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By R. Perlo

"INTRODUCTION Peoples’ and operators’ safety in construction are tightly linked to the engineering choices, as much as the necessity of reducing time and costs of realization. Therefore, it is of paramount importance to address them properly from the earliest stage of the design, identifying the risks connected to the work and the variability of such during the different phases of the project. Risk is often measured as the expected value of an undesirable outcome. Regarding to occupational safety and health, the risk is the likelihood that a person may be harmed of suffers adverse health effects if exposed to a hazard. This combines the probabilities of various possible events and the assessment of the corresponding harm into a single value. However, the actual occurrences are often more complex than a single binary possibility case. In a real case scenario, with several possible accidents, the total risk is the sum of the risks for each different accident, provided that the outcomes are comparable. The semi-automatic tunnel support system along with its erector machine proved to be a solution with improved structural performance, able to reduce the time and yet to deliver an enhanced, quality-aware and safer working environment for the operators. The implementation of the system provides the engineers, the contractors and the owners with an effective alternative option shortlisted in 2015 for the ITA Award for the Safety Innovation of the Year. In a market industry driven by safety and time constrains the efficiency shall be the ultimate goal, in order to provide solutions able to negotiate with the most challenging ground conditions. In this paper, the authors describe the recent developments on regard of this whole new tunnel support system, including design approach and presenting related case histories OFFSETTING THE RISKS Considering the above factors, from the manufacturers’ point of view, an effective way to limit the construction risks is to focus on the material and technological characteristics, their application and the risks related to them including any residual risks. Finally addressing the construction needs also involves time and cost-effective solutions. The path to follow is an integrated approach where the efficient management of the risk is supported by a flexible, user-friendly, and time effective product that is able to provide a safe, reliable and viable solution to address the construction requirements. Therefore, in a market sector driven by safety and time constraints, the efficiency is a key goal, in order to avoid redundancy and yet to deliver a safe working environment able to meet the construction schedule. The safety of all the parties involved is given by stable working conditions, either for the workers, or the operators and eventually the public. Therefore, the solutions provided should ‘strengthen’ the overall condition and such “to limit or to reduce the deformations within acceptable designed limits and to prevent [the tunnel] to collapse” [1: Clause 207.1.4]."

Jan 1, 2018

By Donald J. Worth

When Eugene Bailey asked me to contribute to this session on "Canadian exploration - 1976", it took a little coaxing before he got me to agree. My immediate reaction was, what could i say about Canadian exploration that already had not been said a hundred times in the past few years; secondly, why include a banking person in such a discussion? Everyone knows banks only come into the picture after the discovery has been made and feasibility well established and validated. Rather than wrestle with these misgivings, I decided to take the easy way out and go on blind faith in Eugene - that is, he asked me so he must think that I could come up with some useful thoughts and at least touch upon some of the pros and cons of exploration in Canada. The object of the whole exploration exercise is to Find economic deposits, once they are found, one cannot really move them elsewhere to mine them. It follows, therefore, that we should really be speaking about the pros and cons of mining In Canada and my treatise will eventually lean in this direction. In any event and before getting down to the pros and cons, let us take a quick look at the history of mineral resource development in our country since the end of world war II. At that time, we were producing well under one billion dollars worth of mineral products including hydrocarbons.

