To address the poor room-temperature plasticity of Mg alloys, this study proposes a method called twist strain-induced twin orientation regulation (TITOR). Firstly, compressive strain is applied along the extrusion direction (ED) to generate preset {10̄12} tensile twins, and then torsional deformation is introduced by screw twist extrusion (STE) to regulate the initial twin orientation. The results show that the TITOR process is dominated by continuous dynamic recrystallization (CDRX). Among them, STE will weaken the basal texture effectively. Under the continuous torsional stress, the c-axis of grains will deviate 30° in the transverse direction (TD), thereby refining the grains and promoting the movement of the basal slip obviously. By introducing controllable torsional deformation to conduct secondary regulation on the twin orientation at a large angle, the problem of poor low-temperature plasticity of Mg alloys is improved. As the increase of volume of pre-twinned, the mechanical properties and orientation regulation of Mg alloys have been improved significantly. Especially, the ultimate tensile strength (UTS) of 3% preset twins after 8 passes sample increased from 295.3 MPa to 375.5 MPa, while the fracture elongation (FE) improved from 17.23 % to 31.84 %, which increased by 27.2 % and 84.9% respectively.

The development of high-performance aluminum alloys remains a critical challenge in industrial applications, among which crossover Al-Mg-Zn alloys have recently attracted much attention due to their excellent mechanical performance. However, the slow ageing response limits their wider application as compared to 7xxx aluminum alloys. To overcome the limitation, this study proposes a synergistic strategy incorporating Cu microalloying and combined pre-treatments (pre-ageing and pre-deformation). A high number density of T-phase precursors and dislocations are formed during combined pre-treatments, which prompts the formation of strengthening precipitates during the final ageing and results in uniform precipitate distribution. The precipitate free zone (PFZ) is narrowed and precipitate-sparse zones (PSZ) are eliminated as well. Therefore, a simultaneous enhancement of ageing kinetic and mechanical properties is achieved. Such improvement is further amplified by Cu addition, which assists the nucleation of GPI zones and enhances the dislocation density during pre-treatments. The Cu-modified alloy with optimized heat treatments achieves an exceptional strength-ductility synergy (520 MPa yield strength with 11% elongation) and rapid ageing response (32 h to peak ageing). These results represent a 44% strength improvement and 94% ageing acceleration compared to the direct-aged Cu-free counterpart (338 MPa yield strength with 10% elongation, and 536 h to peak ageing). This work provides a guideline for designing high-performance crossover aluminium alloys through thermomechanical treatments.

This work focuses on the role of Cu-rich nanoprecipitates in stress corrosion cracking (SCC), elucidated by comparing the SCC mechanisms in solution-treated and aged 1000 MPa-grade high-strength steels. Research findings indicate that the precipitation of 9R-structured Cu-rich nanoprecipitates enhances the resistance to SCC by suppressing both hydrogen embrittlement (HE) and anodic dissolution (AD). X-ray photoelectron spectroscopy and electrochemical tests reveal that the corrosion products of the aged steel contain a higher content of thermodynamically stable phases (e. g.: CuFeO₂, Fe₂O₃, and Al₂O₃), which contribute to enhanced corrosion resistance and reduced AD. Fast and slow scan rate potentiodynamic polarization tests reveal that after aging treatment, the equivalent hydrogen charging current density is significantly reduced from 14.4 µA/cm² to 4.8 µA/cm², indicating a significant decrease of HE susceptibility.

Lithium-rich manganese-based cathode material Li_1.2Ni_0.2Mn_0.6O₂ (LLNMO) has attracted widespread attention because of its high theoretical capacity and low cobalt content. However, its practical application is hindered by structural instability and rapid capacity decay during cycling. In this study, we present a novel synthesis method for single-crystal LLNMO using a LiCl+KCl mixed molten salt-assisted combustion method. Three types of LLNMO samples were comparatively investigated: polycrystalline particles, single-crystal particles prepared with LiCl, and single-crystal particles prepared with the LiCl+KCl mixed molten salt. Structural and morphological analyses reveal that the mixed molten salt-assisted single-crystal particles possess larger primary grains and a more robust crystal framework. Electrochemical characterization demonstrates that these particles exhibit superior cycling stability, minimal capacity fading, and reduced voltage decay. Specifically, the initial discharge capacity reaches 247.3 mAh · g⁻¹ at 0.1 C, with the lowest impedance and minimal polarization. This work highlights the effectiveness of mixed molten salt-assisted combustion in controlling particle morphology and improving the electrochemical performance of lithium-rich layered cathodes.

