Coal Mine Roadways Research Articles

Control Effect Analysis and Engineering Application of Anchor Cable Beam-Truss Structure on Large-Deformation Roadway in Deep Coal Mine

In response to the shortcomings of the small support scope of single anchor cable and failure to fully utilize the joint anchoring for surrounding rock, this study summarizes the classification of basic support forms for coal mine roadway surrounding rock and clarifies the main composition and mechanism of anchor cable beam-truss structure. A mechanical model of roadway roof beam under the conditions of no support, single anchor cable support, and anchor cable beam-truss structure support at both ends of the roadway is constructed, and the force and maximum bending moment of roadway roof beam under different support types are compared and analyzed. The study clarifies the bending moment reduction rate of anchor cable beam-truss structure relative to unsupported and single anchor cable support and combines numerical simulation to analyze the response laws of anchor cable beam-truss to prestress distribution and stress shell in roadway surrounding rock. Based on the on-site engineering application of a typical large-deformation mining roadway in a deep coal mine, the important role of anchor cable beam-truss structure in ensuring the safety and stability of surrounding rock in deep high-stress and intense-mining large-deformation roadway is revealed, providing technical references for surrounding rock control of similar conditions in deep roadways.

Reinforcement Learning Based Speed Control with Creep Rate Constraints for Autonomous Driving of Mining Electric Locomotives

The working environment of mining electric locomotives is wet and muddy coal mine roadway. Due to low friction between the wheel and rail and insufficient utilization of creep rate, there may be idling or slipping between the wheels and rails of mining electric locomotives. Therefore, it is necessary to control the creep rate within a reasonable range. In this paper, the autonomous control algorithm for mining electric locomotives based on improved ε-greedy is theoretically proven to be convergent and effective firstly. Secondly, after analyzing the contact state between the wheel and rail under wet and slippery road conditions, it is concluded that the value of creep rate is an important factor affecting the autonomous driving of mining electric locomotives. Therefore, the autonomous control method for mining electric locomotives based on creep control is proposed in this paper. Finally, the effectiveness of the proposed method is verified through simulation. The problem of wheel slipping and idling caused by insufficient friction of mining electric locomotives in coal mining environments is effectively suppressed. Autonomous operation of vehicles with optimal driving efficiency can be achieved through quantitative control and utilization of the creep rate between wheels and rails.

Application of Research on Risk Assessment of Roadway Roof Falls Based on Combined Weight Matter Element Extension Model

Roof falls in coal mine roadways are the main causes of many casualties, shutdowns and production plan delays. To understand the relationship between the influencing factors of roadway roof fall accidents and the importance ranking of the accidents, we will reduce safety accidents in coal mines. To enable the timely prediction and control of roadway roof fall risks, based on the investigation of many roadway roof fall risk factors, 12 evaluation indexes such as the roadway roof rock thickness, geological conditions and roadway section shape were selected. An evaluation index system of roadway roof fall risks is constructed. A risk degree standard of roadway roof falls is proposed. The risk evaluation model of roadway roof falls was established by using the combination weight of the analytic hierarchy process (AHP), entropy weight method (EW) and matter element extension theory. According to the principle of the maximum membership degree, the risk degree of roadway roof falls is determined. Based on Java Web, a risk assessment system for roadway roof falls was developed. We name the system Multiple Weight-Material Element Web (MW-MEW). The MW-MEW system was used to evaluate the risk degree of roof falls in the C9 return airway of the Xingu Coal Mine. Compared with the evaluation results of the AHP matter element extension model, it is found that the evaluation results of the MW-MEW system are more in line with the actual engineering conditions. The successful application of the MW-MEW system will provide new avenues for the quantitative evaluation of roof fall risks in coal mine roadways.

