Search Results (261)

With the increasing depth of coal mining, thick-hard overlying strata (THOS) often induce dynamic disasters such as rockbursts, posing significant threats to mine safety. This study focuses on the application of directional hydraulic fracturing roof pressure relief technology (HFRPRT) as a key disaster prevention technology in the Hongqinghe Coal Mine’s 3^-1302 longwall face. An integrated monitoring system combining microseismic (MS) and acoustic emission (AE) data was established to quantitatively evaluate the fracturing process through multi-indicator analysis, including support pressure response, energy distribution, and surface subsidence. The results demonstrate that HFRPRT effectively weakened THOS integrity, reducing periodic weighting intervals by 25% and peak pressure intensity by 21.95%. Daily AE energy and event count increased by 154% and 636%, respectively, indicating enhanced microfracture propagation. MS events shifted to lower-energy patterns, with second-order events predominating (59.16%), highlighting the technology’s role in mitigating elastic energy accumulation and dynamic hazards. This research provides a theoretical foundation for optimizing hydraulic fracturing parameters in similar geotechnical conditions, advancing coal mine disaster prevention strategies. Full article

Underground mining-induced surface subsidence poses significant risks to overlying structures, infrastructure, and the environment. Overburden delamination grouting has emerged as an effective technique to mitigate subsidence, but its design requires a comprehensive understanding of fractured-zone development, grouting-layer placement, isolation-layer stability, and grout material performance. This study developed an integrated methodology for overburden delamination grouting in longwall mining by combining fractured- and bending-zone analysis, grouting-layer design, isolation-layer stability evaluation, grout material strength design, and surface-subsidence monitoring for performance assessment. The mechanical properties of grout materials were systematically evaluated through laboratory testing, including compressive behavior and stress–strain response. Results indicate that ternary mixtures exhibit the best compressive stability, with a fly ash–coal gangue–slag powder ratio of 4:3:3 achieving a compressive ratio of 8.2%. The proposed workflow and selected materials were validated through three representative engineering case studies, demonstrating practical applicability under varied geological and mining conditions. Surface-subsidence monitoring results show that grouting effectively reduces subsidence and supports the continued safe performance of overlying structures. This study offers both theoretical guidance and practical solutions for sustainable subsidence control in underground mining. Full article

Precise monitoring of damage evolution in coal-rock mass during mining emerges as a paramount requirement for developing accurate early warning systems for coal burst hazards. However, limited research has demonstrated the integrated damage characteristics of the coal-rock mass under static and dynamic loads during longwall mining. Therefore, in this paper, two novel seismic monitoring approaches, the Seismic Cluster Index (CI) and the Number of High Ground Motions (NHGMs), are developed to study the evolution of coal-rock mass damage during longwall mining under static and dynamic loads, respectively. Two months of monitored seismic data from a burst-prone longwall are used for analysis. The results show that CI can depict coal-rock damage conditions under static load, which identifies coalescence of fractures based on seismic source sizes and inter-event distances. Ground motion intensity has a positive correlation with seismic energy. The induced dynamic disturbance to roadways can further weaken the coal-rock mass, depending on the distance from the seismic sources. High-intensity dynamic disturbances, as indicated by elevated NHGMs and accelerated increments, strongly correlate with coal-burst damage. The proposed CI and NHGMs framework evaluate coal-rock mass damage and forecasts coal burst hazards, validated by the correlation between high CI/NHGMs values and actual burst locations. Full article

In the face of the urgent need for sustainable practices in the coal industry, we propose a novel green cut-and-fill mining method aimed at achieving material self-sufficiency and mitigating overburden subsidence. This method leverages the goaf roof as an in situ filling material, integrating long-wall caving mining efficiency with partial filling techniques. Through laboratory analog material modeling, numerical simulations, and structural mechanics modeling, we compare the performance of cut-and-fill mining and traditional caving mining methods. The results show that the cut-and-fill method offers more uniform and controlled deformation behavior. Specifically, vertical and horizontal displacements along 40 m survey lines are significantly reduced, with a maximum reduction on the order of millimeters, compared to caving mining. Furthermore, the floor stress concentration coefficient is lower, and the total number of fractures decreases, with shear fractures reduced by 8.8% and tensile fractures reduced by 66.9%. The gangue column in the cut-and-fill method effectively supports the goaf roof, preventing fracture formation and extending the deformation time. The results demonstrate the effectiveness of the cut-and-fill method for subsidence control, suggesting its potential for achieving green and sustainable coal mining practices. Full article

