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By T. Schepp, T. Friedrich

"The natural stage of deep mines operation is a closure of unnecessary shafts. It is extremely important to ensure a proper shaft closure to avoid stability loss and the associated damage to surface facilities in the future. For the still active shafts, it can be done by a dedicated shaft closure design, but even then, depending on the shaft closure method, it may be necessary to perform regular shaft inspections. The paper presents a short overview of shaft closure methods and available tools and devices developed in the last time for such shaft inspections. INTRODUCTION The natural stage of deep mines operation, commonly occurring after depletion of the reserves of mined materials, is a closure of unnecessary shafts. All over the world, the number of liquidated shafts grows continuously and the problem of shafts disposal is especially critical for deep shafts. The typical depth of 600 m of currently liquidated shafts in Poland may already be seen as a challenging task. The greater is the challenge of shaft closure in Germany where the last active coal mines for shafts with a depth of up to 1,300 m have been recently closed. It is therefore extremely important to ensure a proper shaft closure to avoid stability loss and the associated damage to surface facilities in the future. For the still active shafts, it can be done by a dedicated shaft closure design, but even then, depending on the shaft closure method, it may be necessary to perform regular shaft inspections. In many cases, it is more important to inspect old, abandoned shafts, where the wall stability or even liner type are not fully known. SHAFT CLOSURE METHODS Abandoning a shaft is a complicated task, as shafts, being the link between the surface and an underground network of workings, disturb hydrogeological and gaseous conditions in the rock mass (Sztelak, 1991). Closure procedures at older mine sites have been carried out in accordance with earlier legislative requirements. For very old shafts (+100 years), it means in many cases only a sealing of the shaft entrances by means of timber or concrete slabs. In the 20th century, the shafts were also closed by means of filling with grainy materials, but even then the retrospective activities at abandoned mine sites were extremely limited and in most cases no further monitoring measures were performed. The possible consequence of an improper shaft closure and lack of monitoring is presented in Figure 1."

Jan 1, 2019

By Reece Kurre, Gabriel Walton

"Roof bolting has long been used in underground mines across the world to provide ground support. Modern roof bolts are cheap and easy to install with the use of specialized machines as a part of the production cycle. Lhoist North America’s Crab Orchard Mine is an underground room and pillar limestone mine that uses mechanically anchored roof bolts for ground support. The mine currently employs two different roof bolting patterns: a standard 5 × 5 foot pattern, and a 2.5 × 2.5 foot pattern for use in areas with particularly hazardous roof conditions. The purpose of this study is to evaluate the relative effectiveness of each bolting pattern.A series of numerical models were created using RocScience’s RS2. The models were based on a symmetrical section of the mine at its deepest point, and were modeled using Generalized Hoek-Brown failure criterion along with a discrete fracture network. A series of sensitivity analyses were performed on the models by varying parameters such as joint friction angle, crack persistence, joint randomization, and tensile strength of the limestone. Based on the results of the original models and sensitivity analyses, it appears that the standard bolting pattern provides sufficient roof support capacity under almost all the expected conditions at the mine, since factors of safety below the design value of 1.5 were only found for individual bolts in a few of the worst test cases considered. These results can help improve the Mine’s productivity and reduce operating costs without compromising safety.INTRODUCTION AND CASE STUDY DESCRIPTIONLhoist North America’s Crab Orchard Mine is an underground limestone mine located in Crab Orchard, Tennessee. The mine is located under an 800-foot-high mountain, and outcrops on three sides. The mine is accessed through three separate portals and has two main levels, along with a partially developed third level. Extraction is accomplished by the room and pillar method using 50 × 50 feet pillars and 50 × 50 feet rooms. The mining height is limited to 50 feet to keep the pillar width to height ratio around 1.0. Each heading is excavated in a two-stage process that consists of a 30-foot-tall top heading and a 20-foot-tall bench. A distance of at least 30 feet is maintained between the two levels at all times (Crab Orchard Mine Technical Staff, 2017)."

Jan 1, 2019

By Rita Aiello, Stan Mack, Peter Werth, Joseph McCarney, Jozef Stachulak

"Johnson Matthey has developed the first diesel particulate filter (DPF) for underground mining that controls particulate matter (PM) at the same time as maintaining emissions of NO2 at or below engine baseline levels. DPF technology is critical for controlling PM which is classified as a carcinogen, but passively regenerating systems rely on the use of oxidation catalysts that can potentially increase NO2 emissions. This paper reviews the development of low-NO2 PM control technology and the results from testing this technology underground on diesel mining equipment. KEYWORDS Decomposition catalyst, Diesel particulate filter (DPF), Diesel particulate matter, Mining Continuously Regenerating Trap (CRT®), NO2, SCR INTRODUCTION The introduction of diesel particulate filter (DPF) technology on heavy duty diesel (HDD) engines has been an important step towards addressing the clean air and health concerns for mining companies. Control of diesel particulate matter (PM) emitted from diesel engines is already being implemented for on- and off-road vehicles, and similar legislation is being prepared for mining equipment. In addition to PM, the diesel emission control strategies (DECS) also reduce carbon monoxide (CO) and hydrocarbons (HC). Some DECS control oxides of nitrogen, or NOx, which is composed of NO and NO2. Johnson Matthey has led the development of emission control technologies for diesel engines for almost 30 years. Over the last ten years alone JM has supplied over 3 million Continuously Regenerating Trap (CRT®) DPF systems for on-road vehicles, and over 200,000 systems for off-road vehicles. The patented CRT technology combines a diesel oxidation catalyst (DOC) with a DPF to effectively trap harmful PM from diesel exhaust, while removing CO and HC. The DOC converts part of the engine NOx to NO2, which reacts with the trapped soot to regenerate the filter. As engines become more fuel efficient, less waste heat enters the exhaust. This can be a disadvantage for after-treatment systems as it leads to lower catalyst operating temperatures. The CRT system regenerates passively, without addition of heat, at temperatures that are typical of diesel engine exhaust. JM recently launched the Mining CRT system which integrates CRT technology with NO2 abatement to reduce PM and tailpipe NO2 from underground diesel mining equipment. This is the first technology proven to control both PM and NO2 emissions for a cleaner, healthier working environment. The Mining CRT is also cost-effective compared to other technologies."

