To investigate the dominant factors and instability mechanism of surrounding rock deformation in cross-mining roadways, a systematic study was conducted using theoretical analysis, numerical simulation, and response surface methodology to examine the influence of various factors on surrounding rock stability. First, the theoretical model was refined by introducing a lithology coefficient of the load-transfer layer, thereby improving its engineering applicability. Subsequently, numerical simulations and response surface experiments were employed to analyze the effects of key factors, including the vertical distance between the working face and the roadway, the horizontal distance between the working face and the roadway, the burial depth of the roadway, the mining height of the working face, and the lithology of the load-transfer layer. The analysis results indicate that the vertical distance, horizontal distance, and lithology of the load-transfer layer are negatively correlated with roadway roof displacement, whereas the burial depth and mining height are positively correlated. The p-values for all factors were less than 0.0001. The order of significance of the influencing factors is as follows: vertical distance > horizontal distance > burial depth > mining height > lithology of the load-transfer layer. Among these, the vertical distance has the most significant effect on roadway deformation and exhibits notable interaction effects with burial depth and horizontal distance. Based on these findings, given that construction conditions cannot be altered, modifying the lithology of the load-transfer layer was selected as the control measure. Directional long-hole hydraulic fracturing for roof cutting and pressure relief was implemented in the roof of the return airway in the No. 6 mining district. Field monitoring results show that hydraulic fracturing effectively interrupted the stress transmission path induced by mining activities, transferring roof pressure to deeper strata. Consequently, the deformation of the surrounding rock was significantly reduced, the dynamic pressure effect was markedly alleviated, and the stability of the roadway was effectively controlled. The research results provide a theoretical basis for the design and control of cross-mining roadways under similar engineering conditions.

Accurate ore identification is a prerequisite for automated crushing by robotic arms. However, the complex underground mining environment, along with the inherent characteristics of ore such as complex shapes, subtle textures, and blurred boundaries, severely restricts ore identification performance. To address these issues, this paper proposes an improved instance segmentation model, GLD-YOLO, based on the YOLO11-seg network. First, considering the feature aliasing problem in underground ore segmentation, a collaborative enhancement mechanism of C3k2_GBC and C2PSA_LRSA is introduced. By adopting novel gated convolution and local self-attention, the edge and detail features of the target are effectively enhanced, strengthening the saliency of the ore’s effective features. Second, addressing the limitation that deep networks easily lose subtle edge information, a PAFPN_DDFE neck network is constructed. Through the novel DDFE module, shallow features are effectively utilized, and the advantages of spatial and frequency domain information are integrated to achieve noise filtering and edge information enhancement. Then, to further refine the boundaries, the gradient update path is optimized using the Focaler-Shape-IoU loss function, guiding the network to focus on difficult samples and improving the regression accuracy of the ore bounding boxes. Finally, comparative experiments and analyses were conducted between the proposed improved method and the benchmark algorithm by building an ore crushing simulation experimental platform. The results show that the proposed method improves the mAP50 and mAP50-95 metrics by 4.4% and 5.1%, respectively, compared to the benchmark model, and the model detection speed reaches 90 FPS. On the MineralImage5k and Crack-seg datasets, the mAP50 is improved by 1.9% and 2.1%, respectively, verifying the feasibility and generalization of the recognition model.

