China is rich in deep coal resources. With the continuous depletion of shallow coal resources, deep coal mining is imperative. Currently, over 40 coal mines in China have reached or exceeded a mining depth of 1 000 meters, with the deepest reaching 1 510 meters, mainly distributed in the central and eastern regions and the northeastern mining areas. Additionally, some mining areas in the west, such as the Ordos, Longdong, and Binchang mining areas, have also entered deep mining. Compared with medium and shallow mines, deep mines are characterized by high ground stress, strong mining-induced disturbance, large deformation (in soft rock) and strong impact (in hard rock). The deformation of the surrounding rock in deep mine roadways is marked by strong dilatancy, strong rheology and severely impact damage . The stress environment and geomechanical properties of the surrounding rock in deep roadways were deeply analyzed, and the deformation and failure characteristics of the surrounding rock in deep soft rock roadways were studied. It was found that the large deformation in deep soft rock roadways was mainly caused by three types of deformation: dilatancy, rheology of coal and rock mass, and structural rheology. The mechanism of large deformation and instability of the surrounding rock in deep soft rock, high stress and strong mining-induced disturbance roadways was revealed. The concept of coordinated control of surrounding rock support, modification and pressure relief in deep roadways was proposed. The fundamental principle of this coordinated control was expounded. The spatio-temporal coordinated action of various surrounding rock control methods was analyzed. The principle of “three active” coordinated control of surrounding rock support, modification and pressure relief in deep roadways was clarified. Different coordinated control methods of surrounding rock in deep roadways were proposed. The “three-in-one” coordinated control technology of surrounding rock support, modification and pressure relief was developed, including high prestressed bolts and cables and thin spray active support, high-pressure splitting grouting active modification, and hydraulic fracturing active pressure relief technology. The grouting bolting with high pretension and pressure in synergy control technology was developed for the advanced section of the working face to strengthen support, forming a complete surrounding rock control technology for deep working face roadways (including gateway, open-off cut and advanced area). New materials for bolting, such as a 700 MPa ultra-high-strength, ultra-high elongation (30% post-fracture), and high-impact toughness bolt, was developed. Three types of high injectability, high adhesion and high strength grouting materials, including nano-modified coal and rock-friendly single-liquid inorganic-organic composite grouting materials and micro-nano double-liquid inorganic-organic composite grouting materials, and high strength and high toughness roadway surface spraying protective materials were developed. Other innovations include the development of high prestressed grouting bolts and cables with high pressure, as well as 35 MPa pneumatic and 45 MPa hydraulic high-pressure grouting pumps, plus a pressure-flow-density multi-parameter grouting monitoring system have been developed. Underground local hydraulic fracturing equipment and underground directional long horizontal borehole large-flow hydraulic fracturing equipment with high-pressure were developed. The complete set of coordinated control technology for deep roadway surrounding rock was systematically integrated and successfully applied in complex and difficult roadways in deep mining areas such as Xinji, Xinwen, Huaibei, Wanbei and Binchang, including deep soft rock roadways, ultra-deep high stress roadways, deep strong mining-induced disturbance roadways, deep soft and broken surrounding rock roadways and deep thick hard roof strong impact roadways. The deformation of the surrounding rock in roadways was significantly reduced, and the stability of the surrounding rock was significantly improved, which strongly support the safety and efficient production of deep coal mines. Finally, the development directions of the theory, technology, materials and equipment for the control of deep roadway surrounding rock in the future were prospected.

Grouting modification is an effective means for reinforcing fractured coal roadways, with the regulation of the coal-slurry interface being the core of grouting modification. This article analyzes the current status and existing issues of grouting modification technology in coal roadways and introduces a new method and material for in-situ reaction enhancement of the coal-slurry interface modification, along with its application effects in underground mines. Focusing on the key issue of the in-situ reaction mechanism for enhancing the bonding of the coal-slurry interface, this study develops a novel inorganic grouting material based on the distribution and morphology of coal fractures, as well as the physical topography and chemical structure of the coal surface. A pioneering nanoparticle delivery system is created to achieve compatible delivery of the components of the inorganic grouting material. The nanoparticles exhibit a typical core-shell structure and pH-responsive characteristics, remaining stable in neutral environments during storage and transportation. However, in the alkaline environment of cementitious material hydration, the nanoparticles decompose and release internal active molecules. These molecules enhance the interface by forming hydrogen bonds at the coal-slurry interface. Combined with dynamic interface wetting experiments, the structural evolution mechanism of the in-situ reaction between organic components and chemical groups on the coal surface is elucidated at the molecular level. The active molecules delivered by the nanoparticles use the terminal hydroxyl groups on the coal surface as initiators to undergo in-situ reactions at the coal-slurry interface, generating polymer macromolecules. These macromolecules act as “molecular bridges” at the coal-slurry interface, improving the bonding strength and the effectiveness of grouting modification. During the hydration of the grouting material, the nanoparticles serve as crystal nuclei, promoting the nucleation and growth of cementitious material crystals, resulting in a more regular and denser crystal structure. After grouting, the anchoring force of the coal mass increased from 93.5 kN to 213 kN. Following grouting, the strength of the roadway improved from 26.4 MPa to 33.5 MPa. Additionally, the roadway deformation decreased from 1300 mm to 200 mm. Meso-mechanical and macro-mechanical experiments validate the significant enhancement of the interface strength and mechanical strength of fractured coal through grouting modification. Underground tests demonstrate that grouting modification significantly improves the anchoring performance of bolts in coal, while also enhancing the strength of the roadway roof strata and the coal walls, providing an effective method for reinforcing soft and fractured surrounding roadways.