Aluminum-lithium (Al-Li) alloys are widely used in marine environments because of their low density and high strength, but they are susceptible to corrosion during service. In this work, a durable and multifunctional PFDTES@ZnO/PU superhydrophobic coating was fabricated on an Al-Li alloy substrate by a simple and economical spraying method using PFDTES-modified ZnO nanoparticles and polyurethane as the binder. The surface morphology, chemical composition, wettability, corrosion resistance, durability, and multifunctional properties of the coating were systematically investigated. The prepared coating showed a water contact angle of 160.07° ± 0.8° and a sliding angle of 3.4° ± 0.6°. Electrochemical tests indicated that, compared with the bare substrate, the coating exhibited an impedance modulus increased by about two orders of magnitude, a positive shift in corrosion potential of 215 mV, and a corrosion inhibition efficiency of 99.7%. After a 10 d NSS test, 15 d semi-immersion in 3.5 wt% NaCl solution, 7 d UV irradiation and 7 d outdoor exposure, the coating still maintained stable superhydrophobicity and structural integrity. In addition, the coating exhibited excellent self-cleaning, anti-pollution, drag-reduction, anti-icing, and antibacterial properties. These results demonstrate that the PFDTES@ZnO/PU coating can effectively integrate corrosion protection, durability, and multifunctionality, showing promising potential for marine applications of Al-Li alloys.

Invar alloys are extensively used in aerospace, mold manufacturing, and precision structural applications due to low coefficient of thermal expansion. However, developing Invar alloys with high hardness, strength, and wear resistance is challenging. Surface grain refinement is an efficient method to meet this challenge while maintaining the precision structure of the mold. In this study, ultrafine-grained surfaces of Invar alloy are prepared via ultrasonic surface rolling process (USRP) and laser heat treatment-assisted USRP (LHT-USRP). The grain refinement evolution mechanism and wear resistance of USRP and LHT-USRP are investigated. The results show that submicron ultrafine grains can be produced on the surface of Invar alloy via USRP, driven by dislocation motion and the stacking fault mechanism. LHT before USRP increases the proportion of low angle grain boundaries, accelerates grain refinement, and deepens the plastic deformation layer by 18%. Compared to untreated samples, the surface hardness of USRP- and LHT-USRP-treated samples increases by 48.8% and 52.2%, while the wear rate decreases by 26.5% and 58.8%, respectively. These improvements are attributed to increased surface hardness, grain refinement, and residual compressive stress, which enhance surface performance and friction-wear properties. This study highlights the potential of LHT-USRP in enhancing the surface performance of Invar alloys.

The internal stress significantly affects the flatness of electrodeposits. Excessive internal stress even induces the delamination of electroformed components from the substrate, particularly on mirror-finished silicon wafers. In this study, precision nickel mold inserts with a high flatness were electroformed via internal stress reduction and interfacial bonding enhancement. Firstly, the temperature and pH of electrolytes were optimized to reduce internal stress. Dislocation density and hydrogen evolution were characterized to explain the influence of temperature and pH on the internal stress raised from nickel sulfamate-based electrolytes. In addition, various interlayers (Ni, Cr and Ti) with different thicknesses were provided to enhance the interfacial bonding strength between deposited nickel and silicon wafers. Compared to interlayer-free samples, a 20 nm thick titanium interlayer significantly increased the critical load from 5.7 N to 43.27 N. The presence of a titanium layer dramatically decreased the deformation of nickel deposits. To balance the internal stress and deposition rate, a segmented electroforming process consisting of initial low current deposition (1 A/dm²) and subsequent high current deposition (5 A/dm²) was provided. Combined with the titanium interlayer and optimized processing parameters, nickel mold inserts with a high flatness and precise micro features were successfully electroformed.

