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By Yuting Xue, Alper Kirmaci, Taghi Sherizadeh, Khaled Mohamed

Resin-grouted bolts serve as a crucial means of stabilizing yielded coal ribs in underground coal mines. A comprehensive investigation into their efficacy was undertaken by a collaborative effort between the National Institute for Occupational Safety and Health (NIOSH) and Missouri University of Science and Technology (MST). This study involved pull-out tests in multiple locations, including six coal mines and the NIOSH research mine. A total of seventy-three (73) tests were conducted, of wide range of anchorage lengths, ranging from a short encapsulation length of 0.305 m to a fully grouted encapsulation length of 1.524 m. The test findings indicate that when short encapsulation bolts are installed at high rotation speeds, their anchorage capacity is significantly reduced, leading to failure at the bolt-grout interface. Conversely, when these bolts are installed at lower rotation speeds, they exhibit greater capacity, with failure occurring at a higher anchorage load equivalent to the yield load of steel rebar. No matter what the rotational speeds were used during bolt installation in this study, the fully grouted bolts consistently experienced failure at the ultimate load of the steel rebar. Most of the tests carried out on partially grouted bolts with anchorage lengths of 0.610 - 0.914 m have shown behavior patterns like the fully grouted bolts, although exhibiting reduced stiffness. The outcomes of this research offer a profound insight into the ways in which resin-grouted bolts enhance the stability of coal mine ribs.

Feb 1, 2024

By Peter Dietrich, Joseph DeMello, Norbert Fuegenschuh, Kerwin Hirro, Jeff Brandt, Mike Cole

This paper presents a successful case history of the ground improvement efforts and excavation of twenty-three cross passages between twin bore tunnels driven by EPB tunneling machines in Los Angeles, California on Section 1 of the Westside Subway Extension. Unique and complicated ground conditions local to the tunnel alignment include San Pedro sands, siltstone/claystone Fernando Formation, and zones of “asphalt impacted soils.” To provide water cut-off and soil stabilization, jet grouting was performed prior to TBM excavation at the location of many of the cross passages. However, upon investigating the cross passages prior to excavation, the subsurface conditions required additional measures and SEM tools to ensure successful completion of the project.

Jun 13, 2023

By Todd Schrauf, James Scott, Mark Smith

"Cyanide heap leaching of gold ores in areas with extremely low winter temperatures requires special considerations to prevent freezing of the leach solution. Factors that impact the solution temperature include ore temperature at the time of stacking and during operation, burial of drip irrigation lines, use of geomembrane covers and heating of the leach solution. Thermodynamic modeling was performed to simulate expected ore and solution temperatures under different operating strategies for Kaminak Gold’s Coffee gold project in the Yukon Territory. Mean monthly temperatures at the site ranged from a low of -22.5 °C (-8.5 °F) to a high of 13.6 °C (56.4 °F), while in situ ore temperatures ranged from -0.5° to about -1.5 °C (31 ° to 29 °F). The modeling results were used to optimize the operational parameters and indicated that a combination of drip line burial and heating of the leach solution during the winter months was required to maintain solution temperatures above freezing during the initial years of stacking, although as the size of the heap increased, heating was no longer necessary.Modeling objectivesThe successful operation of a cyanide heap leach under extremely cold winter temperatures requires the implementation of operational strategies to prevent freezing of the leach solution and the ore within the heap. Thermodynamic modeling of the heap provides the means to quantify the effectiveness of these different operational parameters on maintaining the required operating temperatures to avoid freezing within the heap. The operational parameters that were evaluated with the model included:"

Apr 1, 2016

By Tuanhui Wang, Qiwei Wang, Quanrui Liu, Jianhui Xu, Chao Wang, Yu Liu, Yuefeng Li