Highwall mining is one of the effective approaches for the safe and efficient recovery of coal resources trapped beneath highwalls in open-pit coal mines. In essence, it represents a boundary-dominated load-bearing problem primarily governed by slope geometry gradients and free-face effects. Existing coal pillar design methods based on tributary area theory or strength safety factors have difficulty in capturing the coupled response and abrupt instability mechanisms of the roof–coal pillar system. To address these limitations, a mechanical model of the roof-pillars system for highwall mining is established based on elastic foundation beam theory, incorporating slope-induced gradient loading. On the basis of characterizing the post-peak stiffness degradation behavior of coal pillars, a local mine stiffness analysis framework is introduced, and a dual-criterion stability criterion integrating both strength capacity and system constraint characteristics is proposed. A three-dimensional numerical model considering slope geometry and the layout of multiple entries is developed using FLAC3D to systematically investigate the characteristics of the initial stress field in highwall support pillars and the spatiotemporal evolution of stresses during excavation. The spatial heterogeneity of the load-bearing behavior of the roof-pillars system along the entry depth direction is revealed. Furthermore, by integrating the strength-stiffness dual-criterion stability framework with load-bearing control mechanisms, a method for identifying critical zones in highwall mining is proposed. Taking the highwall mining project at the Antaibao open-pit coal mine in Pingshuo as the engineering background, theoretical analysis and numerical simulation are employed to effectively identify critical zones within the mining panel, based on which a preliminary coal pillar design scheme is determined. To address the challenge that personnel cannot access the entries after highwall mining, resulting in uncertainty regarding post-mining entry stability, a tracked robotic platform equipped with three-dimensional laser scanning and ultrasonic ranging sensors is deployed to measure the deformation of surrounding rock within the entries. The results indicate that the initial loads acting on highwall coal pillars under slope topographic control do not increase monotonically with slope height; instead, a transitional zone characterized by stress unloading followed by reloading exists in the lower portion of the slope. After mining is completed, the stress distribution of coal pillars along the entry depth exhibits a “decrease, increase, decrease” pattern, with the stress level and increment of central pillars exceeding those of boundary-adjacent pillars. Comparison between tributary area theory estimates and numerical simulation results shows that the tributary area method underestimates stresses in shallow-depth pillars while overestimating stresses in deep-depth pillars. Significant differences are observed in the load-bearing behavior of the roof-pillars system along the entry depth under varying boundary and loading control conditions. Based on dominant effect differences and stress response characteristics, the system is divided into a topographic effect-dominated zone, a slope gradient effect-dominated zone, and a three-dimensional spatial effect-dominated zone. Engineering case analysis demonstrates that the entry vicinity in the central part of the mining panel constitutes a stiffness-controlled critical zone, whereas the area near the vertical line of slope crest line at greater entry depths in the central panel represents a strength-controlled critical zone. Accordingly, coal pillar design dimensions in highwall mining should prioritize controlling both the strength and stiffness of these critical zones. Based on the preliminary coal pillar design scheme, in-situ testing conducted using the tracked robotic monitoring system confirms that the surrounding rock load-bearing system within the study area remains stable. Neither localized damage associated with abrupt instability in stiffness-controlled critical zones nor large deformations indicative of insufficient load-bearing reserve in strength-controlled critical zones are observed. These results verify that the coal pillar design method based on the strength-stiffness dual-criterion and critical zone control framework can effectively ensure the stability of surrounding rock in highwall entries and satisfy the requirements for safe highwall mining operations.