Experimental Study on Gas Drainage Through Long-distance Bedding Directional Borehole

In order to solve the problem of gas exceeding the limit in the No.3 coal seam excavation face of Huoerxinhe coalmine, the gas outburst control measure was adopted to pre-evacuate the gas by the long-distance bedding directional borehole. The results show that after 25 days of gas drainage by long-distance bedding directional borehole, the gas content of test point decreased from 13.81m3/t to 7.81m3/t, and the gas pre-pumping rate was about 43.30%. The driving speed of the main transport roadway was 1.48 times that of the traditional ordinary drilling drainage measures, and the tunneling efficiency indicators had not exceeded the standard. Through the application of this measure, it is confirmed that the long-distance bedding directional borehole can effectively reduce the drilling hole construction amount and increase the gas extraction rate, and effectively eliminate the danger of protruding, and realize the safe and rapid excavation of the coal mine roadway.

Method for Pressure Relief in Deep Coal Mine Roadways Using Borehole Groups and Its Application to Guqiao Coal Mine

Abstract With the increase in the mining depth of coal mines in China, the problem of large deformation of roadways owing to high-ground pressure has become prominent even under enhanced support systems. To reduce the high pressure on the surrounding rock, this study investigates a pressure-relief method for deep roadways using drilling borehole groups. Based on a deep roadway in the Huainan mining area of China, the influences of drilling parameters, such as borehole diameter, length, and arrangement were investigated. The results indicate that the fan-shaped arrangement of the borehole group can compensate for the dilatancy deformation of the surrounding rock. The peak stress of the surrounding rock is reduced and transferred to the inner part of the surrounding rock. Furthermore, a field experiment was conducted on an experimental roadway. The deformation of the roadway was monitored and compared with that of an adjacent roadway that did not apply the pressure-relief method. The monitoring results indicated that the deformation of the experimental roadway was significantly reduced.

Roadway rock burst prediction based on catastrophe theory

In order to quantitatively calculate the critical depth and critical load of mines affected by rock burst, and to achieve effective prevention and control of rock burst in coal mines, this paper proposes a mechanical model for predicting the occurrence of rock burst in coal mine roadways based on catastrophe theory. Additionally, a theoretical calculation formula for initiating rock burst is derived. The first step was to establish a mechanical analysis model, which directly correlated with the in-situ stress, physical and mechanical characteristics of the coal-rock mass, and engineering structural parameters. Following this, a mechanical instability criterion was derived for the key load-bearing circle within the surrounding rock of the roadway. In the final step, the critical depth and load for rock burst initiation were verified for 25 distinct coal mines in China that were prone to rock burst hazards. The research results demonstrate that the discrepancy between the theoretically calculated critical depth and the actual measured statistical values was less than 35%. In addition, the difference between the theoretically determined critical depth and the value calculated by Pan Yishan was less than 32%. Notably, the ratio of the theoretically calculated critical load to the uniaxial compressive strength of the coal-rock mass ranged from 0.38 to 1.93. This aligns with empirical data on rock burst occurrences, as set out in the engineering classification standards for rock masses. These research outcomes substantiated the practical utility of the proposed theory, thereby laying a robust theoretical groundwork for the quantitative control of rock burst.

Study on Wind Speed Distribution Law of Mine Roadway Section under Different Conditions

Ventilation is the cornerstone of coal mine safety production, and accurate monitoring of ventilation parameters is the basic guarantee for ventilation technology decision-making. Aiming at the problem that the accuracy of wind speed monitoring in coal mine roadway is difficult to meet the needs of decision-making, this paper studies the position relationship between the average wind speed line and the roadway wall surface by combining theoretical calculation and numerical simulation, and simulates the wind speed distribution law of typical roadway section. The main factors affecting the distribution of wind speed in roadway section include roadway section shape, section size, support form, wind speed, facilities and equipment status, etc. The expression of the position relationship between the average wind speed line of the rectangular and semi-circular arch roadway section and the roadway wall surface is y=elna-1.5. Through 25 groups of model simulation, the wind speed distribution law of different types of roadway sections under different conditions is obtained: the wind speed contour is basically parallel to the roadway wall. The wind speed gradient near the roadway wall is large, and the wind speed gradient in the middle of the roadway is small. The thickness of the boundary layer decreases with the increase of wind speed.