Jan 1, 2019

By Fulian He, Jianhang Chen, Shoubao Zhang

"Fully grouted rock bolts have been used in mining industry for many years. Significant research has been conducted to evaluate the load transfer behavior of fully grouted rock bolts with experimental programs. However, compared with that, less work has been conducted with analytical modelling. Therefore, in this paper, the authors used an analytical model to study the load transfer behavior of fully grouted rock bolts. To confirm the credibility of this analytical model, an in-situ pull-out test was used to validate this model. There was a close match between the experimental result and the analytical result. Following this, a parametric study was conducted with this analytical model. The influence of coefficients, Young’s modulus of the rock bolt and the diameter of the rock bolt on the load transfer performance of rock bolts were studied. Furthermore, the load distribution along the fully grouted rock bolt was analytically studied. The results show that the axial load in the rock bolt decayed from the loaded end to the free end independent of the pull-out load. However, the trend of the load distribution curve was influenced by the pull-out load. This paper was beneficial to better understand the load transfer mechanism of fully grouted rock bolts.INTRODUCTIONRock bolts have been used in the mining industry for a long time. They are used as the reinforcement tendons to keep the stability of openings in underground mining and the slope in open-pit mining. Furthermore, rock bolts are commonly used not only in the mining engineering, but also in civil engineering (Thompson, Villaescusa, and Windsor, 2012).The rock bolt is a tendon which can be a rod or a cable inserted into a borehole drilled in rock masses or soils. Traditionally, the material of rock bolts was steel. However, engineering practices showed that the steel rock bolts can be easily corroded by the moist environment in underground mines. Next, Fiber Reinforced Polymer (FRP) was used to manufacture rock bolts, which are termed as FRP rock bolts. Experimental results proved that the FRP rock bolts can effectively reinforce the surrounding rock masses without being corroded (Wang et al., 2018)."

Jan 1, 2019

By D. M. Ziebarth

"Normal sequence of operations to develop a new underground mine is: construct and outfit headframe for shaft sinking, sink shaft, construct and outfit shaft sump, develop shaft station and shaft bottom steel. In an effort to reduce the overall project schedule, an innovative plan was developed to install service shaft steel below station level, prior to the completion of the shaft sinking effort. To better evaluate the construction of this substantial steel tower, a preliminary constructability evaluation was conducted, including the best method of supporting the main tower; from the bottom, middle or top of the tower. The design criteria and plan involved: •,Develop access from existing service shaft, 25 km underground •,Use of materials to maximize strength while minimizing corrosion exposure •,Estimating the location of the shaft centerline •,Over excavating the station and shaft below station to allow future shaft steel repositioning •,Designing the tower steel for modular installation •,Incorporate commissioning considerations, such as suspension of the cheese weights during steel installation •,Provision for covered stair access to shaft bottom •,Enclosed shaft envelope with open panels to allow visibility and ventilation The design approach was innovative and this paper will describe the design principles and challenges encountered while providing insight into the solutions developed and implemented; especially the modular construction and installation methodology. INTRODUCTION In an effort to expand the mining operations, a plan was developed to construct a new service shaft closer to the new mine workings and convert the existing service shaft to a production shaft at the Potash Corporation of Saskatchewan Inc. (PCS now Nutrien) Rocanville Potash mine in southeast Saskatchewan. The new service shaft required a multi roped friction hoist operating a cage / counterweight, rope guided conveyances to support the operational requirements. The service shaft is an integral part of the mining infrastructure as it provides access to the underground workings, transport personnel and materials underground for operation and maintenance of the mine. The shaft also allows for services required for safe operation of the underground mine, power supply, controls, communication, dewatering and fresh water supply."

