Mechanized Mining Face Research Articles

Visual detection of drilling robot position for rockburst prevention in mining processing by a new image dehazing method

AbstractThe positioning of drill pipe based on visual detection is a crucial aspect in achieving unmanned operation of drilling robot for rockburst prevention. However, the images directly collected from mechanized mining face are always polluted. In order to eliminate the interference of dust and haze in the image, an image dehazing method based on improved CycleGAN model is proposed in this paper. Firstly, a pipe image dehazing dataset for the rockburst prevention drilling robot is collected and established. Moreover, a generator architecture with a multi-scale U-shaped network structure is designed to improve the quality and accuracy of image recovery. A new reconstruction block is designed and an SK fusion layer is introduced to improve the feature extraction capability of the model, and a MU-CycleGAN network structure is constructed. Finally, an experimental platform for drill pipe image dehazing of the drilling robot for rockburst prevention is set up in the intelligent mining equipment laboratory. Experimental results showed that the PSNR and SSIM of the image dehazing model achieved 27.04 and 0.946, and the success rate of drill pipe grabbing has increased by 13.75%. Experimental results reveal that the proposed framework achieves superior image enhancement performance than the comparison algorithms.

Spatiotemporal spreading characteristics of dust aerosols by coal mining machine cutting and "partition/multi-level composite field" atomization dust purification technology

To locally atomize the spatial confinement of primary dust generated by the shearer cut-off, the CFD-DPM mathematical model was used to simulate and analyze the wind-borne dust transport law, which resulted in the heavily polluted area of primary dust. A multi-level and multi-dimensional coal machine spray system was developed for the polluted area, its atomization effect was verified by using the TAB breakup model. The results show that the heavily polluted area of primary dust is mainly concentrated in the position of fully mechanized mining face Z=24–39 m area of shearer, and the average concentration is 738.2 mg/m³. The average concentration of droplets generated by the multi-level and multi-dimensional shearer spray system at the shearer drum is 0.66 kg/m³, with a percentage of droplets with particle size between 40 and 160 μm exceeding 85 %. The coverage rate of the shearer drum is 95 %. The relationship between droplet concentration and time is consistent with the Boltzmann function fitting model. Following the implementation of the multi-level and multi-dimensional coal machine spray system in the field, it was observed that the average reduction in dust levels was 90.9 % for total dust and 85.7 % for exhaled dust in the synthesized mining face.

The Construction and Application of a Digital Coal Seam for Shearer Autonomous Navigation Cutting.

Accurately obtaining the geological characteristic digital model of a coal seam and surrounding rock in front of a fully mechanized mining face is one of the key technologies for automatic and continuous coal mining operation to realize an intelligent unmanned working face. The research on how to establish accurate and reliable coal seam digital models is a hot topic and technical bottleneck in the field of intelligent coal mining. This paper puts forward a construction method and dynamic update mechanism for a digital model of coal seam autonomous cutting by a coal mining machine, and verifies its effectiveness in experiments. Based on the interpolation model of drilling data, a fine coal seam digital model was established according to the results of geological statistical inversion, which overcomes the shortcomings of an insufficient lateral resolution of lithology and physical properties in a traditional geological model and can accurately depict the distribution trend of coal seams. By utilizing the numerical derivation of surrounding rock mining and geological SLAM advanced exploration, the coal seam digital model was modified to achieve a dynamic updating and optimization of the model, providing an accurate geological information guarantee for intelligent unmanned coal mining. Based on the model, it is possible to obtain the boundary and inclination information of the coal seam profile, and provide strategies for adjusting the height of the coal mining machine drum at the current position, achieving precise control of the automatic height adjustment of the coal mining machine.

