In this study, the hot deformation behavior and microstructural evolution of the GH4706 alloy under various thermal processing parameters (TPPs) were investigated through hot deformation experiments and electron backscatter diffraction (EBSD) microstructural characterization. The findings suggest that increasing hot compression temperature (T) and reducing strain rate

enhance the degree of dynamic recrystallization (DRX), significantly reducing flow stress and weakening texture intensity. Increasing strain (ε) promotes DRX, with the overall texture strength initially increasing before decreasing. During hot compression at 1000–1100 °C, discontinuous dynamic recrystallization (DDRX), continuous dynamic recrystallization (CDRX), and twin-induced dynamic recrystallization (TDRX) jointly influence texture development. Among these, DDRX plays a dominant role, with numerous DDRX grains exhibiting dispersed orientations, significantly contributing to texture weakening. The CDRX mechanism induces a limited number of randomly oriented grains within the deformed grains, and its contribution to texture weakening is enhanced with increasing ε and decreasing T. The TDRX mechanism generates DRX grains within Σ3 twin boundaries deviating from their theoretical orientation, and these grains inherit the twin orientation, exerting a limited effect on texture weakening. These findings provide a theoretical foundation for a deeper understanding of DRX behavior and texture evolution in the GH4706 during hot working.

In this paper, the multi cross-rolling and cryogenic treatment were adopted to process the AZ31 Mg alloy to study the influence of passes and cryogenic treatment on cross-rolled AZ31 Mg alloy. The tensile properties and hardness were tested. The microstructure was characterized using electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) in order to elucidate the influencing mechanism. The results indicate that the treatment method can significantly improve the mechanical properties of AZ31 Mg alloy. The 3-pass sample processed by cryogenic treatment shows the highest strength (351 MPa) and has the highest hardness (76.1HV) and best hardness uniformity (standard deviation=0.9HV). The 2-pass sample has the highest ductility among all the samples but poor hardness evenness. The strengthening mechanism of 3-pass sample can be attributed to the fine grains, bimodal structure, high dislocation density, and precipitation strengthening. Due to repeated heat preservation of 4-pass and 5-pass, their comprehensive performances decrease.

This study investigates the effects of varying Sc content on phase composition, corrosion resistance and passive film characteristic of Al_1.2CoCrFeNiSc_x (x=0, 0.1, 0.2, 0.3) high-entropy alloys in 0.5 mol/L H₂SO₄ solution. The addition of Sc causes the alloys to form a Laves phase which is a (Ni, Co)₂Sc intermetallic compound with face centred cubic (FCC) structure and lattice parameter of 0.695 nm. During the potentiodynamic polarization process, Laves phase is severely corroded due to its large grain orientation spread value and high electrochemical activity. Sc deteriorates the corrosion resistance of the alloy primarily by significantly accelerating the corrosion rate rather than altering the corrosion tendency. Al_1.2CoCrFeNiSc_x alloys exhibit poorer corrosion resistance in 0.5 mol/L H₂SO₄ than in 3.5 wt.% NaCl solution, with severe intergranular corrosion observed on the alloy surface. The passive films on Sc-free alloys primarily composed of Al₂O₃ and Cr₂O₃, while for Sc-containing alloys, the film mainly contains Al₂O₃, Cr₂O₃ and Sc₂O₃. In addition, the passive films on Sc-free alloys behave as an n-type semiconductor, while the passive films on Sc-containing alloys surface exhibit the electronic characteristics of p-n junctions. As the Sc content rises, the defect density in passive film increases from 10²¹ cm⁻³ to 10²³ cm⁻³, which leads to a less compact and less protective passive film, ultimately decreasing the alloy’s corrosion resistance. This work holds significant guiding significance for the engineering application of high-entropy alloys in acidic environments and is conducive to the development of highperformance corrosion-resistant alloys.

This study addresses the enhanced cycling stability of zinc-based flow batteries through a synergistic strategy integrating a vine-derived porous carbon framework (3D VPCF) with nicotinamide (NAM) in alkaline Zn-Fe hybrid liquid-solid flow batteries. By introducing 0.15 mol/L NAM to suppress zinc dendrite growth and regulate deposition behavior, combined with 0.05 mol/L ZnO additives for optimized nucleation and electrolyte conductivity, we achieved enhanced reversibility of zinc deposition/dissolution and interfacial stability. The system exhibits stable charge/discharge plateaus at 5 mA/cm² (non-normalized to electrode area), demonstrating 99.9 % capacity retention over 1000 cycles. This work provides an innovative pathway for developing stable zinc-based energy storage systems.

