The underground extraction of coal resources can induce surface subsidence, posing a potential threat to both the ecological environment and the structural stability of buildings. Anticipating the dynamic subsidence values prior to mining is crucial for establishing a foundation for dynamic restoration designs in mining subsidence areas. This represents a pressing concern within the field. In order to precisely predict the dynamic progression of surface subsidence resulting from underground coal mining, an optimal time function model is synthesized based on the dynamic principles governing surface subsidence. Subsequently, the Boltzmann time function model is introduced to comprehensively analyze the model in terms of subsidence value, subsidence velocity, and subsidence acceleration. The analysis reveals that the model aligns with the dynamic trends of surface subsidence. Through an exploration of the influence of various parameters on the model’s representation, their physical significance is determined, and defined as the final subsidence value A, the time of maximum subsidence rate t₀, and the coefficient of the degree of urgency of subsidence B, leading to the establishment of a dynamic prediction model parameter system based on the Boltzmann time function. Fitting the measured subsidence values at a singular point demonstrates that the accuracy of this model surpasses that of traditional dynamic prediction models, achieving a fitting disturbance R² of 0.998 8. Parameter inversion is conducted on the measured subsidence values at monitoring points within the mining area. Based on the inversion results, correlations are established between the dynamic predicted parameters of any point in the subsidence basin and the maximum subsidence value on the surface, mining speed, and overlying rock lithology coefficient. A calculation method for determining the dynamic predicted parameters of the model at any surface point is provided, and its accuracy is verified to be reliable by utilizing the data collected from six working faces. A dynamic prediction model for surface subsidence, integrating the Boltzmann time function and probability integration method, is formulated, enabling predictions at any point and time within the subsidence basin. The model is employed to obtain subsidence values for multiple periods, and its accuracy is validated. Results indicate that the dynamic prediction relative error during the mining process is less than 6.0%, the minimum is 2.7%.

In recent years, a number of vertical shaft tilt deformation and breakage disasters have occurred in the eastern mining areas of China, which have seriously affected mine safety and production. In response to the tilting and damage disasters of deep vertical shafts in thick water-bearing loose layers, the tilting and deformation monitoring of shafts was carried out by taking the deep vertical shaft (800 m) of a mine in Lunan as the research object, studying the spatial and temporal change characteristics of shaft tilting, and analyzing the main influencing factors of shaft tilting; based on this, based on the deep learning theory, four types of deep learning method, namely, recurrent neural network (RNN), long and short-term memory network (LSTM), gated recurrent unit (GRU), and one-dimensional convolutional neural network (1DCNN), were used. unit (GRU), and one-dimensional convolutional neural network (1DCNN) to construct a wellbore tilt deformation prediction model, and compare the prediction results with the measured values to analyze the accuracy of the wellbore deformation prediction model, validate the reliability of the model, studied overall wellbore and critical area prediction effects, and carry out engineering applications. The study shows that: ① The wellbore tilt mainly occurs in the loose layer, the tilt value decreases linearly from shallow to deep, and is biased towards the side of the extraction zone, with a maximum of 352 mm, and the deformation of the bedrock layer is smaller, with a maximum of 88 mm; the increase in the range of deformation propagation in the thick loose layer caused by the mining, and the change of seepage hydrophobicity of the aquifer at the bottom along the wall of the well and the seepage field of the groundwater are the main causes of the tilted deformation of the wellbore. ② The Spearman correlation coefficient between the model and the measured value is 0.978 at the maximum and 0.867 at the minimum;the maximum difference between the four models and the field measured offsets is 0.043 m, the mean absolute error E_MA is within 0.003–0.009 m, and the root mean square error E_RMS is within 0.004–0.011 m. The overall prediction is optimized by the 1DCNN model, and the main tilting direction (The prediction accuracy of the main inclined direction (east-west direction, which is inclined to the side of the mining area) is slightly lower than that of the direction with smaller deformation amount (north-south direction), and all of them can meet the engineering needs. ③ The overall prediction curve of the wellbore is consistent with the actual tilt direction, and the average values of E_MA and E_RMS of the wellhead and loose bedrock interface are 0.005 m and 0.006 m. The accuracy of the wellbore bottoming is a little bit lower, with the corresponding values of 0.012 m and 0.013 m. The wellbore characteristic area and overall prediction effect are good, indicating that the wellbore deformation prediction model based on deep learning has good prediction ability. The research results have been effectively applied in the wellbore grouting repair and management project, which provides technical reference and data support for the safe management of wellbore, and provides engineering practical experience for similar projects.

The ecologically fragile mining area in the west is an important coal production base in China, and the current scale and intensity of coal mining has far exceeded its environmental carrying capacity, which is very likely to cause irreversible damage to the ecological environment. The restoration of surface ecology in the post-coal mining stage will be the most prominent environmental problem facing the region, while water resources play a fundamental role in this process, and the contradiction between "water-environment" is prominent. Mining-affected water resources refers to the water resources transferred, pooled and effectively stored due to mining activities, which are artificial aquifers, and play a pivotal role in the surface ecological restoration from the point of view of the regional water cycle. On the basis of summarizing the existing research results, the calculation methods of the total amount of mining-affected water resources and the storage capacity of mining space were proposed, the relationship between them and the influencing factors such as overburden structure, hydrogeology, coal mining and the stability of water storage space were elaborated, and the evaluation system of the potential of mining-affected water resources, which contains 15 parameters in three aspects, was established. The regional water cycle pattern and the ecological damage process under the influence of mining were analyzed, the calculation method of the total amount of mining-affected water resources required to maintain ecological balance was explored, the concepts of the optimal, reasonable and minimum ecological water demand in the region were defined, the indicators for evaluating the effect of surface ecological environment restoration were proposed, and the mine planning and design ideas and technical system based on the whole cycle of coal mining were constructed. Taking a mine in an ecologically fragile mining area in the west as an example, the state of water balance/overbalance under the regional water cycle was described, and the effect of surface ecological restoration was assessed and predicted. The results shows that even in dry years, the current volume of mining-affected water resources can provide reliable and sufficient water resources for the surface ecosystem, and the ecological restoration level is Class II. The surface ecosystem of 1.53−2.26 times the area of the goaf can be restored at the level of Class I in both common and abundant years, and the functional integrity of the ecosystem can be maintained over a larger area, with the ratio coefficient of up to 9.03 in an abundant year. The volume of mining-affected water resources increases step by step with the increase of coal mining area, and under the premise of meeting the regional ecological water demand, it is the next key research direction to store it as a strategic reserve resource for a long period of time and use it for national defense, people's livelihood and industry in due time. Water is the most critical influencing factor in the process of changing regional ecological environment elements, and the protection and utilization of mining-affected water resources have important strategic values for both safe and efficient coal mining and ecological environment restoration.

Revealing the aggregation and release mechanism of overlaying rock energy field is the theoretical basis for the prevention and cure of coal-rock dynamic disasters. By means of simulation experiment, numerical calculation and theoretical analysis, the mechanical models of two steady states before and after hard rock breaking were established. The step change characteristics of coal and rock under load before and after structural transient were compared and analyzed. The evolution mechanism of strain energy and gravitational potential energy accumulation and release of overlying rock under structural transient excitation was studied. The results show that it is affected by self-weight stress field and mining unloading effect, the rock strata within the mining influence range interact and restrict each other, and there is a close and complex mechanical connection. The structural transient induced by hard rock breaking, it breaks the balance of the original old order between the rock strata. It leads to the transient change of the mechanical relation between the strata and the load transfer path of the overlying strata. The strain energy field and the gravitational potential energy field of the overlying strata change accordingly. In addition, the transient change of overburden load transfer path will cause different instantaneous loading and unloading of coal and rock in different areas of stope space, resulting in differences in the energy evolution characteristics of overlying strata in different regions. Among them, after the fracture of the lower hard rock stratum, the instantaneous unloading of the internal force of the fracture surface and the instantaneous loading formed by the transient transition of the load transfer path of the overlying rock make some areas near the goaf instantaneously rebound upward and release strain energy, the instantaneous subsidence and release of gravitational potential energy in some areas within the rebound zone. At the same time, the instantaneous unloading of the support load in the transient region of the structure makes the upper hard rock layer sink instantaneously and the deformation increase sharply, and the gravitational potential energy is released and the strain energy is accumulated. In essence, the dynamic mechanical response process of coal rock in mining field under transient excitation of structural is a dynamic process of the evolution of the original space-time structure of coal rock in mining field to the new space-time structure after the original space-time structure of coal rock in mining field is broken. There is a mutual conversion of strain energy, gravitational potential energy and kinetic energy, accompanied by the aggregation and release of strain energy and gravitational potential energy. On the whole, the release area of overlaying rock strain energy is small, mainly concentrated in the instantaneous unloading area, and the rest areas increase instantaneously. The release range of gravitational potential energy is large, and only the rebound area of the lower hard rock layer increases slightly.

The migration and fracture of overlying strata during coal seam mining is an important factor affecting the strata behaviors in working face. By studying the damage and failure characteristics of overlying strata from the perspective of energy, the behavior law and potential risk of overlying rock migration and failure under the influence of mining can be better understood, which provides effective guidance for reasonable mining parameter design of longwall face. Based on the research background of Qinglongsi coal mine in Shenfu mining area, Shaanxi province, this paper studies the post-peak deformation and failure characteristics of overlying rock fracture damage from the perspective of two-dimensional plane and three-dimensional space through the energy dissipation theory. An innovative method has been proposed for calculating the total energy of overlying rock layers with gravity potential energy imparted by coal seam excavation. On the basis, an overburden damage degree characterization system was built based on energy conduction mechanism through the integration of numerical simulation and theoretical analysis. The finite difference equation for rock dissipative energy is derived based on energy balance and finite difference theory. This equation is then incorporated into the FLAC^3D strain softening model using FISH language. This effectively supplements the software energy calculation module. This approach addresses the limitations of conventional qualitative characterization of damage degree and type resulting from engineering rock excavation due to plastic zone effects. The energy dissipation degree of the scale effect of the index parameter was quantitatively characterized by defining the damage degree index. Based on the geological conditions of the Qinglongsi coal mine longwall face, a simulation analysis was conducted to investigate the influence of longwall face length and advance speed on the damage degree of overlying strata. The overburden damage degree increases and decreases in an “S” shape with the increase of longwall face length and advancing speed, respectively. Finally, it was established that the optimal longwall face length should not exceed 303.26 m, while the appropriate range for the uniform advance speed is between 10.13 m/d and 18.00 m/d. If the parameters of the longwall face exceed the above-mentioned range, the mining-induced damage could result in the failure of key controlling layers in the overlying strata, leading to a significant increase in the damage ratio. Finally, the feasibility of the characterization system based on the energy transmission model was verified through an analysis of the advance speed and the corresponding strata pressure of the 5-20108 longwall face. It was found that the increase in the advancing speed of the longwall face resulted in an increase in the step distance of the periodical Weighting, an increase in the strength of the mining pressure manifestation, and a decrease in the overall degree of overburden damage.

Hydraulic fracturing technology is one of the effective methods for weakening the roof of coal mines and preventing rockburst. This article takes the 2305 thick coal seam fully mechanized caving working face of a coal mine in Shaanxi Province as the engineering background, and uses theoretical analysis, numerical simulation, on-site testing, and engineering monitoring methods to study the weakening control technology of the hard roof area. Based on the theory of “plastic stranded wire”, a mechanical model of the basic top “thin plate structure” is constructed, and a method is proposed to determine the hydraulic fracturing target layer by combining the accumulated bending strain energy and the distribution and response characteristics of high-energy microseismic events at the critical state of the first fracture of the hard top plate in the coal seam extraction process. According to this method, the fracturing target layer of 2305 working face is determined to be 14.50 m thick coarse sandstone; A numerical calculation model for strain softening under fluid structure coupling mode was constructed, and a comparative experiment was designed with and without directional segmented hydraulic fracturing in the target layer. The strength stress ratio parameter was introduced to analyze the local stability of the roof. The results showed that directional long drilling hydraulic fracturing effectively broke the integrity of the basic roof and shortened the step distance of the basic roof. The initial step distance was reduced by 25.81%, and the periodic step distance was reduced by 24.64%, reducing the possibility of forming huge dynamic loads and inducing impact ground pressure due to the large suspended area of the roof; Based on the geological conditions of the 2305 working face, a multi-dimensional segmented hydraulic fracturing construction plan combining directional long drilling and conventional shallow drilling was designed. During the fracturing process of directional long drilling holes No.20, No.21, and No.22, there were 30, 35, and 23 instances of pressure drop above 3 MPa, respectively. The directional segmented hydraulic fracturing caused damage to the integrity of the roof. During the conventional shallow drilling fracturing process, the expansion forms of different fractures showed different stage characteristics of two-stage stability and multi-stage development on the fracturing curve. The fracturing effect of the roof and top coal was significant; Multiple monitoring methods were used to monitor the surrounding rock activity of the 2305 working face. The implementation of multi-dimensional segmented hydraulic fracturing technology destroyed the integrity of the hard roof. Compared with the 2303 working face without hydraulic fracturing, the initial and periodic pressure step distances were reduced by 24 m and 12 m, respectively, with a reduction of 33.33% and 32.19%, effectively reducing the working resistance of the mining face support and reducing the possibility of high-energy microseismic events, providing a guarantee for underground safety production.

