As a core link connecting the physical and virtual worlds, digital twin technology plays a pivotal role in the intelligent transformation of industry. In particular, it provides a new approach for safe and efficient production in the complex operating environments of the coal industry. This paper focuses on the de-velopment status, general key technologies of digital twin technology, and its application in the coal sector (taking hydraulic supports as a case study). First, it sorts out the conceptual evolution and cross-industry application characteristics of digital twin technology, and analyzes the current technical bottlenecks in terms of modeling accuracy, sensing reliability, communication real-time performance, and cross-system compatibility. Second, it systematically expounds the core principles and application status of the general key technologies of digital twin, including technical architecture, geometric modeling, mechanism modeling, communication, monitoring and prediction, and control. Finally, in response to the demands of the coal industry, a digital twin technical architecture for hydraulic supports is constructed, clarifying the physical entity optimization, virtual model construction, virtual-real interaction mechanism, and the whole-life-cycle management and control process. This research can provide theoretical support and technical reference for the practical application of digital twin technology in the coal industry, and con-tribute to the construction of smart mines and the intelligent upgrading of coal mines.

Deep mining represents the future direction of mining technology, with heat hazards in mines being a major factor restricting safe production in deep mines. Conventional cooling technology is difficult to meet the demand for large enthalpy difference cooling in deep mines, and there is an urgent need to develop high-efficiency and low-carbon large enthalpy difference refrigeration systems. This study proposes a mine cooling and heating combined heat pump system, using ethylene glycol solution as a low-temperature coolant to establish a synergistic system for mine airflow cooling and heat supply to surface buildings. By comparing the thermophysical properties, cycling performance and safety of potential refrigerants, this study found that R515B exhibits the best overall performance. This paper constructs a model of a mine cooling and heating combined heat pump system and verifies its reliability. Simulations indicate that for every 1 ℃ increase in the outlet temperature of the ethylene glycol solution, the cooling coefficient of performance improves by 3.8%, while for every 1 ℃ increase in the hot water supply temperature, the heating coefficient of performance decreases by 2.2%. The system significantly improves the underground humid and hot environment, reducing the supply air temperature to 11~16 ℃ in high-temperature, high-humidity mine environments of 28–38 °C and 80% relative humidity. Additionally, it can extract hot water at temperatures of 40~48 ℃.

When large near-horizontal coalfields adopt open-pit mining, the zonal mining mode is usually adopted. The transition and succession issue between the old and new mining areas is crucial to the economic benefits and production stability of the mine. Regarding the issue of turning and succession after the service life of the second mining area of Baorixile Open-pit Coal Mine ends, the research finds that the tight space for dumping, the long distance for stripping and transportation, as well as the challenges that may be faced in the next five years, such as excessively high internal dumping height, excessive transportation distance and increased costs, will significantly affect the overall benefits and sustainable development of the mine. Therefore, this paper focuses on the research of the reasonable transition and turning from the second mining area to the third mining area. By comparing the characteristics of the three turning methods of right-angle gentle side retaining gully, fan-shaped turning and re-pulling gully, combined with the Analytic Hierarchy Process to determine the weights of the four core indicators, the ELECTRE evaluation method is adopted to construct the harmony and disharmony matrix, and the priority level relationship is determined through threshold comparison. The system assesses the applicability of the three steering methods. The results show that the net advantage values of the right-angle gentle retaining ditch, the re-pulling ditch and the fan-shaped turning are 2, 0 and -2 respectively. The right-angle gentle retaining ditch performs the best in the evaluation by the ELECTRE evaluation method and is determined as the optimal choice for the turning in the mining area of Baorixile open-pit Coal mine

Under the "Dual Carbon" goals, the thermal power and coal storage/distribution industries face stringent policy requirements and technical challenges in achieving near-zero discharge and recycling of high-turbidity micro-polluted wastewater. Focusing on an integrated coal storage and power generation project in Jiangxi, this study addresses the limitations of existing systems—such as inadequate treatment efficiency, insufficient non-point source pollution control, and limited capability for graded water reuse—by proposing and implementing an innovative treatment train combining micro-media precipitation with ceramic membrane filtration. The process leverages the "flocculation nucleus enhancement" effect of micro-media to accelerate colloidal destabilization and floc growth, coupled with cross-flow ceramic membrane filtration for precise removal of micro-pollutants. This establishes a synergistic system capable of "rapid coarse-particle separation and precise micro-pollutant control". Operational results demonstrate that the effluent quality consistently surpasses the standards specified in The Reuse of Urban Recycling Water—Water Quality Standards for Industrial Uses(GB/T 19923-2024): suspended solids (SS) remain below 6 mg/L, turbidity under 3 NTU, and chemical oxygen demand (COD) below 15 mg/L. The system achieves SS and turbidity removal rates exceeding 99% and 100% compliance, respectively, along with 79% COD removal. Ammonia nitrogen and total phosphorus are reduced by approximately 30% and 96%, respectively. With a daily treatment capacity reaching 91% of the design value, the ceramic membranes maintain an average flux of 72 LMH, and the backwash interval is extended to 5–6 hours. This integrated process realizes near-zero liquid discharge and high-efficiency recycling of high-turbidity wastewater, reducing freshwater consumption by approximately 600 m3/day. The direct operating cost is estimated at ￥1.04 per cubic meter of water treated, and projected annual savings in water costs amount to approximately ￥736,000 after full-capacity operation. The study provides a technically robust and economically feasible paradigm for wastewater resource recovery in the coal industry, demonstrating significant environmental and economic benefits.