Rockburst is a highly destructive geological hazard that can cause casualties and equipment damage. To achieve highaccuracy discrimination of rockburst intensity, this article proposes an improved model that addresses the inefficient maximum membership principle used in traditional rockburst fuzzy evaluation models. The stress coefficient σθ/σc, brittleness coefficient σc/σt, and elastic deformation energy index Wet are selected as evaluation indicators for rockburst classification. Subjective and objective weights are obtained using the Delphi method and entropy weight method (EWM). Three types of membership function distribution forms are then used to obtain the membership degrees of each indicator to rockburst grades: trapezoidal membership function (TMF), normal membership function (NMF), and quadratic parabolic membership function (QPMF). Finally, six traditional models and six improved models are established using the maximum membership principle (MMP) and weighted average-maximum membership principle combination evaluation principle (WMP), respectively. Based on the analysis of 100 sets of rockburst field data, the accuracy, precision, recall, and F1-score of the improved evaluation model are increased by 11.3%, 0.097, 0.068, and 0.089, respectively, compared to the traditional model. The Delphi-NMF-WMP model is selected as the best model, with four performance indices reaching 97.0%, 0.979, 0.979, and 0.978. The best model is applied to evaluate the rockburst intensity of the Cangling Tunnel, Dongguashan Copper Mine, and Jiangbian Hydropower Station Diversion Tunnel, with evaluation results consistent with the actual situation, demonstrating the reliability and scientificity of the model.

Feb 28, 2024

By Donald J. Olson

The North 27th St. ISS Extension tunnel will, under present plans, be the last constructed section of Milwaukee Metropolitan Sewerage District?s (MMSD?s) existing deep tunnel system. The 6.5 m (21 ft) finished diameter tunnel is approximately 3,260 m (10,590 ft) long and is located in NE Milwaukee County. When disputes over the pro-cesses to be used in owner-directed pre-excavation grouting in rock threatened the completion date stipulated between MMSD and the State of Wisconsin, the MMSD and J.F. Shea, the contractor, entered into a unique agreement. Shea accepted responsibility for all shaft and tunnel grouting and water control during the project in exchange for settlement of claims related to grout quantities and perceived delays. This significantly reduced risk for the MMSD and helped ensure the stipulated completion of the project.

By Enrique Rubio Esquivel, Matías Fuentes Bustamante

The transition from open pit to underground mining represents a key strategic challenge in modern mine planning. This paper presents a multicriteria and multivariable methodology to plan such a transition, integrating technical, economic, environmental, and social considerations. The proposed framework focuses on risk reduction (de-risking) through the identification of alternative development paths, the use of stochastic simulation to model geological and technical uncertainty, and different mining strategies such as methods, production rates, sequence, etc. for ultimate underground implementation. The study summarizes the limitations of traditional planning methods—which usually treat the open pit and underground mine designs as independent processes—, also often it considers a single mining method and production rate for the underground option. Instead it is proposed an integrated approach that leverages synergies between both mining methods and scalable production rates. Also the proposed methodology incorporates the definition of critical variables (geotechnical, economic, and social, among others), the construction of multiple operational and technological transition paths, and the evaluation of each path under criteria of economic attractiveness and practical do-ability (capacity to be executed). Using simulation tools (SIMPLAN for operational performance and SIMVAL for economic evaluation), probabilistic distributions of the different path are obtained, enabling the quantification of the project’s Value at Risk (VaR). A subsequent multicriteria analysis weights the expected profitability against the feasibility of execution of each alternative, producing a decision matrix that provides a framework for evaluating the different project path. As a result, the proposed approach identifies OP→UG transition strategies that maximize business value by capturing remaining resources while minimizing financial and operational risks. Finally, strategic conclusions and recommendations for the industry are provided, emphasizing the importance of early transition planning even challenging the open pit sequencing of the latest push backs by introducing early underground operations. Future work includes strengthening the methodology—such as integrating real-time analysis and adaptive decision-making—and providing recommendations for its application in various mining operations. In summary, this paper delivers a technical and professional framework to guide mining companies on when and how to carry out a successful transition from open pit to underground mining, balancing resource recovery with financial, operational, and social security.

