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By C. L. Sarff

[Automation has become a word that means many things. To management it is the end of the rainbow; you push a button and all your problems are solved. To the working man it is a horrible monster that is taking his livelihood away. To the maintenance man it is a complex that overwhelms him when he thinks of trying to find the trouble when the machine is not operating, properly. Automation has been with us in the coal nines for many years. Long before my time you were using float switches on mine sumps to control the level of the water. That?s automation in the truest sense of the word, but we call it automatic and think nothing of it. If we use the word automatic instead of automation your mine electrician and mechanic will take hold of the problems in stride.]

Jan 1, 1962

By J. N. Albright

Both microgravimetry and crosshole seismic tomography are means by which subsurface collapse and rock failure may be observed. We show results of calculations that predict changes in gravity and gravity gradient that result from void migration, bulking, and hydrology disruption due to room and pillar mining. Crosshole seismic tomography also holds promise for detecting and mapping changes in structure during subsidence. Commercially avail- able logging tools, advances in theory, and recent field results strongly suggest tomographic surveys are now possible. Subsidence phenomena which may be located are faulting, joint separation, bed parting, water table changes, and formation outgassing.

Jan 1, 1982

By James W. Derrick

General widespread interest in fine coal cleaning circuits did not occur in the United States until the mid 1960's. Up until this period the relatively low price for which bituminous coal was sold did not justify for many operators the capital and maintenance costs associated with the beneficiation and drying of fine coal. However, with current growing interest in this area, the introduction of new types of process equipment along with modifications to existing components is occuring to maximize the recovery of coal fines. In 1973 Derrick Manufacturing Corporation introduced high frequency screening machinery into the coal industry. The first design consisted of a 4 ft. wide 18 ft. long single deck screen frame with three 100 mesh woven wire screen surfaces divided by repulping troughs for the addition of wash water. In addition, a special slotted rubber dewatering deck was installed on the discharge end of the unit to assure adequate dewatering of the screen oversize. This panel had nominal 25 mesh X 3.0" slotted openings. The machine was also equipped with a special high speed-low amplitude (3600 RPM .032" % AMP.) integral vibrator.

Jan 1, 1983

By K. L. Whitehead, R. A. Jankowski, N. I. Jayaraman

Most continuous miner sections utilizing flooded-bed scrubbers also use blowing face ventilation. Blowing ventilation, however, interferes with dust capture and minimizes scrubber effectiveness. To enhance the efficiency of the scrubber system and reduce dust concentrations, the Bureau of Mines tested various combinations of operating parameters. Experiments for system efficiency took place in a full- scale model mine at 3.05 m roof height. In general, higher values for scrubber and face airflows resulted in lower dust concentrations. In addition, optimum dust controls would include a face ventilation to scrubber airflow ratio of one. When the airflow ratio was either less than or greater than one, the dust levels in the return and at the operator locations increased. No single dust control technique was the most effective one at all locations due to mutual interaction among techniques.

Jan 1, 1992

By P. A. Rittenhouse

Reserves of potash are more than adequate to meet future world demand for this primary fertilizer nutrient. The bulk of both reserves and current production is located in only a few countries. Recent attention has focused on potential development of smaller reserves to supply local markets in developing areas of the world. However, most new capacity in the next decade will be built in countries with large current production and reserves. The paper reviews current and future projects that will add to the world supply of potash.

