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By L. Yuan, J. H. Rowland III

"In 1995 and 2003, the Mine Safety Health Administration (MSHA) conducted surveys to determine the number of atmospheric monitoring systems (AMS) being used in underground coal mines in the United States. The survey reports showed data for the different AMS manufacturers, the different types of equipment monitored, and the different type of gas sensors and their locations. Since the last survey in 2003, MSHA has changed the regulation requirements for early fire detection along the belt haulage entries. As of December 31, 2009, point-type heat sensors were prohibited for use for an early fire detection system; instead carbon monoxide (CO) sensors are now required. This report will examine the number of AMS currently used in underground mines in the United States to see if there is a change in their use. The locations and parameters monitored by AMS are also discussed. INTRODUCTION The last survey conducted by the Mine Safety and Health Administration (MSHA) on atmospheric monitoring systems (AMS) used in underground coal mines in the United States (US) was in 2003 [1]. The survey report states that since 1995 there had been a steady increase in the use of AMS in underground coal mines as the technology of CO sensors was improved by manufacturers. AMS had become more reliable and some CO sensors could be purchased with the capability to discriminate between the CO produced from a fire versus CO produced from diesel equipment. This increase in reliability had reduced the number of false alarms and the response time. The faster response time to a developing fire allowed for the miners to take the necessary action to put out the fire or exit the mine. It should also be noted that at the time of last MSHA survey, some mines still used point-type heat sensors to detect the presence of a fire on conveyor belts. This detection method works by measuring the temperature of the air around the sensor. As a fire starts to develop, smoke and hot gases are produced from the combustion process, and the air is heated up. Once the air and gases reach a designated temperature detected by the point-type heat sensor, a fire alarm signal is generated. Studies have shown that the response times for detecting the presence of a fire using CO sensors are much shorter than using point-type heat sensors [2]. Finally, since the last MSHA survey, regulations have changed on the type of automatic fire detection systems permitted to be used in conveyor belt entries. As of December 31, 2009, point-type heat sensors are not permitted to be used for fire detection in underground coal mines in the US; instead CO sensors are required as a replacement (30 CFR 75.1103-4). This study will examine how the changing of the above regulations has impacted the use of CO sensors in underground coal mines in the US compared to their use based on the last MSHA survey. Importantly, in the previous MSHA survey, the data was recorded for producing and non-producing coal mines. In this study, only the data from the producing coal mines was recorded. Data was collected from a total of 235 coal mines for this study with the help of the MSHA district offices."

Jan 1, 2017

By Kim McKnight

Dupont has successfully incorporated a Floatex Density Separator into its wet-gravity operations for the recovery of zircon from titanium tailings. Results indicate that the Floatex achieved a zircon recovery of approximately 95% while rejecting similar amounts of quartz and other gangue minerals. Additionally, a unit capacity approaching 16 tonnes/hr/m2 was achieved. Results also show that the alumino-silicates can be separated into other product streams that will further improve process economics and minimize waste material. The improved plant feed grade provided by the Floatex has allowed for either an increase in overall plant capacity and/or final product grade. This paper will present the findings from the in-plant study.

Jan 1, 1996

By Saverio Agresti, Giuseppe Lunardi, Donato Basta, Roberto Trapasso

"At a distance of 10 years from the first application of the Nazzano Method, the widening under traffic of a tube of an existing motorway tunnel was realized near Ancona, along the A14 Motorway in Italy. This paper describes the works for the enlargement with conventional method of the second tube, very close to that already widened under traffic.This enlargement was realized very fast, taking into account the advantages of some interesting technological improvements of the Final Design proved in the first tube.INTRODUCTION TO THE WIDENING OF EXISTING MOTORWAY TUNNELSThe widening of a twin-bore motorway tunnel usually considers the double option of creating a third bore as an alternative or closure to traffic of one of the two bores with the resulting reduction in the level of service for users.On the contrary, the extension in situ of a road, motorway, railway or underground tunnel in the presence of traffic, made possible by an inspired idea of Prof. Pietro Lunardi, enables the level of service of the infrastructure to be maintained without the need to resort to alternative routes to create new permanent or temporary bores, not always feasible because of the lack of the necessary space.This construction technique, known as the ‘Nazzano Method’, is part of the technologies refined and offered by the ADECO-RS approach to tunnel design and construction (Lunardi P., 2008) which is increasingly used in the world, leading to the industrialisation of tunnelling (meaning respect for the times and costs set out during detailed design) both in conventional and mechanised (through TBM) excavations.The first true experimentation of the ‘Nazzano Method’ was carried out between 2004 and 2007 to enlarge the two-bore ‘Nazzano’ tunnel (Italy, Milan-Rome A1 motorway) in the presence of traffic, widening it to house from two to four lanes in each direction (Lunardi P. et al., 2007). Following the success achieved in this first application, the Nazzano Method was strengthened considering all the possible suggestions arising from the previous experience and then taken up to enlarge the north bore of the ‘Montedomini’ two-bore tunnel (Italy, Bologna-Taranto A14 motorway), in situ and the presence of traffic."

