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By B. Slaker, M. M. Sears, G. Rashed

Ground falls represent a significant hazard at underground mines in the stone, sand and gravel (SSG) sector in the United States. Researchers from the U.S. National Institute for Occupational Safety and Health (NIOSH) are conducting detailed investigations into the complex loading conditions at underground stone mines operating in challenging conditions. This paper presents the application of numerical modeling to analyze pillar and roof stability at a dipping underground limestone mine.

By Bülent Erdem, Zekeriya Duran, Tuğba Doğan

The objective of this study was to evaluate the potential health risk associated with exposure of dozer operators to whole-body vibration. Measurements were made on 31 dozers used in different surface mines in Turkey. Predictions of adverse health effects of vibration were based on the standards BS 6841:1987, ISO 2631–1:1997, ISO 2631–5:2004, and the EU Vibration Directive:2002. Operators experienced high and comparable levels of vibration acceleration and dose during all dozer tasks: pushing the material (DOZE), moving forward (FORWARD), moving backward (REVERSE), and ripping (RIP). Specifically, DOZE, FORWARD, REVERSE, and RIP showed high potential of adverse health effects in terms of vibration dose according to the worst-case axis and vector sum criteria and a moderate adverse health effect for acceleration according to the worst-case axis criterion. Operators of large dozers were exposed to lower levels of vibration. However, no statistically significant relationship between vibration exposure levels and the propelling mechanism and the service time of dozers, operator experience, operator age, and ground type was found.

Jun 16, 2022

By Madan M. Singh

This section is unique to the Handbook in that it is the only section that deals with underground excavations for nonmining purposes. The editors were of the opinion that the section should be incorporated because the subject matter covered by the chapters is closely related to mining, and many mining engineers are currently involved in these activities. As we enter the decade of the 1990s activities in this category will increase, enhancing the relevance and utility of the material discussed. As the population increases, especially in metropolitan areas, the necessity to go underground will be greater. At the present time, not only are subsurface shopping malls and pedways connecting buildings becoming commonplace, but structures as diverse as the Civil and Mining Engineering Building on the University of Minnesota campus, a road-and-fleet maintenance facility in Multnomah County, OR, and even an ice cream parlor (Dairy Queen) in northern Wisconsin have been constructed underground. Placing utilities below the surface has numerous advantages and is now customary. Rapid transit and highways through tunnels in urban areas have been the norm for many years, but subterranean stormwater reservoirs, power plants, industrial warehouses, and food storage silos are relatively new innovations. The philosophy of underground defense installations is ancient, but their requirements and designs have trans-formed radically as technology advances. The use of under-ground space for disposition of wastes is modern, since it is recently that environmental concerns and waste disposal costs have assumed increased significance.

Jan 1, 2008

By Ping Zhang, Xu Ma

Perturbations from mining operations significantly affect the stability of rock masses, especially with the increase in mining depths. This study uses the discrete element method (DEM) to investigate shear slip failure along discontinuities in an underground mine, aiming to quantify seismic moment and seismic energy to better understand seismic hazards.

