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By P. Tsang

The stability of longwall chain pillars depends not only on the mechanical properties of coal and surrounding rocks, but also geological and mining conditions. In order to evaluate the effects of each, variable, the orthogonal experiment design was employed in this study for significance analysis. The study concluded that the stability of longwall chain pillars is mainly controlled by the ratio of pillar stress to pillar strength, the ratio of Young's moduluds of the roof to coal and floor to coal, entry width, pillar width and the internal friction angle of coal. Additionally, horizontal stress, panel width and mining height also play a significant role.

Jan 1, 1994

By B. C. B. Pretorius

A heat load analysis of the very hot sub-shaft area of Loraine gold mine situated near Welkom, South Africa, showed. that the heat that needed to be removed to give acceptable wet-bulb temperatures at the working faces could not be done by the normal ventilation air alone, but would have to be complemented with extensive refrigeration. The paper outlines the considerations in selecting the cooling system adopted for this shaft.

Jan 1, 1980

By K. J. Henderson

INTRODUCTION Shrinkage mining at Inco Ltd.'s Crean Hill mine can best be defined as a horizontal breasting method utilizing the broken ore for the mining floor and to provide wall support, with draw from a series of boxholes or draw¬points at the base of the stoping block. In choosing to shrink a given block of ore, the initial investigation centers on the ore configuration and grade, the expected ground conditions in the stoping area, the expected profit compared to alternative mining methods, the future production requirements, development lead time, the availability and type of equipment in the area, and the availability of experienced miners. These factors are weighed against other mining methods and shrinkage mining is chosen when the advantages outweigh the dis¬advantages. These will be discussed in more detail later. At Inco Ltd.'s Crean Hill mine, shrinkage mining makes up 17% of total mine production and is decreasing due to the advent of advanced blasthole techniques, notably in-the-hole drilling. Shrinkage is an adaptable mining method that is currently employed in narrow irregular ore zones, as undercuts for in-the-hole blast¬hole stopes, in ore bodies that do not extend from level to level, and in areas where quick production is required with a minimum of capital outlay or minimum develop¬ment. Two major types are currently in use which are classified on the basis of type of draw system employed. These are the utilization of load-haul-dump (LHD) equipment drawing from drawpoints, and the slusher and train method drawing from boxholes into a slusher trench and loading into a train. A third method being phased out is drawing from chutes directly into a train. In all three methods the actual stoping operation remains the same. In the initial planning of a mining block, the ore body is first located using an exploration diamond drill¬ing program. This is essentially done at a 130-m (400¬ft) spacing and it gives an indication of the amount of ore, grade of ore, the configuration of the ore body, as well as other geological features such as ground condi¬tions which will affect future mining. This drilling is done from an exploration drift 165 m (500 ft) long in the hanging wall and covers a vertical extent of 330 to 670 m (1000 to 2000 ft). However, these data are not accurate enough for detailed planning. When the de¬cision has been made to mine, a preliminary develop¬ment drill drift is driven in such a position that it can serve the dual purposes of allowing the ore body to be drilled off in detail, or of later serving as a haulage or access drift. Diamond drilling from this drift is usually on a 15-m (50-ft) grid spacing and gives adequate information for detailed planning. Utilizing the drill data, a decision is made on the mining type. For a shrinkage operation, the stoping block is ideally 49 m (150 ft) in length and a maximum of 13 m (40 ft) in width. Lengths of 65 m (200 ft) are considered a practical maximum because of the length of time the back of the stope remains open during the min¬ing of a cut. A minimum length of 13 m (40 ft) is used because the amount of time spent in opening a new cut increases in comparison with the total stoping time. The maximum width of 13 m (40 ft) is used because ex¬perience with the ground indicates that generally stope backs tend to be unstable over greater widths. However, widths of 33 m (100 ft) have been mined. A minimum width of 5 m (15 ft) is used to allow an effective draw, but in unusual cases, a width of 3 m (10 ft) has been mined successfully. The dip of the ore should not be less than 1.04 rad (60°). Angles flatter than this will not pull properly resulting in inefficient mining because of ore hang-ups on the footwall side of the stope and the need for large stagings on the hanging wall. In considering shrinkage, mining ground conditions play an important role. Strong shearing, cross faulting, or dikes are avoided. These usually cause dangerous mining conditions and an alternative safer mining method which will give adequate support to these adverse ground conditions is employed. Production requirements are taken into considera¬tion when planning a shrinkage mining program. In it¬self, shrinkage mining is capable of producing ore in a relatively short time with little capital development. If quick production is required, this method can produce ore rapidly as all that is required is that the draw system be completed and the miners with jacklegs and stopers produce a limited amount of ore. The obvious disadvan¬tage is that not all the ore broken can be pulled from the stope immediately. However, a mining horizon with sev¬eral shrinkage stopes in different stages of production can adequately maintain scheduled tonnage require¬ments, the cycle being stopes under development, stopes actively mining, and stopes completed and pulling. When the decision has been made to use shrinkage mining in a given block, the haulage and draw system is driven. The proximity of the orepass system dictates whether the system is to be a LHD operation or a slusher trench operation. If the orepass system is in close prox¬imity to the stoping block, LHD equipment is employed because of its ability to operate efficiently over short haulage distances. A long tram to the orepass usually dictates a slusher trench operation with haulage by train. Internal orepass systems are used effectively with LHD equipment with a load-out and retramming taking place on a lower horizon. In addition, stoping blocks in older areas of the mine are developed track because of the capital cost involved in converting an existing level to trackless mining. DRIFT DEVELOPMENT USING LHD EQUIPMENT The haulage drift for a draw system using LHD equipment is driven parallel to the ore body in the foot¬wall at a sufficient distance to allow an 11.5-m (35-ft) drawpoint to be driven into the ore (Fig. 1). The actual position of the drift depends entirely upon the ore con¬figuration and the drift size depends on the equipment to be used. Drift sizes of 4.6 x 4.1 m (14 x 121/2 ft) for an St-4 and 3.8 x 3.6 m (111/2 x 11 ft) for an St-2 meet company and government clearance standards and allow sufficient space to accommodate a ventilation pipe. The

