Underground Mining Research Articles

Retrieving Seismic Source Characteristics Using Seismic and Infrasound Data: The 2020 ML 4.1 Kiruna Minequake, Sweden

AbstractA minequake of magnitude ML 4.1 occurred on 18 May 2020 early in the morning at the LKAB underground iron ore mine in Kiruna, Sweden. This is the largest mining‐induced earthquake in Scandinavia. It generated acoustic signals observed at three infrasound arrays at 9.3 (KRIS, Sweden), 155 (IS37, Norway), and 286 km (ARCI, Norway) distance. We perform full‐waveform focal mechanism inversion based on regional seismic data and local infrasound data. These independently highlight that this event was dominated by a shallow‐depth collapse in agreement with in‐mine seismic station data. However, regional infrasound data cannot inform the inversion process without an accurate model of atmospheric winds and temperatures. Yet, our numerical simulations demonstrate a potential of using local and regional infrasound data to constrain an event's focal mechanism and depth.

Durability performance of BFRP-confined coal gangue concrete exposed to the sulfate-rich mine environment

The combination of basalt fiber reinforced polymer (BFRP) confinement and coal gangue concrete (CGC) is an economical and innovative approach for serving as a supporting structure in the underground mine. Nevertheless, the sulfate-rich mine water and mist exist in the mine environment, which may cause the performance deterioration of structures. Thus, the long-term behavior of BFRP-confined CGC in the sulfate-rich environment was systematically explored, based on the sulfate durability investigation of BFRP sheets and CGC. The tensile test of BFRP sheets and the compressive test of CGC were first carried out to evaluate their deterioration laws and mechanism in different sulfate environment. More importantly, axial compression test of FRP-confined concrete cylindrical specimens after sulfate attack were conducted, considering the effect of inner concrete, FRP layer, sulfate concentration and corrosion time on the stress-strain response and dilation properties. The results indicate that the tensile strength of BFRP sheet declined to a small extent with the extension of sulfate corrosion due to the degradation of epoxy resin and matrix-fiber interface. Additionally, the compressive strength of CGC exhibits a first increase and then decrease trend as the secondary hydration occurs and the sulfate ions react with the hydrated production to form expansive gypsum and ettringite crystals. The strength and ductility of CGC were improved by FRP confinement regardless of sulfate attack or not, whereas sulfate corrosion degraded the improvement ratio, especially the deformation capacity. Most importantly, the sulfate degradation coefficients were introduced into ultimate strength and strain models for sulfate-attacked BFRP-confined CGC, providing a basis for its design and life cycle assessment in the underground mine.

Source types of induced earthquakes in underground mines: Revealed by regional moment tensor inversion

Mining-induced earthquakes have been very frequent in recent years due to increasing mechanized mining. Compared with natural earthquakes, even a small one may cause significant damage to the mine area and its surroundings. Source type identification is important for better understanding the physical processes and is a crucial and fundamental issue for hazard assessment and emergency rescue in the mining environment. The moment tensor (MT) theory plays a pivotal role in distinguishing different source types. In this study, we concentrated on two strong reported “mine collapse earthquakes” in Qufu (ML 3.2, July 13, 2020) and Zoucheng (ML2.9, June 09, 2020), Shandong Province, China. Seismograms from regional seismic stations were utilized to calculate the full moment tensors through low-frequency full-waveform inversion. Our results show that the two studied events exhibit notably different source types. The DC (Double-Couple) component of both events are 5% (Qufu) and 60% (Zoucheng), respectively. The Qufu event which contains approximately 75% closing crack component, is more consistent with the theoretical models of collapse seismic source. However, the Zoucheng event, which exhibits a significant proportion of DC components, demonstrates characteristics typical of shear failure. Focusing on the Zoucheng event, which occurred at the Dongtan Coal Mine, further research was conducted on a local mining scale. Analyzed in conjunction with microseismic sensor data, geologic setting, and mining progress, we illustrated that the source type of Zoucheng event is not a collapse one. The fracture slip of a thick-hard roof due to an overlying load, characterized by a large DC component, is a plausible geomechanical interpretation.