Study of spray atomization law and dust suppression effect of a wet dust catcher on a hydraulic support

To control effectively large dust concentrations and their diffusion during coal cutting and shifting of shearers at fully mechanized mining faces, a wet dust catcher on a hydraulic support was developed. The spray nozzle suitable for wet dust collection devices was optimized through spray experiments, and the effects of the spray pressure Pw and nozzle tilt angle θ on the droplet size and fog field concentration were analyzed with Fluent. The numerical simulation results show that the wide-angle solid cone nozzle (with an X-type swirl core) with a diameter of 2.4 mm, water pressure Pw of 6 MPa, and nozzle tilt angle θ of 10° toward the windward side can form a better water curtain. Finally, the wet dust catcher was applied at a 22104 fully mechanized mining face of the Shangwan Coal Mine. The dust removal rate of the shearer driver reached 86.20 %, and that at other positions reached 85 % on average. Evidently, the hydraulic support wet dust catcher can effectively control the diffusion of coal dust at fully mechanized mining faces.

Research on the optimal design of roadway support for fully mechanized coal seam working face

Abstract For the optimal design of surrounding rock deformation and support in the shallow buried coal seam of large-scale fully mechanized mining face, this paper took the surrounding rock of the roadway as the research object, used theoretical calculation and numerical simulation to establish the mechanical model of the deformation of the surrounding rock structure, and proposed and analyzed the reasonable roadway support scheme of the shallow buried coal seam. The numerical simulation results showed that the top anchor rod with Φ18×2200 mm and the inter-row distance of 1100×1000 mm, the anchor cable with Φ15.24×6300 mm and the inter-row spacing of 2200×2000 mm, the upper part anchor of Φ16×2200 mm, and the C30 concrete with a thickness of 200 mm for laying the bottom plate are selected, which was certified as the optimal support scheme. In practical engineering applications, the deformation of surrounding rock has been effectively controlled, and the supporting effect of surrounding rock was obvious, which was of great significance to ensure the safe production of coal mines.

Extension Mechanism of Water-Conducting Cracks in the Thick and Hard Overlying Strata of Coal Mining Face

It is of great significance for coal safety production and water resource protection in the Yuheng mining area to master the evolution law of water-conducting fractures under the condition of thick and hard overburden. This research focuses on the 2102 fully mechanized mining face in the Balasu Coal Mine as the research background. The fracture evolution and strata movement characteristics in thick and hard overlying strata are simulated and analyzed by combining numerical simulation with physical simulation, and the formation mechanism of a water-conducting fracture in the overlying strata is revealed and verified by field measurements of the development height of “two zones”. The results show that the anisotropy of fracture propagation in low-position overlying strata is high, and the fracture propagation in high-position overlying strata is mainly vertical, which indicates characteristics of leapfrog development. The number and development height of fractures undergo the change–growth process of “slow–rapid–uniform”. Multiple rock strata together form a complex force chain network with multiple strong chain arches. The local stress concentration leads to the initiation of micro-cracks in contact fractures, and the cracks gradually penetrate from bottom to top and then the strong chain arches are broken. The water-conducting cracks in overlying strata show a dynamic expansion process of “local micro-cracks–jumping cracks–through cracks–water-conducting cracks”. The fracture between the caving zone and fracture zone presents obvious layered characteristics, the overall shape of the water-conducting fracture zone is “saddle-shaped”, and the maximum development height lags behind the coal mining face by about 180 m. Through the observation of water injection leakage and borehole TV observation of three boreholes under underground construction, combined with the results of water pressure tests, it is comprehensively determined that the height of the water-conducting fracture zone is 103.68~107.58, and the fracture–production ratio is 31.42~32.60, which is basically consistent with the results of numerical simulation and physical simulation. This research provides theoretical guidance and a scientific basis for coal mine water disaster prevention under similar geological conditions.