Jan 1, 1976

By M. Scaggs, K. Phillips

"Coal Worker’s Pneumoconiosis (CWP) is an occupational lung disease caused by chronic exposure to respirable mine dust. After decades of steady decline, CWP incidence appears to be on the rise since the mid-1990s, particularly in some regions of Appalachia. Alarmingly, many of these cases have rapidly progressed to the most advanced form of CWP, referred to as Progressive Massive Fibrosis (PMF). Most of what is currently understood about respirable mine dust has been gleaned from routine regulatory monitoring, which tracks total mass concentration of respirable dust (mg/m3) and, less frequently, silica mass content. This paper focuses on the use of thermogravimetric analysis (TGA) as a way to provide basic characterization of the whole composition of the dust, allowing it to be classified into three mass fractions – coal, carbonate, and non-carbonate minerals. TGA was conducted on 59 dust samples collected by miners from eight coal mines in central Appalachia, and the results are discussed in terms of differences between mines, regions, and primary occupations. Consistent with prior results on area dust samples from some of the same mines, results of the personal samples generally show that the coal mass fraction of the dust is relatively low. Carbonate and non-carbonate minerals thus tend to make up the bulk of the dust mass, and vary across occupations and specific mines. INTRODUCTION After nearly four decades of decline, the prevalence of Coal Workers’ Pneumoconiosis (CWP, or “black lung”) in the US has been on the rise since the mid-1990s (Laney et al., 2014; Laney et al., 2010; Suarthana et al., 2011; Pollock et al., 2010; Antao et al., 2005; Blackley et al., 2016). Particularly alarming is the number of cases of progressive massive fibrosis (PMF), which is the most advanced form of the disease (Pollock et al., 2010; Antao et al., 2005; Blackley et al., 2016; Laney et al., 2017). A recent study by Laney et al. (2017) observed 192 US coal miners participating in the Coal Workers’ Health Surveillance Program (CWHSP) who had been diagnosed with PMF since 2000. Of the 163 (85%) that had a normal radiograph on file to use as a baseline, 27 (17%) of these individuals had progressed from a normal radiograph to PMF diagnosis in less than 10 years. Moreover, 162 (84%) of the individuals in that study worked in KY, WV or VA, and 169 (88%) had only ever mined underground. Blackley et al. (2016) also reported on a group of 60 PMF cases that were discovered by a single black lung clinic in eastern KY. Since seeking care at such clinics and participation in the CWHSP are voluntary, and could be influenced by a number of factors, these recent reports may well overestimate the degree of resurgence in severe disease (i.e., versus disease that was previously under-reported). Even so, they highlight a critical need to better understand the cause(s) of disease development and progression – such that effective interventions can be devised."

Jan 1, 2018

By S. Dereski, G. Chancellor

"INTRODUCTION Barrick Goldstrike underground mine is located in Northern Nevada on the Carlin trend. The underground mine produces approximately 1.5 to 1.8 million tons a year and approximately 400,000 ounces of gold a year. The mine is comprised of two main mining methods, underhand drift and fill and long hole stopeing. The mass blast project stated in 2012 as Value in Use project between Barrick, Southwest Energy and Orica, the goal of this project is to be able to blast an entire drilled stope in one blasting event instead of taking multiple blasts. This will improve productivity by eliminating intermediate blasts, reducing additional blast time, eliminate drill hole cleaning due to the previous blast. Project implantation started in the fourth quarter of 2013 and mass blasting has been common practice throughout all of 2014. STOPPING PRACTICE AT GOLDSTRIKE BEFORE MASS BLAST PROJECT The production from the Goldstrike mine is approximately 70% from stopes. The timely completion of all stoping blocks is imperative to maintaining the plan, delays in the execution of any particular block can have detrimental ripple down effects as neighbouring stoping blocks become delayed. Before the implementation of this project the standard practice for Goldstrike was to: 1. Drill the entire stope 2. Blast a bottom shot, normally between 10 feet and 20 feet off the bottom of the slot rings. This would be mucked out before the next shot 3. Blast a pull through shot, this included the raise and one or two production rings. Again mucking this out before the next shot 4. Blast production rings, one or two more blasts depending on stope size. In most cases between each of these blasts the holes in the other rings of the stope would have to be cleaned. This meant either cleaning manually using air and water, or mechanically cleaning with a bench drill. In many cases this resulted in delays in completing the stoping block."