The recovery of lithium from spent lithium-ion batteries (LIBs) is of great importance in addressing lithium shortages and environmental issues. In this study, a novel and clean process for selective separation of lithium from spent LiFePO₄ cathode material by low temperature oxidative roasting and water leaching was proposed. The effect of several important factors, such as roasting temperature, roasting time, and molar ratio of ferric chloride (FeCl₃ • 6H₂O) to lithium iron phosphate (LFP), on the leaching efficiency of lithium and iron was systematically investigated by using single factor experimental method. The results show that approximately 97.1% lithium element was recovered by being converted to water-soluble LiCl at a roasting temperature 350 °C, a roasting time 120 min and a FeCl₃ • 6H₂O/LFP molar ratio of 1:1, and iron element was enriched in the leaching residue in the form of insoluble FePO₄ High-purity lithium carbonate products could be prepared from the leching solution by adding Na₂CO₃ after removing iron. The establishment of new cleaning process can provide a scalable, environmentally friendly and simple way to recover valuable metals from spent LFP batteries.

Potassium-ion batteries (KIBs) are rising as a noteworthy contender to lithium-ion batteries (LIBs), particularly for large-scale applications, driven by the natural abundance and cost-effectiveness of potassium resource. Yet, lacking anodes which can reversibly accommodate the larger K⁺ currently poses a critical development hurdle, highlighting an urgent need for innovative solutions. Herein, porous ZnO-SnO₂-graphene-carbon (ZTO-G-C) nanofibers are presented, featuring amorphous SnO₂ and ZnO nanoparticles homogeneously dispersed within a carbon matrix, with the strategic graphene incorporation for enhanced performance. Employing an adjustable and straightforward electrospinning method, the nanofibers were crafted to achieve a stable fibrous architecture. When evaluated as KIB anodes, the ZTO-G-C nanofibers demonstrated remarkable cycling stability (retaining 230.82 mA·h/g over 100 cycles at 100 mA/g), and rate capability (184.78 mA·h/g at 1 A/g). This outstanding performance is due to the synergistic interaction among all active components, collectively enhancing the structural stability against volume expansion during K⁺ intercalation, facilitating efficient charge transport, and delivering exceptional cyclability, capacity, and rate performance. Moreover, the intrinsic pseudocapacitive behavior stemming from the porous carbon substrate of ZTO-G-C further boosts its overall K-storage capacity. It is anticipated that the insights gained from this study offer fresh perspectives for developing next-generation high-performance KIB anodes.

Solid-state electrolytes (SSEs) have attracted much attention due to their high safety and cycling stability for lithium-ion batteries. However, the high interface impedance between the electrode and the solid-state electrolyte hinders their practical application. In this work, the solid-liquid hybrid electrolyte S-Li_1.3Al_0.3Ti_1.7(PO₄)₃-LE05(S-LATP-LE05) (LATP: Li_1.5Al_0.5Ti_1.5 (PO₄)₃) sheet is prepared by dropping liquid electrolyte (LE) with appropriate FeF₂ into spark plasma sintering S-LATP (solid-liquid hybrid electrolyte), which shows high-density and high-ionic-conductivity (5.78×10⁻⁴ S/cm). When the amount of FeF₂ is 0.5 wt%, the interfacial properties between the anode and electrolyte are improved, and the S-LATP is well protected by LiF-rich (solid electrolyte interface) (SEI) interface in cycling process. The Li∣S-LATP-LE05∣Li symmetric battery and full battery show better electrochemical performance and stability relatively. The overpotential of the Li∣S-LATP-LE05∣Li symmetric battery is smaller and shows more stable electrochemical performance after cycling for 350 h, revealing good compatibility with a lithium metal anode and can inhibit the growth of lithium dendrites effectively. The Li∣S-LATP-LE05∣LiFePO₄ full battery delivers a specific discharge capacity of 160 mA·h/g at 0.2C for 50 cycles. The corresponding coulombic efficiency is about 99.9% and displays better rate performance compared with the battery without FeF₂ LE.

Sb₂S₃ films are susceptible to the formation of nanogap defects during the crystallization process, leading to their experimental power conversion efficiency (PCE) falling significantly short of the theoretical limit. This investigation presents, a groundbreaking Sb₂S₃ photovoltaic device model that integrates perovskite within these nanogaps, and systematically examines the mechanisms for enhancing the PCE. Our findings reveal that incorporating perovskite within the nanogaps yields a 10% enhancement in optical absorption performance. Furthermore, perovskite nanogaps function as effective electron transport channels, significantly reducing the recombination of photogenerated carriers within the highly defective Sb₂S₃. The dimensions and arrangement of the nanochannels play a pivotal role in determining device performance, with optimal measurements of 5 nm in width and 15 nm in spacing. Additionally, this study examines the universality of the nanochannel structure. The projected PCE of this innovative structure is an impressive 25.40%. These findings provide valuable theoretical guidance for designing high-efficiency Sb₂S₃ solar cells.