Abstract Rock elasticity varies with both humidity and water saturation, yet their combined effects remain poorly understood, although in nature vapor adsorption and liquid infiltration occur simultaneously. Here, we present experimental data of P‐wave velocity and volume expansion in a free‐standing sandstone subject to progressive wetting. Elastic softening, evidenced by P‐wave velocity reduction, precedes the wetting front, followed by stiffening as liquid infiltration reverses this trend. To reconcile these softening/stiffening behaviors, vapor migration ahead of the wetting front is captured by numerical simulation of moisture transport constrained by experimental data. Initial softening is explained by a micromechanical model governed by surface energy reduction at grain contacts and validated by independent vapor adsorption tests. Subsequent stiffening is attributed to water infiltration, consistent with patchy saturation theory. We propose softening and stiffening are transitional processes governed by the advancing wetting front, with implications for seismic imaging of progressive wetting processes in crustal rocks.

Targeting strong ground pressure disasters induced by intense mining activities and hard-thick roof strata in the Inner Mongolia-Shaanxi mining area, this study proposes technical countermeasures for ground pressure control through underground regional fracturing in hard-thick roof strata. Integrated methodologies including theoretical analysis, physical modeling, and field trials were employed to investigate key fracturing technologies. The pressure relief mechanism of hydraulic fracturing for hard-thick roof strata, centered on strata structure control, was elucidated. A comprehensive technical workflow for regional fracturing was proposed, including: determination of the target fracturing horizon, design of the fracture network and optimization of key construction parameters, drilling of underground directional long boreholes, multi-stage fracturing within these boreholes, and monitoring and evaluation of the hydraulic fracturing effects. Moreover, an integrated technological system and associated equipment for underground regional fracturing of hard-thick roof strata in coal mines were developed and demonstrated for pressure relief in a super-large mining height panel. The results indicate that during the trial period, a total of 174 microseismic events related to roof breakage were recorded. Among these, 141 events (81.03% of the total) were of the 102 J energy level, with a total roof breakage energy of 7.39×104 J. No major microseismic events with energy levels exceeding 104 J occurred. The weighted average periodic weighting interval was 17.9 m, the average duration span of weightings was 10.7 m, the average leg closure was 375 mm, and the average dynamic load factor was 1.46. Field implementation demonstrates that regional hydraulic fracturing can promote the timely caving of hard-thick roof strata, reduce the periodic weighting interval, and effectively mitigate the intensity of ground pressure manifestations, thereby ensuring the safe and efficient extraction of the super-large mining height panel. The results validate the effectiveness and applicability of the regional fracturing countermeasure for controlling powerful ground pressure in thick-hard roof strata. This research can provide a valuable reference for preventing and controlling powerful ground pressure hazards associated with hard-thick roof strata in the Inner Mongolia-Shaanxi mining area.

Understanding how water influences slow fracture growth in rocks remains a major gap in our ability to predict time-dependent failure. In particular, it is still unclear how moisture-related weakening push a subcritically stressed rock from stable deformation into sudden collapse.In this study, we investigate how hygroscopic weakening—caused by liquid water entering a notch—affects the creep behavior of a clastic rock loaded below its short-term strength. Using a sandstone beam (400 mm×90 mm×90 mm) in an inverted three-point bending setup, we first load the sample to about 67% of its failure strength more than 5 days, then introduce a controlled water drip directly into the notch.We track the fracture response using digital image correlation, ultrasonic transmission, acoustic emission, and crack-opening measurements. The results show two distinct stages after water arrives:a rapid increase in crack opening and loss of stiffness, consistent with moisture-driven softening; anda slower but sustained rise in microcracking activity, leading to accelerated creep and, in some cases, catastrophic failure.In contrast, identical dry beams remain stable over several days, confirming that water—not load alone—initiates the transition to instability.These findings demonstrate that even small amounts of liquid water can sharply alter the long-term mechanical stability of brittle stressed rocks. This work highlights a potential pathway through which more frequent or intense wetting events could increase the likelihood of sudden rock failure in natural and engineered settings.

Coal bursts pose significant safety and operational challenges in deep mining environments, necessitating effective mitigation strategies to address high-stress concentrations and dynamic failure risks. This study evaluated the efficacy of hydraulic fracturing as a preconditioning tool at a longwall face of the Mengcun coal mine with strong coal bursts, Shaanxi Province. The program involved the systematic creation of a fracture network through high-pressure fluid injection, monitored via microseismic arrays, stress measurements, and hydrological sensors. Results demonstrated that hydraulic fracturing effectively redistributed in-situ stresses, reducing high-stress concentrations by up to 30%, lowering the frequency of high-energy microseismic events, and enhancing the stability of fractured zones. However, the presence of unfractured blind spots and interactions with pre-existing faults highlighted the need for optimized well placement and adaptive fracturing designs. These findings underscore the potential of hydraulic fracturing as a critical preconditioning tool in high-stress mining operations, which could provide a framework for improving safety and efficiency in similar geological and operational settings.