The sedimentary rock strata of the coal measure are generally characterised by significant argillity, high water content and weak lithology. The problem of controlling the stability of the surrounding rock in soft rock argillation roadways has become increasingly prominent. Taking the typical soft rock argillation roadway in Huaibei Mining area as the engineering background, based on the investigation and measurement of engineering geological conditions, the composition of clay minerals and the macro and micro failure characteristics are analyzed, and it is clear that the water-rich environment and stress environment are the important factors inducing the deformation and failure of argillation roadway. The mudification instability of surrounding rock is mainly reflected in the progressive failure mode of hydration of argillous rock mass, bearing failure of anchorage structure, and mud-state collapse of surrounding rock. It plays a decisive role to realize the stability control of bearing structure of surrounding rock in roadway under the coupling effect of stress-water. On this basis, the step strengthening control principle of soft rock argillation roadway is put forward. On the premise of ensuring the closed-loop structure with high preload, high stiffness and high strength anchor (cable) support in the interaction relationship between support and surrounding rock, the engineering instability control method is judged according to the hydration degree of mudstone. Three important technical paths have been formed to improve the properties of mudstone surrounding rock with anchor injection, strengthen the structure of shallow pile group with rotary grouting, and replace the mudstone mass with anchor injection layer by layer. The new multi-strand combined hollow grouting anchor cable bundle independently developed for mining is applied to the floor heave control in the west roadway of Luling Coal Mine. For the first time, the underground high pressure rotary-grouting engineering practice was carried out in the 8204 roadway of Guobei Coal Mine. The instability problem of mudded surrounding rock in belt roadway of the second level of Zhuxianzhuang Coal Mine is solved by the method of strong displacement of mudded surrounding rock by artificial constructed rock mass. According to the deformation of surrounding rock of roadway, the supporting forming condition of surrounding rock and drilling into results show that the results better solve the problem of soft rock roadway control. It strengthens the bearing capacity of surrounding rock of muddy roadway at multiple levels, ensures the long-term safety and stability of surrounding rock, and provides effective scientific control concept and technical support for surrounding rock control of soft rock argillation roadway.

Through theoretical analysis, a three-dimensional model of the full-plane strain problem considering the influence of the axial stress of the roadway is established. The implicit analytical solution of the second invariant deviatoric stress J₂ of the roadway surrounding rock under the three-dimensional stress field is derived. The distribution and morphological evolution of J₂ under different horizontal lateral pressure and axial lateral pressure stress environments in the elastic state and plastic state of the roadway surrounding rock are analyzed. Based on the Kastner solution method, the implicit solution of the plastic zone boundary of roadway surrounding rock under three-dimensional stress field is obtained, and the distribution characteristics of plastic zone of roadway surrounding rock under different stress conditions are studied by mathematical and numerical analysis methods. The corresponding relationship between the second invariant deviator stress J₂ and the plastic zone shape of surrounding rock is established, and the deformation and failure mechanism of surrounding rock is revealed. Taking the return airway of 31205 working face in Cuncaota No.2 Mine as the engineering background, the distribution characteristics of J₂ and plastic zone of roadway surrounding rock under superimposed mining are studied, the characteristics of asymmetric deformation and failure are quantified, the interaction relationship between support resistance and J₂ is sought, and the stability control technology of superimposed mining roadway is proposed. The results show that: When the axial lateral pressure value is fixed and the horizontal lateral pressure value is changed, the morphological distribution characteristics of J₂ and plastic zone show the evolution process of “circular-elliptical-butterfly-like”. When the horizontal lateral pressure value is fixed and the axial lateral pressure value is changed, the shape of J₂ and plastic zone remains unchanged. The change of axial stress has little effect on the shape of plastic zone, but has a great influence on the size of plastic zone. The greater the concentration of surrounding rock J₂, the greater the degree of deformation and failure of surrounding rock. The distribution of J₂ determines the failure mode of plastic zone to a certain extent. The 31205 return airway is in a high deviatoric stress J₂ environment under the influence of superimposed mining, and the stress distribution characteristics of rotating to the side of the goaf are formed, resulting in the formation of asymmetric large deformation and failure of the roadway. The increase of support resistance has limited effect on the decrease of deviatoric stress J₂ of roadway surrounding rock, and it is impossible to completely control the stability of roadway surrounding rock only by bolt (cable). Based on the above research, the combined control technology of advanced strong support + bolt (cable) support system is proposed, and the field application effect is good.

Realizing the intelligent warning of rock burst in coal mine is of great significance to ensure the safety of mine operation. Based on the intelligent classification prediction of rock burst occurrence time series in roadway of steeply inclined ultra-thick coal seam in a mine in Xinjiang, the spatio-temporal evolution of each microseismic information index during roadway excavation was analyzed. The Random Forest optimized by Genetic Algorithm (GA) was used. RF selects a number of indicators with high performance in predicting the development trend of impact. Based on the Phase Space Reconstruction (PSR) technology, the data is mapped to the high-dimensional space for reconstruction. LSTM is trained to learn the characteristics of high dimensional data, and a prediction model of steeply inclined ultra-thick coal seam rock burst (PSR-LSTM) based on deep learning and multiple chaotic time series is constructed. The results show that each microseismic information index is sensitive to shock warning and has significant correlation with each other. Six microseismic information indexes with high performance in predicting the development trend of shock are selected. The time series of multiple indicators has chaotic characteristics. After phase space reconstruction, LSTM learning and training can effectively enhance the data utilization rate and prediction accuracy of the model. When the prediction time of the constructed PSR-LSTM model is specified as 1 day, the prediction accuracy can reach 0.9135, and the F₁ value can reach 0.9116. All of them are better than the unreconstructed LSTM model. The model can well predict the time series trend and danger level of the rock burst in the excavation roadway of steeply inclined ultra-thick coal seam. The research method can provide reference for the intelligent prediction and early warning of rock burst in the excavation roadway of steeply inclined ultra-thick coal seam.

Borehole drilling is an essential step for the anchoring control of roadway surrounding rock of coal mines. The efficiency of bolt installation and bonding effect between resin-rock interface are closely related to the quality of borehole formation. When borehole drilling in argillaceous surrounding rock, the phenomenon of drill sticking and drill jamming exists, and it is difficult to discharge the drilling cuttings when occurring argillization, which is the bottleneck restricting rapid and high-quality formation of borehole. Therefore, by using theoretical analysis and laboratory test methods, this paper studied the mechanism of argillization and adhesion and influencing factors of the drilling cuttings in the borehole of soft argillaceous surrounding rock containing kaolinite. The results show that the oxygen atoms with strong electronegativity on the surface of kaolinite crystal layer adsorb hydrogen atoms in water molecules to form hydrogen bonds, and constantly absorb water molecules to expand the water layer, and finally form a “water film” of multi-layer water molecules. The adsorption of water by kaolinite clay on the surface of drilling cuttings makes the drilling cuttings also coated by “water film”. At the same time, with the continuous dissolution of non- argillaceous minerals and the swelling of drilling cuttings particles, the spacing between drilling cuttings particles is reduced, which is easily captured by van der Waals forces between each other’s water films, so that they aggregate to form aggregates. The main reason for the adhesion of drilling cuttings is that the drilling cuttings is subjected to the electrostatic force generated by its own “water film” and the surface of the drill bit and the interfacial tension of the overall structure formed by the “water film” on the surface of the drill bit. The electrostatic force plays an important role in the process of argillization and adhesion of drilling cuttings. The degree of argillization of drilling cuttings decreases with the increase of particle size of drilling cuttings, solid-liquid ratio, stirring speed and time of drilling tool, and K ion concentration. Acidic solution will also inhibit the mudding of drilling cuttings. The significant degree of each factor on the inhibition of drilling cuttings argillization in the test range is in the order: solid-liquid ratio, particle size of drilling cuttings, stirring time, stirring speed, pH value and K ion concentration. The countermeasures to suppress the argillization of drilling cuttings are put forward. such as adjusting the structure of the drill bit, increasing the liquid inlet pressure, increasing the rotation speed of the drilling tool, and adjusting the composition of drilling fluid can weaken the degree of argillization of argillaceous drilling cuttings and water, and reduce the adhesion to the drilling tool. The research results can provide a theoretical reference for improving the quality, efficiency and anchoring support effect of the boreholes in soft argillaceous surrounding rock.

In order to explore the influence of the stiffness of the loading system on rock failure mode and energy evolution law, the self-developed rigidity and variable stiffness test system is used to carry out biaxial compression tests, and the mechanism of the loading system stiffness on the post-peak unsteady failure and energy release law of rock under lateral constraints is analyzed. The results show that: The interaction between the rock sample and the testing machine system is analyzed from the perspective of energy dissipation and release, revealing the relationship between these factors during the rock failure process under the stiffness of the loading system. It can be divided into three modes: stable failure (W_d > W_u +W_e), critical state (W_d =W_u +W_e), and unstable failure (W_d < W_u +W_e). Under low stiffness conditions, the stress-strain curve of the rock sample shows significant stress drop and fluctuation, indicating local unsteady failure. In contrast, under high stiffness conditions, the post-peak stress of the rock sample decreases gradually, and the curve is stepped with a residual stage. With the increase of the stiffness of the loading system, the maximum strain energy release and maximum dissipative energy of the rock sample decrease nonlinearly, while the increase of the lateral binding force leads to the nonlinear increase of the maximum strain energy release and maximum dissipative energy. The application of lateral constraints strengthens the stiffness rebound effect and changes the energy release mode when the rock is fractured. In the early stage after the peak (∆W_pe > ∆W_pd), the energy release is relatively rapid, In the middle stage after the peak (∆W_pe < ∆W_pd), the energy is mainly dissipated, In the late stage after the peak (∆W_pe≈∆W_pd), the energy release and dissipation enter a stable stage. The research results provide a theoretical basis for understanding the post-peak failure mechanism of the loading system stiffness and dynamic disaster prevention, and propose measures such as lateral binding, phased energy control and reducing the energy storage capacity of the rock mass to improve the energy release mode, enhance energy dissipation, and enhance the stability of the surrounding rock of the roadway.

To investigate the mechanical characteristics and deformation evolution patterns of buried natural gas pipelines under subsidence in coal and natural gas overlapping areas, this study integrates pipeline deformation theory with numerical simulation to analyze the effects of mining-induced subsidence on pipeline deformation. Moreover, full-scale mechanical characteristic tests were conducted to explore the stress and deformation behavior of large-diameter pipelines under external loads, followed by a comprehensive safety and operation analysis. The results demonstrate that, as pipeline subsidence increases, the amount of subsidence at the pipeline ends is smaller than the central segment, and the deformation is approximately symmetrically distributed around the center. The relative displacement at the center of the pipeline is less than that at the ends. Under the combined effects of self-weight and external load, the top of the pipeline is subjected to compressive forces, while the bottom experiences tensile forces. The compression and tensile deformation increase progressively from the ends toward the center, with the maximum deformations occurring at the pipeline center. As the applied load increases, the overall deformation pattern of the pipeline transitions from a flat-bottom shape to a funnel-like shape. Under self-weight, the maximum settlement of the pipeline is 45 cm, reaching 35% of the maximum allowable settlement. When external loads are applied, the maximum settlement increases to 63.6 cm, accounting for 50% of the maximum allowable settlement. Based on the pipeline’s tensile strain and the maximum allowable elastic deformation, the safety threshold of the pipeline was estimated. The tensile displacements were calculated as 31 mm and 90 mm under coordinated and uncoordinated deformations between the pipeline and surrounding soil, respectively, which remain below the material’s safety limits.

The presence of slide-resistant structures within faults alters the laws of energy accumulation and slip behavior, resulting in significant differences in the mechanisms of fault activation and instability compared to conventional understanding. To study the evolution laws of activation and energy storage of hard rock-bridge-type faults under mining influence, the activation conditions of faults with slide-resistant structures of hard rock bridges were theoretically analyzed. The slip laws of faults with hard rock bridges under mining disturbances was studied by physical simulation experiments. The differential characteristics of fault activation between faults with hard rock bridges and those without slide-resistant structures were analyzed. Moreover, the variation characteristics of normal and shear stresses in the fault zones with hard rock bridges and without slide-resistant structures during the working face extraction process were studied. Using the numerical simulation method, the stress distribution and energy accumulation laws in the fault zones with hard rock bridges and without slide-resistant structures during the mining process near the fault were studied. The research results indicate that faults with hard rock bridges under mining disturbances exhibit more pronounced non-uniform slip behavior. However, the fault slippage amount is significantly reduced, and the degree of activation is decreased. The hard rock bridges can enhance fault stability, and this improvement in stability is primarily reflected in the increased cohesion of the fault surface. The hard rock bridge near the working face has the highest stress concentration and is most prone to shear failure, but to a certain extent, the hard rock bridge will disperse the stress concentration zone. For fault zones without slide-resistant structures, the elastic strain energy density gradually increases as mining approaches the fault, but the extent of increase remains limited, and the peak value of elastic strain energy density consistently occurs in the area ahead of the working face. However, The existence of hard rock bridge alters the energy distribution law in the fault zone, with the peak of strain energy density is mainly concentrated in the contact between hard rock bridge and fault zone. The closer locations within the fault zone is to the rock bridge, the higher the degree of slip compression and the higher the degree of energy accumulation. The energy accumulation in faults containing hard rock bridges is significantly greater than in faults without slide-resistant structures. The slide-resistant structures can greatly enhance the energy storage potential of fault zones.

Under the action of disturbance load, the rheological rock mass in the “sensitive neighborhood” is prone to deformation and failure. In order to study the influence of confining pressure on the range of disturbance “sensitive neighborhood”, the red sandstone is taken as the research object, and the RRTS-IV rock rheological disturbance effect test system is used to carry out the disturbance impact test on the rheological rock mass under different confining pressures and axial pressures. The change rule of axial disturbance strain with axial pressure is observed, and the change of “sensitive neighborhood” under different confining pressure conditions is analyzed. The nuclear magnetic resonance analysis system is used to compare and analyze the rheological rock mass under different confining pressure conditions. The variation of porosity, T₂ spectrum curve, spectral peak area and pore size distribution of rheological rock mass in sensitive and non-sensitive areas before and after disturbance. The results show that: When the confining pressure remains constant, the axial disturbance strain value shows a nonlinear trend of decreasing first and then increasing with the increase of axial pressure, and when the axial pressure applied to the rheological rock mass is closer to the long-term strength under the confining pressure condition, the axial disturbance strain value generated by the dynamic disturbance is larger. There is a sensitive transition point (${\sigma _m}$) in rheological rock mass under different confining pressure conditions, which determines the sensitivity of rheological rock mass to dynamic disturbance. When ${\sigma }_{1} < {\sigma }_{m}$, the sensitivity of rheological rock mass decreases with the increase of axial pressure. When ${\sigma _1} \geqslant {\sigma _m}$, the sensitivity of rheological rock mass increases with the increase of axial pressure. According to the sensitivity of rheological rock mass, three sensitive areas are divided: R₁ non-sensitive area, R₂ sensitive area and R₃ creep failure area. It is determined that the range of sensitive neighborhood ($\Delta \sigma$) should be between long-term strength (${\sigma _p}$) and sensitive transition point strength (${\sigma _m}$). By calculating the change of “sensitive domain ratio” under different confining pressure conditions, it is found that the inhibition of confining pressure on crack propagation in rock mass and the increase of damage threshold do not increase nonlinearly, but show a trend of deceleration growth. When the rheological rock mass is in the sensitive area, the external disturbance impact will lead to the generation of new micro-pores inside the rock mass, and under the action of disturbance impact, the micro-pores inside the rock mass will gradually penetrate and expand into new large-aperture pores, which makes the number of pores inside the rock mass increase. At the same time, the influence of external disturbance impact on the development of pores inside the rock mass will gradually decrease with the increase of confining pressure. When the rheological rock mass is in the non-sensitive area, the external disturbance impact will make the large pores in the rock mass close, resulting in a decrease in the total number of pores in the rock mass. At the same time, the formation rate of new micro pores and the closure rate of large pores in the rock mass will gradually decrease with the increase of confining pressure. The research results have important practical significance for enriching the theory of rheological disturbance effect of triaxial rock.