Jan 1, 1985

By Niels Jonassen

INTRODUCTION The occurrence of the radioactive element radium, [2gg~a], often in trace amounts, in the crust of the earth gives rise to a flux of the daughter product radon, ['ii~n], across the earth-air interface. This so-called exhalation process has been studied by many investigators [KO 45, Kra 64, Pe 66, Wi 741] over several decades. In the earlier investigations the exhalation process was studied in a purely geophysical context, but over the last 20 years it has been realized, that under certain conditions the exhalation may be intense enough to also have radiological implications. This is for example the case where relatively radium-rich wastes or by-products, like uranium mill tailings and phospho-gypsum, are stored in larger quantities. In order to be able to predict the radiological impact on the environnent it is necessary to know the rate of exhalation of radon from the surface of the exhaling material. Usually the determination of these exhalation rates has been done by measurements in situ directly upon the accumulated material [~le 74, Ha 791. Although such field measurements have the obvious merit of dealing directly with the full scale problem, the results are often lacking in generality, making predictions for other situations difficult or even impossible. The present paper describes some results of an investigation where it is attempted from laboratory measurements on samples of limited size to obtain material parameters, which are suited for extrapolating and predicting the radiational behaviour of larger accumulations of the material. THEORY Let us consider a sample of a radon exhaling material enclosed in a container with a dead space volume, Vd, and initially containing radon free air. If the total exhalation rate (number of atoms per unit time) is c, the radon concentration (number of atoms per unit volume) N will initially grow with the time t according to the equation [ ] where [R] is the decay constant of radon. As the concentration (or activity) in the container grows, the net exhalation rate will slow down because of back diffusion, and, furthermore, radon atoms may be removed from the container, not only by radioactive decay, but also by diffusion leakage [JO 81 ]. If, however,only the initial. part of the activity growth curve is considered, the total exhalation rate, c, is given by [c = r•Vd(2) where r is the initial activity growth rate in the container. Let the container be cylindrical with an inner cross-section S and filled to a height L with a radon exhaling material with the specific mass p, the porosity E, the radon pore production rate f and the diffusion length i. When the container is left open,i.e. the radon exhalation takes place into a virtually radon free room, the radon area exhalation rate, E, can be written [Jo 80] E = Ef?t tanh L.R (3) assuming the exhalation only takes place in one direction, towards the surface of the material. It appears that for values of L > 2•ithe area exhalation rate becomes E a = Efi (4) independently of the sample dimensions and the total exhalation rate c is then c = E •S (5) For L ;~ 0.5•i, tanh P _ k and equation (3) may be written E ~ EfL (6) then c = EfL•S = p•m= Em •m (7) where m is the mass of the sample and Em = P (8) is the mass exhalation rate. It thus appears that the radon exhalation rate from a given amount of material may often be conveniently expressed by c = E •Sfor L z 2•I (5) a orc = Em •mfor L0.5•i (7) where S is the total exhaling area and m the total exhaling mass, E and E the area and mass exhalation rates respectively defined by equations (4) and (8).]

Jan 1, 1981

By J. A. Nelen, R. B. Cook

Panned stream-sediment, geochemistry-based gold exploration in those parts of the southeastern Piedmont proximal to the Fall Line must take into account potential contamination from basal fluvial sediments of the Coastal Plain. Anomalies attributable to the incorporation of placer gold of Coastal Plain origin into modern Piedmont drainages have been identified in portions of Lee, Macon, and Tallapoosa Counties, AL, and Baldwin and Hancock Counties, GA. Identification and interpretation of such multicyclic anomalies must be based on knowledge of the local maximum Cretaceous transgression, paleotopography, modern and paleofluvial system dynamics, and fineness trends and Au-Ag zoning in gold grains.

Jan 1, 1990

By J. B. Cabezas

The metallurgical processes that are frequently applied today use strong solutions and are of alkaline, acidic, or organic nature. These play a very important part in recovery of values from many ores. These solutions are of such a chemical nature that they are generally corrosive, flammable, and contaminating. In most cases, they are highly dangerous to the environment. Within the extractive metallurgical industry, it is also very common to have to deal with the handling of contaminating solutions with a high content of cyanide, arsenic, mercury, lead, copper kerosene, acid and many other components whose temporary or permanent confinement within the process must be adequate and absolute.

