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By Caibin Wu, Bin Xie, Jiaqi Tong, Ningning Liao, Chong Zeng

Understanding the energy-size reduction relationship is vital to grinding process; therefore, this paper aims to show the energy-size reduction of magnetite-calcite binary mixture in a laboratory wet conical ball mill. Single magnetite, single calcite, and blended magnetite-calcite mixture at three weight ratios in four particle sizes were ground in a laboratory wet conical ball mill at four grinding time periods. The results showed that the particle size distribution of both fine particles and coarse particles of single and mixture ground product fitted well with the PSD computed by Rosin–Rammler-Benne function. The larger mass percentage of calcite is, the higher t10 of binary mixture ground product is. On the contrary, t10 in the mixture decreases as the percentage of magnetite in the mixture increases. The different breakage behaviors in blended samples are due to the hardness and particle size. The results of calculated ratio of energy absorption factor showed that the calcite consumed more energy in the breakage process of binary mixture than ground alone. The JK size-dependent breakage model based on the t10 method fits all the experiment data, be it generated from pure minerals, mixtures at different weight ratios, or each component separated from the mixture.

Jun 4, 2022

By Neil D. Donnell, O&apos

Bituminous sands of the Lower Cretaceous McMurray Formation in northern Alberta constitute the ore for the surface mining operation at Syncrude Canada Ltd. These sediments represent a complex succession of fluvial, estuarine and marine depositional environments. Grade prediction is realized through a combination of geological interpretation, computer modeling, and reference to past mining experience. Accurate forecasts of feed grade permit reliable predictions of volumes for removal to meet budgeted synthetic crude oil production. This planning facilitates efficient allocation of mining equipment and resources. The feed grade to the Extraction Plant is monitored at various points along the delivery system.

Jan 1, 1984

By H. N. Dougherty

"The National Institute for Occupational Safety and Health (NIOSH) Office of Mine Safety and Health Research (OMSHR) ventilation gallery was used to study methane-air flows around a continuous miner mockup with water sprays and a scrubber fan. Methane gas was released from pipes located at the face to simulate face gas emissions. Methane concentrations and air velocities were measured while varying parameters such as airflow quantity, entry width (sump or slab cut), and face ventilation configuration (blowing or exhausting curtain). Test data showed a similar pattern of methane concentrations at both low and high airflow quantities, but a difference in the distribution of methane concentrations between narrow and wide entry widths. Most tests showed that blowing face ventilation was more efficient in diluting methane than exhausting ventilation, similar to observations made in previous empty gallery studies. The patterns of airflow and methane concentrations observed in this testing can further improve the understanding of airflow in and around the CM and face, promoting effective use of face ventilation to improve the health and safety of miners. INTRODUCTION Attaining an accurate understanding of airflow distribution at the continuous miner face is instrumental in maintaining a safe mining environment. US mining regulations require that sufficient airflow must be directed to the deepest penetration of the face and render harmless contaminant gases, as verified by the Mine Safety and Health Administration (MSHA). Currently, continuous miner face air readings can be taken in the last open crosscut and at the inby end of the curtain mouth. By measuring adequate airflow in a pre-determined area it is accepted that a sufficient quantity of that air exists to sweep the face of harmful dust and gasses. Unfortunately, due to the location inaccessibility, precise face velocity readings cannot be measured in situ. Face velocities may be estimated through computer-simulated programs based on laboratory models. Improving upon previous empty gallery testing and to more effectively determine representative face methane readings, a mockup of a continuous miner with water sprays and a scrubber fan was used in the current study to further refine face airflow conditions that would be closer to actual mining conditions."

Jan 1, 2016

By J. Payton

Public Service Company of Oklahoma began burning sub-bituminous coal in December, 1979. Initially PSO had a single source coal supply from Jacobs Ranch Mine, and in 1982 added deliveries from Clovis Point mine. Both are Powder River Basin (Wyoming) coal mines. In 1986 PSO began burning Oklahoma coal to meet Oklahoma's 10% native use law. PSO experienced random s lagging during certain blends of these coals. PSO installed a boiler performance system to help control the slagging problems from the various coal blends, to improve boiler efficiency, and increase total coal consumption.

