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By J. C. Stankus

In this paper, an innovative concept in longwall tailgate support is discussed. This new concept utilizes a new high capacity roof truss system in lieu of conventional wooden crib block. The first field test was conducted at Bailey Mine and was very successful. Similar tests have been installed in other mines and seams. An extensive instrumentation plan was designed and implemented in the truss test area. The test data has shown that the dynamic roof truss system effectively controls the various abutment pressures caused by longwall mining thus maintaining a stable tailgate entry.

Jan 1, 1995

By H. Ipek

Industrial grinding machines used in the mineral processing industries are mostly of the tumbling mill type. These mills exist in various types: ball, rod, pebble, autogenous, and semi-autogenous. Balls and rods are traditionally media shapes used in the tumbling mills. In resent years, as an alternative to balls, grinding charges with various shapes are being used. Cylpebs are slightly tapered cylindrical grinding charges with length equaling diameter, and all the edges being radiused. Cylpebs of equal diameter and length have 50% greater surface area and 45% greater weight than balls of the same material. In addition, they have 9% higher bulk density than steel balls, or 12% higher bulk density than cast balls. An important advantage of cylpebs over balls is that cylpebs produce narrower granulometric distribution due to their shapes. However, some discrepancies were found in the literature regarding the milling performance of cylpebs in comparison with balls (Chi, 2004). In recent studies, Chi (2004) has provided detailed information on cylpebs and has compared these to balls in relation to media mass, size distribution, surface area, and input specific energy. Ipek (2006) has investigated the effects of cylpebs and balls with equal mass and surface area on the breakage rate of quartz, using cylpebs and balls separately. Similarly, Lameck and Moys (2006) have investigated the effects of balls and worn balls on breakage rate of material using worn balls as grinding environment. However, no study has attempted to investigate the effects of grinding environment other than balls on the brekage distribution. As indicated by Prasher (1987), the breakage distribution function is independent of the following variables in ball mills: hold-up (Mika et al., 1967; Kelsall et al. 1969), mill speed and ball load (Herbst and Fuerstenau, 1972), media load and ball density (Kelsall et al., 1973), mill diameter (Malghan and Fuerstenau, 1976), and powder charge (Shoji et al. 1980). The aim of the present paper is to compare the effects of cylpebs and balls on the breakage distribution function of quartz with respect to same mass and same surface area. BACKGROUND Comminution as a rate process is called kinetic approach. Studies on the kinetic approach are reviewed by Oner (2001). Oner states that grinding kinetics are based on studies by Kolmogorov in 1941 and that Robert (1950) is the first to suggest this approach. Later, Melzak, Loeveday, and Reid have improved the grinding kinetics equation; and, Austin and Lynch have conducted two basic studies on the analytical solutions of these equations. Considering the results of studies comparing the size reduction mechanisms, it has been accepted that breakage constitutes of two operations. These two basic operations, first defined by Epstein (1948), are those of selection of material for breakage and the distribution of breakage material to particle sizes smaller than the initial size (Lynch, 1977). Epstein defined the two operations as: ? Pn(y), the probability of breakage of a particle size in the nth step of the breakage process. ? F(x,y), the cumulative distributions by weight of particles of size x<y arising from the breakage of a unit mass of a size y. Probability of breakage is called a selection or a breakage-rate function (Si). Characteristics size distribution after breakage is called a breakage distribution or appearance function (Bi,j). Due to the difficulties in representing particle size distributions mathematically and constantly, the batch equation based on particle size fraction is suggested. Thus, as is the case in breakage distribution and specific rate of breakage, the breakage parameters were defined by batch grinding experiments conducted in laboratories (Oner, 2001). When effective breakage occurs in the mill, the breakage of material with single feed size fraction usually fits first order grinding kinetics and the specific rate of breakage values can be calculated through the slope of semi-log plot. The values of the breakage distributions are deduced from the size distributions at short grinding times where there is mainly size 1 material breaking and only small amount of smaller sizes to rebreak (Austin et. al., 1984). B values can be calculated by using BII. [ ] where j is the top size of the charge, Pi(t) is the cumulative percent undersize of i th size interval at the short grinding time which gives no more than about 30% broken out of the top size interval. Cumulative primary breakage distribution, Bi,j, is also defined in an empirical form by [ ] where xi is the top size and Bi,j is the weight fraction of primary breakage products. The parameters F, ? and ß define the size distribution of the material being ground. On plotting size versus Bi,j on log scale, the slope of the lower portion of the curve gives the value of ?, the slope of the upper portion of the curve gives the value of ß, and F is the intercept as in Fig.1. [ ]

