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By M. Raffaldi, J. Johnson, M. Stepan, D. Benton

"The Office of Mine Safety and Health Research (OMSHR), Spokane Mining Research Division (SMRD), is continuing its High-Energy High-Displacement (HEHD) testing of field-scale shotcrete panels. A test program was developed to determine the relationship between applied force, displacement, and energy for both unreinforced and reinforced shotcrete panels. Reinforcement options consisted of synthetic macro-fibers, sprayed polyurea liners, chain-link fence, welded-wire mesh, and combinations of these products. During testing, photogrammetry was used to measure the geometric changes of the panels, including volume changes and panel cracking. These measurements were correlated with the load and displacement data, allowing visual observation to be related to the applied force and displacement. The test results provide a comparison of the mechanical performance of the various panel types and can be used by the practicing engineer to evaluate installed support based on visual observation of cracking and deformation. Visual assessment of the loading cycle and strength capacity of shotcrete in underground excavations will improve mine safety by providing a means to quantify the stability of installed shotcrete support. INTRODUCTION The National Institute for Occupational Safety and Health (NIOSH), Office of Mine Safety and Health Research (OMSHR), Spokane Mining Research Division (SMRD) is continuing research on the behavior of shotcrete when used as the surface support component in mining ground support systems. Ground control safety often depends on supporting, or at least containing, the ground between the rockbolts. Shotcrete and mesh, in various combinations and with other components, are often used to accomplish this (Figure 1). Maintaining support pressure during ground deformation is key to the performance of these systems, and to ensuring miner safety. However, the toughness of a ground support system–the ability to maintain strength over large deformations–is difficult to quantify. Researchers at SMRD have responded to this deficiency by designing a full-scale test device, described previously by Martin et al. [2015a], and beginning a testing program to assess the behavior of shotcrete surface support reinforced with a variety of products including: fibers, chain-link mesh, welded-wire mesh, spray-on polyurea liners, and combinations of these products. This paper presents the findings of these tests."

Jan 1, 2016

By B. Genc, V. J. Mahadeo, S. Ramparsad4, U. Govender

The study was intent on assessing the socio-economic impact of a zinc mine in South Africa through the application of people-centric digital tools using a case study research methodology. The global mining industry is undergoing significant technological shifts to modernize, improve operational sustainability, and align with the environmental, social, and governance (ESG) agenda. While the case study mine is a more modernized mine, continuous improvement around the ‘social’ pillar becomes critical, and to this end application of people-centered digital tools presented as the vehicle to understand community needs and impacts. Despite considerable annual corporate social investment by mines annually, the overall impact or social return on investment is marginally understood. Towards contributing to addressing this gap, digital ESG ‘social-related’ data gathering tools for mines decision-making were developed, including the training-needs assessment tool, community-social needs assessment, small, micro, and medium enterprise (SMME) communications and engagement tool, digital leadership competencies gap assessment tool, and change management blueprint, which further allowed for customization to the mining context. Hence, the novelty of this paper relates to applying digital tools to provide real-time information of the needs of a community, both socially and economically. The findings suggested that these digital tools enabled gathering of information for the establishment of regional and operational baselines towards enabling of social investment returns in relation to socio-economic transformation development interventions. These tools have been applied to a zinc mine context, with lessons and experiences obtained through this study, invaluable to the application of these digital tool in other mines in South Africa. The study was conducted in September 2023 across five host communities, surrounding the zinc mine, in the Northern Cape region, with 120 participants involved in the application of three relevant community-related digital tools, which included the training needs, community-social needs, and SMME communications and engagement tools. It was evident that the digital ESG tools could be used for data gathering for the mine’s informed decision-making and allowed for securing of insights on community needs in near real-time, and further proved practical for community use.