To address the lack of a systematic cognitive model in the intelligentization process of directional drilling construction, a hierarchical knowledge description method is proposed. Firstly, the drilling technology, drilling rig actions, and characteristics of internal modules of the drilling rig are analyzed and identified as the core elements of directional drilling construction, and these elements are layered and defined. On this basis, integrating expert experience and knowledge graph theory, the knowledge representation of drilling technology, drilling rig actions, and characteristics of internal modules of the drilling rig is completed respectively. Furthermore, a knowledge description model for the directional drilling construction process is constructed by coupling the above representations. Practical verification shows that when this method is applied to describe the long-distance drilling construction process at the Baode Coal Mine site, the presented construction process can reflect the technical characteristics and operation rules of the directional drilling construction process. Therefore, the hierarchical knowledge description method and the constructed knowledge model proposed in this paper provide a systematic cognitive framework for the intelligentization process of directional drilling construction and have important engineering application value.

As a part of the green mining technology system, the separation grouting technology can play a importment role in reducing the surface subsidence. In view of the serious problems of surface subsidence under the conditions of fully integrated mining of extra-thick coal seams in Xinjiang, effective measures such as separation grouting should be taken to control them. In this paper, the working face of 1101 of Zhundong No.2 Mine is taken as the research background, the key layers and quantities of overburden are calculated through the theory of key layers, and the possible horizons of the separation are predicted, and then the stable and effective separation space horizon is obtained by calculating the development height of the water conduction fracture zone, so as to determine the separation grouting horizon. Subsequently, according to the migration law of overburden and the development characteristics of separation during the advancement of the working face, the best time for grouting was determined. Then, according to the double integral of the deflection curve of the thin plate under uniform load, the space volume of the separation layer is solved, so as to preliminarily predict the size of the separation grouting amount.Finally, the above calculations are verified based on the results of numerical simulation analysis and the measured microseismic data. It is concluded that the key layer 2 should be selected for the horizon of separation grouting and grouting should be carried out between the mining of the working face and 200m~220m. Finally, it is concluded that the separation grouting volume is about 1.03×104m3. The separation grouting volume calculated from the simulation results is 0.89×104m3, and the error is 13.6%.

Aiming at the engineering problems such as excessive stress concentration and severe roadway deformation caused by the superposition of multi-working face mining in the return airway of the 110 working face of Cuncaota No.2 Mine, this paper adopts the efficient control technology of large-diameter boreholes. Through theoretical analysis of the pressure relief mechanism and combined with FLAC3D numerical simulation, it systematically studies the influence laws of borehole diameter, depth, and spacing on the stress and displacement of the roadway side, clarifies the optimal pressure relief parameters and adjustment directions, and finally verifies the effectiveness of the scheme through engineering practice. The research results show that: (1) After drilling, the stress peak decreases and shifts to the deep part. The pressure relief effect is not obvious when the borehole diameter is too small, while the pressure relief area gradually expands with the increase of borehole diameter. However, the coal wall loses its bearing capacity when the borehole diameter is excessively large, so the optimal borehole diameter is determined to be 0.3m. (2) If the borehole depth is too small, there is no pressure relief effect. As the borehole depth increases, the stress peak decreases and shifts to the deep part, the pressure relief effect is enhanced, and the pressure relief range expands. When the borehole depth increases to 15m, the pressure relief effect no longer improves, and the optimal pressure relief borehole depth range is determined to be 9m~15m (Lp＜Lh≤3.3Lp). (3) With the decrease of borehole spacing, the double stress cores between boreholes gradually evolve into a single stress core, and the stress forms are bimodal (separated state and transitional state), unimodal, and non-peaked in turn, with the displacement between boreholes gradually connected. When the borehole diameter is 0.3m, the optimal pressure relief borehole spacing is determined to be 1.0m~1.6m (2X0≤L2≤2X0＋2D). Engineering practice verification shows that after pressure relief using the optimized parameters, the roadway stress tends to be stable, and the convergence of the roof and floor as well as the two sides decreases by 86.15% and 86% respectively, solving the core engineering problems of excessive stress concentration and severe roadway deformation. The research results provide scientific support and engineering reference for the control of similar high-stress roadways affected by mining superposition.

