Underground Mining Environment Research Articles

Temperature Prediction Model in the Main Ventilation System of an Underground Mine

A model to forecast the underground temperature in a mine ventilation circuit was developed on the basis of a case study and actual data describing temperature, airflow, and drift length collected over several years. A mathematical model featuring seven variables with interactions provided reliable predicted temperatures, achieving a correlation of R2 = 0.933 with an estimation error of ±2 °C. Its soundness was proven using both the node-to-node analysis and the multi-node approach. The multi-node approach was shown to be an interesting option to model underground mining environments. This model can be very useful to predict the temperature evolution along the main ventilation system, determine the best workplace conditions in terms of temperature, and analyze different planning scenarios of the mine. Moreover, some recommendations are presented for obtaining reliable data when using temperature sensors and the model in a U-shaped ventilation system.

Internet of Things assisted radio frequency identification based mine safety management platform

AbstractThe production of any mine depends heavily on the secure relation between human and mining equipment. Protecting and optimizing the use of these tools and workers from potential accidents by real‐time monitoring and control will greatly improve mine safety and productivity. As an emerging technology, the Internet of Things (IoT) and radio frequency identification (RFID) provides a new strategy for underground production of mine security and safety. The main technologies of the Internet of Things are introduced in line with the required of mine safety production. The innovation used in this process is RFID technology, sensor technology for the conceiving of things, intelligent technology for thinking about things, and inherent security technology. In this article, the adaptive heuristic mathematical model based on IoT and RFID real‐time monitoring systems has been proposed for the production of mine safety and analysis. This system allows for real‐time tracking, detecting suspicious incidents, and verification of the position of a miner within the harsh underground mining environment. The major involvement of this research is the cost‐efficient framework to efficiently promote the protection of underground coalmines. This system helps solve serviceability, accessibility, flexibility, and interoperability problems in coal mines.

What localizes beneath: A metric multisensor localization and mapping system for autonomous underground mining vehicles

AbstractRobustly and accurately localizing vehicles in underground mines is particularly challenging due to the unavailability of GPS, variable and often poor lighting conditions, visual aliasing in long tunnels, and airborne dust and water. In this paper, we present a novel, infrastructure‐less, multisensor localization method for robust autonomous operation within underground mines. The proposed method integrates with existing mine site commissioning and operation procedures and includes both an offline map‐building process and an online localization algorithm. The approach combines the strengths of visual‐based place recognition, LIDAR‐based localization, and odometry in a particle filter fusion process. We provide an extensive experimental validation using new large data sets acquired in two operational Australian underground hard‐rock mines (including a 600m‐deep multilevel mine with approximately 33 km of mapping data and 7 km of vehicle localization) by actual mining vehicles during production operations. We demonstrate a significant increase in localization accuracy over prior state‐of‐the‐art SLAM research systems and real‐time operation, with processing times in the order of 10 Hz. We present results showing a mean error of 0.68 m from the Queensland Mine data set and 1.32 m from the New South Wales Mine data set and at least 86% reduction in error compared with prior state of the art. We also analyze the impact of the particle filter parameters with respect to localization accuracy. Together this study represents a new approach to positioning systems for currently deployed autonomous vehicles within underground mine environments.

European legal framework related to underground mining and tunnelling concerning commission directive (EU) 2017/164, 31 January establishing a fourth list of indicative occupational exposure limit values

Directive (EU) 2017/164 establishes a fourth list of indicative occupational exposure limit values (IOELVs) to protect workers from risks of exposure to hazardous chemicals. It states that in underground mining and tunnelling, Member States may benefit from a transitional period regarding IOELVs for nitrogen monoxide, nitrogen dioxide, and carbon monoxide, during which the existing established IOELVs may be applied. The European Advisory Committee on Health and Safety at Work questions the technical feasibility of the proposed IOELVs in underground mining (CO, NO and NO2) and tunnelling (NO and NO2). Challenges arise concerning the availability of measurement methodologies for compliance with proposed IOELVs (NO2) in underground mining and tunnelling environments.