Feb 22, 2026

By Yuting Xue, Alper Kirmaci, Taghi Sherizadeh, Dogukan Guner, Khaled Mohamed

Rib brows present a significant safety hazard in underground coal mines in the United States. To address this issue, researchers at the National Institute for Occupational Safety and Health (NIOSH) and Missouri University of Science and Technology (MST) are developing a practical tool to assess both the potential of rib brow formation and the stability of any formed brows. As part of this effort, a monitoring study was conducted to assess the potential for rib brow formation in coal pillar ribs. This study was conducted in a room-and-pillar coal mine where coal pillar ribs are prone to developing rib brows. Although no rib brows formed in the instrumented pillar, data from monitoring and visual observations provided valuable insights into the loading mechanisms impacting the instrumented pillar. These findings helped identify factors that may reduce rib brow formation, including the cavability of the roof in mined areas, the applied rib support, the strength of rock partings, and the overall integrity of the coal seam. The scientific findings published in the case study aid in assessing the potential of brow formation, offering additional evidence for the need to improve rib control methods in underground coal mines.

Feb 1, 2025

By Laura Suarez, Jörgen Kajberg, Pär Jonsén

In recent years, slag, a residue from pyrometallurgical processes, has become more attractive in circular economy frameworks to increase the efficient use of resources throughout the life cycle of steel products and help in the reduction of carbon emissions. Its applicability is strongly dependent on the particle size, and therefore, the optimization of breaking processes should be approached by increasing the knowledge of the dynamics of slag to promote fracture. Increasing the knowledge on themechanical response ofmanganese slag opens up the potential for the development of cost-effective numerical models, e.g., constitutive models based on inverse engineering calibration frameworks or digital twins. In this study, rate-dependent tests of manganese slag have been performed using a split Hopkinson pressure bar device for testing its dynamic mechanical response. In order to obtain information about the crack initiation and fracture process, 2D ultra-high speed imaging was implemented with a sampling frequency of 663,200 fps for diametrically loaded specimens. Full-field deformation measurements using digital image correlation (DIC) techniques showed a staggered fracture process where failure points on mechanical response curves vary due to the internal events happening in the material. Localized frictional occurrences and inertial effects acting inside the pre-cracked matrix have a strong effect on the global mechanical response, and therefore, a great variability of strengths was obtained.

Nov 3, 2023

By David Mast, Irwan Halim, Seung Han Kim

Nowadays more infrastructure tunnel projects are procured using design-build method. In this environment, the Owner’s engineer would typically provide performance requirements for the design-builder, and the Contractor’s designer would work with the contractor to design the tunnel lining based on the Contractor’s means and methods and manufacturing process. This paper will describe the typical requirements provided by the Owner based on its design objectives, and the means and methods by the Contractor that would significantly impact the design. Project examples and recommendations for Owner’s requirements will be provided that can optimize the design and still achieve the Owner’s performance objectives.

Jun 13, 2021

By V. Rajagopal

Corrosion and abrasion properties of a series of chromium-containing cast iron balls with Cr contents ranging from 0 to 29% was evaluated and compared with austenitic stainless steel and mild steel balls. Marked ball wear tests were performed on artificial ore samples consisting of 95% quartzite with either 5% pyrrhotite or 5% chalcopyrite under a nitrogen or oxygen atmosphere. The electrochemical mechanism was investigated by correlating the corrosive wear with the corrosion currents obtained from potentiodynamic polarization curves under abrasion. An offset in their electrochemical activities was observed somewhere between 16 and 26% Cr. In fact, 26 and 29% Cr cast irons showed an excellent corrosion resistance approaching that of austenitic stainless steel. Flotation recoveries were estimated on a 95% quartzite + 5% pyrrhotite sample ground with various cast iron ball materials under an oxygen or nitrogen atmosphere. Electrochemical results are found to be in good agreement with corrosive wear obtained from marked ball wear test and with flotation results.

