Enhancing the electrochemical reduction-recovery of trace-level gold(I) in thiosulfate media is essential for advancing environmentally friendly, cyanide-free hydrometallurgical technologies. In this work, walnut shell charcoal (WSC) was modified using various ferric compounds to enhance its performance as an electrode. Ferric modification led to stable surface coating which significantly improved electrical conductivity and electrochemical behavior by increasing the specific capacitance and reducing the charge transfer resistance during gold(I) recovery. Among the different ferric precursors tested, ferric sulfate (Fe₂(SO₄)₃) modification exhibited the most outstanding performance, increasing the reduction capacity from 36.52 mg/g (pristine WSC) to 97.70 mg/g, a 2.67-fold enhancement. Under optimized electrochemical conditions, this modified electrode achieved a 95.72% recovery for trace gold(I) (5 mg/L), significantly outperforming electrodes modified with FeCl₃. Systematic experiments and material characterizations revealed that Fe₂(SO₄)₃ modification led to the formation of surface-bound sulfate groups and oxygen-rich functional sites, which enhance the adsorption affinity toward gold species and facilitated pre-concentration near active centers. Moreover, density functional theory (DFT) simulations confirmed strong interactions between sulfur-derived oxygen atoms and gold(I), contributing to the improved recovery. Chloride from ferric chloride also showed ability to coordinate with oxygen atoms, contributing to a moderate recovery. These results collectively highlight the importance of ferric source selection in optimizing carbon-based electrodes for noble metal recovery, providing a promising strategy for sustainable hydrometallurgical processes.

Understanding the mechanisms and mitigation strategies for disturbance-induced rockbursts is essential for ensuring safety in deep rock engineering. To evaluate the effectiveness of drilling pressure relief, uniaxial compression tests were conducted on high-stress, cavity-containing sandstone under low-frequency disturbance loading at various amplitudes. Progressive damage was monitored using acoustic emission and digital image correlation. The threshold disturbance amplitude required to trigger dynamic failure was 25% of uniaxial compressive strength, which was significantly higher than that of intact sandstone. During the stable-damage stage, damage accumulated primarily through small-scale tensile fracturing, whereas large-scale shear fractures developed at later stages, initiating and propagating macrocracks that signalled impending structural instability. The energy-storage limit of cavity-containing sandstone was found to be independent of the loading path. The input energy during disturbance was stored as elastic strain energy and rapidly exceeded its storage limit, thereby driving crack propagation and rockburst failure. An energy pre-release ratio (EPR) was introduced to quantify the premature release of elastic strain energy induced by cavity instability. For all disturbance amplitudes, the EPR exceeded 45%, demonstrating that the cavity effectively mitigates disturbance-induced rockbursts. The results of this study provide a theoretical basis for evaluating the effectiveness of drilling pressure relief in mitigating disturbance-induced rockbursts.

To effectively control the large deformation of the surrounding rock under complex conditions, it is often necessary to apply prestress to anchor cables. However, due to the influence of surrounding rock deformation, mining disturbance, and strong impact, anchor cables are often in a dynamic and static coupling stress state. Therefore, it is crucial to study the dynamic and static coupling mechanical characteristics of anchor cables. Based on this, the self-developed dynamic and static coupling test equipment is developed. The dynamic and static coupling mechanical test of anchor cables is conducted. Test results indicate that the energy absorption for anchor cables under the initial load of 350 kN decreased by 69.8% compared to the condition without initial load, and the energy absorption efficiency increased by 6.6 times. The increase of initial load can improve its energy absorption efficiency, but it can also lead to a decrease in its energy absorption. The energy absorption and energy absorption efficiency shows a bilinear variation law with the increase of initial load. On this basis, the energy absorption calculation formula and the support design model of the anchor cable are established. It provides new ideas for the safety control of dynamic disasters in deep engineering.

Accurate mechanical parameters are crucial for deep rock engineering. Traditional two-dimensional strength models often fail to reflect the complex three-dimensional mechanical properties of deep rock mass. This study proposes an elastoplastic constitutive model based on the smooth GZZ strength criterion, incorporating a non-associated flow rule to account for rock dilatancy. The model was numerically implemented and validated against theoretical and experimental results. Applied to a deep-buried tunnel, it determined the scale-dependent uniaxial compressive strength (UCS) and Geological Strength Index (GSI) of the rock mass. Numerical experiments revealed a transition from brittle to ductile failure with increasing confining pressure. Both the strength and GSI increase nonlinearly with confining pressure. The impacts of the plastic flow rule and rock matrix strength criterion on these parameters were quantitatively analyzed. At high confining pressures, neglecting dilatancy leads to their overestimation. Compared to the proposed model, using the Hoek-Brown criterion for the rock matrix fails to capture continuous hardening and yields conservative strength predictions under high confinement. Overall, the proposed model offers an improved tool for predicting rock mass strength and GSI under high confinement, with direct implications for the design and stability assessment of deep underground excavations.