In response to the challenges of large deformation and control of surrounding rock in system roadways subjected to strong mining-induced stress superposition during deep multi-seam mining, this study takes the system roadways in the West Third 8-coal seam district of Pansan Mine as the engineering background. Through field investigation, mechanical testing, numerical simulation, and industrial trials, the deformation mechanism of the roadway surrounding rock was systematically investigated, and a "coordinated pressure relief and support" control technology was proposed. Research indicates that the intense superposition of stresses from the overlying goaf and the current mining operations results in a stress concentration factor of up to 2.19 and a peak stress of 37.3 MPa in the surrounding rock. Concurrently, the continuous expansion and interconnection of the plastic zones cause the width of the elastic core between roadways to drastically reduce to approximately 10 m, which is the fundamental cause of severe deformation and instability. Based on this mechanism, a control technology centered on "stress field optimization" and "structural stability control," namely "coordinated pressure relief and support," was proposed. Field application verification shows that this technology can reduce the peak stress behind the roadway by 28.24 MPa, a decrease of 40%. The deformation rate of the surrounding rock was significantly reduced from 3.85–4.01 mm/d, with the maximum deformation controlled within 80 mm, ensuring a stable service period of 4–5 months for the roadways. This provides an effective approach for solving stability control problems of roadways under similar conditions.

Regarding the issue of determining the reasonable width of flexible formwork walls along the goaf of shallow buried coal seams. Taking the 22103 working face of Liuta Coal Mine as the engineering background, this study adopts theoretical analysis, numerical simulation, and on-site industrial testing methods to determine the reasonable width of flexible formwork walls for shallow buried coal seam along the goaf. The results show that under shallow burial conditions, the reasonable width range of the flexible formwork wall along the goaf is 0.8-1.6 m, and as the width of the formwork wall increases, the bearing capacity of the flexible formwork wall gradually increases, and the deformation of the surrounding rock of the roadway gradually decreases; When the width of the flexible formwork wall reaches 1.2 m, the bearing capacity inside the flexible formwork wall increases significantly, and the subsidence of the roadway roof, the bulging of the bottom, the lateral movement of the flexible formwork wall, and the lateral movement of the coal wall also decrease significantly, effectively reducing the deformation of the surrounding rock system along the goaf and meeting the safety production needs of coal mines. On site industrial tests have shown that a reasonable width of the flexible formwork wall has a significant effect on controlling the stability of the surrounding rock along the goaf.

Taking the 3-1 coal 31305 working face of the Shendong Shigetai Coal Mine as the research object, this study systematically explores the dynamic evolution mechanism of energy convergence and dispersion in the main retreat roadway during the final mining stage of a fully mechanized mining face. Through mechanical and energy method hypotheses, Flac3D numerical simulations, and acoustic emission physical similarity simulation phenomena, the energy evolution perspective is used to deduce the energy convergence and dispersion mechanism of the main retreat roadway in the final mining stage. Meanwhile, based on the bearing state conditions of the residual coal pillars, the energy evolution process of the main retreat roadway is divided into the "large" coal pillar bearing stage and the "small" coal pillar instability stage. The research results show that: (1) Using the ultimate bearing capacity of the residual coal pillars in the final mining stage as the criterion, a corresponding relationship with the width is established to distinguish between the stable bearing stage and the stage; (2) The amount of energy transferred from the residual coal pillars to the coal pillars in the main and auxiliary retreat roadways accounts for 59.24% of the energy in the roadway coal pillars, and the boundary between the "large" coal pillar bearing stage and the located 5 meters from the working face to the main retreat roadway; (3) During the "large" coal pillar bearing stage, energy is transmitted from the working face along the coal-rock mass and accumulates in the surrounding rock of the main retreat roadway, whereas in the "small" coal pillar instability stage, energy dissipation and instability intensify on the side of the residual coal pillars in the main retreat roadway, with the core area of energy accumulation shifting to the side of the roadway coal pillars.