Research on the Anchor-Rod Recognition and Positioning Method of a Coal-Mine Roadway Based on Image Enhancement and Multiattention Mechanism Fusion-Improved YOLOv7 Model

A drill-anchor robot is an essential means of efficient drilling and anchoring in coal-mine roadways. It is significant to calculate the position of the drill-anchor robot based on the positioning information of the supported anchor rod to improve tunneling efficiency. Therefore, identifying and positioning the supported anchor rod has become a critical problem that needs to be solved urgently. Aiming at the problem that the target in the image is blurred and cannot be accurately identified due to the low and uneven illumination environment, we proposed an improved YOLOv7 (the seventh version of the You Only Look Once) model based on the fusion of image enhancement and multiattention mechanism, and the self-made dataset is used for testing and training. Aiming at the problem that the traditional positioning method cannot guarantee accuracy and efficiency simultaneously, an anchor-rod positioning method using depth image and RGB image alignment combined with least squares linear fitting is proposed, and the positioning accuracy is improved by processing the depth map. The results show that the improved model improves the mAP by 5.7% compared with YOLOv7 and can accurately identify the target. Through the positioning method proposed in this paper, the error between the positioning coordinate and the measurement coordinate of the target point on each axis does not exceed 11 mm, which has high positioning accuracy and improves the positioning accuracy and robustness of the anchor rod in the coal-mine roadway.

A Study on the Transient Response of Compressed Air Energy Storage in the Interaction between Gas Storage Chambers and Horseshoe-Shaped Tunnels in an Abandoned Coal Mine

This study focuses on the renovation and construction of compressed air energy storage chambers within abandoned coal mine roadways. The transient mechanical responses of underground gas storage chambers under a cycle are analyzed through thermal-solid coupling simulations. These simulations highlight changes in key parameters such as displacement, stress, and temperature within the chamber group during the loading and unloading processes of compressed air energy storage. It is found that within a cycle, the small circular chamber experiences the most significant deformation, with an average peak displacement of 0.24 mm, followed by the large circular chamber and horseshoe-shaped tunnels. The small circular chamber exhibits maximum tensile and compressive stresses. Therefore, special attention in engineering practice should be paid to the long-term safety and stability of small circular tunnels, and the stability of horseshoe-shaped tunnels should be also carefully considered. The findings from this study offer some insights for theoretical support and practical implementation in the planning, design, construction, and operation of high-pressure underground gas storage chambers for compressed air energy storage.

Research and development of fully enclosed wire-shell support structure technology for deep soft rock roadway based on TRIZ theory

The TRIZ theory was used to accurately discover the problems to be solved in the design of roadway surrounding rock control technology. This paper tried to solve the complex issue of surrounding rock control in deep roadways from a new perspective. Based on the functional component analysis and causal axis analysis of the problem’s primary reason, simultaneously, the surrounding rock control technology was optimized through technical contradiction analysis, physical contradiction analysis, and substance and field model analysis. As a result, a fully enclosed wire-shell support technology was proposed. Finally, taking the typical soft rock roadway engineering of Pansan Coal Mine in Huainan Mining Area, Anhui Province, China, as the engineering background, the engineering application and effect evaluation were completed. This paper provides a reference for controlling the instability of deep soft rock roadways in coal mines. A new idea of optimizing roadway support engineering based on TRIZ theory was proposed.

Study on the propagation characteristics of methane-air explosion under the promotion of crushed gangue

Methane-air explosion is one of the major disasters in industrial process. The explosion strength could be influenced by the crushed coal gangue, which is widely distributed in coal mine gob and roadway. To understand the influence of the coal gangue on gas explosion, an experimental system with a 0.2 × 0.2 × 3.0 m3 pipeline was designed and explosion experiments of coal gangue with 5 blockage length-diameter ratios (ratio of axial blockage length to pipeline equivalent diameter) were carried out. The results show that coal gangue can cause significant disturbances to the flame front, resulting in a violent acceleration of the explosion flame. The overpressure ratio presents a negative exponential function distribution with the blockage length-diameter ratio. The influence range increases with the blockage length-diameter ratio under the condition of rich fuel, and reaches the maximum when equivalent ratio is 1.237. The explosion intensity is more sensitive to the blockage length-diameter ratio for the equivalent ratio equals 1.0 and 1.237. The formation of high-intensity explosion should be avoided by controlling the accumulation state of the overlying rock in coal mining.