Jan 1, 1990

By Robert R. Unterberger

The purpose of this paper is to summarize the research of the past sixteen years on three distinct methods of probing into solid rock. The first method is to use radar of the appropriate frequency. The second method is to use sonar. The third method is of recent vintage and uses techniques of nonlinear sonar also known as parametric sonar. The first two concepts, that of radar and sonar, are common to most people. Very few have heard of nonlinear sonar. Each of the probing techniques were investigated in order to overcome deficiencies in the former technique. Each has its advantages and disadvantages. It should be emphasized that all of these techniques for probing (or seeing) into rock are used in mines, and generally speaking not from the surface. Only in very special cases, such as certain very dry parts of Egypt or Peru, or, for example, the surface of the moon, will these probing techniques work from the surface. The reason for the development of these probing techniques has been to alert miners to possible hazards ahead of mining. Such hazards may be (1) old (unknown) boreholes connected with high pressure water zones above, (2) fractures that might connect to the Gulf of Mexico above the mine, (3) water-filled fractures that threaten the safety of miners, or (4) the discovery of dry faults ahead that can disrupt the planning of future operations.

Jan 1, 1983

By James K. Hallenburg

Geophysical borehole logging is a valuable and inexpensive tool for coal deposit evaluation, development, and production. In addition to the usual determinations of depth and seam thickness, geophysical borehole logs can effectively and accurately determine the coal ash, moisture, and heat contents in situ. Location and evaluation of the partings can be done quickly and accurately. Overburden character determination, such as roof competence, dewatering parameters, ripability, trace element content of the coal and overburden, and sulfur content can be done with existing tools and techniques. The quality of such determinations depends upon the quality of planning and calibration.

Jan 1, 1984

By V. Shchukin

According to the scientific views formed by the middle of nineteen seventies there should be no possibility of commercial diamondiferous kimberlites in the north of the west European platform. However a later analysis of the geological data gave rise to the concept that diamond bearing kimberlites would be present in the north but on the mineralogical level they would differ from kimberlites of South Africa and Yakutia. Further investigations resulted in the confirmation of these conclusions and with discovery at the beginning of 1980 of diamond bearing kimberlite pipes in the Arkhangelsk region.

Jan 1, 1995

By R. L. Braun

In situ chemical mining of primary sulfide ore requires distribution of injected oxygen in a large underground flooded region of broken ore. Although the maximum oxygen content of the leach solution will be dictated by the operating temperature and hydrostatic pressure, the actual oxygen content will be limited by the geometric dispersion of the injected oxygen, the rate of dissolution of oxygen, and the rate of convective circulation of oxygenated solution within the flooded bed of ore fragments. These factors are examined by a detailed theoretical analysis supported by laboratory experimental data. Typical results of the study illustrate that adequate dissolution of oxygen and circulation of oxygenated solution can be obtained in a column of 4 million metric tons of broken ore by using three gas injection lines and an oxygen injection to consumption ratio of 1.84.

Jan 1, 1974

By Basilio Giurgola, Federico Bonaiuti, Norbert Fuegenschuh

The North East Boundary Tunnel (NEBT) project in Washington, D.C. requires design and construction of several SEM adits which have to be built between lateral shafts and the NEBT-TBM Tunnel. The paper describes ground improvements, the actual excavation, and also the final lining works. Schedule and sequencing restrictions provided some unique challenges which had to be considered when designing and constructing these mostly short, but essential portions of the project

Dec 1, 2022

By Peter Chou, Pooyan Asadollahi, Danny Lin

To maintain flexibility and ductility of tunnels crossing active faults, various mitigation measures are being utilized depending on fault offset movements and seismic design criteria. Examples of those approaches are simple bell and spigot joint, articulated joint, and complex deformable longitudinal bolt and spring joint system with seismic isolation washer. This paper presents a summary of tunnel fault crossing mitigation approaches and design considerations using previous relevant experiences in California as well as case histories from Japan, Taiwan, Turkey, Greece, and Italy found in literatures. Comparisons are made between large and small diameter tunnels, transportation, and utility tunnels, as well as bored, mined and cut-and-cover tunnels. Recent innovations, such as Japanese and Italian techniques, for tunnels crossing active faults are also discussed.

