In deep hard rock mining, high confining pressure inhibits tensile failure, leading to low efficiency and severe tool wear in conventional mechanical rock breaking methods. To solve this problem, we propose a Controllable Free Surface Induced Tensile-Shear Collaborative Fracturing (CFS-TSCF) method. The method pre-forms an engineered controllable free surface (CFS) to reconfigure the local stress field, enabling a specialized device (FIPFD) to apply directional tensile-shear loads for low-energy breaking. A multi-scale approach integrating lab AE tests, DEM simulations, and field verification investigated the fracture mechanism and performance. Results revealed a predominantly tensile-driven (>50%) process. The CFS transforms the rock's triaxial compression into a specific stress path. This path, dominated by directional tension and constrained by lateral compression, guides the fracture along a low-energy channel. This also dictates the micro-mechanism's evolution from central quasi-tensile to peripheral tensile-shear failure. Field trials in hard rock (>200 MPa UCS) validated the method, demonstrating controllable, blocky spalling and achieving an average mining efficiency of 52.03 t/h. This research validates the CFS-TSCF method, offering a new technical paradigm for safe, efficient, continuous hard rock mining.(c) 2026 China University of Mining & Technology. Publishing services by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Microseismic monitoring is widely used to support early warning of engineering rock-mass instability, but a physically developing instability nucleus may not be directly observable under realistic monitoring conditions. This study evaluates instability-nucleation observability using a controlled C2 two-nucleus benchmark and a real observation library containing 28 stations, 6902 events, and 59988 event-station detections. The benchmark defines a true target nucleus and a competing nucleus, while the observation library imposes realistic station geometry and event-dependent detection constraints. A scenario hierarchy separates the imposed truth field, ideal observation, real station geometry, and real event triggering. Observability is assessed using observable onset, detection delay, warning lead time, normalized recovery gap, and false-nucleus dominance. The results show that monitoring realism strongly controls recoverable warning information. Usable ray support remains 56 in the ideal and real-geometry full-detection scenarios, but decreases to 35 when real event-dependent detections are imposed. The observable onset of the true nucleus is delayed from t4 to t5, and the true nucleus is not observed by t7 under the real-detection scenario. Accordingly, detection delay increases from 3 to 4 and then to >6 stage units, while warning lead time decreases from 3 to 2 and then to 0. Under spatial-bias sensitivity, the maximum false-nucleus dominance reaches 0.86. These findings indicate that monitoring-system performance should be evaluated in terms of recoverable warning information, not only event activity or anomaly strength. The framework links monitoring geometry, event triggering, ray support, timing reliability, and target identity into a unified approach for engineering warning reliability.

The structural integrity of reinforced concrete utility poles relies heavily on the distribution of their internal rebars. However, existing non-destructive testing techniques struggle to precisely locate and quantify the dimensions of these slender reinforcements. To address this limitation, we propose an evaluation method based on time-of-flight acoustic tomography. By integrating the fast marching method with a quasi-Newton optimization algorithm, this approach accurately models wave propagation in complex media and performs nonlinear inversion of the velocity field. Extensive numerical simulations under both homogeneous and complex radial gradient backgrounds confirm the algorithm's robustness. To objectively assess imaging quality, we introduce novel quantitative metrics: intersection over union (IoU), relative diameter error (RDE), amplitude recovery (AR), and separability index (SI). The results demonstrate that increasing external excitation sources significantly enhances ray coverage density. Under optimal configurations, the IoU exceeds 70 % , and the RDE drops to approximately 5 % . Furthermore, resolution limit tests reveal that the algorithm can distinctly resolve independent rebars spaced more than 4.0 cm apart and successfully image those with a minimum radius of 1.0 cm . The evaluation framework established through these local physical metrics accurately quantifies the resolution limits of acoustic tomography, providing a reliable methodological basis for the high-precision inspection of utility poles and similar infrastructure.