Abstract：Addressing the challenge of preventing dynamic-static coupling disasters during deep high-gas coal seam mining, this study investigates gas-stress coupling mechanisms to evaluate mining pressure hazards in the No. 3 coal seam at 700m depth in the Zhao Zhuang Mine. Through a combined approach of laboratory experiments, in-situ stress testing, and numerical simulation, this study reveals the weakening effect of gas adsorption on coal strength and establishes an integrated dynamic-static mine pressure hazard assessment system. Experiments demonstrated that the uniaxial compressive strengths of coal samples under gas pressures of 0 MPa, 1 MPa, and 2 MPa were 9.838 MPa, 9.254 MPa, and 8.338 MPa, respectively, confirming that the combined action of adsorbed and free gas leads to deterioration of coal strength. Field in-situ stress testing revealed the maximum horizontal principal stress direction as N36.67°W, aligning with the regional tectonic stress field orientation. This dominant horizontal stress significantly exacerbates roadway deformation risks. Based on three-dimensional in-situ stress inversion and dynamic excavation simulation, stress concentration zones ranging from 10 to 66.1 MPa were identified in the Zhao Zhuang Mine 1311 working face during the initial excavation phase (150-350 m), secondary excavation phase (415-655 m), cyclic pressure phase, and final mining phase (100 m ahead of the retreating support passage). Through comprehensive multi-factor coupling analysis, an evaluation method incorporating key indicators such as geological structures, face-out effects, and coal pillar zones was established, dividing the working face into four medium-risk and four general-risk zones. A targeted integrated prevention plan combining “roof directional fracturing + shaped charge blasting + controlled-rate mining” was proposed. This involved drilling 433 roof hydraulic fracturing holes, 317 shaped charge blasting holes, and 1,542 large-diameter pressure-relief holes. The research findings elucidated the mechanism of mining pressure-induced disasters in deep gas-bearing coal seams, establishing a technical framework encompassing “experimental research-in-situ stress inversion-dynamic evaluation-zonal prevention and control.” This achievement provides theoretical support and practical reference for preventing dynamic disasters in mines with similar conditions.

With the increase of coal mining depth, the risk of strong mineral pressure and composite dynamic disaster faced by deep coal seam mining is significantly aggravated. Aiming at the prevention and control of strong mineral pressure disaster induced by superposition of multiple working faces in deep coal mines, the engineering background of Zhaozhuang Mine is the three times square area of 1311 working face (strike 698-938m), and the dynamic evolution law of the quarry perimeter rock structure and the disaster mechanism of strong mineral pressure are revealed through the integration of microseismic monitoring, stress on-line monitoring, bracket resistance analysis, and fissure development observation and other multi-source monitoring means. The study shows that: ① microseismic events in the vertical - tendency of the “arch” type distribution, the scope of activity is concentrated in the coal seam above 60m, the most intense activities in the middle of the working face roof; ② the influence of the over-supporting stress range of up to 150m, the value of the stress is growing with the advancement of the working face, the section of the coal pillar with the work face near the first increase in the stress is shown, Subsequently, the stress in the coal pillar is maintained at a high level, and after the monitoring point enters the hollow area, the concentration of coal pillar stress is slowly reduced; ③The working face shows the characteristic of “upper big and lower small” pressure, the average step distance of the upper measurement area is 10.96m (the dynamic load coefficient is 1.28), and the step distance of the lower measurement area is shortened to 10.08m, and the dynamic load coefficient is increased to 1.34, which reveals that the lower part of the working face has a very intense stress. 1.34, revealing that the risk of strong mineral pressure in the lower area is significant; ④ After the implementation of directional hydraulic fracturing of the roof plate and energy blasting, the fissures on the roof plate of the roadway are concentrated in the 11-27m level, which reduces the integrity index of the roof plate, thus effectively blocking the path of stress transmission; ⑤ The monitoring of the deeper delamination reveals that the amount of peripheral rock delamination is significantly larger than that of the shallower part of the 9m range, which verifies the collapse of low rock layers as the main reason of the disaster caused by the dynamic loading. The study proposes the theory of “static-dynamic dual source”: the static load environment formed by the over-supporting stress and the dynamic load disturbance triggered by the development of fissures in the low rock layer, the expansion of the off-layer, and the collapse of the low rock layer form the composite conditions for the disaster. The research results provide theoretical and technical support for the prevention and control of deep composite dynamic disasters.

During the opposite-direction mining process of adjacent working faces, air leakage from neighboring goaf areas complicates the identification of coal spontaneous combustion risk zones in composite goafs. This study employs a combined approach of numerical simulation and field measurements to investigate the evolution patterns of coal spontaneous combustion risk zones in composite goafs before and after the convergence of adjacent opposite-direction mining faces. The research analyzes the influence of coal pillar porosity and working face pressure differentials on the distribution of coal spontaneous combustion risk zones. The results indicate that prior to face convergence, the maximum oxidation heating zone widths in the goafs of faces 2201 and 2206 were 39m and 37m, respectively. Following face convergence and intersection, with increasing coal pillar porosity, the oxidation heating zone width in the central and return air side of the 2206 goaf increased by 66m, while the spontaneous combustion risk zones on the intake air side of both 2201 and 2206 goafs decreased. Under increasing negative pressure differentials, the oxidation heating zone width in the 2201 goaf showed a slight increase, while the maximum width of the oxidation heating zone in the return air side and central area of the 2206 goaf reached 97m, with the risk zone area increasing by 48% for each doubling of negative pressure differential. With increasing positive pressure differentials, the oxidation zone width on the intake air side and central area of the 2201 goaf expanded, while both the cooling and oxidation zones in the 2206 goaf showed expansion trends. For each doubling of positive pressure differential, the oxidation heating zone width on the intake air side of the 2201 goaf increased by 69%, and the coal spontaneous combustion risk zone area in the 2206 goaf more than doubled. These findings provide valuable references for determining coal spontaneous combustion risk zones and formulating fire prevention strategies in similar goaf conditions.