Mo₂CT_x MXene is a novel two-dimensional material, which is generally made by the etching of inorganic acid solutions, such as hydrofluoric acid (HF) or hydrochloric acid (HCl). Those solutions are always corrosive and hazardous. In this paper, a mild organic acid, acetic acid (CH₃COOH), was selected to synthesize Mo₂CT_x MXene. 30 mL acetic acid (HAc) with the concentration of 13 mol/L was mixed with 2 g acetate (CH₃COONa or CH₃COOK) and 10 mL water to make etching solution (NaAc+HAc or KAc+HAc). In the solution, the concentration of CH₃COO⁻ was 10 mol/L, the concentration of Na⁺/K⁺ is 0.6/0.5 mol/L. The pH value is 2.8. Mo₂CT_x was obtained by hydrothermal etching at 240 °C for 1 d. Compared with the general method of HF etching, the etchant is milder and the etching process is safer. On the surface of Mo₂CT_x nanosheet made by this method, acetate group (CH₃COO⁻) was adsorbed as termination, which is larger than the F/O/OH termination of that made by general HF etching. The lattice parameter c (LPc) of Mo₂CT_x etched with NaAc+HAc/KAc+HAc is 21.09 Å/20.89 Å. Moreover, the specific surface areas of the samples etched by NaAc+HAc and KAc+HAc were 18.1 m²/g and 14.1 m²/g, respectively, which were much larger than those etched by conventional methods. As the anode of lithium-ion battery, the specific capacity under current density of 100 mA/g at 100th cycle was 108 mA·h/g, which is higher than the capacity of samples made by general HF etching. This work reports a novel method to make Mo₂CT_x MXene by the solution of mild acetic acid. The samples made by this method had very high specific surface area and relatively high lithium-storage performance.

Indium (In) has been used as a thermal interface material (TIM1) in high-performance central processing unit (CPU) for better heat dissipation. However, leakage or pump-out of liquid indium during the multiple reflow cycles limits its application in advanced flip chip ball gray array (FCBGA) packaging. Former researchers place a seal or dam structure to prevent In leakage, leading to the risk of In explosion, thermal degradation, or require additional keep-out zones. In this work, a copper foam (CF) matrix was embedded in In to absorb the liquid In and eliminate the leakage of In TIM1 during the multiple reflow cycles, as the CF capillary force. Au/Ni/Cu-Au/Ni/Cu joint was fabricated by soldering with the composite solder at 190 °C for 2 min. After reflow cycles, good metallurgical bonding was formed at interfaces of joint. Rod-like Cu₁₁In₉ formed at the CF and In interface, due to the re-dissolved of Cu₁₁In₉ crystal. Small amount of Cu atoms from CF can reduce the activity of In, which inhibits the growth of Ni₃In₇ intermetallic compound (IMC) at the interface of In and Au/Ni/Cu substrate. The CF matrix also improved the shear strength (22.9%) and thermal conductivity of the solder joints. Besides, the fracture behavior of solder joints without CF matrix was classified to be ductile type while that with CF matrix was changed to be ductile-brittle mixed type.

The femtosecond laser is commonly used for high-quality micromachining of materials. However, the interaction time between the femtosecond laser and the substrate material is extremely short, making it difficult for quantitative measurements and analysis through experiments. In this work, we use a two-temperature model for simulation to study the ablation process of aluminum alloy and aluminum/titanium alloy under femtosecond laser pulse mode. The temperature changes and ablation process of both alloys under femtosecond laser burst irradiation were studied. The study found that when the separation time of sub-pulses was 1 ps, the surface temperature and ablation depth rised with the increase of sub-pulse numbers. A comparison was made between these two alloy types, and enhanced ablation was observed with the heterogeneous aluminum/titanium alloy, up to 34.7% deeper compared to aluminum alloy. Moreover, the detailed theoretical explanation was also discussed. This work provided a basis for efficient ablation of materials with low laser fluence.

