Search Results (1,707)

The severe deformation and failure of reused roadways due to repeated mining disturbances pose considerable challenges to roadway maintenance. In this study, field measurements were taken at the 13092 reused roadway of Zhaozhuang Coal Mine to determine the deformation characteristics of its surrounding rock. Based on the equation for the plastic zone boundary of a circular roadway under a non-uniform stress field, the distribution characteristics of the plastic zone of the reused roadway under different stress conditions were analyzed, and their associated risk levels were assessed. Furthermore, the distribution characteristics of the plastic zone at different locations under primary and secondary mining, the non-uniform evolution of the mining-induced stress field, and the deformation behavior of the surrounding rock under repeated mining disturbances were investigated using FLAC3D 7.0 numerical simulations. The following conclusions were reached: Repeated mining is the primary cause of severe deformation and instability of the surrounding rock in the reused roadway, and there are marked spatial differences in severe deformation between different locations. Under a non-uniform stress field, the distribution of the plastic zone in the surrounding rock varies markedly with the ratio of the maximum principal stress to the minimum principal stress (λ). Specifically, as the ratio λ grows, the shape of the plastic zone evolves from circular to elliptical and ultimately to a butterfly shape. Once the plastic zone becomes butterfly-shaped, further increases in λ cause rapid expansion of the plastic zone. Under repeated mining disturbances, the plastic zone of the surrounding rock can be regarded as a superposition of plastic zones induced by multiple mining activities. The stress distribution of the surrounding rock is markedly different at different locations. The ratio λ, which is the dominant factor responsible for the distinct deformation and failure modes observed in different regions, also varies spatially. Based on these findings, a grouting reinforcement control technique was proposed. The grouting timing, grouting pressure, and grouting radius were determined to formulate a practical grouting control scheme for field application. Field tests demonstrate that the proposed grouting control method effectively covers the deformation range of the surrounding rock and achieves satisfactory control performance. The results of this study are expected to provide a valuable reference for grouting reinforcement control in similar mining scenarios. Full article

Ventilation network feature graphs (Q-H graphs) are a key visualisation tool for mine ventilation systems, and their automated generation reduces to a combinatorial optimisation problem over independent-path permutations. Existing methods, however, exhibit three limitations: a single-dimensional evaluation criterion, inadequate nodal pressure-energy assignment, and unstable convergence in factorial-scale search spaces. This paper proposes an adaptive NSGA-II (A-NSGA-II) framework with coordinated enhancements at the evaluation, modelling, and algorithmic levels. A three-objective system that minimises split-block count, topological-spatial discrepancy, and layout fragmentation is established, together with an aggregate evaluation score (AES) for engineering decision-making; nodal pressure energies are reconstructed via the longest path on a directed acyclic graph; and topology-aware initialisation, Lagrange three-point interpolated adaptive operators, and periodic memetic local search are integrated within NSGA-II. Experiments on two mine ventilation networks (75 and 112 branches) over 30 independent trials show that A-NSGA-II consistently outperforms four benchmarks (NSGA-II, MOEA/D, SPEA2, and MOSA) in terms of split-block count, AES, and hypervolume; statistical tests confirm significant, large-effect HV advantages on the 112-branch network, while the 75-branch network shows a 56.6–71.5% reduction in HV standard deviation. Full article