Jun 13, 2021

By Harold J. Schock

This paper describes an experimental method for the monitoring of diesel-generated exhaust gas pollutants in a dead-ended drift for the purpose of assessing the effect of control approaches. Experiments were conducted to determine the relative merits of these ventilation configurations: no auxiliary ventilation, induction ventilation at the entrance to the drift, and ventilation of the dead-ended drift with positive displacement tubing. The drift used in this experimental work was approximately 105 ft. (32.0 mf long and slightly downsloping, with an average height and width of 8 ft. (2.4 m) and 28 ft. (8.5 m1 , respectively. The data were gathered for assessing these ventilation methods and for gathering data to support a computer model of the dispersion and mixing processes. For this drift, it was found that ventilation with positive displacement tubing provided the best removal of diesel-generated pollutants. Induction ventilation appeared to be the least effective of the three methods examined. A comparison was also made between personal monitoring and area monitoring. Results of this analysis showed that in regions of high concentration gradients, it was not possible to get good agreement between point sampling and personal monitoring. In well-mixed areas, good agreement between the two methods of monitoring was obtained.

Jan 1, 1980

By J. Kretschmann, K. van de Loo, J. Brune

In 2018, the German Federal government decided to phase-out the energy production using coal-fired power plants and to terminate lignite mining completely by 2038 at the latest. This decision will impact approximately 60,000 jobs. It will have an enormous impact on the socioeconomic development especially in all German lignite mining regions. To avoid economic and political friction, it is of utmost importance to achieve a sustainable transition towards a post-mining era and to offer residents in the mining districts perspectives for a good future that include adequate job opportunities. In this context, the German government is providing massive structural aids early on. As previous closure experiences from the German hard coal mining industry have shown, it takes at least a generation to overcome the effects of a strategic closing decision of this magnitude. Therefore, the planned closure process appears to be a long time at first glance. In fact, however, it is not.

Mar 2, 2022

By Madan M. Singh

Section 516 of Public Law (PL) 95-87, commonly known as the Surface Mining Control and Reclamation Act of 1977 (SMCRA), requires that underground coal mine operators must "adopt measures consistent with known technology in order to prevent subsidence causing material damage to the extent technologically and economically feasible, maximize mine stability, and maintain the value and reasonable foreseeable use of such surface lands, except in those instances where the mining technology used requires planned subsidence in a predictable and controlled manner..." Implied in the constraints of Section 516(b)(1) of SMCRA is a determination of what constitutes "material damage" to surface structures, renewable resource lands, and the capacity for sequential land use following underground mining. The authors have already briefly addressed the subject of damage criteria in relation to surface structures (Bhattacharya et al, 1984). In this paper, an attempt is made to provide quantitative guidelines to ascertain material damage to renewable resource lands, although the data available to establish these criteria are considerably more limited than is the case for surface structures. Besides, many more variables influence the severity of the impact at a given site, making the task of assigning stringent ground movement limits even more complex. This often necessitated use of professional judgement and occasional reverting to a qualitative approach. Hence the reader is cautioned at the very outset that the quantitative limits presented herein are approximate and are primarily intended to serve as rough guides for ascertaining the extent of damage to the renewable resource lands under consideration, and that depending on site-specific conditions the actual damage incurred may differ significantly from that predicted by the proposed criteria. The authors, however, feel that the criteria suggested are somewhat conservative, but realistic. The actual damage observed should generally be less severe than predicted by these criteria. It may also be clarified here that the term "subsidence", as used in this paper, implies the total phenomenon of surface and subsurface effects associated with the mining of minerals and not only the vertical displacement of the surface as is sometimes inferred in the literature.