Jan 1, 2015

By Jie Li, Longxiang Li, Wenbing Guo, Gaobo Zhao, Yuhang Hu

Surface subsidence caused by underground longwall mining is a very complicated process in time and space, influencing building and structures on the surface of the mining area, including houses, pipelines, and highway. The field monitoring data of surface subsidence are essential for protecting them. This study investigated the dynamic and residual subsidence characteristics of both the surface and the highway over a 730-day monitoring period on a longwall panel. Three monitoring lines (Lines 1–3) were established to monitor the subsidence process, and three stages were identified: initial stage of surface subsidence, active period of surface subsidence, and residual subsidence deformation stage. The maximum subsidence value on the highway (1,786 mm) was smaller than that on the surface (2,094 mm), and the maximum subsidence velocity on the highway (41.7–50.8 mm/day) was also lower than that on the surface (66.7 mm/day). During the residual subsidence deformation stage, both the surface and highway subsidence velocities decreased to below 0.6 mm/day. Furthermore, differences in subsidence characteristics between the surface and the highway were analyzed, with the subsidence value on the highway always being less than that on the surface, while the subsidence velocity during the residual deformation stage was not always lower. This could be attributed to the influence of dynamic loads from vehicles, which could induce additional residual subsidence on the highway. Further investigation into this phenomenon will be conducted in future research.

Jul 1, 2023

By George A. Snyder

The presence of moderate to high concentrations of colloidal clays in coal preparation plant waters can cause serious operating and economic problems for a coal company. Among the host of possible problems are the following: 1) Poor separation of clays in the plant thickener, resulting in: a) Increased ash in the clean coal. b) Increased specific gravity of the wash water and decreased coal recoveries at the desired quality. c) Increased thickener operating costs in trying to overcome the problem. 2) Decreased solid concentrations in the thickener underflow and increased pumping requirements to meet solids withdrawal requirements.

Jan 1, 1979

An AFM has been applied to study in situ the adsorption of oleic acid on fluorite in aqueous solutions. The AFM images show that fluorite surface becomes smoother with the adsorption of 7 × 10-5 M oleic acid solution at pH 9. Force measurement shows that fluorite is strongly positively charged in water at pH 6, suggesting a neglectable surface carbonation of fluorite. The adsorption of oleic acid at pH 9 renders fluorite more and more negatively charged. The surface morphology change of fluorite as shown by the AFM images suggests that oleic acid chemisorbs on fluorite at pH 9. Increasing temperature can help increase the adsorption of oleic acid on fluorite. It may also improve the lateral polymerization of unsaturated oleic acid on fluorite as suggested by the smoother mineral surface in oleic acid solutions at an elevated temperature.

Feb 23, 2014

By Fred T. Towne

There are a number of air classifiers manufactured throughout the United States and the rest of the world. The classifiers manufactured by Alpine, A. G. of Augsburg, Germany, are unique in their abilities. It is this uniqueness that I wish to delve into and in this respect we will limit this discussion primarily to the classifiers as manufactured by Alpine. It has been reported in the past that these classifiers were introduced into the. United States in the late 50's. Until the introduction of the Alpine Classifiers, air classification seldom produced a satisfactory fractionation of a product below 45 microns (325 mesh) or above approximately 22 mesh. It has been a common practice to classify fine materials which used water as a carrier medium The use of centrifuges are today producing thousands of tons of finely partitive powders in the very small particle size range. The use of centrifuges in connection with wet grinding mills has increased the rates of production of these mills considerably.

Jan 1, 1965

By Stefan Mede

Robot Supported Moulding—this is the name of Herrenknecht Formwork’s entry to the world of automated segment production. What had been considered impossible for a long time, has been achieved by Herrenknecht experts together with the Swiss company Marti AG: unmanned segment production on the working line. The moulds open and close autonomously with the help of a hydraulic system. A robot cleans and greases the moulds at one work station and inserts the injection sockets at another. The next step will include further automation and digital networking of all processes from production to installation in the tunnel.