May 1, 2023

By E. C. Westman, W. R. Thomas, W. J. Conrad, A. J. R. Russell

"Understanding ground control problems continues to remain a focus of the mining engineering community. To aid mine operators and engineers in identifying and responding to ground control issues, the Ground Observation System (GOS) is being developed. The GOS is an integrated, web-based graphical user interface that displays ground response data collected wirelessly from an underground mine. It presents data in an intuitive manner to assist mine personnel, who are on- or off-site, in quickly identifying hazardous areas. Geotechnical instrumentation will be connected to wireless transmitters that will relay data in real-time to a surface computer that stores the information in a database. The GOS website will then display the geotechnical data in graphical and tabular forms, as well as in conditionally formatted mine maps. Data from each measurement device will be able to be viewed in its entirety or within a time interval, and can be downloaded for further analysis. The ability of the GOS to quickly interpret and communicate mine hazards to personnel of varying technical ability should prove to be a useful tool in understanding ground control and thus improving mine safety.INTRODUCTION Computer-based data information centers that convey operating parameters and conditions are prevalent in modern underground mines. Today’s systems are popular in showing ventilation controls and monitoring equipment performance (Jyothi & Meena 2013). In ground control monitoring, Conover, Ross, and Bigby, 2010 have installed a wired telltale roof monitoring system that sends roof displacement data every ten minutes to a computer on the surface. The computer receives, stores, and displays the data in real time. Data can also be viewed remotely through a password protected internet connection. Additionally, an internet connection allowed for remote updates to the system which streamlined software development and maintenance by eliminating travel (Conover et al., 2010). Currently, no such system beyond Conover et al.’s design has been accomplished. The Ground Observation System (GOS) is being developed to fill the void of real-time geotechnical monitoring in underground mines. A wide array of data will be transmitted wirelessly and broadcasted to on- and off-site mine personnel through the internet. The GOS will incorporate geotechnical data from roof deformation, borehole scratch testing, photogrammetry, and seismic monitoring into one interface, all while achieving permissibility for the use in gaseous mines. As a result, a comprehensive view of rock movement due to mining will be available. The overall purpose of the GOS is to deliver warnings; to ensure reliable data is relayed to personnel for the identification of potential ground failures, provide mine engineers information to design more stable mines, and assist with further geotechnical research."

Jan 1, 2015

By B. DANIEL MARJAVAARA, I. A. SOFIA LARSSON, ANNA-LENA LJUNG

One way to upgrade iron ore is to process it into pellets. The pelletizing process is multifaceted, involving complex fluid dynamics with highly turbulent, high-temperature flow in intricate geometries. This makes it hard to perform measurements during operation, so a useful tool for better process understanding is computational fluid dynamics (CFD), where the challenge is to perform efficient and trustful simulations of complicated problems. A validated simulation model can be valuable for increased process control and development. In this paper, the flow field and coal combustion process in a pilot-scale iron-ore pelletizing kiln is simulated using a CFD model. The objective of this work is to apply a coal combustion model to enable an investigation of thermal effects from the flame on the surrounding flow field.

By Tim M. Benson, Adam L. Lamanna, Carolina Martinez-Gutierrez, Mark J. Stephani

The Lower Concourse C Extension (LCE) 108-in Storm Sewer consists of a 2,797-foot long, 27 to 55-foot deep, 108-in I.D. storm sewer tunnel. Situated beneath active taxiways and a terminal apron at Hare International Airport (D), the tunnel diverts ows from existing storm sewers located within the footprint of a future satellite concourse. The project was delivered via Construction Manager at Risk (CMAR) as part of Chicago Department of Aviation’s (CDA) ongoing O’Hare 21 Capital Program. This paper presents project details, multiple stakeholder coordination, subsurface risks and challenges, TBM performance, and impacts to existing infrastructure.

Jun 23, 2024

By Simon Strong, Tim Brown, Luis Ignacio Sanz Vivanco

"One of the most significant technical and practical challenges facing the tunnel construction team on the Legacy Way road tunnel project in Brisbane, Australia was how to erect the pre-stressed precast concrete slabs to form the smoke duct in the tunnel boring machine (TBM) tunnels. An essential part of the tunnel ventilation system, the smoke duct, extends the full length of the 4.6km long twin, two lane tunnels. The vast majority of the tunnels (approx. 4.3km) were constructed using two 12.4m diameter double shield TBMs. The refurbished Herrenknecht machines broke several world records on the way to completing the tunnel excavation works in just over nine months. With the excavation complete the focus turned to solving the complex civil tunnel fit out challenges. A key component of the civil fit out of the tunnels was constructing the smoke duct in the TBM tunnels which was designed as a precast solution. The slabs which each measure 8.62m long by 2.0m wide by 200mm thick and weigh close to 9 tonne need to be erected above cast in situ corbels whilst other tunnel finishing works continue. The space proofing clearance offered by the design to the support corbels below and the precast segmental lining above was in the order of only 100mm. This paper details the events of how the Transcity JV tunnel fit out team, comprising some of Europe and Australia’s leading tunnel construction specialists, drew upon the global strengths of the existing JV member companies and the global reach of leading TBM manufacturer Herrenknecht to develop an innovative system to solve this challenging problem. This globetrotting story, which starts in Australia, visits Europe and mainland China before returning to Brisbane where it all began."

