Coal Mining Applications Research Articles

Experimental investigation of the influence of mine water on mechanical properties of resin grout

Resin grout is widely used in geotechnical and underground engineering, and is often affected by different mine water solutions. This study considered the effects of different mine water solutions and soaking times on resin grout. Soaking tests and uniaxial compression tests were conducted to investigate the changes in the solution pH, relative specimen mass, and uniaxial compressive strength (UCS), and the deterioration of the resin grout’s mechanical properties caused by the mine water solution was analyzed. The corrosion mechanism of resin grout under the action of different mine water solutions was investigated through scanning electron microscopy tests. The results reveal that the pH value of the solution and the relative mass of the specimen gradually stabilized as the soaking time was extended, and the final solution was weakly alkaline. The increase in the acidity and alkalinity of the solution and the extension of the soaking time led to a gradual decrease in the UCS and elastic modulus of resin grout under the action of mine water. As the soaking was prolonged, the resin grout properties deteriorated to different degrees and Poisson’s ratio increased. Moreover, owing to the different types and degrees of mine water action on resin grout in different mine water environments, the changes in the resin grout microstructure were also different. The defined damage parameters can express the damage process of the resin grout’s UCS quantitatively under the action of mine water solution. Finally, beneficial engineering application countermeasures are proposed for different resin grout types used in roadway support applications in coal mines.

Exploration of the microbial dust suppressant application in open-pit coal mines: Dust source conditions and application processes

To promote large-scale application, this paper studied the influences of different dust source conditions and application processes on microbial dust suppressant. Results showed that microbial dust suppressant could adapt to various dust source conditions. The wind erosion rate of samples did not exceed 47 g·m−2·min−1 after a single spraying volume of more than 1.25 L·m−2 and more than 4 spraying times. The change of CaCO3 crystallinity (about 6%) and crystal forms led to the change of hardness and thickness of the cemented layer (about 12–24%). The crystallization process of microbial dust suppressant is an important factor affecting performance, which is mainly regulated by saturation. In addition, the contact distribution mode of CaCO3 between particles and its corresponding pore was put forward. CaCO3 deposited by surface contact was the key to improving dust suppression performance. Under the background of large-scale application, 1.25 L·m−2 and 2 times for spraying were more suitable.

A Kind of High-Efficiency Dust Extinguishing Protection Device for Coal Mine in Huangbaici Coal Mine Practice and Application

A Kind of High-Efficiency Dust Extinguishing Protection Device for Coal Mine in Huangbaici Coal Mine Practice and Application

The conditions for proper operation of the arch-rectangular support

Steel arch-rectangular support has a wide range of applications in Polish coal mines due to its asymmetrical shape. The frame has an arched outline on one side of the side wall, while on the opposite side it is rectangular. As a result, the support is ideal for securing set up room and recovery room. It can also be successfully used to secure three-way intersections of underground workings. To a large extent, however, the importance of these advantages is diminished by relatively low load-bearing parameters, resulting from a partially straight canopy, as well as the asymmetrical distribution of the load acting on the support in underground conditions. In order to ensure the proper and optimal operation of such frames, in addition to the standard requirements for roof supports, additional conditions must be met. The basic requirement is to support the end of the canopy on the corner of the excavation. This article presents examples of arch-rectangular supports, their applications as well as laboratory tests and strength analysis of the frames and its elements. These tests allowed the requirements regarding the construction of the frame, the selection of the support and the conditions of building in the excavation to be specified.

Research on the classification and control of human factor characteristics of coal mine accidents based on K-Means clustering analysis

The occurrence of coal mine accidents is closely related to human factors. Six-hundred eighty five coal mine accident reports were analyzed to identify risk factors for coal mine accidents. A total of 29 human factors were classified from three levels of supervision-management-production using the improved HFACS (Human Factors Analysis and Classification System) model, and the degree of clustering of human factors was verified by complex networks. Then, the 29 human factors were classified into four categories by K-Means clustering analysis, namely subjective corrective accident human factors, perceived corrective accident human factors, associated corrective accident human factors, and critical corrective accident human factors, and control suggestions were proposed for different categories. Finally, the interface of the supervision-management-production-based coal mine employee control system was designed in order to provide a solid theoretical basis for the subsequent system development and its application in specific coal mines. This study can provide new ideas for the study of human factors of coal mine accidents and help coal mine enterprises to strengthen the control of human factors.