Jun 13, 2021

By L. Alan Weakly

The Powder River Basin of northeastern Wyoming and southcentral Montana contains the largest strip minable reserve of compliance coal (0.27 kg or 0.6 or less Ibs of sulfur per million Btu) in the United States. In mining parlance, it is the mother lode. Wyoming's portion of the Basin is called the Southern Powder River Basin (SPRB). It has been the nation's top coal producer for the past nine years. And based on 1997 production statistics and estimated strippable compliance coal reserves, Wyoming should remain the nation's top producer for the next 51 plus years. In August 1994, ME featured 10 articles that covered all aspects of coal production in the SPRB. In this issue, five authors update the 1994 articles and provide a pre- diction of what the Basin will look like at the turn of the century. In addition to this article, the titles and authors of the other five articles include: ? "Geology of Wyoming's Powder River Basin coal field," by Gary B. Glass and Robert M. Lyman. ? "Coal quality challenges in the Powder River Basin," by Sharon Roness, Richard A. Turpin and Robert A. Young. ? "Markets for Southern Powder River Basin coal," by , Patti J. Best and Patrick W. Wright. ? "Evolution of mining equipment in the Powder River Basin," by Kenneth R. Miller and James L. Long. ? "Hauling coal into the 21st century," by Dave Willis and Will Cunningham.

Jan 1, 1998

By A. E. Koski

This paper describes the implementation of specialized software in mine planning at the Cleveland-Cliffs' managed Empire Mine on Michigan's Marquette Iron Range. The application puts together years of mining experience on the eastern end of the Marquette Range beginning in the early 1960's. The Empire Mine, in its thirty-fifth year of production, uses the software to model a complex and highly variable low grade magnetite ore body, capturing the economics of mining and processing to the final product. With special attention given to geostatistical methods, the software is used for all geologic modeling, ore reserve estimation, ore control, pit design and short and long range planning.

Jan 1, 1999

By R. W. Wotring

Mr. Chairman, Officers, Members and Guests of the AIME, I want to express my appreciation for the privilege of being on your program at this meeting. Coal mining, in recent years, has become much more competitive than it formerly was. To stay in business, it has been necessary for coal mines to mechanize. This, in itself, has not been enough for after one has mechanized his mine, he must keep replacing the equipment with the latest type and model machines. We, at Olga, have been doing this very thing for the past several years. Olga No. 2 Mine is located at Caretta, West Virginia, in McDovell County, about twelve miles south of Welch, It is a shaft mine, operating in the No. 4 Pocahontas seam. The thickness in the area, we are presently mining, varies from five to six feet. In some areas the immediate roof is slate, ranging in thickness from a few inches to four and five feet; in other places, the sandstone lies on top of the coal, This sandstone is about twenty-five feet thick.