Aiming at the challenges of low coalbed methane (CBM) extraction efficiency caused by significant permeabil-ity differences in soft-hard interbedded coal seams and poor adaptability of conventional fracturing technolo-gies in China, this study focuses on the No. 3 soft-hard interbedded coal seam in the Jincheng mining area. A "geology-engineering integration" development concept is proposed, and an innovative staged fracturing tech-nology for horizontal wells with uncemented casing outside the coal seam is developed. By adopting a tub-ing-annulus co-injection fracturing process (injection rate: 8.0–9.0 m3/min, proppant concentration: 6–8 m3/m), combined with self-developed expandable packers (pressure resistance: 70 MPa), sand-control hydraulic an-chors (tensile strength >200 kN), and high-displacement hydraulic jetting-fracturing integrated tools, a "perfo-ration-fracturing" collaborative mode is established to achieve balanced staged stimulation of soft and hard coal layers. Field tests demonstrate that the single-well daily gas production exceeds 5,000 m3, the gas contri-bution rate of soft coal seams increases to 35%, and the gas content reduction reaches 24.2% after two years of extraction. Additionally, the construction cost is reduced by 100,000 yuan per stage, with a 30% improvement in efficiency. This technology effectively resolves issues such as wellbore instability and coal fines blockage, significantly enhances pressure relief volume and extraction efficiency, and provides technical support for coal mine gas hazard prevention, large-scale CBM development, and green mine construction under the “du-al-carbon” goal.

Abstract: In order to study the overall destabilisation mechanism of coal columns generated by the intersection of deep shafts, the coal columns generated by the cutting of the intersection roadway of Shandong Xinhe Coal Mine-980 level are taken as the engineering background, and the stress evolution characteristics of coal columns under the control of the synergistic deformation of coal columns-roof plate are studied in depth by means of on-site monitoring and theoretical research, and a mechanical estimation model under the synergistic deformation of coal columns-roof plate is established. The mechanical estimation model under the coordinated deformation of ‘coal pillar-roof plate’ is established, and the preliminary mechanical criterion of coal pillar instability is obtained. The study shows that: 1) under the superposition of large mining depth, overburden subsidence and clamping, the coal pillar ruptures due to the long-term creep state, and its platform-type stress distribution can be regarded as the main feature of the coal pillar in critical stability; 2) under the action of high stress, the coal pillar in the deep shaft guarding lane produces creep deformation and the elastic core area corrodes continuously, and it is easy to induce the instability shock once the elastic core area of the pillar is eroded to the critical width; 3) the analysis of the influencing factors shows that the instability shock is easily triggered by the ‘coal pillar-roof plate’ cooperative deformation model. (3) The analysis of the influencing factors shows that the average stress of the coal pillar in the deep shaft protection channel is proportional to the axial load on the roof plate and the elastic modulus of the coal body, and inversely proportional to the width of the coal pillar. The research results have certain guiding significance for the prevention and control of deep coal pillar-type impact ground pressure.

This article takes the strong impact working face of the thick and hard roof slab in Hujiahe Mine as the engineering background to address the problem of easily induced rockburst. By comprehensively using theoretical analysis, on-site monitoring and other research methods, the mechanism of thick and hard roof slab induced impact is revealed, and a criterion for the initiation of thick and hard roof slab impact is established. The downhole directional long drilling segmented hydraulic fracturing technology is proposed, and the spatiotemporal response changes of microseismic in the fractured area and non fractured area are compared and analyzed to verify the anti impact effect of regional fracturing load reduction. The results indicate that the "F-shaped" suspended roof structure formed by the thick hard roof covering the working face serves as the source of dynamic and static load supply, providing a path for inducing impact initiation; The fracturing of the thick and hard roof in the area has caused it to lose the load conditions that trigger impact initiation, hindering the path of impact initiation; The release of microseismic events has shifted from "high energy and low frequency" to "high frequency and low energy" forms. In the un fractured area, microseismic events with energies of 102-103J are the main ones, accounting for about 60.3%, while in the fractured area, microseismic events with energies less than 102J are the main ones, accounting for about 46.2%; The average energy and energy released per meter in the fracturing area are at a relatively low level and have stable changes. The concentrated impact of mining is far away from the working face and reduces the degree of mining influence. The regional fracturing has a good effect on load reduction and anti-collision.