Development of a combined mining technique to protect the underground workspace above confined aquifer from water inrush disaster

One task facing by the geotechnical engineers is to protect the workspace in an underground construction/excavation site from various forms of geological disasters, such as the water inrush, rock burst, and collapse of the surrounding rock/soil. In this paper, a combined controlling measure was proposed based on underground mining and water environment: the method of strip mining has been initially proposed as an effective measure against underground workspace floor failure when mining above confined aquifer in the Bucun coal mine, China, and however, its ability to avoid floor water inrush has yet to be demonstrated; in the next step, field trials using caving zone backfill technology to prevent underground workspace floor failure and excavate retained strip coal pillars were implemented based on the theoretical calculation and numerical simulation results. Engineering practice showed that the failure depth of the underlying strata of the workspace had no growth without the possibility of water inrush, and the safety of the underground space was achieved. Thus, this study represents a successful attempt to develop the combined strip mining and caving zone backfilling technique to ensure the safety of the underground workspace and control surface subsidence when excavating the retained strip coal pillars above confined aquifer. The proposed combined technique can also be used in other underground excavation activities with similar problems.

Rheological behavior of ultrafine-tailings cemented paste backfill in high-temperature mining conditions

The ultrafine-tailings cemented paste backfill (UCPB) exhibits special rheological characteristics in the high-temperature underground mining environment, which has an important influence on the stability of pipeline transportation. This study examines the time- and temperature-dependent rheological behavior of UCPB that the d(av) of tailing is 9.41 µm, and the effects of high temperature, solid content, cement content, and binder type on rheological behavior. It is found that the UCPB is yield plastic fluid with significant time-dependent characteristics under high-temperature. The UCPB is a positive thixotropic fluid that the shear stress and apparent viscosity decrease rapidly and then keep stable under a constant shear rate, and the falling curve is lower than the rising curve in the thixotropic loops. Increasing temperature causes a significant decrease in yield stress, apparent viscosity, and thixotropy. The rheological model of UCPB changes with the change of solid content, and shear-thickening occurred after the rheological curve stabilizes for solids content at 57 wt% and 54 wt%. Fly ash can effectively improve the liquidity of UCPB and reduce thixotropic behavior, due to its lubrication and water reducing effects. The hysteresis loop is not suitable as a means of quantitative analysis of thixotropy.

Effect of the heating rate on the spontaneous combustion characteristics and exothermic phenomena of weakly caking coal at the low-temperature oxidation stage

The low-temperature oxidation stage of coal spontaneous combustion (CSC) is crucial due to its impact on likelihood of spontaneous fire, as well as fire prevention in coal storage and underground mine environments. A detailed understanding of the oxidation characteristics of coal can provide a systematic understanding of CSC. A temperature-programmed experiment was conducted to simulate CSC in its low-temperature oxidation stage under different heating rates. The characteristic temperatures and oxidation performance were calculated using related functions, and the temperature distribution in space was obtained using three different measuring points. An additional experiment using a C80 micro-calorimeter was also performed to examine the heat flows. The coal sample was subjected to different heating rates, and variations in endothermic and exothermic heats were recorded using the derivative of the heat flow concerning time (dHFCT). A low heating rate promoted the exothermic effects of coal oxidation, resulting in a more thorough exothermic process.

Deploying MAVs for autonomous navigation in dark underground mine environments

Operating Micro Aerial Vehicles (MAVs) in subterranean environments is becoming more and more relevant in the field of aerial robotics. Despite the large spectrum of technological advances in the field, flying in such challenging environments is still an ongoing quest that requires the combination of multiple sensor modalities like visual/thermal cameras as well as 3D and 2D lidars. Nevertheless, there exist cases in subterranean environments where the aim is to deploy fast and lightweight aerial robots for area reckoning purposes after an event (e.g. blasting in production areas). This work proposes a novel baseline approach for the navigation of resource constrained robots, introducing the aerial underground scout, with the main goal to rapidly explore unknown areas and provide a feedback to the operator. The main proposed framework focuses on the navigation, control and vision capabilities of the aerial platforms with low-cost sensor suites, contributing significantly towards real-life applications. The merit of the proposed control architecture is that it considers the flying platform as a floating object, composing a velocity controller on the x, y axes and altitude control to navigate along the tunnel. Two novel approaches make up the cornerstone of the proposed contributions for the task of navigation: (1) a vector geometry method based on 2D lidar, and (2) a Deep Learning (DL) method through a classification process based on an on-board image stream, where both methods correct the heading towards the center of the mine tunnel. Finally, the framework has been evaluated in multiple field trials in an underground mine in Sweden.