Jan 1, 1961

By Ingemar Marklund

INTRODUCTION Today at LKAB, the primary mining method used is sublevel caving, independent of ore-body size, shape, dip, and geographical location. The mining of small ore bodies with relatively flat dip involves a lot of develop¬ment work, a large initial investment, big dilution, and large ore losses. In 1975 serious investigations into other possible methods, especially for those small ore bodies which do not lie in direct contact with other ore bodies, began. Different methods were studied and a number of in¬teresting ideas came from Russian mines. An analysis was made of one of the proposed methods, sublevel benching, in which mining is carried out from raises, and which uses the throw from the blast to place the broken ore. However, there were reservations about working in big open rooms at great depth, and doubts about the possibility of getting acceptable drilling results in an acceptable environment from raised platforms. Testing was therefore delayed for a time. However the investigations continued and in the fall of 1976, it was decided to try vein mining in a small ore body (Indian) (see Figs. 1 and 2). MINING RESULTS The results are now available from the mining of Indian and are as follows: Ore plan area 1200 m2 Level height 50 m Ore volume 60 000 m3 Ore tonnage 270 000 t Iron content 62% Dip 0.69 rad (40°) Ore thickness 14 m Ore compressive strength 26 MPa Ore C-factor (fracture density) 0.21 Hanging wall compressive strength 28 MPa Hanging wall C-factor 0.27 About 40 000 m of the holes were drilled by ring drills with an average productivity of 85 m/shift; loading of a round (2 rows, 750 m of hole) was usually accomplished in one shift. The total ore recovery was about 270 000 t with an average iron content of 59%, and three to four shifts were required per round (4700 t) to load. The principal of "throwing" the rock during blast¬ing worked well, and no ore remains on the footwall. ROCK CONTROL Before mining commenced at Indian, it was dis¬covered that the rock strength in its vicinity was rela¬tively poor. Since the ore is flatly dipping, and mining was to take place with open rooms, the strength of the hanging wall was of great importance. A supplementary program of exploration drilling was done during the fall of 1976 in order to assess fracture spacing and rock strength from the drill cores. Results showed that the strength of the hanging wall was low because of the many fractures. A decision was made to try cable bolting of the hanging wall by extending some of the ordinary blast¬holes. Cables (20 mm diam) were grouted in these larger holes and the rest of the hole was then utilized for ordinary loading (see Fig. 2). About 100 bolts altogether were installed and, to date, only small falls have occurred and the hanging wall is holding. Its exposed area is 2100 m2 DEVELOPMENT WORK On the 350-m level, four crosscuts (two per mining room), one longitudinal drift, and two elongated drifts (one per raise) for the raise climber were developed as shown in Fig. 1. Of the 230 m of drift, 60 m were in ore and the rest in waste. For mining room A alone, a total of 115 m of drift were needed with 30 m in ore. The drift dimensions were about 4.5 X 5.5 m. In the drifting on the 300-m level, two connecting drifts were driven from one existing transport drift forward to the respective raises. The total development was 93 m, all in waste (Fig. 1). The two raises having a length of 80 m each were driven at an angle of 0.68 rad (39°) from the hori¬zontal. They were driven along the footwall contact with a separation of 30 m and had an area of 10 m2. LONG-HOLE DRILLING The drilling of long holes with the ring drilling unit began in the fall of 1977 in raise A. The equipment consisted of an Alimak raise climber, equipped with a lower platform from which the charging was done.

Jan 1, 1982

By R. L. Godfrey

The Custom Coals advanced coal cleaning plant will be designed with a unique blending of existing and new processes to produce two types of compliance coals: Carefree Coal? and Self-Scrubbing Coal?. Carefree Coal will be produced by cleaning the coal in a proprietary dense media cyclone circuit utilizing fine magnetite to remove up to 90 percent of the pyritic sulfur and correspondingly greatly reduce the ash. While may utilities can achieve full S02 reduction compliance with Carefree Coal, others face higher sulfur reduction requirements due to the higher sulfur content of their existing fuel supplies. For these circumstances, a patented Self-Scrubbing Coal will be produced by taking Carefree Coal and pelletizing limestone-based additives with the finest fraction of the clean coal. These technologies will enable over 150 billion tons of non-compliance U.S. coal reserves to meet compliance requirements.

Jan 1, 1995

By E. S. Forbus

A process for producing reductive bleach in-situ in kaolin slurries has been developed. The bleach is formed by mixing an iron sponge powder (-325M) with slurry treated with SO2. The process has been successfully demonstrated in production, and applied to several grades. The color, brightness, and viscosity of the bleached product is equivalent to or better than that of product bleached with commercial sodium hydrosulfite . The tested products can be bleached at a cost, which is 38-54% of those associated with the use of commercial bleach.

Jan 1, 1993

By Apostolos Vrakas, Georgios Anagnostou

"INTRODUCTION The small strain assumption routinely made in tunnel analyses remains sufficient from an engineering point of view as long as convergences do not exceed 10%. More specifically, small strain theory assumes that deformations are so small (in relation to the size of the underground opening) that any geometric change in the continuum can be disregarded (Fig. 1a). In fact, however, the geometry is updated during loading (or unloading) according to large strain theory and thus equilibrium and stiffness are evaluated on the deformed configuration of the continuum (Fig. 1b).In problems involving large deformations, where the undeformed and the deformed tunnel geometry differ significantly, small strain theory leads to erroneous and sometimes even nonsensical results (i.e. it can predict wall displacements even greater than the excavated radius under conditions of very low stiffness and strength, high in situ stress and low support pressure). This can easily be verified from the widely applied relationships for the ground response curve. For example, in the ideal case of linearly elastic behaviour, the convergence of an unsupported opening equals (1+?) s0 / E (where E, ? and s0 denote the Young’s modulus, Poisson’s ratio and initial isotropic stress, respectively) and is greater than 100% for E < (1+?) s0. Although convergences are less than 10% in the great majority of tunnelling projects, very large deformations may take place when tunnelling through weak rocks under a high overburden (Fig. 2). This paper will first present a very simple and practicable way to account for large strains, based entirely on the results of routine small strain analyses, and will subsequently show the importance of addressing large strains in tunnel analysis and design with reference to three typical case studies of tunnelling in squeezing ground."