Jan 1, 2009

By V. Price

Abstract: Action of certain strains of bacteria has been implicated as a significant factor in the oxidation of ore deposits. Other bacteria are thought to be significant in the formation of syngenetic sedimentary ores and in supergene enrichment processes. A normal soil/ground-water regime provides all of the necessary pH and Eh conditions for several groups of bacteria which influence the sulfur cycle in nature. Limiting concentrations of nutrients such as sulfate ions can determine whether a particular microbial species is active at a given place. In the present study, ground water was analyzed from a mineralized area and from a presumed barren area. Trace metal content of the ground water gave no well defined clue as to the presence of a sulfide ore deposit. Sulfide producing bacteria (presumably sulfate users) were found in water from about 50% of wells sampled in the mineralized area and in about 30% of samples from the barren area. These bacteria are readily detected and may provide a useful tool for regional geochemical recon-naissance. Bacterially produced sulfide ions can remove metals such as copper and zinc from solution thus complicating the interpretation of hydrogeochemical prospecting.

Jan 1, 1972

By James W. Bass

Atmospheric fluidized bed combustion (AFBC) is an improvement in coal-fired boiler design that offers several advantages over conventional boilers. AFC can meet sulfur and nitrogen oxide emission regulations without the need for add-on flue gas treatment equipment. The relatively low combustion temperature inhibits ash melting, thus reducing slagging and fouling which can, in turn, increase a boiler&apos;s fuel flexibility. This report discusses, in general, AFBC technology and, in particular, progress at the 20-MW Pilot Plant built by the Tennessee Valley Authority (TVA) at its Shawnee Power Station near Paducah, Kentucky.

Jan 1, 1985

By Joseph M. Driscoll

After 30 years of successfully mining gold, Newmont Gold has temporarily ceased production from the original Carlin Pit. In late 1993, the Carlin East decline was driven and an extensive underground exploration program was started. Today, Newmont Gold produces refractory ore from the Carlin East Underground at the rate of 864 t/d (950 stpd). Annual production is more than 3.1 t (100,000 02). More than 70 underground miners will be employed during Carlin East&apos;s estimated six-year mine life. About 70% of the ore at Carlin East is mined by mechanized longhole stoping with delayed, cemented backfill. The remaining ore is mined by underhand drift and cemented fill methods.

Jan 1, 1997

By J. S. Martin

The redesign and reinforcement of a highwall located adjacent to a $10,000,000 shopping center, destabilized by active subsidence, was conducted after an extensive geotechnical investigation. The highwall was excavated in a hillside where a coal seam had been retreat mined and augered. Engineering geological mapping, determination of the properties and behavior of the intact rock, fractured rock, and urethane grout material, and soil were required to characterize the highwall and conduct a stability analysis. Remedial measures included re-excavating portions of the highwall to reduce the slope angle, and pressure grouting of the immediate roof.

Jan 1, 1988

By J. Bertisen, G. Davis

Previous analyses of small samples of mining projects have found that feasibility studies tend to well under-estimate the actual capital costs of the project. Our review of 63 mining and smelting projects completed over 4 decades confirms that as-built capital costs are, on average, 25% higher than as estimated at the bankable feasibility study stage. There appears to be little attenuation over time of this bias in capital cost estimation, at first appearing to reflect an absence of learning on the part of the consulting engineer. We instead argue that this persistence of bias is intentional, driven by a scarcity of project financing and the need to inflate the project economics in a bid to secure financing. Around this intentional bias is a considerable amount of scatter. Roughly half of all projects’ as-built capita costs fall outside of the expected ±15% of the feasibility study capital cost estimate, even after allowing for intentional estimation bias. Cost overruns of 100% or more happen in roughly 1 out of 13 projects. The data reveal that a shifted lognormal probability distribution should be used when modeling mining project capital costs in a Monte Carlo analysis.

Jan 1, 2007

By Landy Stinnett

"When performing a valuation of a mineral property, a developing mine or perhaps an ongoing operation, the appraiser is typically provided with a range of information prepared by the property owner. This information can include ownership records, geological interpretation, assay data, an estimate of the reserves or resources believed to be on site (tons and grade), mine plans, production forecasts, capital and operating cost projections, and so forth.The appraiser familiarizes himself with the data, analyzes the various reports and then prepares the appraisal. There is usually a site visit, and there may be some effort at comparison of the particular mineral deposit with others in the region or with those of similar depositional characteristics, but for the most part, the appraiser is relying on the corporate documents, tempered by his/her experience in the field. Time is usually of the essence, the cost for the assignment has been trimmed, and therefore independent verification of the various components comprising the underlying data base (legal review, redrilling portions of the deposit, collection of new samples, re-assaying, etc.) is unlikely in most situations.In the case of high-value commodities — gold, silver, diamonds, perhaps the platinum-group elements — there have been numerous examples of the property owners attempting to increase the value of their holdings by nefarious methods. Most of these involve salting the deposit in some fashion; i.e., introducing small amounts of the commodity into samples being sent to a laboratory for analysis so that the resultant assay shows a higher grade (Donaldson, 2002; Greeley, 2001; Lechler et al., 2008 and Meech, 2001). Other schemes to enhance the apparent worth of a property include the use of nonstandard assay procedures, incorrect handling or withholding of the underlying information, and false reporting."