Rock elasticity varies with both mechanical loading and moisture content. Studies to date have only examined each effect independently, although moisture interactions with pore walls are likely coupled to mechanical stress. Here, we present experimental data specifically collected in sandstone and granite under simultaneous control of cyclic loading alongside ambient humidity approaching saturated vapor. Adsorption can account for 40% reduction in Young's modulus, which reduces to 10% as uniaxial stress increases from below 1 MPa to below the elastic limit. The observation is explained by a micromechanical model linking grain-scale contact stiffness to pore-scale vapor adsorption, quantitatively capturing coupled stress-induced stiffening and adsorption-induced softening. The coupled behavior is interpreted as adsorption-induced softening becoming inhibited under greater mechanical loads. Our results suggest the coupled effects are strongest at overburden stresses between 3.3 and 10.6 MPa (140-450 m) in sandstone and 6-30.3 MPa (235-1,200 m) in granite.

Fault-slip induced rockburst poses a significant threat to safe and efficient mining of deep coal resources. Investigating the control factors and underlying mechanisms of such events is crucial for disaster prevention and control. This study utilizes a self-developed experimental system designed for simulating fault-slip induced rockbursts in coal mine roadways. A novel low-strength and high-brittleness similitude material was developed, and a corresponding physical model was constructed. A specialized fault-loading scheme was proposed, successfully replicating the full evolution of fault-slip induced roadway rockburst. Complementary numerical simulations were conducted to further elucidate the underlying mechanisms. Key findings include: ① The developed similitude material, primarily bonded with sodium silicate, exhibits an average uniaxial compressive strength of 7.40 MPa, cohesion of 3.35 MPa, a rockburst energy index of 18, and an elastic energy index of 9.2. Under uniaxial loading, the material exhibits dynamic failure modes such as projectile ejection and fragment spalling, effectively simulating fault-slip induced roadway rockbursts. ② A two-stage loading scheme—“critical loading of the roadway followed by activation loading of the fault”—was implemented to simulate the entire process of roadway rockbursts induced by fault slip. The fault-slip process exhibits prominent stick-slip characteristics, resulting in intermittent and extremely brief rockburst events. Fine particle ejection from roadway sidewalls is identified as a significant precursor to dynamic failure. ③ The complete mechanism of fault-slip induced rockburst involves the progressive failure of fault-locking structures during shear, which generates seismic waves. These waves propagate with attenuation into the surrounding rock, triggering the release of accumulated strain energy and inducing dynamic failure. ④ Seismic waves generated by fault slip act as the immediate trigger of the rockburst. The main energy source originates from the strain energy stored in the surrounding rock, of which 30% is transformed into sliding friction energy (facilitating crack propagation and rock fragmentation), and 5.6% into kinetic energy (causing projectile ejection of fractured blocks).

Aiming at the problems of super-large mining space, strong ore pressure and ultra-high coal wall stability control faced by full-mechanized mining face with ultra-large mining height and thick hard roof, this paper takes the 122104 working face of Caojiatan Coal Mine, the world’s first ultra-10 m super-mechanized mining face, as the research background. Systematic research on pressure relief mechanism of heavy hard roof fracturing, true triaxial hydraulic fracturing fracture reconstruction experiment, three-dimensional fracture propagation fluid-structure coupling numerical simulation, high-flow composite fracturing technology and process, hydraulic fracturing effect monitoring and evaluation are carried out. The results show that the pressure relief mechanism of hydraulic fracturing of thick hard roof is mainly embodied in structural regulation, stress transfer, energy release, strength deterioration and so on. Compared with Zhiluo formation, Yan’an Formation has a higher content of brittle minerals and is easy to form complex fracture network. The average fracture radius increases from 21.9 m to 32.5 m with the displacement increasing from 1 m3/min to 5 m3/min, an increase of about 48.40%. The larger the displacement, the larger the hydraulic fracture scale. The hydraulic fracturing pressure relief technology and high-flow fracturing equipment for thick hard roof have been developed. The composite fracturing technology of abrasive jet pre-cut slit and 5 m3/min large flow rate was developed, and a “one game, one policy” zoning design concept of directional hydraulic fracturing for long horizontal drilling was proposed. A set of directional hydraulic fracturing methods for long horizontal drilling with dynamic update of fracturing zones and fracturing plans was formed, and engineering application tests were carried out in Caojiatan Coal Mine. It has realized scientific and effective prevention and control of ore pressure in 10 m super-high working face. The surface microseismic real-time monitoring technology captures the spread track of the fracture network in real time, effectively guides the adjustment of hydraulic fracturing scheme, and obtains the spatial distribution characteristics of roof hydraulic fractures. The multi-factor comprehensive evaluation of hydraulic fracturing effect is carried out, and the working resistance of hydraulic support, the pressing step distance and continuous distance of working face cycle, the dynamic load coefficient, microseismic events and energy are comprehensively analyzed to evaluate the hydraulic fracturing effect. The underground test results show that the underground hydraulic cracks in Caojiatan Coal mine are mainly horizontal cracks, and the average spreading distance along both sides of the borehole is about 80 m, which effectively weakens the overlying thick and complete roof within the working face, and realizes the effective control of regional roof structure. By using zone fracturing technology, the thick hard rock group is pre-fractured in advance, reducing the pressure step and dynamic load coefficient, and ensuring the safe and efficient production of 10 m super-high mining face.