Jan 1, 1982

By L. G. Austin, R. S. C. Rogers

INTRODUCTION Coal is geologically a sedimentary rock with distinct bedding planes containing a mixture of petrographic constituents. Yet. because of its chemical nature, it also has some of the characteristics of a polymeric material. In addition, it is extensively precracked to give a macropore structure and also has a substantial internal volume of microporosity. Add to this the mineral constituents dispersed in the coal in a variety of forms and sizes. and it can be readily appreciated that coal is a complex and heterogeneous material. It has to date not been possible to predict the particle size distributions produced by breakage of coals from a priori application of the principles of fracture mechanics. However, there is a substantial body of data resulting from empirical observation of size distributions produced under various conditions, primarily from grinding mills. It is the function of this review to outline how this empirical information can be used to predict product size distributions for those systems which have been studied systematically, and to suggest future avenues of research using similar methodology. FRACTURE THEORY APPLIED TO COAL It is, of course, possible to devise experiments for slow crack propagation in a coal. However, the evidence is that coal breaks by brittle fracture in the mills and mining machines of industrial importance and therefore the theory of brittle fracture is sufficient to illustrate the important features of the fracture of coal. In order to produce size reduction a solid must be stressed by the application of force. The force can be a tensile (stretching), compressive, or shear force, and the three dimensional stress pattern in the solid represents the tensile, compressive, and shear forces per unit area acting in any direction through any point in the solid. As an illustration consider the case of a simple one-dimensional tensile stress: then stress is defined as a=F/A where F is the force. A is the cross-sectional area of the solid normal to F and strain. E, is defined as the fractional change in the length of the solid. so that E= x/L where x is the extension of an original length of L. Coal behaves as an elastic material over short times (although viscoelastic creep can occur if the stress is maintained over long times) and if it is not stretched too far the coal returns to its original shape when the stress is removed; otherwise catastrophic failure occurs and the coal fractures at a stress termed the tensile strength. The failure under stress of an elastic material is termed brittle fracture. Elastic material fails at small stain and the stress-stain relation to where brittle fracture occurs is the empirical Hooke's law. a= YE, where Y is Young's modulus. The work done on the solid to take the solid from zero external stress to a stressed state by slowly increasing F up to a final stress u is the integral of the stress times the strain. This reversible strain energy is stored in the solid and. using Hooke's law. is u /2Y per unit volume of solid. If the solid is immediately loaded to u the work done is [EAuL] which Is a2 /Y per unit volume, that is, twice the reversible work.