Optimizing Mining Ventilation Using 3D Technologies

Abstract. Ventilation systems constitute an important piece of the industrial facility ecosystems. Creating proper working environmental conditions for humans is crucial, especially in hazardous sites with presence of various gases, such as underground mines. Combined with the vast amount of space to be ventilated in large mines, designing and maintaining such a system is challenging and costly. To alleviate these issues, the EIT-RM project VOT3D (Ventilation Optimizing Technology based on 3D scanning) proposes conducting advanced airflow modeling in the underground tunnel networks, utilizing computational fluid dynamics (CFD) simulations, modern surveying and 3D modeling approaches to reverse engineer a reliable geometric model of the mine and estimate the 3D airflow field inside it. In this paper, we present the challenges to be solved in this task and the proposed workflow to address them. An example related to an active industrial mine in Poland is reported as a basis for performing experimental data processing using the full, highly automatized procedure. Developments and results of underground mobile mapping (with a drone and a handheld system), point cloud processing and filtering, surface reconstruction and CFD modeling are presented. The detailed results of airflow field estimation show the advantages of the proposed solution and promise its high practical usefulness.

The Influence of Geotechnical, Geological and Mining Factors on the Formation of Sinkholes at Lubambe Mine, Zambia

Mining-induced sinkholes are a common feature in underground mines. Sinkholes usually disrupt mining operations and associated infrastructure when they occur. This paper presents a case study of the Lubambe copper mine, where nine (9) sinkholes have been reported on the eastern and southern limbs. The development of sinkholes has resulted in increased mining costs due to the closure of the 182 mL decline on the eastern limb and the 175 mL truck route on the southern limb. This study establishes the influence that poor ground formation, rock stability, geological structures, and inappropriate mining practices have on the formation of surface sinkholes. Assessment of ground condition was done by core logging, and borehole analysis was conducted using GEM4D-BasRock software to classify the rock mass quality based on RQD, RMR, Q-System and GIS. Assessment of the mining operational environment was focused on the effects of varying stope designs and sequencing on ground stability. Results of the study indicate that the formation of surface-induced sinkholes is attributed to historical mining in weak rock formation and weathered rock coupled with subsequent failure of unsupported stopes with stope height between 8 and 25 metres and less stand-up time of 7 days.

Constructing artificial cover layers for supercritical carbon dioxide sequestration: A novel approach to old goaf remediation and carbon emission reduction

Over the past centuries, global coal mining activities have resulted in the formation of 242.36 billion cubic meters of underground goaf areas, resulting in the waste of billions of square meters of land resources. Furthermore, this phenomenon has introduced significant safety hazards and environmental risks. In addressing the challenge of the inability to directly sequester supercritical carbon dioxide in coal mine goaf areas due to extensive fracturing of the surrounding rock mass caused by underground mining, an innovative approach is proposed. This involves the construction of artificial cover layers within the overlying rock strata of abandoned coal mine goaf areas, offering a novel strategy for the sequestration of supercritical CO2 in such geological contexts. Considering the development characteristics of fractures in the overlying strata of coal mine goaf areas, a functional relationship model is established to delineate the sealing capacity of artificial cover layers in relation to the burial depth, length, width, and thickness of the cover layers. A design methodology for constructing artificial cover layers tailored for sequestering supercritical CO2 in abandoned coal mine goaf areas is proposed, providing technical support for its widespread application. Building upon this foundation, an assessment model for the sequestration capacity of abandoned coal mine goaf areas for supercritical CO2 is developed. The calculations indicate a global sequestration potential of approximately 72.71–218.12 billion tons of supercritical CO2, with anticipated economic benefits ranging from 657.36 to 1991.47 billion USD. The research outcomes present a promising avenue to assist carbon-neutral initiatives in coal-dependent urban areas globally.

Model of the Formation of Work Safety Culture in Polish Mining Enterprises

The article presents the results of research on the level of work safety culture, which is an important element influencing the organisational culture in mining enterprises. The article aims to measure the safety culture among managers in Polish hard coal mines. The assumed goal was achieved in the area of literature and empirical research. Research shows that the precise identification of hazards defined the thematic areas shaping safe working conditions in underground mines. The main part of the work was to survey 135 employees in 3 hard coal companies in Poland. The questionnaires were developed in cooperation with mining experts, and the 5-point Likert scale was used to evaluate individual questions. This methodological approach identified the subjective feelings and experiences of employees for building appropriate attitudes and behaviours that shape the organisational culture. The use of a culture grid enabled the creation of seven thematic groups of safety areas related to the so-called referents of organisational culture. The result of the empirical research is to propose an approach for the transformation of safety culture in the selected area for mining companies. The approach uses the organisational culture grid to shape the attitudes and behaviours of employees, which identifies and designates weak areas, defining them as unsatisfactory and unacceptable, and being the key conclusion of the research.