Jan 1, 2016

By L. F. Delgado

Environmental and cost pressures sparked renewed interest in gravity separation. Industrial sands in Mexico are generally processed by screening, desliming, and flotation. Gravity separation with spirals was evaluated as an alternative to flotation in order to lower operating costs and decrease water pollution. Outstanding operating results are obtained in glass and foundry sand operations, plus a more competitive position for Mexican producers due to lower operating costs. Coal fines, generally recovered by flotation, have the same cost and environmental advantages when processed with spirals.

Jan 1, 1994

By M. G. Gorman

The effects of particle size, particle shape and degree of aggregation on n-dodecylamine flotation of -20 µ m quartz and glass beads were studied. A microflotation cell suitable for use with very fine particles was used in the flotation experimentation. Degree of agglomeration of particles was estimated by comparing size distributions of the quartz and beads in a dispersed system to size distributions in systems in which the collector was present. Results obtained show that in such flotation systems the fine particles are not generally present as individual particles during flotation but rather as aggregations. However, the quartz floats more readily than the beads indicating that there are some shape effects in the systems, considering the large specific surface areas of the materials it also appears that substantial amine consumption in the systems may limit flotation or lead to a requirement of greater reagent dosage for equivalent flotation to that tor larger particles.

Jan 1, 1990

By S. A. Moffatt

For several years iron ore processing plants, located in the northern U.S. experienced seasonal decreases in the grinding efficiency of their primary autogenous mills. Kawatra and Eisele (1992) studied this phenomenon in an operating plant and characterized it in terms of specific energy consumption (Fig. 1) and production of critical size material (Fig. 2). Critical size material is defined as ore that is too small to be effective grinding media and too large to be ground. This data showed that both specific energy consumption and critical size production increased during the winter months. The increased energy consumption was in part a result of an increase in the viscosity of the mill pulp at colder pulp temperatures. However, viscosity could not fully explain the changes in critical size production. These changes are most likely due to changes in the breakage characteristics of the ore. Other studies were also conducted to determine if thermal and physical properties of iron ore changed at colder temperatures. These are summarized below:

Jan 1, 1993

By M. U. Khan

"Underground mine diesel equipment generally offers more flexibility as compared to electric powered systems. Diesel exhaust is an adverse agent which affects the health of underground miners. The National Institute of Occupational Safety and Health (NIOSH) regard diesel exhaust as carcinogenic. The NIOSH 5040 method is an established technique for measuring Diesel Particulate Matter (DPM). This process inherently involve a lag time before an accurate exposure determination can be made during which miners are potentially overexposed to DPM. This issue can be addressed by using realtime DPM monitors. This paper presents underground mine shift average based and realtime monitored DPM values monitored in US mines. A FLIR Airtec instrument has been used for realtime measurement whereas shift average based DPM has been determined by the use of NIOSH 5040 method. A log of diesel equipment movement was kept. DPM concentrations versus time were plotted and analyzed. High DPM sources were identified and the FLIR Airtec was demonstrated to be satisfactory for realtime DPM measurements. INTRODUCTION The use of diesel equipment in mines is an attractive option due to its ability to convert a large fraction of available energy into useable work. Diesel engines are rugged, dependable and fuel efficient. It is very common for diesel engines in heavy duty trucks to have a life of 1,600,000 km [Anon, 1999]. Generally in underground mines compared to electric powered equipment, diesel equipment provides more maneuverability. It can be assumed that the underground mining industry will maintain its reliance on diesel powered equipment keeping in mind the recent developments in other energy alternatives [Anon, 2001a]. A harmful aspect to the use of diesel as a fuel is its resultant emission as an adverse environmental exposure agent. Generally diesel particles are approximately one order of magnitude smaller than respirable dust aerosols in underground mines (typically less than one micron in size) [Kittelson, 1998]. Force of gravity has less effect on DPM due to its small particle size. The phenomenon of less gravitational attraction increases the settling and residence time of DPM in the mine atmosphere. High residence time of DPM as compared to other mechanically generated particles increases the chances of diesel particles deposition in the human respiratory tract. The small sized diesel aerosols penetrate deeply into regions of the human lung [Morawska. et al. 2005], which increase the health risks associated with long term exposure to diesel aerosols. Published studies documented the adverse health effects of DPM exposure [Walsh M.P., 1999]. Continuous and long term DPM exposure can result in respiratory disease, lung cancer, reduced lung capacity, and heart disease. NIOSH has declared that the reductions in DPM exposure would reduce cancer risks. In underground mines DPM determination is a challenging task and it is becoming a matter of serious concern due to the harmful health effects associated with the exposure of DPM. The current study involves the determination of realtime and shift averaged based DPM in underground mines of United States of America (USA). Realtime DPM was measured using FLIR Airtec monitors and shift averaged based measurement was performed by the MSHA approved NIOSH 5040 method. FLIR Airtec uses laser scattering approach to measures the Elemental Carbon (EC) component of the DPM. The results from the FLIR Airtec were compared with the results of NIOSH 5040 method and its performance was found satisfactory."

Jan 1, 2015

By J. Killian, S. Cox

Many questions exist within the geotechnical industry as to the applicability of Strength Reduction Factor (SRF) values to the design acceptance criteria (DAC) of mining operations. There are many factors that contribute to changes in the SRF estimate, some of which are numerical (e.g. dilation angle) and some of which are geometric (e.g. model grid size)[1]. Numerous studies have confirmed equivalent values of SRF and FOS are found for soil slopes of limited height as presented in, [2] and [3]. However, significant deviation of the SRF value was observed for highly cohesive materials (rock slopes) of heights typically encountered in mining, [4]. This paper builds on the work presented in [4], providing a more rigorous examination of the modeling parameters that control the SRF estimate. The failure mechanism assumed for this study was a simple circular shear surface in a uniform material. Both LEM and numerical methods are suited well for analysis of this failure mechanism. A parametric study was completed to evaluate and test the relationships of key numerical variables that affect the estimated value of the SRF using Itasca’s Fast Lagrangian Analysis of Continua (FLACTM) software. The effect of groundwater has been tested and may be significant but is not presented as part of this body of work for brevity and simplicity of presentation.

Mar 2, 2022

By R. K. Mehta

Conventional triboelectrification based dry coal beneficiation methods require ground coal as a prerequisite feed material, energy intensive static-in-line mixer or cyclonic tribocharger configuration, and transport and/or improvement in the design of free-fall separators to improve the separation efficiency of [me pyrite/mineral matter from coal. The proposed paper illustrates the two concepts. First, the use of ceramic media in a polyurethane lined attitor in achieving simultaneous grinding and differential charging. Second, the use of an electrocentrifuge to selectively separate coal from mineral matter present in the triboelectrified mixture. It is of interest to note that some ceramic media can satisfy the requirements of both desired density and work function to achieve grinding and differential charging.