Accurate recognition of coal-rock properties (CRPs) while drilling is a critical prerequisite for ensuring the intelligent control and stable operation of antipunching drilling robot. The primary challenges in industrial applications are potential safety hazards and single drilling mode in coal mine roadways, resulting in samples with insufficient number, unbalanced distribution, and background interference. However, most current CRPs recognition methods rely on sufficient and balanced samples, limiting their application efficiency and scope. To this end, we propose a selective kernel transformer with model-data fusion loss (SKformer-MFL) model with data correction, which generates simulated signals via electromagnetic simulation model to assist the CRPs recognition while drilling under limited samples. First, a coal-rock drilling model based on electromagnetic simulation is established to generate simulated signals as the primary part of training samples. Then, the simulated signals are corrected using denoising diffusion probabilistic model improved with vector-quantized variational autoencoder to minimize the feature discrepancies between simulated and real signals. Finally, the corrected high-fidelity signals are used to train the proposed SKformer-MFL model, where a novel loss is built to handle the imbalanced training dataset through an adaptive weighting mechanism. This model can simultaneously capture long-range correlated features and local mutation multiscale features of the input signals, thereby improving the model’s recognition capability and generalization performance. The experimental results indicate that the proposed method can produce high-fidelity electromagnetic simulation signals and achieve excellent recognition performance for CRPs while drilling under limited samples.

Beishan granite should serve as host rock for a high-level radioactive waste (HLW) repository in China. The host rock of an HLW repository will be subjected to high crustal stress, elevated temperatures, and significant pore and joint pressure, respectively. This study documents thermo-hydro-mechanical (THM) coupled tests on Beishan granite and provides its properties under these complex conditions. The results indicate that increase in temperature or fluid pressure leads to a strength reduction. However, the extent of strength reduction due to increasing temperature varies with different fluid pressures. Additionally, the mean values of Young’s modulus and Poisson’s ratio exhibit an initial increase followed by a subsequent decrease as temperature rises up to 90 °C. Throughout the damage process, it was observed that the amplitudes of acoustic emissions (AE) increase approximately proportional to the decrease in number of AE events. The released AE energy within the amplitude ranges of (45, 50], (50, 55], and (> 60) constitutes the primary contributor to the damage observed in the specimens. To characterize the permeability evolution throughout the entire deformation process of the specimen, a linear exponential relationship between permeability and volumetric strain is established.

The stability of the hole-bolt composite structure (HBCS) is crucial for controlling the surrounding rock in engineering. Based on the experimental results, the discrete element analysis was employed to investigate the fracture properties and collaborative mechanism of HBCS. Initially, the theoretical analysis indicates that the stress within the surrounding rock around the pressure relief hole is influenced by the rock mass’s properties and the spatial distance. The mechanical response observed in the models is consistent with the results from physical tests. Observations of fracture suggest that a higher bolt pre-tightening force promotes the coalescence of tensile cracks between the hole and bolt. In contrast, increased hole-bolt spacing leads to more discontinuous cracks. Data monitored using measuring balls show that the stress around the pressure relief hole initially increases as hole-bolt spacing rises, while it will diminish on the upper and horizontal sides of the hole. Furthermore, stress nephograms illustrate a proportional relationship between the stress around the bolt and the bolt pre-tightening force, with an expanding low-stress area occurring as hole-bolt spacing increases. The variations in bolt force further corroborate that larger hole-bolt spacing enhances the reinforcement capacity of the bolt. These findings demonstrate that the hole-bolt collaborative mechanism enables the bolt to achieve optimal reinforcement effectiveness, while maximizing the pressure relief capabilities of the pressure relief hole, thereby enhancing the strength and stiffness of the HBCS. This research provides critical insights for controlling the stability control of surrounding rock in high-stress roadways.

The variation in roof structure induced by changes in bedrock thickness exerts a direct influence on the stress distribution within lower strata, consequently governing the stability of roadway surrounding rock. To investigate the impact of bedrock thickness variations on overburden fracture behavior and stress evolution in deep-buried thick loose layers, a numerical simulation model of an unequal-thickness bedrock working face was developed using discrete element numerical simulation software. This model was utilized to conduct a systematic investigation into the fracture characteristics of the overburden, displacement characteristics, and stress evolution during the mining process. The results demonstrate that as the working face advances and bedrock thickness progressively increases, several significant changes occur: the caving interval of the immediate roof extends; the degree of fragmentation, overall separation, and subsidence of the caving rock layer above the goaf gradually diminish; the peak stress at the working face shifts deeper into the coal wall; and the stress influence zone expands. Through the establishment of a mechanical model of the key strata, a fracture formula for the overburden was derived, elucidating the fracture mechanics of bedrock with varying thicknesses. A combined support measure tailored to varying bedrock thicknesses has been developed. Practical applications have demonstrated the technology’s effectiveness in maintaining roadway stability, offering valuable guidance for safe and efficient mining operations under comparable geological conditions.

