International Journal of Mining Science and Technology最新文献

In order to improve rib stability, failure criteria and instability mode of a thick coal seam with inter-band rock layer are analysed in this study. A three-dimensional mechanical model is established for the rib by considering the rock layer. A safety factor is defined foy the rib, and it is observed that the safety factor exhibits a positive correlation with the thickness and strength of the inter-band rock. A calculation method for determining critical parameters of the rock layer is presented to ensure the rib stability. It is revealed that incomplete propagation of the fracture at the hard rock constitutes a fundamental prerequisite for ensuring the rib stability. The influence of the position of the inter-band rock in the coal seam on failure mechanism of the rib was thoroughly investigated by developing a series of physical models for the rib at the face area. The best position for the inter-band rock in the coal seam is at a height of 1.5 m away from the roof line, which tends to provide a good stability state for the rib. For different inter-band rock positions, two ways of controlling rib by increasing supports stiffness and flexible grouting reinforcement are proposed.

Underground hydrogen storage (UHS) and compressed air energy storage (CAES) are two viable large-scale energy storage technologies for mitigating the intermittency of wind and solar power. Therefore, it is meaningful to compare the properties of hydrogen and air with typical thermodynamic storage processes. This study employs a multi-physical coupling model to compare the operations of CAES and UHS, integrating gas thermodynamics within caverns, thermal conduction, and mechanical deformation around rock caverns. Gas thermodynamic responses are validated using additional simulations and the field test data. Temperature and pressure variations of air and hydrogen within rock caverns exhibit similarities under both adiabatic and diabatic simulation modes. Hydrogen reaches higher temperature and pressure following gas charging stage compared to air, and the ideal gas assumption may lead to overestimation of gas temperature and pressure. Unlike steel lining of CAES, the sealing layer (fibre-reinforced plastic FRP) in UHS is prone to deformation but can effectively mitigates stress in the sealing layer. In CAES, the first principal stress on the surface of the sealing layer and concrete lining is tensile stress, whereas UHS exhibits compressive stress in the same areas. Our present research can provide references for the selection of energy storage methods.

X-ray fluorescence (XRF) sensor-based ore sorting enables efficient beneficiation of heterogeneous ores, while intraparticle heterogeneity can cause significant grade detection errors, leading to misclassifications and hindering widespread technology adoption. Accurate classification models are crucial to determine if actual grade exceeds the sorting threshold using localized XRF signals. Previous studies mainly used linear regression (LR) algorithms including simple linear regression (SLR), multivariable linear regression (MLR), and multivariable linear regression with interaction (MLRI) but often fell short attaining satisfactory results. This study employed the particle swarm optimization support vector machine (PSO-SVM) algorithm for sorting porphyritic copper ore pebble. Lab-scale results showed PSO-SVM outperformed LR and raw data (RD) models and the significant interaction effects among input features was observed. Despite poor input data quality, PSO-SVM demonstrated exceptional capabilities. Lab-scale sorting achieved 93.0% accuracy, 0.24% grade increase, 84.94% recovery rate, 57.02% discard rate, and a remarkable 39.62 yuan/t net smelter return (NSR) increase compared to no sorting. These improvements were achieved by the PSO-SVM model with optimized input combinations and highest data quality (T=10, T is XRF testing times). The unsuitability of LR methods for XRF sensor-based sorting of investigated sample is illustrated. Input element selection and mineral association analysis elucidate element importance and influence mechanisms.

The relationship between support and surrounding rock is of great significance to the control of surrounding rock in mining process. In view of the fact that most of the existing numerical simulation methods construct virtual elements and stress servo control to approximately replace the hydraulic support problem, this paper establishes a new numerical model of hydraulic support with the same working characteristics as the actual hydraulic support by integrating numerical simulation software Rhino, Griddle and FLAC3D, which can realize the simulation of different working conditions. Based on this model, the influence mechanism of the supporting strength of hydraulic support on surrounding rock stress regulation and coal stability in front of the top coal caving face in extra thick coal seam were researched. Firstly, under different support intensity, the abutment pressure of the bearing coal and the coal in front of it presents the “three-stage” evolution characteristics. The influence range of support intensity is 15%–30%. Secondly, 1.5 MPa is the upper limit of impact that the support strength can have on the front coal failure area. Thirdly, within a displacement range of 2.76 m from the coal wall, a support strength of 1.5 MPa provides optimal control of the horizontal displacement of the coal.

Based on existing triaxial compression experimental data, a new empirical failure criterion with wide applicability was proposed considering hydrostatic pressure, second stress invariance, and maximum shear stress. Four fitting evaluation indicators were used to verify the consistency of the new failure criterion, and the differences with the other 6 failure criteria were discussed. The characteristics of the new failure criteria in the principal stress space were finally analyzed. The results indicate that (1) the new failure criterion exhibits strong predictive ability for triaxial experiments and has good applicability for both intact and jointed rocks; (2) the influence of hydrostatic pressure on the failure surface exhibits a non-linear trend, and different hydrostatic pressure also exhibits different distribution patterns on the deviatoric stress plane, with a distribution characteristic pattern of hexagonal snowflake-regular hexagon. The maximum shear stress has a torsional effect on the new criterion, in the three-dimensional failure surface. The parameters a and b of the rock have an impact on the failure surface morphology of the new criterion function on the offset surface.