Analysis of Potential Use of Freezing Boreholes Drilled for an Underground Mine Shaft as Borehole Heat Exchangers for Heat and/or Cooling Applications

Borehole engineering encompasses the part of mining that involves the process of drilling boreholes and their utilization (e.g., for research, exploration, exploitation, and injection purposes). According to legal regulations, mining pits must be closed after their use, and this applies to pits in the form of boreholes as well. The Laboratory of Geoenergetics at AGH University of Krakow is involved in adapting old, exploited and already closed boreholes for energetic purposes. This includes geothermal applications, as well as energy storage in rock formations and boreholes. Geoenergetics is a relatively new concept that combines geothermal energy with energy storage in rock formations (including boreholes). One type of analysed borehole is a freezing borehole. They are used, for example, in drilling mining shafts that are in the vicinity of aquifers and are drilled using the rotary drilling method with a reverse circulation of drilling mud, or in peat bogs. For borehole heat exchangers based on freezing boreholes for long-term mathematical modelling, several heating scenarios were considered with several thermal loads. The maximum average power obtained after one year of usage of four boreholes with variable temperatures was 11 kW. With the usage of 10 boreholes the power reached over 27 kW. The heat-carrying temperature was assumed to be 22 °C during early summer (June and July) and 2 °C during the rest of the year. When considering stable exploitation during a 10-year period with four boreholes with the same temperatures, a heating power of over 12 kW was obtained, as well as a power of over 28 kW when considering using 10 boreholes. The maximum amount of heat obtained during the 10-year period using 10 boreholes was over 8.8 thousand GJ. Once they have fulfilled their function, these boreholes lose their technological significance. In the paper, the concept is outlined, and the results of the analysis are described using the numerical program BoHEx.

Cannibalistic exchanges with mountain‐ancestors: Moral economies of gold mining in northern Peru

AbstractCampesinos (peasants) and norteños (northerner entrepreneurs) in highland Huamachuco, la Libertad, northern Peru—reconcile their mining within Andean practices about the perceived sentience and agency of mountain‐ancestors (apus). They do so by engaging in two different types of apu cannibalism that are antithetical to each other. I analyze how the conflict between Andean campesino communities who practice small‐scale underground mining on the apu El Toro site, and, the Summa Gold open‐pit mining company (owned by former campesinos now norteño) also on apu El Toro, reshapes, on both sides, relationalities with mountain‐ancestors and capitalism. I explore miners’ practical moral economies with apus, the local government, and legal authorities to secure economic and political benefits as their worlds are transformed by capitalism. I also analyze how the power inequality between campesino and norteño miners shapes these exchanges, their ability to control the limits of extractivism, and the rhetoric around mining contamination.

A parameter inversion method for the probability integral method based on robust ridge estimation

The probability integral method is one of the most widely used methods for predicting surface subsidence induced by underground mining in China. In its parameter calculation, the least square algorithm is commonly employed for fitting parameters. However, in the process of fitting parameters, the results are easily affected by ill-conditioned normal matrices and the interference of outliers, resulting in divergent problems. To solve these problems, the principle of robust ridge estimation was introduced in this paper, and a parameter calculation model for the probability integral method based on this principle (hereafter referred to as the established model) was established. Besides, a parameter calculation experiment with manual intervention was conducted in combination with engineering examples. The results demonstrate that the parameter calculation method based on robust ridge estimation can suppress the interference of outliers, overcome the problem of ill-conditioned matrix, and ensure the effectiveness and reliability of parameter estimation results. Compared with the conventional least squares method, the robust ridge estimation method demonstrates greater accuracy in predicting surface subsidence parameters, which validates its rationality and accuracy in underground mining engineering. The research findings provide technical support for obtaining similar parameters for surface subsidence in mining areas and hold significant engineering application value.