During the deformation and rupture process of loaded composite coal rock, due to the generation and expansion of fissures, small vibrations will be generated, and their change characteristics are closely related to the coal rock stress and rupture deformation. Through the use of fluctuation principle, vibration-electricity conversion principle and other related theories combined with PVDF piezoelectric film technology, we independently developed a new type of equipment to convert the small vibration into voltage signal and collect it, and carried out uniaxial compression experiments on the composite coal rock under the conditions of different loading rates and different coal seam ratios to study the microseismic voltage evolution law at each stage of the deformation and rupture process of the loaded composite coal rock and obtain the microseismic characteristics and its deformation and rupture characteristics during the deformation and rupture process of the composite coal rock body. The microseismic characteristics of the composite coal rock in the process of deformation and rupture and the correlation between them and the rupture behavior of the coal rock body are investigated. The results show: The self-developed microseismic voltage acquisition equipment has high accuracy and sensitivity, and the acquired voltage data can be used as the basis for describing the microseismic characteristics of the loaded coal rock; under the condition of different loading rates of loaded composite coal rock, the process of stress change is positively correlated with the change of the microseismic voltage, and the microseismic voltage is more sensitive to the change of the loading rate compared with the stress; the evolution of microseismic voltage in each stress stage is different, the amplitude of microseismic voltage in the compression stage rises slowly from low, the microseismic voltage in the elasticity stage changes in the first and middle stages of the small fluctuations of irregular amplitude, and in the later stage of the microseismic voltage appears to fluctuate from low to high, the microseismic voltage fluctuations in the yield stage intensify in amplitude, and in the final stage there is a characteristic of the rupture precursor, and in the rupture stage there is a pulse amplitude of the microseismic voltage that is almost synchronized with the stress peak and returns to steady state rapidly after complete rupture of coal rock. the coal rock is completely ruptured, it quickly returns to a steady state; the increase of the proportion of composite coal rock combination leads to the increase of the amplitude distribution range and average amplitude of the main body of microseismic voltage, the peak voltage decreases, the amplitude number of the instantaneous voltage of the coal rock rupture decreases, and the overall distribution changes from dense to sparse. The tiny vibration generated by the loaded deformation and rupture process of the composite coal rock is converted into electrical signals and analyzed the change rule, and the correlation between the microseismic characteristics of the composite coal rock and the internal rupture behavior of the coal body is obtained, which provide new technological approaches for the safe production and sustainable development of the coal mining industry.

The segmented fracturing and pressure relief gas drainage technology in the horizontal well of the coal seam roof is a key means to guide the efficient gas extraction in deep, high gas, soft and low permeability coal seams.Based on this, a full lifecycle development concept for the segmented fracturing, pressure relief,and gas drainage engineering of the coal seam roof horizontal well is proposed, including three stages: early scientific planning, mid-term engineering construction, and later safety management.This paper summarizes the research progress on the full life cycle development of segmented fracturing and pressure relief gas drainage in coal seam roof horizontal wells, constructs an overall research framework for key scientific issues related to segmented fracturing and pressure relief gas drainage in coal seam roof horizontal wells, and looks forward to its future development direction.The results show that the expansion of segmented fracturing cracks in the horizontal well of the coal seam roof is extremely complex due to geological factors, construction parameters, and physical properties.It is urgent to comprehensively evaluate the primary and secondary relationships under the influence of multiple factors in crack expansion, and reveal the mechanism of coal seam roof fracturing crack expansion under the influence of multiple factors.Exploring the critical relationship between the coupling of stress, water, temperature, and coal factors on the promotion and inhibition of coalbed methane adsorption, desorption, and migration, and establishing an optimal model for coalbed methane adsorption and desorption under multiple critical indicators, is the key to achieving efficient coalbed methane extraction. At present, there is insufficient research on the residual water from coal seam roof fracturing in terms of polluting water sources, inhibiting gas drainage, and dangerous accumulation, and there is a lack of management experience and technical support in a “Chinese style” approach.Guided by the development concept of the entire life cycle of coal seam roof fracturing engineering, this paper analyzes its high water consumption, fracturing fluid selection and potential pollution, reasonable selection of proppants, air pollution and seismic risks, and puts forward corresponding policy and regulatory formulation ideas.Realizing real-time and accurate monitoring of multi crack competition expansion in complex environments, revealing the mechanism of segmented fracturing and cross interface crack expansion of coal seam roof under the influence of multiple factors, constructing an effective radius evaluation model for segmented fracturing crack expansion of coal seam roof horizontal wells, exploring the water and gas migration law under the dual anisotropy conditions of three-dimensional stress and coal body structure, achieving advanced detection of potential danger areas for water and gas aggregation during fracturing of coal seam roof horizontal wells,and establishing a refined evaluation model for the effect of segmented fracturing,pressure relief, and gas drainage in coal seam roof horizontal wells is currently a key scientific problem that urgently needs to be solved.Finally, the development direction of precision,coordination, intelligence, comprehensiveness, and demonstration of segmented fracturing and pressure relief gas drainage technology for coal seam roof horizontal wells was outlined.

To solve the difficulties such as the small range of unloading pressure in hard coal seams and poor permeability enhancement effect, based on the water dynamic flexible cutting coal unloading and permeability enhancement technology, the combination of the quality and impact velocity of the terminal end teeth was optimized when the kinetic energy of the terminal end teeth was constant, in order to improve energy utilization and coal breaking efficiency. Therefore, flexible cutting coal impact experiments were carried out, and the coal fragmentation quality and average fragmentation depth under different conditions of terminal end teeth quality and velocity were analyzed. A numerical simulation method of particle flow was used to establish a model of flexible cutting coal impact with the terminal end teeth, and the energy of the coal body and the evolution law of the cracks during the coal breaking process were analyzed to reveal the influence mechanism of the terminal end teeth quality and impact velocity on the effect of flexible cutting coal impact. Results show that when the kinetic energy of the end teeth is constant, with a decrease in tooth mass and an increase in impact velocity, the quality of coal fragmentation and the average depth of fragmentation both show an initial increase followed by a decrease in trend. The area of coal shear crushing zone, total number of cracks, and the distance from the deepest axial main crack to the surface of the coal body all show an initial increase followed by a decrease in trend. After the end teeth come into contact with the coal body, the kinetic energy of the teeth rapidly decreases, principally transforming into the coal’s strain energy and frictional energy. The accumulation and release of strain energy leads to the generation of a large number of cracks directly below the teeth, forming a semi-circular shear crushing zone. Around the shear crushing zone, there is a concentration of stress at the weakly bonded areas of the cracks, resulting in the formation of main cracks that extend outward. When the kinetic energy of the end teeth is 60.3 J, with a tooth impact velocity of 38.8 m/s and a mass of 0.08 kg, the coal fragmentation effect is optimal. As the impact velocity of the end teeth increases, the energy density acting on the coal body increases per unit time, but the impact force decreases, causing the peak strain energy of the coal body to first increase and then decrease. When the peak strain energy is at its maximum, the coal body exhibits the best crushing effect.

Gas and coal dust are the two major killers that restrict coal mine safety production and endanger the lives and health of miners. Coal seam water injection was widely used for coal dust prevention and gas control. However, in coal seams with high gas content interferes with the wetting of coal by moisture, resulting in poor wetting effect of gas-bearing coal. Dodecyl surfactants (C₁₂H₂₅−[HG]) were frequently utilized in studies aimed at enhancing the wetting of non-gas-containing coal. Typical hydrophilic groups ([HG]) within these surfactants include —OH, —COOH, and —SO₃H. However, the regulatory behavior and mechanisms of these groups concerning the wetting of gas-containing coal remain unclear. This paper conducted research using experimental and molecular dynamics simulation methods. The surface tension between C₁₂H₂₅−[HG] solution and gas, the contact angle between C₁₂H₂₅−[HG] solution and gas-containing coal, the interfacial energy, the evolution of functional groups after C₁₂H₂₅−[HG] solution and pure water infiltration of coal samples, and the potential difference between hydrophobic sites and water molecules showed that the control effect of —OH, —COOH, and —SO₃H hydrophilic groups on the wetting of gas-bearing coal gradually increased. In the micro models of surfactant solutions and gas-bearing coal, the interactions between —OH, —COOH, and —SO₃H hydrophilic groups and oxygen atoms in water molecules are enhanced, and their radial distribution functions and coordination numbers gradually increase. The presence of hydrophilic groups such as —OH, —COOH, and —SO₃H results in an increasing radial distribution function and coordination number between hydrophobic groups and coal molecules. For dodecyl surfactant solutions containing —OH, —COOH, and —SO₃H groups, the adsorption degree of water molecules gradually increases and the diffusion coefficient gradually decreases, while the aggregation degree gradually increases. The degree of methane molecule displacement gradually increases and the diffusion coefficient gradually increases. The introduction of - SO₃H hydrophilic groups into the solution helps to improve the wetting performance of gas-bearing coal. The research results provide theoretical guidance for efficient screening of surfactants suitable for coal mine gas control and revealing the mechanism of injecting surface active water into coal seams for gas control.

Grouting sealing is the most commonly used sealing measure of extraction borehole. Under the influence of stress disturbance, the cracks sealed by grouting are easy to crack and form secondary air leakage channels. Therefore, it is proposed to develop grouting sealing materials that can make regenerated cracks self-healing. However, the underground air environment is complex, especially the crack healing performance of the hole sealing materials depends on the self-healing products generated after the exchange of materials with the air environment. Therefore, in-depth research on the influence of different gas environments on the crack healing performance of the hole sealing materials is necessary to improve the ratio of hole sealing materials. It is of great significance to realize long - term sealing of extraction borehole. In this paper, the fracture self-healing and the generation of repair products of self-healing sealing materials in vacuum, CO₂ and air environment were studied. The results showed that the hole sealing material could realize the self-healing of cracks with a width of 1.82mm in the air environment within 6 days, and the hole sealing material could realize the self-healing of cracks with a width of 1.51mm in the CO₂ environment within 8 days, while the hole sealing material could only reduce the crack width by 0.1mm in the vacuum environment within 15 days, and could not achieve complete healing. Under different environment, the material exchange law of sealing material is different from the outside world, and its mass change is quite different. In air environment, it can be divided into water loss weight loss stage, dynamic weight gain stage, secondary water loss weight loss stage and stable stage. Under CO₂ environment, it can be divided into rapid carbonization weight gain stage, slow weight gain stage and equilibrium stage. Under vacuum, the quality of the specimen is almost stable. Combined with carbonization and water evaporation, the internal law of quality change of sealing materials under different environments was analyzed. The results show that the roughness of self-healing products is the highest in air environment, the second in vacuum environment, and the least in CO₂ environment. The microscopic test results show that CO₂ does not change the main structure of the sealing material, but can only slightly increase the content of CaCO₃ in the hydration products of the sealing material, and cause the matrix porosity to decrease. However, CO₂ can significantly increase the proportion of CaCO₃ in self-healing products, and has a significant effect on promoting the particle size of self-healing products. The formation principle of self-healing products in different gas environments is quite different. The formation of self-healing products in vacuum environment lies in the precipitation caused by porous structure. In the CO₂ environment, the self-repairing products are mainly formed by carbonation, and precipitation is auxiliary. Silicate produced by secondary hydration has the largest proportion of self-repairing products in air environment, followed by carbonate produced by carbonization, and the contribution of precipitation is the least. Moderate increase of CO₂ concentration and humidity in the curing environment can promote the efficiency of self-healing of cracks. The research results are of great significance for realizing long - term sealing of extraction boreholes.

Improving the permeability of coal seam is a common method to improve the efficient extraction of coal seam gas. Using liquid CO₂ as fracturing medium to freeze-thaw coal is one of the methods to improve the permeability of coal seam. Liquid CO₂ changes the permeability of coal seam by causing deformation damage to coal body. In-depth study of the deformation damage characteristics of liquid CO₂ freeze-thaw coal body is the basis for revealing the mechanism of liquid CO₂ fracturing and permeability enhancement coal body to strengthen gas extraction. Based on the self-developed experimental system of liquid CO₂ freeze-thaw coal body, the experiment of deformation and damage characteristics of coal body under liquid CO₂ freeze-thaw conditions was carried out by means of physical experiment. The surface temperature, stress, strain and tank pressure parameters of coal body during freeze-thaw process were monitored. The influence of liquid CO₂ freeze-thaw on stress and strain of coal body and the phase characteristics of CO₂ in tank were analyzed. The contribution of thermal stress, water-ice phase change frost heave force and vaporization expansion force to deformation and damage of coal body during liquid CO₂ freeze-thaw process was explored, and the mechanism of deformation and damage of coal body caused by triple composite stress of liquid CO₂ freeze-thaw was revealed. The results show that: The volume strain of liquid CO₂ freeze-thaw coal shows a ‘U’ -shaped trend of decreasing first and then increasing. The coal matrix shrinkage deformation occurs in the low temperature freezing stage, and the shrinkage deformation of the coal matrix gradually recovers in the melting stage, and finally an irreversible deformation is formed. The overall performance is two stages of coal matrix shrinkage deformation and strain recovery. During the experiment, the phase state of CO₂ shows a trend of gas-liquid ( gas-liquid coexistence ) -gas state. The freezing and thawing process of liquid CO₂ includes four stages: liquid entry, freezing, slow pressure relief and room temperature thawing. The corresponding deformation characteristics of coal body are freeze-shrinkage deformation, freeze-shrinkage + frost heave + adsorption expansion deformation, deformation recovery and thermal expansion deformation. The absolute values of the minimum strain values of unsealed dry coal, sealed dry coal and unsealed saturated coal are 10056.636×10⁻⁶,11480.186×10⁻⁶ and 7881.893×10⁻⁶, respectively. The residual strains are 270.191×10⁻⁶, 154.869×10⁻⁶ and 2033.636×10⁻⁶, respectively. The expansion and contraction rates are 2.686 %, 1.349 % and 25.801 %, respectively. The total deformation damage caused by the combined stress of liquid CO₂ freeze-thaw is 2033.636×10⁻⁶. The deformation damage caused by thermal stress, vaporization expansion force and water-ice phase change frost heaving force is 154.869×10⁻⁶, 115.322×10⁻⁶ and 1763.445×10⁻⁶, respectively, accounting for 7.615 %, 5.671 % and 86.714 % of the total deformation damage, respectively. The water-ice phase change frost heaving force dominates. With the increase of water content of coal samples, the absolute value of the minimum strain value of coal decreases, the residual strain increases, and the proportion of water ice phase change frost heaving force increases. The research results clarify the deformation and damage mechanism of liquid CO₂ freeze-thaw coal from the perspective of coal deformation and enrich the technical system of liquid CO₂ cracking and anti-reflection coal enhanced gas extraction.