Backfilling the industrial solid waste coal gangue into deep coal mine goafs for CO₂ geological sequestration is a crucial pathway to achieve the synergistic effect of pollution reduction and carbon mitigation. However, in complex deep geological environments, the chemical evolution of multiple mineral phases of coal gangue under gas–water–rock coupling effects and the carbon-controlling mechanism of residual total organic carbon (TOC) remain unclear. In this study, coal gangue from the goaf of the Xiaobaodang Coal Mine was used as the research object. Relying on a customized high-temperature and high-pressure reaction system to simulate the deep in situ environment (45 °C, 10 MPa), and combined with X-ray diffraction (XRD), total organic carbon determination, and isothermal CO₂ adsorption experiments, the geochemical mechanism by which inorganic minerals and organic residual carbon synergistically control the ultimate CO₂ adsorption potential was systematically revealed. The results show that the modification of the CO₂ adsorption potential of coal gangue by gas–water–rock reactions exhibits strong mineral phase differentiation. Systems rich in active silicates generate a large amount of secondary clay minerals through intense carbonation alteration, achieving a significant increase in micro–nano pores and absolute adsorption capacity. Systems rich in carbonates steadily release deep primary adsorption potential by widening mass transfer channels through mineral dissolution. In contrast, systems rich in primary clay minerals face an irreversible attenuation of adsorption space due to physical clogging of pore throats caused by fluid migration. Furthermore, the initial organic carbon content exerts a significant non-linear regulatory effect on the development of the micropore network. The physical adsorption sites provided by the high relative content of layered clay minerals (>41%), coupled with the interfacial enhancement effect exerted by a moderate organic carbon content (0.12~0.16%), constitute an optimal physicochemical synergistic enhancement network, which is the core geological reason for stimulating the ultimate carbon sequestration capacity of coal gangue. The results of this study not only enrich the multiphase interfacial thermodynamic theory of complex heterogeneous geological bodies but also provide solid theoretical support for the precise optimization of target areas and the long-term evaluation of carbon sinks in goaf CO₂ sequestration engineering. Full article

Freeze–thaw cycles cause mechanical deterioration and instability of slope rock masses in open-pit coal mines located in the cold regions of Northwest China. In this study, the research object is fine-grained sandstone from the Yan’an Formation in the Tarangole mining area of the Ordos Basin. Here, indoor freeze–thaw cycling, uniaxial compression, and triaxial compression tests were conducted to systematically analyze the deformation behavior, strength evolution, and failure modes of the sandstone under varying numbers of freeze–thaw cycles, freezing temperatures, and confining pressures, thereby revealing its freeze–thaw damage mechanism. The results show that the number of freeze–thaw cycles is the dominant factor affecting the elastic modulus. Freezing temperatures (especially between −5 °C and −15 °C) and the number of freeze–thaw cycles (particularly the first 10 cycles) significantly reduce peak strength. In addition, confining pressure can significantly enhance the resistance to deformation (under 15 freeze–thaw cycles, the elastic modulus increases by 181.8% as confining pressure rises from 0 to 2 MPa). Within the low confining pressure range (0–1.5 MPa), peak strain decreases monotonically with increasing confining pressure and is independent of the number of freeze–thaw cycles. Finally, the increase in the number of freeze–thaw cycles and the decrease in temperature jointly promote crack development, and the failure mode shifts from pure shear to a shear-tension composite mode. The underlying cause lies in the evolution of interparticle cementation within the soil skeleton and in the associated pore–crack structure. In addition, based on fracture damage mechanics and the modified Weibull distribution, a damage evolution equation and a constitutive model for sandstone considering freeze–thaw cycles and temperature effects were established and validated. Therefore, the research findings can provide a theoretical basis for slope support, freeze–thaw disaster prevention and mitigation, and stability assessment in the Tarangole mining area and other cold regions. Full article

Rock pillars in deep underground mines are subjected to complex stress environments. The combined effects of in situ stress and cyclic disturbances from mining activities lead to a redistribution of the surrounding rock mass stress field, which readily triggers instability and failure, posing severe threats to mining engineering safety. To investigate the damage mechanism of cyclic loading on rock and its weakening effect on the bearing capacity of mine pillars, this study takes limestone as the research object. A series of uniaxial compression tests were conducted on limestone specimens subjected to triaxial cyclic pre-damage, complemented by numerical simulations to further characterize the energy and deformation evolution of the damaged limestone under cyclic loading conditions. The findings are as follows: (i) Triaxial cyclic tests on limestone show that both the input energy and dissipated energy follow similar trends, decreasing rapidly in the initial stage before stabilizing. The elastic strain energy remains largely constant, with most of the input energy being stored as elastic strain energy. Under constant stress levels and cycle numbers, increases in confining pressure and frequency reduce the rock’s input energy, elastic strain energy, and dissipated energy. (ii) The peak stress of damaged limestone exhibits a positive correlation with the pre-damage confining pressure and cyclic frequency, while it decreases with an increasing number of cycles. Higher confining pressure and frequency raise the input energy, elastic potential energy, and dissipated energy at the peak stress point. (iii) Deformation and failure in damaged limestone originate from the development and propagation of localized deformation zones. Increased lateral displacement within these zones promotes the formation of macroscopic fractures. Due to significant structural heterogeneity inside the localized areas, the evolution of deformation energy is influenced by regional characteristics. (iv) Simulation results indicate that the uniaxial compressive failure of limestone involves the accumulation and propagation of micro-scale tensile cracks, which ultimately coalesce into macro-scale shear fracture surfaces. During uniaxial loading of pre-damaged limestone, newly generated cracks predominantly initiate around pre-existing cracks, with only a limited number distributed randomly. Their peak intensity shows a positive correlation with the pre-damage confining pressure. Full article