Jan 1, 1986

By Ahmet Gursoy

Maryland, will be the widest vehicular tunnel ever built by the trench tube method. Careful coordination and planning were required to meet the tight and fast design and construction schedules. During the preliminary design, traditional design drawings were bypassed in favor of 25 preliminary design reports representing major work breakdown structures (tasks). For each task, alternative design solutions were examined and analyzed by means of trade-off studies on the basis of engineering, constructibility, and economic considerations, thus providing an overall conceptual value engineering approach for the entire project. So far, total value engineering proposed by the contractor for Contract I I (largest contract of the project at $245 million) is less than 1.5 percent of the contract value. This is an important indication of the success of the design phase planning.

Jan 1, 1983

By A. K. Bakshi

Slurry rheology affects autogenous grinding performance by changing the rock's breakage characteristics. In this study pilot scale batch autogenous grinding was carried out to observe the effect of viscosity on the breakage characteristics of the rocks (the media), and on the overall specific energy consumption. Clay/fines content, and temperature of the initial charge, were varied to alter the viscosity of the slurry. Results showed that at higher slurry viscosity, rocks became more difficult to break, resulting in an overall increase in the specific energy consumption of the mill. Also, it was observed that viscosity had a significant effect on the amount of critical size material present in the grinding circuit, where the critical size material is the material which is too large to be effectively ground in the mill, and too fine to act as grinding media.

Jan 1, 1996

By C. D. Mann

INTRODUCTION The sublevel stoping mining method is usually applied to a relatively steeply dipping, competent ore body, surrounded by competent wall rock. Ore is produced by drilling and blasting longholes, which can range from 50 mm (2 in.) to 200 mm (7% in.) diam, with lengths up to 90 m (300 ft). Longholes can be inclined in any direction, but the ring or pattern usually forms a plane, and the holes are blasted as a unit. Recently developed mobile drilling and loading machinery, as well as new explosives products, blasting techniques, and cemented sand and rock fill have made sublevel stoping a highly efficient and versatile mining method. When designing a sublevel stoping production sys- tem, it should be kept in mind that production rates from conventional sublevel stopes vary widely through- out the life of the stope. Early production is at a low rate, coming only from the drawpoints near the slot, but increases as new drawpoints are reached by the stope face. As the stope nears completion, again, fewer drawpoints are productive. Enough drawpoints must be available at any time to provide required production. Drawpoint availability should be compared to equipment availability; plan for more drawpoints than are needed at any one time. Accurate, realistic scheduling is essential to smooth production rates. Also, initial recovery of ore in a stope/pillar block is normally from 35% to 50% in sublevel stoping. Planning of pillar recovery, representing the majority of ore tonnage in a production block, must be done during early mine planning. Since much of the development already done for primary stoping (access for drilling, drawpoints, and haulageways), can be used for pillar recovery, early production from pillars is highly desirable. The following description of components of the system is an attempt to highlight some of the most important features and requirements of mechanized sublevel stoping methods. Similar comments would apply to the use of older equipment (column-and-arm drill setups, slushers, etc.) in similar methods. As in any good mining system, maximum economic recovery of the resource in the ground is the primary consideration. STOPE DESIGN CHARACTERISTICS Length and Width The following are some of the factors which affect sublevel open stope length and width dimensions: ore body geometry, principal stress directions, competence of stope back, optimum drill pattern, and drilling drift layout. In new mines initial stope layout design may occur before the ore body is actually intersected by mine workings. Stope dimensioning is a critical decision, and assistance from as many knowledgeable people as possible at this stage is essential. Operators with past experience in similar ore bodies, rock mechanics experts, and others with mine design experience should participate at this stage of stope planning. Height The following are some of the factors which must be considered in determining stope height: competence of stope pillar and stope/fill walls; slenderness ratio of adjacent pillars; ore body dip; ore body thickness; hole depth capability of the drilling machine; fragmentation characteristics of the ore; and level intervals in existing mines. In competent ground, drill-hole length and accuracy are the most important determinants of stoping height. Frequently entire drilling sublevels can be eliminated because of the depth capability of sophisticated drilling equipment, resulting in significant development cost savings. Drawpoint Location and Design Some of the most important considerations of a good drawpoint system are optimum spacing of draw- points, within the constraints of stope dimensions, for uniform drawdown and maximum recovery; excavations designed for stability for the life of the ore block to be drawn-primary stope ore as well as subsequent pillar ore; floor or roadway design including type of surface, reinforcing, grade for water runoff; orientation with respect to the main haulageway, for optimum loader maneuverability and ground stability at the inter- section; and length, to allow articulated front-end loaders to work in a straight configuration. Careful drawpoint design and construction are keys to successful production. Extra care in development, such as smooth wall blasting, rockbolts or grouted rebar, wire mesh, and shotcrete usually will ensure long draw- point life. Human exposure during production loading is of longer duration than during development or production drilling, and consequently preparation of draw- points is easily justified, particularly when pillar ore can be drawn through the same drawpoints. Secondary blasting of boulders can weaken drawpoints, also justifying good ground control techniques. A smooth draw- point floor of poured, reinforced concrete, on a grade of +3% or +4% toward the ore pile facilitates water flow out of the drawpoint, and ease of loader bucket penetration into the muck pile. Slot Raising, Slotting A slot or other space for rock expansion is necessary in conventional sublevel stoping where vertical rings or rows of holes are blasted. The slot can be started at a slot raise driven by conventional raising methods, raise boring, drop raising (predrilling and blasting a raise from the top, using small diameter-less than 200-mm (7%-in.)-holes for relief), or crater blasting (similar to drop raising, but without relief holes). The slot usually extends from the extraction level to the back of the stope. It is normally expanded to full stope width by