Study of distribution mechanism for high water-based hydraulic motor

In coal mining, food manufacturing, and underwater applications, high water-based hydraulic motors (HWBHM) offer the advantages of high specific power and media friendliness. The water motors in these applications maintain the traditional structure and only replace the working medium with a high water-based fluid. However, the conventional plate flow distribution structures are limited by severe leakage, especially at low speeds and high pressure. In the context of underground emulsion drive systems for mining, a valve flow distribution mechanism comprising the valve and pentagon-wheel is proposed. Intaking and discharging processes of the motor are controlled by the valves, which are driven by the pentagon-wheel motion. A model of the motor is established using the AMESim simulation method to validate the feasibility of the new distribution structure. The numerical investigation into the flow filed characteristics inside valves shows that the valve seat with half-cone-angle of 45° improves the service life of the distribution structure. Performance experiment of a first-generation prototype revealed that pressure can be quickly built up in the plunger chamber at different conditions. Compared with traditional flow distribution mechanism, leakage of the valve flow distribution mechanism is 0.15 ml/min, which significantly improves the volumetric efficiency of the motor. The new flow distribution mechanism works well at high pressure, low speeds, and water-based medium working conditions.

Accurate integrated position measurement system for mobile applications in GPS-denied coal mine

The automatic positioning of underground mobile applications plays a crucial role in enabling intelligent coal mining. However, due to the diverse kinematics and dynamics of these applications, various positioning methods have been proposed to match different targets. Nonetheless, the accuracy and applicability of these methods still fall short of meeting the requirements for field applications. Based on the vibration characteristics of underground mobile devices, a multi-sensor fusion positioning system is developed to enhance the accuracy of positioning in long and narrow global positioning system denied (GPS-denied) underground coal mine roadways. The system combines inertial navigation (INS), odometer, and ultra wide band (UWB) technologies through extended Kalman filter (EKF) and unscented Kalman filter (UKF). This approach enables accurate positioning by recognizing target carrier vibrations and facilitating fast conversion between multi-sensor fusion modes. The proposed system is tested on both a small unmanned mine vehicle (UMV) and a large roadheader, demonstrating that UKF enhances stability for roadheaders with strong nonlinear vibrations while EKF is more suitable for flexible UMVs. Detailed results confirm that the proposed system achieves an accuracy level of 0.15 m, meeting most coal mine application requirements.

Study on green filling mining technology and its application in deep coal mines: A case study in the Xieqiao coal mine

Due to the gradual depletion of shallow mineral resources at present, mines are now gradually entering the deep mining stage. To promote the safe and efficient green mining of deep coal resources and sustainable energy development, and to improve the production efficiency of paste filling mining, the research group has performed this study on the green filling mining technology and application of the working face. Taking working face 1241 (3) of the Xieqiao coal mine as the engineering background, the selection and experiment of filling materials were carried out, and the gangue, fly ash and cement produced by the Xieqiao coal mine were used as the filling aggregate. Next, the strength changes before and after paste filling was obtained by theoretical calculation. The strength at the early stage of filling was no less than 0.13 MPa, and that at the late stage of filling was no less than 2 MPa. Based on previous experimental research and theoretical calculation, the mixing pumping process of paste material ratio and the gangue crushing process were determined, and the filling pipeline system was designed. Then, based on the traditional coal mining technology, a filling mining technology of working face was designed and optimized. The field application of the research results shows that after the goaf of the working face had been filled, the ground pressure behavior of the coal wall of the working face was significantly weakened, and the stability of the surrounding rock of the working face was effectively controlled. Therefore, the method achieved good results, effectively controlled the stability of surrounding rock in goaf, and provided a theoretical basis and data support for realizing safe, efficient and green mining of deep coal resources. The results of this study bear important significance and application value.