Fractured rock masses are extremely common in geological engineering. In order to improve the stability of surrounding rock under dynamic conditions, new grouting materials and their reinforcement characteristics were studied. In this paper, split Hopkinson pressure bar (SHPB) tests were employed to analyze the dynamic mechanical and failure characteristics of grouted fractured rock with nano-grouting material (nano-grouted fractured rock). Simultaneously, high-speed camera tests were utilized to examine the macroscopic dynamic deformation and failure processes. The following was found: (1) Under a relatively low impact air pressure of 0.1 MPa, the mechanical properties of nano-grouted fractured rock are considerably better than those of traditional cement-based grouted rock. However, when the impact air pressure is increased to 0.3 MPa, the superiority of nano-grouting material diminishes, the possible cause of which is explained from the microscopic point of view. This means the nano-grouting material is more suitable for low-engineering-disturbance conditions (e.g., shield construction). (2) Both for the nano- and superfine cement grouting material, the impact fractures initially emerge at the two ends of the original grouted fracture and form a pair of parallel lines. (3) In comparison with 0.1 MPa, the impact pressure of 0.3 MPa leads to more severe damage to the rock specimen. These findings contribute to a deeper understanding of the behavior of nano-grouted fractured rock under dynamic loading and provide valuable insights for relevant engineering applications in the field of rock mechanics and grouting technology.

Accurate recognition of coal-gangue is an important prerequisite for ensuring intelligent control and stable operation in top coal caving face. The main challenges in underground application are serious harsh conditions including low light and high dust, which significantly degrade the image quality and complicate the recognition process. Current coal-gangue recognition methods often struggle with noise and lack robustness under these harsh conditions. To this end, this paper proposes a novel visual image-based coal-gangue release status recognition method with Detail-WaveNet and a lightweight YOLOv8n model coal-gangue object detection-YOLO (CG-YOLO) in top coal caving face. First, the image enhancement model Detail-WaveNet is developed, which improves the coal-gangue image clarity by introducing detail enhancement convolutions and a self-modulation feature aggregation module into WaveNet model. Then, a coal-gangue recognition model CG-YOLO is proposed based on the YOLOv8n architecture, which incorporates a high-performance GPU structure (HGNetv2) and a large separable kernel attention mechanism to significantly improve the recognition accuracy of coal-gangue in harsh environments. Finally, some simulations and experiments are carried out, and the results indicate that the proposed method significantly outperform the advanced models, enabling accurate coal-gangue recognition under harsh conditions.

Drilling tools loading and unloading for drilling machine is a labor-intensive task. The automatic loading and unloading function of the drilling machine can prominently lessen the labor intensity borne by workers and serves as a key requisite for the full automation of underground drilling equipment. The drilling tools loading and unloading system (DTLUS) is subject to a relatively large load, leading to fluctuations in the hydraulic system’s pressure and flow rate. In view of this, a robust control strategy based on the sliding mode controller is proposed. Aiming at the requirement of suppressing chattering during the operation of the sliding mode controller (SMC), a fuzzy neural network (FNN) parameter adjustment method based on the variable structure control framework is designed, which is intended to enhance the stability and control accuracy of the system, so as to better cope with the complex working conditions of the DTLUS and ensure its efficient and stable operation. The experimental results indicate that the designed controller can reduce mechanical impact and enhance the efficiency of drilling tools loading and unloading.