Study on failure mechanism and control of surrounding rock of inclined strata crossing roadway in deep coal mine

China’s coal mines are mainly underground mines, and a large number of roadways have to be excavated underground. It is of great significance for coal mine production to adopt safe and reasonable roadway support methods. In the process of roadway excavation, the rock stratum is inclined and the roadway pass through the layer. Since the surrounding rock conditions of the roadway passing through the layer are more complicated, it is easy to cause deformation of surrounding rock, failure and floor heave, which makes the support work difficult. In order to solve this problem, the mechanical properties of roadway surrounding rock were tested and the failure of roadway surrounding rock was analyzed using the +260 horizontal centralized transportation roadway in Changcheng No.2 mine. The surrounding rock of the roadway was divided into 8 regions, and the stress analysis of the surrounding rock in different regions was carried out. It is found that the left shoulder pit, the right side and the floor of the roadway are prone to damage. The influence of the lateral pressure coefficient, the rock dip angle and the lithology on the failure of the roadway surrounding rock was analyzed by Mohr-Coulomb failure criterion, and the specific failure range of the roadway surrounding rock was obtained. The support optimization design of the roadway was carried out, and the weak area of the surrounding rock was reinforced. The deformation monitoring of roadway surrounding rock after support optimization was carried out. The field monitoring results show that after the optimized support, the displacement of the roof and floor of the roadway section and the two sides are reduced by 43.6% and 40.8% respectively compared with the original scheme, and the deformation of the surrounding rock also shows a trend of gradual stability, and the surrounding rock of the roadway is effectively controlled. The research can provide a new way for the stress and failure analysis of the surrounding rock of the inclined rock roadway.

Failure mechanism and strengthening countermeasures of end-anchored cable free section under combined tension and shear

As an effective and economical reinforcement method, end anchorage cables are widely used for roadway support in coal mines. The failure of the free section of the end-anchored cable (FSEC) under the combined action of tension and shear is a key factor inducing roof collapse accidents in coal mine roadways. Based on cable bolt tensile and shear test results, this paper aims to reveal the failure mechanism of the FSEC under tension and shear by establishing a mechanical model of the interaction between the cable bolt and jointed rock mass. The results show that the axial and shear force coupling in the FSEC increases because of the joint plane shear action. The FSEC is subject to tensile–shear failure when the axial and shear forces meet the tensile–shear composite yield condition at the inflection point of the sheared cable bolt. The steel strands of the cable bolt experience and transmit shear force through the contact point, resulting in an uneven distribution of shear stress in the cable bolt cross-section, directly causing the FSEC’s local failure. Strengthening countermeasures are proposed using a high-strength slotted steel pipe to protect the cable bolt under shear, and a strengthening device has also been designed. Experimental results obtained in the laboratory have revealed that the strengthening device does not only effectively enhance the cable bolt’s shear capacity by increasing its shear strength and changing the shear transfer mode, but also significantly improves the cable bolt’s comprehensive performance. This study elucidated the failure mechanism of the FSEC and provides a practical and convenient method for increasing the shear strength of an end-anchorage cable system and enhancing roadway stability.

Monitoring Technology of Surrounding Rock Deformation Based on IWFBG Sensing Principle and Its Application

Abstract To address the challenge of achieving precise real-time monitoring of significant deformation in deep roadway surrounding rock, a quasi-distributed strain-sensing cable (SSC), which has a spatial resolution of 1 m, was developed based on the principle of Identical Weak Fiber Bragg Gratings. The performance of SSC has been evaluated through a series of calibration tests, revealing a range of 0%–3%, an accuracy level of 0.5%, a strain sensitivity measuring at 1.23 pm/με, and a temperature sensitivity recorded as 10.78 pm/℃. Furthermore, a real-time deformation monitoring system has been established to monitor rock deformation, consisting of SSC, supporting installation equipment, demodulation equipment, and monitoring software. Moreover, the proposed methodology was applied in the deep roadway of Guqiao coal mine. The results showed that the maximum surface displacement of the roadway is 103.47 mm, while the lateral contrast error stands at 5%. The maximum strain value of the surrounding rock measures 27,095 με. The depth of rock rupture zone is about 3 m, while the boundary of rock damage zone extends up to 6 m. This information serves as the foundation for determining the parameters of the roadway reinforcement support design.