Intrinsically Safe Drone Propulsion System for Underground Coal Mining Applications: Computational and Experimental Studies

The mining industry has recently shown increased interest in drones for routine activities in underground and surface mines. Designing a drone for coal mines is extremely complicated since the Mine Safety and Health Administration (MSHA) has tight guidelines for any equipment that can be used in underground coal mines. Due to these criteria, designing a drone for underground coal mining is exceedingly difficult. This paper explores the challenges of creating an intrinsically safe drone propulsion system. To address the challenges of designing an intrinsically safe drone’s propulsion system for an underground coal mine, this work aims to investigate the potential approaches to enhance efficiency and mitigate the heat. The study begins with the drone’s sizing approach before moving on to the experimental setup that is utilized to test the drone’s propulsion system. Finally, answers to numerous issues arising during the inquiry are offered, and these solutions are empirically explored.

Determination of mechanical and microstructure properties of paste backfills to avoid to overburden failure

Backfilling, a widely used technology for green and sustainable underground practice, is an environmentally sustainable engineering approach. This study comprehensively investigates the mechanical properties and microstructural characteristics of backfills maintained underground for three years to avoid overburden failure, considering the static and dynamic mechanical characteristics, creep characteristics, permeability, and microporous structures under dry, natural, and saturated states. The experimental results indicate that the backfill can maintain a high residual stress after peak stress with a very low permeability under triaxial compression. The strength of backfill worked three years under dry, saturated and natural states show a slight difference, indicating a slight water effect on the long-term backfill. The triaxial compression strength of the backfill is greater than the value of stresses in the goaf of panel, indicating that the backfill strength has been achieved an standard value that can support the surrounding rock mass and maintain the stability of themselves in a long term. The porous structure of the backfill show a micro basis for the macro mechanical properties. All the results show that backfills possess the low permeability, strong strength, stable microstructure characteristics under complex environment and indicating an improving function and strength in supporting the surrounding rock mass and maintaining the stability themselves. The findings indicate that the backfills can serve as a useful reference for the control mechanism, waterproof effect, and safety evaluation of the backfill on the deformation of the surrounding rock mass underground. Furthermore, the successful applications show a good verification, indicating a significant practical application in other coal mines with the similar engineering geological conditions, which also contribute to other underground practice.

Optimization of coalbed methane recovery from extraction borehole using novel plastic spraying material: A field application and evaluation

High-quality gas extraction is confronting enormous difficulties due to the leakage of air from the roadway through the coal wall into the extraction system, particularly in the boreholes along the coal seam. In this work, a new set of material and technology for coal wall spraying and sealing was developed to block the air leakage channel and enhance the concentration of extracted gas. The material has excellent air-tightness, resilience, and flame retardancy, and the feasibility of the implementation of the technology was demonstrated by the application in Hexi Coal Mine. The results showed that: the gas-extracted concentration was lower than 10% after 70 days under the conventional borehole sealing method. However, the new material and technology could increase gas-extracted concentration by 26.9∼43.7% with a maximum increase multiple of 4.090 times. Moreover, the average gas-extracted concentration can be increased to 76.7% and maintain a relatively stable state for 80 days. This technology could not only reduce the air leakage, but also strengthen the internal and external pressure difference of the borehole, so that more gas can be extracted at a high concentration, which is expected to provide a reference for the gas disaster control and high-quality gas source guarantee.

Application of Intelligent Sensor in Mining Electrical Equipment Collection

In order to meet the informatization requirements of coal mine safety monitoring, the author proposes a method for the application of smart sensors in the acquisition of mine electrical equipment. The system uses a variety of sensor fusion methods, with the help of Zigbee wireless network nodes, and passes the data collected by the sensor to the MCU core processor; thus, the collected data are processed, and then, the RS-485 communication protocol is used to upload the data to the upper station; finally, the monitoring of coal mine safety is realized through the background monitoring interface. Experimental results show that, among the five randomly selected nodes, most of the errors between the actual measured results and the collected results are concentrated within the 2% error range. Conclusion. The effect of the abovementioned acquisition scheme in coal mine application is verified, so as to realize the scientific monitoring of coal mine safety.