Dust particles in humid-hot-dusty underground mine environment pose a great harm to the physical and mental health of the operators. Among them, fine particulate dust is easy to be inhaled and can reach the deep alveolar area of the respiratory tract, which is the main cause of occupational pneumoconiosis in coal mine industry. Herein, the electrospinning technology was used to regulate the structure of micro-nano fibrous medias. And a kind of composite medias with both highly efficient dust capture and enhanced moisture permeability were prepared by the layer upon layer of spinning method. Hydrophilic fibers were used to enhance the adsorption of water, hydrophobic fibers were used to avoid the production of capillary water in the medias. Meanwhile, the wettable diversion layers were added to construct the gradient polyethylene terephthalate (PET) based composite fibrous filter media, which might solve the difficult problems of preparation, poor skin affinity and insufficient comfort. In this study, using PET as substrate, hydroxylated graphene was added to enhance diffusion and electrostatic adsorption effects to capture dust. And polyvinyl pyrrolidone was selected to regulate the hydrophilic gradient and improve the moisture permeability. Microstructure characterization and performance detection showed that the fabricated fibrous membranes had micro-nano scale fiber diameter, excellent structural regularity and relatively smooth surface topography, exhibiting a good regulation of fiber diameter and morphology. Moreover, the distribution of surface elements and functional groups of each fiber membrane was consistent with its feature. Comparative experiments showed that the multi-layer composite membrane showed a better dust filtering performance, with a quality factor of 0.439 Pa⁻¹, and pore size distribution between 2.15 and 4.61 µm. Meanwhile, the contact angle test showed that the multi-layer composite membrane had a gradual wetting gradient variation from super-hydrophilic (0°) to hydrophobic (135.2°), and the water vapor transmission arrived at 5434.325 g/m²·24 h, which was 1.37 and 2.04 times higher than that of the hydrophilic and hydrophobic membranes, respectively. In addition, the terahertz scanning imaging analysis method was used to carry out the quantitative analysis of liquid water inside of the fiber material. Moreover, based on the terahertz scanning imaging analysis method, the transport mechanism of water molecules in the fiber membrane was clarified. It could be concluded that the proposed multi-layer gradient fibrous filter medias will have broad application prospects in the area of respiratory protection in the humid-hot-dusty industrial/ mining environment, which could also provide a new approach for the resource utilization of wastes.

The use of fly ash slurry for mineralization to capture CO₂, along with utilizing the mineralized slurry to prevent spontaneous combustion in goaf area, can achieve the dual benefits of pollution reduction and carbon reduction, as well as disaster management. Addressing the current issues in the CO₂ mineralization process of fly ash, such as slow leaching rate of calcium ions and low mineralization capacity, proposing a new approach to use ultrasound to accelerate the leaching of calcium ions from fly ash and enhance its CO₂ mineralization efficiency. Using ion chromatography to study the leaching patterns of calcium ions in low-calcium fly ash and high-calcium fly ash slurries, and employing low-temperature N₂ adsorption and SEM-EDS techniques to analyze the changes in structure of fly ash particles under the action of ultrasound, the paper evaluates the enhancement effect of ultrasound on CO₂ mineralization of fly ash using a self-built CO₂ adsorption and mineralization reaction experimental system. Moreover, the principle of ultrasound-enhanced leaching of calcium ions from fly ash was explored. The experimental results show that the leaching rate of Ca²⁺ in low-calcium and high-calcium fly ash slurries is very slow under static conditions, reaching leaching equilibrium only after 30 days. After ultrasound-enhanced treatment, the concentration of Ca²⁺ in both types of fly ash slurries can reach the leaching level of 30 days under static conditions within 30 minutes, indicating that ultrasound significantly enhances the leaching rate of Ca²⁺ in fly ash slurries. At the same time, after ultrasound-enhanced leaching treatment, the specific surface area of low-calcium and high-calcium fly ash increased by 23.71% and 184.71%, respectively, indicating that the cavitation effect of ultrasound can disrupt the aggregation and adhesion between fly ash particles, leading to particle refinement and further development of pore structure. This promotes mass transfer processes such as Ca²⁺ leaching from fly ash into water. Mineralization test results show that after ultrasound modification, the mineralization amount of low-calcium and high-calcium fly ash increased by 410% and 22%, respectively, with mineralized carbon sequestration amounts reaching 7.66 g/kg and 82.02 g/kg, respectively, indicating that ultrasound significantly enhances the CO₂ mineralization effect of fly ash. Based on this, utilizing the mineralized CO₂ product of fly ash slurry for preventing and controlling coal spontaneous combustion. Compared to treating coal samples with original fly ash, the heat release of coal samples treated with mineralized products decreased by 3.32% and 14.24%, respectively, indicating that mineralized CO₂ products have superior coal spontaneous combustion inhibition characteristics.

Bed separation water, as a source of sudden water inrush induced by mining, is characterized by large instantaneous discharge, periodic occurrence, and subtle warning signs, making it highly hazardous and extremely challenging to prevent and control. Taking the Zhaoxian Coal Mine in the Yonglong Mining Area of the Huanglong Coalfield, Shaanxi province, as the study area, a long-term multi-well pumping test was conducted on the Cretaceous aquifer. Hydraulic tomography inversion technology, based on the Simultaneous Sequential Linear Estimation (SimSLE) algorithm, was used to analyze the permeability evolution of the aquifer during mining. Finally, a mining-induced permeability evolution and bed separation water accumulation model, incorporating vacuum negative pressure effects, was established through groundwater dynamics and numerical simulation methods. The results indicate that: ① The permeability of the Cretaceous aquifer in the overlying strata exhibits a trend of initially increasing and then decreasing as mining progresses. Within the goaf area, the permeability coefficient of the Cretaceous aquifer increases to 23-392 times that of its natural state, while within the mining influence area, it increases to 1-67 times that of its natural state. In the horizontal plane, as the working face advances, the permeability in the front of the working face undergoes a sequential and progressive increase. ② Based on the conceptual model of the spatial convergence point in a semi-infinite aquifer, a theoretical model of bed separation water accumulation under vacuum negative pressure was derived. A “circular island model” for classic steady-state conditions was developed using COMSOL numerical simulation software. The numerical results showed minimal deviation from the theoretical model, indicating that the bed separation water accumulation model established using COMSOL is reasonable and reliable. ③ When the permeability of individual blocks evolves sequentially, the bed separation water accumulation rate increases only slightly. However, once all blocks evolve, the accumulation rate rises significantly from 14.09 m³/h to 98.95 m³/h, an increase of 84.86 m³/h. Additionally, the water inflow rate under absolute vacuum is 2.5 m³/h higher than under standard atmospheric pressure. The proposed aquifer permeability evolution-bed separation water accumulation model provides a research framework for predicting and analyzing the accumulation rate and evolution of high-level bed separation water.

Yushen mining area is the main mining area of the coal base in northern Shaanxi at present. During the development of high-intensity coal resources, the problems of coal seam roof water disaster and water resource leakage are prominent. with the comprehensive promotion of the ecological environment protection strategy in the Yellow River Basin, advanced, proactive, and source oriented geological guarantee requirements have been put forward for mine water prevention and water resource protection. the article focuses on the problem of water inrush (loss) in the loose water bearing layer near the surface under the influence of underground coal mining in Yushen mining area, Shaanxi Province. Drawing on the successful experience of curtain seepage reduction in open-pit large water mining areas, the article summarizes the basic conditions for carrying out underground continuous wall water interception curtains in coal mining areas from three aspects: stable supply water sources, relatively concentrated supply channels, and the waterproof layer conditions to prevent groundwater from flowing around; a theoretical model of water inflow under the condition of loose water rich aquifer curtain in underground coal mines is established. It is concluded that the weaker the permeability and thickness of the cut-off curtain wall, and the closer it is to the mining range, are the basic principles for reducing water inrush in the loose aquifer near the surface of the coal seam roof. Taking the problem of concentrated water inflow in a coal mining face in Yushen mining area as the research object, based on the basic principle of groundwater continuous wall curtain seepage reduction, it is analyzed that the main water source in the concentrated water inflow section of the working face is the loose aquifer groundwater near the surface, which has stable and observable dynamic recharge. The water conducting cracks formed by coal seam mining break through the roof waterproof soil layer and expose the strip-shaped ancient river channel inside the loose layer (the waterproof soil layer inside the ancient river channel becomes thinner and the loose layer becomes thicker), forming a relatively concentrated water inflow channel. Under the combination structure of "upper aquifer and lower barrier" (the upper layer is the rich water loose aquifer, and the lower layer is the relatively waterproof soil layer), it is believed that this section has the feasibility of constructing a lateral waterproof curtain wall. and a numerical model of the groundwater system was established for the working face under normal mining and curtain wall construction conditions. The simulation results showed that under local curtain wall conditions around the working face, the groundwater level gradient in the loose aquifer around the curtain wall was significantly intensified. However, due to the good permeability of the loose aquifer and the low terrain and water control conditions of the mining field, the groundwater level in the loose layer near the ground did not significantly rise. The groundwater runoff that entered the goaf through the thin bedrock area and the thickened strip of the loose layer was diverted downstream, and The overall water reduction rate under the construction conditions of a 600 m long lateral cut-off curtain wall is 28.43%. The research results of the article provide a scientific basis for the feasibility analysis of roof water damage prevention and groundwater resource protection based on water interception curtains in the Jinggong Coal Mine of Yushen Mining Area.

China’s coal-forming conditions are harsh, the coal-bearing environment is complex and changeable, and the resources are distributed in a global, multi-geological type and scattered distribution, resulting in frequent occurrence of mining-associated geological disasters. At the same time, with the optimization and regulation of coal resource development layout, the negative orientation of coal seam floor water damage is becoming more and more significant. The synergistic effect of high confined water hydraulic drive and strong sensitive defect structure activation leads to a significant increase in the threat of macroscopic dynamic representation of coal seam floor water damage, which has become an endogenous resistance to the high-quality transformation and development of coal resources in China. In order to grasp the development situation of coal seam floor water disaster in China in an all-round way and discuss the key research direction of prevention and control operation based on new technology in the future, the dynamic evolution trend of coal seam floor water disaster in China in recent years is comprehensively demonstrated from the multi-dimensional perspectives of time, space and water inrush quantity. The type is divided into “total-sub” type, and the mechanical mutual feedback response mechanism of coal seam floor water disaster in China is discussed by establishing geomechanical model. Based on the macroscopic representation of disaster, the endogenous disaster-causing mechanism is revealed, and the new development path and vision orientation of prevention and control technology concept are pointed out. The results show that: The evolution law and characteristics of coal seam floor water disasters in China from a multi-dimensional perspective are statistically analyzed, and the main framework of coal seam floor water disasters in China is discussed and established. According to the accident core cause system and macroscopic disaster-causing representation, the coal seam floor water disasters are divided into three categories: karst collapse column water inrush, fault activation water inrush and fracture-induced (composite) limestone water inrush, which are further refined into 12 subcategories, such as full-path through incremental water inrush (karst collapse column), through coal seam water inrush (fault), single-layer direct water inrush (fracture) with mining and unloading. The geographical spatial distribution of water disasters in three major types of coal seam floors was analyzed independently. The mechanism of ground stress and confined water pressure on the alienation development of confined water conduction path in the process of water inrush from karst collapse column is analyzed. The water inrush mode of floor karst collapse column induced by dynamic/static load disturbance of overburden roof is proposed, and its mechanical starting conditions and disaster-causing mechanism are clarified. The generalized model of macro-micro geomechanical structure of coal seam floor fault is established. Based on the identification of the core disaster-causing factors that induce fault activation water inrush, the mechanical criteria of fault activation water inrush in different types of coal seam floor are established. Based on the fracture as the basic unit, the critical discriminant conditions for the inrush of fissure-type ascending (composite) limestone water induced by single-layer and composite-layer confined aquifers are established by the formula of “one to n”, and the disaster-causing mechanism of the whole process of this type of floor water disaster is revealed. On the basis of summarizing the current concept of coal seam floor water disaster detection, prediction and control technology, combined with the frontier development direction, it is pointed out and suggested that the three-dimensional dynamic reconstruction of the whole life cycle mining-induced mutation characteristics of the background geological gene of the coal seam floor, the upgrading of the concept of coal seam floor water inrush prediction and prediction suitable for the dynamic geological environment of space-time differentiation, the application of low disturbance and strong intervention with mining\water control and mutual grouting treatment technology, and the establishment of long-term monitoring, diagnosis and treatment platform for geological ecosystem after restoration should be carried out to build a large system of full-time and space-time prevention and control of coal seam floor water disaster, and keep up with the development of new formats in the whole coal industry under the background of new productivity.