A Steady-Pressure Control Method for Emulsion Pump Station Based on Online Updating of Optimal Flow Rate

In order to solve the problem of unstable fluid supply pressure and serious impact caused by the complicated and changeable working condition of a fully mechanized mining face in coal mines and the sluggish response of the fluid supply system to the fluid demand for the hydraulic support, a control method based on online updating generalized regression neural network (GRNN) was proposed. Firstly, the simulated hydraulic support test platform and co-simulation model were built. Secondly, The optimal flow dataset of steady-pressure fluid supply under different working conditions is calculated by simulation. Furthermore, the GRNN prediction model was established by using dataset and online updating learning technology to predict the optimal fluid supply flow according to environmental parameters. Finally, the optimal flow control method of online updating GRNN was established, and numerical research and experimental verification were also carried out in different working conditions. The results indicated that the proposed control method could track the working conditions of the working face in real time and adjusted the fluid supply flow of the emulsion pump station adaptively, which effectively alleviated the pressure fluctuation and pressure shock, and the system pressure was more stable, meeting the demand of steady-pressure fluid supply on the working face.

Optimization of wind-and-water coordinated dust reduction device for coal mine return airway based on CFD technology

High-concentration respirable dust is generated in fully mechanized mining faces, causing health hazards to operators in return airways. To effectively solve this problem, we developed a wind-and-water coordinated dust reduction device. Firstly, the effectiveness of the numerical simulation was validated through spray experiments. Next, the orthogonal experiment method was employed using software such as Fluent and CFD-Post to conduct numerical simulations. This enabled the analysis of the influence of the fan airflow rate (Q), spray pressure (Pw), and nozzle diameter (D) on the coverage capability of the return air roadway and the distribution pattern of the mist field. The results of the numerical simulations indicated that the optimal combination of parameters was Q = 500 m3/min, D = 1.6 mm, and Pw = 5 MPa. Through field application and actual measurement in the return air tunnel of 117 fully mechanized mining face of Jinjitan Coal Mine, the average dust reduction efficiency reaches 91.05%. After dust reduction, the respiratory dust concentrations in the return airway at 20 m, 50 m and 80 m from the air inlet of the return airway are 0.214 mg/m3, 0.172 mg/m3 and 0.153 mg/m3 respectively, which effectively solves the problem of dust pollution in the return airway and reduces dust harm.

Research on Virtual Simulation Experiment Teaching of Scraper Conveyor Condition Monitoring and Fault Diagnosis

The scraper conveyor status monitoring and fault diagnosis virtual simulation experiment system is designed and developed based on the operating environment of the scraper conveyor in the fully mechanized mining face. Using augmented virtual reality teaching resources, through immersive display and interactive operation experiments, students are guided on basis of scraper conveyor mechanical cognition, master the virtual teaching experiment of state monitoring and fault diagnosis such as broken chain monitoring, motor fault classification and identification, reducer compound fault separation, etc. The teaching practice shows that the system can overcome the harsh production environment in coal mines and the risk factors caused by equipment failure, improve students' understanding of the mechanical fault diagnosis technology, and mobilize students' enthusiasm for experiments and initiative to enhance students' innovative ability.

Law of respirable dust pollution induced by cutting-advancing support in a fully mechanized mining face and spatial stereoscopic dust control and removal technology

Law of respirable dust pollution induced by cutting-advancing support in a fully mechanized mining face and spatial stereoscopic dust control and removal technology

Research on the Dust Transport Law in Large Mining Height Fully Mechanized Mining Face

The fully mechanized mining face with high mining height has always been a high-risk area for coal mine dust pollution. In order to further understand the spatiotemporal transport law of dust in the zoning of the high mining height fully mechanized mining face, the 122109 high mining height fully mechanized mining face of Caojiatan Coal Mine was taken as the research object. Numerical simulation method was used to simulate and analyze the dust transport situation of the 122109 fully mechanized mining machine drum single dust source, the hydraulic support moving frame single dust source, and the superposition of all dust sources in forward and backward wind cutting coal. The research results can guide the ventilation layout design in the early stage of the mine and the dust control in the comprehensive mining process, which is of great significance for the construction of safe and green mines.

