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By Luis Pommier

In the United States, about one-quarter of the fuel oil and natural gas consumption is associated with power production in utility and industrial boilers and process heat needs in industrial furnaces. Coal has been an attractive candidate for replacement of these premium fuels because of its low cost, but there are penalties associated with the solid fuel form. In many cases pulverized coal is unacceptable as a premium fuel replacement because of the extensive cost of retrofitting an existing boiler designed to burn oil or gas. In the cases of synthetic fuels from coal, research and development still has a long way to go and the costs of research and development are very high. Another option which appears very attractive is the use of solid coal in a liquid fuel form, coal slurry fuels. Occidental Research Corporation (ORC) has been developing coal slurry fuels in conjunction with Island Creek Coal (ICC,) Occidental Petroleum's wholly-owned subsidiary. Both Coal-Oil Mixtures and Coal -Water Mixtures are under development. ICC is a large eastern coal producer, engaged in the production and marketing of bituminous coal, both utility steam and high quality/low volatile metallurgical coals. A sister division, Sheridan Enterprises is engaged in the development of western coals.

Jan 1, 1983

By Dru Brown

More than 150 Mt (165 million st) of material crashed down at the Bingham Canyon Mine (Rio Tinto/Kennecott Utah Copper) near Salt Lake City, UT on April 10, 2013. The mine, one of the largest openpit mines in the world, ceased operations and evacuated personnel prior to the slide when it was discovered that material was moving at a rate of 5 cm/d (2 in./day). The slide destroyed the mine?s visitor?s center, buried several pieces of large mining equipment and severely hampered production. The Kennecott Utah Copper Corp. immediately began to assess the damage and look for options to reestablish operations. The highly unstable ground ? emphasized by another minor slide in September 2013 ? makes any cleanup efforts extremely dangerous. With terrain too dangerous for human operators, Kennecott was forced to look for alternatives that would help the company work on the treacherous slopes of the landslide while also keeping personnel safe.

Jan 1, 2014

By Clyde N. Garman

The Homestake-New Mexico Partners consist of Homestake Mining Company of Lead, South Dakota; Rio de Ore Uranium Mines, Inc; United Western Minerals Company; White, Weld and Company; J.H. Whitney; San Jacinto Petroleum Corporation; and Clyde Osborn, Homestake Mining Company is the general partner, the others are limited partners. The Rio de Ore Uranium Mines, Inc. has. a mine in the Ambrosia Lake area; this was the first mine to go into production in this area. The United Western Minerals Company also has a mine in the Ambrosia Lake which is operated as a "farm out" from the San Jacinto Petroleum Corporation. These mines are the principal sources of ore for the mill. This group was the first to obtain a contract with AEC to make uranium concentrate from Ambrosia Lake ores and the first to have a mill in operation specifically for these ores. With Clyde Osborn as the sparkplug and co-ordinator holding the ore suppliers of, this group together, a contract with AEC was agreed on as to its essential points by mid-summer, 1956, At that time, there was no general partner and no financing, so me formal contract could be signed. By December, 1956 when the contract was signed and the present partnership officially formed, much of the basic engineering was done and purchasing of main elements of the mill waited on the formalizing of agreements, at the specifications and sizes agreed on previously. Ground for the mill was broken in April, 1957. The sampling plant went into operation in October and ore was first fed to the ball mills on February 5, 1958, ten months after construction actually started. Filling of the circuit with sodium carbonate bicarbonate solution had begun a week before that.

Jan 1, 1959

By P. L. Sibrell

Three different refractory carbonaceous gold ores from the Carlin operation in northeastern Nevada were investigated to characterize the effect of passivation treatments on the nature of the carbonaceous material. The carbonaceous material was chemically isolated from the ores and passivated residues, and examined by FTIR spectroscopy, elemental analysis, and gold adsorption capacity. The main component of the carbonaceous material in these ores was found to be a naturally occurring activated carbon-type compound. Hydro-carbons were detected on rare occasions, but no evidence was seen for humic acids. Ore samples were passivated by autoclaving, or by treatment with sodium hypochlorite or gaseous Chlorine. In some of the passivation tests, a new peak was observed in the IR spectra of the isolated carbonaceous material, that was due to carbonyl functionalities. However, all of the passivation treatments tested decreased preg robbing significantly. This suggested that the appearance of the carbonyl peak was due to the severity of the conditions during passivation, rather than the method used.