Jan 1, 2019

By Ken McIntyre, Trodel Wolf-Dieter

"Sirius Minerals is a UK based fertilizer development company focused on advancing into operation its polyhalite project in North Yorkshire, England. The operation is known as the Woodsmith Mine which has an estimated 2.7 Billion Tonnes of reserves and is currently in the construction phase. DMC Mining Services was selected to carry out the construction of four shafts for the project, a production shaft of 6.75m diameter to a depth of 1594 m, a ventilation shaft of 6.75 m diameter to a depth of 1565 m, and two additional shafts to support the construction of the material transport system (the MTS and Lockwood Beck intermediate) to 360m in depth for servicing the underground conveyor network for transport of product from the mine site to the costal port facilities located at Teasside. This paper will review the status of the project to date and the innovative approaches that DMC is utilizing to ensure a safe and successful shaft sinking project. INTRODUCTION The Woodsmith Mine in North Yorkshire is a Sirius Minerals-owned deep potash and polyhalite mine located near to the hamlet of Sneatonthorpe, Whitby in North Yorkshire, England, approximately 75 km east of York. The area of interest is more than 700 km2. The £3.2 billion project is to develop the Woodsmith Mine to extract polyhalite, and a tunnel system to transport it to a materials handling facility and harbour at Teesside. The site is the world's largest and highest-grade deposit of polyhalite and is expected to produce 20 million tonnes of polyhalite, potash and POLY4 per annum, as well as create over 1,000 direct jobs and many more indirectly. It has the potential to generate over £2 billion of annual exports for the UK. As the project will require mining to be undertaken in the North York Moors National Park, many objections were raised about the mine. Sirius Minerals has gone to great lengths to ensure that the project is sensitive to the local landscape, including: mineshaft head frames that will be positioned below ground to reduce their visual impact; surface buildings will be kept to a minimum; and the entire site will be landscaped and screened by existing woodland to blend in with the surrounding area. The project will also abide by strict environmental limits which govern our activity during the construction phase."

Jan 1, 2019

By J. A. Scott, K. Moreau, H. Shang

"Trials of automated technology at underground mine sites around the world have reported increased production and the potential for lower energy consumption. Autonomous mining eliminates a range of delays related to operator downtime and travel to the workface and facilitates continuous operation in conditions that are unsafe for workers. Automation also introduces complexities and safety hazards arising from equipment–personnel interactions; automated processes must be isolated from other stope-cycle–related activities such as production drilling, development, loading, and backfilling, poten¬tially requiring changes to the mine design to maintain an efficient and safe operation. This paper reviews and discusses the implementation of automated equipment in deep underground mining operations and the challenges and advantages associated with the technology. ¦ KEYWORDS Automated equipment, Emissions reduction, Energy, Productivity, Sustainability, Technology, Underground mines RÉSUMÉ Des essais de technologies automatisées dans des sites miniers souterrains aux quatre coins du monde ont indiqué une production accrue et la possibilité de réduire la consommation d’énergie. L’exploitation minière autonome élimine tout un éventail de retards liés aux temps d’immobilisation des opérateurs et aux déplacements vers le front de taille, et facilite l’exploitation continue dans des conditions qui s’avèrent peu sécurisées pour les travailleurs. L’automatisation introduit également des complexités et des risques pour la sécurité, qui surviennent en raison des interactions entre l’équipement et le personnel. On recommande d’isoler les procédés automatisés des autres activités liées au cycle des chantiers telles que le forage de production, le développement, le chargement et le remblai, ce qui pourrait entraîner des changements au niveau de la conception de la mine afin de préserver rendement et sécurité dans l’exploitation. Cet article examine et aborde la mise en oeuvre de l’équipement automatisé dans des exploitations minières souterraines profondes, ainsi que les enjeux et les avantages associés à cette technologie. ¦ MOTS CLÉS durabilité, énergie, équipement automatisé, mines souterraines, productivité, réduction des émissions, technologieINTRODUCTION As the mining industry continues to exhaust easily accessible orebodies, the need for efficient, deep (typically below 2,500 m) mine operations increases (Atlas Copco, 2013a); however, the mining process can become economically infeasible at great depths because operation costs drastically increase. This has resulted in investigations into automating mining operations as the industry strives for improved productivity (Schunnesson, Gustafson, & Kumar, 2009) and ways to remove personnel from hazardous work areas."

Jan 1, 2019

By F. Calizaya, S. Bhattacharyya

"This study presents the results of a set of sound level measurements carried out in three underground mines where auxiliary fans are used regularly. Sound levels as high as 100 dB(A) by the workings and 115 dB(A) by the fans were measured in these mines. These levels are quite high even for intermittent noise. Ventilation layouts and best practices used to overcome potential problems related to overexposure to fan noise in underground hard-rock mines are presented here. Factors such as fan type, rotational speed, and silencer-duct arrangements and their effects on noise attenuation are discussed. INTRODUCTION Auxiliary fans are used in hard-rock mines extensively. They are used to ventilate development headings, crusher rooms, conveyor transfer points, and underground shops. They are also used in developing long tunnels and ramps. Depending on the flow requirements and space restrictions, single or double stage axial fans with rigid or flexible ducts are used. Usually, they are high pressure (3.75 kPa) fans with flow rates ranging from 7.1 m3/s to 30 m3/s. The input power varies from 15 kW to 113 kW (Mutama, 2004; O’Connor, 2008). Typically, a 113 kW fan can produce sound levels as high a 113 dB(A) (Howes, 2005). Silencers are often omitted for cost reduction purposes or when used, they are not well maintained. Furthermore, silencers provide limited attenuation depending on their length and type. Typically, the sound attenuation ranges from 10 dB(A) for a 1 × D silencer to 14 dB(A) for a 2 × D silencer, where D is the fan diameter. In a mine, the silencer is subject to wear and tear, especially when the silencer is used in harsh environments. The interior lining can get clogged and the acoustic fill can get covered by dust and diesel soot, thus reducing the silencer performance. Periodic cleaning of the interior casing can increase the attenuation capacity of a silencer by 6 to 9 dB(A) (Dabson & Acuña, 2017). However, this requires a special silencer design in which the inner cartridge can be removed, the sound absorbing material replaced, the inner casing cleaned and the whole set retrofitted. A number of techniques can be used to reduce auxiliary fan noise in underground mines. These range from selecting the right fan for the job to installing adequate silencers. The choice depends on the air quantity requirement at the working place, cross-sectional area of the opening, duct diameter, fan type (axial or centrifugal) and local restrictions. Auxiliary ventilation layouts and best practices used to overcome potential problems related to overexposure to fan noise in underground hard rock mines are presented here. Factors such as fan type, rotational speed, duct diameter, and silencer-duct arrangements and their effects on noise attenuation are discussed."

