Abstract: We consider an underground production scheduling problem which consists of determining the proper time interval(s) in which to complete each mining activity so as to maximize a mine’s discounted value, while adhering to precedence, activity durations, and production and processing limits. We present two different integer programming formulations for modeling this optimization problem. Both formulations possess a resource-constrained project scheduling problem structure. The first formulation uses a fine time discretization and is better suited for tactical mine scheduling applications. The second formulation, which uses a coarser time discretization, is better suited for strategic scheduling applications. We illustrate the strengths and weakness of each formulation with examples. Introduction: Project scheduling is an important aspect of underground mine planning that consists of determining the start dates for a given set of activities so as to maximize the value of a project, while adhering to operational and resourceavailability constraints. Important activities that require scheduling include development, drilling, stoping or other ore-extraction techniques, and backfilling. Precedence relationships impose an order in which activities can be carried out based on their location in the mine. For example, ``the activity a associated with development of an area must be completed before the activity a’ associated with extraction of that same area can begin.” Resources include attributes of the mining operation such as the amount of extraction and mill capacity available per time period, and are determined by capital and equipment availability, among other factors. Correspondingly, for our setting, resource-availability constraints consider the amount of material that can be extracted and sent to the mill (i.e., processed) per time period. We define the Underground Mine Project Scheduling Problem, or UG-PSP, as that of scheduling a set of mining activities in such a way as to maximize the net present value of the project, while adhering to precedence and resource-availability constraints; in general, optimization models for underground scheduling are more complex than their open pit counterparts (O'Sullivan, Brickey, and Newman, 2015). The UG-PSP is a particular case of the Resource-Constrained Project Scheduling Problem (RCPSP), a class of optimization problems known for their difficulty (Artigues et al., 2008). It should be noted, however, that the UG-PSP may have a multitude of feasible solutions. Many mine planning software packages typically rely on heuristics. In this article, we are concerned with using mixed-integer programming to determine a provably optimal schedule, i.e. the schedule with the highest net present value. Trout (1995) first proposed a mixed-integer program to solve a 55-stope UG-PSP over a two-year time horizon using multiple time fidelities. The detailed formulation did not gain widespread adoption due to slow solution times. Little et al. (2013) demonstrate the value of implementing scheduling optimization in the mine design process. Others have created case-specific formulations for a variety of underground mines (Carlyle and Eaves, 2001; Nehring et al., 2010; Martinez and Newman, 2011; Epstein et al., 2012). Newman and Kuchta (2007) provide a model for scheduling the Kiruna mine in which activity duration spans multiple time periods; see also Sarin and West-Hansen (2005), O'Sullivan and Newman (2014), and Brickey (2015) for similar models applied to different mines. Little et al. (2011) outline several aggregation techniques to reduce the number of variables a UG-PSP problem containts, while Salama et al. (2015) examine how changing the production rate changes the value of the UG-PSP solution. UG-PSP Formulations: We begin by introducing notation for our integer programming (IP) formulations of the UG-PSP, and by noting our assumptions. Our formulations are streamlined, generalized, and highly versatile. That is, they contain precedence and resource constraints, which can be tailored to a specific application, and which are the primary two types of

Abstract: Atmospheric monitoring systems (AMS) have been widely used in underground coal mines in the United States for the detection of fire in the belt entry and the monitoring of other ventilation-related parameters such as airflow velocity and methane concentration in specific mine locations In addition to an AMS being able to detect a mine fire, the AMS data have the potential to provide fire characteristic information such as fire growth - in terms of heat release rate - and exact fire location Such information is critical in making decisions regarding fire-fighting strategies, underground personnel evacuation and optimal escape routes In this study, a methodology was developed to calculate the fire heat release rate using AMS sensor data for carbon monoxide concentration, carbon dioxide concentration and airflow velocity based on the theory of heat and species transfer in ventilation airflow Full-scale mine fire experiments were then conducted in the Pittsburgh Mining Research Division's Safety Research Coal Mine using an AMS with different fire sources Sensor data collected from the experiments were used to calculate the heat release rates of the fires using this methodology The calculated heat release rate was compared with the value determined from the mass loss rate of the combustible material using a digital load cell The experimental results show that the heat release rate of a mine fire can be calculated using AMS sensor data with reasonable accuracy