From the perspective of fracture mechanics, the stability of goafs is closely related to the fracture instability of multi-pillar systems. To investigate the progressive evolution characteristics of instability in multi-pillar systems and the types of fracture sources that trigger such instability, an experiment on a multi-pillar system was conducted under uniaxial compression conditions. The entire process was monitored using digital image correlation analysis and acoustic emission monitoring. By calculating the digital speckle field on the surface of the rock specimen during the experiment, the evolution characteristics of the deformation and strain fields were analyzed from the beginning of loading to complete destruction. In addition, microcrack types were identified based on the RA-AF characteristic parameters. Large-amplitude acoustic emission events corresponding to major macroscopic crack formation were selected, and their seismic source mechanisms were inverted. The results revealed that the number of tension-type AE sources was significantly greater than that of shear-type sources. The failure mechanism, characterized by tension-dominated fracture and progressive chain reaction instability, was analyzed. Based on this mechanism, support measures and field recommendations were proposed.

Seismic source localization is an essential technique for the study of earthquakes. Accurate seismic source localization is important in seismic risk assessment. Various machine learning-based methods for earthquake monitoring and source localization have been proposed, along with the development of source localization techniques. However, these methods require a large amount of historical data for training, and acquiring the required data using monitoring stations may take years or even decades. Moreover, the acquired data often contain various seismic noise types that can affect the calculation results. To address this problem, we combine wavelet de-noising with convolutional neural network (CNN) to achieve fast source localization without any historically cataloged events. The results show that adding the wavelet de-noising technique improves the proposed model. In addition, provided that the regional model is known a priori, the method has a wide range of applications. For example, it can be applied to scenarios such as rock bursts in mines, microseismic events generated by mining, or big earthquakes. Based on this approach, we also have the potential to build a pickingfree, non-historical catalog, noise-robust, and fully automated location method.

In this study, we assess the state of the stress field in eastern Türkiye and discuss whether the stress field in the region has changed over time. To assess the governing stress field, we applied stress tensor inversion techniques using focal mechanisms from earthquake catalogs. The focal mechanisms were grouped into subregions based on spatial and temporal factors. We employed a damped regional-scale stress tensor inversion algorithm and an iterative joint inversion technique to determine the stress field for eastern Türkiye. Near the North Anatolian Fault Zone, the stress field exhibits strike-slip faulting with a slight counterclockwise rotation of the principal stress axes. From 1983 to 2016, reverse faulting was observed near Erzincan, transitioning to strike-slip faulting after 2017 due to changes in Smid and Smin axes. Near the East Anatolian Fault Zone, the stress field remains strike-slip, but after two major earthquakes in 2023, normal faulting emerged in areas with longitude less than 37 ^∘E , likely due to stress perturbations. In the easternmost region near the Zagros Fold Belt, reverse faulting dominates the north and south, while strike-slip faulting characterizes the central part. High R-values suggest frequent interchange of Smid and Smin axes. The damped inversion method effectively smoothens stress axis transitions in data-sparse regions but introduces errors in isolated areas, where the iterative method proves more reliable. These findings illuminate eastern Türkiye’s evolving tectonic stress field.