Jan 1, 2019

By Ting Ren, Lihai Tan, Alex Remennikov, Xiaohan Yang, Xueqiu He

"Due to recent coal bursts in Australian coalmines, research of coal bursts has attracted intensive interest from mining researchers and engineers worldwide. Previous research has shown that the sudden drop of fractal dimension may be a precursor of catastrophic failure of rock. This paper examines the fractal characteristics of temporal-spatial distribution of acoustic emission signals released during the compression loading process of coal. This research suggests the possibility of coal burst forecasting based on acoustic emission data. The concept and calculation equation of fractal dimension is introduced in this paper. Additionally, uniaxial compression experiments of Australian coal samples are conducted, and the acoustic emission waveform and 3D location are recorded simultaneously by eight sensors Express-8 AE monitoring equipment in the loading process. The experimental results indicate that the continued slowdown of fractal dimension in time sequence can be used as a precursory signal of coal sample brittle failure. The fractal dimension of the spatial distribution of acoustic emission events decreases with the evolution of coal fracturing.INTRODUCTIONCoal bursts refer to the catastrophic failure of overstressed coal subject to the dynamic and static loads. In recent years, coal bursts have occurred in major coal mining countries and this phenomenon has attracted the research interests of international mining and geotechnical scholars. A total of five coal burst accidents happened in Australian coalmines since 2014. On October 20, 2018, a coal burst occurred at Longyun Coalmine in China’s Shandong province, which led to 21 fatalities. Unfortunately, even after decades of research, it seems neither more accurate forecasting methods nor comprehensive controlling measures put forward by researchers have solved the problems posed by coal bursts.As an instantons energy releasing process, coal bursts are always associated with energy dissipation in the forms of acoustic emission, micro seismicity, and electromagnetic radiation (Yamada, Masuda, and Mizutani, 1989). It is believed by many researchers that the frequency–magnitude relationship of micro seismicity induced by rock failure satisfies Gutenberg-Richer relationship as well (Feng et al., 2017). Hence, based on the principal and theory of earthquake source locating, micro-seismicity monitoring equipment has been adopted in many coalmines to locate seismic event origins associated with coal and rock failure in an attempt to better forecast coal and rock bursts. Although many parameters such as b value (parameter of Gutenberg and Richter’s law) (Lu et al., 2015) have been adopted as indicators of risk, the forecasting of coal bursts is still of low accuracy. The same is true with earthquake prediction, as it remains as a worldwide problem even after decades of research and practice. Acoustic emission (AE) methods are now widely adopted to detect rock failure processes under an applied stress for application predicting the abrupt failure of rock in the laboratory (Li et al., 2017). Previous studies have found that significant overlap exists between research regarding AE and micro seismicity with respect to generation process (both are concerned with the generation and propagation of elastic wave) and event origin location, as geophysical signals of both are same (Lockner, 1993). That is, the frequency–magnitude relationship and early-warning indicators found by AE research in the laboratory have a potential applicability to in-field micro seismic monitoring of coal bursts. Through experimental study, Feng and Seto found that the temporal distribution of acoustic emission counts of rock have distinct fractal structures during load-increase processes (Feng and Seto, 1999). Landis and Lucie found good correlation between fracture energy and AE energy during testing of mortar specimens as well (Landis and Lucie, 2002). Based on preliminary experimental study, many schol"

Jan 1, 2019

By B. Burger, T. Bester, S. Deonarain, L. S. Schultz

"This paper details the process followed to raise drill and equip a 6.1 metre diameter vertical service shaft at Glencore’s Mindola Deeps project in Kitwe, Copperbelt Province, Zambia. The project scope comprises a shaft collar, bulk air intake, a pre-sink to -90 metres and raise drilling the shaft from surface to a final depth of 1,892 metres underground, in four separate lifts of approximately 475 metres each. Equipping of the shaft steelwork, headframe erection and commissioning the shaft for hoisting. In addition, the scope included the development of a decline down from 5430’ level underground to the new shaft position on 6205’ level. This paper will provide some insight into the successes and challenges encountered during execution of the shaft works to date and provide some learnings for future projects of a similar nature. INTRODUCTION The Mindola Mine is situated to the west of the city of Kitwe in the Copperbelt Province of the Republic of Zambia (Figure 1). The mine is owned and operated by Mopani Copper Mines Plc (MCM), whose shareholders are Glencore AG (73.1%), First Quantum (17.9%) and ZCCM Holdings Plc (10%).Productivity at the Mindola mine has been adversely affected because of significant ventilation and ore re-handling challenges, which are caused by the dilapidated infrastructure, and design of the existing vertical and sub vertical shaft system. In the circumstances, it was apparent that it was necessary to sink a new vertical shaft that would increase the volume of fresh air down the mine, improving the underground working environment and the current hoisting restrictions, resulting in an increase in productivity and efficiency. Because there were two existing levels ideally situated and perpendicular to one another and because a third level was in close proximity to that perpendicular and because the mine required a ramp down to shaft bottom in any event, consideration was given to raise drilling the shaft as opposed to using conventional blind sinking methodologies."