In coal mine production, water-proof coal pillars are reserved to prevent water hazards from old goaf areas. However, under long-term pressurized immersion of aggressive mine water accumulated in abandoned goaf areas, both macroscopic and mesoscopic structures of these coal pillars undergo continuous changes, leading to damage and deterioration. This results in reduced physical and mechanical strength, decreased stability, and ultimately instability and water inrush accidents. A self-designed high-pressure mine water-coal coupling test apparatus is used to simulate long-term immersion of coal pillar samples under different water pressures, simulated mine water, and original mine water conditions. Techniques such as computerized tomography (CT), X-ray diffraction (XRD), and a high-pressure servo-controlled compression testing system are employed to analyze structural evolution and mechanical damage degradation processes and mechanisms of coal samples under prolonged immersion. Results indicate that, under long-term immersion in aggressive mine water, coal sample structures exhibit significant irregular pore-fracture development, with porosity increasing from 0.25% to 1.2%, and the dispersion of pore development gradually decreases over time. Mechanical damage degradation effects are pronounced under long-term immersion in aggressive solutions, with immersion time and solution pH identified as the most influential factors. Mutual interaction occurs between coal samples and mine water during immersion, characterized by initial water absorption and swelling followed by dissolution and consumption in later stages. The physical-chemical coupling mechanism of structural evolution and damage degradation in boundary coal pillars of abandoned mines and goaf areas under high permeation pressure and long-term exposure to aggressive mine water is elucidated. The dynamic response process and key stages of coal pillars under pressurized immersion are revealed: the first stage is dominated by physical water absorption and swelling, resulting in an overall decrease in compressive strength and a fluctuating trend in tensile strength (initial decrease, followed by recovery and subsequent decline); the second stage is characterized by combined physical-chemical effects, where partial dissolution and depletion of clay minerals lead to increased porosity, thereby inducing physical and mechanical damage degradation. Based on the concept of the softening coefficient, the definition and calculation formula for the damage coefficient of immersed coal pillars are proposed, and empirical values for this coefficient are determined. Significant theoretical insights and practical engineering value are provided for evaluating the stability of boundary coal pillars in abandoned mines or goaf areas and for preventing and controlling water-related hazards.

Clarifying the adsorbed gas density of coal seam is the basis of studying the adsorption characteristics and the real gas content of coalbed methane, but the existing calculation methods of adsorbed gas density do not reflect the influence of temperature and pressure. Based on the analysis of the potential energy of gas intermolecular interaction and gas-solid molecular interaction, a non-uniform distribution model of gas density near the wall was constructed, and then the calculation equations of adsorption thickness and adsorption layer number were obtained. Then the calculation model of adsorbed gas density was derived, and corresponding adsorption model was established. The reliabilities of the proposed models have been verified by molecular dynamic simulation results and adsorption experimental results. The analysis results show that the adsorbed gas density is greatly affected by gas-solid interaction strength, pressure, and temperature. The stronger the gas adsorption capacity of coal, the greater the gas-solid interaction strength, the higher the gas density near the wall, the higher the adsorbed gas density, and the larger the adsorbed layer number. The region with 1 molecular layer thickness away from the wall is the strong adsorption region, and the main factor affecting the adsorption behavior in this region is gas-solid interaction; the region with more than 1 molecular layer thickness away from the wall is the weak adsorption region, and the main factor affecting the adsorption behavior in this region is external pressure. The gas density near the wall increases with the pressure ascending, and the gas adsorption process is to fill the strong adsorption region first and then to fill the weak adsorption region. Adsorbed gas density and free gas density both increase with the increase of pressure, but the adsorbed gas molecular layers’ number will decrease. The excess adsorption capacity shows a decreasing or stable trend with the ascent of pressure, as a result of the combined action of adsorbed gas density and molecular layers’ number. With the temperature increasing, adsorbed gas density, free gas density, adsorbed gas molecular layers’ number and thickness, and the absolute and excess adsorption capacity all show a downtrend, but the gas density in the range of 0.2 nm near the wall is less affected by temperature. Therefore, assisted by the desorption methods of reducing pressure and rising temperature, reducing the intensity of gas-solid interaction can further reduce the gas absolute adsorption capacity. In addition, the decrease in gas adsorption layers’ number caused by the effect of rising temperature and increased pressure is the reason for the decline in the proportion of adsorbed gas in deep coal seams.

China has abundant deep coalbed methane (CBM) resources with significant potential for development and utilization, which is expected to become an important supplement to national natural gas supply. However, the current deep CBM development technology is still in the exploratory status, and the reservoir stimulation mainly relies on massive fracturing, which suffers from significant differences in gas production rate and rapid production declines. The major reason behind is the lack of a stimulation technology that precisely matches geological conditions. “Orientation perforating + targeted fracture controlling + precision fracturing” is expected to become an effective fracturing method that is geologically compatible with deep CBM. This paper proposes seven orientation perforating patterns for deep coalbed horizontal wells: directional horizontal, 4 o’clock—8 o’clock orientation downward, fan-shaped orientation downward (upward), fan-shaped orientation downward (upward) + horizontal (240° perforation pattern), and straight upward orientation (downward). To investigate the uniformity of fluid and proppant distribution between and within clusters in deep coalbed horizontal wells under different orientation perforating patterns, this paper utilizes a coupled computational fluid dynamics and discrete element method (CFD-DEM). A fluid-particle transport fluid-solid coupling model for horizontal wellbores is established. The study examines the characteristics of inter-cluster and intra-cluster flow distribution and proppant distribution under different orientation perforating patterns, flow rates, sand ratios, cluster numbers within one stage, and graded proppant injection. The results show that the uniformity of flow and proppant distribution varies under different orientation perforating methods. The 240° orientation perforating (fan shape down or up + horizontal direction) shows better uniformity in flow distribution between holes, and the 240° orientation perforating and 4 o’clock—8 o’clock orientation downward perforating show better uniformity in proppant distribution between holes. High pumping rates (> 16 m³/min), low sand ratios (maximum sand ratio during the sand carrying stage < 25%), a higher proportion of smaller particle-sized proppants (0.212/0.109 mm∶0.380/0.212 mm∶0.550/0.270 mm = 6∶3∶1), and 3 to 4 clusters within a stage are conducive to the uniform distribution of flow and proppant between holes/clusters, enhancing the balance of reservoir stimulation. Field applications in the eastern margin of the Ordos Basin for deep CBM have shown that orientation perforating yields higher gas production than conventional spiral perforating, with the “fan shape down + horizontal direction (240° pattern)” orientation perforating showing the most significant increasing in gas production. It is recommended that deep CBM reservoir stimulation be designed based on the position of the well trajectory within the coal seam (especially its relative position to bright coal), implementing a “one-cluster one-policy” perforating design to induce directional fracture initiation, targeted communication with the “geological-engineering” sweet spots, and achieve the stimulation objectives of “directed guidance, taper design, uniform proppant placement and effective support”. The key findings are expected to provide theoretical foundations and parameter references for high-quality and efficient fracturing in deep CBM wells.

Accelerating the exploration and development of deep coalbed methane resources is a key direction for developing coalbed methane. However, with large-scale volume fracturing in deep coalbed methane development, the complexity of the fractures formed by deep coalbed methane fracturing gradually increases. However, the low-viscosity fracturing fluid carrying spherical proppants has limited transport and turning performance in complex deep coalbed methane fractures, resulting in the poor placement of proppant on the branch and deep fractures, seriously affecting the effect of deep coalbed methane large-scale volume fracturing. Thus, the author proposes a biomimetic dandelion proppant with efficient transport and steering capabilities in low-viscosity fracturing fluids. To further understand this proppant's transport and steering performance in deep coal seam fractures under different construction parameters, this study constructs a T-shaped visualized complex fracture proppant transport experimental system based on common T-shaped fractures in deep coal seams. The effects of construction parameters such as pump rate, perforation position, fracturing fluid viscosity, proppant particle size, and proppant concentration on biomimetic dandelion proppant transport and steering performance in T-shaped fractures were studied. It was found that with the increase of pump rate, the support area of biomimetic dandelion proppant in the primary fracture of T-shaped fractures would increase. The sand embankment channel rate was gradually increasing. At the same time, more proppants were turning into the branch fractures of the T-shaped fractures, indicating an increase in pump rate and an improvement in the transport and turning performance of the biomimetic dandelion proppants. Biomimetic dandelion proppants could maintain good transport efficiency in fracturing fluids of different viscosities and accumulate to form sand embankments with large channels. A single perforation in the middle could form better accumulation effects in both the branch and central fractures of the T-shaped fracture. As the sand ratio increases, the area of the proppant in the primary and branch fractures of the T-shaped gradually increases. However, as time passes, the increase of proppant area would slow down, and the channel rate of the sand embankment gradually decreases. Based on qualitative analysis of construction factors, it is recommended to use biomimetic dandelion proppant with medium to high displacement, low viscosity, middle perforation method, small particle size proppant, and 7%–11% sand ratio when applying it to deep coalbed methane. This study can promote the large-scale application of biomimetic dandelion proppants in deep coal seam fracturing and is also of great significance for the efficient development of deep coalbed methane in China.

Limit volume Fracturing Technology is the effective means to achieve high yield industrial flow for deep coal rock gas, on the basis of this technique, fracturing fluid is the key to fully “Breaking” coal seam, establish filling sand complex crack network, realize Anatonosising-Desorption promote for coal rock,therefore, the focus of coal rock gas fracturing fluid research is fully meet the field condition, construction technology and physical characteristics of coal rock. Focus on the research of the friction reducer with high stability, instant, low dosage but high efficiency and on-line viscosity change integration,a switch-type emulsion resistance reducer was prepared by introducing inorganic salt stimulation response material, designing switch reverse phase emulsion polymerization technology, condition controling of Multicomponent copolymerization and compounding desorption promote agent. The influence law on fracturing fluid performance by important parameters of emulsion resistance reducer was clarified by combining Characterization and Evaluation of basic performance, the expected coal rock gas special resistance reducing agent SFY-2 was obtained with the optimization conditions of hydrolysis ratio for 50%～55%, molecular weight for about 18 million and effective content for 29%～34%, the stability is improved to over 50 days, the low temperature resistance is below −15 ℃, the dissolution time is reduced to 10 s, the viscosity increasing rate is over 90% in 3 min, and the viscosity increasing ability is strong,the highlight contradiction of convention emulsion friction reducer between stability and instant solubility was resolved,as well as provided a guarantee for the online integrated construction of deep coal rock gas Ultimate volume Fracturing. By taking the advantage of SFY-2, a efficient and variable viscosity fracturing fluid is constructed to fit the design idea of coal rock gas Ultimate volume Fracturing, the variable viscosity control scheme is formulated and the construction technology is optimizated to achieve the goal of “Breaking” the coal rock sufficiently, creating complex sewing nets, filling sands fully and supporting effective. Performance evaluation of fracturing fluid indicated that: after simulate variable shearing of 170 s⁻¹～1 500 s⁻¹～100 s⁻¹ at 70 ℃, the viscosities of high viscosity fluid and middle viscosity fluid were kept 35 and 20 mPa·s respectively; The drag reduction rates of high viscosity fluid, middle viscosity fluid and low viscosity fluid can respectively reachs more than 66%, 72%, 77%, furthermore, the resistance retention rate of high viscosity fluid and middle viscosity fluid is over 100% under high shear conditions, thanks to the good shear dilution of fracturing fluid. The corresponding relationship between the suspended sand performance and the viscoelastic parameter tan δ for the fracturing fluid has been established, when the dosage of SFY-2 exceeds 0.2% (tan δ=0.84), the settling speed of fracturing fluid is obviously reduced, When the dosage reaches 0.4% (tan δ=0.395), the viscoelasticity of fracturing fluid is significant, which is conducive to high strength continuous sand adding for seam mesh saturation support, and increases the effective transformation volume of seam mesh. There is almost no residue in fracturing fluid gel breaker, the surface tension is as low as 26 mN/m or below, the gel breaker can effectively improve the wettability of coal rock surface, increase the contact angle up to 108.2°, reduce the desorption damage rate of coal rock as low as 13%. This technology has been applied more than 350 Wells (more than 2 000 stages/times in total) in the deep coal reservoir of Ordos Basin, with the advantages such as stable liquid performance, high construction efficiency, the real-time Drag reduction rate reachs 84.4%, highly sand completion rate, remarkable effect of increasing production,and so on, which provided power for realizing the scale benefit development of deep coal rock gas.

Under the goal of “dual carbon”, “taking hydrogen and retaining carbon” has become an inevitable choice for the clean utilization of coal, and underground coal pyrolysis provides a new idea for increasing domestic tar and gas production. Scientific prediction of underground tar-rich coal pyrolysis capacity is critical for project economics and energy return assessment, but fewer studies have been conducted on the underground coal pyrolysis in mid to deep layers, and pyrolysis experiments on block coal considering real confining pressure conditions have not yet been reported. To predict underground tar-rich coal pyrolysis capacity and identify the laws of oil and gas production, this paper proposed a horizontal well development method suitable for underground coal pyrolysis in mid to deep layers based on the characteristics of underground coal pyrolysis. Block coal overburden pyrolysis experiments were conducted on two sets of main coal seams in the Santanghu Basin. The overlying pyrolysis yield evaluation model of tar-rich coal in Badaowan Formation based on Boltsmann function and the productivity prediction method of U-shaped horizontal well were established. The variation law of tar and coal gas production capacity and energy return rate were discussed. The results show that: ① Underground coal pyrolysis has the advantages of high resource abundance, clean and low-carbon gas products, and low geological risk. U-shaped, L-shaped and multi-branch horizontal Wells can be produced intermittently or continuously. ② The coal of Badaowan Formation has a higher tar and coal gas yield than that of Xishanyao Formation. Tar production reaches its peak at 400−500 ℃, confining pressure also has a negative effect on reducing the mass transfer capacity of pyrolysis products and a positive effect on improving heat transfer efficiency. When the temperature is lower than 400 ℃, the negative effect dominates, and the positive effect gradually dominates as the temperature rises. The coal gas production increases rapidly at 300−400 ℃, slows down at 400−600 ℃, and rapidly decreases after 600 ℃. H₂ and CO in coal gas increase monotonously with increasing temperature. CH₄ and CO₂ increase first and then decrease with temperature, the effect of confining pressure on the two sets of coal is different, and the application of confining pressure is more beneficial to coal gas production of Badaowan Formation coal. ③ Tar-rich coal pyrolysis product yield shows an S-shaped variation pattern of “slow increase - rapid increase - tends to stabilize” with increasing temperature, the Boltsmann function can better fit the law of tar-rich coal pyrolysis product yield. The linear and triangular well patterns form rectangular and circular temperature fields, respectively. To reach the effective pyrolysis temperature (350 ℃) required for the coal seam between wells, the well spacing of horizontal wells is 4.5 and 5.5 meters respectively, which shows that the heating effect of triangular well pattern is better than that of linear well pattern. ④ Tar and coal gas productivity is divided into three stages: low production in the early stage, rapid production in the middle stage, and stable production in the late stage. According to 1 W/(m·℃) coal thermal conductivity, the production capacity of tar, methane and hydrogen in a single U-type well for 5 years is expected to reach 1.56×10⁴ t/a、260.21×10⁴ m³/a and 201.83×10⁴ m³/a, and the energy return rate can reach 2.09. The mass ratio of pyrolysis water and tar in pyrolysis products is the largest, and the production capacity is the first to stabilize. The mass proportion of CH₄ and CO₂ in coal gas is the highest, CO₂ increases first and then decreases with production years, while CO and H₂ increase monotonically with production years. The production capacity contribution in the later stage of heating is mainly from CO and H₂ in the coal gas. ⑤ In the case of equal calorific value, underground coal pyrolysis reduces carbon emissions by 97% compared with surface coal combustion, ideally, and the CO₂ produced can be absorbed and buried through the semi-coke layer to achieve carbon neutrality. Overall, underground coal pyrolysis has the resource base, technical feasibility and good economic prospect for scale development, which is a new technology for clean and low-carbon development of fossil energy with great development potential.