Experimental and Numerical Simulations of Pore Structures and Seepage Characteristics of Deep Sandstones

Previously conducted studies have established that deep underground rock masses have complex pore structures and face complex geological conditions. Therefore, the seepage problem of such rock masses seriously affects engineering safety. To better explore the seepage law of deep rock masses and ensure engineering safety, indoor experimental methods such as casting thin sections, scanning electron microscopy, and mercury intrusion testing were utilized in this study. The microscopic pore shape, size, distribution, and other structural characteristics of sandstone in coal bearing strata were analyzed. The tortuosity calculation formula was obtained by the theoretical derivation method. And a numerical model was established for seepage numerical simulation research through microscopic digital image methods. The seepage law of surrounding rocks in the Tangkou Coal Mine roadway under different conditions is discussed. The research results indicate that the complexity of the pore structure in porous media leads to an uneven distribution of flow velocity and pressure within the medium. Meanwhile, with the change of physical properties, the fluid flow characteristics also undergo significant changes. The research results can effectively guide micropore water blocking, reduce the impact of groundwater on the environment, ensure the environment and safety of the project, and provide guidance for other geological projects.

Characteristics of fires in coal mine roadways and comparative analysis of control effectiveness between longitudinal ventilation and cross-section sealing

Enhancing ventilation velocity and constructing sealing walls are prevalent strategies aimed at managing fires in coal mine roadways. To assess the efficacy of these control tactics, this study investigates the fire characteristics with varying heat release rates (HRR) using a 1:10 experiment and numerical simulations. Results reveal that an increase in the HRR corresponds to a decrease in ceiling temperature, alongside an increase in both smoke back-layering length and critical velocity. Longitudinal ventilation proves effective in lowering ceiling temperature and inhibiting upstream smoke propagation from fire source, but it does not extinguish the fire, instead reducing downstream visibility and escalating risk downstream of fire. When the actual velocity exceeds 3.1 m/s, it effectively prevents smoke backflow in a fire of 10 MW. Cross-section sealing works by reducing oxygen levels within roadway to suffocate the fire. As the sealing ratio increases, flame inclination angle and burning time decline, whereas ceiling temperature rises. When it exceeds 75%, CO concentration sharply rises and fire enters the extinguishment phase, if ratio is 100%, fire with higher HRR are extinguished more quickly. This study provides valuable insights into roadway fire control: longitudinal ventilation aids personnel evacuation, while cross-sectional sealing effectively extinguishes fires in unpopulated spaces.

Study on Smoke Temperature Distribution Characteristics of Coal Mine Inclined Roadway Fire

ABSTRACT Mine roadway fire is a major natural disaster that threatens the safety of mine production for a long time. 65% of the total casualties of coal mines are caused by mine roadway fire. In order to study the smoke temperature distribution characteristics of inclined roadway fire in coal mine and reduce personnel injury and equipment loss. In this paper, the calculation formula of the maximum air flow temperature and the expression of the maximum temperature on the downwind side of the fire area are presented. Based on the actual roadway of Wusu Coal mine in Hohhot, Inner Mongolia, a “Mine inclined roadway fire simulation experimental system” with similarity ratio of 1:20 is established. The fire smoke temperature under different roadway inclination (5°, 10°, 15°) and different inlet wind speed (0.5 m/s, 1.0 m/s, 1.5 m/s) was tested and analyzed, and the temperature field of inclined roadway during fire was simulated and analyzed by Ansys numerical simulation software. The research shows that when the inlet wind speed is larger or the roadway inclination is larger, the heat diffusion is faster, the temperature field is longer and narrower, and the temperature is lower, but the temperature variation trend of the overall combustion process remains unchanged. By studying the temperature distribution of smoke in inclined roadway fire, it is convenient to take corresponding measures in time to minimize the impact of fire.