Jan 1, 2019

By R. E. Ray

"As real estate for new development in urban settings becomes scarce, commercial high rises are being constructed above open passenger rail tracks and vehicular roadways. Rail and roadway overbuilds are treated as tunnels requiring emergency ventilation systems for train or automobile and truck fires. The value of floor space in residential and office towers poses challenges to engineers responsible for designing fan rooms and shafts for tunnel ventilation systems within the towers. This paper describes a case study of the unique incorporation of tunnel ventilation fan plants in the overbuild structure of a passenger railyard and an adjacent roadway.INTRODUCTIONTunnel ventilation systems are required for passenger rail and transit (subway) tunnels by the NFPA 130 Standard for Fixed Guideway Transit and Passenger Rail Systems, and the NFPA 502 Standard for Road Tunnels, Bridges, and Other Limited Access Highways requires tunnel ventilation systems for vehicular (road) tunnels. Passenger rail and transit (subway) tunnels are typically ventilated with a series of shafts placed longitudinally along the tunnels to provide piston relief for normal train operations and emergency ventilation of train fires utilizing reversible axial flow fans. The shafts are incorporated in dedicated ventilation buildings that house the tunnel ventilation fans and starters, switchgear to power the fans and other equipment and systems in the building, Programmable Logic Controllers (PLCs) to control fan operation with Supervisory Control and Data Acquisition (SCADA) software, and HVAC fans and ductwork to ventilate the spaces in the building. These ventilation buildings may also provide access to the tunnels below with ingress/egress stairs for use by first responders and firefighters entering the tunnels and train or transit system passengers exiting the tunnels in an emergency. A photograph of a passenger rail ventilation building that encompasses four tunnels is shown in Figure 1."

Jan 1, 2019

By J. Herhold, S. Plaum

The focus within the economical optimization of projects, which are conducted underground, shifts more and more towards the conduction of construction work underground. Underground operations can be defined in a wide range of various projects, from underground mining tasks to the construction of engineering structures. Within these projects the conduction of construction work cannot only be defined as absolutely necessary, but sometimes also as optimizing for underground processes (e. g. installation of workshops underground to support the mining processes). Even though the conduction of underground construction might cause positive outcomes concerning the productivity, it also tends to be challenging due to local (sub-surface) conditions and influences. To minimize the risk of failure and sudden events within in the conduction of construction work underground, the tool “work preparation” shall be used. Under the given constraints, such as local influences, expected construction work and set time frame, the conduction of the construction work will be planned in advance by consideration of the construction logistics as well as the selection of a fitted construction technique. PROBLEM DEFINITION Economic Challenges - Raw Material Extraction Enterprises in the construction, mining and raw material extraction industries are increasingly under the pressure to perform economically to sustain their position on the global market. Profitability, efficiency and productivity are the basic conditions to be an active participant on the global market as well as a business partner and contractor for mining and construction projects or projects related to the extraction of raw materials. The completion of large-scale as well as common construction projects above ground has been under the pressure to minimize costs and time whilst maximizing the potential outcome, in the meanings of quality and economic gain, for more than a decade now. Whereas the construction industry has to fight the competition on the market with efficient project outcomes, the mining industry has to find ways to perform efficiently to further conduct the extraction of decreasing raw material deposits. The ongoing exploitation of existing raw material deposits to satisfy the constantly increasing raw material demands world-wide, led to the predicament that economically mineable deposits have decreased dramatically. Even tough mineral deposits do still exist on a global level, near-surface deposits decrease rapidly. Therefore, the extraction of raw materials within mining operations will be relocated further away from the surface in greater depths. With the growing distance from the surface to the mineral deposit, the extraction costs will increase many times over. With that in mind, the extraction costs will increase whilst the economic efficiency will decrease. The extraction of certain deposits will no longer be profitable with the common approach. To further extract raw materials efficiently even in greater depth, companies have to change their practice in different ways. That leads to the fact, if the deposits are in the depths, where the extraction processes won´t be economically, other (support) processes have to be in order to guaranty an economical corporate process itself. This precept will divert the focus from the actual mining process to support processes, where potential for optimization still can be found, as shown in figure 1.