Fractured coal in the residual-strength stage is a primary medium for gas migration and drainage in deep mining areas. To investigate the hydro–mechanical seepage response of post-peak fractured coal under constant-pressure-difference conditions, triaxial CO₂ seepage tests were conducted on coal specimens collected from the Xinyuan Coal Mine. A Weibull-based damage constitutive model was established to characterize the confining-pressure-induced hysteresis in the damage-evolution path. The flow-rate evolution and Reynolds number analysis indicated that gas flow remained within the linear Darcy regime. A controlled-variable analysis was used to examine the competing effects governing permeability evolution. Mechanical compaction induced an exponential decrease in permeability, whereas the decrease in permeability with increasing pore pressure was interpreted, within the proposed model framework, as the combined effect of possible adsorption-induced matrix swelling and weakened gas slippage. To address the limitations of conventional constant-slip-factor models, a pressure-dependent slip modulation coefficient was introduced into a composite permeability equation incorporating effective stress, adsorption-related deformation, and dynamic gas slippage. Global nonlinear fitting yielded R² = 0.97 and an RMSE of 0.1909, with the residuals generally distributed around zero, supporting the fitting reliability of the model within the investigated stress–pressure range. Response-surface analysis identified mechanical compaction as the dominant controlling mechanism, while adsorption-related deformation and gas slippage acted as secondary correction mechanisms. The proposed framework provides a quantitative basis for distinguishing the mechanical and fluid-related effects governing permeability evolution in post-peak fractured coal. Full article

To elucidate the molecular structural characteristics of weakly caking coal and the microscopic mechanism by which CO₂ inhibits coal–oxygen complexation, a weakly caking coal sample from the Dahaize coal mine in Shaanxi, China, was investigated using proximate and ultimate analyses, FTIR, XPS, and ¹³C NMR. On this basis, a representative coal macromolecular model was constructed and further analyzed using density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulations. The molecular formula of the representative weakly caking coal from the Dahaize mine (RNM) unit was determined as C₁₇₆H₁₅₆N₂O₁₉S₂. The aromatic carbon fraction was 65.41%, and the bridge carbon/peripheral carbon ratio was 0.25, indicating a certain degree of aromatic condensation but a limited content of highly fused aromatic structures. DFT calculations revealed that the reactive sites were mainly located around edge oxygen-containing functional groups and bridging structures, with a maximum Fukui index of approximately 0.024. Adsorption simulations showed that O₂ and CO₂ adsorption on RNM followed Langmuir-type behavior over 303.15–363.15 K: adsorption capacity increased with pressure and decreased with temperature. At 8000 kPa, the CO₂ uptake was approximately 1.6 times that of O₂. In the binary O₂-CO₂ system, CO₂ preferentially occupied pore surfaces and high-energy adsorption sites, reducing the local enrichment of O₂. These results provide a molecular-level explanation for the inhibition of coal–oxygen complexation by CO₂ through competitive adsorption, site shielding, and decreased oxidation probability at active sites. Full article