Leveraging the high strength-to-weight ratio of composite materials for lightweight robot design, this study presents a cable-driven underactuated hyper-redundant robot with a metamaterial-inspired architecture, achieving performance in complex and constrained environments. By adopting a modular flexible structure, coupled with a soft-mechanism integration approach, we design a 10-joint hyper-redundant robotic arm composed of three modules: head, middle, and tail. The rigid arm is fabricated from carbon fiber–reinforced polyamide-6 using fused deposition modeling. Universal joints in the middle segment facilitate three-dimensional deflection, while single-axis joints in the head and tail segments provide axial motion stability. Underactuated cable coupling allows coordinated multi-degree-of-freedom motion with fewer drive units. Structural modularization and joint-level constraint design reduce volume and mass while improving spatial flexibility. The soft-tentacle mechanism, fabricated via direct ink writing (DIW), allows compliant deformation and adaptive grasping through pneumatic actuation. The experimental results show that the robot exhibits high flexibility and environmental adaptability during confined-space manipulation, with a maximum end-effector speed of approximately 90 mm/s, a positioning repeatability of less than 3 mm, and a maximum payload of about 300 g. Notably, this integrated design maintains motion stability comparable to fully actuated hyper-redundant robots, while reducing system complexity through underactuation and modular construction.

Formic acid dehydrogenation offers an efficient method to accomplish hydrogen storage and supply because of its liquid state and high volumetric content of hydrogen at ambient conditions. In this study, we developed and tested h-BN supported Pd-Fe, Pd-Ni, Pd-Co, and Pd-Cu catalysts for formic acid dehydrogenation. Among them, the Pd-Cu/h-BN catalyst synthesized via wet impregnation demonstrates an average productivity of 0.208 mmol/min at 160 °C under catalyst weight at 0.300 g and formic acid feeding rate at 0.008 mL/min, an 84.1% improvement compared to Pd-based catalyst, with minimal CO formation (1.3% CO selectivity at 160 °). Characterizations such as XRD, TEM, and DRIFTS-MS were conducted, confirming PdCu(111) alloy formation with homogeneous metal dispersion. Long-term stability tests showed that the Pd-Cu/h-BN catalyst maintained relatively stable H₂ productivity of 0.210 mmol/min over 2000 min. Density functional theory calculations confirm the superiorities of Pd-Cu alloy compared with Pd/h-BN and Cu/h-BN. These findings underscore potential of Pd-Cu/h-BN as an activated and robust material for hydrogen generation.

This research work reports the synthesis and characterizations of ZnO, MnO₂ and MnO₂@ZnO nanocomposites by using Azadirachta Indica as well as Orange Peel (Citrus Sinensis) extracts. The synthesized nanomaterials were used to treat wastewater, containing Methylene Blue dye as well as used as a potential Energy storage electrode material. Several characterizations confirmed the characteristic properties of synthesized nanocomposites, and among them, OP-MnO₂@ZnO showed better morphology, reduced bandgap and recombination rate, and enhanced electrochemical as well as photocatalytic properties. OP-MnO₂@ZnO showed 97.72% degradation of MB dye and 883.63 F/g Csp that are much greater than other synthesized materials. The findings have proved the proficiency of OP-MnO₂@ZnO as a synergistic candidate material for various applications.

Red mud is a high-alkalinity solid waste generated during alumina production, and its large-scale utilization remains a thorny problem worldwide. Based on its physical and chemical properties as well as environmental impact, this paper systematically reviews the latest application and research progress of red mud in construction materials such as cements, lightweight aggregates, ceramics, bricks, concretes, and geopolymers. The high alkalinity and compositional variability of red mud remain critical barriers to its direct use in construction, often causing efflorescence, poor durability, and environmental risks. To overcome these challenges, alkali activation and synergistic utilization with other solid wastes have emerged as promising breakthrough directions, enabling enhanced reactivity, long-term stability, and effective immobilization of alkalis and heavy metals. The properties and preparation process of various red mud-based construction materials were summarized, and the advantages and disadvantages of different preparation methods were also analyzed. Finally, beneficial suggestions for future research were put forward, and the key directions of future study on red mud application in construction materials were proposed. This review provides a detailed understanding of the application of red mud in the construction field and is expected to inspire researchers to participate in future studies.

