International Journal of Mining Science and Technology最新文献

The Voronoi grain-based breakable block model (VGBBM) based on the combined finite-discrete element method (FDEM) was proposed to explicitly characterize the failure mechanism and predict the deformation behavior of hard-rock mine pillars. The influence of the microscopic parameters on the macroscopic mechanical behavior was investigated using laboratory-scale models. The field-scale pillar models (width-to-height, W/H=1, 2 and 3) were calibrated based on the empirically predicted stress-strain curves of Creighton mine pillars. The results indicated that as the W/H ratios increased, the VGBBM effectively predicted the transition from strain-softening to pseudo-ductile behavior in pillars, and explicitly captured the separated rock slabs and the V-shaped damage zones on both sides of pillars and conjugate shear bands in core zones of pillars. The volumetric strain field revealed significant compressional deformation in core zones of pillars. While the peak strains of W/H=1 and 2 pillars were relatively consistent, there were significant differences in the strain energy storage and release mechanism. W/H was the primary factor influencing the deformation and strain energy in the pillar core. The friction coefficient of the structural plane was also an important factor affecting the pillar strength and the weakest discontinuity angle. The fracture surface was controlled by the discontinuity angle and the friction coefficient. This study demonstrated the capability of the VGBBM in predicting the strengths and deformation behavior of hard-rock pillars in deep mine design.

Underground pumped storage power plant (UPSP) is an innovative concept for space recycling of abandoned mines. Its realization requires better understanding of the dynamic performance and durability of reservoir rock. This paper conducted ultrasonic detection, split Hopkinson pressure bar (SHPB) impact, mercury intrusion porosimetry (MIP), and backscatter electron observation (BSE) tests to investigate the dynamical behaviour and microstructure of sandstone with cyclical dry-wet damage. A coupling FEM-DEM model was constructed for reappearing mesoscopic structure damage. The results show that dry-wet cycles decrease the dynamic compressive strength (DCS) with a maximum reduction of 39.40%, the elastic limit strength is reduced from 41.75 to 25.62 MPa. The sieved fragments obtain the highest crack growth rate during the 23rd dry-wet cycle with a predictable life of 25 cycles for each rock particle. The pore fractal features of the macropores and micro-meso pores show great differences between the early and late cycles, which verifies the computational statistics analysis of particle deterioration. The numerical results show that the failure patterns are governed by the strain in pre-peak stage and the shear cracks are dominant. The dry-wet cycles reduce the energy transfer efficiency and lead to the discretization of force chain and crack fields.

3D printing is widely adopted to quickly produce rock mass models with complex structures in batches, improving the consistency and repeatability of physical modeling. It is necessary to regulate the mechanical properties of 3D-printed specimens to make them proportionally similar to natural rocks. This study investigates mechanical properties of 3D-printed rock analogues prepared by furan resin-bonded silica sand particles. The mechanical property regulation of 3D-printed specimens is realized through quantifying its similarity to sandstone, so that analogous deformation characteristics and failure mode are acquired. Considering similarity conversion, uniaxial compressive strength, cohesion and stress–strain relationship curve of 3D-printed specimen are similar to those of sandstone. In the study ranges, the strength of 3D-printed specimen is positively correlated with the additive content, negatively correlated with the sand particle size, and first increases then decreases with the increase of curing temperature. The regulation scheme with optimal similarity quantification index, that is the sand type of 70/140, additive content of 2.5‰ and curing temperature of 81.6 ℃, is determined for preparing 3D-printed sandstone analogues and models. The effectiveness of mechanical property regulation is proved through uniaxial compression contrast tests. This study provides a reference for preparing rock-like specimens and engineering models using 3D printing technology.

Underground constructions often encounter water environments, where water–rock interaction can increase porosity, thereby weakening engineering rocks. Correspondingly, the failure criterion for chemically corroded rocks becomes essential in the stability analysis and design of such structures. This study enhances the applicability of the Hoek-Brown (H-B) criterion for engineering structures operating in chemically corrosive conditions by introducing a kinetic porosity-dependent instantaneous m_i (KPIM). A multiscale experimental investigation, including nuclear magnetic resonance (NMR), X-ray diffraction (XRD), scanning electron microscopy (SEM), pH and ion chromatography analysis, and triaxial compression tests, is employed to quantify pore structural changes and their linkage with the strength responses of limestone under coupled chemical-mechanical (C-M) conditions. By employing ion chromatography and NMR analysis, along with incorporating the principles of free-face dissolution theory accounting for both congruent and incongruent dissolution, a kinetic chemical corrosion model is developed. This model aims to calculate the kinetic porosity alterations within rocks exposed to varying H⁺ concentrations and durations. Subsequently, utilizing the generalized mixture rule (GMR), the kinetic porosity-dependent m_i is formulated. Evaluation of the KPIM-enhanced H-B criterion using compression test data from 5 types of rocks demonstrated a high level of consistency between the criterion and the experimental results, with a coefficient of determination greater than 0.96, a mean absolute percentage error less than 4.84%, and a root-mean-square deviation less than 5.95 MPa. Finally, the physical significance of the porosity-dependent instantaneous m_i is clarified: it serves as an indicator of a rock’s capacity to leverage the confining pressure effect.