Jan 1, 1988

By K. S. Olson

My reaction when first asked to present this paper was; "What could I possibly say that would hold the audience?s attention for 15 minutes? What could I offer that anyone familiar with the Nevada Barite Industry wouldn't already know?" Well, quite frankly I can't. The industry has certainly been anything but exciting for the past 10 years and, in fact, quite depressing. The challenge, for those few of us left in it, has been to keep it alive. At times it has felt like a doctor must feel with a terminally ill patient. All I can do is recap the past ten years, review the present state of the industry, and offer a few personal opinions and observations as to where I think we are headed.

Jan 1, 1993

By James F. Holzbach

Although Disputes Review Boards have been used for some time, they had not received wide publicity at the time Monroe County first used one. Public owners frequently resist adopting new contracting practices. This paper discusses an owner's experience with Dispute Review Boards, from learning about them to their use on two (2) projects. The experiences of potential and actual contractor claims are compared to a claim on an earlier contract and the ensuing litigation. Suggestions for possible use for Owner-Engineer disputes and recommendations for use are provided.

Jan 1, 1995

By Lee S. Richardson

Silicon is usually considered to be a useful metallic alloying element. To be more truthful, it is not a metal at all, but a semiconductor, whose electrical resistance (when pure) is high and decreases with temperature. We will join the metallurgists, at least for this paper, and refer to it as a metal. In its commercially available form, silicon is metallic in appearance, brittle, with a density of 2.33, less than that of aluminum. Silicon dioxide or quartz has a high heat of formation, which not only makes the metal a useful reductant for other materials, but also makes it difficult to reduce from its ore. The melting point is 1412°C, slightly less than steel, but substantially higher than aluminum or cast iron. The alloys of silicon with iron, usually called ferrosilicons, have some unique advantages. The melting points of most alloys are substantially below those of iron or silicon (Fig. 1). The two major compounds formed (FeSi and FeSi2) help somewhat in the reduction of silicon by their energies of formation, but the influence of these phases on the mechanical properties is more important. Four major groups of alloys are made -- silicon metal (>95% silicon), 75-85% ferrosilicon, 50% ferrosilicon, and silvery pig iron (12-22% silicon). The alloys between 50 and 65% silicon and between 25 and 40% silicon are normally avoided because of structural instabilities, presumably of the two compounds, leading to disintegration of the alloys on cooling.

Jan 1, 1974

By Juan P. Camus

One of the most important decisions in mine development is the selection of the mining method. Open pit or underground methods are selected depending on the shape of the deposit, and its position with respect to the surface. When the decision is not clear or evident, then the common rule is to compare underground and open pit projects to choose the one which yields the maximum return. However, in some circumstances' the best alternative is to start-up the operation with an open pit until a point where mine operating costs make more convenient to employ an underground method. In this case, the final pit limit is not directly related with commodity prices and its position is a funtion of capital and operating costs associated with both methods. The goal of this paper is a mans of establishing the proper ultimate pit considering a potential underground mine. The methodology is quite simple and can be implemented to work with a variety of available routines for pit optimization, such as Lerchs-Grossmann, floating cone, network flow and the Lemieux moving cone optimizing algorithm, which is the tool used by the author.