Sep 1, 2016

Instabilities occurred as a result of climate changes caused to investigate the rock behavior dependency to temperature changes, in this paper. In the natural earth condition, the phase transition of pore water has known to be the most effective factor causing different rocks mechanical properties due to temperature changes. So, the temperature range of [-30, 30]°C is selected in laboratory tests of this study. P-wave velocity, unconfined compressive strength (UCS) and elasticity modulus of rocks at different temperatures are studied by developing a temperature adjusting apparatus. The tests were performed on three rock types. The results show that firstly, the temperature reduction and pore fluid freezing improves these rock?s mechanical properties. Secondly, the dependency of rock properties to climate changes depends on the type and shape of its porosity as well as porosity percent. The improvement of rock mechanical properties in jointed rocks exceeds rocks with spherical pores. Finally, maximum changes in rock?s properties occur at [-10, 0]°C, which includes the phase transition of pore fluid. Keywords: Temperature; Rock Mechanical Properties; Pore Fluid; Porosity.

Feb 27, 2013

By Wang Zuoyu

The manuscript of this paper was not available for publication when the Proceedings went to press. Should the author elect, he may distribute copies to the time of the Symposium.

Jan 1, 1986

By Yuting Xue, Danqing Gao, Brijes Mishra

Heterogeneity and discontinuity significantly affect rockmass strength. Past studies have largely used arbitrary scaling approaches to produce rockmass strength from laboratory rock tests. This paper proposes a stochastic approach to produce rockmass strength from laboratory rock tests. Based on the laboratory data, MATLAB with an extreme value stochastic model generated a database for each physico-mechanical property of the rock. Then finite-difference software FLAC2D simulated laboratory-sized rock specimens. Random material properties in MATLAB were generated using the grids developed in the numerical model. The random properties were then applied to the final FLAC2D model. Model runs simulated the approach performed in the laboratory. The results from the model indicate that a stochastic approach produced compressive strengths that were lower than those from the deterministic approach. Failure modes for each specimen were different from those observed in the laboratory. In addition, random density also influenced the failure mode, highlighting the importance of stochastic analysis in rocks.

By M. Soya, M. Imazu, Ö. Aydan

"SUMMARY Taru-Toge tunnel is being constructed using drilling-blasting technique as a part of expressway project connecting Shin-Tomei Expressway and Chuo Expressway at the boundary of Shizuoka and Yamanashi Prefectures in the Central Japan. The maximum overburden is about 400 m. The authors have been carrying out a monitoring program to measure dynamic and multi-parameter responses of tunnel during and soon after the blasting operations using a multi-parameter monitoring system (Acoustic Emissions (AE), Electric Potential (EP), Temperature (T), Humidity (H) and Air Pressure (P)) and stand-alone type compact accelerometers developed by the first author. The measured response involves dynamic vibrations and other measurable parameters caused by blasting as well as by stress-redistribution around the tunnel face. This is one of the first attempts in the world to measure the response of rock mass caused by blasting at a very close vicinity of the tunnel face. In this paper, the authors present the outcomes of this unique monitoring study on the dynamic responses of the Taru-Toge tunnel during excavation and discuss their implications in actual applications. INTRODUCTION The real time monitoring of the stability of tunnels are of great importance when tunnels are prone to failure during excavation such as rockbursting or squeezing (i.e. Aydan et al. 1993, 2001). Experimental studies by the authors showed that rock indicates distinct variations of multi-parameters during deformation and fracturing processes (i.e. Mizutani et al. 1976; Aydan and Daido 2002; Aydan et al. 2003, 2011). These may be used for the real-time assessment of the stability of rock structures. An application of this approach was done to the Taru-toge tunnel a part of expressway project connecting Shin-Tomei Expressway and Chuo Expressway at the boundary of Shizuoka and Yamanashi Prefectures in the Central Japan (Imazu et al. 2015). The parameters measured involve electric potential variations, acoustic emissions, rock temperature, temperature and humidity of the tunnel in addition to the measurements of convergence and loads on support members during the face advance."

