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By M. A. Reyes, L. Yan

"Heat and humidity buildup within refuge alternatives (RAs) may expose occupants to physiological hazards such as heat stress. Mine Safety and Health Administration (MSHA) regulations require RAs in underground coal mines to provide a life-sustaining environment for miners trapped underground when escape is impossible. RAs are required to sustain life for 96 hours while maintaining an apparent temperature (AT) below 95°F (35°C). NIOSH tested a 10-person tent-type RA, a 23-person tent-type RA, and a 6-person metal-type RA in NIOSH underground coal mine facilities to investigate the thermal environment over a 96-hour period. The test results showed that mine air and mine strata temperatures surrounding an RA occupied by simulated miners increased over the 96-hour test period. The test results suggest that RA manufacturers should consider this increase in temperatures when calculating and evaluating RA components during surface and laboratory tests. The findings can equip stakeholders with additional considerations for calculating heat and humidity temperature profiles for RAs not tested in situ. INTRODUCTION RAs are designed to provide a life-sustaining environment for miners who cannot escape after a mine disaster. One of the major considerations for integrating RAs in mine environments is the thermal environment inside the RA and the impact that the surrounding mine conditions have on the temperature and humidity buildup. Previous research has observed that the metabolic heat of the occupants and the heat released by the CO2 scrubbing systems will cause the RA interior air temperature to increase. In addition to the increase in temperature, an occupant’s respiration and perspiration, as well as the chemical reaction of the scrubbing chemicals with CO2, will contribute to an increase in humidity within the RA. The resulting internal thermal conditions, if not controlled, can subject miners to conditions that can lead to heat exhaustion, heat stroke, or even death depending on the duration and magnitude of exposure. Apparent temperature (AT) is a temperature-humidity metric for the perceived temperature caused by the combined effects of air temperature, relative humidity (RH), and wind speed. It is used to assess the perception of indoor temperatures when workplaces are not sufficiently heated, cooled, or insulated to provide comfortable or healthy conditions. Mine Safety and Health Administration (MSHA) regulations require that RAs must be designed to ensure that the internal AT does not exceed 95°F (35°C) when the RA is fully occupied."

Jan 1, 2018

By Christopher Newman, David Newman

The ability to assess, address, and predict mining-induced stress distribution is paramount in maintaining a safe and efficient underground operation as coal mines continue to develop at deeper depths and in more geologically complex reserves. This is especially true for longwall mining operations given their limited flexibility in panel layout and orientation. This paper focuses on ground behaviors and conditions observed at two deep-cover, steeply dipping longwall mining operations in Utah’s Unita coal basin. This region is susceptible to coal pillar bump/bounce events as a result of high depth of cover, high-extraction mining, and the close proximity of a thick massive stiff sandstone stratum to active mineworks. The successful prediction of mining-induced coal bump events for Mine A and Mine B operating in the Unita basin has prompted mine management to develop a rock mechanics testing database for reserve calculations. The database is applicable to mine planning as well as the development of multiple numerical models to proactively identify and address adverse ground conditions using input parameters calibrated to site-specific behaviors and conditions. For both Mine A and Mine B, the most critical question relates to longwall development and recovery for “extreme” deep-cover longwall panels at overburden depths greater than 600 m. This paper highlights the impact of high-stress concentrations associated with deep-cover longwall mining as well as the methods applied to mitigate stress impacts on miner safety and longwall production.

Jul 1, 2023

By Kevin Andrews, SETAREH GHAYCHI AFROUZ

Ground control analysis and groundwater inflow assessments for underground coal mines require in-depth field investigations including, but not limited to, geological and geotechnical core logging, downhole geophysical logging, laboratory rock strength testing, and packer (Lugeon) testing. Field and laboratory data collection are time consuming and expensive, and an initial understanding of the expected trends among various geotechnical and hydrogeological parameters can assist with the planning and optimization of geotechnical characterization studies and grouting plans. In this study, a comprehensive database is analyzed, comprised of important rock mass characteristics (hydraulic conductivity, rock quality designation (RQD), and lithology) for coal-bearing rocks in the Central Appalachian Basin. Statistical analysis of the data is completed to establish an enhanced understanding of geotechnical and hydrogeological conditions expected to be encountered as underground coal mining passes near and beneath streams and rivers. The results of the study provide valuable reference material for the coal mining industry for completion of shaft installations, mine stream crossings, environmental assessments, and grouting and mine dewatering designs.