Jan 1, 2019

By Laura Steeves, Inoka Eranda Perera, Jhon Silva, Arend Spaeth

"This paper reviews the main concepts ruling the design, implementation and performance of active explosion barrier systems for underground coal mines in the USA. The document examines the parameters needed for the design of this type of system, such as overpressure and flame speed, suppressant deployment speed and duration time of the active barrier. The document also discusses the available solutions for gassy mines and the concepts behind the selection of machined mounted and roadway active explosion barrier systems. The paper includes a review of active explosion barrier systems developed in the USA and South Africa. The paper provides an overview of the current status of this technology in the underground coal mining industry in the USA, and the possible implementation of such systems. The paper concludes with the identification of the future work needed for the successful implementation of the systems in several conditions to enhance the safety of underground coal mine operations and to provide more tools to the miners for their safety.INTRODUCTIONUnderground coal mine explosions can be addressed in two ways, through prevention or mitigation. The United States mining industry practices have emphasized the prevention of explosions in underground coal mines, with little being done to mitigate the explosion once it occurs. Despite successful practices for the prevention of underground coal mine explosions in the US, the threat of an explosion does still exist. Other mining countries around the world have developed and implemented mitigation systems such as active explosion barriers in their underground mines. In the 1970s, the United States Bureau of Mines (USBM) carried out extensive research on the use of active or triggered explosion barrier systems in the US; however, they are not currently used.Explosion barrier systems do not prevent explosions but mitigate the propagation of the shockwave and flame to other areas of the mine. The use of active explosion barrier systems enhance the safety of underground coal mines. Active or triggered explosion barriers will detect the arrival of the shockwave or flame front of the explosion and release inert material to suppress or extinguish the flame. The technology required for active barrier systems is readily available based on their presence in other mining countries and must be adapted for their use in US coal mines. The adaption must consider the coal dust and methane concentrations in US coal mines, the mine geometry, and the mining equipment used."

Jan 1, 2019

By M. G. Beukes

"In South Africa most of the large gold mines operate between 1500m and 4500m below surface where reef is accessed initially through a vertical shaft system then via a network of tunnels and mined in either a longwall, sequential grid or scattered mining configuration. Due to the complexity of the ventilation networks used to ventilate these mines and the potential disastrous consequences associated with underground fires, it is of utmost importance that these mines are managed in such a way that underground fires are prevented. However, if they do occur the fires are managed to firstly prevent the loss of life and secondly protect the infrastructure and viability of the mine. The aim of this paper will be to: • Discuss current SA mining legislation regarding underground fire prevention and control. • Examine these fires from a risk management perspective by means of a bowtie assessment. • List and discuss the major Threats and Consequences as determined by the bowtie assessment. • Discuss the various prevention and consequence controls for deep level underground fires. • Examine how to effectively run an emergency control room. From this, a practical way of designing, implementing and managing an underground fire management system is explored. Lastly, the paper identifies new technology and ways of thinking and how these can be used to combat underground fires. INTRODUCTION The orebodies of South African gold mines are generally narrow tabular structures that vary in thickness between 0.8m and 1.2m with an inclination of between 200 and 700. This, coupled with depths of between 1500m and 4500m, as well as the unpredictable geology, creates unique challenges and significantly impacts on mine designs and mining methods. In general, gold bearing reefs are accessed initially through a vertical shaft system then via a network of tunnels and mined in either a longwall, sequential grid or scattered mining configuration (Figure 1). Mining is very labour intensive with very limited mechanisation opportunities and this increases the risk to human life if an underground fire occurs. On 16 September 1986, one of the worst mining disasters in SA mining history took place when 177 mineworkers were killed at Kinross Mine. An acetylene tank sparked flames that swept through the mining tunnel igniting plastic covering on the wiring and the flames also set fire to polyurethane foam. The burning plastic combined with polyurethane and the toxic fumes that filled the shafts caused the miners death. This incident was a stark reminder of the serious consequence that underground fires can have on human life as well as the crippling financial and asset impact for the mining companies. Over the past thirty years, the SA mining industry reduced the number of mine fires significantly by replacing normal timber support with fire retardant treated timber, alternative support systems such as backfill and elongate support and many other fire prevention initiatives. Although the number of fire incidents and number of fatalities due to fires does not show a direct correlation because of various factors, the controls put in place against fires has had an impact on the number of fire and explosion fatalities (Figure 2)."

Jan 1, 2019

By R. Bishop, J. Baggett, J. Monsalve, J. Hole, N. Ripepi, A. Abassi

This work focuses on the operational and safety issues associated with karst voids in large opening underground mines. Issues include water inrush, structural instability, and engineering uncertainty in these environments. Coupled with the fracturing prevalent in folded sedimentary rocks, karsts are complex and challenging ground control risks. Traditional methods of predicting karst locations, such as probe drilling, are impeded by the inconsistent spatial distribution and variable sizes of the features. Ground penetrating radar (GPR) is a geophysical technique that transmits radio waves into a medium and subsequently detects reflected waves via a receiver. The travel time and energy of received signals are then processed and interpreted. The difference in material properties between limestone and open karsts causes strong reflections. GPR is frequently used as a geophysical surveying technique in several industries, however there is a lack of published research on underground mining GPR applications. The purpose of this work is to prove the viability of GPR in underground stone mines for karst detection, and to discuss the importance of karst detection ahead of mining. INTRODUCTION The Mine Safety and Health Administration (MSHA) currently lists 116 active underground stone mines in the United States, the vast majority of which extract limestone for crushed stone products. These limestone mines have the potential to encounter karst voids at some point in their operation, as most karstic regions of the United States develop in limestone rock masses (Kuniansky, Weary, & Kaufmann, 2016). Karsts, the cavities formed by the dissolution of carbonate rock, have long plagued the mining and tunneling industries, as well as been a hindrance on the Earth’s surface, producing sinkholes and ruining otherwise valuable land for construction and public use. The impact of karsts on the Gavarres tunnel in Spain is well documented by Alija et al; constant instability conditions, material spills into the tunnel, and unexpected cavities seriously delayed the project deadlines and “were not foreseen in the design” (Alija, Torrijo, & Qunita-Ferreira, 2013). At the water supply project in Sohngua River, China, Bin et al detail the presence of both water and sediment filled karsts which are sources of disastrous conditions at this tunnel (Bin, et al., 2017). A hydrological tunnel in Lebanon encountered numerous massive karsts in the tunneling path which required remediation via friction anchors, rockbolts, welded wire fabric, channel steel arch segments, invert steel beams, and shotcrete (Leech, Jaoude, & Ghanem, 2008). From a design standpoint, rock mass classification schemes, such as the RMR from Bieniawski and the Q-system from Barton, are not able to represent the true nature of a karstified carbonate rock mass, and therefore complex case-by-case analyses of underground conditions are necessary (Andriani & Parise, 2017).