To solve the problem of strong mine pressure in the free roadway under the condition of hard roof in extremely thick coal seam, taking the 4305 working face of Yangcheng Coal Mine of Jinan Mining Group as the engineering background, a joint "blasting pre-splitting-large diameter drilling" pressure relief technology for hard roof in thick coal seam was proposed. Through a combination of theoretical analysis, numerical simulation and on-site monitoring, the evolution laws of surrounding rock displacement and stress under different joint pressure relief technical parameters are studied. The results indicate that based on key stratum theory, the target blasting layers were identified as 15.1 m fine sandstone located 2.0 m above the coal seam and 10.6 m fine sandstone at 37.6 m above the coal seam, with pre-splitting heights of 17.1 m and 48.2 m, respectively. The blasting angles were determined as 83° and 87° on the goaf side, and 38° and 66° on the solid coal side. Using Flac3D to analyze the displacement and stress changes in surrounding rock of roadways under different combined pressure relief technical parameters, the optimal solution was determined as follows: drilling holes of φ250 mm×30m arranged at a spacing of 3m, combined with differentiated blasting angles, resulting in a maximum roof displacement reduction to 3.55 cm and a peak vertical stress controlled below 6 MPa. This approach established a three-dimensional pressure relief system characterized by "deep-shallow synergy and layered fracture." Field comparisons between the pressure-relief zone and the non-pressure-relief zone showed that the combined pressure relief technology significantly reduced the convergence of the roof and floor, and two sides of the roadway. The combined pressure relief technology effectively enhanced the stability of the surrounding rock in the gob-side entry, providing a theoretical basis and engineering application support for the prevention and control of rock pressure disasters under conditions of extra-thick coal seams and hard roof strata.

In order to reduce the number of equipment regulation in the existing resistance calculation algorithm and realize the real-time online calculation of roadway resistance, firstly, according to the actual situation of mine ventilation system, the type of resistance alteration and its key characteristics are analyzed, and the feasibility of the design idea of resistance calculation algorithm based on resistance alteration is established. Secondly, a node pressure sensor placement algorithm based on the minimum vertex coverage theory is designed, and it is proved that the ventilation network can be divided into linear subnet and star subnet. Then, based on the ventilation subnet as the basic unit, combined with the real-time air volume of the roadway, a real-time online measurement resistance theory based on resistance alteration is proposed. Finally, taking the ventilation system in some areas of Sihe Coal Mine as an example, a simulation experiment was carried out. The results show that the proposed theory and algorithm can control the absolute value of the relative error of the resistance of a single roadway to about 5%, and the average absolute error of the resistance of all roadways is 0.1468%, which effectively reduces the number of equipment regulation and improves the real-time calculation of the resistance of the roadway.

To grasp the air leakage characteristics of pressure relief boreholes in deep mining and the key areas of coal spontaneous combustion prevention, combined with the actual situation of the production site, the influence range of air leakage of pressure relief boreholes was theoretically analyzed. The penetration of vertical cracks between pressure relief boreholes and roadway sides was tested by SF6 tracer method, and the air leakage rate of cracks between pressure relief boreholes was calculated, and a targeted coal spontaneous combustion prevention and control method was proposed. The results show that the pressure difference between the inside and outside of the pressure relief borehole is 11.84~20.51 Pa, which provides the driving force for the seepage and diffusion of oxygen from the roadway to the fracture zone of the borehole, and is the key factor leading to air leakage. There is a phenomenon of air leakage through the vertical cracks around and in the borehole. The direction of air leakage between the boreholes is consistent with the air flow in the roadway. The average air leakage rate on the wind side under the release point is 0.0041~0.0166 m/s. Aiming at the air leakage characteristics of pressure relief boreholes, a comprehensive coal spontaneous combustion prevention and control method is proposed, which includes “two plugging and one injection” sealing method to reduce the direct air leakage between boreholes and roadways, segmented gel injection to isolate the air leakage channel between boreholes, and roadway side grouting to block the air leakage of vertical fractures. The oxygen concentration in the borehole is maintained at 0.87%~6.71% for a long time, which effectively blocks the air leakage microcirculation and achieves the effect of coal spontaneous combustion control. This study will provide a reference for the prevention and control of coal spontaneous combustion in deep mining pressure relief boreholes.