A New Hydraulic Fracturing Instrument to Measure In Situ Stress and Its Application in Chahasu Coal Mine

Abstract Accurate measurements of the in situ stress of the mining area in coal mines are crucial for roadway layouts, support designs, and for coal mining technology selections. Based on the principle of hydraulic fracturing, this study proposes a newly developed instrument, named the instrument for single-loop pneumatic pressurization in situ stress measurements (RBHST-50) and presents its measurement procedures. This instrument boasts four advantages for in situ stress measurements in coal mines: (1) As a safe dynamic in underground coal mines, compressed air provides the driving force of the fracturing fluid; (2) the instrument, which is small and lightweight, can be transported easily from one test point to another; (3) the process of plugging and fracturing is controlled by a simple-loop control system, which avoids the problem of borehole blocking; and (4) the adoption of the integrated impression packer saves the time of conversion between the borehole wall fracturing program and the fracturing impression program, eliminating the error of in situ stress orientation caused by fracture closure. Field investigation was performed in Chahasu Coal Mine in China. The investigation results show that the in situ stress field of Chahasu Coal Mine is dominated by tectonic horizontal stress fields and mainly influenced by the West-North-West tectonic compressive stress, which agrees well with the evaluation results of regression formula. In summary, the proposed RBHST-50 instrument can measure the magnitude and orientation of in situ stress in the coal mine rapidly and accurately while achieving good water plugging capabilities.

Power ultrasound assisted coalbed methane enhancement recovery: Field application and performance evaluation in underground coal mine

Power ultrasonic assisted reservoir modification is a promising technique for enhanced coalbed methane recovery. The current studies confirm the coal structural alteration and the improvement of gas deliverability in coal pores with ultrasound stimulation. However, the in-site performance of ultrasound-assisted CBM production has not yet been revealed. In the current study, the in-situ antireflection test was conducted with high power ultrasound ∼18 kW in underground coal seam, and the antireflection performance was evaluated by measuring the borehole drainage gas data in the field test zone. The result shows, within 40 days’ drainage after ultrasonic antireflection in coal seam, the average gas concentration of single borehole in the experimental group increased by 81.4% ∼ 227.3% than that in control group, the average borehole gas flowrate has a 20% ∼106% improvement over the control group, and the pure methane production in single borehole increased by about 3.83 times. The ultrasonic anti-reflection influence radius exceeds 8 m in the coalseam with water injection in this study, and the increment of methane production in single borehole decreases with the distance increase from the ultrasound source, which is due to the energy attenuation of ultrasound propagation in the porous coalseam. This study preliminarily demonstrates the on-site implementability and effectiveness of power ultrasound in enhancing coalbed methane recovery.

Explosion-proof lithium-ion battery pack – In-depth investigation and experimental study on the design criteria

The catastrophic consequences of cascading thermal runaway events on lithium-ion battery (LIB) packs have been well recognised and studied. In underground coal mining occupations, the design enclosure for LIB packs is generally constructed to be explosion-proof (IEC60079.1 Standard). This, however, in contrast to various investigations that have been performed and conducted to illustrate the inappropriate application of such protection techniques if detailed and thorough analyses of the thermal runaway mechanism and the thermodynamic characterization of the vented gas are well understood. In this article, a thorough experimental and finite element analysis is conducted to illustrate the paramount design parameters and factors that need to be considered for safe operation of large LIB packs, particularly for hazardous environments, in both traction and stationary applications. The outcomes of this investigation provide the deep insight that can evaluate the influential factors when it comes to the design of the battery enclosure and also potentially establishes new guidelines for assessing the integrity of any large-scale battery pack design and construction for various practical applications, specifically for underground coal mining applications.

Superflexible yet robust functionalized carbon nanotube fiber reinforced sulphoaluminate cement-based grouting materials with excellent mechanical, electrical and thermal properties

Fiber-reinforced cement-based grouting material has triggered strong interest owing to its promising application in coal mining. However, how to enable a combined feature of great robustness, exceptional electrical and thermal behaviors, which is crucial for high-performance realization, still remains a significant challenge. Herein, an effective and facile strategy to address the issue was proposed by manufacturing functionalized carbon nanotube (CNT) fibers featuring prominent flexibility, excellent water dispersibility, superior tensile strength and electrical conductivity. Benefiting from the chemical bonds generated between cement hydration product and CNT-COOH fiber effectively embedded into cement matrix, the obtained fiber-cement hybrid with water-cement ratio of 0.8 and 0.5% fiber content was integrated into a whole, with flexural strength (4.8 MPa) and compressive strength (27 MPa) increased by 50% and 30%, respectively, compared to control sample after curing for 28 days. Meanwhile, attributing to the formation of interconnected network architecture built by CNT-COOH fibers in the cement matrix, the hybrid featured a significantly enhanced performance in heat transfer and electrical conductivity, which was further improved under loading. This work has shed light on new strategies for manufacturing carbon-based fiber reinforced cement-based grouting materials with great robustness, prominent electrical and thermal behaviors toward future uses.