Dec 11, 2024

By Andrea Koschinsky, Luise Heinrich, Stefan Gößling-Reisemann

"Germany, like several other countries, has entered a contract with the International Seabed Authority (ISA) to explore the prospects of commercial manganese nodule mining in the Clarion-Clipperton Zone (CCZ). Ensuring a maximally sustainable deep-sea mining operation requires a thorough understanding of the environmental impacts associated with every step of the mining process from the extraction of the nodules at the seafloor to the refinery on land. Against this background, the project presented here applies a combination of scenario-building and life cycle assessment (LCA) to assess and evaluate the sustainability performance of the individual process steps as well as the entire mining operation.Life cycle assessment (LCA) is a comprehensive methodological framework that allows the identification and quantification of impacts occurring during a products life-cycle, as well as the analysis and evaluation of their contribution to pre-defined impact categories, such as climate change, acidification and toxicity (Rebitzer et al., 2004). Until now, LCAs with a focus on raw material extraction have almost exclusively been applied to terrestrial processes. Noteworthy exceptions are offshore drilling, offshore wind farms and ocean fishing. Hence, the first part of the project is to investigate in how far LCA can be applied to deep-sea settings and if and in what way it could be adapted to be used in a deep-sea mining context."

Jan 1, 2017

By S. Iverson

Fall of ground accidents continue to be a source of injury in underground metal mines. MSHA accident statistics indicate that most rock fall accidents occur at a new face where drilling and blasting methods are used. Removing loose rock by scaling is imperative to removing the potential for rock fall injury. Detection of potentially loose rock could improve the scaling process and result in fewer rock falls. Infrared thermal imaging cameras were investigated as far back as 1966 as a tool for loose rock detection. Early on it was clear that sensitivity (e.g. detectable temperature increment) is a key factor in this application. Both pixel resolution and temperature resolution have greatly improved with modern instruments. This paper describes an evaluation of modern infrared thermal imaging camera technology to detect loose rock conditions at six underground metal mines in the western U.S. It was found that thermal images provide a high resolution visual discrimination between loose rock and intact rock. However, detecting loose rock was difficult in cases where the rock and ventilation air were at the same temperature. Loose rock was detected when rock was both warmer and cooler than the ventilation air temperature. Warm rock with cool ventilation air provided the best conditions for detection.

Feb 23, 2014

By W. R. Tyson

Imperfections such as lack-of-fusion and undercut are inevitable in field welding of pipelines. Above a certain size, such defects must be removed or repaired. In the present state of the art, determination of allowable defect size is done by Engineering Critical Assessment (ECA). This requires measurement of toughness, and comparison of toughness with crack driving force. ECA methods used in current international pipeline standards will be reviewed and compared.

Jan 1, 2010

By James P. Hambleton, Anastasia Nally

This work focuses on the numerical simulation of multi-plate anchor systems (e.g., helical anchors) in sand subjected to vertical loading. In assessing the stiffness and capacity of these multi-plate anchor systems, full awareness of the abilities and limitations of the various analysis methods must be understood. This work first summarizes studies completed by others and then goes on to assess the failure mechanisms of multi-plate anchors in sand and the influence of (1) plate width-to-depth ratio, (2) number of plates, and (3) relative positioning of plates. The analysis makes use of (1) conventional limit analysis, (2) so-called modified limit analysis that employs reduced strength parameters to account for the influence of soil dilatancy, and (3) the displacement-based finite element method, which considers elastic as well as plastic deformation leading to failure. The work critically reflects on limitations in the current analysis methods for helical ground anchors. INTRODUCTION Helical anchors are a relatively low cost foundation type, typically consisting of a steel rod and single or multiple plate attachments. In recent decades, they have seen rapid growth, and as outlined by Merifield and Sloan (2006) and Hambleton et al. (2014). Design techniques for helical anchors have previously been predominately empirical, as much of the past research in this field is experimentally based. It is common practice for helical anchors to be modeled as horizontally oriented plate anchors in both numerical and experimental analysis. This work focuses on analysis based on the finite element method, including so-called finite element limit analysis and the conventional displacement-based finite element method, with some comparisons made to experimental studies. Numerical simulation of anchor pull-out capacity in cohesionless soils is stunted by the many difficulties faced when using numerical analysis with cohesionless soils. Additional variations can be seen when comparing the serviceability based load capacities to the ultimate load. In this work, both the force-displacement response (stiffness) and the ultimate anchor capacity are assessed, with more focus on the latter. This work focuses only on analysis techniques for multi-plate anchors with vertical loading in cohesionless soils. Many studies have been completed in this area, some of which assume a rectangular plate in a plain strain model (Rowe & Davis, 1982; Merifield & Sloan, 2006; Cerfontaine et al., 2019). Whereas others use axisymmetric conditions (Baker and Kondner, 1966; Saeedy, 1987; Murray & Geddes, 1987; Ghaly & Hanna, 1994; Sakai & Tanaka, 1998; Merifield et al., 2006;) and minimal studies considered both axisymmetric and plane strain in the one study (Vesic, 1971; Tagaya et al., 1988; Murray & Geddes, 1987; Sarac, 1989).