Jan 1, 1984

By J. W. Hawley, G. S. Austin, L. A. Brandvold, J. Renault

Soil next to a smelter abandoned about 100 years ago near Socorro, NM was found, by the US Environmental Protection Agency (EPA), to contain high Pb concentrations. Detailed characterization of the soil by the New Mexico Bureau of Mines and Mineral Resources (Bureau) shows that the highest Pb concentration is in the clay-size fraction, although this fraction accounts for only 1 to 3 wt % of the soil. The depth of contamination, determined in areas relatively undisturbed since the smelter was abandoned, is no more than 76 mm (3 in.). Because of the soil's alkalinity, the Pb mobility is dominated by the movement of Pb-bearing particles, as opposed to chemical transport in solution.

Jan 1, 1994

By R. Hogg

Experimental studies of the axial distribution of particles along dry ball mills are described. The results, for mills ranging in diameter from about 10 cm to 1 meter and operated in both the batch and continuous modes, indicate a consistent pattern of significant migration of particles away from the ends of the mill. In some, but less frequent, cases axial migration of the grinding media is also observed. Analysis of the data suggests that particle migration results from end-effects which extend for a distance of about one mill diameter along its length. End-wall roughness appears to play a significant role in the particle migration phenomenon. Media migration is generally associated with continuous mills operating at relatively high powder flow rates.

Jan 1, 1994

By Jack M. Jodrey, Neil D. O’Donnell, R. A. Metz

Bituminous sands of the Lower Cretaceous McMurray Formation in northern Alberta constitute the ore for the surface mining operation at Syncrude Canada Ltd. These sediments represent a complex succession of fluvial, estuarine and marine depositional environments. Grade prediction is realized through a combination of geological interpretation, computer modeling, and reference to past mining experience. Accurate forecasts of feed grade permit reliable predictions of volumes for removal to meet budgeted synthetic crude oil production. This planning facilitates efficient allocation of mining equipment and resources. The feed grade to the Extraction Plant is monitored at various points along the delivery system.

Jan 1, 1992

By Kexin Cai, Isidro Rivera, Shawna Von Stockhausen, Maria Chastka, Kevin Huynh

The Newell Creek Dam Inlet/Outlet Replacement Project is located approximately 11 miles north of Santa Cruz, California along Highway 9 in the San Lorenzo Valley. This project will replace the existing inlet/outlet works at the Loch Lomond Reservoir by constructing a tunnel using conventional excavation methods while simultaneously drilling three intake shafts to intercept the tunnel from within the city’s water supply. This project will improve the system’s overall operational efficiency and performance, and provide a safe and reliable facility for the City of Santa Cruz’s drinking water supply. This paper discusses the overall project configuration, construction observations, and challenges during construction, including tunnel excavating through the marine sedimentary siltstone of the Monterey Formation, probing and pre-excavation grouting, and the tools utilized to manage the project.