Jan 1, 1990

By DING TANG, JINGHE CHEN, Shuiping Zhong, CHEN KUANG

The Zijinshan gold-copper mine, located in Shanghang County, China, is a porphyry-type, low-grade ore deposit with a geological profile of upper gold and lower copper. Despite its low-grade nature, it has become one of the largest in production scale and most profitable nonferrous metal mines in China, which can be attributed to the successful application of hydrometallurgy as well as proper engineering design. A large-scale, open-air cyanide heap leach has been successfully implemented to recover gold under the humid and rainy weather conditions of southern China. Furthermore, according to the gold ore characteristics, a combination of gravity separation, carbon-in-leach and heap leaching processes was developed to improve gold recovery. In terms of copper extraction, copper ore of a grade higher than 0.25 percent is fed to the flotation plants to produce copper concentrate (gold is also enriched here), while copper ore of a grade lower than 0.25 percent undergoes heap bioleaching followed by solvent extraction and electrowinning to produce cathode copper. Additionally, a unique bioleaching system has been established at the Zijinshan Mine: low operating pH (0.8~1.0), high concentration of total soluble iron (~50 g/L), high temperatures (45~60 °C) and low activity of microorganism (~104/mL) in the pregnant leach solution (PLS). This review paper summarizes the practical experience acquired in developing the Zijinshan gold-copper mine and could be of use in other gold and/or copper plants.

By RALPH BALTES, AMIR EHSAN KIANFAR, FABIAN UTH, ELISABETH CLAUSEN

  Underground positioning and communication are essential technologies for the future of underground mining operations. In contrast to other positioning and communication technologies such as wireless local area network (WLAN) or radio frequency identification (RFID), ultra-wideband (UWB) radio technology provides significant benefits like accurate and robust positioning of mobile machine equipment, which is indispensable for future autonomous systems in underground mining processes, such as production, transportation and auxiliary operations. Among these technologies, UWB offers many advantages, including higher accuracy, robustness, resistance against noise and multipath effects, and low power consumption [1,2]. Underground automation and localization systems benefit from these advantages and use the technology to improve efficiency and safety. There are many studies being carried out on this technology to increase the results’ accuracy, energy sufficiency and more. Two robust UWB modules that were developed for underground positioning and collision avoidance with regard to human safety in underground mining operations are introduced. The measurement results of tests carried out in an underground mine are discussed as well to confirm the functionality of the system.

By S. R. Dindarloo

"Truck-shovel systems are the dominant material loading and haulage machinery in open pit mining operations. Optimal selection, sizing, and allocation of this capital intensive equipment is highly desirable for both achieving production targets and improving the mine’s economics. In this study, discrete event simulation technique was applied for modeling material transportation in Golegohar open pit iron ore mine in Iran. Direct observation of the material loading and haulage for duration of three months resulted in statistical modeling of the operation in the form of probability distribution functions. These probability models were used as the inputs of a stochastic simulation model constructed in GPSS/H simulation language. The model was validated through comparison with the actual operation and was used to test different what-if scenarios and sensitivity analysis of the current system. Some modifications in the number of trucks, shovels, and dispatching strategies were proposed. Simulation resulted in considerable improvements in the mine’s production and economics.INTRODUCTION There are three different mechanisms of discrete, continues, and hybrid material transportation in open mines, including but not limited to: i) in-pit crusher and conveyor belts (hybrid), ii) slurry piping (continues) and iii) truck-shovel system (discrete). Although, each mechanism has its advantages, the truck-shovel system is the dominant method of material loading and handling in open pit mines owing to its high production rate, excellent flexibility, relatively low operating and capital costs, and good maintainability. General objectives of optimal equipment selection include: i) meeting the long and short term requirements of production rates, ii) human & equipment safety, iii) environmental protection, and iv) economic operations (Figure 1).The two most important decision factors on a truck-shovel system selection and sizing are the equipment geometry and size. Geometry (equipment width, weight, turning radius, swing angle, etc.) is mostly controlled by mine’s designs and layouts, as well, as operational constraints. After selection of a favorable geometry based on the constraints; the next step is to select the equipment manufacturer. Once the geometry and manufacturers are selected; the next step is to decide on models (e.g. Bucket size) and required number of each unit"