Jan 1, 2019

By E. Stone, R. Reagan

Risk of hand injury is very real for operators carrying out conventional bolting operations with power torque tools, reaction arms and backup wrenches. Bolting operations of this type are common today in the installation and maintenance of heavy mining machinery and equipment. Newer solutions have become available that have the potential to dramatically reduce the risk of hand injuries in mining applications. MINING APPLICATIONS Within the scope of mining operations, various types of equipment are used such as tunnel boring machines, bucket wheel excavators, draglines, material handlers, screens, pumps, crushers, continuous miners and longwall systems. Design of these machines typically includes larger diameter bolts for strength and durability. Due to rugged use all machines require frequent maintenance and service which requires the use of heavy industrial bolting tools and methods. Those engaged in bolting operations include technicians working for end-users, equipment manufacturers, general contractors and others who provide services in mining operations. Most all personnel involved with these activities are engaged with use of high power bolting tools and procedures. Training is essential to raise the awareness of bolting safety and to avoid accidents. However improved bolting tools and procedures can play an even more significant role in further improving the safety of all those engaged with bolting in the mining industry. SAFETY CONCERNS Professionals working in the mining industry are constantly looking for ways to further reduce risk to health and safety. Bolting operations which are fundamental to service and maintenance of mining equipment are often overlooked as a potential area for improvement. Several areas of bolting operations offer potential for improvement in safety and avoiding accidents during equipment maintenance. This paper addresses the safety concerns associated with reaction arms and backup wrenches in conventional bolting applications (Figure 1).

Jan 1, 2019

By J. Sottile, V. Androulakis

Operators of underground coal mine shuttle cars are exposed to numerous hazards including noise, dust and musculoskeletal trauma. The repetitive nature of shuttle car operation leads to fatigue-related incidents and soft tissue injuries. The poor visibility conditions, and dust and noise increase the occupational hazards to the operator, as well to other miners. To reduce the risks for all miners, towards providing a safer working environment for all workers, the introduction of autonomous shuttle cars is essential. This paper introduces a project to demonstrate the feasibility of incorporating autonomous shuttle cars in the underground coal mining cycle. The autonomous shuttle car will be able to localize itself, to map its surroundings and to navigate in an underground GPS-denied environment. It will also navigate efficiently by fusing different on-board sensor modalities, autonomously planning the optimum path and traversing around the mine while avoiding collisions with humans and other static and dynamic obstacles. This will be achieved by exploring and testing different state-of-the-art techniques and off-the-shelf components, and integrating them into existing equipment, i.e., retrofitting an actual shuttle car. Moreover, a modified mining system will be demonstrated which will incorporate the autonomous shuttle car, capable of making real-time decisions, into the mining cycle. The system will regulate the interactions between the autonomous machinery and the human dynamic, with emphasis given to the safety of the workers, and enable the real-time, remote supervision of the mining process. The focus will be on coal mines, where the room and pillar mining method is used. INTRODUCTION The growing demand for mineral supplies combined with the steady decline in the available surface reserves has driven the mining industry to mine deeper underground deposits. These deposits are difficult to access, and the environment may be hazardous to mine personnel (e.g., increased heat, difficult ventilation conditions, etc.). Moreover, current mining methods expose the miners to numerous occupational hazards such as working in the proximity of heavy mining equipment, possible roof falls, as well as noise and dust. In recent decades, the utilization of autonomous machines has evolved in the mining industry to provide increased health and safety to mine personnel and reduce their exposure to adverse conditions. Automation aims to remove the workers from the hazardous conditions which may be present in an active mining area and place them to a more comfortable and safer environment at a distance from the active mining face. Examples of incorporation of autonomous machinery in the mining industry include the fleet of more than 100 autonomous mine trucks that are employed at the Rio Tinto’s iron ore mines in Western Australia for material haulage. There are also semi-autonomous, teleoperated LHD machines employed at several mines around the world (e.g., Sweden, USA, China). However, the operation of the autonomous machinery in these cases is either partial (semi-autonomous, teleoperated vehicles) and of small-scale or occurs at surface mines where GPS significantly facilitates the autonomous navigation of them.