Accurate modeling of underground mine ventilation requires reliable estimates of roadway aerodynamic resistance. Conventional methods, based on geometric surveys or barometric pressure measurements, have notable limitations, including neglect of local losses, high time requirements, and sensitivity to environmental disturbances. This paper introduces a two-point flow-based method for determining roadway resistance directly from in situ measurements. Using basic instruments (anemometer, differential manometer, thermometer, and hygrometer), measurements are taken at two points along a straight airway. The pressure drop is calculated via the Bernoulli equation, allowing resistance to be determined without relying on geometric data or friction assumptions. This method captures both frictional and local losses inherently. Field testing in five roadway sections of a coal mine in Vietnam yielded resistance values 10–15 times higher than theoretical friction-only estimates, highlighting the importance of local losses. The equivalent cross-sectional areas back-calculated from the measured resistance using literature-based friction factors showed consistency with geometric survey data (typical deviation 3–6%), indicating internal coherence of the measurements. Full validation against independent barometric or CFD methods remains a subject of ongoing research. The method is simple, fast, minimally disruptive, and compatible with ventilation modeling tools. It provides a practical and accurate alternative for resistance estimation under real operating conditions. Full article

Shallow-buried coal seams in western China are commonly overlain by deeply incised gully terrain, where mining is often accompanied by coal-wall spalling and abnormal increases in support resistance, which affect safe and efficient production. To investigate overburden failure during shallow-buried coal seam mining under gully terrain and to clarify the support–resistance mechanism, a typical working face was selected as the engineering background. Physical similarity simulation, 3DEC numerical simulation, and theoretical analysis were used to analyze overburden failure characteristics and the coupled evolution of the stress, displacement, and fracture fields. Mechanical models of key-stratum fracture and a support–resistance estimation model were established to reveal the influence of overburden-thickness variation on key-stratum fracture and support resistance. The results show that overburden failure in gully areas exhibits pronounced stage-dependent and asymmetric characteristics. In the similarity simulation, the initial fracture intervals of the key stratum in the downhill section were 32 m and 36 m, indicating an asymmetric fracture pattern with a shorter span on the left side and a longer span on the right side. In the uphill section, the periodic fracture interval of the key stratum decreased from 30 m to 24 m as the overburden thickness increased. During overburden failure in gully areas, the three fields exhibited a coupled relationship: stress concentration at the working face caused overburden failure and subsidence, which promoted fracture propagation, whereas stress redistribution in the goaf compacted the fractured overburden and promoted fracture closure. The overburden failure characteristics differed significantly between mining stages. During downhill mining, the key stratum behaved as a fixed-ended beam with a relatively large fracture interval, whereas during uphill mining, it formed a cantilever beam, and its fracture interval decreased with increasing overburden thickness. The loading mechanism of support resistance was shown to be jointly controlled by variations in gully overburden thickness and key-stratum fracture. During downhill mining, support loading increased gradually under the support of the fixed-ended beam key stratum. During uphill mining, support loading exhibited periodic abrupt increases under the combined effects of increasing overburden thickness and periodic fracture of the cantilever-beam key stratum. These findings provide a theoretical basis for strata pressure control at working faces in gully areas. Full article

Sustainable land-use regulation in historical and cultural cities requires balancing heritage conservation, development demand, cropland retention, and urban–rural spatial restructuring. However, the stage-wise reorganization of urban–rural construction land under these coupled pressures remains insufficiently understood. Taking Jingzhou District, China, as a case study, this study uses land-use data from 2000, 2005, 2010, 2015, and 2020 and integrates stage-wise random-forest analysis, consistency-based interaction-network mining, and multi-scenario simulation within the intPLUS framework. Population, GDP, and areal-water distance layers were matched to the corresponding stage-terminal snapshots where applicable, whereas 2020 POI data were used as contemporary spatial-context proxies. From 2000 to 2020, urban industrial land (UIL) expanded from 16.63 to 46.42 km², increasing by approximately 179.1%, whereas rural settlements (RS) increased more moderately from 56.59 to 60.27 km², increasing by approximately 6.5%. The stage-wise RF and interaction-network results show that UIL and RS followed different spatial association structures, with stronger UIL self-reinforcement and stronger RS self-continuity in the later stage. Historical validation showed overall accuracy values of approximately 91% and Kappa values around 0.80, but FoM values remained relatively low, ranging from 0.098 to 0.176. Class-specific mapping accuracy was higher for RS (81.90–82.37%) than for UIL (55.20–66.93%), indicating a weaker performance in locating UIL change. Therefore, the 2035 simulations should be interpreted as parameter-conditioned regulatory comparisons rather than deterministic pixel-level forecasts. The scenario results indicate that the conservation-oriented limited growth was associated with the restricted UIL expansion and better cropland retention under the prescribed demand and constraint settings, while the RS reduction occurred only under explicit village-consolidation and construction-land quota reallocation assumptions. By distinguishing UIL and RS, this study provides differentiated regulation-oriented evidence for sustainable land-use governance in historical and cultural cities. Full article