With the rapid development of new energy vehicles and renewable energy industries, the demand for lithium resources has increased significantly, and the resulting large amount of solid waste from lithium extraction poses a serious threat to the environment. For zero-waste utilization of lithium extraction clay slag, this study employed an acid leaching-polymerization-aging process to prepare polyaluminium chloride for water treatment and silica-enriched ingredient for cement production. Optimization of preparation conditions yielded liquid polyaluminium chloride (PAC) containing 10.06% Al₂O₃ with 59.16% basicity, which complies with the national standards. Meanwhile, the illite residue derived from the Al leaching process, with a silica modulus of 2.4, satisfies the requirement for clay raw materials in cement production. In coagulation tests using simulated wastewater, the synthesized PAC demonstrated removal efficiencies of 96.92% for turbidity and 97.32% for chemical oxygen demand (COD) in humic acid wastewater, and 99.24% for turbidity and 92.21% for COD in methyl orange wastewater, outperforming a commercially available polyaluminium chloride. These results demonstrate that the proposed strategy facilitates the complete utilization of lithium extraction slag, thereby promoting sustainable development in the lithium industry.

Efficient and environmental friendly separation of chalcopyrite and molybdenite has always been a difficult problem in mineral processing. Therefore, a new strategy using mercaptosuccinic acid (MSA) as chalcopyrite depressant has been proposed in this study, based on the heterogeneous surface regulation by copper ions on mineral surfaces. The MSA dosage required for chalcopyrite-molybdenite separation reduced significantly after heterogeneous surface regulation of copper ions. Molybdenite concentrate with Mo grade of 53.97% and recovery of 89.81% can be obtained with less MSA in mixed-mineral flotation. TOC, XPS and ToF-SIMS results demonstrated that the heterogeneous surface regulation of copper ions significantly increased the adsorption capacity of MSA on chalcopyrite surface, while the adsorption of MSA on the surface of molybdenite was negligible. XPS, ToF-SIMS and DFT calculations indicated that MSA interacts with the copper sites on the chalcopyrite surface through the carboxyl group in its molecule, and the interaction is attributed to the p orbital of the oxygen atom and the d orbital of the copper atom. The findings provide valuable insights into the enhancement of organic depressant performance via metallic ion regulation at mineral surfaces, which holds significant reference implications for efficient separation and environmental protection in mineral processing.

High wall shear stress and uneven gas-liquid mixing constrain anode slime side-blown smelting. A multi-fluid VOF model is developed to quantify the response of bath agitation and wall shear stress to lance inclination, bath depth, and injection velocity. Melt viscosity (0.2 Pa·s) was measured at 1573.15 K, and a 580.02 K inlet temperature was derived from conjugate heat transfer analysis. Simulations were performed for inclinations of −30° to +30° , depths of 1200–1800 mm, and velocities of 300−450 m/s. Results show that a −15° inclination opposes buoyancy, lengthening the plume path and thickening the near-wall protective film from 8 mm (at −30°) to 40 mm, avoiding direct sidewall impingement. Increasing bath depth to 1800 mm enhances melt velocity, but the protective film thins to 22.5 mm at 1400 mm, shifting high-shear zones upward. Beyond 400 m/s, jet inertia forms a central gas column; increasing velocity from 400 to 450 m/s raises melt velocity by only 11.6% while lance-tip shear stress jumps 18%. Conclusively, a shallow downward inclination (−15°) with velocities £400 m/s optimizes agitation while mitigating localized high shear.

In-situ condition-preserved coring of lunar rock samples is crucial for lunar resource exploration and research station construction. A reliable understanding of the basic physical and mechanical properties of lunar rocks under the Moon’s extreme temperature conditions is a prerequisite for these efforts. Brazilian tests were conducted on lunar rock simulant under simulated lunar temperatures (−120 to 200 °C) to investigate the relationship between tensile strength and in-situ temperature. The results indicate that tensile strength, peak tensile strain, and the duration to peak load all decrease nonlinearly with increasing temperature. Micro-morphological observations show that the tensile fracture surfaces are complex, with high-temperature specimens exhibiting rougher surfaces and more pronounced fracture cracks than low-temperature specimens. The fracture morphology is dominated by intergranular cracking, together with small-scale cleavage rivers, cleavage steps, and a small plane of analogous cleavage, as further supported by box fractal dimension analysis of the fracture surfaces. Additionally, matrix tensile failure is identified as the dominant failure mode in Brazilian tests under simulated lunar temperature conditions. These findings provide a scientific basis and theoretical reference for in-situ condition-preserved deep coring of lunar rocks in the Moon’s extreme thermal environment.