Jan 1, 2019

By J. Holtzhausen

"An analysis of operating costs for underground mining operations in the current global economic climate considers the financial burden for a ventilation system to be in vicinity of 30–50%. These operating costs are often overlooked by management teams in the greater scale of things when looking to save money in the procurement phase. This oversight to operational costs can be as little as the effective delivery of ventilating air to the work zone. One of the biggest opportunities for substantial savings and improvements can be realized in the selection of a quality vent duct that is suitable and fit for purpose. The key component to the selection process for quality products is a solid selection criterion that is followed during the tender process. This allows the management team to filter out unsuitable suppliers and products. The case study identifies some of the key components that were considered in the procurement and selection process for lay-flat ducting products. These included the characteristics and strength of the materials. The selection criteria also considered a ducted performance comparison that offers the best aerodynamic performance with some of the following components. • Airflow at Duct Face (m³/s or cfm), Fan Pressure (Pa), Air Power (kW or hp), Assumed Fan Efficiency, Annual Running Costs, K – Factor or Lambda, Leakage Factor, Joining Method and available Duct Lengths with weights. • Critical components considered were the current Testing standards available for: o Bursting Strength AS 4878.5, Mass AS 2001.2.13, Tensile Strength AS 4878.6, Tensile Strength AS 2001.2.3.1, Tear Strength AS 2001.2.10, Tear Strength AS 4878.7 • Other key considerations were: o Warranty Claim, Damage claims, Local storage / operations, community engagement and relationships, current testing data, previous issues, after sales service with technical assistance, etc. Hidden costs associated with product failures and operational stoppages are often not quantified during the tender process. Buyer beware. INTRODUCTION The largest constraint underground mining operations currently face are their operating efficiencies and electrical costs. The overall cost of an operations ventilation system and its components requires more focus to identify what opportunities exist to maximise efficiency and effectiveness. This tender process may not always be clearly understood and it should be broken down into fewer components to achieve quantifiable results."

Jan 1, 2019

By H. S. Venkatesh R. Balachander, G. C. Naveen

During the construction of a 1020 MW underground hydroelectric project in Bhutan a huge rock fall took place in the Downstream Surge Chamber (DSC) during March 2016. The total quantity of rock in the fall area is estimated to be about 1,50,000m3 (2.6 billion cubic feet), out of which about 25,000m3 (0.44 billion cubic feet) of muck was removed. The removal of muck was stopped apprehending that the cavity formed due to the rock fall may get further aggravated leading to widening and destabilising the adjacent transformer hall cavern or it might day light as the top cover was about 190m (623 feet). As the fall has virtually blocked the 314m (1030 feet) long cavern and divided it into two different chambers (south and north), and that the muck cannot be disturbed, it was decided to erect concrete wall on either side of the fall up to the cavern roof and then later address the filling of the cavity with appropriate fill material. As the access to the DSC was there for the southern side it was decided to extend a cable tunnel which was terminated at a distance on the north side of the cavern by D&B so that once it gets punctured into the north wall of the DSC it can be used to access the fall from this front too. This is a unique situation where in every blast approaching the DSC, the parting between them is diminishing and hence the tunnel blast will be exerting axial load on the parting wall leading to dynamic transient loading conditions and buckling may take place on the northern wall of DSC. This paper describes the various drill blast combinations adopted for successful excavation of this tunnel.

Jan 1, 2019

By G. Bonin, A. Jamal, G. Preciado, S. Gillis

"Accurate, easy to obtain, and reliable methods of measurement are the cornerstone of shaft and tunnel developments - during their sinking, operation and maintenance, or in some cases, remediation. This paper presents a new methodology to capture existing shaft conditions in such a manner that they can be transferred from the field to a digital copy, where they can be stored and used for engineering design purposes in a space not directly affected by the costs associated with schedule and equipment performance. The methodology utilizes basic principles of excavation alignment (plumb lines and survey instruments) while adding modern LiDAR, geolocation and survey control tools that can more completely capture the surrounding environment. The complete cycle of collection, processing, and delivery of pertinent information underground can take under an hour. During sinking, capturing data as a live stream measurement and being able to assess the alignment of the shaft liner can be critical to meeting rigid design tolerances. As sinking progresses, small changes in alignment or liner deviations can be captured and immediately corrected. Likewise, post-construction as-built conditions can be recorded and digitized, which will allow the mine personnel to compare the proper working condition to the actual condition years later. Observed changes can be identified and planned as future shaft repair works. This methodology has been developed and successfully deployed during the on-going sinking works of the two shafts at the Jansen Potash Project in south-central Saskatchewan and is described in greater detail in this paper.INTRODUCTION Light Detection and Ranging (or LiDAR) scans of the BHP Jansen Production and Service shafts during construction identified sections of both shafts where the internal radius of the temporary primary liner was insufficient to accommodate the tolerances of the permanent liner that was to be installed inside the temporary liner. These locations are referred to as “tights”. The “Tights Removal Program” was designed to collect high resolution point clouds of the shaft, using stringent survey control, that could be compared to the design profile to generate a heat map of locations for removal of up to 75 mm of steel-fiber-reinforced, 70 MPa concrete liner. This work was all on critical path, which made it valuable to save time on the schedule. Because concrete removal was a time-intensive task, it was essential to locate and remove only the concrete that would encroach on the planned permanent liner, while attempting to maximize the amount of cutting time. Removal was carried by a road header attached to a Brokk(R) 160, a small multi-attachment demolition machine."

Jan 1, 2019