The stability of deeply buried tunnels is significantly influenced by the combined effects of primary joint fissures, blasting-induced damage, high-stress environments, and dynamic disturbances, all of which are key contributors to rock instability. The instability characteristics of rock masses under varying disturbance frequencies and amplitudes remain unclear, making it difficult to establish a reliable basis for tunnel management. This study measured the distribution of joint fissures on the tunnel surface at a burial depth of 1240 m, investigated rock failure characteristics through low-frequency perturbation true triaxial experiments, and analyzed support designs incorporating various combinations of metal mesh, bolts, anchor cables, and shotcrete. The results indicate that as the amplitude and frequency of disturbances increase, the number of cracks in the rock rises significantly and irregularly, while the fractal dimension of the rock's fracture direction decreases. When the disturbance reaches 10 MPa and 10 Hz, the fractal dimension decreases to a minimum value of 0.62. Additionally, the frequency of pore orientation at angles between 80° and 120° peaks at 52% of its maximum value, approximately 1.68 times that of the original rock. This suggests that the stress experienced by the particles within the rock becomes uneven after disturbance, leading to stress concentration and a pronounced fracture direction. Furthermore, as the amplitude and frequency of disturbances increase, the micropore area observed in scanning electron microscope (SEM) images initially increases rapidly, then continues to grow at a slower rate, with the rate of increase progressively diminishing. Simulations reveal that standard bolts in tunnels subject to dynamic disturbances can effectively resist disturbances with strengths below 40 MPa. However, when the disturbance intensity exceeds 70 MPa, the anchor's bearing capacity reaches its limit. In the case of bolt-supported tunnels subjected to dynamic disturbances, characteristics such as shallow anchoring depth, low preload force, significant separation of deep surrounding rock, and poor anti-damage ability of the bolts are observed. The use of highly prestressed anchor cable support can resist dynamic disturbances up to 100 MPa and enhance the tunnel's damage resistance. By combining stress and peak ground acceleration (PGA), the tunnel is classified into five potential risk levels (I to V). Based on this classification, a tunnel support strategy under high-stress disturbances is proposed. Practical applications demonstrate that implementing this strategy reduces the deformation of the surrounding rock by 42.47% to 51.07%, significantly improving the tunnel's stability.

The combination of high stress and dynamic perturbation is a critical factor contributing to deep rock instability. However, the mechanisms of rock energy dissipation and microcrack propagation under different perturbation frequencies and unloading conditions remain unclear. Consequently, there is no solid theoretical foundation for understanding deep rock instability or preventing related disasters. To investigate the mechanical response and damage characteristics of rock under perturbation, a model of crack propagation in rock columns subjected to high-stress perturbations was developed. A correlation between crack behavior and energy density was constructed based on true triaxial unloading-perturbation tests. The rock damage law under different perturbation frequencies (4 Hz, 8 Hz, 12 Hz, 16 Hz) and sigma(3) unloading conditions (0 MPa, 10 MPa) was analyzed. Additionally, micro-CT testing was conducted to explore the internal crack extension structure of the rock. A disturbance power function and an exponential energy-dissipation-driven crack propagation model were proposed and integrated into a unified instability criterion. This establishes a complete mathematical framework linking energy input, dissipation accumulation, crack evolution, and macroscopic failure. The results indicate that: (1) Micro-turbulence can intensify rock column instability under specific conditions, such as during the post-peak phase when the post-peak modulus is equal to or greater than the pre-peak modulus. Additionally, higher perturbation intensities lead to greater energy accumulation within the rock. (2) The spatial distribution of pores and cracks in altered rock under different perturbation frequencies and unloading conditions was revealed through true triaxial and CT scanning tests, providing an intuitive reflection of perturbation damage to the rock's fine structure. At 4 Hz, pore volume in altered rock is primarily distributed across the <= 106 mu m3, 106 similar to 107 mu m3, and 107 similar to 108 mu m3 ranges. As perturbation intensity increases, the proportion of pore volume within the <= 106 mu m3 range decreases significantly. When the perturbation frequency exceeds 12 Hz, the proportion of pore volume greater than 107 mu m3 reaches approximately 60 %, suggesting that perturbation leads to the formation of an internal crack lattice, indicating significant perturbation damage. (3) The three-dimensional crack field of eroded rock under perturbation was quantitatively characterized using a triangular mesh discretization technique, combined with an ellipsoidal model reconstruction algorithm and crack tensor theory. The relationship between the fracture grouping tensor and peak intensity was also established, revealing the mechanism by which perturbation affects the fine-grained structure and mechanical properties of eroded rock.