Jan 1, 1991

By Joel L. Morrison

The preparation of coal-water slurry fuel (CWSF) has the potential to be a commercially viable technology for the coal industry. The technology base required to prepare stable CWSF using grinding circuits has been developed over the past decade and is now being applied to the preparation of CWSF from wet coal fines which are generated during coal beneficiation. When preparing CWSF, the optimum CWSF formulation must be determined to ensure that the fuel will be stable while having acceptable atomization and combustion properties, and the production run must be monitored closely to ensure that the CWSF quality is maintained. This paper describes the CWSF formulation process, CWSF preparation circuits, and some of typical problems encountered in, and solutions to, the transportation and storage of CWSF.

Jan 1, 1993

By Ronald C. W. Webber‑Youngman, Philani Larrance Ngwenyama

Entrapments are a huge risk in underground mines. This happens when miners (or any other persons who have entered underground) survive the initial event of an accident, become trapped or lost in unknown and life-threatening locations after evacuation, and remain unaccounted for. At this point, every second counts, and emergency response is highly desired for any chances of saving survivors. The survival chances of the missing persons depend on how quickly they can be located. Rescue teams are often deployed to search for the missing persons underground. However, the rescue teams are forced to search in random and presumed areas of the mine. This is due to the unavailability of information pertaining to the whereabouts of the missing persons. Not only the provision of accurate locations, but various other types of information such as post-accident two-way communication can enhance the survival chances of the missing persons. This information can be provided by a fit-for-purpose missing person locator system. A wide variety of missing person locator systems are already commercially available, some are in testing phases and others in prototype and development phases. This includes tracking, tracing, location detectors and post-accident two-way communication systems. These systems have unique functionalities, capabilities and limitations; making it difficult for mines to select the most effective, applicable and suitable system specific to their mine. In this study, the user requirements for a fit-for-purpose missing person locator system were developed. The purpose of the user requirements was to provide a guideline to facilitate the system selection process. The user requirements can also be used as a tool to measure and evaluate the performance of the selected missing person locator system. The user requirements were also used to predict the success of the selected system under different missing person incident scenarios. The development of the user requirements showed a potential for many other benefits for missing person locator systems.

Nov 2, 2023

By J. Harrison Daniel

Were the legislators and politicians responsible for the closing of the U.S. Department of the Interior?s Bureau of Mines (Bureau) in March 1996 fully aware of what they were doing? Throughout the United States? history, the domestic mining and minerals industry has been largely responsible for the nation?s growth and prosperity that had made it a world leader. The mining and minerals industry made it possible for the young nation to catch up with Europe during the Industrial Revolution, played an essential role leading to victories in World Wars I and II and was a core ingredient for continued economic growth. For a number of decades, America?s import dependency on non-fuel mineral materials has continued to increase. (USGS Mineral Commodity Summaries). Developing domestic resources to meet current and future demands ? particularly those resources considered to be of strategic and critical value to national security ? is necessary. Federal involvement is required since many of these resources are located on public lands. Another reason for federal involvement is that the success of the industry depends on long-range research programs and advances that may take up to 25 years to become commercially available. This situation requires federal partnership to coordinate the programs necessary to collectively involve the industry, individual mining companies and colleges and universities. So, how was it possible to close a federal agency that had contributed so much to the nation?s welfare in a mandated 90-day period, with more than 1,200 employees losing their jobs?