Detection and identification of faults are crucial in the process of coal exploration and mining, and the traditional manual method of fault interpretation can no longer meet the needs of actual production, and the deep learning-based seismic fault interpretation method performs better in the field of fault segmentation. Conventional convolutional neural network (CNN) has limited sensory field and cannot make good use of the global information, which will lead to some predicted faults with insufficient continuity and missing faults, etc. Transformer has the advantage of extracting global information, and introduces the TransUNet network which is a fusion of CNN and Transformer to construct a CBAM- based seismic fault identification method. TransUNet seismic fault identification method to identify 2D seismic fault images. Firstly, the CBAM-Block attention module is integrated into the TransUNet network, and the module is added into the CNN tomography encoder part and the 3-layer jump connection part connecting the tomography encoder and the tomography decoder, respectively, to enhance the recognition ability of the seismic tomography image from two dimensions, namely, the channel and the space; secondly, the loss function optimised jointly by the Dice loss function and the cross-entropy loss function is selected to make the segmentation of the tomography image more accurate. function and cross-entropy loss function to make the fault image segmentation more accurate, and the DICE and IOU values obtained by the CBAM-TransUNet fault identification network on the synthetic seismic dataset are increased to 0.84 and 0.75, respectively, and the experimental results show that the continuity of the fault identification is stronger, which is obviously superior to other classical segmentation methods; finally, the constructed model is used to interpret the faults on the real seismic dataset of the F3 block of the North Sea, off the coast of the Netherlands. Finally, the constructed model was used to interpret the faults in the real seismic data set of Block F3 in the North Sea off the Netherlands. The experimental results show that the seismic fault identification method based on CBAM-TransUNet can effectively identify the faults while removing the redundant fault information, and performs well in terms of fault identification accuracy and fault identification continuity, and the identified faults are richer in details, which improves the accuracy of fault identification, and can be effectively applied to identify the faults in the real seismic data.

During the production of metallurgical industry and the development of coal resources, a large number of solid wastes that are difficult to be effectively utilized are produced, accompanied by surface subsidence, solid waste stockpiling and high carbon emissions. In order to achieve the goal of "coal mine loss reduction mining-functional utilization of solid waste-CO₂ low-carbon disposal", this study innovatively proposed the key technologies of CO₂ mineralization multi-source solid waste preparation of carbon fixation mining materials and multi scenario utilization.Taking the modified magnesium coal based solid waste (including modified magnesium slag, fly ash and coal gangue) as an example, the direct mineralization method was used to mineralize it on the ground to prepare carbon fixation mining materials, so as to meet the application requirements of multiple scenarios in the mine. In this paper, the process of direct mineralization of solid waste and its key influencing factors were systematically analyzed, and the modified magnesium coal based solid waste carbon fixation mining materials were prepared. The basic properties (flow performance, strength performance, carbon fixation ability) and carbon fixation mechanism of the modified magnesium coal based solid waste carbon fixation mining materials under different liquid-solid ratios were studied.The results show that when the liquid-solid ratio is greater than 0.23, the material meets the backfill flow performance requirements, and the maximum 28 days compressive strength can reach 6.18 MPa; The mineralization efficiency of direct mineralization mixing for 10 minutes reached 50.7%. Aiming at the problem of multi scene utilization of multi-source solid waste based carbon fixation mining materials, this paper puts forward the key technologies of multi scene utilization, including "carbon fixation mining prefabricated parts, carbon fixation paste backfill mining, carbon fixation mining materials for goaf treatment, and carbon fixation backfill materials for mine cooling". Based on the carbon fixation mine prefabricated parts, the integrated technology and equipment of high-strength and low-permeability reservoir wall construction technology and roadway excavation floor laying are proposed; On the basis of paste backfill mining in the mine, this paper innovatively puts forward the room and pillar coal mining carbon fixation backfill coal pillar recovery technology and the integrated equipment of efficient preparation and backfill application of metallurgical coal based solid waste carbon fixation backfill material. In addition, in the application of goaf treatment, it is also necessary to study the adsorption diffusion mechanism of CO₂ in solid waste materials, the multi field coupling mechanism between grouting materials and the environment, and the CO₂ efficient absorption mixing reaction device, and establish the application system of "goaf hazard monitoring-solid waste mineralization grouting material treatment-grouting effect evaluation". This study provides a useful reference for the rational disposal of bulk metallurgical coal based solid waste and the efficient storage of CO₂, and is of great significance to promote the realization of the dual carbon goal and the transformation and development of coal mining areas from "zero carbon" to "negative carbon".

In order to solve the problems of surface runoff disorder, poor water connectivity, and weak hydrodynamic water circulation capacity in high groundwater level mining areas in the east, and to reduce the non-point source pollution and point source pollution caused by agricultural and industrial production spaces around a large number of collapsed water bodies entering the water bodies of collapsed areas through surface runoff, which leads to water quality degradation and water ecological environment risks, this paper innovatively proposes a new technology for the systematic protection and restoration of water bodies in coal mining collapsed areas and the health of the ecological system in collapsed areas through a systematic protection and restoration approach. Based on the concept of systematic protection and restoration of mountains, rivers, forests, fields, lakes, grasses, and sands, the optimization of landscape patterns in key areas, and the principle of systematic regulation of surface runoff, a new technology for the systematic protection and restoration of water bodies in collapsed areas combining "connectivity+pollution interception" is proposed. The main technical contents include: Analysis of surface runoff network using precision DEM Various water body identification and precise monitoring of water surface elevation, construction of water connected corridor network and evaluation of hydrodynamic enhancement effect, calculation of suitable range of water vegetation buffer zone, spatial identification of missing vegetation buffer zone, evaluation of water protection and restoration effect, and other technical aspects. This article takes the Yanzhou mining area in Shandong Province as an example to conduct simulation analysis on the application of systematic protection and restoration technology for collapsed water bodies based on surface runoff regulation. The results show that: ① by building water connection corridors at key locations and using hydrodynamic enhancement technology based on water connection, 45 ecological source areas were effectively connected. After connection, the maximum connection distance from east to west in the study area increased by 5 times, and the overall connectivity of the watershed was improved. The average water velocity in the corridors reached 0.067 m/s, significantly improving the hydrodynamic conditions in the mining area; ② By using the pollutant interception technology based on the spatial optimization layout of vegetation buffer zones in key areas, with water connected corridors and ecological source areas as key areas, the Phillips hydrological model was used to calculate that the required vegetation buffer zone width in the Yanzhou mining area is mainly concentrated between 15～35 m, with a total area of 5.59 km², of which 18 km² is already covered by vegetation and 41 km² is missing vegetation buffer zone to be constructed; ③ The results of SWAT scenario simulation analysis further verified that the model has a significant effect on the protection and restoration of water bodies in mining areas. Through this model, pollution can be reduced by at least 10.14%～15.5%, and the removal effect of phosphorus element is particularly significant. The systematic protection and restoration technology proposed in this article for coal mine subsidence areas is a typical combination of landscape ecology and ecological hydrology in the ecological protection and restoration of mining areas. It has important reference value for other types of areas to achieve regional systematic protection and restoration through surface runoff regulation.

Cracking the soil and water loss effects of mining-induced surface fissures in the coal mining area of the middle reaches of the Yellow River is of great significance for ecological environment protection and high-quality development in the coal mining region of northern Shaanxi. Taking the soil around the mining-induced ground fissures with widths of 0−10, 10−20, 20−30 cm (within 80 cm in horizontal distance and shallower than 20 cm in vertical depth) in the typical mining-induced ground fissure development area in the north wing of Ningtiaota mine field in northern Shaanxi as the research object, the soil infiltration rate, cumulative infiltration, saturated hydraulic conductivity (K_s), organic matter, mechanical composition and > 0.25 mm water-stable aggregates were measured by constant head method and instrument analysis method, respectively. The influence of mining-induced ground fissures on soil infiltration characteristics was revealed. Based on the RUSLE2 model calculation, the soil erosion effect on the small spatial scale of mining-induced ground fissures considering infiltration characteristics is clarified. The results showed that: ① The infiltration rate of soil around the mining-induced fissures exhibits a dynamic variation process over time, characterized by three stages: transient (0−3 min), gradual (3−60 min), and stable (60−110 min). ② The effect of mining-induced ground fissure development on soil Ks is the most significant, with an average increase of 60.63%. This effect increases with the increase of mining-induced ground fissure width and the decrease of horizontal distance from ground fissure. ③ Soil cumulative infiltration and Ks were significantly positively correlated with very fine sand (p < 0.01), but significantly negatively correlated with clay and organic matter (p < 0.01), and significantly negatively correlated with > 0.25 mm water-stable aggregates (p < 0.05). ④ The variation range of erodibility K-value calculated by considering infiltration characteristics is 1.12−2.13 times larger than that without considering infiltration characteristics. Based on the exponential function, the prediction model of the influence range of mining-induced ground fissures with different widths on the infiltration rate and erodibility K-value of the surrounding soil was constructed. It was found that when the horizontal distance from the mining-induced ground fissures exceeded 226 cm and 157 cm, respectively, the effect of mining-induced ground fissures on increasing the infiltration rate and erodibility of the surrounding soil basically disappeared. It can be used as a precise prevention and control target area for soil erosion in the loess mining-induced ground fissure development area in the middle reaches of the Yellow River.

Biochar application is a key measure for enhancing soil quality. However, the impact of biochar applications on the reclaimed soil for improvement on soil physicochemical properties, enzyme activity and microbial diversity is still unclear, especially for the promotion mechanism of microbial carbon sequestration capacity. This study applied three kinds of biochar originated from straw containing rice straw, wheat straw, and corn straw to mine reclaimed soil, measured the effects of biochar addition on the physicochemical properties, enzyme activity, and carbon management index of reclaimed soil, and analyzed the variation of soil microbial community structure and carbon sequestration functional genes. From the experimental results, the main conclusions are shown as follows: ① The soil pH, electrical conductivity, ammonium nitrogen, nitrate nitrogen, available phosphorus, and available potassium content in the biochar-added groups significantly increased (P < 0.05), and the activities of β-glucosidase (BG), cellobiohydrolase (CBH), and leucine aminopeptidase (LAP) were enhanced, whereas the activity of β–N-acetylglucosaminidase (NAG) decreased by 15.0% to 25.0%. ② Biochar addition increased the α diversity index of soil microbial community, while the effect on bacterial α diversity index was significantly higher than that of fungi. Biochar addition increased the relative abundance of Proteobacteria and Chloroflexi (P < 0.05), while decreased the relative abundance of Actinobacteriota. In addition, it reduced the relative abundance of Ascomycota in fungi and significantly increased the relative abundance of Basidiomycota (P < 0.05). The three biochar treatments enhanced bacterial network complexity, but biochar addition did not significantly affect the fungal network complexity. ③ The soil carbon management index of rice straw biochar, wheat straw biochar, and corn straw biochar treatments increased by 4.7%, 4.8%, and 24.0%, respectively. Compared to the control group, the absolute abundance of carbon sequestration functional gene CBBL (the encoding gene of ribulose bisphosphate carboxylase large subunit) in the straw biochar treatment group significantly increased (P < 0.05). The absolute abundance of carbon sequestration functional gene PMOA (the encoding gene of particulate methane monooxygenase ß subunit) in the corn straw biochar treatment group significantly increased (P < 0.05). Biochar addition significantly improved the correlations among environmental factors, carbon sequestration functional genes, and carbon management index, with the microbial community being the main controlling factor to regulate soil carbon sequestration potential, which could provide important basis for the future ecological restoration of mines, carbon sequestration and sink enhancement.