The Design and Implementation of AR Glass for Coal Mine Application

Augmented Reality (AR) has been applied in many applications. The key for the AR implementation is the devices or AR glasses. Currently, many companies have published their AR glasses, which could not be directly used in coal mine underground environments. Therefore, in this paper, we propose an improved design of AR glass especially for the coal mine situation. The novel device improves the light projection according to the low illumination in coal mine. Meanwhile, the overall electricity system is enhanced to prevent the fire or explosion. The devices has been applied in the coal mine and the effects are analyzed. Also, the feedback from the users to the new AR glass on the decision support in coal mine is collected for the future improvements.

Laboratory Study of Deformation Behaviour of Two New Reinforcing Polymeric TSLs and Their Potential Application in Deep Underground Coal Mine.

Thin spray-on liner (TSL) is a surface protection technology used by spraying a polymer film, which is widely used for mine airtightness and waterproofing. A reinforcing TSL can replace steel mesh, which is a new method for roadway support. This paper reviews the development of a reinforcing TSL. Considering the deterioration of geological conditions in deep underground mining and the demand for reinforcing automation, two kinds of polymeric reinforcing TSL (RPTSL) materials are developed. The mechanical characteristics of the new TSL materials are studied experimentally. Results show that the average compressive strength, tensile strength, cohesion, and internal friction angle of the two TSL materials are 52 and 32 MPa, 12 and 8 MPa, 6.2 and 17.2 MPa, and 33.6° and 25.9°, respectively. The bonding strength between the two materials and coal is greater than the tensile strength of coal itself, and the mechanical properties of the material for comparison are lower than those of both materials. Based on the TSL support mechanism, we examine the application of the two TSL materials to the mining environment and compare the mechanical properties of polymer materials and cement-based materials. The advantages of polymer materials include versatile mechanical properties, good adhesion, and high early strength. This study provides a new support material to replace steel mesh for roadway surface support, which satisfies the needs of different surface support designs under complex geological conditions, and promotes the automation of roadway support.

Development of New Mean of Individual Transport for Application in Underground Coal Mines

Development of underground coal mines is reflected in increasing lengths of transport routes between shafts and workplaces. This is not an issue in terms of transportation of materials or groups of people, because suspended railways are efficient, safe, and fast mean of transport. However, transportation of individual people or small loads is an issue because of the lack of a means of individual transport and the high cost of transport using suspended railways. The development of individual means of transport, based on historical solutions, utilizes existing equipment of mine workings. This paper presents the stages of development of an underground bike, from the original idea to tests and analysis. The development process consists of simulations of different parameters of the bike using Working Model software and real-life tests conducted in an underground mine. The paper also presents analysis of the legal background of this new means of individual transport.

Experimental study on thermal effect and gas release laws of coal-polyurethane cooperative spontaneous combustion

This paper presents a research on the kinetics and gas release laws of the cooperative spontaneous combustion of coal-polyurethane binary system by means of thermogravimetric analysis and spontaneous combustion simulation experiments. The coal-polyurethane binary system is more prone than individual samples to combustion. The polyurethane mass fraction has a great influence on the cooperative spontaneous combustion process. As the polyurethane mass fraction rises, the activation energies of oxygen absorption stage and pyrolysis stage decrease. The combustion residues of coal-polyurethane binary system scorches into lumps and the surfaces of the particles become rougher. During spontaneous combustion, the initial release temperatures of the four gases CO2, CO, C2H6 and C2H4 drop as the polyurethane mass fraction increases. The gas release amount of them increases with increasing polyurethane mass fraction. And the amount of CH4 decreases as the polyurethane mass fraction increases. The CO/CO2 ratio with temperature for different polyurethane mass fraction have the same trends. The results of this study have implications concerning polyurethane materials application and fire protection in coal mine.