Accurate identification and prediction of abnormal strata pressure in intelligent longwall mining faces are essential for ensuring mine safety and production efficiency. Although machine learning has been increasingly applied to hydraulic support resistance prediction, challenges remain in capturing the strong temporal dependency and periodic pressure characteristics associated with strata behavior. In this study, a novel abnormal strata pressure identification and prediction framework based on the Gated Recurrent Unit (GRU) integrated with an attention mechanism (AM) is proposed for fully mechanized coal mining faces. The model is designed to capture both short-term fluctuations and long-term cyclic characteristics of support resistance, thereby enhancing its sensitivity to dynamic loading conditions and precursory abnormal pressure signals. Results indicate that the proposed GRU-AM model achieves high prediction accuracy for both single-support and multi-support scenarios, with the predicted resistance closely matching the measured values. Compared with conventional LSTM and CNN models, GRU-AM demonstrates consistently improved performance across multiple evaluation metrics, including RMSE, MAE, MAPE, and Pearson correlation coefficient (R), in both short-step and long-step prediction tasks. At a 1 min step length, the model achieves an overall Accuracy of 0.9741 for abnormal pressure identification, and maintains a high Accuracy of 0.9195 at a 10 min step length. Field application across different mining conditions further confirms the robustness, computational efficiency, and practical reliability of the proposed method. These results demonstrate that the GRU-AM framework provides an effective and scalable solution for real-time abnormal strata pressure recognition and early warning in intelligent coal mining environments. Full article

Gas disasters in coal mines are the principal constraint on safe operations; accordingly, accurate gas time-series forecasting and real-time fluctuation monitoring are essential for prevention and early warning. A method termed Decomposition-Enhanced Cross-Graph Forecasting and Anomaly Finding is proposed. The Multi-Variate Variational Mode Decomposition (MVMD) algorithm is refined by integrating wavelet denoising with an Entropy Weight Method (EWM) multi-index scheme (seven indicators, including SNR and PSNR; weight-solver error ≤ 0.001, defined as the maximum absolute change between successive weight vectors in the entropy-weight iteration). Through this optimisation, the decomposition parameters are selected as K = 4 (modes) and $\alpha$ = 1000, yielding effective noise reduction on 83,970 multi-channel records from longwall faces; after joint denoising, SSIM reaches 0.9849, representing an improvement of 0.5%–18.7% over standalone wavelet denoising. An interpretable Cross Interaction Refinement Graph Neural Network (CrossGNN) is then constructed. Shapley analysis is employed to quantify feature contributions; the m1t2 gas component attains a SHAP value of 0.025, which is 5.8× that of the wind-speed sensor. For multi-timestep prediction (T0–T2), the model achieves MAE = 0.008705754 and MSE = 0.000242083, which are 8.7% and 12.7% lower, respectively, than those of STGNN and MTGNN. For fluctuation detection, Pruned Exact Linear Time (PELT) with minimum segment length L_min = 58 is combined with a circular block bootstrap test to identify sudden-growth and high-fluctuation segments while controlling FDR = 0.10. Hasse diagrams are further used to elucidate dominance relations among components (e.g., m3t3, the third decomposed component of the T2 gas sensor). Field data analyses substantiate the effectiveness of the approach and provide technical guidance for the intellectualisation of coal-mine safety management. Full article

The article is devoted to the issues of designing the exploitation of a seam deposit in the boundary areas of underground mines in terms of minimizing the risk of dynamic phenomena. Its main goal was to attempt to demonstrate the relationship between the method of extracting resources trapped in the boundary pillar and the magnitude of the induced seismicity of the rock mass accompanying this process. The substantive considerations concerned the single-wall model and were divided into two main parts—theoretical and verification. As part of the theoretical piece, based on model studies, a geomechanical assessment of the impact of the working face advance on changes in the stress–strain behaviour occurring in the burst-prone layer in terms of the possible loss of continuity of its original structure was carried out. The starting point for the key analyses were the results of numerical simulations based on the algorithms of S. Knothe and W. Budryk’s theories in combination with classical solutions of the mechanics of deformable bodies. Two variants of mining operations in a two-sided environment of goaf were considered, differing in the direction of progress, the degree of constraint of the start and end of the face advance, and mining circumstances in the vicinity of both sides of the advancing face. As part of the verification piece, the results of model analyses were related to an example polygon of a crossing longwall in one of the functioning, rockburst USCB hard coal mines. The scope of the research included a comparison of the experimentally indicated zones of occurrence of tremor-favourable effort processes in the roof of the seam with the actual location of the seismic phenomena foci recorded during the ongoing exploitation. The considerations included in the work formed the basis for formulating conclusions of a cognitive and applicable nature. Full article