Research on grouting reinforcement technology of fault crossing roadway in fully mechanized mining face with large dip angle

Research on grouting reinforcement technology of fault crossing roadway in fully mechanized mining face with large dip angle

Influence of Sealing Wall Crack on Gas Migration in Working Face without Coal Pillar Under Gob Connectivity

ABSTRACT Aiming at the problem of gas control in the working face of gob-side entry retention, taking the 97,312 fully mechanized mining face of Shaft No. 2 in Sihe Coal Mine as the research object, combined with numerical simulation and field measurement, the influence of the sealing wall crack on the gas migration rule of the goaf under the state of the adjacent goaf connection is studied. The results show that the simulation results match those measured in the field. The established physical model and numerical simulation model of goaf can better simulate the 97,312 goaf gas migration law. Considering the connection between 97,312 goaf and 97,311 goaf and 97,310 goaf, compared with only considering the connection between 97,312 goaf and 97,311 goaf, the maximum gas concentration difference between 97,312 fully mechanized mining face and 97,224 lane gob-side entry retention is only 0.01%, and the gas concentration has no significant change. Therefore, only the connection of 97,312 goaf with 97,311 goaf is considered. It can meet the demand for research on gas migration law in 97,312 goaf. The connection between 97,312 goaf and 97,311 goaf can well reflect the study of gas migration law in 97,312 goaf. The tightness of the gob-side entry retention sealing wall directly affects the gas concentration in the gob-side entry retention. With the sealing wall’s porosity increasing, the gas concentration in the corner of the return air gradually decreases. In contrast, the gas concentration in gob-side entry retention gradually increases. In order to prevent the gas concentration in gob-side entry retention from exceeding the limit, the porosity of the sealing wall on the side of the gob-side entry retention should be lower than 10%.

Research on Speech Denoising Algorithm for Equipment Trains in Fully Mechanized Mining Working Faces based on CEEMDAN High and Low Frequency Filtering

This paper proposes a high and low frequency filtering denoising algorithm based on Complete Ensemble Empirical Mode Decomposition with Adaptive Noise (CEEMDAN). CEEMDAN to address the issue of noise in speech signals obtained in the environment of fully mechanized mining face equipment trains. This algorithm first decomposes speech signals into multiple Intrinsic Mode Functions (IMFs) in different frequency domains through CEEMDAN, then uses Hilbert-Huang Transform (HHT) to obtain the instantaneous frequency and amplitude of IMFs, calculates the Euclidean distance between IMFs, normalizes it to obtain the average distance between IMFs, and divides the IMFs components into high and low frequency categories based on the average distance. Next, Optimally Modified Log Spectral Amplitude (OMLSA) algorithm and Kalman filtering algorithm are used for the high-frequency and low-frequency IMF components, respectively. Finally, the processed IMF components are reconstructed to obtain a denoised signal. After comparative experiments, the noise reduction algorithm proposed in this paper significantly improves the Signal to Noise Ratio (SNR), Peak Signal to Noise Ratio (PSNR), Mean Square Error (RMSE), and Mean Absolute Distance (MAE) of speech signals obtained in the environment of fully mechanized mining face equipment trains compared to other commonly used noise reduction algorithms.

CM-YOLOv8: Lightweight YOLO for Coal Mine Fully Mechanized Mining Face.

With the continuous development of deep learning, the application of object detection based on deep neural networks in the coal mine has been expanding. Simultaneously, as the production applications demand higher recognition accuracy, most research chooses to enlarge the depth and parameters of the network to improve accuracy. However, due to the limited computing resources in the coal mining face, it is challenging to meet the computation demands of a large number of hardware resources. Therefore, this paper proposes a lightweight object detection algorithm designed specifically for the coal mining face, referred to as CM-YOLOv8. The algorithm introduces adaptive predefined anchor boxes tailored to the coal mining face dataset to enhance the detection performance of various targets. Simultaneously, a pruning method based on the L1 norm is designed, significantly compressing the model's computation and parameter volume without compromising accuracy. The proposed algorithm is validated on the coal mining dataset DsLMF+, achieving a compression rate of 40% on the model volume with less than a 1% drop in accuracy. Comparative analysis with other existing algorithms demonstrates its efficiency and practicality in coal mining scenarios. The experiments confirm that CM-YOLOv8 significantly reduces the model's computational requirements and volume while maintaining high accuracy.