Jan 1, 2015

By E. McCarthy

"INTRODUCTION Talc is a hydrous magnesium silicate with the approximate elemental composition 4MgO.3SiO2.H2O. It is one of the layered phyllosilicates (like kaolin and mica) but it differs from these in that it is relatively hydrophobic. This is due to its unique crystalline structure whereby a brucite inner layer is sandwiched between silica layers and the adjacent silica layers have no interlayer bonding other than van der Waals forces. This allows talc to be sheared easily along this basal plane, and the surface is covalent not ionic. Talc occurs both as a relatively pure material (>90% talc content) and in conjunction with many other minerals in proportions all the way from 1% to 90%. At lower concentrations, it is often considered a nuisance mineral when it occurs with base metals like copper, molybdenum or nickel or with precious metals like platinum or palladium. It floats readily with these materials and often is suppressed using guar gum or carboxy methyl cellulose which will absorb along the basal surface and make it hydrophilic. Alternately if the reduced ore is hydrophobic, like MoS2, then a partial oxidation of the sulfide will convert the surface to a hydrophilic oxide and the talc can be floated away in a separate step. Talc in grades from 20 to 90% has been commercially exploited in a wide range of pigment (paint and paper), material (ceramic, construction and cosmetic), reinforcing (polymers and composites) and functional (pitch adsorbent, lubricating agent) applications. Initially these tended to be local or regional markets, but eventually with certain higher purity grades, cosmetic, polymer and ceramic applications became valuable enough to be national and trans ocean markets. TALC FLOATATION PLANTS This drove the need for higher purity grades of talc and initially this need was met primarily by ore sorting. This works well for certain deposits with well crystallized talc lenses, but for ores, such as those from widely available ultramafic deposits, where the liberation size is closer to 100 microns, sorting is not effective. That drove the need for floatation and the first investigations were published by Clemmer and Cooke of the US Bureau of Mines in 19362. The first commercial floatation plant was installed in Johnson, VT by the Eastern Magnesia Talc Co in 1937. The circuit is shown in the schematic (Figure 1). The ore was an ultramafic, serpentine derived talc; mineralogy was about 55% talc, 40% ferroan magnesite and 5% oxides, sulfides and other silicates. The oxides include hematite and chromite, sulfides pyrite and gerstorffite and silicates chlorite, serpentine and mica. After crushing, the ore was dry ball milled and then air classified to remove minus 325 mesh fines. The coarse fraction was further classified to cut at about 100 mesh and the fines from this were the feed to floatation. The -325 mesh (about 15% of the ore) was sold as a paint grade and the plus 100 mesh (about 25% of the ore) was screened to make an asphalt backsurfacing grade."