Jan 1, 2016

By F. A. Molloy

As a result of feasibility studies made in 1975 a 3-0 seismic reflection survey was shot over part of the Veendam salt pillow during 1978-1979. The Zechstein salt pillow, located in the northeast of the Netherlands near the town of veendam, occurs at a depth of 1400 m and contains three carnallite rich horizons over an interval of 300 m below top salt. MgCl2 brines are produced from these layers as feedstock for a magnesia plant, which starts up in 1981. Prior to the acquisition of the seismic data four wells had been drilled. The thickness of the carnallitite layers encountered in these wells varied between 50 and 125 meters. In view of these variations it was necessary to obtain a reliable isopach of the different layers. The 3-0 seismic survey covered an area of ± 4x4 km with a sampling interval of 20 m in all directions. The data was recorded it an area array using a 120 channel instrument. Final presentation of the data was in the form of 3-0 migrated acoustic impedance cross sections. The quality and resolution of the seismic data allowed reliable structural and isopach mans to be made. It was shown that the carnallitite layers are continuous over the area surveyed, whilst local thickening is "fault" related. Having this information brine production locations could be choosen in the thicker parts, allowing maximisation of production potential whilst avoiding faults and fulfilling mining regulations. A subsequent benefit of this approach is the possibility of using the seismic data to predict ore grade. Using the available wells as calibration points the acoustic impedance response of the seismic at the well was matched to the ore grade found. From these points a synthetic section was made with varying ore grades. Pre¬liminary results are encouraging and the liability of this predictive tool will be evaluated in the light of future drilling.

Jan 1, 1981

A comprehensive understanding of the effects of autoclave configuration (batch, semi-batch, continuous) on the residence time necessary to achieve a target conversion is a prerequisite for design of commercial scale autoclaves. Particle size distribution, mineral and reagent concentrations, temperature and mixing also influence the conversion. This paper outlines the bases of using test data to predict performance of commercial scale autoclaves. Recommendations for coordinating test program design with selection of scale-up method are provided. Examples are given to illustrate the different levels of engineering effort needed to meet corresponding levels of design optimization and accuracy.

Jan 1, 1998

By Yves C. Lizotte

Although blasting remains the most inexpensive method of fragmentation in hardrock mining, the significance of the costs of blast-induced rockmass damage in terms of mining efficiency and safety is becoming increasingly recognized. There is no straightforward and systematic method of adequately measuring blast damage in on-going mining operations. This paper considers various techniques available to measure blast damage, making particular reference to recent underground hardrock mine studies. It concludes by proposing a damage audit procedure for integration into routine mine production control.

Jan 1, 1996

By H. Akgun

Design of plugs for abandonment of boreholes and shafts may be governed by the bond strength between the plug and host rock. This paper presents the results of push-out tests on cement grout plugs in salt. Two expandable cement grouts have been tested. The average interface shear strengths ranged from 2 to 12 MPa. Peak shear stresses at failure, assuming an elastic stress distribution along the interface, were up to eight times higher. Standard deviations commonly reached 20%. Dissolution along the interface was observed, and may have been enhanced by clay inclusions in the salt. This dissolution appears to have reduced bond strengths. Application of the results to the design of plugs for larger openings (e.g. shafts, drifts, or boreholes) is discussed.

Jan 1, 1991