Fully mechanized mining technology with extra-large shearing height is the optimal technical approach to achieve high-yield,high-efficiency and high-recovery mining for 6-10 m ultra-thick coal seam in Chinese coal mines.Based on the analysis of the current status of fully mechanized mining technology and equipment with extra-large shear-ing height at home,focusing on the geological condition of fully mechanized working face with ultra-large shearing height of 10 m in extra-thick coal seam in the Caojiatan Coal Mine,Shaanxi Coal and Chemical Industry Group Co.,Ltd.,the ex-isting technical problems were analyzed and the associated solutions were given from three aspects:surrounding rock con-trol,key mining equipment and intelligent collaborative control.After nearly five years of scientific research,a series of innovative achievements have been achieved:① The surrounding rock control strategy with coordination of support and destressing for ultra-large shearing height working faces,namely"active strong support and protection+regional hydraul-ic fracturing weakening and stress relief',was proposed,a complete set of underground hydraulic fracturing technology and equipment with large flow of 5 m3/min was developed.Effective prevention and control of strong mining-induced activities in ultra-large shearing height working face has been realized.② The strong hydraulic shields with ultra-large shearing height of 10 m were developed,and the"double-layer telescopic beam+three-level side guard"mechanism was innovatively designed to achieve safe protection of working face roof and ultra-high coal wall;the zoned lubrication and distributed cooling scheme improves the cutting reliability of the shearer with large angle of elevation and long rocker;the high-reliability middle trough,lower chain catenary and slow-changing power start-up improve the adaptability of the ultra-large capacity scraper conveyor to the coal flow transportation of the working face with ultra-large shearing height.The systematic integration has formed the global first set of comprehensive mining equipment with extra-large shearing height of 10 m.③ An innovative intelligent control strategy for the operation status of the hydraulic shields with 10 m ultra-large shearing height,and the automatic control strategy for the shearer were proposed.A coordinated control system for the shearer with ultra-large shearing height and the scraper conveyor was constructed by applying the rough neural network technology.An intelligent control mode and control logic for heavy equipment groups with ultra-large shearing height were formed.④ A multi-field and multi-parameter collaborative monitoring and integrated analysis system for the work-ing face with ultra-large shearing height based on"microseism-rock movement-stress-hydrology"was constructed,realiz-ing the multivariate heterogeneous data integrated analysis among damage of overburden rock above working face,sur-face movement and deformation,groundwater flow field and mining-induced activities.The research results were success-fully applied in the in Caojiatan Coal Mine,achieving high-yield,high-efficiency and high-recovery mining in 10 m ultra-thick coal seam,getting significant economic benefits,and leading the development direction of high-efficiency and intel-ligent mining for extra-thick coal seam at home and abroad.

Joint development in rock masses results in complicated anchoring mechanisms of fully grouted bolts. This study offers a detailed analysis of the elastic-plastic deformation evolution of the bolts. A method was developed, taking the deflecting section as a hyperstatic structure with ends rotation, to predict bolt contribution and describe bolt shear behavior by incorporating beam bending theory and the coupling effect of external loads. Assuming elastic-perfectly plastic behavior in steel, the failure process of the bolts was described. As joint shear displacement increases, the bolts initially reach their elastic limit at the zero-shear force point, forming a plastic hinge under combined tension and bending. The plastic deformation zone then expands, leading to full yielding at the bolt-joint intersection under combined tension and shear, and the instability of the hyperstatic structure. Comparative analysis with other models and experimental data reveals accuracy improvements in bolt contribution by 2.0%-11.87% with corresponding end rotational angles from 0.090 degrees to 4.701 degrees, and the length of the deflecting section obtained with the developed method is closer to the test results than other predictions.