Jan 1, 1996

By Eleanor Kentish, Nathan Bond, Edward Batty, Simon Webber, Alan Skarda

"Crossrail is Europe’s largest construction project — a new 100km rail route running through central London. A joint venture of BAM, Ferrovial and Kier (BFK) has constructed the tunnels and escalator shafts at the new Bond Street and Farringdon Stations. The recent trend in the UK industry towards sprayed secondary linings is driven by the potential for significant savings in cost and time. BFK is unique within Crossrail by constructing both sprayed and cast secondary linings. This paper presents a direct comparison between sprayed and traditional cast in situ secondary linings at Bond Street and Farringdon Crossrail Stations. An objective comparison is drawn between procurement and mobilisation periods, production rates, flexibility, tolerances and logistics in the tunnels. The technical challenges surrounding cast and sprayed secondary linings are explored, and recommendations are made of how each method could be improved for future use. INTRODUCTION It is well established that sprayed concrete offers a fast and effective method to seal the face of an excavation. In a relatively short space of time, sprayed concrete can be applied to an open face to support the short term ground loading on the tunnels during construction. Advances in sprayed concrete lining (SCL) technology — such as the use of wet mix processes, improved accelerators, fiber reinforcement, remotely controlled spraying robots, innovative surveying equipment and nozzleman competency schemes — have greatly increased the speed and safety of tunnel excavations using this technique. As a result, design engineers have become increasingly confident to use SCL primary linings as part of the permanent structural lining (Su 2014). Historically, long term ground and water pressure loads have been considered to be carried by the main structural or secondary lining, constructed using cast in situ concrete (Pickett 2014). However, the advances described above have made sprayed secondary linings a viable option, which has already been proven on the A3 Hindhead Tunnel (Arnold 2012). Sprayed concrete secondary linings offer potentially significant savings in cost and time during the construction process. The contractor does not need to procure a bespoke formwork system for each different sized tunnel — the SCL plant required is already on site for the primary lining. Each bay is sprayed with accelerated concrete, becoming self-supporting almost immediately — compared to moving and resetting the shutter, pumping concrete and waiting for it to cure. With sprayed concrete, working sequences and cross sections can easily be changed."

Jan 1, 2016

By P. Aparicio

The rheological properties of five kaolins, isostatically pressurized at 4 x10 Pa for 10 min in the presence/absence of water, was determined. Under dry conditions, measured viscosity values either decreased or remained the same. After treatment under wet conditions, measured viscosity values were 30-60% higher at high shear and 50-60% higher at low shear. These results correlate with variations in nanomorphology and structural order. Dry compaction degraded kaolinite crystals but wet-pressing appeared to cause an increase in the proportion of euhedral crystallites and a decrease in deformed crystals. Dry compaction decreased the low-defect phase proportion (ldp), but in contrast, the ldp in wet-treated kaolins remained constant or increased. Results show that hydrous pressure treatment produces a change in viscosity of kaolin suspensions, yielding the potential for improving paper coating performance, whereas anhydrous pressure treatment decreased or maintained the viscosity.

Jan 1, 2010

By T. Lupek, M. Buxton, A. de Jong

"With regard to the EU funded project ‘Real-Time Mining’ a sensor-based acquisition, collection and transmission of data for the resource extraction process will be developed. The key concept promotes the change in paradigm from a discontinuous to a continuous process monitoring. Especially concerning material characterization, machine performance and underground positioning ‘Real-Time Mining’ will provide sensor solutions as well as the interfaces for integration, management and visualization of the collected data for a permanent updating process of the resource model with the aim of near real-time optimization of decisions. On the basis of ‘Real-Time Mining’-Output a permanent monitoring of costs can be performed as well in both, the installation and the production process of a mine. Due to the collected data in terms of machine performance connected with the underground positioning information added with personnel tracking and mine surveys a comprehensive overview of process performance is available. By evaluating those information in a specific manner costs per unit will arise for monitoring and possibly controlling actions. INTRODUCTION By having a look into the future of mineral extraction projects, a new challenge for the Ore Mining Industry will arise in the short and medium term. Due to the depletion of currently mined mineral reserves in addition to the persistently high demand of mineral raw materials, the extraction of complex reserves will be necessary. By characterizing such deposits as not constantly graded and geometrically varying, the extraction process, especially concerning the requirement of a minimized zero-value material handling, will become economically ineffective by utilizing the traditional mineral resource management methods. Regarding the state-of-the-art mineral resource management process along the mining value chain, an intermitted, discontinuous sequence of actions is applied (Figure 1). Recently data will be collected from drill hole cores. These rock samples are analyzed in a laboratory. Based on those analyses a resource model is created whereby unknown data between drill holes is interpolated. This resource model is the basis for all mine planning actions including the selection of the mining method, extraction sequencing and the prediction of the expected performance. With the start of the production, real conditions (concentrations of elements, hardness, stability, etc.) can be observed and measured. As the production process is running accordingly to the above described mine plan, the verification of the initial assumptions happens at the earliest after processing of the extracted material. Even if deviations between the predicted and the actual performance are now recognized, the execution of corrective actions is not possible anymore."