Enhancing cavern sealing is crucial for improving the efficiency of compressed air energy storage (CAES) in hard rock formations. This study introduced a novel approach using a nano-grade organosilicon polymer (NOSP) as a sealant, coupled with an air seepage evaluation model that incorporates Knudsen diffusion. Moreover, the initial coating application methods were outlined, and the advantages of using NOSP compared to other sealing materials, particularly regarding cost and construction techniques, were also examined and discussed. Experimental results indicated a significant reduction in permeability of rock specimens coated with a 7–10 μm thick NOSP layer. Specifically, under a 0.5 MPa pulse pressure, the permeability decreased to less than 1 nD, and under a 4 MPa pulse pressure, it ranged between 4.5×10⁻⁶–5.5×10⁻⁶ mD, marking a 75%–80% decrease in granite permeability. The sealing efficacy of NOSP surpasses concrete and is comparable to rubber materials. The optimal viscosity for application lies between 95 and 105 KU, and the coating thickness should ideally range from 7 to 10 μm, applied to substrates with less than 3% porosity. This study provides new insights into air transport and sealing mechanisms at the pore level, proposing NOSP as a cost-effective and simplified solution for CAES applications.

In underground engineering with complex conditions, the bolt (cable) anchorage support system is in an environment where static and dynamic stresses coexist, under the action of geological conditions such as high stresses and strong disturbances and construction conditions such as the application of high prestress. It is essential to study the support components performance under dynamic-static coupling conditions. Based on this, a multi-functional anchorage support dynamic-static coupling performance test system (MAC system) is developed, which can achieve 7 types of testing functions, including single component performance, anchored net performance, anchored rock performance and so on. The bolt and cable mechanical tests are conducted by MAC system under different prestress levels. The results showed that compared to the non-prestress condition, the impact resistance performance of prestressed bolts (cables) is significantly reduced. In the prestress range of 50–160 kN, the maximum reduction rate of impact energy resisted by different types of bolts is 53.9%–61.5% compared to non-prestress condition. In the prestress range of 150–300 kN, the impact energy resisted by high-strength cable is reduced by 76.8%–84.6% compared to non-prestress condition. The MAC system achieves dynamic-static coupling performance test, which provide an effective means for the design of anchorage support system.

The stability control of fissured rock is difficult, especially under static and dynamic loads in deep coal mines. In this paper, the dynamic mechanical properties, strain rate evolution and energy dissipation of fissured and anchored rocks were respectively obtained by SHPB tests. It was found that bolt can provide supporting efficiency-improving effect for fissured rock against dynamic disturbance, and this effect increased quadratically with decrease in anchoring angles. Then, the energy dissipation mechanism of anchored rock was obtained by slipping model. Furthermore, bolt energy-absorbing mechanism by instantaneous tensile-shear deformation was expressed based on material mechanics, which was the larger the anchoring angle, the smaller the energy absorption, and the less the contribution to supporting efficiency improvement. On this basis, the functional relationship between energy dissipation of anchored rock and energy absorption of bolt was established. Taking the coal-gangue separation system of Longgu coal mine as an example, the optimal anchoring angle can be determined as 57.5°–67.5°. Field monitoring showed fissured rock with the optimal anchoring angle, can not only effectively control the deformation, but also fully exert the energy-absorbing and efficiency-improving effect of bolt itself. This study provides guidance to the stability control and supporting design for deep engineering under the same or similar conditions.

Rock mass quality serves as a vital index for predicting the stability and safety status of rock tunnel faces. In tunneling practice, the rock mass quality is often assessed via a combination of qualitative and quantitative parameters. However, due to the harsh on-site construction conditions, it is rather difficult to obtain some of the evaluation parameters which are essential for the rock mass quality prediction. In this study, a novel improved Swin Transformer is proposed to detect, segment, and quantify rock mass characteristic parameters such as water leakage, fractures, weak interlayers. The site experiment results demonstrate that the improved Swin Transformer achieves optimal segmentation results and achieving accuracies of 92%, 81%, and 86% for water leakage, fractures, and weak interlayers, respectively. A multi-source rock tunnel face characteristic (RTFC) dataset includes 11 parameters for predicting rock mass quality is established. Considering the limitations in predictive performance of incomplete evaluation parameters exist in this dataset, a novel tree-augmented naive Bayesian network (BN) is proposed to address the challenge of the incomplete dataset and achieved a prediction accuracy of 88%. In comparison with other commonly used Machine Learning models the proposed BN-based approach proved an improved performance on predicting the rock mass quality with the incomplete dataset. By utilizing the established BN, a further sensitivity analysis is conducted to quantitatively evaluate the importance of the various parameters, results indicate that the rock strength and fractures parameter exert the most significant influence on rock mass quality.

This study explores the effects of dynamic and static loading on rock bolt performance a key factor in maintaining the structural safety of coal mine roadways susceptible to coal bursts. Employing a house-made load frame to simulate various failure scenarios, pretension-impact-pull tests on rock bolts were conducted to scrutinize their dynamic responses under varied static load conditions and their failure traits under combined loads. The experimental results denote that with increased impact energy, maximum and average impact loads on rock bolts escalate significantly under pretension, initiating plastic deformation beyond a certain threshold. Despite minor reductions in the yield load due to impact-induced damage, pretension aids in constraining post-impact deformation rate and fluctuation degree of rock bolts. Moreover, impact-induced plastic deformation causes internal microstructure dislocation, fortifying the stiffness of the rock bolt support system. The magnitude of this fortification is directly related to the plastic deformation induced by the impact. These findings provide crucial guidance for designing rock bolt support in coal mine roadway excavation, emphasizing the necessity to consider both static and dynamic loads for improved safety and efficiency.