Jan 1, 2018

By W. G. Pariseau

This paper is concerned with the problem of calculating ground movement that occurs as a consequence of mining. Solution to this problem is straight forward in principle but rather complex in practice. The complexities of the problem arise from the ever present constraints of technology and economics. However, the identity of these constraints is often obscured by a faulty understanding of the fundamentals of the problem and a lack of appreciation of current computational capabilities and costs. As a consequence much time and effort are sometimes wasted on gathering information that is of little direct value to ground control programs while important input data are neglected. This paper therefore reviews the essentials of the process of formulating the ground movement problem. Emphasis is upon application to longwall mining, although much of the discussion applies to other mining methods as well. In many instances, the hardrock term stope could be substituted for longwall panel because the fundamentals of the problem are independent of the excavation dimensions and numerical values of rock properties. The latter affect the outcome of a calculation, of course, but not the underlying formulation. Only the major features of the problem are discussed in this brief review. The objective of the discussion is the generation of a reliable basis for developing a technically sound ground control strategy. Any rational ground control strategy must be consistent with basic physical laws. For example, under static conditions, equations of equilibrium must be satisfied. Operational, that is, tactical, details may vary widely with local conditions, but the basic approach must be based on physical laws. The alternative empirical route is intrinsically unreliable and unnecessary as well. Empirical descriptions of ground motion caused by mining including recent statistical curve fits to specialized data sets (for example, surface subsidence data) as well as antiquated "theories" of ground pressure and so forth, however dignified with mathematical formulas, are hardly worthy of the label "theory". Extrapolation of statistical data is always accompanied by rapidly diverging confidence limits, while empirical equations simply lack predictive capability under circumstances even slightly different from those of the original development. For example, applications of surface subsidence curves generated empirically in the United Kingdom to coal mines in the United States generally result in considerably greater subsidence and wider subsidence troughs than actually observed. Locally, empirical criteria for specific ground control actions may be made practical through trial and error, but such tactics are no basis for the development of a general ground control strategy. In this regard, it is worthwhile to recall the traditional scientific distinctions between speculation, hypothesis and law, between the empirical and the proven.

Jan 1, 1982

By Chaoxun Zhao, TAIYOU LI, JIAQI JIN, Chen-Luh Lin, Jan D. Miller

A large portion of the energy consumed in copper concentrators is used to reduce the particle size of the feed by crushing and grinding. The cost of metal production could be reduced if low-grade particles of centimeter size were removed prior to further processing. Two copper sulfide ore samples (3 × 1 cm) from Arizona were analyzed by micro X-ray computed tomography (Micro-XCT) to determine the grade of copper sulfide in each particle. For copper ore sample A, a significant number of particles contained very low amounts of copper, while some particles had copper sulfide grains of millimeter size. Based on Micro-XCT, it was expected that 85 percent of copper for sample A could be recovered at 65 percent of mass rejection during preconcentration by sorting. However, in sample B (a different copper ore), distribution of copper sulfide was dispersed primarily in each ore particle, so for the particle size class of 3 × 1 cm, liberation of copper sulfide and gangue minerals was not significant. In view of the XCT results, dual-energy X-ray radiography was used as a basis for sorting. Pilot-scale X-ray sorting of sample A (10 × 1 cm) showed 31 percent rejection of a 0.08 percent Cu gangue product with a corresponding recovery of 90 percent copper.

By James A. Berberick

Research methods to develop an economic model for the determination of regional mineral advantage are discussed. An industrial complex conceptual framework is used to study potential mineral resource outputs of Kansas. A procedure for making a comparative cost analysis of potential outputs for a Kansas-based industrial complex is outlined and illustrated. Methods for estimating aggregate demand and for developing an input-output matrix for a hypothetical limestone complex are explained. The input-output matrix is expressed in physical units. A computer algorithm for converting physical production data and input cost data into total cost per unit of output information is briefly explained and flowcharted. Limitations and usefulness of this procedure in determining regional advantages are surveyed.

Jan 1, 1969

By MOHAMMED AMINE BELMI, ANAS DRIOUCH, ABDELAZIZ LAHMILI, LATIFA OUADIF

The mineral industry uses significant amounts of water in processing. Thus, sustainable practices with the processing of ores are of critical importance. An impact tester was used to measure the adhesion force between particles and a glass disk [1,2]. A removal force was caused by the impact of the disk/particle containing a puck with a stopper. Johnson-Kendall-Roberts (JKR) theory [3] was used to determine the interfacial energy between the particles and the substrate. Capillary condensation of water can occur between the particle and surfaces in humid environments. The adhesion of particles on rough surfaces has been studied previously [4-10]. The research presented herein combines both variables to separate particle types with minimal water usage.

