S., imported barite ore increased from 417, in 1981 to 65% in 1985. The major exporting countries to the U.S. during this period were China 46.27, Morocco 15.27., Chile 10%, Peru 8.4%, India 7.9%, Mexico 5.4%, Thailand 3.9% and Ireland 2.3%.

Jan 1, 1986

By Gerrit V. R. Goodman, Edward F. Divers, Charles D. Taylor

Future mining systems will possess the ability to cut from crosscut to crosscut where advances could exceed 30.5 m (100ft). However, limitations arise when ventilating such mining systems. In deep advance mining, there will be no workers at the face to manually advance ventilation tubing or curtain. Additionally, traditional methods provide no means for maintaining face ventilation after the miner backs out. Problems such as these have suggested the need for innovative ventilation methods compatible with deep advance mining systems. The Bureau of Mines is currently considering a number of innovative ventilation schemes. One such method is the use of a jet fan to ventilate a deep cut. A jet fan is simply a freestanding fan using little or no ducting to direct the ventilation flow. Previous testing in large metal-nonmetal mine entries showed that jet fans provided adequate face ventilation for deep advances in large headings. Current testing will determine the application of jet fans in ventilating smaller coal mine entries. Another approach considered compatible with deep advance mining will use either exhausting or blowing tubing that can be remotely extended from crosscut to crosscut. During the mining cycle, such a device would extend automatically as the miner sumps into the face. The Bureau of Mines is considering several different operating designs using this tubing.

Jan 1, 1991

By J. F. Brune

This paper analyzes the explosion hazard resulting from the formation of methane-air mixtures in the mined-out gobs of underground longwall coal mines. Although direct examinations of the gob atmosphere are difficult due to the inaccessibility of these gobs, evidence from methane drainage practices and investigations of numerous mine explosions suggests that explosive methane zones can form within longwall gobs. Explosions and fires resulting from these methane accumulations have led to severe and fatal injuries to the miners. Most recently, this was demonstrated in the explosion of the Upper Big Branch Mine in West Virginia, where 29 miners lost their lives.The paper also reviews current research on numerical modeling of gas flows in longwall gobs and outlines how targeted injection of nitrogen into gobs can effectively reduce the volume of such explosive methane zones. The paper concludes that comprehensive monitoring of gas compositions, along the accessible fringes of the gobs along with inertization, improved ventilation schemes and further research are necessary to control this explosion hazard and make mining operations safe.

Jan 1, 2013

By Jaime Adasme, Héctor González, Benjamín Celada

"INTRODUCTION Santiago de Chile is a 7 million inhabitant city which has a 103 Km long subway network operated since 1975 by Metro S.A. This network is used on a daily basis by 2.3 million people. In 2012 Metro S.A. started the biggest enlargement of the network in its history, through the design and construction of the new Line 3 (21.7 Km) and Line 6 (16.5 Km). The detailed engineering contract for civil underground works of Line 6 (L6) was awarded to the Consortium integrated by ZAÑARTU Ingenieros Consultores and GEOCONTROL S.A., in which Geocontrol was in charge of the design of 11 stations and 14.5 Km of tunnel. L6 crosses L3 in Ñuble and Ñuñoa Station, L2 at Franklin Station and ends, intersecting L1, at Los Leones Station as shown in Figure 1. LOS LEONES STATION DESIGN Location and Characteristics Los Leones Station is placed at the North end of the L6, next to the same named station of the L1 and it has four construction units, as is shown in Figure 2: I. Access Shaft (49 m x 47 m). II. Access Gallery (34 m long). III. Station Tunnel (120 m long). IV. Connection Gallery with L1 (104 m long). A singular feature of Los Leones is that the western section of the station tunnel, built from the access gallery, is located below an underground parking lot which is located in Providencia Avenue, as shown in Figure 3. It is important to highlight that the distance between the vault of Los Leones Station Tunnel and the foundations of the underground parking lot is only 6 m."

Jan 1, 2016