A better understanding of the mechanical behavior and failure characteristics of fully grouted bolts under tension is of great significance to ensure the safe production of coal mines. For this purpose, a pull-out experiment of anchorage specimens was conducted and a numerical simulation was conducted based on the experimental results. The experimental and numerical results were analyzed in detail to study the bearing characteristics of fully grouted bolts. The results indicated the following: (1) The bearing characteristics of the anchorage interface could be divided into four stages. The local strain of the anchorage interface was positively correlated with the change trend of the pull-out load. (2) The acoustic emission (AE) activity showed a tendency to first increase and then decrease during the pull-out process. The cumulative AE energy was the largest in the microcrack development stage, while the cumulative AE counts and AE hits were the largest in the shear failure stage. The AE peak frequency presented obvious divisional centralized distribution characteristics, and the AE amplitudes were mainly in the range of 50-80 dB. The cumulative AE events were positively correlated with the damage degree of the anchorage interface and the duration of AE events increased significantly during the microcrack development stage. (3) There are four main stages in the pull-out bearing process of fully grouted bolts. The failure process of the fully grouted bolts was progressive. The increase of the bonding length not only increased the non-uniformity of the shear stress of the anchorage interface, but it also affected the characteristics of the pull-out load-displacement characteristics. With the increase of the bonding length, the peak pull-out load first increased rapidly and then increased at a relatively low but steady rate. The research results may provide guidance for the support design of fully grouted bolts.

As coal mining depth increases, the combined effects of high stress, mining stress, and fault structures make dynamic impact hazards more frequent. The reproduction of dynamic impact phenomena is basis for studying their occurrence patterns and control mechanisms. Physical simulation test represents an efficacious methodology. However, there is currently a lack of simulation devices that can effectively simulate two types of dynamic impact phenomena, including high stress and fault slip dynamic impact. To solve aforementioned issues, the physical simulation test system for dynamic impact in deep roadways developed by authors is employed to carry out comparative tests of high stress and fault slip dynamic impact. The phenomena of high stress and fault slip dynamic impact are reproduced successfully. A comparative analysis is conducted on dynamic phenomena, stress evolution, roadway deformation, and support force. The high stress dynamic impact roadway instability mode, which is characterized by the release of high energy accompanied by symmetric damage, and the fault slip dynamic impact roadway instability mode, which is characterized by the propagation of unilateral stress waves accompanied by asymmetric damage, are clarified. On the basis, the differentiated control concepts for different types of dynamic impact in deep roadways are proposed.

As a fundamental energy resource in China, coal plays a pivotal role in the national economy. The development of the coal industry, an integral part of China's energy sector, is closely tied to advancements in coal science and technology. This paper comprehensively summarizes the progress and major research achievements in coal mining science and technology in China, covering geological prospecting, open-pit mining, underground mining, and safety technologies. In the area of geological prospecting, the paper elaborates on advanced coal exploration technologies that enable high-precision, small-scale, and large-range real-time detection of hidden geological hazards in coal mines. For open-pit mining, the progress in intelligent mining technologies and ecological protection methods is introduced, achieving the coordinated development of safe, efficient production and environmental protection. In underground mining, world-class shaft construction technologies, including drilling, freezing, and grouting, are discussed, ensuring stability and safety in shaft operations. Considering the complex geological conditions of coal seams in China, advanced technologies and equipment for rapid roadway excavation and support under various conditions are outlined, highlighting rapid excavation systems featuring integrated spray and drill-anchor support, which significantly enhance support efficiency. Additionally, the paper systematically reviews the latest advancements in fully mechanized mining technologies and equipment for single-pass full-height extraction, top-coal caving for thick coal seams, intelligent coal mining technologies, and disaster prevention and control methods. Years of research and practice have demonstrated that China has developed a coal miming science and technology system with unique characteristics, providing reliable technical support for safe and efficient coal mining. Finally, the paper proposes future development directions for safe, green, and intelligent coal mining technologies under deep and complex conditions in China.