By Jamal Rostami, Tom Iseley, Saleh Behbahani

Tunnels and underground infrastructures assets, like all assets, deteriorate with time. At some point, they reach the end of their useful life. Therefore, frequent inspections, higher levels of maintenance, and rehabilitation are needed to address loss of life and safety concerns. The repair cost of tunnels will increase if maintenance of tunnels is not satisfactory and timely. Historically, tunnel inspections have primarily relied on visual and manual procedures. Due to their time-consuming nature and susceptibility to human error, there is a demand for alternative automated techniques that can enhance efficiency and reliability in tunnel inspection. By utilizing a tunnel scanning system, such as laser scanner and thermography, or photogrammetry system, tunnel inspection cost, time, and personnel can be reduced. The goal of this study is to utilize deep convolutional neural networks (CNNs) for automated identification of defects in tunnel lining inspection. This paper presents a framework to classify two types of defects in tunnel lining (water leakages and cracks) using CNNs. The CNNs were trained and tested using 4,608 images. The Precision, Recall, and F1 Score were each 99.6%, confirming the viability of this approach in the automated defect identification in tunnel lining.

Jun 23, 2024

When most people think of coal mining, they envision men in soot-covered clothes and hard hats digging at deposits in deep underground caverns. These mental images commonly include coal cars rumbling on rails as they emerge from the earth, filled to the brim with rocky ore. The world of modern, longwall coal mining is a far different place. Yes, it?s underground, the miners still wear hard hats and the environment is filled with soot. However, today?s mining operations are carefully monitored and the entire process is highly automated. Five kilometers (3 miles) underground, a sophisticated, high-powered mining machine moves steadily through a 2-m (6-ft) high tunnel at an average speed of 3.2 km/h (2 mph), carving out coal, then conveying it to a crusher and carrying it to the surface. Instead of digging out the ore, a longwall mining system slices it from the exposed tunnel face, using giant rotating shears. The shorn coal tumbles onto a conveyer below the shears and is conveyed to the stageloader, where it is crushed and dumped onto the main conveyer belt that eventually hauls it out of the mine. Integral to the longwall shear and conveyor is a moving metal roof that protects it from the thousand plus feet of ground above. The ceiling panels automatically advance above the shears, powered by hydraulic roof supports that stand on the other side of the tunnel, moving in a slow, sideways lock-step with the shears. This complex and massive machine makes longwall mining the most ef?cient and productive method for excavating coal. In fact, it produces 2.7 kt to 22.6 kt (3,000 to 25,000 st) of ore per shift, versus 544 to 907 st (600 to 1,000 st) for the conventional room-and-pillar mining. Using that method, miners develop one section of a mine at a time after carving out load-bearing columns of coal to support the roof above their heads. Longwall mining also is considered safer than the room-and-pillar method, largely because the process is mostly automated, requiring fewer workers. Still, longwall mining has its drawbacks: The equipment is expensive and the mining conditions are harsh. An entire longwall system can cost between $50 million and $100 million, while the electrical controls used to operate it can cost an additional $1 million to $2 million. These investments grind away all day, every day, in hot tunnels filled with coal dust.