Jan 1, 1992

By Jeff Salai

The CP-3A contract is the final segment of the MWWST’s 28.3 km (17.6 mile)pressurized water supply tunnel for the metropolitan Boston area. The 1,288 m (4,226 feet) of U-shaped tunnel alignment passed through five rock zones employing four different primary support systems. The short tunnel began in Weston, Massachusetts, at Shaft 5A in soft, completely weathered argillite, passed through a fault zone, and ended in Dedham granite. An 18-foot diameter horseshoe starter tunnel was built to accommodate a 4.94 m (16-foot 2 1 / 2 inch) diameter Robbins TBM. Heavy water inflows were anticipated and subsequently encountered during probe drilling. Pre-excavation grouting was implemented at high pressures to displace high water inflows in the starter tunnel and consolidate the fault zone. This paper will provide an overview of the tunnel construction with an emphasis on ground control, grouting and survey control.

Jan 1, 2001

By Baron Miya, Keith Hanks, William Edgerton, Francis Fong

The City of Los Angeles capital improvement program includes the construction of a new 35-km interceptor sewer. This sewer will be built as a deep tunnel with finished diameters ranging from 2- to- 4 meters. The project will be constructed concurrently in two phases; an 18-km East-West and a 17-km North-South segment. The new sewer provides additional conveyance capacity for an existing deteriorating sewer that is scheduled for rehabilitation. Large sewage spills during the El Niño storms of 1998 resulted in a Cease and Desist Order that established an aggressive schedule for the completion of the project.

Jan 1, 1999

By Michael Fellows

Epidote is a common hydrothermal alteration product in many copper deposits of the southwestern United States. In many of these deposits epidote, along with calcite and chlorite, generally characterize a distal or halo propylitic alteration assemblage, but the mineral can occur within the central potassic alteration zone as well. Epidote is also a common alteration mineral in deposits formed in calcareous host rocks -- the skarn or pyrometasomatic ore bodies. Within the past 15 years, studies of the major and trace element composition of other alteration phases, principally biotite, associated with base metal ore deposits have demonstrated that some hydrothermal alteration minerals are compositional distinct from their igneous or metamorphic counterparts: However, the use of major and minor element content to identify and zero in on mineral¬ized areas does not appear to be very promising. Little work has been published upon the geochemistry of epidote from this standpoint and the results of my work suggest that a similar conclusion can be applied to epidote. My work (Fellows, 1976) suggests that epidote minerals in hydrothermal alteration suites from porphyry copper deposits in the southwestern United States are generally iron-rich rather than aluminum-rich. As a group, these alteration minerals differ compositionally from epidotes of regional metamorphic terrains. I ascribe these differences to the variations in the oxidation character of the respective environments. However, it appears as though the use of major element compositional variations of epidotes as an exploration tool is severely limited. Epidote is a complex calcium-aluminum silicate. Replacement of aluminum by ferric iron establishes a solid solution series between

Jan 1, 1977

By Indranil Roy

Gua supergene enriched iron ore deposit from Jharkhand, India has been geostatistically modeled. Population modeling shows a negatively skewed 3-parameter log-normal fit for Fe and positively skewed 3-parameter log-normal fit for Al2O3 and SO2. Semi-variographic studies for Fe indicate spherical function fit using point kriging cross-validation technique with Co=4.06(%)2, C5.11 (%)2, Co+C=9.1 7(%)2 and 'a'=348m. Kriging with 50mx50mx 10m block size at 740mRL led to a global mean kriged estimate of 61.98% and kriging variance of 4.04(%)2 for Fe with central 90% geostatistical confidence limits at 61.39% and 62.24% for that level. This led to an ore inventory at 740mRL as 7.29 million tonnes of ore.