Dec 1, 2022

By Simon Strong, Tim Brown, Luis Ignacio Sanz Vivanco

"One of the most significant technical and practical challenges facing the tunnel construction team on the Legacy Way road tunnel project in Brisbane, Australia was how to erect the pre-stressed precast concrete slabs to form the smoke duct in the tunnel boring machine (TBM) tunnels. An essential part of the tunnel ventilation system, the smoke duct, extends the full length of the 4.6km long twin, two lane tunnels. The vast majority of the tunnels (approx. 4.3km) were constructed using two 12.4m diameter double shield TBMs. The refurbished Herrenknecht machines broke several world records on the way to completing the tunnel excavation works in just over nine months. With the excavation complete the focus turned to solving the complex civil tunnel fit out challenges. A key component of the civil fit out of the tunnels was constructing the smoke duct in the TBM tunnels which was designed as a precast solution. The slabs which each measure 8.62m long by 2.0m wide by 200mm thick and weigh close to 9 tonne need to be erected above cast in situ corbels whilst other tunnel finishing works continue. The space proofing clearance offered by the design to the support corbels below and the precast segmental lining above was in the order of only 100mm. This paper details the events of how the Transcity JV tunnel fit out team, comprising some of Europe and Australia’s leading tunnel construction specialists, drew upon the global strengths of the existing JV member companies and the global reach of leading TBM manufacturer Herrenknecht to develop an innovative system to solve this challenging problem. This globetrotting story, which starts in Australia, visits Europe and mainland China before returning to Brisbane where it all began."

Jan 1, 2016

By Gunjan R. Bhattarai, Kumar Bhattarai

Recently, there has been an enormous increase of interest in artificial intelligence (AI), machine learning (ML), and their applications by researchers, government agencies, and the underground construction industry. Ultimately, these tools have the potential to automate the design and construction processes and boost productivity, safety, quality, and operational stability. This paper presents ongoing research and applications of artificial neural networks (ANNs), robotics, and 3D technologies in ground characterization, tunnel ground support prediction, risk projection and reduction, and productivity enhancement in TBM operations. The paper further investigates potential uses of AI, robotics, and 3D technologies in the underground construction industry

Dec 1, 2022

The latest resource estimate for the Caspiche gold/silver/copper project in the Maricunga region of Chile was released by gold explorer Exeter Resource Corp. The resource is low grade, but bulk minable and drilling to date has shown a NI 43-101 compliant inferred resource of 1,117 Mt (1.23 billion st) grading 0.55 g/t (0.016 oz/st) gold, 3.81 g/t (0.111 oz/st) silver and 0.22 percent copper. Exeter said these findings make the in situ metals amounts of 609 t (19.6 million oz) of gold, 4.4 kt (137 million oz) of silver and 4.84 billion lbs of copper, which the company relates as 33.7 million gold equivalent ounces using assumed metal prices of $23.33/g ($800/oz) for gold, 35 cents/g ($12/oz) for silver and $2/lb for copper. The deposit is almost midway between Barrick?s Cerro Casale gold deposit and Kinross? Refugio Mine. In a statement Exeter chairman Yale Simpson said ?This updated resource estimate places Caspiche firmly among the world?s largest gold-copper discoveries in recent years and clearly supports our decision to aggressively drill the property, despite the global economic decline. ?We expect that the very substantial copper and silver credits will be extremely important, and will markedly impact the potential viability of Caspiche. Specifically, using metal prices of US$2/lb copper, $23.33/g ($800/oz) gold and 35 cents/g ($12/oz) silver, the 4.84 billion lbs of copper and 4.2 kt (137 million oz) of silver are equivalent to 376 kt and 62 t (12.1 and 2 million oz) of gold, respectively. ?Our recent drilling has defined what appears to be a coherent higher grade central zone associated with a definable early stage diorite intrusion. We expect this zone will be important in developing various mining and economic models for the project,? Simpson said. Exeter is still drilling the deposit to expand the re-source estimate further to the southeast and at depth and to upgrade the higher grade central zone to the indicated category. Simpson said, ?Exeter intends to enhance the value of Caspiche by continuing to de-risk the project through ongoing exploration, metallurgy, engineering, water and environmental studies. These studies will continue through the next 12 months and will lead to a conceptual development study. A timeline for the release of that study is being formulated. The project budget for the next 12 months is C$14 million.? Mineweb reported that Caspiche is likely too big of a deposit and at too high of altitude for Exeter to handle alone. Exeter will be looking to other majors, or perhaps the Chinese, to help develop this huge orebody. But, in the meantime, it also has its high grade Cerro Moro deposit in Argentina, which could be brought to production relatively quickly and at relatively low cost.

Jan 1, 2009