Mine Machine Radar Sensor for Emergency Escape

This paper presents the results of recent work to develop and trial a mine machine radar sensor for underground coal mine vehicles. There is an urgent industry need for an integrated solution to the problem of operating an underground vehicle in conditions of dense ambient dust and/or smoke, such as may occur in underground coal mines after a fire or explosion. Under these conditions, sensors such as cameras and lidar offer limited assistance due to their inability to penetrate thick dust. Thermal infrared can penetrate dust but still results in poor vision, as there is insufficient temperature contrast between the tunnel walls and the ambient air. Microwave radar sensors are able to penetrate the dust, and suitable radar sensors have been developed for use in the automation industry. Adapting such sensors for use in an underground coal mining environment was the focus of this research effort, and involved trialing a suitable sensor in dust and smoke chambers as well as trials in an underground coal mine with introduced dust. Data processing and the development of a suitable user interface were key aspects of the research. Since any sensor would have to operate in an explosive atmosphere, a related research work developed a flameproof dielectric enclosure to allow the use of the radar in the mine environment.

Application of time-frequency image feature extraction method based on gray level co-occurrence matrix in coal mine pipeline leakage detection

The underground mining environment of coal mine is complex. Once the water supply or gas supply pipes leak, the location and time of leakage are unpredictable. If the leakage can not be found in time, it will seriously threaten the life safety of underground workers. Therefore, it is very necessary to automatically detect the pipeline leakage. In order to solve the problem of automatic detection of coal mine pipeline leakage, this paper proposes an image processing method based on gray level co-occurrence matrix to extract the features of time-frequency image of vibration signal. Firstly, the data in a relatively short time is divided into one frame to reduce the amount of calculation. Secondly, each frame of signal is processed by SPWVD to get the time-frequency image. Then, the time-frequency image after time-frequency analysis is transformed into gray-scale image, and the gray-scale co-occurrence matrix (GLCM) of the image is extracted. Finally, the energy, contrast and correlation of the co-occurrence matrix are extracted and input to SVM for learning and training. Through the design and build of the experimental pipeline to test the algorithm proposed in this paper, the detection result of SVM is 96.67%, which shows that this method can effectively detect the pipeline leakage.

On the formation of a mine-based energy resource complex

The paper represents the analysis, which has helped to determine tendencies of the formation of energy resource complex based on the available mining facilities. The approach helps prolong operating life of the mine with the depleted balance reserves or the one being under abandonment. The proposed technologies of generator gas production by anaerobic digestion of organic raw material in the methane-tanks as well as other approaches to the combined formation of new energy systems make it possible to reorient the mine operation. The approach is extremely important for rather depressed mining regions as it helps solve the problem of social strain. Formation of the joint power and chemical production allows both improving economic expediency and preventing negative ecologic impact on surface and underground mine environment. The proposed tendencies make it possible to outline further issues to be highlighted in the following authors’ studies.

Study on the Instability Mechanism and Grouting Reinforcement Repair of Large‐Scale Underground Stopes

The environmental conditions due to unreasonable mining in underground stopes, the slurry diffusion mechanism in the grouting reinforcement of a stope within its influence, the causes of large‐scale instability collapse, and the catastrophic stope process are analyzed, and limit upper line analysis theory and numerical analysis methods are comprehensively adopted, revealing the continuous catastrophic collapse mode of large‐scale underground stopes. The method of determining the stope instability collapse boundary and the slip surface within the range based on the theory of the maximum shear strain increment is proposed, and the diffusion radius and range of the grouting slurry during the reinforcement process, which considers the multifield coupling factors, are obtained. The results show that the U‐shaped hidden danger area formed after the collapse of the large‐scale underground stope. The influence range reaches six adjacent stopes, which are symmetrically distributed around the collapse; the mining instability is manifested as a catastrophic chain process of stress change, energy accumulation, state change, and instability collapse. The damage mode of instability collapse is a combination method of wedge collapse, circular arc rotation, triangular translation, and strip slip. According to the multiphysics coupling numerical calculation, the diffusion radius of the grouting slurry is 12 m, exhibiting an elliptical distribution. The research results can be used to comprehensively control the underground mining environment, thus effectively solving the safety problems faced by tunnel or roadway excavations above the goaf.

CFD simulations of DPM flow patterns generated by vehicles in underground mines for different air flow and exhaust pipe directions

In this paper, an attempt is made to model diesel particulate matter (DPM) flows generated by load haul dumpers (LHDs) and trucks in an underground mine environment for different DPM flow and intake air flow directions and exhaust pipe directions. The results obtained show that the DPM concentration near the vehicle was dependent on exhaust pipe location and direction. If the exhaust pipe is located at the rear or the top of the vehicle, the vehicle operator may be susceptible to exposure to high concentrations of DPM. If the exhaust pipe is located at the bottom of the vehicle, the operator is less likely to be exposed to high concentrations of DPM. Finally, at 10 m downstream of the loading bay the very high concentrations DPM particles tend to spread over the entire cross section of the roadway.