Abstract: Federal regulations require the installation of refuge alternatives (RAs) in underground coal mines. Mobile RAs have a limited ability to dissipate heat, and heat buildup can lead to a life-threatening condition as the RA internal air temperature and relative humidity increase. The U.S. National Institute for Occupational Safety and Health (NIOSH) performed heat testing on a 10-person tent-type training RA and contracted ThermoAnalytics Inc. to develop a validated thermal simulation model of the tested RA. The model was used to examine the effects of the constant mine strata temperature assumption, initial mine air temperature, initial mine strata surface temperature (MSST), initial mine strata temperature at depth (MSTD) and mine strata thermal behavior on RA internal air temperature using 117 W (400 Btu/h) of sensible heat input per simulated miner. For the studied RA, when the mine strata temperature was treated as a constant, the final predicted RA internal air temperature was 7.1°C (12.8°F) lower than it was when the mine strata thermal behavior was included in the model. A 5.6°C (10.0°F) increase in the initial MSST resulted in a 3.9°C (7.1°F) increase in the final RA internal air temperature, whereas a 5.6°C (10°F) increase in the initial MSTD yielded a 1.4°C (2.5°F) increase in the final RA internal air temperature. The results indicate that mine strata temperature increases and mine strata initial temperatures must be accounted for in the physical testing or thermal simulations of RAs.

Abstract: Float coal dust is produced by various mining methods, carried by ventilating air and deposited on the floor, roof and ribs of mine airways. If deposited, float dust is re-entrained during a methane explosion. Without sufficient inert rock dust quantities, this float coal dust can propagate an explosion throughout mining entries. Consequently, controlling float coal dust is of critical interest to mining operations. Rock dusting, which is the adding of inert material to airway surfaces, is the main control technique currently used by the coal mining industry to reduce the float coal dust explosion hazard. To assist the industry in reducing this hazard, the Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health initiated a project to investigate methods and technologies to reduce float coal dust in underground coal mines through prevention, capture and suppression prior to deposition. Field characterization studies were performed to determine quantitatively the sources, types and amounts of dust produced during various coal mining processes. The operations chosen for study were a continuous miner section, a longwall section and a coal-handling facility. For each of these operations, the primary dust sources were confirmed to be the continuous mining machine, longwall shearer and conveyor belt transfer points, respectively. Respirable and total airborne float dust samples were collected and analyzed for each operation, and the ratio of total airborne float coal dust to respirable dust was calculated. During the continuous mining process, the ratio of total airborne float coal dust to respirable dust ranged from 10.3 to 13.8. The ratios measured on the longwall face were between 18.5 and 21.5. The total airborne float coal dust to respirable dust ratio observed during belt transport ranged between 7.5 and 21.8.

Abstract: Testing of the roof bolter canopy air curtain (CAC) designed by the U.S. National Institute for Occupational Safety and Health (NIOSH) has gone through many iterations, demonstrating successful dust control performance under controlled laboratory conditions. J.H. Fletcher & Co., an original equipment manufacturer of mining equipment, further developed the concept by incorporating it into the design of its roof bolting machines. In the present work, laboratory testing was conducted, showing dust control efficiencies ranging from 17.2 to 24.5 percent. Subsequent computational fluid dynamics (CFD) analysis revealed limitations in the design, and a potential improvement was analyzed and recommended. As a result, a new CAC design is being developed, incorporating the results of the testing and CFD analysis.

Abstract: The Pittsburgh Mining Research Division of the U.S. National Institute for Occupational Safety and Health (NIOSH) conducted underground evaluations in an attempt to quantify respirable rock dust generation when using untreated rock dust and rock dust treated with an anticaking additive. Using personal dust monitors, these evaluations measured respirable rock dust levels arising from a flinger-type application of rock dust on rib and roof surfaces. Rock dust with a majority of the respirable component removed was also applied in NIOSH's Bruceton Experimental Mine using a bantam duster. The respirable dust measurements obtained downwind from both of these tests are presented and discussed. This testing did not measure miners' exposure to respirable coal mine dust under acceptable mining practices, but indicates the need for effective continuous administrative controls to be exercised when rock dusting to minimize the measured amount of rock dust in the sampling device.