Jan 1, 2016

By Kai Koosmen, Mehdi Serati, Tengzhou Wang

Spalling and rockburst are unwanted brittle failures at the boundaries of underground excavations that are commonly observed in hard rock and high-stress environments at significant depths, although, spalling has also been observed in comparatively shallow soft rocks. The crack initiation (CI) stress threshold (representing the stress level at which new micro cracks begin to form in an intact rock) is widely used to establish the in-situ spalling strength, and is generally regarded as the lower limit of the long-term rock strength. This study analyses the evolution of CI and other mechanical properties for a high-porosity sandstone with an average UCS of 38 MPa under unconfined cyclic compressive loading. The results indicate that rock properties are variably affected by cyclic loading with; no significant effect on Youngs Modulus; a moderate increase in Poisson’s ratio and fracture angle; a moderate decrease in UCS; and a major reduction in the CI stress threshold. All of these changes were generally amplified by cyclic loading at higher stresses. From the results, it is concluded that rockburst and spalling limit in underground structures may reduce over time if the rock is subject to repetitive cyclic loading, and that the reductions will be greater for higher cyclic stresses. This may be a significant factor in the design and operation of some deep underground structures.

Apr 26, 2022

By Peter Amelunxen, Brandon Akerstrom

Since its introduction 40 years ago, the compartmental model of flotation has been used to predict the performance of mechanical flotation cells. However, it has found limited success for modeling dual-chamber machines and, as a result, engineers have adopted empirical correction factors usually derived from field audits of industrial cells to predict the performance of dual-chamber flotation cells. This paper introduces an extension of the compartmental model that applies to both single- and dual-chamber cells. The model is tested against pilot test work performed at Capstone’s Pinto Valley concentrator, and then used to evaluate the key operating and design parameters of dual chamber flotation cells. The results suggest that the design of the mixing chamber — for example, whether it is pneumatic or mechanically agitated — is not a significant contributor to overall machine performance. The work also suggests that the highest recoveries are achieved when the froth recovery is high, and longer separation chamber residence times and/or higher internal circulating loads are only beneficial when the froth recovery is low. Lastly, the results show that the single most important driver of the machine performance is the froth recovery of the separation chamber.

Mar 1, 2025

By Shi Wang, Hongbin Liu, Meiliang Wei, Wu Liu, Xiaojun Wang, Yuxian Ke, Xuepeng Song, Tiejun Tao

The study investigates the influence of water migration on the fluidity of fresh cemented paste backfill (CPB) with and without flocculant under variable shear rates. The research utilizes nuclear magnetic resonance (NMR), rheological tests, and scanning electron microscopy (SEM) to analyze water migration, rheological properties, and microstructure evolution. The findings reveal that water migrates to more stable states as shear rate increases, and the addition of flocculant enhances water migration and increases shear stress and apparent viscosity. The study establishes relationships between water content and rheological parameters, providing insights into the flow characteristics of fresh CPB for pipeline transportation.

May 4, 2022

By Donald W. Gentry

This paper presents some of the results of a rock mechanics in¬strumentation program designed for, and implemented at, longwall panel 4N at the York Canyon Mine near Raton, New Mexico. The objective of this particular instrumentation program was to determine the response of the rock mass to longwall mining of a thick coal seam utilizing shield-type supports. Measurements were made in the rock along the ground surface, above the coal seam, in the coal seam and immediately below the coal seam. Longwall test panel 411 had a total developed length of 762 m (2500 ft) and a face width of 168 m (550 ft). The seam mining height in the panel area was approximately 3 m (10 ft). The average depth of overburden above the panel is 107 m (350 ft) al¬though it ranges from 73-134 m (240 - 440 ft). Roof support at the face was provided by Hemscheidt shields. These shield-type supports weigh 11.4 metric tons each.