Jul 1, 2023

By J. K. Ross, K. O. Hoal, S. K. Appleby

Understanding ore variability is a key factor in the geometallurgical analysis of a deposit and is beneficial to process development and mine planning. Ore variability is a function of the mineralogy of a deposit, in terms of both ore and gangue minerals and their textural relationships. This study integrates optical microscopy and quantitative mineral analysis to characterize the mineralogy and texture from 13 samples from different lithologic units at the Bingham Canyon Mine. The analysis identified several parameters, such as modal mineralogy, alteration assemblages, distribution of mineral phases and alteration assemblages and microfracture and void space distribution. These parameters can have an impact on the materials’ behavior during processing. This study demonstrates that quantitative mineralogical analysis can provide detailed information for improved understanding of ore variability.

Jan 1, 2010

A charge of the Research Council of the Society for Mining, Metallurgy and Exploration, Inc. (SME) is to ?? identify longer term research ideas/needs, that in the perception of the SME Research Council, could represent significant technology breakthroughs ?? (SME, n.d.). In 2008, the Council decided that instead of unilaterally developing a list of top priorities, it would involve the entire membership of SME in identifying the top priorities. Additionally, it decided to keep the list short. This paper describes the process and results from that exercise.

Jan 1, 2010

By Peter Zhang, Daniel Su, Mark Alexander Van Dyke, Heather Dougherty, Bo Hyun Kim

The National Institute for Occupational Safety and Health (NIOSH) has been evaluating longwall mining-induced strata fractures and their impacts on casing stability of Marcellus shale gas wells located in longwall pillars. To understand the extent of overburden fractures after longwall mining, NIOSH researchers drilled a post-mining corehole into the fractured strata above the Pittsburgh coal seam longwall gob. Knowing the extent of the fracture zone height will help gas operators minimize the hazards of drilling into longwall gobs. The core was retrieved from the surface down to the top of the gob void. Various fractures were encountered varying from 35 to 64°, depending on lithologic type and relative closeness to the gob. The longwall panel dimension was 457-m wide and 3657-m long, in which the total fracture zone height was found to be at 141 m and the hydraulic connected fracture zone at 87.7 m above the top of the Pittsburgh seam. In addition to core drilling through the gob, FLAC3D modeling was also used to simulate the formation of fracture zone and the orientations of longwall-induced fractures. This study provides much-needed evidence on the fracture zone of Pittsburgh seam longwall gobs to help gas operators avoid potential hazards associated with drilling through highly fractured zones in longwall gobs.

Jun 9, 2022

By Justin R. Patts, Andrew B. Cecala, A. KYLE LOUK, Emily J. Haas

The National Institute for Occupational Safety and Health (NIOSH) and the former U.S. Bureau ofMines (USBM) have given a significant effort over the past four decades in researching and developing engineering controls and interventions to reduce mine workers’ dust exposures during the bagging and palletizing of industrial minerals. Workers performing manual bagging and palletizing of 50- to 100-pound bags typically have some of the highest dust exposures of all workers at mining and mineral processing operations. This paper will provide an overview of available dust control technologies for bagging operations and present the findings of a recent case study that was conducted at four different industrial sand operations to identify the current types of bagging and palletizing technologies being used and to evaluate their effectiveness in reducing workers’ exposures to respirable crystalline silica dust. An evaluation will also be performed to determine if further reductions in respirable dust levels can be achieved by incorporating additional modifications or improvements into the existing technology.