The reasonable setting of coal pillar width plays a key role in guaranteeing the steadiness of surrounding rock of fully mechanized caving gateroad driving along the next goaf. Based on the engineering background of the Bayangaole mine, the discrete element method was used to simulate the fracture evolution of coal pillars with different pillar widths. The results show that the damage rate of the coal pillar increases with the decrease in the width of the coal pillar. Once the coal pillar width is smaller than 6 m, cracks run through the coal pillar, and the coal pillar is completely damaged. In the middle of the coal pillar, which has a width of 6 m and above, there is a relatively complete area with low damage. The results show that the pillar width of 6 m is the most appropriate. Field tests prove that the reserved width of a 6 m small coal pillar can effectively control the surrounding rock deformation, ensuring the overall steadiness of the gateroad in the thick coal seam. It is hoped that this study will offer some reference for the determination of the reasonable size of the coal pillar.

Accurately characterizing the mechanical behavior and fracture mechanisms of rock containing holes under dynamic loads is essential for ensuring the stability of underground rock structures. In this study, to enhance the understanding of the fracture processes in rock specimens with cavities subjected to dynamic impacts, experimental and numerical studies focusing on the influence of borehole geometry and strain rate are conducted. The results reveal that the strain rate affects the specimens’ dynamic mechanical strength and peak strain. However, the degree of such influence diminishes as the borehole diameter increases in specimens containing two holes. Fractures that lead to failure are primarily initiated at the axial and radial edges of the holes, the specimen extremities, and around the rock bridges in specimens with dual cavities, indicating significant stress concentration zones within the stress field distribution for specimens with a single hole. Further analysis using displacement field diagrams confirms that shear-induced fractures are the predominant cause of failure across all specimens. These findings provide critical insights for developing borehole pressure relief technology to protect against the risks of deep dynamic impacts.

This study investigates the impact of tailings characteristics, particularly fine tailings, on the efficiency and effectiveness of mining engineering backfill operations. Contrary to the common underestimation, fine tailings significantly affect the mechanical properties and failure mechanisms of Cemented Tailings Backfill (CTB). Through a series of experiments examining various particle size distributions and employing advanced Scanning Electron Microscopy (SEM) and Mercury Intrusion Porosimetry (MIP) techniques, this research clarifies the role of fine tailings in modifying the mechanical strength and failure patterns of CTB. Adding 20 % fine tailings optimally enhances both the early and long-term strength of backfill materials. With aging, adding 30 % fine tailings shows a rapid strength increase from 7d to 28d, with the 28d strength slightly lower than that of specimens with 20 % addition, but the specimens demonstrate better ductility after reaching peak strength. As the content of fine tailings increases, crack propagation in the specimens shifts from radial to axial, simplifying the fracture mode from complex to singular. Consequently, the fracture mechanism changes from ductile to brittle, and then reverts to ductile. Moreover, using particle flow simulation and moment tensor analysis to study the failure processes indicates that while increased fine particle content boosts the material's initial strength, it ultimately leads to a simpler crack network and volumetric expansion as the primary failure mode. In terms of energy conversion mechanisms, as the content of fine particles increases, the energy first increases and then decreases. During the elastic stage and the early stage of the plastic stage, the energy is mainly converted into strain energy and PB bonding energy, which affects the elasticity of the sample. In the later stage of the plastic phase, the energy is mainly converted into dissipated energy, leading to the failure of the sample.

For jointed rock mass with anisotropy and discontinuity, the structure of the surrounding rock is constantly developing and changing during tunnel excavation. It is difficult to reasonably predict localized deformation of jointed rock mass by using the existing rock mechanics theory. In this paper, the failure characteristic of pre-holed jointed rock mass with three joint angles is experimentally investigated by adopting the digital image correlation and acoustic emission methods. To avoid the influence of measurement error on Digital Image Correlation (DIC) from discontinuous deformation, parametric studies and an optimized algorithm are also included in DIC tests. Results indicate that the perpendicular-jointed condition (0° joints) is the most dangerous situation because of its comparatively lower strength and brittle failure mode with a shift energy release. For rocks with different jointed angles, localized deformation emerges after the material enters the plasticity. Significant localization occurs after the failure with cracks surrounding the center hole and pre-existing joints.