Jan 1, 2019

By D. Stone, M. Le Roux, Q. P. Campbell, M. Fofana

Float-and-sink analysis is widely used in the coal industry to obtain washability data, yielding important information about beneficiation potential and performance. This method is associated with health and environmental problems, and research into alternative densimetric methods is important. The RhoVol is a new technology developed by De Beers Group Technology South Africa (DebTech) for the image-based generation of densimetric data from ores. The analysis is done on a per-particle basis, within a size range of +3 mm –8 mm. In this paper we compare the established methods used for the float-and-sink analysis of coal with a new method using RhoVol. The aim of the study was to determine the validity of the information obtained from the RhoVol analyser by performing comparative densimetric analysis on three different coal samples. The results showed that the RhoVol method was more rapid, safe, and precise, but tended to consistently underestimate the density of the coal sample, probably due to varying coal porosity.

Oct 3, 2023

By Bo Hyun Kim, Mark K. Larson

This study was developed as part of an effort by the National Institute for Occupational Safety and Health (NIOSH) to better understand rock-mass behavior in longwall coal mines in highly stressed, bump-prone ground. The floor-heave and nofloor- heave phenomena at a western US coal mine could not be properly simulated in numerical models using conventional shear-dominant failure criteria (i.e., Mohr–Coulomb or Hoek–Brown failure criterion). The previous numerical study demonstrated these phenomena using a user-defined model of the s-shaped brittle failure criterion in conjunction with a spalling process in the FLAC3D numerical modeling software. The results of the FLAC3D modeling agreed with the observations of the relative amounts of heave from each gate-road system. However, the FLAC3D model adopted many assumptions and simplifications that were not very realistic from a physical or mechanical perspective. To overcome the limitations of the FLAC3D model, 3DEC modeling in conjunction with the discrete fracture network (DFN) technique was performed to better understand the true behavior of floor heave associated with underground mining in an anisotropic stress field. The effect of stress rotation in the mining-induced stress field was considered by using a different geometry of rock fractures in the coal seam. The heterogeneity of the engineering properties (i.e., cohesion and tensile strength) were also considered by using Monte Carlo simulations. Consequently, the 3DEC models using the DFN technique resulted in predictions of floor heave that agreed with observations of the relative amounts of heave from each gate-road system, but the cause of heave was mainly related to the degree of anisotropy instead of the size of the pillar.

Apr 14, 2022

By BO HYUN KIM, MARK K. LARSON

The floor-heave and no-floor-heave phenomena at a western U.S. coal mine could not be properly simulated in numerical models using conventional shear-dominant failure criteria. Although the previous numerical study using FLAC3D very reasonably demonstrated these phenomena, 3DEC modeling in conjunction with the discrete fracture network (DFN) technique was performed to better understand the true behavior of floor heave associated with underground mining in an anisotropic stress field. As a result, the latter models predicted floor heave that agreed with relative amounts of observed heave from each gateroad system, but the cause of heave was mainly related to the degree of anisotropy instead of the size of the pillar.