In deep mining engineering, coal and rock dynamic disasters occur frequently, which have gradually become a significant threat to coal mining safety. High-toughness cementitious materials are required to serve as energy-absorbing and supporting structures. This paper investigated the synergistic effects of lithium slag (LS) and polyvinyl alcohol (PVA) fibers of different sizes (bars/powder) on mechanical properties of cement concrete under dynamic compression-tensile load. Dynamic compression and tensile tests were carried out with the aid of the Split Hopkinson Pressure Bar (SHPB) system. Combined with the scanning electron microscopy (SEM) micro-morphology analysis and fractal theory calculations, the mechanical response characteristics, energy evolution mechanism, energy absorption effect, and fractal properties of the LS-PVA modified concrete under impact compression-tensile loads were investigated. The stress-strain curve was used to analyze the characteristics of materials at different stages, and the change law of peak strain and stress with LS content was determined. It was found that the synergistic effect of LS and PVA fiber bars is the best in enhancing the toughness of materials. The modified concrete had more substantial ductility and could continue to maintain its bearing capacity even after being damaged. From the perspective of energy evolution, it has been discovered that under dynamic compression, the reflected energy plays a dominant role. In contrast, during dynamic tension, the mechanism governing the dissipation of energy is distinct. Although the energy proportion trend is different, both of them have the “toughening” effect. The fractal calculation shows that adding LS and PVA fibers can improve the impact resistance of the material. The microfracture morphology reveals the LS-PVA synergistic toughening mechanism. In general, it is found that the toughening effect of PVA fiber bars is more potent than that of PVA fiber powder, and PVA fiber bars can exhibit a more substantial synergistic effect with LS. The higher the LS content, the more obvious the synergistic effect. This is mainly because LS can promote secondary hydration, form C-S-H gels, densify the matrix, while PVA fibers can bridge the cracks and redistribute the stress. Under dynamic load, the two cooperate to promote energy dissipation through gel densification, fiber pull-out fracture and interface debonding. This material can absorb energy through significant deformation when the coal mine roadway is impacted by dynamic loads, avoiding brittle failure, and alleviating the damage to the roadway structure caused by the impact. At the same time, it also has multiple advantages such as economy, environmental protection, and safety. The findings of this study provide a potential material solution for enhancing the impact resistance of tunnel linings and roadway-supported structures in deep mining engineering.

Water saturation is regarded as an effective approach to reduce rock abrasivity and mitigate cutter wear; however, the influence of water saturation on rock abrasivity and the water-weakening mechanisms remain incompletely understood. This study addresses this research gap through a series of Cerchar abrasivity index (CAI) tests using thirteen rock samples under dry and saturated conditions. Meanwhile, basic geomechanical tests of rock samples are conducted under dry and saturated states, mainly including P-wave velocity (UPV), uniaxial compressive strength (UCS), elastic modulus (E), Brittleness index (B) and Brazilian tensile strength (BTS). Next, the correlations of CAI with mechanical parameters of rocks are established using linear regression analysis. Following this, the effect of water saturation on the improvement of cutter wear and the relationships between rock properties, CAI, and the weakening effect of water saturation are systematically explored. The results indicated that CAI, UCS, BTS, B and E in saturated states show a downward trend compared with their dry states, while UPV increases when the rocks are saturated. The regression results showed that there are strong positive linear correlations between CAI and UCS, BTS and B. This study provides critical theoretical and practical implications for improving cutter wear during TBM excavation.

