International Journal of Mining Science and Technology最新文献

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.

Acoustic emission (AE) localization algorithms based on homogeneous media or single-velocity are less accurate when applied to the triaxial localization experiments. To the end, a robust triaxial localization method of AE source using refraction path is proposed. Firstly, the control equation of the refraction path is established according to the sensor coordinates and arrival times. Secondly, considering the influence of time-difference-of-arrival (TDOA) errors, the residual of the governing equation is calculated to estimate the equation weight. Thirdly, the refraction points in different directions are solved using Snell’s law and orthogonal constraints. Finally, the source coordinates are iteratively solved by weighted correction terms. The feasibility and accuracy of the proposed method are verified by pencil-lead breaking experiments. The simulation results show that the new method is almost unaffected by the refraction ratio, and always holds more stable and accurate positioning performance than the traditional method under different ratios and scales of TDOA outliers.

In fractured geothermal reservoirs, the fracture networks and internal fluid flow behaviors can significantly impact the thermal performance. In this study, we proposed a non-Darcy rough  discrete fracture network (NR-DFN) model that can simultaneously consider the fracture evolution and non-Darcy flow dynamics in studying the thermo-hydro-mechanical (THM) coupling processes for heat extraction in geothermal reservoir. We further employed the model on the Habanero enhanced geothermal systems (EGS) project located in Australia. First, our findings illustrate a clear spatial-temporal variation in the thermal stress and pressure perturbations, as well as uneven spatial distribution of shear failure in 3D fracture networks. Activated shear failure is mainly concentrated in the first fracture cluster. Secondly, channeling flow have also been observed in DFNs during heat extraction and are further intensified by the expansion of fractures driven by thermal stresses. Moreover, the combined effect of non-Darcy flow and fracture evolution triggers a rapid decline in the resulting heat rate and temperature. The NR-DFN model framework and the Habanero EGS’s results illustrate the importance of both fracture evolution and non-Darcy flow on the efficiency of EGS production and have the potential to promote the development of more sustainable and efficient EGS operations for stakeholders.

The 2D limit equilibrium method is widely used for slope stability analysis. However, with the advancement of dump engineering, composite slopes often exhibit significant 3D mechanical effects. Consequently, it is of significant importance to develop an effective 3D stability calculation method for composite slopes to enhance the design and stability control of open-pit slope engineering. Using the composite slope formed by the mining stope and inner dump in Baiyinhua No. 1 and No. 2 open-pit coal mine as a case study, this research investigates the failure mode of composite slopes and establishes spatial shape equations for the sliding mass. By integrating the shear resistance and sliding force of each row of microstrip columns onto the bottom surface of the strip corresponding to the main sliding surface, a novel 2D equivalent physical and mechanical parameters analysis method for the strips on the main sliding surface of 3D sliding masses is proposed. Subsequently, a comprehensive 3D stability calculation method for composite slopes is developed, and the quantitative relationship between the coordinated development distance and its 3D stability coefficients is examined. The analysis reveals that the failure mode of the composite slope is characterized by cutting-bedding sliding, with the arc serving as the side interface and the weak layer as the bottom interface, while the destabilization mechanism primarily involves shear failure. The spatial form equation of the sliding mass comprises an ellipsoid and weak plane equation. The analysis revealed that when the coordinated development distance is 1500 m, the error rate between the 3D stability calculation result and the 2D stability calculation result of the composite slope is less than 8%, thereby verifying the proposed analytical method of equivalent physical and mechanical parameters and the 3D stability calculation method for composite slopes. Furthermore, the 3D stability coefficient of the composite slope exhibits an exponential correlation with the coordinated development distance, with the coefficient gradually decreasing as the coordinated development distance increases. These findings provide a theoretical guideline for designing similar slope shape parameters and conducting stability analysis.