Case study: Noise risk assessment of workers at the mechanized mining face of coal mines

An assessment of workers at the mechanized mining face of coal mines was conducted in China. The survey on the current status of subject exposure to noise of coal miners was administered by occupational health investigation and detailed record of work days. The noise dosimeter measurements of 211 workers were obtained, including coal cutting, supporting, transportation, crushing, and auxiliary (such as air pressure, pump, and maintenance). A total of 56.4% of the LEX,8h exceeded 85 dB(A), and the average 8-hour equivalent sound level of the workers at the mechanized mining face of these coal mines was 91.2 dB(A). Within the noise frequency from 500 to 6000 Hz, there was a “V” shift in the displacement value of hearing threshold. At the noise frequency of 4000 Hz, the hearing loss N50 (dB) of workers reached the maximum. The longer the exposure time, the higher risk both in high-frequency hearing loss and noise-induced deafness. The risk of high-frequency hearing loss reached the high-risk level at 25 years of work, while the risk of noise deafness reached the high-risk level after 30 years of work. In addition, the Pearson correlation coefficient between the noise exposure time and the risk of noise-induced hearing loss was high and positively correlated. The results show that the production noise hazards at the mechanized mining face of coal mine are relatively large. High levels of hazardous noise exposure are typical in coal mines. The noise exposure data can help to develop more feasible noise controls for the employer.

The MMI-HCPS method: Integrating perception-decision-control capabilities of multiple mine inspectors

Due to the complex mining environment, the development of equipment intelligence has stagnated, with challenges in the application of key technologies. Additionally, underground inspectors exhibit a lower level of intelligence in monitoring, decision-making, and control aspects. This paper proposes an MMI-HCPS (Multiple Mine Inspectors- Human-Cyber-Physical System) method that integrates the perception, decision, and control capabilities of multiple mine inspectors. Firstly, it reviews the current status of equipment intelligentization in fully mechanized mining faces to highlight the necessity of equipment intelligentization. Secondly, the paper establishes the theoretical framework MMI-HCPS and further refines the overall structure of the entire document based on MMI-HCPS, composed of high-performance multi-site and multi-device communication network (MCN), intelligent inference system (IIS), inspection-human-system (IHS), and center-human-system (CHS). MCN forms the foundation for the overall architecture to operate smoothly, while IIS, IHS, and CHS constitute the core components driving the operation of MMI-HCPS. Both IIS and CHS have their own monitoring and control subsystems, and their decision subsystems are in a loop with IIS, achieving closed-loop inference. Finally, a utilizing the laboratory environment, separate tests were conducted on the network operation status of MCN, monitoring and control capabilities of IHS and CHS, experimental validation of decision-making abilities of multiple inspectors, and ultimately, an experiment was undertaken to assess the overall inspection process. The results indicate that promoting the intelligence of inspectors in the fully mechanized mining face from an intelligent perspective is feasible with this method. The method achieves a shared perception of the fully mechanized mining face among different inspectors, complementing each other’s strengths and weaknesses, enhancing information processing efficiency, and improving individual work efficiency. Furthermore, the method enables an interactive loop between human, computers, and the physical mining face, providing support for further intelligent development of mining equipment.