Underground mining in hard-rock mines is conducted under complex geological conditions, where rock masses are prone to sudden failure. To address this challenge, this study proposes an integrated early-warning framework coupling microseismic (MS) monitoring with a Convolutional Neural Network – Long Short-Term Memory (CNN-LSTM) predictor and a Cumulative Sum (CUSUM) change-point detector. The CNN-LSTM forecasts key MS parameters (seismic energy and source radius) from real-time monitoring data. A new indicator, Q—defined as the ratio of seismic energy to the cube of source radius—is introduced to quantify energy release density during rock fracturing. CUSUM tracks the evolving Q series to identify significant deviations and issue early warnings. The framework is validated using MS data from the Dongtangzi lead – zinc mine in the tectonically active Qinling Orogenic Belt, northwestern China. Results show that, compared with conventional approaches, prediction performance is markedly improved: relative to a standalone LSTM, RMSE and MAE decrease by ∼30% – 56%, while R² increases by ∼20% – 58%. The framework remains robust under complex monitoring conditions and provides warning signals up to one week in advance. Moreover, the post-blasting attenuation of Q provides quantitative insights into stress-release mechanisms and surrounding rock behavior. These findings highlight the framework’s practical applicability and theoretical significance for mining hazard prediction.

The relationship between mine seismicity (MS) and energy release due to the fracture instability of hard roof strata (HRSs) remains unclear. Theoretical models are proposed in this study to quantify the energy released by the first fracture and subsequent instability of HRSs. Based on extended voussoir beam theory and numerical simulations, the energy mechanisms of MS induced by voussoir beam instability are elucidated. The results indicate that MS mainly originates from the release of bending elastic energy, potential energy accumulated during voussoir beam rotation deformation, and impact kinetic energy after instability. Over 50% of the bending elastic energy released during the first fracture transforms into the initial kinetic energy of the voussoir beam. For a unit-width voussoir beam, the potential energy released by the instantaneous rotation crush increases with roof thickness and overlying load, typically ranging from 10⁵–10⁸ J; the impact energy from rotation or slip instability generally ranges from 10⁷–10⁹ J and increases with overlying load, roof thickness, and free space height of HRSs. A methodology for identifying MS induced by voussoir beam instability in HSRs is hereby proposed. These findings provide theoretical guidance for estimating the MS magnitude and formulating targeted mitigation strategies.

This study conducted true triaxial unloading disturbance tests and DEM numerical simulations to elucidate the damage evolution and failure modes of deep rock mass under unloading disturbance conditions. The findings indicated that the DEM-developed Model Predictive Control (MPC) method surpasses conventional servo control in stability of servo speed and boundary stress. During initial loading of intact sandstone under high true triaxial stress, stress-coupling characteristics in intermediate/minimum principal stress directions showed insensitivity to intermediate principal stress; divergence began at yield initiation. Perforated sandstone exhibited consistent failure modes across disturbance amplitudes. Increased disturbance amplitude reduced bearing strength while accelerating damage rates, with sixth-level disturbance accounting for >40% of total damage. Tensile cracks consistently predominated over shear cracks throughout loading; disturbance did not significantly alter their ratio. Secondary loading progressively increased shear crack proportion, peaking at specimen failure. Shear failure dominated perforated sandstone instability. Based on the failure characteristics and strength attenuation laws of perforated sandstone under deep disturbance, control measures for engineering sites are proposed. The research results provide a reference for the application of discrete element method in understanding complex stress paths in deep geotechnical engineering and the damage and failure mechanisms of surrounding rock in deep roadways.

Understanding brittle rock strength evolution is crucial for deep underground engineering design, particularly for projects at burial depths exceeding 1000 m. While the Cohesion Weakening and Frictional Strengthening (CWFS) model effectively predicts brittle rock failure patterns, existing CWFS models rely predominantly on empirical fitting with complex parameter determination procedures. This study conducted extensive triaxial cyclic loading-unloading tests to investigate the distribution and evolution of elastic and dissipative energy. Through theoretical derivation, the physical meanings of parameters in the logistic dissipation energy evolution model were elucidated, demonstrating that these parameters are independent of confining pressure. A rock damage variable was defined as the ratio of cumulative dissipated energy to residual dissipated energy, which is expressed as a function of normalized plastic strain. Nonlinear evolution equations for cohesion and internal friction angle were then formulated based on the principle that strength parameter evolution corresponds to energy dissipation. Building upon these evolution equations, a modified triple-shear energy criterion (MTSEC) was established. Fitting results from triaxial loading-unloading tests under various confining pressures demonstrate excellent agreement between the MTSEC and experimental data. The proposed model was implemented in FLAC^3D software and validated through field measurements of excavation-induced damage zones in the Jinping deep underground laboratory.