Sep 1, 2022

By Sahendra Ram, Priyadarshi Onam, Abhishek Kumar Singh

A numerical simulation study is carried out for assessment of stability of coal pillars having dirt bands by varying its size and depths. Physico-mechanical properties of dirt bands including thickness and its position in pillar system are varied in the simulation study. Results of the simulation study are correlated with the available empirical approaches of pillar strength are validated with field observations. It is observed that the presence of weak dirt bands significantly influences the strength of pillar. An attempt is made to develop correction factor for the available empirical approaches, which are developed without considering the weak dirt bands in pillar system. The findings of the study will be helpful for suitable design of different size of coal pillars at different depths and stages of depillaring operations.

Feb 1, 2025

By Danielle Nhanqulumanga, Pranith Bhatt, Snehal Patel, Khadeeja Priyan

The Bi-Directional Static Load Test (BDSLT) is a test that determines the capacity of piles when loaded under bi-axial static compression. In recent years the BDSLT has seen an increase in demand due to its safety, speed, and affordability. This innovative foundation testing method has been universally used over the last 50 years, however respective codes and standards have only been published within the recent years. Detailed test procedures and methodology are expatiated in the ASTM D8169 M-18 [1], and the IRC 78 2014 Clause 709.2.5. [2] These standards provide the minimum requirements for the execution of the BDSLT. In this paper we did a comparative study of both standards envisaging to bring attention to the similarities and discrepancies found therein, with an aim to highlight the impacts and challenges that differing provisions of each standard could pose on the conduct of the BDSLT. Discrepancies found have been explained on the basis of geotechnical engineering theories and relevant field occurrences observed by superior engineers. Additionally, we emphasize on the relevance of experienced engineer’s judgement when utilizing the standards.

Sep 1, 2022

By G. Mark Aylmore

Various processes have been developed using a combination of elevated temperature and chemical treatment processing to recover Li from silicate minerals. To facilitate further process development, a comprehensive understanding of the deportment of Li and associated minerals in ore bodies is essential to allow the industry to predict the response of ore reserves to metallurgical treatment options. This paper describes results from the integrated use of the John de Laeter Centre’s state of the art analytical and mass spectrometry techniques to characterise a selection of Li bearing ore bodies and determine their amenability to potential processing options for the extraction of Li. The mineralogy, mineral associations, and liberation characteristics of ore-bearing and gangue minerals were characterised using a combination of the TIMA and XRPD studies. The Li content and distribution within minerals were defined using LA-ICPMS and field emission scanning electron microscopy techniques (EBSD, ToF-SIMS) and atomic probe microscopy.

The article presents an outline of methods and certain results of laboratory tests, underground tests and model tests, aimed at assessing performance of a powered shield support on the floor of low strength parameters. The tests were conducted within the framework of GEOSOFT project co financed by Research Fund for Coal and Steel (RFCR-CT-2010-00001). The described research works were conducted by Central Mining Institute (Glówny Instytut Górnictwa), Janina coal mine and Becker-Warkop

Aug 1, 2013

By G. Fehr, B. B. Panda, R. Bansberg, K. Arnold, T. Freiman

To evaluate the potential for process solutions to contaminate groundwater outside of the area of the Oxide Pit, it is necessary to predict the ultimate maximum pit lake elevation once pit-related mining activities have ceased. A water balance model was developed based on the existing pit geometry, the groundwater flow equation, and assumed hydrologic input parameters. The model assumed that at any point in time, total inflow into the system (i.e., direct precipitation, surface water and groundwater) minus outflow from the system (evaporation from the lake surface) was equal to the change in the pit water volume. The pit lake depth over time was predicted by assuming a succession of steady- state water balance conditions over short time increments. An analytical method using a spreadsheet and computer model was employed in this study to model the filling of the lake in the Oxide Pit. A sensitivity analysis was performed to evaluate uncertainty associated with the input parameters in the model. The sensitivity analysis indicated that the model was most sensitive to values of precipitation and evaporation and to the static water table.