A complex geological environment with faults can be encountered in the process of coal mining. Fault activation can cause instantaneous structure slipping, releasing a significant amount of elastic strain energy during underground coal mining. This would trigger strong rockburst disasters. To understand the occurrence of fault-slip induced rockbursts, we developed a physical model test system for fault-slip induced rockbursts in coal mine drifts. The boundary energy storage (BES) loading apparatus and bottom rapid retraction (BRR) apparatus are designed to realize energy compensation and continuous boundary stress transfer of the surrounding rocks for instantaneous fault slip, as well as to provide space for the potential fault slip. Taking the typical fault-slip induced rockburst in the Xinjulong Coal Mine, China, as the background, we conducted a model test using the test system. The deformation and stress in the rock surrounding the drift and the support unit force during fault slip are analyzed. The deformation and failure characteristics and dynamic responses of drifts under fault-slip induced rockbursts are obtained. The test results illustrate the rationality and effectiveness of the test system. Finally, corresponding recommendations and prospects are proposed based on our findings.

Rock support is a complex challenge in coal mine heading operations. In particular, heading faces with moderately stable surrounding rock are constrained by unsupported roof /sidewall distance and duration. The ability to provide rapid and effective support directly impacts surrounding rock stability and heading efficiency. This study focused on the anchoring mechanism in rapid heading faces in a specific entry of the No. 2 Coal Mine of Huangling Mine, characterized by moderately stable surrounding rock. The geological conditions, heading status, and factors limiting rapid heading were analyzed. A novel partitioned parallel anchoring (PPA) model was proposed, and its mechanism and impact on the surrounding rock stability were investigated. The findings show that the surrounding rock is significantly affected by heading disturbances; however, a reasonably implemented effective PPA strategy can control surrounding rock deformation. Spatially, anchoring operations are categorized into local anchoring and reinforcement anchoring. Temporally, cutting, local anchoring, and reinforcement anchoring are performed simultaneously, effectively reducing the cycle time and enhancing the overall heading speed. Combining these findings with the actual geological conditions, a specific scheme of PPA was proposed, and the optimization of the rapid heading and PPA processes, along with the effectiveness of PPA, were validated through field experiments. Finally, recommendations for effective PPA in rapid heading faces were provided, offering valuable insights into efficient rock anchoring and rapid heading under similar geological conditions.

The 10 m ultra-large mining height of Caojiatan Coal Mine is a world's first in terms of single mining height and mining intensity,and the effective control of surrounding rock in the stope is crucial for safe and efficient mining at the working face.Based on the analysis of the coal seam occurrence conditions and the characteristics of the ground pres-sure behavior of the already mined faces,and considering the ultra-large mining space and the ultra-high coal wall charac-teristics of the working face,the difficulties in controlling the surrounding rock of ultra-large mining height were clarified.A"superimposed arch-beam"structural model for the ultra-large mining height stope was established,and a three-in-one surrounding rock control strategy of"active support protection+regional pressure relief weakening+comprehensive monitoring and early warning"was proposed,verifying the effectiveness of the surrounding rock control for the 10 m ultra-large mining height.The research shows that:the occurrence characteristics of multi-layer thick and hard roofs cause ab-normally strong mine pressure manifestation at the working face,with large-area hanging roofs during initial mining and significant strong dynamic loading pressure at the working face during normal mining.The keys to controlling the sur-rounding rock in the 10 m ultra-large mining height stope are reducing the pressure step distance,weakening the dynamic loading pressure,preventing rib spalling,and preventing the working face from being crushed by the pressure.The"double-layer telescopic beams+three-stage rib protection"structure of the hydraulic support achieves independent opera-tion for the protection of the empty roof in front of the support and the ultra-high coal wall,solving the problem of incom-plete rib protection by the original split-type rib protection.The high initial setting force and high working resistance of the hydraulic support significantly reduce the risk of rib spalling and roof caving at the working face and effectively control the roof subsidence during the pressure period.The underground deep-hole 5.0 m3/min high-flow directional fracturing weakening technology achieves weakening of the multi-layer thick and hard roofs,effectively reducing the intensity of mine pressure at the working face,controlling the amount of rib spalling and significant roof subsidence during the pres-sure period,and preventing the working face from being crushed by the pressure.Comprehensive monitoring and early warning effectively ensures the support efficiency of the support during mining,realizing real-time tracking of roof frac-ture and real-time analysis of strong mine pressure.The problems of large-area hanging roofs and small hurricanes during the initial mining of the ultra-large mining height working face have been resolved.The initial pressure step distance is 49.35 m,the pressure duration distance is 5.75 m,and the opening ratio of the safety valve of the support column is 24.81％.The manifestation of mine pressure during the periodic pressure period has been significantly alleviated.The av-erage shrinkage of the hydraulic support column has decreased from 0.48 m to 0.32 m,a decrease of 33.3％,and the max-imum shrinkage has decreased from 1.88 m to 1.44 m,a decrease of 23.4％.The proportion of the average dynamic load coefficient of the working face periodic pressure greater than 1.5 has decreased from 39.6％to 14％.During normal pro-duction at the working face,rib spalling is within a controllable range,with the amount of rib spalling concentrated at 0.2-0.5 m.The research results have important guiding significance for the control of surrounding rock in ultra-large min-ing height mining.