Jan 1, 1982

By James P. Morris, William H. Hansmire

The U. S. Department of Energy's (DOE) Yucca Mountain Project (YMP) is a scientific endeavor to determine the suitability of Yucca Mountain for the first long term, high level nuclear waste repository in the United States. The status of this long-term project from the construction perspective is described. A key element is construction of the Exploratory Studies Facility (ESF), which is being excavated with a 7.6 m (25 ft) diameter tunnel boring machine (TBM). Development of the ESF may include the excavation of over 15 km (9.3 mi) of tunnel varying in size from 3 to 7.6 m (10 to 25 ft). Prior to construction, extensive constructibility reviews were an interactive part of the final design. The intent was to establish a constructible design that met the long-term stability requirements for radiological safety of a future repository while maintaining flexibility for the scientific investigations and acceptable tunneling productivity.

Jan 1, 1995

By L. B. Paterson

Mining Engineers throughout the world have an appreciation for the importance of the role of the Blasthole Drill in one of the primary elements of the mining process. This paper highlights areas that could influence the overall cost effectiveness of that process of breaking rock and how equipment is designed and configured to meet that challenge. Factors influencing drill productivity and overall cost effectiveness are addressed, both in the Mine Environment and on the Blasthole Drill.

Jan 1, 1999

By Takuya Tani, Tomoyuki Aoki, Kazuo Saskai

"The authors have proposed a unique methodology in the evaluation of rock mass stiffness for the range of five to twenty meters ahead of the tunnel face, with the use of small diameter inclinometers. The inclinometers are installed at the tunnel crown at a pre-determined constant interval, about one meter behind the face in order to obtain the slight change in inclination angles during tunnel excavation. This method was developed as a daily control measurement such that the geological condition and its possible change ahead of the face could be detected early by monitoring the trend of inclination angles. This paper describes the results of the ground stiffness ahead of the tunnel face evaluated at a mountain tunnel construction site. This stiffness is evaluated automatically and displayed visually by the current system equipped with a result display screen, together with a warning message against a weak zone when detected. 1. INTRODUCTION In a conventional planning of a mountain tunnel, according to the Japanese Standard (JSCE, 2006) seismic refraction surveys from the ground surface are performed and tunnel support patterns are then designed based on the seismic wave velocity. The resolution of the velocity profile estimated by this technique, however, is poor as the tunnel overburden becomes large. The tunnel face is therefore often encountered by unforeseeable fault zones or weak rocks. Such an unpredictable weak zone occasionally causes the collapse of the tunnel face. Clarifying the forward geological information during excavation is hence significant for safe and well-controlled construction. According to the geological conditions ahead of a face, auxiliary methods typified by forepiling and face bolting could be preliminarily prepared for prompt execution. For the purpose of acquiring forward geological information, pilot borehole drilling and seismic reflection methods represented by the TSP (Tunnel Seismic Prediction) or HSP (Horizontal Seismic Profiling) are often applied. Those exploration are carried out near the tunnel face for a couple of days. This often leads to the interruption of excavation procedure and has no small effect on the construction schedule. On the other hand, some forward ground prediction methods in the daily control measurement have been developed e.g. by Schubert et al. (1995). In this method, tunnel displacements in the direction of the tunnel axis are used together with the crown settlements. We have tested their method at a few of our tunnel projects and found difficulty in the evaluation of the forward ground condition due to insufficient resolution of the axial displacement measured by a total station theodolite that we usually use for the tunnel measurement. We have therefore developed a novel methodology of monitoring slight inclination at the tunnel crown near the face, so that the forward ground conditions can be predicted and evaluated as part of a routine measurement procedure."