Jan 1, 2002

By Pedone Ezio Michele, Mohamed Dahir Holad

"The 4c segment is a part of the ""Oman National Railway Project” linking the mining area in the surroundings of Thumrait and the port of Salalah. It is 90 km long and the last 40 km stretch crosses a mountainous area near the city of Salalah. The project includes the excavation of a 33 km double and single bore tunnel and 10 km of safety tunnels. This mountainous area is a holiday destination for Omanis, thanks to its beautiful landscapes, especially in summer time due to the monsoon rains. The tunnelling design had to take into account both these environmental constraints and the limestone rock formations crossed, which are affected by significant karst features. Given the context, the conventional tunnelling method has been preferred. INTRODUCTION The Oman Railway Project (Fig. 1) covers the construction of approximately 2,150 km of railway line for freight and passenger transport which will connect together Oman’s main towns and industrial sites and it will form part of the Arabian Peninsula railway system “GCC Project”. The non-electrified double-track railway line must guarantee a speed of 220 km/h for passenger trains and 120 km/h for freight trains and must guarantee the transit of AAR (Association of American Railroad) H and D plates using clearance envelope according to AREMA (American Railway Engineering and Maintenance-of-Way Association) requirements. The design alignment must have maximum radiuses of curvature of 3,250m and a maximum gradient of 1.0%. The project is divided into 9 constructional and functional segments. •,Segment 4c will be constructed in the southern region of Oman, close to the border with Yemen, to connect the town of Thumrait with the Port of Salalah. •,Segment 4c will run through the Dhofar region and will be mainly used by the freight traffic which currently travels by road."

Jan 1, 2016

By Robert O. Vernon

The discussion of water and pit mining together is most appropriate. In fact, water can be considered a mineral and a well a narrow pit. Thus, of all the mineral resources mined, water is probably the cheapest, most valuable and least valued. The delivered price, including mining, transportation, storage and marketing rarely exceeds ten cents per ton, and our economy would cease without it. The time has come when the public must recognize that the extraction of a mineral resource from the land is a necessary and inevitable result of the industries? attempt to meet the demands of a growing economy. In so much of Florida, the lands mined can, with forethought and planning, be left as improved real estate, water conservation and management lands. On the other hand, the mining industries must face up to the need for the reclamation of land and compact with themselves, appropriate governmental agencies and with the mining states to restore mined lands to usefulness. Of limestone, sand, and clay 90 to 100 percent of the mined material is used, but with planning and specing, these pits, if they penetrate the water table, become valuable as real property. Phosphate, which returns about 70 percent of the mined materials to the pit, can reclaim the land for many purposes.

Jan 1, 1966

By T. D. Oulton

The only known attapulgite clay deposits of any considerable extent and purity in the United States are roughly bisected by the Georgia. Florida state line between Decatur County, southwest Georgia, and Gadsden County, northwest Florida. Although attapulgite clay occurrences both farther East and South are known and have been mined to some extent in the past, at the present time it can be said that substantially: all of the commercial attapulgite clay mining and pro¬cessing is concentrated in a roughly rectangular area some 25 miles long by 15 miles wide,, in the general region of Attapulgus, Georgia, and of Quincy and Havana, Florida. Within this area are located the clay processing plants of the four major producers as well as most, if not all, of the currently active mining operations. The approximate location of the plants and of some of the open mines are shown in the local area map, Figure No. 1, for the purpose of orientation only.

Jan 1, 1965

By W. Morgan, D. Gove

In truck and shovel operations, productivity and cost per ton are influenced by the system matching choice, Optimization involves a balance of the size and number of trucks, the size and type of loading tool and the projected material conditions and haul roads. Caterpillar has updated its Fleet Production and Cost program so miners can more easily look at matching choices and optimize on the variable they choose. This paper introduces the Fleet Production and Cost program. It then demonstrates its capabilities with examples of optimization. Mining operations that use trucks need to properly match the number and size of hauling units (trucks, wagons, scrapers, etc.) to a loading unit (wheel-loader, hydraulic shovel-excavator, cable shovel, push tractor, etc.) to provide the best possible fleet match. Optimizing fleet match minimizes the cost per unit of material moved by that fleet. As haul conditions change (haul length, grade or rolling resistance), there may be need to adjust the number of trucks to maintain the optimum fleet match. Fleet Production and Cost is a tool that can be used to optimize the truck-loader match.