Jan 1, 1977

By Laura Suarez, Jörgen Kajberg, Pär Jonsén

How does an investigation into the breakage characterization of electric arc furnace (EAF) manganese slags contribute to a more responsible usage of resources throughout the life cycle of steel products and reduction of carbon emissions? The main goal of this study is to increase the knowledge on the mechanical response of manganese slag to open the potential of pyrometallurgical residues to become secondary material in industrial applications such as infrastructure construction, fillers, binders and soil stabilization, among others.

Mar 1, 2024

By Sandy Worden

Coal mining companies in Australia are managing the high-consequence risks across their operations more effectively by using an interactive online risk management system known as Riskgate Developed by the Minerals Industry Safety and Health Centre (MISHC) at the University of Queensland, Australia, Riskgate contains detailed information about 11 high-consequence risk areas (called topics in the system) for opencut and underground coal mines (Table 1). The existing topics are: fires; strata control for underground mining; ground control for opencut mining; tires; isolation; collisions; explosions and explosives; manual tasks; and trips, slips and falls. Every Riskgate topic is focused on coal industry activities (mining, processing, transport and storage). The scope includes mine sites, lease areas and mine infrastructure (mobile, fixed plant, field equipment, buildings, road and rail transport), and all aspects of the mine life cycle from design through to decommissioning. The topics uniformly recognize that a loss of control can result in injury or fatality, equipment damage, production loss, reputation loss and environmental damage. However, the priority focus for Riskgate is the safety of mine personnel.

Jul 1, 2013

By Xuehui Li, Xinshuai Shi, Jun Wang, Jianguo Ning, Shang Yang, Zhaohui Zhang

Pressure relief is an important step in preventing and controlling rock burst disasters. Hydraulic slotting has emerged as a strategy for pressure relief and energy release in roadway surrounding rock. There is no qualitative description for the response relationship between hydraulic slotting parameters and the degree of pressure and energy release in a roadway, which is a scientific problem. In this paper, theoretical analysis, numerical simulation, and on-site industrial practice were comprehensively used. First, a structural model for the pressure relief and energy release of coal by hydraulic slotting in a deep roadway was established, and the pressure relief and energy release principle by hydraulic slotting was revealed. The principles and methods for determining hydraulic slotting parameters in the roadway were proposed. Three evaluation indices for the pressure relief and energy release effect of coal after hydraulic slotting were proposed, namely, the stress ratio of coal, elastic energy density ratio of coal, and displacement rate of the roadway rib. According to the evaluation indices, the degree of pressure relief and energy release was divided into three levels: reverse pressurization, full pressure relief, and transitional pressure relief. Then, a FLAC3D numerical model was constructed, the levels of pressure relief and energy release under different hydraulic slotting parameters were analyzed, and the optimal slotting parameters were determined. Finally, on-site industrial practices were carried out in Panel 7312 of the Xinhe Coal Mine. An effect test showed that the effect of pressure relief and energy release was remarkable after hydraulic slotting was adopted on the roadway surrounding rock, which can effectively reduce the risk of rock bursts. These research results can further improve hydraulic slotting technology systems and provide a theoretical basis and technical reference for the stability control of deep roadway surrounding rock.