Jan 4, 2010

Once every three years the eyes of the construction and mining industry?s turn to Munich, Germany for the bauma trade fair and exhibition. From April 19-25, Messe München International (MMI) will host the 29th edition of this massive show that, despite the recent recession and global financial struggles, has grown yet again. The show, which is completely booked, will take place on a record 555,000 m2 (5.9 million sq ft) of indoor and outdoor exhibition space at the New Munich Trade Fair Centre. More than 3,000 exhibitors are expected to make use of this event. To prepare for the show that highlights some of the largest and most impressive construction and mining equipment in the world, Messe München began working months in advance on getting the infrastructure on the open-air site ready, in time for the arrival of the gigantic machinery exhibits, which started to arrive in March. Part of the preparations include a new entrance at the northwest corner of the exhibition center that was built to regulate visitor flow better. This should help with bauma considering that in 2007 more than 500,000 visitors passed through the gates. ?Although in 2010 the construction machinery sector in many markets worldwide will be recovering only slowly from the recession, we are pleased to report that we are seeing strong demand for exhibition space. This shows that exhibitors regard participation in the world?s leading trade fair bauma as a must, although many are at present having to make cuts in their advertising and trade-fair budgets. We have been particularly surprised by the strong demand for space from exhibitors from markets like China, India and Turkey. The fair is fully booked and many more companies are on the waiting list,? said Eugen Egetenmeir, managing director of Messe München. More than 50 percent of the exhibitors at bauma 2010 come from countries outside of Germany. While the show?s primary focus is on the construction section, it is not as if the mining sector will be difficult to find. With some of the largest equipment in world on display in section C2 (Fig. 1), the mining industry is sure to be well-represented.

Jan 4, 2010

By Hyung-woo Kim, Sup Hong, Sung-Soo Kim, Chang-Ho Lee

A deep-seabed integrated mining system, which consists of four subsystems such as riser pipe, buffer, flexible riser, and tracked vehicles, is presented in Figure 1. In order to collect more manganese nodules, multiple tracked vehicle systems should be used in a deep-seabed integrated mining system.

Sep 1, 2014

The Río Agrio of northern Patagonia, Argentina, is highly acidic due to inputs of volcanic gases (SO2, HCl, HF) in its headwaters. The watershed includes a hyper-acidic (pH <0.5) volcanic crater lake, a larger glacially carved lake that is also strongly acidic (pH 2.6 to 2.7) and an acidic river that flows for more than 40 km (25 miles) before its pH is completely neutralized. This unique watershed has many geochemical and biological similarities to acid waters caused by mining. This paper describes the Río Agrio watershed and draws a comparison with some famous acid mine waters. Learning more about naturally acidic lakes and river systems could have important applications to the bioleaching of ores or biological treatment of mine waters. Therefore, it should be of interest to the general community of mining and metallurgical engineers.

Jan 1, 2008

By David Hanson, Sean Warren, Chaparral Berry

"Coal bumps, also referred to as dynamic failure events or coal bursts (Lawson, Weakley, and Miller, 2016), continue to be a hazard in underground coal mines. While current design methods have significantly reduced the occurrence of coal bumps, they have not been completely eliminated. This paper investigates a correlation between coal compositional components, coal molecular structure, and probability of coal bumps in an effort to deepen understanding of coal behavior in an effort to reduce hazards in underground coal mines.Samples from the Penn State Office of Coal (PSOC) Department of Energy Coal Samples (DECS) were obtained for Fourier Transform Infrared Spectroscopy (FTIR) analysis using the KBr pellet method. Peaks indicative of the coal molecular structures were obtained using spectral integration software. These data, combined with published elemental data, were compared to historic bump occurrence in order to establish a possible correlation. Finally, results based on multivariate analysis of the elemental and FTIR data with bump status as the dependent variable suggest that elemental sulfur and molecular structure can be used as an indicator of bump susceptibility within the sample set considered.INTRODUCTIONThe study of coal requires consideration of multiple variables: percentages of organic and inorganic components, organic component origins, coal age, pore structure, cleat density, elemental composition, etc. Examining coal in situ increases the number of variables, such as coal depth, seam thickness, surrounding stratigraphy, and so forth. This collection of variables influences the subsequent behavior of coal simultaneously, and weighing their relative impact is a challenge for researchers. “A problem never exists in isolation; it is surrounded by other problems in space and time” (Ackoff, 1956). Having a substance such as coal that we know so much about, and yet so little, we have to ask what can be learned.An experimental study using Fourier Transform Infrared Spectroscopy (FTIR) was undertaken to determine if the chemical structure of coal contains information which may lead to a better understanding of triggers or attributes which may, in turn, lead to an increased probability of a dynamic failure event. While a full analysis of the factors driving dynamic failure are beyond the scope of this study, it is possible that a better understanding of the chemical structure of coal will lead to an increased knowledge of its inherent behavior, including its propensity to burst."