To investigate the influence of bolt pre-tightening force and hole-bolt spacing on the mechanical responses and failure characteristics of rock-like materials with hole-bolt composite structures, a comprehensive set of physical tests was carried out. The findings suggest that enhancing the pre-tightening force improves the peak stress and elastic modulus of the material. However, these properties initially increase and then diminish with widening hole-bolt spacing. An increase in pre-tightening force results in more fractures around the hole, altering the material's failure mode from tensile-shear to purely tensile. Additionally, as the hole-bolt spacing expands, the tensile crack positioned above the hole progressively shifts away from the bolt, leading to a transition in failure mode from tensile to tensile-shear. Field tests confirm that the bolt force proximate to the pressure relief hole remains significantly greater than that at a distance, establishing hole-bolt spacing as a critical factor in anchorage stability.

In natural rock mass, the existence of joints or fissures makes the strength of surrounding rock significantly reduced. In this paper, the influence of deformation and failure law of jointed rock mass on the stability of surrounding rock is studied by prefabricating five kinds of single fracture rock samples with different angles. Firstly, the failure and deformation of the unanchored and anchored specimens under different loading conditions (uniaxial compression and cyclic loading) were studied in laboratory tests, respectively. Secondly, the microscopic fracture characteristics and deformation damage modes of the specimens were simulated by using PFC numerical simulation software. The results show that the peak strength and elastic modulus of the sample increase with the increase in the inclination angle. After the sample is anchored, the peak strength of the sample is effectively improved, and the number of cracks is significantly reduced. In practical engineering applications, bolts can change the crack propagation mode and limit the initiation of cracks in the surrounding rock. By studying the crack propagation law and failure characteristics of fractured anchored rock samples, we can deepen the understanding of rock fracture behavior and better reveal the failure and deformation mechanism of surrounding rock instability in tunnel construction.

Nonpersistent joints are prevalent in engineering rock masses and are sensitive to cyclic loads induced by geological movements and engineering disturbances. Therefore, studying the fatigue mechanisms of rock masses with nonpersistent joints under cyclic compressive loads is crucial for ensuring the rational design and long-term stability of rock engineering structures. Based on laboratory experiments, this study employed the discrete element method to create specimens with different nonpersistent joints, and uniaxial compressive cyclic loading tests were conducted on these specimens with different maximum cyclic stress levels. The results show that the joint inclination significantly affects the characteristics of jointed rock, such as deformation modulus, irreversible strain, energy evolution, and crack characteristics. Increasing the maximum stress in the stress path results in a rapid release of hysteretic energy in the jointed regions of the rock, which leads to an exponential decrease in fatigue life while an increase in initial irreversible strain, final irreversible strain, and hysteretic energy density. Additionally, the shear fracture zones on both sides of the model expand, and the propagation and merging of cracks between joints become more extensive and complex. The results are significant for studying rock fatigue instability and structure engineering design.