To comprehensively evaluate the benefits of intelligent transformation of coal mining and excavation systems, this paper constructs an index system of influencing factors of intelligent transformation benefits from three dimensions: economy, safety and environment, and determines the index weights by using the analytic hierarchy process. On this basis, a system dynamics model is established by using the basic inflow tree method, and the dimensional differences among multiple benefit indicators are eliminated through standardization processing. The model is verified with the actual transformation data of Shendong mining area, and the error rate is less than 10%. Further, the causal chain tracking and sensitivity analysis are used to identify the action paths of intelligent transformation on benefits, and the Monte Carlo simulation is adopted to quantify its impact degree. The orthogonal test method is introduced to evaluate the robustness of the system. The research results show that intelligent transformation significantly improves the comprehensive benefits of the mining and excavation system through three key paths: economy, safety and environment. Even under the fluctuations of basic failure rate, coal price and energy consumption per ton of coal, its comprehensive benefits are still better than those of the untransformed system, and the benefit growth trend becomes more significant with the deepening of the transformation degree, demonstrating good robustness.

Existing mine tunnel field strength prediction models are often complex, have low accuracy, and lack strong generalization. To overcome these challenges, this paper presents a CNNSE-based path loss prediction model for mine tunnels. The model considers factors such as antenna frequency, tunnel wall roughness, and humidity as input features, with path loss as the output, allowing for accurate path loss predictions. The approach incorporates the SE module and multi-scale dilated convolution to improve the model’s ability to capture electromagnetic wave propagation patterns in complex environments, enhancing its attention to crucial features. PGD adversarial training is also used to boost the model's generalization, ensuring robust and accurate predictions in mining conditions. Experimental results indicate that the model achieves an average absolute error of less than 0.5 dB and a correlation coefficient of 0.9969, demonstrating significant improvements in both prediction accuracy and generalization.

In order to solve the problem of asymmetric large deformation control of coal and rock roadways widely distributed in Guizhou mining area, based on digital image correlation technology ( DIC ), the macroscopic mechanical response and deformation data of the whole process were collected synchronously. Through the digital image full-field strain analysis and macroscopic stress-strain response comprehensive characterization, the uniaxial compression test of unanchored coal-rock combination specimens under different coal-rock interface dip angles, height ratios and strength ratios was carried out. The results show that the evolution of DIC strain field clearly presents the whole process of time-sharing fracture of ' coal strain concentration → coal main fracture → stress transfer → rock mass lag failure '. The increase of the dip angle of the interface enhances the shear slip component of the interface, which makes the fracture mode gradually shift from coal crushing to interface slip. The coal-rock height ratio affects the timing characteristics and damage severity of time-sharing fracture by regulating the dominance of coal in the structure and the constraint effect of rock mass. The strength ratio of coal rock is the essential factor driving time-sharing fracture. The larger the difference is, the more significant the time-sharing fracture sequence is, and the more obvious the time difference is. The above research results further reveal the time-sharing fracture evolution law and formation mechanism of unanchored coal-rock combination under uniaxial compression load, and provide a theoretical basis for the control of surrounding rock of coal-rock roadway.

Abstract：Addressing the issues of coal slime accumulation and water-blocking effects in hydraulic permeability enhancement technologies for high-stress soft coal seams, where newly formed fractures tend to close rapidly resulting in inefficient gas drainage, this study investigates the damage characteristics and fracture propagation patterns in soft coal subjected to directional expansion fracturing based on water-free fracturing technology. The research analyzes the relationship between fracture length and expansion force, along with fracture extension patterns under different guide borehole layout parameters. Experimental results demonstrate that multi-borehole fracturing achieves superior performance compared to single-borehole operations. Under 30 MPa expansion pressure, the developed fracture length reaches approximately 1.5 m. Optimized guide borehole arrangement at 1.3 m from the expansion hole significantly improves terminal fracture development.

The application of hydraulic fracturing technology in addressing the hard roof strata of coal mines can effectively reduce the working fracturing step distance and mitigate fracturing intensity, thereby decreasing the risk of impact-induced disaster accidents. To investigate the propagation patterns of fractures during the hydraulic fracturing process, this study examines the influences of various factors, including water injection pressure, displacement, in-situ stress, and tensile strength of the surrounding rock on fracture evolution through numerical simulation methods. The findings indicate that during the fracturing process, fractures initially develop along the direction of the maximum principal stress. As the injected fluid continues to exert pressure, fractures progressively expand in multiple directions, forming a complex fracture network structure. Higher water injection pressure, moderate displacement, and significant differential ground stress promote rapid crack expansion. Moreover, tensile strength plays a critical role in crack propagation. When tensile strength is low, cracks propagate unidirectionally. However, as tensile strength increases, crack propagation exhibits greater diversity in directionality. These research outcomes provide a crucial reference for the practical implementation of hydraulic fracturing technology in mitigating coal mine impact disasters.