Effect of wet-dry cycle on triaxial mechanical properties and constitutive models of solid waste cemented backfill

As the environmental requirements of underground mine backfilling processes have been promoted, solid waste cemented backfilling (SWCB) technology is widely exploited in goaf backfilling. Due to the groundwater circulation and geothermal drying effects, the SWCB is often exposed to the cycle period of wetting and drying state. To study the influence of wet-dry state transformation on the mechanical properties of SWCB, a series of triaxial compression tests were carried out on SWCB specimens treated with wet-dry cycle. As the cycle numbers increased, first, mass-loss behavior occurred and then hydration damage gradually accumulated in the SWCB specimen, where the maximum mass loss rate (Rw-d) was 7 %. The triaxial compressive strength (TCS) and elastic modulus of SWCB increased with the increase in confining pressure but decreased with the increase in cycle numbers. In low cycle numbers, the wet-dry cycle treatment did not damage the skeleton structure, and the SWCB specimen could still bear external load after failure. A constitutive model considering residual strength was established to describe the stress state and failure process of SWCB specimens. In high cycle numbers, hydration damage occurred and was widely distributed in the SWCB specimen. A rheology constitutive model was established to reflect the stress-strain relationship and flow failure characteristic. From the scanning electron microscopy (SEM) results after SWCB specimen failure, main cracks and many partial microcracks appeared in the low and high cycle numbers, which verified the applicability for two constitutive models. Aiming at the negative effect of wet-dry cycle on the mechanical properties of SWCB, isolating water source and protecting SWCB were proposed to prevent and control the large deformation of SWCB and surface subsidence induced by rheological behavior.

Evaluation and Comparison of Rock Bolting Versus Steel Arch Support Systems in Thick Coal Seam Underground Galleries: A Case Study

This study investigates the feasibility of rock bolting support in an underground coal mine gallery with a thick coal seam. The Ömerler underground coal mine working area, owned by the West Lignite Enterprise (GLI) of the Turkish Coal Enterprises (TKI), was selected for this purpose. Longwall top coal caving (LTCC) is implemented as the production method in the Ömerler underground coal mine. Field and laboratory studies were conducted to determine rock mass and rock material properties, followed by experimental, empirical, and numerical analyses based on the acquired data. The obtained design results were evaluated using a resin-grouted rebar (RBR) rock bolting system and steel arch support (SAS) pilot application areas. The numerical modeling results conducted using the Fast Lagrangian Analysis of Continua 3D (FLAC 3D) (v6.0) program indicated less displacement and secondary stress change in the RBR-supported zone compared to the SAS-supported zone. In situ measurements also demonstrated that RBR provided more successful support to the roof during coal production activities. The findings suggest that RBR is a more effective solution when evaluating the feasibility of rock bolting support systems in underground galleries with thick coal seams at the Ömerler underground coal mine. This study emphasizes the importance of more sustainable and safe support systems to enhance operational efficiency in the coal mining industry.

A COMPARISON OF NON-DESTRUCTIVE DEFECT DETECTION METHODS FOR STEEL WIRE ROPES

Steel wire ropes are among the essential technical elements widely used in many industries. The impeccable condition of these elements has a major impact on the safety of entire facilities where they are applied, be it construction, mining, agriculture, transport, engineering or another area. This article focuses on comparing two non-destructive methods designed to study the internal defects of steel wire ropes. They are defectoscopes with different principles of operation, namely the MID-3 magnetic defectoscope with both excitation and detection of the magnetic field by means of induction coils, and the REMA defectoscope with Hall sensors. Four reference samples of steel wire ropes used in underground mines with well-defined defects corresponding to damage due to fatigue of the wire rope material were created for the study. Based on the experiments performed, it was confirmed that defectoscopes working on the principle of Hall sensors can detect metal cross section loss adequately.

A Causal Analysis of the Influential Criteria in Underground Mining Method Selection

A Causal Analysis of the Influential Criteria in Underground Mining Method Selection

Thin seams and small mines are associated with higher exposures to respirable crystalline silica in US underground coal mines

ObjectivesPrevious radiologic and histopathologic studies suggest respirable crystalline silica (RCS) overexposure has been driving the resurgence of pneumoconiosis among contemporary US coal miners, with a higher prevalence of severe disease...