To efficiently realize backfilling mining with medium-deep hole caving in a gold mine, the rational determination of stope dimensions is essential. The Vlazov plate theory was employed to analyze the stress state and investigate the relationship between roof thickness and maximum tensile stress under varying stope spans. Since the latter serves as a criterion for evaluating roof strength failure, it is imperative to establish the appropriate range of parameters that ensure the rock mechanics stability during mining operations. Through central composite testing, numerical simulations were conducted to obtain mechanical response characteristics under different stope dimensions. Simultaneously, roof stress distributions and stope stability were analyzed. A second-order response surface model was constructed based on these findings, enabling the formulation of a comprehensive optimization framework. The interaction between variables within this framework was carefully considered when defining the objective functions for optimization. By integrating chaotic mapping into genetic algorithms, a multi-objective optimization approach was implemented, yielding 17 Pareto-optimal solutions. Ultimately, the optimized stope geometry was determined to have a chamber span of 31.89 m, a pillar span of 29.14 m, and a roof thickness of 5.35 m. This configuration represents the optimal balance between mechanical performance and mining efficiency in the context of medium-deep hole caving operations within the gold mine.

Elastic wave tomography is a non-destructive technique used to obtain velocity images of internal structures. Wave velocity tomography has been used to quantitatively describe abnormal structures and identify boundaries in different media and shapes. This research aims to quantitatively describe anomalous structures on a laboratory scale and identify boundaries in different media and shapes. Wave velocity tomography technology was applied to non-empty and empty anomalous areas, and the accuracy of the resulting velocity images was quantified. The reliability of boundary recognition was studied and analyzed. The accuracy of the results was found to relate to the size and shape of the anomalous structures estimated in the prior model, as well as the wave velocity difference between the anomalous and normal regions. In practical engineering, when the presence of abnormal areas cannot be determined, a completely homogeneous prior model is used. The results indicate that, although the inversion velocity may not be accurate, it is sufficient to identify boundaries. The larger the velocity difference, the clearer the boundary to be recognized. Furthermore, to assess the practical efficacy of this physical detection method, the wave velocity tomography technology was used to detect hidden goafs within a tantalum–niobium mine belonging to the Hunan Fuguihengtong Mining Company. Utilizing physical detection, 12 potential goafs and 100 confirmed goafs were identified within the mine, demonstrating the efficacy of the proposed empty anomalous area detection methodology in accurately identifying and delineating the boundaries of hidden goafs.

Several major earthquakes have taken place near the East Anatolian fault zone (EAFZ) in history. Despite extensive research on the Coulomb stress changes associated with these earthquakes, there remains a paucity of studies examining the spatial and temporal distribution of Coulomb stress near the East Anatolian fault zone over extended periods. This study investigates the changes in Coulomb stress induced by significant earthquakes (≥6 Mw) near the EAFZ from 1986 to 2023. High-stress changes (1.5–2.5 bar) were observed along the fault’s northeastern and southwestern segments, indicating a high likelihood of future seismicity. We also found that the three major earthquakes between 1986 and 2003 had little impact on subsequent major seismic events in the vicinity. However, the 2020 Mw 6.8 earthquake generated a Coulomb stress increment exceeding 0.1 bar, which influenced nearby seismic activity for two years. This suggests that the 2023 major earthquakes were likely facilitated by this stress change. Parameter sensitivity analysis shows fault strikes significantly affect calculations, highlighting the importance of accurate source mechanisms for reliable results. The findings of this study offer critical insights for seismologists and geophysicists aiming to refine earthquake-triggering models and stress transfer mechanisms. Civil engineers and urban planners can utilize the identified high-stress zones to prioritize seismic retrofitting of infrastructure.