Jan 1, 2016

By David D. Spencer

As in many other areas of the Mexican economy, the legal rules applicable to mining in Mexico have been changing fast. Mexico&apos;s mining sector is opening up to levels of international participation that were unforeseeable just a few years ago. Over the last several years, Mexico has made dramatic changes in its trade and investment policies. Many of these changes have their roots in the administrations of Miguel de la Madrid and perhaps even Jose Lopez Portillo. However, the current administration of President Carlos Salinas must be given credit for articulating, advancing, promulgating and implementing these changes. Just a few short years ago, few people believed Mexico would repeal so many of its restrictions on foreign investment and lower its average tariff level from something around 100% to less than 10%, where it is today. NAFTA and mining The North American Free Trade Agreement (NAFTA) is the most comprehensive international expression of Mexico&apos;s new policies. Except perhaps for the agreements establishing the European Union, NAFTA is the most detailed trade agreement ever written, consisting of about 2000 pages. The provisions of NAFTA with the greatest relevance to the mining industry include the chapters on investment and government procurement. Many mining companies may also find the temporary work provisions relevant. Finally, no discussion of NAFTA and the mining industry would be complete without some mention of the North American Agreement on Environmental Cooperation, the so-called Environmental Side Agreement.

Jan 1, 1994

By Harold Wagner, Prakash Donde, Larry H. Heflin

INTRODUCTION The Washington Metropolitan Area Transit Authority is responsible for the planned 166 kilometer (103 mile) Metro rapid rail transit system in Washington, D.C. Some 117 kilometers (72.8 miles) of this system is in operation and contains 30.6 route-kilometers (19 miles) of rock tunneling. To complete the planned system an additional 1.6 kilometers (1.0 miles) of single track tunnels in rock are planned and additional contracts will consist of 4 kilometers (2.5 miles) of twin tunnel, resulting in 8 additional linear kilometers (5 miles) of single track tunnel contracts yet to be offered in soft ground. Three recent contracts in soft ground included the New Austrian Tunneling Method (NATM), along with conventional tunneling, as a bid option. Section E5a, Fort Totten Station and Tunnels, was the only one of the three to be constructed using the NATM option. This is the first application of the New Austrian Tunneling Method in soft ground in the United States. This paper will concentrate on the Fort Totten Station chamber NATM design, construction, and the instrumentation readings and evaluations which lead to an engineering back analysis which allowed a refinement of the bid design, resulting in a faster, more efficient construction. Design of the Fort Totten Station and Lines was done by Sheladia Associates. The design team included Greiner Engineering and Jenny Engineering with Mayreder-Consult of Austria, who was responsible for NATM design and NATM construction consultation.

Jan 1, 1991

THE QUARTETTE Mine near Searchlight, NV, a mine that first operated in the 1890s, could begin processing ore again by September. Jetco Enterprises Inc. plans to work through the tailings and ore close to the surface followed by plans for an openpit mine. It is one of at least three new mining efforts in the region, the Associated Press reported. Another is north of Searchlight, with yet another across the Colorado River in Arizona, east of Bullhead City. Gold mining is rare in southern Nevada. The area generally lacks the rock type that contains gold deposits. Restrictions on federal wilderness areas and protections for the desert tortoise also play a role. Gold veins in the region are generally small and erratic in length and height, Bill Durbin, a geologist and chief of southern Nevada operations for the Nevada Division of Minerals told the Associated Press. L.R. Tad Tinnell, president of Jetco Enterprises, has long eyed the mine. From 1993 to 1995, he explored and drilled on the property, which was still owned by Searchlight Mercantile.

Sep 1, 2013

By J. F. T. Agapito, J. B. Page

This paper describes part of a geotechnical study based on stress determinations and convergence measurements conducted to assess the long-term stability of an experimental room-and-pillar oil shale mine. A rock mechanics program was initiated in 1971 at the Colony Mine as part of a large study conducted for the design of a commercial operation. The Colony Development Operation is a joint venture currently consisting of four active members; Ashland Oil Inc., Atlantic Richfield Company (Operator of the project), Shell Oil Company, and The Oil Shale Corporation. Although oil shale commercialization plans are presently suspended, rock mechanics instrumentation has been continued as part of Colony&apos;s policy in maintaining readiness to proceed with a commercial shale oil plant when national energy policies became better defined. The property is located in the southern edge of the Piceance Creek Basin in northwestern Colorado, approximately 200 miles west of Denver. Experimental mining operations were conducted from 1965 to 1972 with one of the major objectives of the pilot mine being the assessment of opening and pillar sizes for the determination of extraction ratio and life of the property. Mining was conducted in a 60 foot thick portion of the Mahogany Zone in the Parachute Creek Member of the Green River Formation, at depths of 600 to 850 feet by a one-bench system. Pillar dimensions were 58 feet by 58 feet and rooms were 55 feet wide.