Apr 3, 2020

By Verya Nasri, Kevin Akbarpour, Hiva Mahdavi

"The Sheppard East Light Rail Transit (SELRT) project comprises approximately 13 km of new light rail, which will be constructed along Sheppard Avenue East in Toronto. There is a 380 metre long section of the route that will be constructed as tunnel below Highway 404, which is owned by the Ministry of Transportation Ontario (MTO). MTO has published guidelines for tunneling under its highways. An impact analysis was undertaken to predict the surface settlement and angular distortion of Highway 404 resulting from the construction of the twin tunnels. The results were then compared to the performance criteria defined in MTO’s guidelines. As a result of this analysis, it was necessary to request an adjustment to MTO’s current performance criteria. This paper presents details and results of the impact assessment, approaches taken to satisfy the requirements defined by MTO, and provides details of the adjustment permitted by MTO. INTRODUCTION Several major rapid transit projects are planned for the Greater Toronto and Hamilton Area (GTHA) located in southern Ontario, Canada. These projects are part of The Big Move (Metrolinx 2008) initiative, a 25-year, and $50 billion plan aimed at improving regional transportation. Metrolinx, an agency of the Government of Ontario, is now working collaboratively across the region to deliver major Toronto rapid transit projects to the GTHA. One such project is the SELRT. The line will largely run along Sheppard Avenue East on the surface, except for a crossing of Highway 404 where it will be constructed using a combination of open cut and bored tunneling methods. AECOM has been retained by Metrolinx as the Technical Advisor (TA) to develop the Reference Conceptual Design (RCD) and Project Specific Output Specifications (PSOS) for the project. Also, Infrastructure Ontario (IO) is the Co-Sponsor and CH2M HILL is Metrolinx’s Owner’s Engineer (OE) & Project Management Support (PMS) for the new LRT lines. This paper presents information on the tunneling settlement analysis and further work undertaken to satisfy the MTO’s requirements."

Jan 1, 2016

By TOMI GIORGIO DE, Ricardo Tichauer

Mineral exploration is a key factor for success in the mining industry. However, exploration best practices are often ignored in small-scale mining. This works presents the Tichauer-DeTomi Matrix, a methodology that measures the level of compliance of exploration programs in small-scale mining with the industry best practices. The matrix has been applied to three projects in Brazil: an artisanal gold mine in the state of Pará, a small-scale manganese project in the state of Bahia, and a small-scale manganese project in the state of São Paulo. The application of the matrix resulted in indexes that represent the level of maturity of the exploration program in each project and indicate priority actions for reduction of the geological uncertainty. Therefore, the Tichauer-DeTomi Matrix has shown potential to be a useful tool for assessment of geological uncertainty in small-scale mining. As a risk indicator, it may contribute to promoting investment in small-scale mining and development for communities that depend on this activity around the world.

By P. Asadollahi, M. Invernizzi

"This paper describes the innovative full-face conventional tunnel excavation technology, with its advantages in terms of savings and safety. The full-face approach has been developed throughout the experiences gained in tunnel construction. The innovative design approach is focused primarily on the deformation response of the ground acting first and foremost ahead of the face, which is analyzed, predicted and controlled by pre-confinement of the core. The advantage of this method is particularly evident in difficult grounds. This paper will present the outstanding benefits given by the adoption of the full-face approach in two projects, the “Sochi” and the “Visnove” tunnels. THEORY AND DESIGN ASPECTS OF THE FULL-FACE EXCAVATION The main challenges in tunnel and underground construction industry are gathering the design data from the ground that is being excavated and foreseeing the critical stage during construction, where the materials are in its most critical configuration. These challenges shall be addressed during excavation when the lining and the excavation disturbance have not yet reach the equilibrium. The in situ stresses in the ground are redistributed (forming an “arch-effect”) around the opening, with zones of increased stresses around the walls of the excavation (Figure 1). The distribution of the stresses can be close or far from the excavation profile, depending upon having a ground capable of withstanding the deviated stresses well or unable to withstand them, respectively. In the latter case, the ground will plasticize and deform in proportion to the volume of ground involved in the plasticization phenomenon. When the ground completely cannot withstand the stresses redistribution, it will cause the collapse of the excavation. While in the first case, the arch effect occurs naturally, in the second case, it does occur naturally only when the ground is stabilized properly. In the case of collapse, the arch-effect must be produced artificially operating on the ground prior excavation. The design should be based on the understanding of if and how the arch-effect can be mobilized during tunnel excavation and ensure that is formed by calibrating excavation and stabilization operations appropriately. The arch-effect is function of the medium that is being excavated, the action taken to excavate and the reaction expected following the excavation."