Imaging the wave velocity field surrounding a borehole while drilling is a promising and urgently needed approach for extending the exploration range of the borehole point. This paper develops a drilling process detection (DPD) system consisting of a multifunctional sensor and a pilot geophone installed at the top of the drilling rod, geophones at the tunnel face, a laser rangefinder, and an onsite computer. A weighted adjoint-state first arrival travel time tomography method is used to invert the P-wave velocity field of rock mass while borehole drilling. A field experiment in the ongoing construction of a deep buried tunnel in southwestern China demonstrated the DPD system and the tomography method. Time-frequency analysis of typical borehole drilling detection data shows that the impact drilling source is a pulse-like seismic exploration wavelet. A velocity field of the rock mass in a triangular area defined by the borehole trajectory and geophone receiving line can be obtained. Both the borehole core and optical image validate the inverted P-wave velocity field. A numerical simulation of a checkerboard benchmark model is used to test the tomography method. The rapid convergence of the misfits and consistent agreement between the inverted and observed travel times validate the P-wave velocity imaging.

Fractal theory offers a powerful tool for the precise description and quantification of the complex pore structures in reservoir rocks, crucial for understanding the storage and migration characteristics of media within these rocks. Faced with the challenge of calculating the three-dimensional fractal dimensions of rock porosity, this study proposes an innovative computational process that directly calculates the three-dimensional fractal dimensions from a geometric perspective. By employing a composite denoising approach that integrates Fourier transform (FT) and wavelet transform (WT), coupled with multimodal pore extraction techniques such as threshold segmentation, top-hat transformation, and membrane enhancement, we successfully crafted accurate digital rock models. The improved box-counting method was then applied to analyze the voxel data of these digital rocks, accurately calculating the fractal dimensions of the rock pore distribution. Further numerical simulations of permeability experiments were conducted to explore the physical correlations between the rock pore fractal dimensions, porosity, and absolute permeability. The results reveal that rocks with higher fractal dimensions exhibit more complex pore connectivity pathways and a wider, more uneven pore distribution, suggesting that the ideal rock samples should possess lower fractal dimensions and higher effective porosity rates to achieve optimal fluid transmission properties. The methodology and conclusions of this study provide new tools and insights for the quantitative analysis of complex pores in rocks and contribute to the exploration of the fractal transport properties of media within rocks.

Accurate measurement of the evolution of rock joint void geometry is essential for comprehending the distribution characteristics of asperities responsible for shear and seepage behaviors. However, existing techniques often require specialized equipment and skilled operators, posing practical challenges. In this study, a cost-effective photogrammetric approach is proposed. Particularly, local coordinate systems are established to facilitate the alignment and precise quantification of the relative position between two halves of a rock joint. Push/pull tests are conducted on rock joints with varying roughness levels to induce different contact states. A high-precision laser scanner serves as a benchmark for evaluating the photogrammetry method. Despite certain deviations exist, the measured evolution of void geometry is generally consistent with the qualitative findings of previous studies. The photogrammetric measurements yield comparable accuracy to laser scanning, with maximum errors of 13.2% for aperture and 14.4% for void volume. Most joint matching coefficient (JMC) measurement errors are below 20%. Larger measurement errors occur primarily in highly mismatched rock joints with JMC values below 0.2, but even in cases where measurement errors exceed 80%, the maximum JMC error is only 0.0434. Thus, the proposed photogrammetric approach holds promise for widespread application in void geometry measurements in rock joints.

Recycling waste frying oils for the synthesis of flotation reagents presents a promising avenue for sustainable waste management. Moreover, it offers a cost-effective solution for crafting a specialized collector designed to efficiently remove carbonates and enhance phosphate enrichment in froth flotation processes. This study focuses on the synthesis of an anionic collector using the saponification reaction of a frying oil sample, subsequently applied to the flotation of calcite and dolomite. To elucidate the adsorption mechanisms of the frying oil collector (FrOC) and sodium oleate, a reference collector, on fluorapatite, calcite, dolomite, and quartz surfaces, comprehensive experiments were conducted, including zeta potential measurements and Fourier transform infrared spectroscopy. Results revealed diverse adsorption affinities of the molecules towards these minerals. To assess the practical performance of the collector, flotation tests were conducted using a natural phosphate ore mixture, employing a Box-Behnken experimental design. Notably, under optimized conditions (pH 9, 1000 g/t of FrOC, 3.5 min of conditioning, and 6 min of flotation), FrOC exhibited excellent performance, with calcite and dolomite recoveries exceeding 80%, while apatite recovery in the concentrate fraction remained below 10%. This work exemplifies both circular economy practices and the distinctive approach to sustainable mineral processing.