Energy evolution mechanism during rockburst development in structures of surrounding rocks of deep rockburst-prone roadways in coal mines

Influenced by the deep high-stress environment, geological structures, and mining disturbance in coal mines, the frequency of rockburst disasters in roadways is increasing. This research analyzed energy evolution characteristics during rockburst development in the elastic bearing zone and energy conversion in the plastic failure zone. The critical energy criteria for structural instability of roadway surrounding rocks were deduced. Numerical software was also applied to simulate the energy evolution during rockburst development in surrounding rocks of rockburst-prone roadways under conditions of different mining depths and coal pillar widths. The occurrence mechanism of rockburst deep in coal mines was analyzed from the perspective of energy in structures of deep roadway surrounding rock in coal mines. The research results show that the critical energy criteria are closely related to the elastic strain energy stored in deep roadway surrounding rocks and the energy absorbed by support systems. The impact energy in roadways is directly proportional to the square of the stress concentration factor k. Moreover, as the mining depth increases, the location of the peak point of maximum energy density gradually shifts to coal ahead of the working face. The larger the mining depth is, the more significantly the energy density is influenced by advanced abutment pressure of the working face and the wider the affected area is. With the increment of the coal pillar width, the distance from the peak point of energy density to the roadway boundary enlarges abruptly at first and then slowly, and the critical coal pillar width for gentle change in the distance is 30 m. Changes in the peak elastic energy density in coal pillars with the coal pillar width can be divided into four stages: the slow increase stage, abrupt increase stage, abrupt decrease stage, and slow decrease stage. The elastic energy density is distributed asymmetrically in deep roadway surrounding rocks in coal mines. Under the action of structures of roadway surrounding rocks, energy evolution in these structures differs greatly during rockburst development under conditions of different coal pillar widths. This research provides an important theoretical basis for the support of rockburst-prone roadways during deep coal mining.

Experimental and numerical studies on the shear mechanical behavior of rock joints under normal vibration loads

Jointed rock masses of roadways in underground coal mines are heavily disturbed by rock-cutting vibrations from Tunnel Boring Machines (TBMs), posing significant challenges in controlling the deformation and damage of the surrounding rock. To investigate the mechanical behavior of rock joints under normal vibration loads, a series of laboratory vibration experiments were conducted with varying frequencies and amplitudes, based on in-situ vibration characteristics during TBM rock-cutting. Subsequently, the relative damage coefficient Dv and relative shear strength ratio Rτ were proposed to quantify the damage degree of rock joints. The findings revealed a non-linear growth of rock joints damage with increasing vibration frequency and amplitude. The vibration frequency and amplitude are categorized into three and two stages, respectively, depending on the damage of rock joints. Additionally, the vibration failure mechanism of rock joints was elucidated using the discrete element method. It was observed that the failure of weakly joints is controlled by both the “filler-rock” interfaces and “filler-filler”, while strongly joints fail solely due to the “filler-rock” interfaces, confirming the agreement with laboratory experiments. Moreover, effective grouting reinforcement was proven to significantly enhance the vibration resistance of in-situ jointed rock masses, preventing vibration collapse resulting from TBM tunneling disturbance.

Research on a Speed Guidance Strategy for Mine Vehicles in Three-Fork Roadways Based on Vehicle–Road Coordination

Aiming at the traffic congestion problem of mining vehicles in the intersection area of three-fork roadways in coal mines, this paper proposes a speed guidance strategy based on a vehicle–road cooperative environment to adjust the running state of mining vehicles in the three-fork roadway system. The proposed speed guidance strategy can realize the safe and effective passage of underground mining vehicles to the greatest extent. Taking a three-fork roadway in a coal mine as an actual case, the operation of mining vehicles in the three-fork roadway is optimized and scheduled. Through the joint simulation of PTV VISSIM 4.3 traffic simulation software and PYTHON 3.7, the travel time, number of queuing vehicles, and delay time of mining vehicles passing through the three-fork roadway entrance under the two conditions of no speed and speed guidance in the coal mine are simulated and compared. The results show that after using the proposed speed guidance strategy for scheduling, mining vehicles can quickly pass through the three-fork roadway intersection. The travel time is reduced by 18.4%, the number of queuing vehicles is reduced by 41.5%, and the delay time is reduced by 24.1%, which effectively improves the transportation efficiency of underground mining vehicles.