Jan 1, 1995

By A. M. Gaudin

In the first place, let me thank you for inviting me to appear before you today to speak to you on "Mineral Industry Problems - Present and Future". It is a distinguished honor for me to have this opportunity, and I am highly appreciative of this distinction. The beautiful surroundings of Gatlinburg and the pleasantness of a summer occasion are a wonderful tonic for all of us, yet they should not blind us to the seriousness of our Industry's problems No doubt, because of my past appearances before members of the Society of Mining Engineers, at which I discussed wholly scientific topics, or research in the Applied Sciences, you may be expecting me to revert to these subjects. But I intend to venture in a field that is new to me, yet old to all of us, the field of Economics.

Jan 1, 1962

By M. Rodgers

Dow Water & Process Solutions (DW&PS) was approached by ASARCO Inc. to attempt to recover cobalt and copper from their copper solvent extraction (SX) raffinate. Cobalt is added to many copper electrowinning tankhouses to help to prevent lead electrode corrosion. With cobalt?s high price this can be a large expense. ASARCO has ore that contains a small amount of naturally occurring cobalt. Currently they have no way of capturing this high value metal from their leach or raffinate streams. DW&PS has some chelating resin technologies that should be able to help solve this problem.

Jan 1, 2010

The need for an integrated approach to optimization of unit operations in both the pit and the mill has long been recognized, but the complexity and nature of the overall problem has up to now resisted solution. This paper reports on a modeling methodology which couples symbolic and numeric computing to unify operations in both the pit and mill. The ultimate goal of this work is to optimize all operations that are influenced by blasting. Blasting plays a key role in all facets of operations. Obviously, drilling and blasting costs are determined by blast design, but the down-stream costs that are closely related to blasting results are often treated as separate functions: loading, hauling, cleanup, and crushing and grinding are all heavily influenced. Diggablilty and bucket fill factor are a function of fragmentation, the condition of the floor and uniformity in the shape of the muck pile. Likewise, cycle times and loading delays partially determine haul cycles, while fragmentation distribution and size determines the efficiency of truck loading. Removal and breakage of oversize causes loading delays and increases cleanup costs. The influence of blasting doesn't stop at the crusher. Mill productivity, power consumption, and maintenance are a function of the feed. Even at the SAG mill a reduction of a critical particle size during blasting can increase throughput. Thus, a bottle-neck for production far removed from unit operations in the pit can be alleviated by a modification in blast design. The question is: how do we optimize blasting with respect not only to itself but to al\ related mining and milling operations? For that matter, how do we even model blasting so that we can control the results of a blast?

Jan 1, 1991

By Lynn B. Hales

Everywhere you turn today there are articles on artificial intelligence and the rapid emergence of expert systems. Expert systems form a class of software that has developed as a result of the large research effort to develop computers and software that think intelligently. By definition, an expert system is a computer program that contains the knowledge component of an expert skill, can offer intelligent advice and justify its line of reasoning. Expert systems can advise people on what actions to take and when, assist in the diagnosis of the physical condition of a human patient or piece of equipment, or even take actions without human guidance, as in process control applications. Expert systems can also explain the line of reasoning behind a particular piece of advice or query for information from the user. Expert systems can be used as advisors to newcomers in any field in which mastery is attained by many years of experience. They often can provide expertise more uniformly and rapidly than human experts. Expert systems can also provide a means of documenting expert knowledge and procedures and provide a common repository for a changing knowledge base. The expert system can represent the best expertise available, thought out in the absence of pressure situations. Each of these attributes or characteristics should be helpful in improving typical concentrator control systems.

Jan 1, 1987