Environmental disasters demand structured monitoring systems capable of linking ecological responses to adaptive governance. This study proposes an integrated indicator framework designed to support ecosystem preservation and environmental risk mitigation following large-scale contamination events. The proposed framework combines multi-source environmental data, intrinsic risk classification, multivariate statistical validation, and a dashboard-based decision-support architecture. When the model was applied to Restinga ecosystems impacted by mining tailings deposition, the results revealed significant spatial heterogeneity between the monitoring stations, with ~33% of sites classified under high or critical ecological risk during at least one monitoring period. Of the metals evaluated, 46.15% were above the reference levels, while for biological response indicators such as primary productivity, a 23.53% reduction in danger alerts was observed in 2019 across the evaluated sites when comparing the rainy and dry seasons. The composite “Danger Alert” indicator was triggered in all sampling campaigns during the evaluated period, demonstrating persistent ecological pressure throughout seasonal cycles. Sensitivity analyses confirmed the robustness of the risk classifications under alternative baseline and aggregation scenarios, and an uncertainty assessment indicated stable trends across temporal variability ranges. The proposed framework enhances the interpretability of complex environmental datasets by structuring inferential ecological associations between environmental pressures and biological responses, which can then be translated into actionable governance outputs. Beyond the case study, the architecture is structurally transferable to other ecosystems, provided that ecological indicators and thresholds are contextually recalibrated. The proposed approach contributes to sustainability-oriented environmental governance by integrating statistical validation, adaptive risk thresholds, and decision-support visualization within a unified monitoring system. Full article

With deep coal mining in China, high in situ stress frequently causes severe floor deformation, bolt-cable support failure, and excessive floor heave, which critically threaten mine safety. In this study, we use physical experiments, numerical simulation, and theoretical analysis to explore how hydraulic fractures with different azimuth angles affect stress transfer in roadways under floor dynamic pressure. Prefabricated fractures simulate weak planes induced by hydraulic fracturing. Uniaxial compression tests and PFC2D fluid–solid coupling simulations analyze mechanical properties, failure modes, acoustic emission behavior, and stress distribution. Results show that fracture azimuth significantly controls rock damage and failure modes. As the angle increases from 0° to 90°, failure changes from gradual degradation to sudden instability. Peak strength first decreases then increases, reaching the minimum at 22.5°, while roadway damage is minimal at 45°. Small-angle fractures lead to shear failure with clear precursors, and large-angle fractures cause sudden tensile failure. Hydraulic fractures form directional stress-relief zones and enable effective stress transfer and pressure relief. The results support parameter optimization of hydraulic fracturing and stability control for deep roadways under floor dynamic pressure. Full article