A VLC Channel Model for Underground Mining Environments With Scattering and Shadowing

Underground mining is an industry that preserves the miners' safety and efficiency in their work using wireless communication systems as a tool. In addition to communication links characterized by radio frequency signals, optical links in the visible light spectrum are under intense research for underground mining applications due to their high transmission rates and immunity to electromagnetic interference. However, the design of a robust visible-light communication (VLC) system for underground mining is a challenging task due to the harsh propagation conditions encountered in mining tunnels. To assist researchers in the design of such VLC systems, we present in this paper a novel channel model that incorporates important factors that influence the quality of the VLC link in underground mines. Features such as an arbitrary positioning and orientation of the optical transmitter and receiver, tunnels with irregular walls, shadowing by large machinery, and scattering by dust clouds are considered. These factors are integrated into a single modeling framework that lends itself for the derivation of compact mathematical expressions for the overall DC gain, the impulse response, the root mean square delay spread, and the received power of the proposed VLC channel model. Our analytical results are validated by computer simulations. These results show that the rotation and tilt of the transmitter and receiver, as well as the tunnels' irregular walls have a notorious influence on the magnitude and temporal dispersion of the VLC channel's line of sight (LoS) and non-LoS components. Furthermore, results show that shadowing reduces the LoS component's magnitude significantly. Our findings also show that scattering by dust particles contributes slightly to the total VLC channel gain, although it generates a large temporal dispersion of the received optical signal.

Design and Evaluation of the Roof Bolt Corrosion Test System in a Simulated Underground Coal Mine Environment

Corrosion of steel roof support systems can cause potential premature failure of the support, thus adversely affecting the excavation stability and rock-related safety. An in-house corrosion test system was designed and developed to test full-length roof bolts for material performance based on tensile load capacity and strength under different corrosive conditions found underground. The roof bolts tested are also used to identify the possible corrosion mechanisms that influenced the bolts’ performance over time. Initially, the most commonly used bolt material in the USA, the ASTM A615 grade 60 steel roof bolts, was tested with and without stresses in a simulated underground coal mining environment for approximately 6 months, and the results are discussed. Localized corrosion forms such as crevice and pitting were mainly observed after testing. The stressed and unstressed roof bolts with and without threads that were tested in alkaline coal mine corrosive environment for 6 months passed their load-bearing capacity as per ASTM F432 test standards. From the results, it is concluded that this test protocol could be applicable to test the material performance of different roof bolt metallurgies and coatings with desired modifications to the proposed methodology for the specific underground mine environment. This paper mainly discusses the test system and protocol and shortcomings of the system and makes recommendations based on the observations and results.

Hybrid Model-Based Analysis of Underground Articulated Vehicles Steering Characteristics

Owing to the harsh environment of underground mines, autonomous underground articulated vehicles (UAVs) with precise control and positioning system are particularly important. However, the ambiguity of steering characteristics hinders the development of UAVs. This study presents a model-based method to uncover the steering characteristics of a UAV. Firstly, a hybrid model of UAV was established, which included a dynamic model of articulated frames and a model of the hydraulic power steering system. Secondly, a field test of a typical UAV, a load-haul-dump (LHD) with 4 m3 capacity, was carried out. In order to verify the correctness of the established model and the accuracy of the involved parameters, the field test results were used to verify the dynamic model in time and frequency domains. Then, the steering characteristics of the UAV were uncovered based on the verified hybrid model, and the results showed that the increased load would increase ‘oversteering’ under the same articulation angle and that the error of trajectory exceeded 0.3 m. In addition, the deviations of trajectories between the two frames were revealed during the transient steering process, and the maximum deviation reached 0.21 m when the velocity was 2 m/s and the articulation angle was 15°. The comprehensive results indicate that the steering characteristics of UAVs cannot be ignored in regard to precise autonomous control and positioning.