The first Sino-German workshop on "Deep-sea mining of massive sulfides: balancing impacts on biodiversity and ecosystem, technological challenges and law of the sea" took place from September 17 to September 23, 2023 in Changsha, Hunan Province, China. Four themes were covered by 20 impulse talks, (1) seabed resources and mineralization systems, marine geology and geochemistry, (2) microbiology and marine ecology, (3) deep-sea mining technology, mineral processing and extractive metallurgy, and (4) law of the sea and international law applicable to the marine environment in Areas Beyond National Jurisdiction, respectively. In round table discussions, the interdisciplinary understanding deepened regarding (i) the distribution of submarine massive sulfides (SMS), their formation mechanisms and the abundance of SMS resources, (ii) the biodiversity linked to SMS and hydrothermal vents and the environmental protection requirements, (iii) the challenges of mining technology and processing of SMS, as well as (iv) the legal framework, the regulatory challenges, the international environmental liability regime and due diligence obligations for commercial seabed mining. The participants covered all four themes and are affiliated with various universities, research institutions, and governmental geoscientific authorities from China (seven) and Germany (six). During the workshop, a number of recommendations to ISA were defined regarding environmental, methodological, technical, and legal issues.

Clustering methods aim to categorize data or samples into distinct groups based on their similarity. When applying clustering methods to earthquake events, it is crucial to establish a metric for quantifying the similarity between these events. Directly applying this clustering method to a catalog of mining-induced seismicity may lead to clustering earthquake events induced by different mining activities or accidents into the same group. To address this issue, a two-step clustering method has been proposed and applied for analyzing a catalog of mining-induced seismicity. The first step involves spatial distance-based clustering of seismic events, while the second step focuses on moment tensor analysis-based clustering of these events. The results obtained from the MT-based clustering method are visualized using Hudson Graphs, and box plots serve as an evaluation tool for assessing the quality of MT clustering. Most box plots demonstrate desirable quality in terms of MT cluster results, indicating successful outcomes. By the proposed two-step clustering method combined with actual mining activities, the potential accident locations and categories can be hypothesized while valuable recommendations provided for mining operations.

During true triaxial experiments, it is impractical to directly affix sensors to the rock sample, which consequently gives rise to a heterogeneous velocity structure extending from the source of acoustic emissions to the sensors. In pursuit of ascertaining the travel path of acoustic emission waves under anisotropic conditions and comprehending the evolution of wave velocity during triaxial loading, we conducted cooperative event localization in conjunction with velocity tomography. Initially, a numerical test was executed to validate the precision and stability of the employed fast-marching tomography method. Subsequently, true triaxial loading was applied to a granite rock specimen. The algorithm's accuracy was corroborated by the congruence between the final locating results and the observable crack positions. The tomography inversion results indicated that the wave velocity field remained relatively stable when the maximum principal stress was below 16 MPa, despite the occurrence of numerous acoustic emissions during this stage. The P-wave velocity exhibited a discernible upward trend with increasing maximum principal stress, particularly evident after reaching the 40 MPa threshold. Nevertheless, it's important to note that stress escalation does not invariably correspond to fracturing during the elastic deformation phase under confining pressure. The inversion method employed here enables the visualization of variable velocities and provides insight into the rock's deformation physics.

为提高巷道围岩松动圈预测准确率,给围岩支护和地压管理提供更科学的指导,提出了一种新的预测方法.采用改进的Adaboost回归算法对3种机器学习算法进行集成优化,即在Adaboost回归算法中寻找误差率阈值的最优值,实现Adaboost全局最优的集成效果.应用网格搜索对BP、SVM和RF的超参数进行优化,建立BP-Adaboost、SVM-Adaboost和RF-Adaboost回归预测模型.结果表明:BP-Adaboost模型的预测性能最好,误差率为7.65%.结合矿山松动圈测试实例进行验证分析,平均相对误差为4.15%.因此,所提出的模型能够为围岩松动圈预测提供参考,可以满足工程应用的需求.