Pipeline valves play a crucial role in oil and gas exploration, production, transportation, and storage, and a systematic understanding of patent technologies in this field can help identify innovation trends and formulate research and development (R&D) strategies. This study collected more than 5000 pipeline-valve-related patents worldwide from 2006 to 2025, including 2292 invention patents, and adopted a progressive patent analytics approach integrating statistical analysis, network analysis, text mining, and high-value invention patent analysis. The results show that innovation activity in this field has remained active over the past two decades, especially since 2016, when the number of patent publications exceeded 300 in almost every year. China, Russia, the United States, South Korea, and Canada are the major sources of patent activity, with Chinese enterprises and universities making important contributions in terms of patent quantity. However, the analysis of high-value invention patents indicates that representative patents from the United States, Canada, and Russia also have a strong influence. Core innovation directions cover multiple pipeline valve applications in oil and gas extraction, transportation, and storage, with valve control systems and mechanical structures constituting the dominant technologies. The ten identified technological themes and their evolution show that technological innovation in this field has gradually expanded from mechanical improvements in traditional valve bodies, sealing components, and pressure relief devices to diversified directions such as wellhead control, intelligentization, and low-carbon development. The analysis of high-value invention patents further confirms this trend, indicating that pipeline valve technology is being reshaped from a relatively mature mechanical technology field into an integrated technological system that combines mechanical reliability, intelligent control, and other dimensions. Full article

The karst region of Southwest China represents a typical high geological background area characterized by extensive carbonate bedrock and secondary enrichment of heavy metals, particularly cadmium (Cd), in residual soils. Under natural carbonate-buffered conditions, Cd is largely immobilized through mineral associations and surface complexation, resulting in elevated total concentrations but low bioavailability. However, intensified anthropogenic pressures–including acid deposition, mining, excessive fertilization, and improper irrigation—have accelerated soil acidification in paddy fields. Acidification disrupts carbonate geochemical equilibria, weakens buffering capacity, and drives Cd speciation shifts toward more labile forms, thereby enhancing plant uptake and accumulation. These effects are especially pronounced in paddy fields and other systems subject to hydrological and redox fluctuations that further increase Cd mobility. To evaluate these coupled geogenic and anthropogenic controls, we conducted a structured literature synthesis (2016–2026) focusing on peer-reviewed studies of Cd dynamics in Southwestern China’s karst agroecosystems. We critically examine (i) the formation mechanisms and spatial heterogeneity of high-background Cd, (ii) acidification-driven speciation transformation and soil–crop transfer pathways, and (iii) in situ remediation and precision risk assessment strategies. By integrating geological inheritance, geochemical activation, and ecological risk perspectives, this review proposes a conceptual framework to support soil quality standard refinement and adaptive risk management in high-background karst regions. Full article

Gases are prone to accumulating in mines. Untimely gas drainage can easily trigger gas outbursts, which may further lead to gas explosions, directly endangering personnel lives and mine safety. Therefore, gas control during gob-side entry driving (roadway excavation adjacent to the goaf) in high-gas mines is crucial to ensuring successful and safe mining and excavation. The 110505 track haulage gateway is a typical high-gas gob-side driving gateway. The measured maximum gas content of the lower No.5 coal seam is 6.0289 m³/t. At present, without a scientific basis for optimizing core parameters, such as the spacing and diameter of gas drainage boreholes, gas drainage is incomplete, and triangular gas pressure zones are likely to form between boreholes. As a result, the risk of gas accumulation is high. This not only exacerbates the danger of unpredicted gas outbursts but also seriously hinders the rapid excavation of the gateway and the progress of mining and further excavation. Based on a mechanical framework coupling coal seam and methane migration, and focusing on the relationships between factors such as borehole spacing, borehole aperture, methane drainage duration, and overall gas drainage efficiency, a model incorporating dual pore distribution and unified permeability characteristics was constructed. Numerical modeling was performed using the COMSOL Multiphysics platform to examine the influences of different borehole spacings and apertures on underground gas drainage in coal seams. The results indicate that reducing borehole spacing contributes to a more pronounced decline in gas pressure and a lower peak pressure between neighboring boreholes. When an interval spacing of 0.3 m was adopted for the drilling layout arrangement, the peak gaseous potential within the surrounding rock matrix dropped to 0.48 MPa following continuous drainage over a duration of 20 days, a reduction of 44%, and there was no obvious triangular zone of pressure. In contrast, borehole diameter had a minor effect on gas drainage efficiency, and the maximum gas pressure after 20 days was less than 0.52 MPa under different borehole diameters. This work establishes a theoretical foundation and offers practical guidance for high-efficiency gas drainage during gob-side entry driving, which is of vital importance for achieving safe and rapid excavation in high-gas mines. Full article