As core pieces of transport equipment in longwall mining systems, scraper conveyors operate under extremely harsh and dynamic loading conditions. Their operational reliability and service life primarily depend on the performance of critical components within their drive systems, particularly the support bearings. However, complex and often unpredictable load spectra (such as severe impacts, vibrations, and contaminant ingress) pose significant challenges to the dynamic behavior and longevity of these bearings. Traditional static analysis fails to capture their true operating state, as it neglects transient effects, varying contact angles, and internal vibration excitation. This study conducts a comprehensive dynamic analysis of angular contact ball bearing 7205C to elucidate its dynamic response under actual operating conditions of scraper conveyors. Based on Hertzian elastic contact theory and bearing dynamics theory, the comprehensive stiffness of the angular contact ball bearing is derived, and the effects of axial force, rotational speed, and mass eccentricity on bearing performance are analyzed. The findings are expected to provide a theoretical foundation for optimizing bearing selection, predicting service life, and enhancing the overall reliability of mining machinery. Full article

The accurate real-time delineation of overburden failure zones, specifically the caved and water-conducted fracture zones, remains a significant challenge in longwall mining, as conventional monitoring methods often lack the spatial continuity and resolution for precise, full-profile strain measurement. Based on the hydrogeological data of the E9103 working face in Hengjin Coal Mine, a numerical calculation model for the overburden strata of the E9103 working face was established to simulate and analyze the stress distribution, failure characteristics, and development height of the water-conducting fracture zones in the overburden strata of the working face. To address this problem, this study presents the application of a distributed optical fiber sensing (DOFS) system, centering on an innovative fiber installation technology. The methodology involves embedding the sensing fiber into boreholes within the overlying strata and employing grouting to achieve effective coupling with the rock mass, a critical step that restores the in situ geological environment and ensures measurement reliability. Field validation at the E9103 longwall face successfully captured the dynamic evolution of the strain field during mining. The results quantitatively identified the caved zone at a height of 13.1–16.33 m and the water-conducted fracture zone at 58–60.6 m. By detecting abrupt strain changes, the system enables the back-analysis of fracture propagation paths and the identification of potential seepage channels. This work demonstrates that the proposed DOFS-based monitoring system, with its precise spatial resolution and real-time capability, provides a robust scientific basis for the early warning of roof hazards, such as water inrushes, thereby contributing to the advancement of intelligent and safe mining practices. Full article

This paper presents a hybrid methodology for predicting rock mass deformation and roadway loads induced by longwall mining. The approach combines the classical Budryk–Knothe influence function model with numerical simulations in the FLAC3D finite difference environment. Instead of explicitly reproducing large-scale excavation and caving, the impact of mining is introduced through analytically derived displacement boundary conditions applied to the numerical model. This allows detailed analyses of the rock mass deformation state while significantly reducing computational effort compared with conventional geomechanical models. The methodology involves deriving displacement components from the Budryk–Knothe influence function, implementing them through Python 3.6.1 scripts in FLAC3D 7.00, and performing stepwise simulations of longwall advance. Results show that the proposed approach reduces the number of finite difference zones by nearly an order of magnitude, achieving more than a tenfold decrease in computation time. At the same time, the displacement and stress distributions obtained remain consistent with both the analytical Budryk–Knothe solution and those from the classical numerical model. The study demonstrates that this methodology provides a reliable and efficient tool for assessing stress redistribution and deformation around roadway excavations influenced by mining. Its application enhances the accuracy of deformation predictions, supports support system design, and improves safety and efficiency in underground mining operations. Full article

Accurate source locating and a complete data catalogue of the seismic network are the prerequisites for seismic analysis methods to identify coal burst risks. Comprehensively understanding the spatial characteristics of source location errors and seismic data integrity is a key insight for optimising seismic networks and enhancing monitoring performance. Based on the monitored seismic data in a burst-prone longwall, this study develops two novel methodologies, Emulation-Testing-based Source Locating Accuracy Analysis (ETSLA) and Probability-based Magnitude of Completeness (PMC) method, to evaluate seismic monitoring performance in underground coal mines. The results indicate that ETSLA effectively quantifies vector characteristics of source location errors, revealing anisotropic error distributions in the studied longwall. The PMC method presents significant differences among geophones regarding their wave detection capacities. The detection probability of the seismic network for the events demonstrates progressive enhancement with increasing energy magnitude. In field practice, ETSLA can correct misclassified burst types by accounting for location errors. The Seismic data inferred using the PMC method can retrace missing seismic activity, and the inferred high-energy zones accurately correlate with actual burst damage locations. The study can serve as a reference to enhance the quality of seismic monitoring for precise early warning of coal burst risks. Full article