Sep 20, 2023

By E. Rubenstein, V. Gangrade, K. V. Raj, M. L. Harris

Underground stone mine ventilation is characterized by large openings with low resistances. These mines primarily face three challenges: moving adequate volumes of air, controlling and directing the airflow, and planning ventilation systems that work well with production requirements. Given these challenges, this paper examines the data collected by the Mine Safety and Health Administration (MSHA) to determine the extent to which respirable crystalline silica (RCS) and diesel particulate matter (DPM) are an issue in underground stone mines. Out of 522 sampled mines, there were 108 personal samples exceeding the RCS Permissible Exposure Limit (PEL) during 2000–2020. DPM were more prevalent than RCS in these mines with 382 personal samples exceeding the DPM PEL out of the 929 mines sampled during 2002–2020. Dilution of DPM is usually the defining parameter for design of mine ventilation systems in largeopening underground stone mines. With this knowledge, focused attention can be directed to these mines so that appropriate prevention and mitigation techniques can be utilized to prevent stone miners’ exposure to RCS and DPM and subsequent respiratory diseases.

Mar 2, 2022

More than 100,000 people are expected to be in Las Vegas, NV in March for ConExpo-Con/Agg 2002, the largest exhibit of its kind in the Western Hemisphere. This triennial event features equipment, services and technical sessions geared toward the global construction aggregates and ready mix concrete industries. ConExpo-Con/Agg 2002 will take place March 19-25, 2002 at the Las Vegas Convention Center. For registration information, contact the show offices, phone 800-867-6060, 414-298-4141, or 301-587-3140, Website www.conexpoconagg.com.

Jan 1, 2002

By David Crouthamel, Raymond Henn

"The need to fill the void space or annulus created between an excavated tunnel or shaft and the final lining system has long been a requirement in underground construction. Most of those types of voids are created as a result of employing the two pass tunneling lining method. Filling of this void is called backfilling. For many years the materials used as backfill were primarily reinforced and non-reinforced concrete, sanded grout, neat cement grout, or blown-in sand/pea gravel. However, in the past 20 years the use of cellular grouts/cellular concrete as the backfill material has greatly increased. Most cellular grout is made of a mixture of water, Portland cement (with or without the addition of fly ash), a foaming agent and admixtures such as a water-reducer or superplasticizer.It is the authors’ preference to use the term cellular grout as opposed to cellular concrete since by ACI Concrete Terminology an ACI Standard (ACI CT 13), concrete contains aggregates. Normally cellular grout does not contain sand (finite aggregate), but almost never contain course aggregates.The authors believe there are several reasons for this increased use of cellular grout as backfill, such as:• The increase utilization of the various trenchless tunneling methods. Tunnels constructed using trenchless method tend to be smaller in size, excavated diameter or cross sectional area. Making man-entry for placing backfill from inside the secondary liner, utilizing pre-installed grout posts, more difficult if not impossible. It is these workspace restrictions that are the drivers as to when to utilize grout ports installed during the pipe/liner fabrication versus grout delivery pipes installed within the void/annulus space.• The ability of cellular backfills to be pumped and flow longer distances.• The unit weight of cellular grouts can be controlled by mix design and generally can range from 560 Kg/m3 (35 lbs/CF) to 1040 Kg/m3 (65 lbs/CF)."

Jan 12, 2017

By FELIPE SÁNCHEZ, PHILIPP HARTLIEB

Innovation plays a critical role in the mining industry not only as a tool to improve the efficiency of its processes and to reduce costs but also to meet the increasing social and environmental concerns among communities and authorities. Technological progress has also been crucial to allow the exploitation of new deposits in more complex scenarios, such as lower ore grades, extreme weather conditions, deeper deposits, harder rock mass and high-stress environments.  

By V. Rajaram

Rock reinforcement systems are used in open pit and underground mines to stabilize the rock mass in-situ and provide safe working conditions. Significant progress has been made to date in the design and implementation of rock reinforcement systems to accommodate bad rock conditions and larger excavations. However, the rationale for the design of rock reinforcement systems remains essentially the same and can be categorized into three groups, namely 1. to create a beam of competent rock in stratified formations, 2. to resist sliding motion in jointed rock, 3. to passively support the superincumbent loads in highly stressed ground. Case histories of the rock reinforcement sys¬tems that illustrate these design approaches will be presented in this paper.

Jan 1, 1983