Firmly, the bearing capacity test of 1:1 equal ratio pillar under different constraint forms and different filling medium conditions was carried out. The results show that the binding pillar-forming effect is relatively good. The constraint ability of unconstrained, metal mesh, polyester mesh, hooked iron flat-hoop bushing, bellows, and spiral iron pipe is enhanced, in turn, and the carrying capacity is improved successfully. The homogeneity of high-water materials is better than concrete, and they have better compressibility, but their carrying capacity is relatively weak. The carrying capacity of concrete pillars is generously higher than that of high-water materials, but the compressibility is poor. Second, the migration characteristics of the surrounding rock structure of the gob-side entry retaining and the rule of side support are analyzed, the requirements of the side support are pointed out, and the side-support technology of the binding pillar is proposed. Taking Hijiata Mine’s 50108 working face gob-side entry retaining as an example, the bellows pump-filled concrete pillar is used as the side support body, supplemented by handling steel mesh and air-duct cloth, and toughness material is sprayed between the pillars to seal the goaf, meeting the requirements of side support and road stability. The pillar has the characteristics of high early strength, strong final consolidation carrying capacity, good crimping effect, high mechanism degree, fast construction speed, less concrete consumption, low comprehensive cost, etc., and it has a good application prospect in the gob-side entry retaining or rapid advanced working face.

This paper analyzes the current situation and existing problems of coal roadway driving technologies and equip-ment,introduces the new mode,technology,equipment of coal roadway rapid driving with integrated drilling and anchor-ing and its underground applications.The bolting technologies and equipment with integrated drilling and anchoring are developed which include the integrated drilling and anchoring bolt,pumpable resin,drilling boom and drill rig as well as bolts cartridge with integrated drilling and anchoring,pump unit and intelligence control system.The new technology sim-plifies the traditional six-step rock bolting process to one continuous step.Rock bolting can be realized automatically by pressing button once and the operation time for installing a single bolt can be reduced from 5 to 6 minutes to 3 minutes.The technologies and equipment of automatic spraying support are developed which include high-strength,rapid setting,and deformable surface supporting spraying materials with a tensile strength exceeding 9 MPa,elongation at break exceed-ing 100%,and a bonding strength exceeding 3 MPa.The spraying system with 6-degree-of-freedom manipulator is de-veloped which can automatically and rapidly spray during roadway driving.The dynamic monitoring technology and sys-tem for roadway surrounding rock deformation are developed during driving which can achieve a surface deformation monitoring of roadway in environments with dust,multiple interference,and low illumination.The monitoring accuracy can meet the requirements of the surrounding rock stability evaluation.A new partitioned parallel collaborative rapid driv-ing mode of excavation,spraying,bolting and transport is proposed and a complete set of roadway rapid driving equip-ment with integrated drilling and anchoring is developed.The displacement and stability of the surrounding rock during the driving process at the Caojiatan Coal Mine in Shaanxi Province are monitored.In terms of time,more than 80%of the surrounding rock displacement had already occurred in 2 to 3 hours after the excavation of the roadway.In terms of space,more than 90%of the surrounding rock displacement had already occurred at a distance equivalent to twice the width of the roadway from the excavation face.Therefore,the roadway surrounding rock displacement caused by rapid driving can be completed in a short time,requiring timely and rapid support.The nearly 6 000 m roadway driving project has been completed in the 10-metre-extra-high fully mechanized mining face of the Caojiatan Coal Mine,and over 60 000 bolts with integrated drilling and anchoring are installed.The time for installing a single bolt,the number of supporting workers,and the labor intensity of workers have been significantly reduced.The driving speed,efficiency,and automation level have been significantly improved.The displacement of the experimental roadway roof is small.The roadway surrounding rock stability is good as well as the support effect.The coal roadway rapid driving technology and equipment with integ-rated drilling and anchoring have achieved a success in underground field test.It has the ability to achieve a monthly driv-ing footage of 1500 to 2000 m for ultra-large cross-section coal roadways.