Jan 1, 2003

By Andrew Thomson, Peter Wright

"A section of a London Underground expanded segmental lined tunnel constructed in the 1970’s progressively deteriorated after 2001, with extensive radial joint spalling and mid-segment cracking. As part of the PPP contract Tube Lines Ltd and their partners carried out various analyses of the tunnel, including analysis of laser scans of the tunnel, geotechnical testing through the tunnel walls, geotechnical desk studies, real-time monitoring and even full-scale segment testing. This paper discusses the behaviour of the tunnel lining in this setting, the causes of failure and the lessons that can be learnt from this rare example of a tunnel which was progressively failing in service. It is finally noted that a replacement tunnel lining was installed during night-time possessions and completed in 2015. INTRODUCTION In 2003, Tube Lines Ltd. was established under a Public-Private Partnership (PPP) scheme to provide maintenance services and upgrade projects for London Underground (LU). The Deep Tube Tunnel Knowledge and Inspection Programme comprised the assessment of all tunnels, shafts and other underground structures. This included a number of lengths of tunnel constructed using segmental concrete linings. First used by LU in the 1960s, the savings both in cost and speed of construction led to concrete linings replacing cast iron for new tunnel construction in all but a few cases. During the initial scoping phase of this programme, inspections identified potential issues with the expanded concrete segmental linings on the Jubilee line. The inspections found a number of segments with surface spalling (Figure 1a), which did not appear on the post-construction defect records. These were generally relatively shallow, up to 40mm deep, spread over a wide area of segment. These were different to spalls caused by handling damage, which are typically localised at segment corners. Subsequent inspections over the following years identified an increasing number of segments with these types of spalls as well as an increased incidence of longitudinal mid-segment cracking (Figure 1b). The increasing occurrence of these defects was hypothesised to be caused by tensile stresses developing in the vicinity of the joint."

Jan 1, 2016

By D. V. Dorling, J. T. Bowker, J. A. Gianetto

Over the last few years, interest in the development and construction of large diameter, high pressure pipelines from the Mackenzie Delta in northern Canada and Alaska's North Slope has steadily increased as a result of the projected decline in recoverable natural gas from existing reserves in western Canada. The success of such enormous pipeline projects, which will require utilization of a strain-based design approach, is largely based on successful application of high strength line pipe steels, such as X80 and X100. To fully realize the economic benefits of high strength steels, welding processes and procedures must be developed to ensure that the requirements for high strength and good low temperature toughness are confidently obtainable in field girth welds used in the construction of such pipelines. This study aims to provide a better understanding of the factors that control weld metal strength and toughness for a series of mechanized X100 girth welds produced using a range of narrow-gap gas-metal arc welding procedures. The attainment of high yield strength (> 810 MPa) is considered to be an important target to ensure overmatching strength relative to the longitudinal property distribution of X100 line pipe steel. Some factors that have been considered in this evaluation include influences of gas-metal arc welding process variants (single and multi-wire) and changes in welding procedure specifications, including joint preparation. Key components of this work relate to the reliable measurement of weld metal strength variation through-thickness and as a function of position around the circumference of a given girth weld.

Jan 1, 2005

By K Smith

This paper presents an assessment of the Robertson (2010a) method within the CPTu inversion parameter framework of Been et al. (1987), using CPTu calibration chamber data presented by Jefferies and Been (2015) and in other literature to assess the validity of the method, with particular focus on applicability of the method to TSFs (i.e. its applicability to loose silts and silty sands). The assessment demonstrates that although the method estimates values of k consistent with calibration chamber data, the method estimates values of m that are generally 1.5 to 2 times greater than calibration chamber data. As a result of this, the method generally overestimates Ψ for values of Ψ less than 0, and underestimates Ψ for values of Ψ greater than 0. This may result in both overly conservative assessment of materials as potentially liquefiable and unconservative predictions of material behaviour for loose materials.