The region where Inner Mongolia and Shaanxi converge is pivotal for the underpinning of national energy security and is also central to the ecological conservation and sustainable development of the Yellow River Basin. Intensive coal extraction in this zone potentially poses a substantial threat to ecological conservation, notably by undermining the integrity of the shallow Quaternary groundwater environment. Accurate assessment of the leakage from various aquifers within the overburden is a complex task, thereby complicating the development of scientifically sound and targeted strategies for water conservation during coal mining. Our research leverages the principle of isotopic mass balance, following the analysis of environmental isotopes (Deuterium and Oxygen-18) present in the groundwater of the aforementioned border region, to quantify the relative contributions of different mine water sources. Findings indicate that the isotopic signatures in the aquifer waters are influenced by a multitude of factors including topography, stratigraphic configuration, and the nature of groundwater storage. The direct sources of groundwater in the Quaternary aquifer of the study area are atmospheric precipitation and surface water, characterized by rapid circulation and renewal, replenished by modern water with tritium-rich features. The deuterium (D) and oxygen-18 (¹⁸O) values in the groundwater are close to those of atmospheric precipitation and surface water. In the deep-buried Cretaceous aquifer, the hydraulic connection with the Quaternary is tight, and the cycle and renewal process is prolonged, resulting in a decrease in environmental isotope values. The deuterium values in the Cretaceous groundwater range from –80.2‰ to –75.6‰, and the oxygen-18 values range from –10.6‰ to –8.7‰. The groundwater in the Jurassic aquifer, which is controlled by vertical recharge, exhibits a slower cycle and renewal rate, with gradually decreasing δD and δ¹⁸O values. The shallow and moderately deep-buried strata have a long depositional history and better cementation, affected by later tectonic movements, and are in direct contact with the Quaternary or Neogene, receiving replenishment from Quaternary groundwater, thus having relatively higher δD and δ¹⁸O values. In contrast, the Jurassic strata in the deep-buried area, with its substantial thickness and overlying thick layers of Quaternary and Cretaceous strata, have poor groundwater replenishment, a long groundwater flow path, and are relatively closed and stagnant, resulting in relatively lower δD and δ¹⁸O values. The application of the D-value, in conjunction with the binary mixing model, facilitates the quantitative assessment of the contribution of Quaternary waters in shallow-buried coal mine waters. In the case of the SGT and HLG coal mines, the proportion of Quaternary waters is typically less than 20%. In contrast, the Quaternary water content in the BLT and LSJ coal mines varies between 28.0% and 57.0%. Notably, the Quaternary water proportion in the YBJ coal mine approaches 80%, indicating a significantly higher contribution. For the middle and deep-buried coal mine waters, the Quaternary water content is generally less than 20%. However, it is noteworthy that in the HLW and SS coal mines, which have been developed earlier and feature 'skylights' of the Puding Formation red soil layer in the roof, the Quaternary water content has reached 37.05% and 26.24%, respectively. This suggests that under specific geological conditions, the proportion of Quaternary waters may be substantially elevated. In the deep-buried mine waters, the contribution of Cretaceous water is approximately around 30%. IsoSource modeling has calculated that the contribution rate of Quaternary water ranges from 7.6% to 9.3%, the contribution rate of Cretaceous water is between 12.0% and 17.1%, and the contribution rate of the Upper Jurassic water is from 74.9% to 80.4%. Moreover, the contributions of various sources to the mine waters are similar across different mining areas. By using the D content value in groundwater and a binary mixed model, it was calculated that the proportion of Quaternary water in shallow buried mine water was less than 20% for SGT and HLG coal mines, 28.0% to 57.0% for BLT and LSJ coal mines, and nearly 80% for YBJ coal mines; The proportion of Quaternary water in the mine water in the middle and deep buried areas was generally less than 20%. The proportion of Quaternary water in HLW and SS coal mines, which were developed earlier and had a “skylight” in the red soil layer of the Baode Formation on the roof, reached 37.05% and 26.24% respectively. The proportion of Cretaceous water in deep buried mine water was about 30%. The IsoSource model calculates that the contribution rates of Quaternary water were between 7.6% and 9.3%, Cretaceous water was between 12.0% and 17.1%, and the contribution rates of upper Jurassic water were between 74.9% and 80.4%. The contribution rates of various sources of mine water in different mining areas were similar. This study accurately identified the proportion of water sources in various aquifers of mine water, which was of great significance for ecological environment protection and green and sustainable development of coal resources in the contiguous area of Inner Mongolia and Shaanxi. Accurately identifying the source proportions of water from various aquifers in mine water is of significant importance for the conservation of water resources and ecological protection in the coal mining areas bordering Inner Mongolia and Shaanxi. This study aims to provide a precise delineation of these proportions, thereby contributing to sustainable mining practices and the preservation of the ecological environment in the region.

To explore the microbial community characteristics and their response to environmental factors in different environmental areas of an underground coal mine, a study was conducted in the Xieqiao coal mine in Huainan, Anhui. A total of 24 water samples were collected from eight underground environmental areas involved in the entire process of mine water sourcing, formation, and accumulation, including the shaft, rock roadway, coal roadway, coal face, goaf, sump, sandstone water outflow point, and limestone water discharge point. These samples underwent hydrochemical composition analysis and high-throughput sequencing of the 16S rRNA gene. Multivariate statistical methods were employed for sequence data processing. The results showed that ① the shaft water is of Cl-Na·Ca type, the sandstone water and goaf water are of HCO₃·Cl-Na type, and the other areas are all of Cl-Na type. Significant variations were observed in the concentrations of Na⁺, Cl⁻, ${\mathrm{SO}}_4^{2-}$, ${\mathrm{HCO}}_3^-$, ${\mathrm{NO}}_2^-$, ${\mathrm{NO}}_3^-$, and Fe among the different environmental areas waters. ② The microbial richness and diversity were highest in the sump water and lowest in the rock roadway water. A total of 55 bacterial phyla and 621 genera were detected across the 24 samples, with Pseudomonadota, Bacteroidota, and Nitrospinota as the dominant phyla, and Hydrogenophaga and Pseudomonas as the dominant genera. Pseudomonadota had the highest abundance in the rock roadway water and the lowest in the limestone water; Bacteroidota were most abundant in the sump water and least in the rock roadway water; Nitrospinota were most abundant in the limestone water and least in the rock roadway water. Hydrogenophaga showed a relatively high abundance across all environmental areas waters, while Pseudomonas was mainly distributed in the rock roadway water. ③ The underground microbial community structure and distribution in the coal mine were primarily influenced by pH, followed by nutrients such as C, N, and S, temperature, DO, ORP, and redox-sensitive substances like Fe, Mn, and Sb. ④ FAPROTAX analysis indicated that the microbial communities in this coal mine exhibited general functions of chemoheterotrophy and aerobic chemoheterotrophy. The microbial communities in water bodies of different environmental areas exhibited diverse ecological functions, ranging from basic metabolic activities such as material cycling and energy conversion to complex environmental remediation processes such as pollutant degradation and water quality improvement. These functions maintained the ecological balance of underground water bodies in coal mines and played an important role in regulating and restoring ecosystems.

To clarify the influence of core wettability on the seepage process during the CO₂ saline aquifer storage, this paper studies the influence of wettability change in the saline aquifer on the seepage process based on the pore-level seepage model combined with nuclear magnetic resonance (NMR) technology, providing theoretical support for revealing the two-phase seepage law under the effect of wettability. Firstly, the saturation parameters during the seepage process are measured by NMR technology in this paper, and the quadratic function coupling relationship between wettability and brine saturation is quantitatively analyzed. Later, based on the level set method at the two-dimensional level, by setting wettability as different wetting levels and spatial position functions, the influence of different wettability of the reservoir in displacing brine in the porous medium by CO₂ on the seepage process is simulated. It was found that based on the functional coupling relationship between nuclear magnetic resonance longitudinal relaxation time (T₁) and transverse relaxation time (T₂) and saline water saturation (S), the core wettability changes during CO₂ displacement of saline water could be well characterized. Based on the pore-scale seepage model representing the isotropy of wettability at the pore scale, it was discovered that when the core wettability was in extreme conditions, such as strongly hydrophilic (θ = 0°), neutrally wetted (θ = 90°), or strongly hydrophobic (θ = 180°), the residual water saturation was lower and the displacement effect was better. For anisotropic wettability, the displacement process was more complex, and its influence on relative permeability and residual saline water saturation varied. Especially, different wettability manifestations at the inlet and outlet ends would directly affect the two-phase seepage process. When the inlet end was more hydrophilic and the outlet end was more hydrophobic, the saline water seepage velocity was faster; this might be due to the anisotropic wettability causing the uneven distribution of seepage behavior, thereby resulting in spatial and temporal differences in seepage rate and displacement efficiency; it can be seen that the physical characteristics of the seepage channel have a significant influence on the seepage process. Future research needs to focus on the different effects at time scales in addition to the associated changes at spatial scales in the saline aquifer.

The ignition temperatures of coals/low-temperature pyrolysis chars obtained by existing thermal analysis are 200–300 K lower than those of coals in boilers. It is generally believed that the low heating rate β of the thermal analyzer is the main reason for the above results, but the essential reason should be that the reactivity of the sample selected in the previous study is too high, which leads to the advance of coal/char ignition. Meanwhile, the commonly used TG-DTG tangent method is not accurate enough to calculate the ignition temperature. In order to solve the above problems, the nonisothermal TG-DSC was used to obtain the ignition characteristics of two high-temperature (1 400 ℃) fast pyrolysis Zhundong coal chars under different βs, including specific heat capacity, ignition temperature and ignition heat, and the effect of β on the ignition characteristics of coal chars was investigated. The specific heat capacity of coal char was obtained by David Merrick model, which was not affected by β but related to the change of temperature. The relationship between specific heat capacity and temperature was described by an exponential function. The specific heat capacity values of the two types of coal char are 0.65–1.99 kJ/(kg·K) in the range of 0 to 1 600 ℃. The ignition temperature of coal char was obtained by the DSC or DTG inflection point method based on Semenov thermal explosion theory and the TG-DTG tangent method. The results show that the ignition temperatures obtained by the DSC and DTG inflection point method were equivalent, and always higher than that obtained by the TG-DTG tangent method. The ignition temperature increased with the increase in β, but the level of increase gradually decreased, which can be described by an exponential function. The Limiting ignition temperatures of coal chars were obtained by setting β as the commonly heating rate of coal conversion in boilers, namely 10⁵ K/s. The Limiting ignition temperatures of coal char obtained by DSC inflection point method and TG-DTG tangent method are 673–680 ℃ and 644–659 ℃, respectively. The former is consistent with the ignition temperature of the same type of coal samples obtained in boiler-like environment reactors such as the entrained flow reactor, as in the literature, while the latter will underestimate the ignition temperature. Combined with the fact that the reactivity of high-temperature pyrolysis char is lower than that of coal/low-temperature pyrolysis char, indicating that the preparation of high-temperature (equivalent to the boiler ambient temperature) pyrolysis char with appropriate reactivity and the use of DSC or DTG inflection point method to obtain the limiting ignition temperature of char can realize the prediction of coal ignition temperature in boiler by thermal analysis. According to the Limiting ignition temperature, the ignition heats q_ig of the two coal chars in the boiler are 3 414–3 669 kJ/kg, and the theoretical ignition heats of the two coal chars under the air/coal ratios of 0.9–2.5 were calculated to be 1 826–2 811 kJ/kg. q_ig is larger than the theoretical ignition heat value of the corresponding coal char, indicating that the theoretical ignition heat value may overestimate the actual ignition capacity of coal in boilers. This study provides a comprehensive interpretation of the rationality of thermal analysis to obtain the coal ignition characteristics in boilers. The proposed thermal analysis methodology can provide a reference for obtaining the basic data required for CFD simulation of coal ignition characteristics in boilers.

The co-firing of biomass with coal is one of the technologies to reduce the carbon emission from the coal-fired power plant. The position of biomass co-firing has a significant impact on NO_x emission during the co-firing process. Therefore, in order to study the effect of the biomass co-firing position and the temperature on the NO_x emission, a two-stage drop-tube furnace was used to study the NO_x emission of biomass co-firing with coal from the primary combustion zone and the burnout zone as well as the migration of fuel N. The results show that NO_x emission behaviors are significantly different when biomass is mixed from the primary combustion zone and the burnout zone. When biomass is mixed from the primary combustion zone, NO_x emission at studied temperature shows a decreasing trend with the increase of the biomass co-firing ratio from 0 to 40%, with the increase of the over-fire air ratio, the lowest NO_x emission occurs when the ratio is 0.33. When biomass is mixed from the burnout zone, the NO_x emission decreases continuously with the increase of the biomass co-firing ratio from 0 to 40% at the burnout temperature of 1 000 ℃. At the burnout temperatures of 1200 and 1400 ℃, the NO_x emission is lowest when the biomass co-firing ratio is 10%. There is a significant difference in the conversion of fuel N to intermediate products of HCN and NH₃ during biomass co-firing in the burnout zone. At the studied burnout temperature, when biomass is mixed in the burnout zone, the conversion rate of fuel N to HCN always increases with the increase of biomass co-firing ratio. The conversion of fuel N to NH₃ increases with the increase of biomass co-firing ratio at the burnout temperature of 1 000 ℃; when the burnout temperatures is 1200 and 1 400 ℃, the conversion rate of NH₃ is the highest at biomass co-firing ratio of 10%. When the primary zone temperature is 1 200 ℃ and the burnout temperature is 1 400 ℃, about 94% of the fuel N is converted to N₂ and ash N, about 5% is converted to NO_x, and less than 1% is converted to HCN and NH₃. The co-firing of biomass can reduce the conversion of fuel N to NO_x compared to pure coal combustion. However, as the biomass co-firing ratio increases, the conversion rate of fuel N to NO_x and ash N increases, and the conversion rate of fuel N to N₂ decreases.

Under the dual-carbon goal, the resource utilization of CO₂ driven by clean and renewable solar energy has become an important research topic. However, the previous reports have mostly used high-purity CO₂ as the research object, while the CO₂ concentration in the flue gas emitted by coal-fired power plants is only 3%−15%. To avoid the high-energy CO₂ enrichment process, photocatalytic directional conversion of low concentration CO₂ into high-valued fuels or chemicals has important scientific significance for energy saving, emission reduction and its resource utilization. Cobalt-aluminum layered double hydroxide (CoAl−LDH) was firstly prepared by coprecipitation-hydrothermal method and visible-light catalysts Ru/CoAl-LDH were constructed by loading ruthenium nanoparticles onto the surface of CoAl-LDH via surface impregnation coupled with hydrogen heat treatment. The unique surface composition and structural characteristics of Ru/CoAl-LDH composites are conductive to implement deep photoreduction of low concentration CO₂ using H₂O as the hydrogen source. Structural composition and micro-morphology of the composite catalysts Ru/CoAl-LDH were determined by X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and ultraviolet-visible diffuse reflection spectroscopy. The results indicate that the loaded Ru species is zero valence state of metal Ru. Loading Ru has no effect on the nano-lamellar morphology of CoAl-LDH, but can significantly improve the photoresponse performance of composite catalysts. By using Ru/CoAl-LDH as photocatalysts, H₂O as electron donor and hydrogen source, and 10% CO₂/N₂ mixture as simulated flue gas, the effect of Ru loading amount on the productivity of CO₂ reduction products and the selectivity of deep reduction products were investigated under visible light irradiation. 1.6% Ru/CoAl-LDH exhibited the optimal CO₂ photoreduction performance. After 3 hours of visible light irradiation, the productivity and selectivity of deep reduction product methane reached 452.4 μmol/g and 86.3%, which were 10.4 and 3.3 times of single CoAl-LDH, respectively. Meanwhile, the performance enhancement mechanism on deep photoreduction of low concentration CO₂ was explored by using CO₂ adsorption isotherms, in-situ XPS, transient photocurrent and impedance spectroscopy. The —OH groups on the surface of CoAl-LDH facilitate selective adsorption of composite catalysts for low concentration CO₂. Excellent H₂O oxidation performance of CoAl-LDH can provide sufficient in-situ hydrogen source for deep photoreduction of CO₂, without the use of H₂ having explosive risk. As the photoelectron acceptor, the loaded Ru can not only enhance the separation and migration efficiency of photogenerated charges, but also implement multi-electron reduction as active reductive sites of CO₂. Therefore, the synergistic effect of CoAl-LDH and cocatalyst Ru is the primary reason for the improvement of low concentration CO₂ deep photoreduction performance. The composite catalysts Ru/CoAl-LDH realize the effective coupling of visible-light water oxidation and low concentration CO₂ deep reduction, providing important theoretical guidance for the construction of essentially safe and low-energy consumptive CO₂ conversion system. It also provides a new idea for the resource utilization of CO₂ from coal flue gas.