Jan 1, 2016

If it had not been for the almost unbelievable adventures that came before and after, the last ten months of 19 15 would have been exciting enough for anyone. As it was they were a cheerful interlude. I spent most of the time on our Warren operations catching up on a lot of underground work and visiting Ajo every few weeks to see if my Chuquicamata visit might help solve the New Cornelia problem. While the difficulties were finally solved, at times they seemed almost hopeless. About all I could do to help was to make sure that the ore sent to the pilot plants represented the average ore that must be treated in the final 5000 tpd mill. Dr. Ricketts and John Greenway worked tirelessly with the best consulting advice they could obtain. Credit for the final success was due chiefly to their efforts. Since our old group had given up its "Merry Widow" home in Warren, a few of us got rooms in the company-built Cole Building over the Warren grocery store. This included Jim Lewis, Roy Mitchell, Steve Landon, Paul Stevens, and Hubert d'Autremont who came from Duluth to join our legal staff. Later we rented a small house two blocks from the Calumet and Arizona office. With the now flourishing country club only a 10-min walk away, and an electric car running to it every half hour or so, we were able to give parties in return for the hospitality of our friends. One of the most pleasant episodes came by luck a few days after I got back from Chile. Chester Congdon, a leading director in Calumet and Arizona, with his wife and their daughters, Elizabeth and Helen, spent a couple of days at the Greenway house before making an auto- mobile trip across the desert from Tucson to Ajo. At the same time I arranged to examine the small but rich Bush and Baxter copper mine a few miles from Tucson. At a party in Warren we found we would all be staying at the Santa Rita Hotel in Tucson, and I took my South

Jan 1, 1976

By Y. J. Wang

The Hardy Cross iterative method is the most popular technique for solving a ventilation network problem with natural air splitting. This method tradition-ally solves each mesh equation by an approximation during each iteration. It is thus interesting from both theoretical and computational viewpoints to be able to solve for an exact solution to the mesh equation. Presented in this paper is an algorithm for computing the exact solution to the mesh equation with a variable fan pressure. The algorithm uses signum functions for air quantities to generate an alternative mesh equation in the form of a quadratic equation, which has two solutions defined by the well-known quadratic formula. The condition that the derivatives of the alternative and the original equations must be the same provides a basis for the correct choice between the two solutions.

Jan 1, 1997

By Jianguo Hao, Qingbiao Zhao, Bingnan Hu, Shimin Fan

The paper makes a systematic analysis of interaction between backfill and pillar in coal mining. It compares the difference of pillar strength with backfill and without backfill. It is proved that there are the obvious improvements in pillar strength and the decrease in subsidence. It discusses the subsidence effects of different extraction ratio, different backfill ratio, and different elastic modulus ratio in details. The paper analyses the sensitivity by orthogonal test method. At last, author proposes some suggestion to increase pillar strength, to reduce subsidence, and to guide engineering practices.