Drilling and blasting in foliated rock masses widely occur in tunnel engineering and mining operations. However, the effects of schistosity on rock fragmentation and energy dissipation behavior remain insufficiently understood. This study first conducts schist blast testing to investigate the influences of schistosity characteristics on rock fragmentation pattern and fragment size distribution, utilizing image processing to analyze the variations in fragment shape and fracture energy dissipation. Finite element models of schist blasting are then developed to simulate the successive process of detonation-induced stress propagation, crack network evolution and rock fragmentation. Blast testing and following image analysis reveal that schist fragments exhibit pronounced foliated features, with many fragments displaying platy shapes, and the average aspect ratio of rock fragments is primarily concentrated in the range of 0.5–0.7. When the schistosity is perpendicular to borehole and the proportion of harder rock matrix increases, the mean fragment size increases, the uniformity of fragment size distribution reduces, and thus the rock fragmentation performs worse. The mean aspect ratio of fragments increases with rounder rock fragments. Compared to blasting with schistosity perpendicular to borehole, blasting with schistosity parallel to borehole consumes more explosive energy, with an average increase of 27.28% in blast testing. Numerical simulations demonstrate that during the propagation of stress waves in schist, cyclic reflections occur at schistosity planes, mainly resulting in fracture and breakage in the weaker rock matrix. This leads to blast-induced cracks growing parallel to schistosity planes at intervals, forming flattened rock fragments with relatively small aspect ratios. The current findings suggest that schistosity perpendicular and parallel to borehole is unfavorable and favorable for rock fragmentation, respectively. Thus, in blasting engineering practice with simple layered structures, aligning the borehole with the dominant schistosity direction is an effective strategy for optimizing rock fragmentation performance, particularly when the harder rock matrix constitutes a large proportion.

To investigate the leakage mechanism of the sealing plug area in compressed air energy storage (CAES) caverns under various conditions, the leakage evolution characteristics of the simulated samples were systematically studied via a self-developed triaxial seepage testing system. Combined with CT scanning, the development and propagation mechanisms of internal defects were elucidated. The results indicate that the leakage index is significantly positively correlated with the peak air pressure and injection rate but negatively correlated with the confining pressure. Leakage behavior during the charging phase is governed primarily by the peak pressure and injection rate, whereas that during the storage phase is predominantly controlled by the pressure magnitude. A distinct time lag, dominated by peak pressure, was identified between the leakage index and pressure characteristic points. The average peak leakage rate exhibited a "decreasing-then-increasing” trend, transitioning from an initial value of 9.3289 to 7.3267 cm³/s and then rebounding to 8.8093 cm³/s. The cyclic process enhanced the connectivity of the pore-fracture network; fracture coalescence reduced the number of large pores (> 0.9 mm) but increased the total pore count. This research provides valuable insights for evaluating the sealing performance and rock concrete interface seepage of artificial CAES caverns.

Understanding the dynamic behavior of rocks under confining conditions is essential for elucidating the failure mechanisms of deep rock masses. In this study, triaxial compression tests on granite were conducted at intermediate strain rates to systematically investigate the effects of confining pressure and strain rate on rock strength and deformation behavior. The roles of these factors in energy dissipation and damage evolution were clarified, and a stage-dependent damage constitutive model based on dissipated energy was established. The results show that both confining pressure and strain rate significantly enhance rock strength and deformation resistance, with confining pressure playing a more dominant role. The proportion of dissipated energy exhibits an overall trend of initial decrease followed by subsequent increase, corresponding to the transition from crack compaction and closure to crack development and propagation. A two-stage damage model incorporating initial damage recovery is proposed and demonstrates improved predictive capability compared with conventional models. Confining pressure suppresses damage development, whereas strain rate promotes it. In addition, higher confining pressure and strain rate increase the occurrence of transgranular cracking, revealing the mechanisms underlying enhanced energy dissipation and smoother fracture surfaces.

The prospective mining of deep-sea polymetallic nodules, a source of strategic critical metals, could cause irreversible damage to fragile deep-sea ecosystems, sparking global scientific, political, and ethical controversies. Consequently, establishing a scientific, credible, and efficient in-situ environmental monitoring system is a core prerequisite for achieving sustainable resource development and effective environmental regulation. This paper reviews the latest progress in in-situ environmental monitoring for polymetallic nodule mining (PNM). First, integrating future commercial mining workflows with current pilot-scale engineering practices, this paper outlines the multi-source environmental disturbances of PNM. The review then analyses impact mechanisms and monitoring strategies for five key areas: physical oceanography, marine chemistry, geology, marine biology, and sediment plumes. Finally, by assessing typical international monitoring campaigns, the paper distils key scientific findings and identifies core challenges. In-situ monitoring indicates that under the specific environmental conditions of PNM areas, mining plumes primarily propagate as near-bottom gravity currents, and that damage to benthic habitats can persist for decades. However, significant technical bottlenecks and scientific uncertainties remain in quantifying micro-scale processes, conducting continuous long-term observation of ecological recovery, and enabling real-time fusion of multi-platform data.