Classification of rock micro-fractures by acoustic emission (AE) parameters is of great significance for rock health monitoring, instability assessment, and precursor warning. But the criteria have not yet been universally formed for the most commonly used method employing rise angle (RA) and average frequency (AF). We conducted expansion rupturing experiment and elastic wave attenuation experiments to investigate the uncertainties of the RA-AF method. Results show the range of the RA-AF distribution extends with the reduction of the AE source scale. The RA-AF moves to the shear-type area in the axis for AE hits with delayed triggering. The RA increase togethering with AF decreasing when the specimen become more compact and smaller in size. It indicates that the fixed micro-fracture reference line is difficult to match potential changes in the RA-AF distribution and the classification criteria is highly dependent on the experimental environment. The uncertainty of the RA-AF method is influenced by the ray path and the source scale. The underlying reason is the uncoordinated distortion between the numerator and denominator in the RA-AF calculation caused by the attenuation and dispersion of elastic wave as well as the measurement error of characteristic parameters. It is concluded that the characteristics of RA-AF are available to understand the comparative relation of different micro-fracture types, but quantify their relations by the absolute proportion requiring consideration of a number of prerequisites. This work not only clarifies the phenomena and reasons for the uncertainty of the RA-AF method but also provides theoretical and experimental guidance for more rational improvement and engineering application.

Strainburst poses significant risks to the safety of workers in deep underground engineering. Assessing strainburst potential plays a crucial role in disaster prevention. Due to the anisotropy and heterogeneity of rock mass, it is essential to quantify the strainburst potential from the perspective of probability. This study aims to propose a methodology that integrates Monte Carlo simulation (MCS) and machine learning (ML) algorithms to evaluate the probability of strainburst potential. First, a numerical model based on damage initiation and spalling limit (DISL) method is established. Then, a novel indicator, absolute local energy release rate (ALERR), is proposed to assess strainburst potential, which describes the absolute value of elastic strain energy released after rock mass failure. The location of the maximum value of ALERR is used to determine the depth of outburst pit, which is adopted to evaluate the strainburst potential level. So, the quantitative relationship between strainburst potential and ALERR can be established. Thereafter, a strainburst dataset including six variables and the depth of outburst pit is obtained based on the MCS method and numerical model. To improve the computational efficiency, seven different ML algorithms are integrated with MCS to calculate the probability of strainburst potential, respectively. Finally, the proposed methodology is used for the strainburst potential evaluation in the 3# headrace tunnel of Jinping II hydropower station. Results show that random forest (RF) and gradient boosting (GB) algorithms have better evaluation performance and can be combined with MCS to calculate the probability of strainburst potential reliably. The proposed methodology can provide valuable guidance for the probability assessment of strainburst potential.

Precise stochastic approaches to quantitatively calculate the source uncertainties offers the opportunity to eliminate the influence of anisotropy on moment tensor inversion. The effects of ignoring anisotropy were tested by using homogeneous Green’s functions. Results indicate the influence of anisotropy and noise on fault plane rotation is very small for a pure shear source whether it is restricted to double couple solution or full moment tensor solution. Green’s functions with different prior rough anisotropy information were tested, indicating that the complex source is more sensitive to velocity models than the pure shear source and the fault plane rotation caused by full moment tensor solution is larger than the pure double couple solution. Collaborative P-wave velocity inversion with active measurements and passive acoustic emission data using the fast-marching method were conducted, and new Green’s functions established based on the tomography results. The resolved fault plane solution rotated only 3.5° when using the new Green’s functions, but the presence of spurious isotropic and compensated linear vector dipole components was not completely eliminated. It is concluded that the cooperative inversion is capable of greatly improving the accuracy of the fault plane solutions and reducing the spurious components in the full moment tensor solution.

微震事件被动监测技术和震源定位技术大大提高了人们对岩体破裂和断层活动的理解.针对某矿山微震事件频发、岩体垮落严重等问题,采用一种新的包含频域拟合和时域拟合的全波形矩张量反演路线,探寻适合该矿山三维监测网络下的微震事件矩张量反演方法,确保能够快速计算矿山微震事件的矩张量参数及断层面解,能够对矩张量进行快速分解并识别岩体的破裂类型.根据计算,该矿山在不同带通滤波器下反演所得的全波形矩张量分解出的双力偶断层面解是一致的,均以剪切为主.