Safety Monitoring and Auto Alert System in Underground Collieries

In the current scenario, significant mine disasters often occur due to explosions and fires. The occurrence of unexpected underground mine landslides poses a significant threat to miner safety, leading to fatalities. Consequently, the proposed system actively monitors key parameters and issues alerts to miners, aiming to mitigate this risk. The system primarily focuses on monitoring gas levels, air quality, temperature, and vibrations in underground mines, with the data being continuously recorded and stored in the ThingSpeak cloud. Visualization of the data is achieved through field charts created within the designated channel. The cloud-stored data is linked with MathWorks to predict missing values, providing a basis for proactive measures. The predicted missing values are then stored in a separate channel on ThingSpeak for continuous chart visualization. This data, complete with timestamps, can be exported to excel for further analysis and application. The scenario of the coal mine is monitored and regular reports are sent to the personnel’s mail which is automated in Thingspeak. In the event of an explosion, the rescue team is promptly notified through SMS alerts using a GSM modem.

Вредные вещества в воздухе рабочей зоны горнодобывающего сектора металлурги-ческой промышленности как факторы риска для здоровья работников (аналитический обзор)

Working conditions at non-ferrous metallurgical enterprises typically involve exposure to a whole set of harmful chemicals present in occupational air. These chemicals contribute to the development of pathologies in workers, respiratory diseases in particular. Research literature was analyzed using bibliographic databases in order to summarize available information on effects produced by harmful chemicals in workplace air on health of workers employed at mining enterprises. Respiratory diseases such as pneumoconiosis, acute and chronic dust bronchitis prevail among occupational pathologies typical for underground miners. Acute and chronic bronchitis prevail among respiratory diseases as health disorders resulting in temporary disability of miners dealing with non-ferrous metal mining. Huge amounts of dust appear in occupational air at mining enterprises due to drilling, blasting and ore crushing. Priority chemicals found in workplace air in mining industry include several carcinogens such as nickel, lead, formaldehyde, cadmium, and benzo(a)pyrene. There is a unidirectional effect produced by sulfur dioxide, nickel, nitrogen oxides, acrolein, formaldehyde, cadmium, and particular matter on the respiratory organs. The nervous system can be affected by manganese, lead, and selenium; the blood, by nickel, lead, and carbon oxide; the cardiovascular system, by carbon oxide and selenium. Working conditions of underground miners in non-ferrous metallurgy involve intensive exposure to chemicals in occupational air, which create health risks of occupational respiratory diseases and malignant tumors. Diseases of the nervous, immune, cardiovascular systems and the blood are also possible. When planning a set of preventive activities, it is advisable to identify groups of work-related diseases caused, among other things, by a specific chemical factor.

Harmful chemicals in occupational air in the ore mining sector of the metal industry as occupational health risk factors (Analytical review)

Working conditions at non-ferrous metallurgical enterprises typically involve exposure to a whole set of harmful chemicals present in occupational air. These chemicals contribute to the development of pathologies in workers, respiratory diseases in particular. Research literature was analyzed using bibliographic databases in order to summarize available information on effects produced by harmful chemicals in workplace air on health of workers employed at mining enterprises. Respiratory diseases such as pneumoconiosis, acute and chronic dust bronchitis prevail among occupational pathologies typical for underground miners. Acute and chronic bronchitis prevail among respiratory diseases as health disorders resulting in temporary disability of miners dealing with non-ferrous metal mining. Huge amounts of dust appear in occupational air at mining enterprises due to drilling, blasting and ore crushing. Priority chemicals found in workplace air in mining industry include several carcinogens such as nickel, lead, formaldehyde, cadmium, and benzo(a)pyrene. There is a unidirectional effect produced by sulfur dioxide, nickel, nitrogen oxides, acrolein, formaldehyde, cadmium, and particular matter on the respiratory organs. The nervous system can be affected by manganese, lead, and selenium; the blood, by nickel, lead, and carbon oxide; the cardiovascular system, by carbon oxide and selenium. Working conditions of underground miners in non-ferrous metallurgy involve intensive exposure to chemicals in occupational air, which create health risks of occupational respiratory diseases and malignant tumors. Diseases of the nervous, immune, cardiovascular systems and the blood are also possible. When planning a set of preventive activities, it is advisable to identify groups of work-related diseases caused, among other things, by a specific chemical factor.

Failure Analysis of Abutment-Loaded Underground Coal Mine Stoppings during Explosion

Failure Analysis of Abutment-Loaded Underground Coal Mine Stoppings during Explosion

Stability Analysis of Pillars in Underground Limestone Mine Using Three-Dimensional Scanning Techniques

Stability Analysis of Pillars in Underground Limestone Mine Using Three-Dimensional Scanning Techniques