TIMTAM: Tunnel-Image Texturally Accorded Mosaic for Location Refinement of Underground Vehicles With a Single Camera

Many mine-site processes such as vehicle operation require localisation systems that are reliable, robust and work in a range of environmental conditions. In underground operations, GPS is not available: solutions instead rely on static infrastructure or expensive, laser-based solutions with limited operational capability. In this letter we present a new vision-based technique, Tunnel-IMage Texturally-Accorded Mosaic (TIMTAM), for sub-metre, infrastructure-free localisation in underground mining environments using a single camera. Our approach stitches upward-facing camera images to form planar mosaic maps, using locations generated by the coarse mapping engine based on a small number of manually anchored locations. Localisation is achieved by refining coarse location estimations with a best fit pixel location for the query image within a search neighbourhood in the mosaic map. Our direct pixel-based method is more robust to the challenging illumination and surface-texture environments encountered in underground mine operations than feature-based techniques. Localisation refinement is only triggered when a confidence threshold for the estimate is exceeded. The system is evaluated in a real world mine tunnel, with results showing that the confidence threshold approach is predictive of the quality of the location estimate refinement, and achieves a reduction in mean localisation metric error of up to ∼ 66% from simulated coarse results.

The medical perspective on mining incidents

PurposeThe purpose of this paper is to examine emergency medical service (EMS) personnel’s perceptions and experiences of managing underground mining injury incidents.Design/methodology/approachIn total, 13 EMS personnel were interviewed according to a semi-structured interview guide. The interviews were transcribed verbatim and analyzed using qualitative content analysis.FindingsAn underground mining environment was described as unfamiliar and unsafe and, with no guidelines for operational actions in an extreme environment, such as underground mines, the EMS personnel were uncertain of their role. They therefore became passive and relied on the rescue service and mining company during a major incident. However, the medical care was not considered to be different from any other prehospital care, although a mining environment would make the situation more difficult and it would take longer for the mine workers to be placed under definitive care.Originality/valueThis study complements earlier studies by examining the EMS personnel’s perceptions and experiences of major incidents.

Modeling and measurements for wireless communication networks in underground mine environments

One of the crucial problems being faced by wireless system designers is experimental understandings of the electromagnetic (EM) wave propagation in high stress environments, such as underground mines and tunnels, so that reliable performance can be achieved. This is driven by the fact of limited availability of real-time data of operational underground mines with different measurement considerations. This paper reports extensive experimental studies and proposes a modified multimode based channel model for wireless communication networks in underground mine environments. The experimental campaigns were carried out in an underground coal mine considering significant use cases viz. line of sight (LOS), no line of sight (NLOS), across the curves and bends, in noisy environments, straight tunnels, and near the face (extraction area). We then validated the proposed channel model with the experimental measurements. The validation results showed reliably a good agreement with a model accuracy of 94.60%, 91%, 90.98% for the straight tunnel, along the belt conveyor and near face respectively. The proposed model outperforms the state-of-the-art channel model for mine workings with model accuracy differences of 60.1%, 60.45% and 58.56% for straight tunnel, along the belt conveyor and near face respectively. A model accuracy of 78.31% is achieved across the curvature measurement scenario. Hence, the proposed channel model can be accepted for wireless communication system design and deployment planning in underground mines to provide a reliable two-way wireless communication and coverage. Furthermore, detailed link analysis of wireless sensor networks in mine workings is also discussed considering packet reception rate with respect to distance and received signal strength.

Overlying strata movement with ground penetrating radar detection in close-multiple coal seams mining

Longwall mining is a productive mining method that has been widely used in China, the United States, Australia, and Europe. However, due to the subsidence caused by coal mining activities, the phenomenon is complex, longwall mining brings the overburden movement issues accompany with the coal recovery. In subsidence trough, the resulting strata and surface ground movements are regarded as largely contemporaneous with mining, producing more or less direct effects of natural ecology. Ground penetrating radar has been widely used in geological hazard detection due to its high precision, but it is rarely employed in underground measuring the overlying strata movement above the longwall panel. In this article, there are five close-multiple coal seams (5#, 7#, 8#, 9#, 12# seams) within 70 m distance to be monitored in Qian Jiaying coal mine of Kailuan Coal Company in Hebei province. The 7#, 8#, 9#, 12# coal seams were already excavated in sequence. So the 5# coal seam is overmining above the gobs of four coal seams at the top. The ZTR12-series ground penetrating radar equipment is used to detect the development of fractures under the floor of the 5# coal seam. The ZTR12-series ground penetrating radar system has the capability of large depth detection and explosion proof to adapt to the working environment of underground coal mines and can realize fine detection and accurate identification. The maximum detection distance of reflection method can reach 50 m. The measurement results show that the 5# coal seam is in the fracture zone above the gobs of four coal seams, and the caved zone of lower coal seam develops to fine sandstone of the 5# coal seam floor. The ground penetrating radar has shown much promise in the detection of overlying strata movement.