Jul 1, 2021

By David Oliveira

"INTRODUCTIONOne of the key drivers for the selection of a mechanized tunneling method in good quality rock masses is a good excavation advance rate. In order to achieve satisfactory advance rates, a good geotechnical performance of the rock grippers in main beam open tunnel boring machines (TBM) is required, besides other factors related to ground support and the performance of the cutter head.One well known potential issue of main beam gripper TBM is associated with the bearing capacity of the tunnel side walls while crossing fault zones or poor rock masses in general. Such a mechanism is similar to that of footings on rock and perhaps the most common problem associated with gripper performance. Depending on the quality of the rock, the rock under the gripper contact may experience significant damage and crushing (Figure 1), eventually affecting the TBM advance rate due to a lack of tunnel wall reaction/support. Such a mechanism is primarily dependent on rock quality, applied loads and gripper size.In the case of large diameter TBMs (e.g., D > 12 m), a second potential failure mechanism may arise associated with the loss of confinement within a rock pillar between twin tunnels, even in good quality rock but particularly in bedded sedimentary strata. Punching of the rock pillar may develop due to excessive shear along bedding partings and sub-vertical joints (Figure 2), particularly under a low stress environment. As a result, this mechanism is dependent on both the rock pillar width between twin tunnels and stress conditions around the tunnels, in addition to the previous factors described for the first failure mechanism."

Jan 1, 2016

Increasing depths and mechanization of underground mines have led to the production of large amounts of gaseous and particulate contaminants. Over 100 000 lives have been lost due to methane gas and dust explosions in coal mine workings in both the United States and Canada since 1900. There is, therefore, the need to constantly assess and evaluate the performance of existing mine ventilation systems to maintain safe and acceptable mine environmental conditions. This paper advances research initiatives in the control of methane gas in underground mine environments. It uses the results of continuous monitoring of methane gas concentrations conducted in selected coal mines in North America to assess the effectiveness of existing auxiliary ventilation systems to control methane gas concentrations. The results show that the average quantities of fresh air required to dilute, disperse and remove methane gas concentrations within set levels of one minute varied from 5.43 m3/sec. to 27.97 m3/sec. in the development headings. The average dilution times in the headings studied were less than eight minutes. The calculated dilution efficiencies of the auxiliary ventilation systems in the headings varied from 12% to 139%. These efficiencies ranged from poor to excellent. This implies that the auxiliary ventilation systems were capable of controlling the methane gas concentrations below statutory levels but may not be able to cope with large and unusual methane gas concentrations in the headings. This study is significant in the control of methane gas and coal dust explosions in coal mines.

Sep 1, 2001

By Raymond S. Suglo

Increasing depths of mining coupled with the mechanization of most underground mining operations have led to growing complexities in the mine environments with the production of large amounts of gaseous and particulate contaminants. Over 100,000 lives have been lost due methane gas and dust explosions in coal mine workings in both the US and Canada since 1900 when the methane concentrations exceeded stipulated levels in some workings. There is therefore the need to constantly assess and evaluate the performance of the existing mine ventilation systems to maintain safe and acceptable mine environmental conditions in workings to meet the requirements of federal, state or provincial laws. This paper uses the results of continuous monitoring of methane concentrations conducted in selected development headings in coal mines in North America to assess the effectiveness of existing auxiliary ventilation systems in the control of methane gas concentrations in the headings. The results show that the average quantities of fresh air required to dilute, disperse and remove methane concentrations within set levels of one minute varied from 5.43 m3/s in Heading #11 (Condition 2) to 27.97 m3/s in Heading #10 (Condition 1) and this represented about 12 to 26% of the quantities required to dilute methane concentrations to safe levels within one minute under Condition 1 and 32 to 139% under Condition 2. The average dilution times in the headings studied were less than 8 minutes. The forcing efficiencies of the auxiliary systems in the headings studied ranged from poor to excellent implying that the auxiliary ventilation systems were capable of controlling the methane concentrations below statutory levels but may not be able to cope with large and unusual methane concentrations in the headings. This study is important to prevent methane gas and coal dust explosions in coal mines and thus avoid any loss of lives and property.

May 1, 2001