Jan 1, 2019

By M. Westendorf, T. Banerjee, S. Kaushik, D. Tinney

"Cyclones are one of the most extensively used pieces of equipment within the mineral processing industry because of their simplistic operating and maintenance philosophies. They are commonly used as classifiers within the comminution circuit to control the grinding product particle size for satisfactory performance of downstream operations.Cyclones are a key contributor to the effective operation of the plant and have a significant impact on the mineral processing plant operations. If the cyclones are not performing as they should, the results are often a combination of lost recovery, grade, capacity and reduced throughput. Similarly, an inefficient cyclone operation may also lead to low or high recirculating loads that impact the efficiency of the comminution circuit. This highlights the importance of having proper stability in cyclone operation while implementing any plant-wide optimization strategy.One of the key challenges in cyclone operation is that cyclones are highly sensitive to changes in operating conditions and are affected by process fluctuations such as feed pressure, solids concentration and flow rates. Fluctuations in cyclone feed characteristics lead to unstable cyclone performance which affects mineral liberation. For such an impactful unit operation, cyclones have historically been under-instrumented in an otherwise highly instrumented process plant. Traditionally, mill operators have relied on visual observations of the apex discharge to determine the operating state of the cyclones. Visual cues corresponding to the different cyclone operating conditions have been discussed by Neesse et al. (2004) as shown in Fig. 1."

Jan 1, 2014

By J. G. Pippenger

Rio Tinto Coal Australia (RTCA) developed the Meandu Mine in Queensland, Australia in 1983 to supply thermal coal to the adjacent and newly constructed Tarong Power Station (TPS). In designing the mine, RTCA selected Meandu?s best economic reserves for a 27-year life based on station owner Tarong Energy Corp.?s (TECs) estimated life for TPS. That 27-year plan changed dramatically in the early 2000s when TEC approved life extensions to TPS?s four existing units plus construction of a fifth unit. After reviewing Meandu?s remaining reserves, RTCA decided the nearby Kunioon reserve offered the more economic option for maintaining deliveries beyond 2010. Those plans changed again in 2007 when TEC chose to purchase the Meandu Mine and nearby reserves. TEC then selected Thiess Pty Ltd. (Thiess) to continue operating Meandu until the new mine at Kunioon could be developed. After assuming operation of the mine in 2008, Thiess began a review of Meandu?s remaining reserves and found considerable coal available with economic potential. Working jointly with TEC, Thiess performed several analyses on Meandu and subsequently the Kunioon coal reserves. The results changed TEC?s decision from expediting Kunioon?s construction to instead continuing Meandu?s operation for up to 15 additional years.

Jan 1, 2011

By Werner Burger

The Hallandsås project with a long history, first started in 1991, is well known in the tunneling community. In the past it has been stopped twice for technical and environmental reasons. The third attempt started in 2004 using a dual mode rock TBM. The heterogeneous highly fractured and abrasive rock mass as well as large areas of water bearing zones present most difficult subsurface conditions. The tunneling concept is based on the use of watertight segmental lining and a TBM able to operate in open mode, possibilities for extensive pre excavation grouting and high pressure closed mode operation up to 13 bar to cover exceptional conditions.