Jan 1, 2018

By Stryker Magnuson

While probe drills are not strictly necessary for all projects, the incorporation and use of probe drills and pre-grouting adds capability and insurance to boring operations. Water ingress and unstable ground can be resolved before becoming a problem and resulting in costly delays through the use of enhanced, 360-degree probe drilling setups. To do this, proper design of the array of drill ports in the shield, matched to the possible ground conditions, is critical. For ground with exceptional water and instabilities expected, additional probing locations are low-cost additions that can lower risk and increase efficiency. In this paper we will look at recent and ongoing projects including the Lower Meramec Tunnel and Jefferson Barracks Phase 2. We will detail the design of those probe drill arrangements, and our overall recommendations for probing/grouting systems that best suit challenging ground conditions and keep projects running smoothly.

Jun 13, 2023

By M. Rodgers

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

Jan 1, 2010

By L. Rudolphy, P. Tähkiö

"The cPlant is a modular flotation plant which has been designed to minimize capital expenditure and risk. The plant is based on a number of standard modules, for both flotation and ancillary equipment, which can be configured to give the required flowsheet for the ore being treated. All of these modules can be rapidly deployed and erected onsite, minimizing not only engineering time and site preparation but reducing the time taken to get the plant up and generating revenue. Given the paradigm shift in flotation circuit design that has been employed in the cPlant it may allow smaller, previously uneconomic deposits to be exploited and create a more cost efficient upgrade route for existing plants. This paper introduces the cPlant and presents a case study comparing EPC cost and development timing of a cPlant against a traditional flotation circuit design. INTRODUCTION In the development of any mining project the cost associated with process plant engineering, equipment procurement and installation can affect the financial viability of a project. This is of special significance for smaller scale mining projects which perhaps don’t have the mine-life or revenue generation to justify the payback on a modern processing facility. Listening to customer feedback and understanding the challenges that small to mid-sized projects can face lead Outotec to the development of the cPlant. Modularization of mineral processing plants isn’t a new idea with a number of examples being reported in literature for gravity gold (Cabot, Trudel and Cabot, 2001; Gray et al., 2006), dense medium separation (September and Abate, 2006) and even hydrometallurgy (Saario et al., 2013). All these plants have been developed to try to improve on the traditional economics associated with fixed processing plants. Using standardized modules to construct a plant reduces engineering time and design costs which can both be beneficial to the outcome of a project. In addition the modular nature of the plant lends itself to transport to remote sites and rapid installation with only minimal site preparation required. A plant of modular design also has several other advantages over its conventional cousins. Firstly it is relatively easy to expand by duplicating existing modules. Secondly the modules can be treated as building blocks for the process and rearranged if a change in conditions requires flowsheet adjustment. Thirdly, there is potential to disassemble and remove the modular units at the end of the mine life. The ability to easily disassemble, re-pack and transport the plant to a new location not only is important to the long term environmental footprint of an operation but can also be seen as a bonus to an operator that has a number of small ore deposits. If applied in this way modular plants have the potential to create a whole new operating model for previously unviable ore deposits."