By J. M. Beck

Mineral property appraisers engaged in eminent domain actions on properties for which mining is the highest and best use must be fully competent in all phases of mineral resource estimation, mine project development, and mine operations (or retain the requisite competent assistance), as well as educated in eminent domain appraisal (USPAP Competency Rule). Failure to ensure such triggers the issue of appraisal competence and demonstrates a flagrant disregard of the myriad code(s) and guidelines to which the appraiser is subject. The cavalier assertion of some vague, undefined “latitude” in the valuation process does not exonerate the appraiser from a disregard of the USPAP Competency Rule. Lack of independence (i.e., “advocacy”) in mineral property appraisal is the usual result of a weak background in mining and/or appraisal theory. While it is readily apparent to those able to recognize it in reports and testimony, judges and juries cannot be expected to detect or recognize purposefully misleading (or even fraudulent) valuation concepts or testimony. Purposeful deception by the appraiser can lead to specious over-compensation of the property owner (thus victimizing the taxpayer); or, a failure to provide appropriate and just compensation to the property owner – yet, the purpose of an eminent domain proceeding is to leave the property owner no richer or poorer as a result of the taking. This paper highlights some of the deceptive practices encountered in litigation settings and raises issues of competency, professional ethics, and the effectiveness of the inherent enforcement capabilities within those institutions awarding professional certifications. INTRODUCTION The practice of eminent domain mineral property appraisal requires (particularly with respect to undeveloped mineral properties) that the appraiser possess the requisite level of competence in all phases of mineral resource estimation, mine project evaluation, mine development, and mine operation (through closure). To the extent the appraiser lacks such competence, it is incumbent on the appraiser not only to divulge this lack of expertise but also to seek competent assistance in the performance of the appraisal. This competence or expertise can only be obtained through a combination of appropriate and relevant technical education and direct mining industry experience. There exist a number of professional certification and/or credentialing authorities that speak to such competency. In a similar manner, eminent domain mineral property appraisal (as the term implies) also requires that the appraiser possess the requisite level of competence in the practice of eminent domain appraisal. This competence or expertise can only be obtained through appropriate and relevant education, direct knowledge of appraisal theory, particularly as it relates to the concept of eminent domain, and licensure.

Jan 1, 2019

By L. Alan Weakly

The purpose of this paper is to present a viable method of reinforcing rock pillars by utilizing fully grouted reinforcing steel and a cement - fly ash mortar. Although the fully bonded bolt concept is not new as exemplified .by the present widespread use of resin bolts within United States mines and by the use of cement grouted reinforcing used as back pins in the Kiruna Iron Ore Mine in northern Sweden, (1)(2) the method of stabilizing mine pillars with fully bonded reinforcing is new. This method, called the "grout-rebar system", was first incorporated at St. Joe Minerals Corporation's Fletcher Mine in December of 1972. The system was used on an emergency basis before extensive research on the mechanics of the system could be completed. Since December of 1972, however, approximately 206 pillars have been reinforced at Fletcher and the system is currently being used on a regular basis at two other St. Joe mines and at two competitor mines in the area. Basically, this paper is a case study of the efforts, research and results of utilizing the grout-rebar system, on a selective basis, at the Fletcher Mine. In addition to information about the system, this paper will explain in detail the three rock mechanics instruments developed by St. Joe and used to measure and monitor rock movement to validate the grout-rebar system.

Jan 1, 1976

By M. B. Daza, B. Lattimer

"Even with modern detection and firefighting techniques, mine fires continue to be a safety concern. However, some underground mine fires can be addressed with the remote application of high expansion foam, reducing firefighter exposure to hazards. The flow of this foam can be numerically or computationally simulated in order to gain a better understanding of its behavior, but rheology parameters are needed as inputs to produce accurate simulations. For this reason, this work studies the rheology of firefighting high expansion foam using a foam generator and Poiseuille –Flow Rheometer. Rheological parameters for foams with expansion ratios between 250-1280 are represented by the consistency index (k) and the power law index (n) due to the results show a strong agreement with the Power Law model for non-Newtonian fluid viscosity. Furthermore, experimental results show that high expansion foam behaves as a shear thinning fluid with a power law index around 0.4 and viscosities in the range of s 0.1 Pa-s and 0.042 Pa-s under shear rates between 44 ??-1 and 187.3 ??-1. INTRODUCTION High expansion foams are called to foams with expansion ratio greater than 200. Expansion ratio (??) is defined as the ratio between the volume of foam produced (i.e. volume of foam solution and volume of gas) and the volume of foam solution used (NFPA 2014). Because of its high expansion ratio, one of the most important application of high expansion foams is to fill or flood large spaces such as hangars, storage facilities and underground mines for fire suppression. The foam can fill large structures using small quantities of foam solution within a short time (Sthamer 2012) (Martin 2012). Although the specific high expansion fire suppression mechanism has not been understood on a quantitative basis, a possible mechanism is fuel isolation when the foam act as a physical barrier between oxygen and the flame. Furthermore, as a consequence of this contact water is evaporated, causing cooling of fuel and surrounding air. Besides, water vapor as product of water evaporation causes a dilution of oxygen concentration available to the fire (Fleming and Sheinson 2012). High expansion foam can be applied remotely by means of conduit pipes or in situ close to the fire. In most of the underground mines scenarios, fires have to be addressed remotely to reduce miner and firefighter exposure to the hazards (Smith et al. 2005). Although high expansion foams should not be blasted and must be deposited directly on the area of application because of their low density (Harding et al. 2016) sometimes it is complicated to apply it directly to the fire due to complex access areas at underground mines. In these cases, foam has to be applied far away from the fire. Despite of this fact there is a lack of knowledge in terms of rheological behavior of high expansion foam under high shear rates (Gardiner, Dlugogorski, and Jameson 1998). Furthermore, there are a few attempts to simulate numerically the high expansion foam flow due to the ignorance of its rheological parameters and its complex behavior. (Weaire 2008)."