In tunnel engineering, the rock mass contains a significant number of irregularly distributed joints, and typically exhibits high energy accumulation, thereby posing a risk of rockburst occurrence. Therefore, it is of paramount importance to investigate the fracture propagation behavior in jointed rock masses and assess the impact of borehole pressure relief on mitigating rockburst occurrences for effective prevention and control measures. This paper focuses on failure characteristics and pressure relief effectiveness of non-persistent jointed rock mass with holes through laboratory testing and numerical simulation. In laboratory experiments, rock samples are prepared to include a range of crack dip angles and circular holes. Then, the crack propagation law of crack inclination and circular hole is studied by AE and DIC technology. The experimental results show that with the increase of fracture dip angle, the peak strength and energy change of the sample decrease first and then increase. Due to the existence of holes, the crack propagation direction of the original crack is changed. After drilling, the strain energy of the sample is obviously reduced, which shows that the drilling pressure relief effect is obvious, which can effectively reduce the energy accumulated inside the rock mass and reduce the risk of rockburst. Finally, the PFC numerical simulation software is used to analyze the micro-failure process and energy change law of the sample from three aspects: the relative position of cracks and holes, the diameter of boreholes and the spacing of boreholes. Further understanding of the energy dissipation law and mechanical behavior characteristics of jointed rock mass provides a reference for exploring the pressure relief effect of rock mass and preventing rockburst.

The collapse of overlying rocks caused by the instability of residual coal pillars during lower coal seam mining significantly impacts its safety. This paper focuses on the gentle dipping coal seam group and utilizes the discrete element method (DEM) as the basis to comprehensively consider multiple factors through orthogonal experiments. In so doing it reveals the influence mechanisms of various factors on mining at a close distance under a residual coal pillar. Firstly, the process of lower coal seam mining under residual coal pillars in gently-dipping coal seams was simulated and analyzed based on a case study at the Baoping coal mine. Comparing the evolution characteristics of coal–rock fractures, stress changes, and displacement changes during the mining process reveals the mechanism of the joint instability of the lower coal seam, interlayer rock, coal pillars, and overlying strata under the disturbed conditions of lower panel mining. Secondly, an orthogonal simulation experiment was established using the width of the coal pillar and the thickness of the lower coal seam as variables. By comparing the development process of cracks, stress distribution, and rock displacement under different conditions, the research results indicate that the width of coal pillars has an impact on the maximum amount of coal pillar subsidence, while the thickness of the underlying coal seam has an impact on the time of subsidence, when hd ≥ 4.2 m (hj/hd ≤ 4) and w ≤ 14 m (w/hm ≤ 2), a large-scale collapse of the overlying strata of the coal pillar occurs.

To explore solutions for reinforcement problems of broken rock masses in deep roadways, it is necessary to study the performance of cement-based grout and its reinforcement effect. In this study, grouting-reinforced specimens with different particle sizes of broken coal were made, which revealed the reinforcement effect of grouting on the bearing capacity of broken coal and the mechanism for secondary bearing damage and the instability of the reinforced specimens. First, it was determined that the appropriate water–cement ratio (W/C) to meet the field grouting conditions is 0.45. Second, the uniaxial compression of the grouting-reinforced specimens with 0.45 W/C was carried out, and acoustic emission equipment was used to detect it. Finally, through indoor experiments, this study investigated the differences in failure modes, stress–strain curves, and acoustic emission signal characteristics among intact coal samples, grouting-reinforced bodies with different particle sizes, and grouting-reinforced bodies after anchoring. The deformation and failure patterns of grouting-reinforced bodies were revealed, and the failure mechanisms of grouting-reinforced bodies with different particle sizes were elucidated.

An implicit gradient-enhanced nonlocal meso‑scale damage model is developed to investigate deformation and fracturing of brittle materials. In the model, an implicit gradient integration scheme is adopted to deal with mesh dependency and strain localization. The mechanical parameters are assigned randomly using a Weibull statistical distribution to reflect the material heterogeneity at the meso‑scale. A linear elastic damage constitutive law with residual strength is used to describe the stress-strain relationship at the mesoscale and the Mohr-Coulomb criterion as well as the tensile stress criterion are used to evaluate the damage of the elements in tension or shear. The local equivalent strain is replaced by a nonlocal description employing the non-local implicit gradient model. Benchmark tests are conducted to document the potential of the model in simulating crack initiation and propagation processes in brittle materials. The benchmark tests also demonstrate that the proposed non-local damage model can effectively achieve strain localization and eliminate mesh dependency to some extent.