In this study, aiming at the temporal and spatial evolution mechanism of rockburst disaster in jointed rock mass in deep engineering, the influence of joint and roadway spacing on the process of rockburst was systematically discussed through true triaxial dynamic and static combined loading test and acoustic emission multi-parameter monitoring. The limestone samples with straight wall arch holes were taken as the object of the test. Combined with the dominant frequency distribution of acoustic emission, RA-AF fracture mode discrimination and b value evolution analysis, the coupling effect of stress path and energy release under different joint spacing was revealed. It is found that the spatial distribution of joints significantly affects the mechanical response and fracture characteristics of rockburst: close-range joints dominate tensile fracture through local tensile stress concentration, prolong energy accumulation period and aggravate rockburst intensity; long-distance joints promote shear crack propagation, accelerate damage penetration and shorten incubation time. The main frequency distribution of acoustic emission and the evolution law of b value show that the increase of joint spacing leads to the change of fracture scale from microcrack to macro shear penetration. The research results are expected to provide scientific guidance and theoretical support for the prevention and control of rockburst in deep jointed rock roadway.

In rock engineering, joints in rock masses are inevitably encountered and often act as triggers for engineering instability. Quantitative characterization of the cracking process under compressive loading is fundamental to understanding rock fracture behavior. This study employs acoustic emission (AE) monitoring to track the progressive cracking process of sandstone samples. To achieve quantitative spatiotemporal characterization, we integrate temporal analysis with nonlinear theoretical methods. A multi-parameter characterization model is subsequently established, incorporating AE activity parameters (AE event rate and AE count rate) and a spatial parameter (single-link cluster correlation length). Building on this framework, a novel method is proposed for the simultaneous determination of three key stress thresholds, including crack closure, crack initiation and crack damage stresses. The stress thresholds obtained from the proposed method are validated against those derived from conventional methods. The results indicate that the proposed multi-parameter characterization model can comprehensively capture the progressive cracking process in rocks. Strong consistency between the stress thresholds identified by the proposed and traditional methods confirms the reliability and accuracy of this quantitative approach for crack stress threshold identification.

The original structure of rock is one of the major factors influencing rock fracture, and understanding the relationship between rock structure and fracture modes is essential for elucidating the failure mechanisms of geotechnical materials. However, the characteristics of rock’s internal structure and its relationship with the ultimate fracture mode remain unclear. To investigate this relationship and identify the impact mechanisms of the original structure during rock fracture, multistage loading experiments were conducted on siltstone using acoustic imaging technology. The results show that minerals and pores within the microstructure of rocks are spatially grouped into different regions, forming new macrostructures with distinct mechanical properties, known as heterogeneity structures. These heterogeneity structures are interwoven and control the final fracture pattern and main fracture shape of rocks. Based on systems engineering principles, we propose the concept of a “rock structure system” and define its hierarchical structure: the rock monolithic layer (rock sample), the macroscopic structural body layer (heterogeneity structures), and the microscopic basic unit layer (mineral grains, microfractures, microporosity, etc.). This study bridges the gap between microscopic and macroscopic studies of rock fracture, providing significant contributions to the prediction and prevention of geological and engineering disasters.

This study investigates the aerodynamic behavior of a high-speed maglev train during tunnel entry and exit under a constant crosswind of 33.7 m/s, with operating speeds ranging from 450 km/h to 600 km/h. A key innovation of this study lies in the integrated CFD model that simultaneously simulates both the tunnel and the train within a unified computational domain, allowing detailed analysis of pressure, velocity, and vortex dynamics during transitional phases. The model was validated against experimental data from a moving model rig, demonstrating strong agreement between numerical and measured results. While prior studies have focused on conventional wheel-rail systems, limited research exists on maglev trains, which are particularly sensitive to lateral aerodynamic forces due to their narrow levitation gap and electromagnetic suspension. The results show that when train speed is 600 km/h, the maximum lift force coefficient reached 0.6368 at the tail car during tunnel entry, while the middle car exhibited a peak side force coefficient of 0.3903 at tunnel exit. These findings provide important insights into the aerodynamic risks faced by future ultra-high-speed maglev systems and underscore the need for aerodynamic optimization under extreme environmental conditions.