Jan 1, 2016

By Bo Kyung Sim, Dae Young Kim, Jae Won Lee, Ebrahim Farrokh

"The contract C931 of the downtown line 3 (DTL3) mass rapid transit system of Singapore includes half a kilometer twin tunnels running between Mattar and Macpherson stations. An EPB TBM of 6.6 m diameter was used to excavate both of these tunnels. The tunnels pass predominantly through a very stiff silty/clayey fine to coarse sand from the Old Alluvium Formation. In this paper, TBM selection procedure, TBM performance evaluation, and some of the tunneling operation challenges with the TBM in the Old Alluvium Formation are discussed. In this regard, soil conditioning trial tests were performed to resolve the clogging issue and low TBM performance. Thorough TBM operational data analysis was performed to detect high soil abrasivity, backfill grout leakage, and foam nozzle clogging. The results of some of the applied modifications are also discussed to show their effects on the TBM performance improvement. Finally, some of the challenging TBM design specifications are also discussed. INTRODUCTION Tunneling and underground construction in Singapore has been increased in the last 30 years due to the demand for public transportation systems and the limited space above the ground for the infrastructure development. Downtown Line Stage 3 (DTL3) Mass Rapid Transit (MRT) system has 21 km total route length and consists of 16 stations. DTL3 Contract C931 runs between Mattar station and MacPherson station. The construction works in this contract include twin bored tunnels of 6.6 m diameter and 450 m length and a TBM launch shaft of nearly 30 m depth. The tunnels run in urban area below Kallang Paya Lebar Expressway tunnel (KPE), Kallang River Canal, and Circuit Link. Figure 1 shows the alignment of the tunnels in between two subway stations. The tunnels were excavated by an earth pressure balance (EPB) tunnel boring machine (TBM) through the Old Alluvium (OA) formation, a challenging geological formation in the sense of its abrasivity and stiffness. The Old Alluvium Formation mostly includes stiff to very stiff clayey and silty sand. The soil is un-weathered cemented to semi-cemented dense, mainly with a low permeability coefficient of 10-7 m/s and high SPT values (almost 100). The soil is classified as “very high abrasive” according to NTNU SAT test classification (SAT value of 15 to 42). The construction of the first tunnel drive was slowed down due to a number of factors related to soil conditioning and TBM operation. In this regard, a thorough analysis of the TBM operational parameters from the excavated sections was performed to identify the problems in time to prevent unwanted construction delays in the subsequent sections. In the following sections, a brief overview of the criteria used for TBM selection is presented at first. Then, the results from the analyses and tests performed to assess soil conditioning, grout leakage, and soil abrasion are presented. The last section discusses some of the tunneling design features that challenged the TBM operation in this project."

Jan 1, 2016

By D. Murray

"The Mine Improvement and New Emergency Response (MINER) Act included the need for improved chemical technologies to address respiratory protective device inadequacies and refuge alternative development. The National Institute for Occupational Safety and Health’s (NIOSH) National Personal Protective Technology Laboratory (NPPTL) invests in research and development to improve the carbon dioxide (CO2) scrubbing technologies built into these mine safety systems. Testing at NIOSH NPPTL is performed using a custom-designed test system containing a chemical reactor and sensors in a constant flow of simulated expired breath to evaluate chemical performance for the scrubber materials. Current testing procedures focus on device duration or capacity, but do not report criteria needed to effectively optimize chemical performance. In this presentation, testing results which identify the chemical performance roles for CO2 scrubber components will be reported, and specific component chemical activities will be linked to both duration and CO2 absorption capacities. Chemical components being evaluated include hydroxyl, superoxides, metal, and amine active sites, distributed in salts, zeolites, metal-organic frameworks, and microporous materials. INTRODUCTION CO2 absorbents and oxygen sources are at the heart of closed circuit breathing air supply systems used in mining escape and rescue operations. CO2 absorbent technology was first developed for diving rebreathers and has been in use for over a century. Typically these devices include a soda lime formulation of pellets in the 8-12 mesh range. Larger 4-8 mesh particles are used in medical grade “low-flow” applications, since these particles present a lower flow resistance regime more amenable for use with resting individuals. Potassium superoxide and lithium hydroxide formulations are also used, where in each case the formulations involve bulk solid pellets or materials affixed to surfaces. CO2 capture technologies are now under intensive study in the energy and automotive industries, where the pursuit of optimal combustion processes has led to the development of new materials to capture, convert and store CO2, oxygen and carbon monoxide gases. Recent advances in nano-structured and high surface area catalysis have produced novel materials demonstrating chemical performance improvements in these industries, and these improvements may now also be adapted to enhance chemical efficiency and performance in escape and rescue devices. Higher surface area materials offer promise for improving the efficiency, or decreasing the burdens associated with the use of closed circuit respiratory protective devices containing CO2 absorbents. Novel chemicals that display advantages in chemical performance or decreased burden will be examined for inclusion in developing systems such as the next-generation closed-circuit mining escape respirator or refuge alternatives."