In response to the imperative to mitigate methane—one of the most potent greenhouse gases—this study proposes and tests an integrated workflow for designing methane drainage boreholes targeting post-mining areas in an active underground coal mine (Pniówek, Poland). The workflow combines the following: (1) forecasting methane emissions from goafs and active longwalls for 2024–2040; (2) 3D geological characterization (structural and lithofacies models); (3) selection and sealing of goaf zones; and (4) optimization of well placement, drilling, and performance evaluation of drainage boreholes, including an assessment of energy use from the recovered gas. Applying the method delineated priority capture zones and estimated recoverable rates under multiple scenarios. Preliminary field data from a borehole near seam 362/1 indicate stable methane inflow to the drainage system and a concomitant reduction in methane load within the ventilation network. The integrated design improves targeting efficiency and provides a quantitative basis for scheduling, risk management, and sizing of surface-to-underground infrastructure. The results suggest that systematic drainage of post-mining voids can enhance safety, limit fugitive emissions, and create opportunities for on-site power generation. The approach is transferable to other active mines with legacy workings, provided site-specific calibration and monitoring are implemented. Full article

The Shendong mining area, a pivotal coal production base in China, faces considerable challenges due to extensive mining activities. The significant development of overlying rock fractures and the widespread occurrence of surface cracks present a major challenge to mining safety and ecological preservation in China and other mining nations. This study focuses on the Panel 12,401 fully mechanized longwall face at Shangwan Coal Mine to systematically investigate overburden movement and the evolution of surface fractures. By combining UDEC discrete element modeling with a computational framework that links subsurface strata subsidence and surface settlement, this research examines the spatial and mechanical properties of fracture propagation. Experimental results show that surface fractures continue to develop as the working face advances, with their horizontal apertures gradually decreasing and eventually closing after the face passes. Both the maximum surface subsidence and the maximum fracture aperture exhibit a strong positive correlation with mining height. In contrast, increased mining depth leads to reductions in maximum surface subsidence, the subsidence factor, and the size of surface fracture apertures. These findings provide a theoretical basis for reducing mining-induced damage and promoting ecological restoration in mining areas. Full article

The objective of this study is to quantify and characterize ground deformations induced by underground coal mining in the Karaganda coal basin, Kazakhstan, in order to improve the understanding of subsidence processes and their long-term evolution. The SBAS-InSAR method was applied to Sentinel-1 (C-band) and TerraSAR-X (X-band) data from 2019–2021 to estimate the magnitude, extent, and temporal behavior of displacements over the Kostenko, Kuzembayev, Aktasskaya, and Saranskaya mines. The results reveal spatially coherent and progressive deformation, with maximum cumulative LOS displacements exceeding –800 mm in TerraSAR-X data within active longwall mining zones. Time-series analysis confirmed acceleration of displacement during active extraction and its subsequent attenuation after mining ceased. Comparative assessment demonstrated a strong agreement between Sentinel-1 and TerraSAR-X results (r = 0.9628), despite differences in resolution and acquisition geometry, highlighting the robustness of the SBAS-InSAR approach. Analysis of displacement over individual longwalls showed that several panels (3, 5, 8, 15, and 18) already exceeded their projected maximum subsidence values, underlining the necessity of continuous monitoring for ensuring safety. In contrast, other longwalls have not yet reached their maximum deformation, indicating potential for further activity. Overall, this study demonstrates the value of multi-sensor InSAR monitoring for reliable assessment of mining-induced subsidence and for supporting geotechnical risk management in post-industrial regions. Full article

This article presents a concept for modernizing the transport system of high-performance coal mines through the transition from traditional monorail to rubber-tyred transport (RTT). The study was conducted based on materials from the V.D. Yalevsky Mine of JSC “SUEK-Kuzbass” with daily longwall output up to 60,000 tons and production capacity up to 10 million tons per year. Analysis of the existing transport system efficiency revealed low equipment utilization rates (52–70%) and significant time losses during shift changeovers (up to 4.3 h/day in development workings). Technical solutions for phased RTT implementation were developed, including six roadway surface scenarios and a fleet composition of 60 specialized equipment units. The research methodology is based on time study observations using the automated “Granch” system, analysis of equipment utilization coefficients, and economic–mathematical modeling using NPV, MIRR, and payback period. The transition to rubber-tyred transport provides a five-fold increase in travel speed (from 4.5 to 25 km/h), reduction in shift changeover time to zero, increase in operating time by 20% in development and 4.5% in extraction, and a reduction in longwall move duration from 173–209 to 88 days. Additional coal production amounts to 6.5 million tons. Economic justification shows NPV of USD 64.2 million with MIRR of 2.4% and a payback period of 4.5 years. Full article