Jan 1, 2016

By Keiichi Fujita, Michio Miyoshi, Hisashi Miyazaki

In the construction of "Hamacho" subway station (Tokyo Metropolitan Rapid Transit), in order to minimize ground surface settlement, the pipe-roof method was employed as an auxiliary measure when removing the portion between two parallel shield tunnels to form one large tunnel for the station. 14 steel pipes (dia.1,219.2mm, length 75m) were driven in horizontally so as to cover tunnels and support heavy and extremely soft covering soil and surface structures. Procedures of temporary supporting, excavation under compressed air, reinforcing, concreting, etc., and some comparisons with conventional methods are described.

Jan 1, 1979

By Alissa Lockett, Chris D. Breeds

Central Water Integration Project (CWIP) Segment 5-1 is the most critical segment of a regional water supply project that transfers groundwater from Burleson County to northern San Antonio, replacing over 20% of that City’s water supply with a new source. CWIP Segment 5-1 included three tunnel reaches totaling 10,350-ft and 5 shafts that were constructed inside the City in an area known to contain large karst features. This paper describes site work used to investigate the alignment for karst features, manage potential environmental impacts, develop the contract package required for mitigation and the means and methods used to mitigate the large karst features that were encountered.

Dec 1, 2022

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

By R. A. Lowe

The low-shear viscosity of kaolin slurries is one of the principal characteristics that determines whether the clay can be utilized for paper and ceramic applications. In this work, causes of poor low-shear viscosity and methods of improving rheology have been investigated. The presence of fine-grained smectite impurities within the kaolin was shown to detrimentally affect the low-shear rheology of slurries produced from these clays. It was also shown that mechanically working (i.e., pugging) a crude kaolin followed by desliming to remove these impurities can reduce the low-shear viscosity.

Jan 1, 1998

By E. Zahl, J. Whyatt, H. Lawson

The U.S. Mine Safety and Health Administration (MSHA) issued Program Information Bulletin P09-03 in April 2008, providing formal guidance on using programs that model the redistribution of stress during underground mining of coal. A key part of this guidance is visual observation and mapping of ground conditions. If a correlation between ground conditions and model output can be established, the model is considered to be verified, and can be used to guide mine design in similar ground. A simple scale is recommended for ranking observed roof, rib and floor conditions. This paper discusses optimization and implementation of a ground condition rating scheme in the gateroads of a deep underground longwall coal mine. Roughly 80% of each gateroad length deteriorated in a fairly uniform manner. However, this manner varied between gateroads, as did pillar size. The implementation of a ground condition mapping program, similar to that recommended in PIB P09-03, was successful in characterizing the ground response to mining in gateroads of a longwall coal mine.

Jan 1, 2013

By R. L. Lewis

The White Pine Mine is the second largest active underground copper mine in the United States, covering an area of approximately 34 km2 in the Upper Peninsula of Michigan. A numerical flow model of the White Pine Mine was constructed to evaluate engineering controls that would reduce the rate of mine water discharge after closure. Of the passive controls evaluated, the placement of low-flow bulkheads within the mine workings was predicted to offer the greatest benefit, reducing the rate of discharge by as much as 35 percent.

Jan 1, 1996

By C. A. Rowland

Comminution efficiency can be expressed in three different ways. Theoretical Efficiency: actual energy consumed, in a comminution machine compared to the theoretical energy required to make the size reduction. Operating Efficiency: compares the operating work index, calculated from production comminution machinery operating data, to the Bond Work Index from bench scale comminution tests or calculated from pilot plant operating data. Economic Efficiency: income compared to planned income. Using the Bond Work Index and operating work index, this paper explains how to determine operating efficiency.

Jan 1, 1998

By Laurent Rus, Bakar Amara, Jean Habimana

The La Fontaine Tunnel in Montreal, Quebec is currently undergoing major structural rehabilitation work and systems upgrade work to comply with current codes, standards and best practices in fire life safety and to extend its lifespan of this 55-year-old immersed tube tunnel for at least another 40 years. The paper discusses design consideration of ongoing works that include structural analyses to evaluate repair strategies for the post-tensioned reinforced caissons, the scheme to repair two leaky joints between caissons, the design of passive fire protection that involved in situ and real scale laboratory tests, and other tunnel systems upgrades.

Jun 13, 2023