Jan 1, 2018

By Dennis W. Leonard

Let us begin our discussion by looking at historical and current levels of sales of both natural and synthetic zeolites on a world-wide basis. Due to the understandable reluctance of some companies to disclose sales data, some estimation has been necessary regarding the tonnages and values shown in Table 1. We are confident, however, that they are within acceptable limits, especially the numbers referring to natural zeolite.

Jan 1, 1979

By REHMAN ATTA UR, Kwame Awuah-Offei

This work evaluated the effects of bucket orientation and operating parameters on resistive forces and penetration for rubber-tire loaders (RTLs), such as load-haul-dumps (LHDs) and front-end loaders (FELs). The work used a 1:16 scale LHD model to test an RTL bucket operating at different levels of traction (tractive effort), speed, digging height and rake angles in a full factorial design experiment. The test was repeated on two muck piles with different particle sizes, and generalized regression modeling was applied to test the association of rake angle, tractive effort, speed and digging height on penetration and resistive forces for RTL buckets. The results show that speed and tractive effort are more important in explaining RTL penetration and resistive forces than height above the floor and rake angle. Speed, tractive effort and height above the floor are positively correlated to bucket penetration, whereas the rake angle is negatively correlated to penetration. Similarly, speed, tractive effort, rake angle and height above the floor are all positively correlated to resistive forces incurred during initial penetration. The results show that the combined effect of speed and tractive effort is negatively correlated to penetration and resistive forces — a novel finding that enhances our understanding of RTL loading. The results also show that the effects of speed, tractive effort and height above the floor all change with changes in particle sizes. This work provides insights into the effects of rake angle, height above the floor, tractive effort and speed on penetration and resistive forces for RTLs to facilitate better design and efficient use of these loaders.

What is your personal view and assessment of the overall health of the industry in the current global economy? The economic outlook remains soft for the near future and, although the global economy is showing signs of recovery, uncertainty has tempered the pace of recovery. In addition to uncertainty, we are still facing significant economic challenges in many parts of the world, including Europe and the United States. The rapid expansion of China?s economy has recently slowed, further contributing to the sense of uncertainty in the overall health of the global economy. This situation is both a blessing and a curse, depending on which sector of the mining industry we are considering. For example, coal, industrial minerals, aggregates, base metal and precious metals markets are impacted by different forces and drivers and will experience different outcomes within the same economic environment. Let me give a few concrete examples to illustrate this concept. The prevailing economic uncertainty that I have just described tends to drive investors toward safe havens. Gold has historically been viewed as a safe haven and as long as investors shy away from traditional investments, gold prices will remain high and gold mining companies will continue to expand and invest capital in their operations. The same sluggish economy that drives gold prices higher has the opposite effect on other segments of the minerals industry. A great example of this is industrial minerals and aggregates used in construction. The markets that consume these minerals have contracted significantly over the past five years. The outlook for this segment is poor, as the glut of available housing continues to inhibit demand for new construction and, thus, many industrial minerals. In addition to this, the federal government?s lack of political will to enact long-term legislation funding transportation and infrastructure projects continues to be a drag on the U.S. aggregates industry.

Jan 1, 2013