Due to the light weight, high strength, and long blades of wind turbine blades characteristics, it has been a difficult problem for the recycling in the solid waste industry. The thermochemical treatment of retired wind turbine blades is a technology with great potential for large-scale industrial application. In response to the issue of pollutant emissions during the thermochemical treatment process, the pre-treated wind turbine blades thermal conversion experiments were conducted on a tubular electric furnace experimental platform under four different temperatures of 400, 600, 800, and 1000 ℃ during N₂, CO₂, and air atmospheres, respectively. The pollutants emissions containing nitrogen and chlorine were tested. Under the CO₂ and N₂ ambience, HCN and NO are the main nitrogen-containing pollutants. As the temperature increases, HCN gradually increases. At 1000 ℃, HCN-N is the most important nitrogen-containing component, accounting for 88.3% of total nitrogen. However, the proportion of HCl-Cl to total chlorine fluctuates little, maintaining around 5%. Under the air ambience, NO is the main nitrogen-containing pollutant, with a peak concentration of 918.3 × 10⁻⁶. Moreover, the oxygen in the NO mainly comes from the wind turbine blades themselves, rather than the external air. As the temperature increases, HCl and HCN gradually decrease, reaching their maximum at 400 ℃, accounting for 46% and 8.4% of total chlorine and total nitrogen, respectively. CO₂ has a significant promoting effect on the distribution of products, which is related to temperature and composition. CO₂ can significantly promote the generation of HCN and NO at a high temperature of 1000 ℃, but the promotion effect is not significant at a low temperature of 400 ℃. At a low temperature of 400 ℃, CO₂ has a significant promoting effect on the generation of NO₂, while at a high temperature of 1000 ℃, CO₂ has no significant promoting effect on the generation of NO₂. Considering that the oxygen generated by NO mainly comes from the blades themselves, traditional air classification is not effective in reducing nitrogen oxides.

To address the problems of low accuracy of video AI recognition of personnel intrusion hazardous areas in fully mechanized mining face caused by factors such as variable personnel scales, and dynamic changes of hazardous areas, an intelligent recognition method for personnel intrusion hazardous areas of fully mechanized mining face based on RSCA-YOLOv8s and automatic division of hazardous areas is proposed. To address the problem of low accuracy of personnel recognition in fully mechanized mining face, the RFAConv-SE (Squeeze-and-Excitation with Receptive-Field Attention Convolution) and CCNet (Criss-Cross Attention Network) attention modules are introduced on the basis of the YOLOv8s model to improve the capture ability of the model for global and contextual information in complex background images. The multi-scale and small target personnel feature extraction ability of the model is improved by fusing the Res2Net network through the C2f module. The adaptive fusion ability of the model for multi-scale personnel features is enhanced through the improved SPC-ASFF (Adaptive Structure Feature Fusion with Sub-Pixel Convolution layer). To address the problem of dynamic changes of hazardous areas within the field of view caused by the dynamic changes of the camera on fully mechanized mining face following the hydraulic support, an automatic division method of hazardous areas based on the extraction of key feature points of landmark targets such as the guard plate and coal baffle plate is proposed. To address the problems of irregular changes of hazardous areas and the difficulty of parameter setting of the judgment method based on overlap degree, a precise recognition method for personnel intrusion hazardous areas based on the ray method to determine the positional relationship between the pixel coordinates of personnel and hazardous areas is proposed. Through ablation experiments, comparison experiments between RSCA-YOLOv8s and methods such as YOLOv5s and YOLOv8-SPDConv, as well as test experiments on automatic division of seven groups of multi-scene hazardous areas and recognition of five groups of personnel intrusion into hazardous areas in fully mechanized mining faces,the results show that the accuracy of the personnel recognition method of RSCA-YOLOv8s is higher, reaching 97.2%, which is 1.1% higher than the baseline model mAP@0.5 and 2.5% higher than mAP@0.5:0.95. It has more accurate recognition ability and higher recognition accuracy for small target personnel. The average accuracy of the automatic division of hazardous areas by this method is 97.285% and the discrimination accuracy of personnel intrusion hazardous areas is more than 98%.

The propagation of methane gas in coal is closely linked to the particle size distribution characteristics of coal particles, which in turn affects the safe mining and utilization of coal. With the continuous development of digital image processing technology, coal particle morphology detection based on digital image segmentation has become the mainstream method for obtaining the particle size distribution characteristics of coal particles. In the process of digital image segmentation, global information and edge details play a crucial role and directly affect the accuracy of the segmentation results. The U-shaped network based on convolutional neural network architecture focus too much on local information, neglecting the importance of global information, which can lead to over-segmentation. On the other hand, Transformer-based networks effectively model global information using multi-head self-attention mechanisms but do not fully utilize edge detail features, resulting in under-segmentation of coal particles. To address these issues, this study proposes an Iterative Squeeze UNet (ISUNet) for coal particle size analysis. The ISUNet model introduces a compressed excitation atrous spatial pyramid pooling module and a Transformer-based multi-path iterative encoder. The compressed excitation atrous spatial pyramid pooling module enhances channel information and global context information of features at different scales, solving the problem of over-segmentation of coal particles. The multi-head self-attention module in the encoder continuously strengthens important edge detail features through dot-product self-attention mechanism, addressing the problem of under-segmentation of coal particles. Compared to five classic image segmentation models and four mainstream segmentation models, ISUNet has shown outstanding performance. Compared to the classic segmentation model TransUNet, it has improved the mean Intersection over Union (mIoU) by 6.6%, the accuracy by 0.3%, and the recall rate by 7.0%. Compared to the current state-of-the-art Segment Anything model, it has improved the mIoU by 4.6%, the accuracy by 0.2%, and the recall rate by 4.9%. In the aspect of coal particle size measurement, the accuracy reached 97.49%. These experimental results fully demonstrate the effectiveness and superiority of ISUNet in coal particle size analysis.

Solid backfilling mining technology has matured, but still faces bottlenecks such as low autonomy and insufficient self-adaptive control capabilities, resulting in a low level of intelligence that affects its application effectiveness and promotion scope. The robotization of large-scale coal mine equipment is an inevitable trend in development of the industry, and it is imperative to research coal mine solid intelligent backfilling support robot and achieve breakthroughs in its key technologies. The concept and system composition of coal mine solid intelligent backfilling support robots are proposed, revealing the mechanism of process self-driven operation. A full-category parameter index set is constructed, and a full-category parameter perception method is formed. The full-condition scenario categories are divided, and an accurate representation and real-time output method of pose were established. A method for judging operating states of the whole working condition and self-regulating robotic arm group is formed. A virtual prototype simulation test platform for solid intelligent backfilling support robot is constructed and three working conditions, “downward mining and upward backfilling” “horizontal mining and backfilling” and “upward mining and downward backfilling”, are set up for process self-driving simulation. The result of simulation test shows that backfilling support robot can accurately identify interference and calculate target parameters to regulation, and intelligent functions such as the overall operation of the system and the self-driven execution of the process have been verified. In view of the key scientific problems faced by the R&D of the coal mine solid intelligent backfilling support robot, the research framework, R&D ideas and technical routes of the coal mine solid intelligent backfilling support robot and their key technologies are preliminarily constructed. It provides theoretical and technical support for in-depth upgrading of backfilling mining technology and R&D of completely independent intellectual property rights of coal mine solid intelligent backfilling and support robot products in China.

Intelligent recognition of coal mine workers and manned vehicles (coal mine pedestrian-vehicles) is an important component of video surveillance systems and a key task in the development of coal mine intelligence. However, the detection scene of coal mine pedestrian-vehicles is complex, and deploying large pedestrian-vehicle detection models on limited computing devices is challenging. Balancing between model detection performance and efficiency poses many challenges. This paper proposes a lightweight coal mine pedestrian detection model based on deep learning and model compression techniques. Taking the coal mine video surveillance dataset in Guizhou region as an example. The model accurately and in real-time completes the task of detecting coal mine pedestrian-vehicles, achieving a balance between model detection performance and efficiency. Specifically, in the network model design phase, a lightweight detection model named FCW-YOLO is proposed based on YOLOv8s as the baseline. Faster-Block and coordinate attention are integrated into the feature extraction module of the network, designing a novel C2f-Faster-CA lightweight architecture to reduce redundant channels of the network while adaptively capturing global key information. Furthermore, the WIOU boundary regression loss function is employed to increase the model's focus on common quality samples, addressing issues such as regression errors caused by imbalanced training samples. In the model compression phase, the proposed FCW-YOLO model undergoes channel-level sparsity through a collaborative pruning algorithm, automatically identifying unimportant channels and reducing them, resulting in the FCWP-YOLO model, achieving secondary lightweight design of the coal mine pedestrian-vehicle detection model. Results on a self-built coal mine pedestrian-vehicle detection dataset show that the proposed model has parameters, computational load, and model size of 2.3 M, 4.0 GFLOPs, and 6.0 MB, respectively, achieving compression ratios of 4.9 times, 4.7 times, and 4.4 times compared to the baseline model. The average detection accuracy is 88.7%, an improvement of 1.1%, with a processing speed of only 5.6ms per image. Compared to various lightweight architectures and advanced detection models, this method demonstrates excellent accuracy, lower computational costs, and better real-time performance, providing a feasible coal mine pedestrian-vehicle detection method for resource-constrained coal mine scenarios, meeting the deployment requirements of coal mine video surveillance and enabling real-time alerts for intelligent inspection of coal mine pedestrian-vehicles.

A magnetoelectric hybrid suspension belt conveyor is introduced as a novel type of continuous transportation equipment characterized by low resistance and low energy consumption. The support system is significantly impacted by the dynamics of the conveyor belt and its connection to the suspension system, where challenges such as unknown modeling errors and coupling disturbances are often encountered, complicating the assurance of system stability. An improved magnetic circuit approach is utilized to establish the electromagnetic model of the suspension support system. Based on the assumptions of a catenary equivalent and section stability, the dynamics equations of the support system are constructed. The system incorporates self-coupling PID control technology and a cross-coupling strategy to achieve coordinated suspension. Initially, considering the distribution of the air gap magnetic field in the magnetoelectric hybrid suspension system and the differences in magnetic circuits, the electromagnetic force variations within the system are described using an improved magnetic circuit formula. This description, integrated with electromechanical relationships, forms the control equation for the electromagnetic forces in the hybrid suspension system. The entire conveyor belt is modeled under the influence of several support points, with assumptions that the material is stable and forms a consistent section across the belt. This simplification leads to a dynamics model of the support system that effectively combines rigid bodies with strings. Subsequently, based on the coupled issues of the dynamics model and the operational conditions for system synchronization, a control strategy for cross-coupled coordination based on self-coupling PID control is proposed. This strategy includes adaptive speed factors for system tracking and coordination control, with proven stability of the coordination control method. The system’s response under lateral, longitudinal, and various disturbance conditions is modeled in simulation studies using a set air gap of 30 mm. The system’s dynamic performance under static suspension and disturbances from air gaps and material loading is validated by experimental research using a suspension experimental rig. The experimental results demonstrate maximum air gap fluctuations and coordination errors of 1 mm under the respective conditions. The control performance and stability of the method are affirmed by both simulation and experimental outcomes, showcasing the feasibility for stable coordination under significant material load disturbances in practical applications.

Recognizing the behavior of key equipment and personnel in fully mechanized mining faces is the foundation and core of intelligent sensing of mining environment information. However, the lighting conditions in fully mechanized mining faces are generally poor. coal dust and water mist can easily cause blurring of the video image, making it difficult to extract key features for identifying target behaviors. As a result, this affects the accuracy of identifying the behavior of equipment and personnel, failing to meet the requirements for practical engineering purposes. In order to address this problem, a multi-information self-attention model and feature fusion mechanism have been developed based on the ResT network architecture. This model expands the information source for feature extraction from pure spatial information to multi-information, including space, time, and channel. This enhancement improves the model's capability to recognize the target's behavior. Among the aforementioned categories, spatial information is a detailed spatial analysis of the target behavior, showcasing a range of deep features such as texture, location, and shape of the target. Temporal information refers to extracting temporal features of the target behavior from continuous video frames, reflecting the order of occurrence of the behavior as well as the evolutionary relationship. Channel information represents the expansion and depth of spatial and temporal levels by extracting spatial and temporal information from multiple perspectives. It characterizes the raw data on feature channels, which provide global features of the target behavior. The effectiveness of our algorithm has been validated through comparative experiments on the dataset for behavior recognition in fully mechanized mining faces. The experimental results demonstrate that the accuracy of behavior recognition can reach 96.90% in the fully mechanized mining faces environment. In comparison with mainstream behavior recognition algorithms such as Swin-Transformer and Timesformer, the recognition accuracy is enhanced by 11.06% and 10.62% respectively. The algorithm is transformed by an ONNX model and accelerated using TensorRT to enable GPU inference, thereby enhancing its value for engineering applications. Consequently, the fully mechanized mining face behavior recognition system was developed. The algorithm model was embedded into the pipeline of the behavior recognition system as a plug-in unit. This integration enables real-time analysis and accurate recognition of crucial equipment and personnel behaviors on the fully mechanized mining faces within the DeepStream framework.