This study investigates the influence of porosity on the Mode I fracture behavior of granite and the predictability of catastrophic failure. Pores are defined in a broad sense to include intrinsic pores and microcrack-type defect structures that collectively contribute to rock heterogeneity. Granite specimens were heat-treated at ambient temperature, 450 °C, and 900 °C to induce porosity variations, which were quantified using Nuclear Magnetic Resonance (NMR). Three-point bending (TPB) tests were conducted with real-time monitoring using Digital Image Correlation (DIC) and Acoustic Emission (AE). The results show that increasing porosity significantly reduces rock strength, fracture toughness, and fracture energy. As porosity increases from 0.68% to 1.33%, the crack initiation and unstable fracture toughness decrease by 94.6% and 87.0%, while crack mouth opening displacement (CMOD), fracture process zone (FPZ) size, and fracture surface roughness increase. AE results indicate that low-porosity specimens exhibit few high-energy events typical of abrupt brittle fracture, whereas high-porosity specimens generate numerous low-energy events associated with distributed microcrack coalescence. Time-Reversed Omori Law (TROL) analysis shows that higher porosity leads to predicted failure times closer to actual collapse, indicating improved predictability. These results demonstrate that pore-related heterogeneity plays a key role in regulating fracture behavior and catastrophic failure predictability.

Understanding the microscopic reaction mechanisms of high-temperature smoldering combustion (SC) is essential for efficient fire management. This study adopted high-temperature in-situ FTIR and DSC techniques to investigate the real-time evolution laws of 11 typical functional groups and their correlation with heat release during SC of long-flame coal. The reaction kinetics mechanism of typical functional groups under time-scale effects (TSE) was revealed. The results demonstrated that reduced oxygen level (100%–21%, 16%–1%) mainly affects coal combustion performance by restricting or delaying the rapid consumption of typical functional groups. Heat release restriction follows a two-stage linear model, with sensitivity to this limitation being about 21 times higher from 21%–3% to 3%–1% oxygen level. Aliphatic hydrocarbons at low temperatures and carboxyl/carbonyl groups at high temperatures exhibit the highest correlation degree with heat release. Aliphatic hydrocarbons determine the early-stage ignition capability of coal, while aromatic hydrocarbons (benzene rings) govern the burnout capability, and oxygen-containing functional groups dictate the burnout characteristics and maximum heat release intensity. The sensitivity to TSE follows the sequence: benzene rings ≈ oxygen-containing functional groups > aliphatic hydrocarbons > hydroxyl groups, and oxygen-limited conditions > normal oxygen conditions. Kinetic studies confirm that the activation energies under oxygen limited conditions (3%, 50–100 kJ/mol) are lower than those under normal oxygen conditions (140–200 kJ/mol). An oxygen level of 3% can be adopted as a critical safety threshold for the on site sealing management of fire zones.

Pyrrhotite, a gangue mineral involved in the separation of polymetallic sulfide ore, is prone to oxidation, which deteriorates the pulp environment and reduces flotation efficiency. In this study, the oxidation-corrosion characteristics of pyrrhotite were systematically investigated, revealing the influence of pulp oxygenation and pH on surface oxidation-corrosion, as well as the mechanism. Dissolved oxygen measurements and inductively coupled plasma emission spectroscopy demonstrated that elevated pulp pH enhances the oxidation kinetics and extent. Under acidic conditions, pulp aeration intensifies Fe-dominated asymmetric corrosion, generating Fe-deficient/S-abundant surfaces. Conversely, pulp aeration is conducive to the selective corrosion of S under alkaline conditions, yielding Fe-abundant/S-deficient surfaces. X-ray photoelectron spectroscopy revealed that enhancing the aeration intensity or raising the pH promotes the oxidation of Fe and S sites and accelerates the hydroxylation of Fe site. Supported by the surface etching analysis, the hierarchical oxidation pathways were clarified: Fe(II)-S → Fe(III)-S → Fe(III)-O, S^2- → S₂^2- → S_n^2- → SO₄^2-, and Me-O → Me-OH → H₂O. Scanning electron microscopy combined with energy dispersive spectroscopy further confirmed the hierarchical oxidation and asymmetric corrosion characteristics, with corrosion becoming more pronounced as oxidation progresses. These findings elucidate the transformation of surface states and provide a theoretical foundation for understanding the reactivity of pyrrhotite during pretreatment and flotation.