Addressing the issues of low efficiency in manual adjustment of process parameters (such as powder removal volume and separation density) in the de-powdering screening and dense medium separation stages of coal preparation plants, which lead to significant fluctuations in product quality, this study proposes an intelligent decision-making and collaborative control method for the coal separation process based on the multi-objective Whale Optimization Algorithm (WOA). The method innovatively extends WOA into a multivariable optimization framework, constructing a composite fitness function to balance ash content deviation, clean coal yield, and process constraints, thereby achieving automated parameter adjustment. Using a coal preparation plant in Jincheng, Shanxi, as a case study, an ash content-yield prediction model is established by integrating historical production data and sink-float tests. Experimental results demonstrate that, compared to manual adjustment, WOA reduces the average ash content deviation (the average deviation between actual and target ash content) from 1.5% to 0.85%, increases the clean coal yield from 38.82% to 41.73%, and improves the calorific value qualification rate from 56.0% to 85.0%, significantly reducing quality surplus and nearly eliminating unqualified products. In comparison with Particle Swarm Optimization (PSO), WOA shows superior performance in terms of ash content deviation, clean coal yield, and calorific value qualification rate; at the same time,validation using subsequent production data confirms its generalization ability. This method provides theoretical support and practical reference for the intelligent optimization of coal preparation processes, demonstrating the effectiveness and robustness of WOA in addressing multivariable, nonlinear industrial problems.

Abstract: The safety evaluation of coal supply and demand can analyze the dynamic relationship between supply security and demand fluctuations, enhance the risk prevention and control capabilities of resource-based cities, and ensure the stable operation of the energy supply system. To establish a regional safety evaluation system for the coordinated coal supply and demand in Guizhou Province, the AHP-entropy weight method (EWM) is adopted to calculate the comprehensive weights of the evaluation factors and determine the main control factors for safety evaluation. Thirteen indicators are selected from the aspects of supply capacity, reserve system, transportation and sales channels, and government guarantee measures. A coal supply and demand safety evaluation model with the logical framework of "multi-dimensional indicator selection - combined weight calculation - spatial zoning - measure response" is designed. The K-Means clustering algorithm is used to determine the safety distribution from the city of Bijie (point) to the whole province (area) in Guizhou Province. The research results show that the main control factors affecting the supply and demand in the resource output city of Bijie are the proven coal reserves, production level and railway shipment volume, with weight proportions of 20.68%, 15.36% and 11.24% respectively. The "large supply, small demand" industrial structure and the increase in clean energy consumption in Bijie have effectively reduced the dependence on coal demand, and the coal supply and demand safety is high. Based on the comprehensive score of the indicators' weights of each city (prefecture) in Guizhou Province, three types of safety areas are classified, and differentiated response measures are proposed, providing a reference for the supply and demand safety assessment of resource-based cities.

Backfill mining serves as an effective method to mitigate mining-induced pressure, control strata movement, and reduce surface subsidence in underground coal extraction. This paper elaborates the operational mechanisms of backfill hydraulic support. Based on strata movement characteristics in backfill mining and 8 typical overburden load patterns, equilibrium equations for the roof beam of six-columns backfill hydraulic supports are established. To investigate the fatigue characteristics of the six-leg backfill hydraulic support base, mechanical theoretical models for both the complete support structure and the base were established. Strength analysis of the base was conducted using the finite element method, revealing stress concentration locations and corresponding stress values under critical operating conditions. Based on the strength analysis results, fatigue life, fatigue damage, safety factor, and fatigue sensitivity analyses of the base were conducted using the Fatigue Tool. The results indicate that the base exhibits multiple stress concentrations under torsional loading conditions. These stress-concentrated areas demonstrate shorter fatigue life, higher fatigue damage, and lower safety factors, making them particularly prone to fatigue failure. The research results provide theoretical references for enhancing the service life of backfill hydraulic supports, thereby mitigating rockburst risks in roof strata and improving backfill mining efficiency.

Compacted strand wire ropes have higher breaking force and longer service life compared with ordinary wire ropes, and they are gradually applied in deep hoisting systems. This paper studies the stiffness characteristics of compacted strand wire ropes and ordinary wire ropes based on Costello's wire rope theory, and a dynamic model of the multi-rope friction hoisting system is established using the first kind of Lagrange equation. The numerical calculation results show that: ordinary wire ropes and compacted strand wire ropes are subjected to the same tension during the operation of the system, but the maximum amplitude of the ordinary wire ropes is about 50% larger than that of the compacted strand wire ropes. Compacted strand wire ropes have much smaller static torque and dynamic torque than ordinary ones, with a difference of 10 times between the two. Compared with ordinary wire ropes, compacted strand wire ropes have better anti-torsion mechanical properties and possess absolute advantages when applied to ultra-kilometer vertical hoisting systems.