Research on the Prevention and Control Technology of Low Oxygen in The Upper Corner of Fully Mechanized Coal Mining Face in Daliuta Coal Mine

In response to the problem of low oxygen in the upper corner of the return air of the 52506 fully mechanized mining face in Daliuta Coal Mine, the impact of atmospheric pressure and temperature changes on the low oxygen in the upper corner of the 52506 fully mechanized coal mining face is analyzed, and the source and cause of the low oxygen gas in the upper corner of the 52506 fully mechanized coal mining face are analyzed from multiple perspectives. A comprehensive treatment method is adopted, including installing windshields and air guide boards at the head and tail ends, joint sealing and leak-repairing at the ground and underground levels, sealing the adjacent goaf communication alleys, pressure ventilation, negative pressure suction, monitoring and control management, etc. This method solves the problem of low oxygen in the upper corner of the 52506 fully mechanized coal mining face.

"Three Zones" Division of Spontaneous Combustion in Goaf of Y-type Ventilation Fully Mechanized Mining Face

The goaf of coal mine is accompanied by residual coal, and the possibility of spontaneous combustion determines whether the mine can work safely. Therefore, the division of "three zones" of spontaneous combustion in goaf under different working conditions is of great significance. This paper takes the 3154 fully mechanized coal face of Longmen Xianan Coal Mine as the research background to explore the "three belts" distribution under the Y-type ventilation mode. Based on the laboratory measured coal related spontaneous combustion characteristic parameters, the division standard of "three zones" is determined. Combined with the daily monitoring of the temperature and gas collection devices deployed on the site and the numerical simulation of the wind speed in the goaf, the comprehensive division of "three zones" in the goaf is realized. The results show that the range of "three zones" divided by temperature is similar to the range of oxygen concentration. The average width of heat dissipation zone and oxidation zone in the transport lane is 34.7m and 48.8m respectively. The asphyxiation zone is located at an average distance of more than 83.4m from the working face; The average width of the heat dissipation zone of the return air lane is 30.6m, the average width of the oxidation zone is 42.7m, and the average distance from the working face is more than 73.3m. In the numerical simulation, the width of the heat dissipation zone of the transport roadway is 35.0m, the width of the oxidation zone is 50m, and the asphyxiation zone is more than 85m from the working face. The width of the heat dissipation zone of the return air lane is 30m, the width of the oxidation zone is 40m, and the asphyxiation zone is more than 75m from the working face. The simulation results are close to the measured range of "three zones" of spontaneous combustion, and the width of "three zones" of return air roadway with Y-type ventilation is obviously different from that of transport roadway.

Research and application of ‘three zones’ range within overlying strata in goaf of steep coal seam

The determination of the ‘three zones’ range within the overlying strata in goaf of paramount importance for effective gas extraction in the goaf and the prevention and control of gas levels exceeding limits in both the working face and the upper corner. Due to the influence of their dip angles, the existing formula used to calculate the breaking boundary angle of the overlying strata in the goaf of horizontal coal seams is no longer suitable for steep coal seams. In response to this issue, the movement law of the overlying strata during the mining of steep coal seams was analyzed and a formula for calculating the breaking boundary angle of the overlying strata in the goaf of steep coal seams was derived. The theoretical calculation formula was applied to the 3,103 fully mechanized mining face of a certain mine in southwest China, and compared and analyzed the results with numerical simulation and on-site measurement using microseismic monitoring technology. The research findings demonstrate that the formula effectively quantifies the ‘three zones’ range within the overlying strata in the goaf of steep coal seams. The ‘three zones’ range in steep coal seams is primarily influenced by factors such as the length of the filling area in the lower part of the goaf, changes in roof lithology, coal seam dip angle, length of the working face, and overburden load. The longer the length of the filling area, the larger the upper breaking boundary angle and the smaller the lower breaking boundary angle of the fracture zone. Based on the research results of three methods, the height of the caving zone in the 3,103 fully mechanized mining face is from 6.93 m to 7.7 m, the height of the fracture zone is from 28.91 m to 34.2 m, the lower breaking boundary angle of the fracture zone is from 40° to 44.5°, and the upper breaking boundary angle of the fracture zone is from 57.7° to 62°. The research results offer robust technical support and theoretical guidance for the determination of the ‘three zones’ range within the overlying strata during the future mining of steep coal seams.