Jan 1, 2001

By George J. Allen, Laura A. Allen

Introduction This section of the text presents a general review of the different types of concentrate marketing contracts. Too often the marketing strategy is ignored in the design phase of the project and the producer is left to the mercy of the buyer. Many items such as concentrate grade, impurity levels and moisture content of the concentrate my enhance, or severely restrict the producers ability to make a profit it. Close attention should be paid to the design of the concentrator which can improve the quality of the concentrates, thus the ability to increase the rider of potential buyers can be enhanced. Difficult at best, is the position of the miner who only has one outlet available for its production. Obviously, the trade offs must be evaluated. For example, concentrate grade vs recovery and grind/filtering capacity vs moisture of the concentrate all must be weighted against freight cost to a potential buyer. In addition, the above considerations must be weighed against the capital cost to the miner. This chapter is intended to highlight important articles that are included in short and long term agreements and to give a new miner/producer some insight into hat my or my not add value to the product. Unless the miner sells the product directly to a consumer such as a gold, or silver producer, or to a large enough operation that has a totally intergrated system to make a finished product, most miners are forced to sell to buyers who ultimately will refine and market the product. Types of Contract Agreements There are many types of contract agreements just as there are colors in the rainbow, however, most contracts fall into three basic categories. (1) Smelter Schedules: Designed for the small producer, the odd lot of concentrate, smelter flux and precious metal ore. Albeit custom smelters are becoming fever by the day, because of pollution control requirements and financial difficulties, most remaining custom smelters have a smelter schedule. A smelter schedule is a posted list of charges and conditions that the smelter will buy material from a seller. Smelter schedules exist for copper, lead, zinc, silver and gold (Handbook for Small Mining Enterprises, Montana Bureau of Mines). (2) Short Term Custom Contracts: Large mine producers frequently use Short Term Contracts where the seller has the buyer frame a contract that is tailored to the sellers’ production. The short term contract my be as long as one year. A spot sale qualifes as a

Jan 1, 1986

By O. Alvarez-Campos

Two porphyry copper orebodies, the North and Central MM orebodies, have been found through regional and structural geologic works, about 5 Km south of Chuquicamata, under a gravel bed of approximately 100 m and in the west side of the West Fissure. The mineralization is emplaced in a coarse granodioritic porphyry, predominantly with sericitic alteration. In the North MM ore-body, with 200 million metric tons of 1.0% Cu, the mineralization is mainly chalcopyrite, bornite, digenite and molibdenite. In the central MM orebody, with 700 million metric tons of 1.3% Cu, there are large veins of enargite, chalcocite and bornite, the last one increasing in depth, separated by chalcopyrite and pyrite zones; in these veins there are interesting gold and silver values. Both orebodies have an upper enrichment of chalcocite and covellite, with pyrite envelope. According with these characteristics, the MM orebodies could he the upper part, with sericitic alteration, of the Chuquicamata porphyry copper system, displaced by the West Fissure system movements, but we couldn't eliminate the possibility that MM can be a new orebody, different of Chuquicamata.

Jan 1, 1993

By J. Um, B. Morin, P. H. S. W. Kulatilake

Development of a three-dimensional mine visualization model for a section of the mine is addressed first. Discontinuity orientation and location information was taken from this visualization model for use in slope stability analyses. Estimated shear strength properties of discontinuities and mechanical properties of intact rock from the rock mass samples obtained from the mine are discussed next. The paper is then focused on the calculated maximum safe slope angles based on the performed kinematic and block theory analyses using the mapped discontinuities at the mine. Finally, the effects of water that exist in the rock mass, tension cracks, slope face inclination, overall wedge height and double benching on factor of safety of wedge stability are illustrated through limit equilibrium slope stability analyses.

Jan 1, 2002