Abstract: Introduction Diesel engines have seen widespread use for well over a century due to their relatively high thermal efficiency and fuel economy (Heywood, 1988). Recently, however, the adverse health risks of diesel exhaust have become increasingly clear. The term diesel particulate matter (DPM) is used to refer to the solid components of diesel exhaust, which are an ultrafine mixture of elemental and organic carbon (EC and OC) and minor constituents including sulfates and metal ash (Kittelson, 1997). DPM is generally considered to occur almost entirely in the submicrometer range. It is classified as a carcinogen (Occupational Safety and Health Administration, 2013), and epidemiological studies have demonstrated a positive correlation between long-term exposure to DPM and other combustionrelated fine particulates and increased cardiovascular and pulmonary diseases (Pope et al., 2002; McDonald et al., 2011). Many of the risks of diesel exhaust are associated with the physical and chemical properties of exhaust components (Heywood, 1988; El-Shobokshy, 1994; Kittelson, 1997). Exposures are generally measured and regulated on the basis of mass concentration. However, DPM number density and particle size are increasingly recognized as critical factors in terms of health outcomes (Bugarski et al., 2012; Kittelson, 1997; Occupational Safety and Health Administration, 2013; Pope et al., 2002). Diesel engines operate in relatively fuel-rich/oxygen-lean conditions and are characterized by high emissions of particulates relative to those from spark-ignition engines (El-Shobokshy, 1994; Kittelson, 1997; Fiebig et al., 2014). Emissions from large equipment such as that used in mining applications typically range from 10 to 10 DPM particles per cubic centimeter (Kittelson, 1997). The physical and chemical properties of DPM vary with the type of engine, fuel and operating conditions such as loading, which is a function of torque and rotational speed (El-Shobokshy, 1994; Kittelson, 1997; McDonald et al., 2011; Bugarski et al., 2010; Huang et al., 2015). Loading is a particularly important factor with respect to DPM toxicity (McDonald et al., 2011; Stevens et al., 2009; McDonald et al., 2004) and the effectiveness of after-treatment technologies (ElShobokshy, 1994; Kittelson, 1997; An et al., 2012). Engine load alone can affect the EC/OC ratio, and the size distribution and number density of DPM. Light loads generally favor the formation of OC and small particles. As load is increased, the volatiles are oxidized, leading to larger soot particles (EC) but lower total number density of DPM. With further loading, the formation of soot offsets the decrease in volatiles, resulting in increased DPM mean size and number density (Kittelson, 1997). A significant body of work has been devoted to the development of DPMreducing technologies, including aftertreatments like oxidation catalysis and Laboratory demonstration of DPM mass removal from an exhaust stream by fog drops

Abstract: Personal respirable dust sampling and the evaluation of control technologies have been providing exposure information to the mining industry but not necessarily in a way that shows how technology can be integrated to provide organizational support and resources for workers to mitigate dust sources on site. In response, the U.S. National Institute for Occupational Safety and Health (NIOSH) used previously developed Helmet-CAM technology to design and engage in a behavioral/engineering cooperative intervention to initiate and enhance mine site conversations about the risks and potential occurrences of respirable silica dust exposures on the job as well as provide impetus and solutions for mitigating higher sources of dust. The study involved 48 workers from five mine sites, who agreed to participate between April 2015 and September 2016. Using the Helmet-CAM in this series of longitudinal interventions revealed several exposure trends in respirable silica dust sources and, in many cases, simple quick-fix strategies to reduce their sources. This paper focuses on several specific identified sources of dust that were elevated but could be reduced through basic engineering fixes, low-cost resources, and supportive communication from management to remind and engage workers in protective work practices.

Abstract: The results of laboratory evaluations were used to compare the potential of two alternative, biomass-derived fuels as a control strategy to reduce the exposure of underground miners to aerosols and gases emitted by diesel-powered equipment. The effects of fatty acid methyl ester (FAME) biodiesel and hydrotreated vegetable oil renewable diesel (HVORD) on criteria aerosol and gaseous emissions from an older-technology, naturally aspirated, mechanically controlled engine equipped with a diesel oxidation catalytic converter were compared with those of widely used petroleum-derived, ultralow-sulfur diesels (ULSDs). The emissions were characterized for four selected steady-state conditions. When fueled with FAME biodiesel and HVORD, the engine emitted less aerosols by total particulate mass, total carbon mass, elemental carbon mass and total number than when it was fueled with ULSDs. Compared with ULSDs, FAME biodiesel and HVORD produced aerosols that were characterized by single modal distributions, smaller count median diameters, and lower total and peak concentrations. For the majority of test cases, FAME biodiesel and HVORD favorably affected nitric oxide (NO) and adversely affected nitrogen dioxide (NO2) generation. Therefore, the use of these alternative fuels appears to be a viable tool for the underground mining industry to address the issues related to emissions from diesel engines, and to transition toward more universal solutions provided by advanced engines with integrated exhaust after treatment technologies.