Jan 1, 2018

By C Rutter, N Shea, K Kolobe

The Henderson mine, a panel cave mine in Colorado, has undergone multiple ventilation system changes to meet dynamic airflow needs. This paper explains the ventilation designs for different production panels, the challenges faced, and the modifications made to optimize the ventilation systems. The study highlights the importance of a robust ventilation system for safe and productive mining.

Mar 2, 2022

By Lindsey Schneider, Steve Kirk, Michael Miglioretti, Jeffrey P. Kolzow, Kyle White

The US17 Spring/Fishburne Drainage Improvements Project utilizes a stormwater conveyance tunnel system of approximately 8,250 LF. The tunnel system includes two intersecting tunnels of differing diameter at a 40-degree angle. The intersection was constructed in soft-ground conditions. This paper discusses the design, geotechnical concerns, initial ground support, and final lining construction. The tunnels utilized two soft-ground TBMs excavated at 15 ft and 11 ft with ribs & lagging initial support. The final lining consisted of unreinforced and reinforced cast-in-place concrete with polymer fibers. Concrete final lining was successfully completed in March 2020.

Jun 13, 2021

By J. Frostiak

The Campbell gold operation of Placer Dome Inc. produces an arsenopyrite-sulphide concentrate which must be treated either by roasting, biooxidation or by pressure oxidation to obtain high gold recoveries. Pressure oxidation is a proven process and has the inherent advantage of meeting the stringent environmental regulations in the province of Ontario. A comparison of biooxidation and pressure oxidation was completed early in 1990 and the latter was selected by Placer Dome as the preferred process for replacement of the roasters. The commercial plant design was based on technology supplied by Sherritt Gordon and in July of 1991, the existing roaster operation was shut down and a new pressure oxidation plant was commissioned. The following summary describes the start up of the new facility and presents typical operating data.

Jan 1, 1992

By Valerio Violo, Antonio Raschillà, Livia Cicinelli

"The Cityringen project foresees the construction of a new circular metro line in and around the city center of Copenhagen. Both drives, the north and the south one, required the TBMs to be equipped in order to cope with contaminated water table and soil. The north drive mined in water contaminated with chlorinated compounds, including chloroform and vinyl chloride, while the south TBMs excavated in a highly benzene contaminated area, becoming the first TBMs to complete such a challenge. Despite the pollution and the stricter operative procedures, the production has been extremely successful with record up to 520 m in one month and 32 m in one day. 1 INTRODUCTION The Cityringen is an extension of the existing metro line. The 15 km long twin tunnels will form a new circular line with 21 new stations (17 + 4 crossovers). When finished it will interchange with the existing metro, rail and bus infrastructure at key locations around town, taking 90% of Copenhagen citizen at less the 600m from a metro station (Figure 1). The Contract has been awarded in April 2011 to the Copenhagen Metro Team (CMT), a joint venture between the Italian companies Salini Impregilo, Tecnimont and Seli SpA. Tunnels are being excavated with 4 Seli-Kawasaki EPB TBMs, two of which manufactured in Denmark by Seli Tunneling Denmark ApS, which is also operating them. At the moment this article is written 50% of the tunnels have been completed and over 40% handed over for the electromechanical works. Seli Tunnelling Denmark is a Danish company constituted in 2012 as a subsidiary of Seli SpA for this project and subsequently acquired by the Salini Impregilo Group in 2015."

Jan 1, 2016

By Ren Bryce

The ninth annual Mineral & Metallurgical Processing Division (MPD) student poster contest was held in February at the SME Annual Conference & Expo in Minneapolis, MN. A total of 33 students presented their work at the contest. The competition began in January when the students submitted a one-page abstract for judging. In February, they prepared and presented a poster that explained their research. A panel of judges went to each student and listened as the students explained their research in five minutes. The students worked hard at their research and then set aside time to complete all the necessary steps to enter the contest. The MPD recognizes the effort required to enter and, as a result, provides monetary rewards to all participants. As in past years, there are separate levels of competition for undergraduates and graduates, and the prizes are designated accordingly. At the graduate level, first place receives $1,000, second place $500, third through seventh $200 each, and all others $125 each. At the undergraduate level, first place receives $1,000, second place $500, third place $250, and all others $125 each.