Jan 1, 1977

By Mark Gershon

Most recent work in the field of mine production scheduling has focused on either the computerization of the traditional methods or the development of sophisticated mathematical optimization models. Yet it is clear to all concerned that the optimizers need to be made more practical and the traditional approach needs to be made more optimal. This paper, along with another recent paper (Gershon, 85) open a middle ground between these two approaches. In that recent paper, a heuristic procedure for production scheduling was introduced. Here, a series of short term optimizations are used in a creative manner to approximate the true long term optimization. Since these small optimizations are aimed at blending to meet production quality specifications, this approach is most applicable to commodities where the blending function is very important such as coal, cement, phosphates or iron, to name a few. The traditional and the optimization approaches are so far apart that their&apos; advocates have difficulty identifying with the other approach. This is especially true concerning the difficulty of understanding the optimization models for those not trained in the field of operations research. This paper takes the position that the pro- 120 per role of the operations researcher is to provide not only useful and advantageous approaches, but practical, understandable and implementable ones as well. This is the goal of the paper in describing a new approach, consistent with the traditional methods and aimed at approximating the results of the optimizers.

Jan 1, 1986

By L. H. Munson, E. H. Carbaugh, D. E. Hadlock, L. F. Munson, R. L. Gilchrist

As a result of the Three Mile Accident and because of evidence indicating radiation protection problems, the U.S Nuclear Regulatory Commission (USNRC) undertook a major effort, with the assistance of the Pacific Northwest Laboratory (PNL), to analyze radiation protection programs at 47 commercially operated nuclear power plants. This effort, the health physics appraisal program (HPAP), using a modified management oversite and risk tree analytical logic methodology (MORT) which consisted of analytical trees with applicable questions for each tree, was subsequently extended to include USNRC licensed uranium mills. In the uranium mill appraisal, a team of four senior radiation safety professionals spent a week at each mill evaluating the total health physics program. Prior to the HPAP, the USNRC inspection efforts were designed to determine if the licensees were fulfilling the requirements of the code of federal regulations and the mills source material license. The HPAP, however, was designed and structured to facilitate an integrated look at the total program. It is also directed into areas for which explicit NRC regulatory requirements may not currently exist. The latitude of the HPAP was designed to allow professional judgement in the evaluation of program adequacy, because merely meeting the explicit regulatory requirements does not necessarily ensure an adequate and effective health physics program. The results of the first eight site visits and the generic health physics problems identified within the uranium milling industry will be identified in this paper.

Jan 1, 1981

By G. Bryant, P. Ziemkiewicz

Acid mine drainage (AMD) from both abandoned surface and underground mines is a serious problem. The flow of water and changes in quality over time from abandoned mines is important in determining remediation strategies. Acid mine drainage from surface mines is estimated to last for 10-20 years, while estimates of acid drainage from underground mines vary from 10- 100s of years. Fifteen underground mine discharges in West Virginia were studied to compare water quality changes between 1968 and 1999 to see if our data are consistent with other studies. Each of the discharges were categorized into one of three groups: undisturbed since 1968, affected by surface mining since 1968, and reclaimed. Comparing water quality between 1968 and 1999, the discharges in the undisturbed category showed a 35 to 95% improvement in acid concentration and a 40 to 99% reduction in iron concentration. The discharges affected by surface mining showed the most dramatic improvement. For acidity, iron, and aluminum, the percent improvements were all above 44%, and in most cases in the 70 to 99% range. In the reclaimed category, one of the four discharges declined in water quality. Discharge 82 showed a 76% increase in acidity, and iron and aluminum concentrations worsened by 58 and 96%. However, discharges 15 and 74 improved in water quality with a 94% acid load improvement and a 95% iron load improvement at both sites.

Jan 1, 2000

By Howard E. Banta

From Alaska to Florida and California to Maine, the National Forest System (NFS) is host to unprecedented levels of prospecting and development. The NFS is large (191 million acres), geologically attractive from the mineral standpoint and relatively unexplored. Significant recent finds and developments involve silver, gold, platinum group metals, molybdenum, cobalt and phosphates. Exploration and development are closely regulated, but most of the NFS is open. The Forest Service endeavors to be a good host to the mineral industry, but increasingly is asked or forced to delay or disapprove mineral projects to protect the environment.

Jan 1, 1984