The efficient recovery of fluorite is paid more and more attention with the increasing application especially in strategic emerging industries. In this study, acrylic acid-2-acrylamido-2-methylpropane sulfonic acid copolymer (AA-AMPS) was first used as the depressant in fluorite flotation, and its effect on the flotation separation of fluorite and dolomite in sodium oleate (NaOL) system was investigated. The depression mechanism was analyzed by contact angle measurement, zeta potential test, FTIR and XPS analyses. The micro-flotation test results showed that dolomite can be inhibited in fluorite flotation system in the addition of 2 mg/L AA-AMPS and 20 mg/L NaOL at pH 10. The CaF₂ grade increased from 49.85% in the artificial mixed mineral to 89.60% in the fluorite concentrate. The depression mechanism indicated that AA-AMPS could adsorb strongly on dolomite surface by the chelation with Ca and Mg active sites. Moreover, the further adsorption of NaOL on dolomite surface was prevented by the AA-AMPS adsorption, but that on fluorite surface was little affected, thereby increasing the difference in the hydrophobicity and floatability of the two minerals.

High performance composite photocatalyst is a hotspot in the photocatalysis researches. In this study, a cutting-edge CeO₂/rutile composite photocatalyst with tiny CeO₂ concentration of 1.28 wt% was synthesized via a simple photocatalytic method. This as-obtained CeO₂/rutile catalyst (CeO₂/TiO₂-1:1) exhibited an enhanced wastewater degradation and improved water splitting H₂ evolution ability, with 95.83 % removal ratio for methylene blue (MB), 72.84% for tetracycline (TC) and 87.57 µmol/g H₂ evolution capacity. Light irradiation and 2-coordinated oxygen vacancies (OV_2C) on rutile surface promoted the Ce³⁺ adsorption on the rutile (110) facet as DFT results shown. The CeO₂/rutile type-II heterojunction was evidenced to promote the migration of e⁻/h⁺ and generation of ·OH/·O₂⁻ and H₂, which rapidly boosted the whole photocatalytic performance. This as-prepared CeO₂/TiO₂ photocatalyst can provide useful inspirations and new thoughts about the photosynthesis process, and offer a novel strategy for heterojunction photocatalysts preparation.

Developing a low-cost stable and high-performance peroxymonosulfate (PMS) catalyst to degrade refractory organic pollutants is still an urgent problem. Herein, this study reported FeVO₄ nanorods decorated sepiolite (FeVO₄/sepiolite) through simple hydrothermal method as an adsorptive-catalyst for PMS activation to degrade tetracycline (TC). Benefiting from the introduction of sepiolite support, FeVO₄ nanorods could be uniformly immobilized onto fibrous sepiolite surface. As a result, FeVO₄/sepiolite composite was endowed with excellent adsorption properties, rich surface hydroxyl groups, more reaction active sites, and the stable redox cycle of Fe³⁺/Fe²⁺ and V⁵⁺/V⁴⁺. Therefore, higher TC degradation efficiency (91.19% within 40 min) and larger reaction rate constant (0.1649 min⁻¹) were obtained in FeVO₄/sepiolite/PMS system than in FeVO₄/PMS system. Besides, the composite presented good stability and reusability, and the effects of application parameters on TC degradation were investigated in detail. Through quenching experiment and electron paramagentic resonance (EPR) test, it was found that both radical and non-radical species participates in TC degradation, and ¹O₂ were the main active species. The PMS activation mechanism was proposed, and the possible degradation pathway was also analyzed according to the high performance liquid chromatography-mass spectrometry (HPLC-MS) results. Overall, this work provides meaningful insights for designing natural mineral based PMS activators to effectively remediate antibiotic wastewater.

In practical engineering construction, multi-layered barriers containing geomembranes are extensively applied to retard the migration of pollutants. However, the associated analytical theory on pollutants diffusion still needs to be further improved. In this work, general analytical solutions are derived for one-dimensional diffusion of degradable organic contaminant (DOC) in the multi-layered media containing geomembranes under a time-varying concentration boundary condition, where the variable substitution and separated variable approaches are employed. These analytical solutions with clear expressions can be used not only to study the diffusion behaviors of DOC in bottom and vertical composite barrier systems, but also to verify other complex numerical models. The proposed general analytical solutions are then fully validated via three comparative analyses, including comparisons with the experimental measurements, an existing analytical solution, and a finite-difference solution. Ultimately, the influences of different factors on the composite cutoff wall’s (CCW, which consists of two soil-bentonite layers and a geomembrane) service performance are investigated through a composite vertical barrier system as the application example. The findings obtained from this investigation can provide scientific guidance for the barrier performance evaluation and the engineering design of CCWs. This application example also exhibits the necessity and effectiveness of the developed analytical solutions.

Under the influence of the upper coal pillars and dynamic pressure of coal mining, the roadway of the lower coal seam is prone to large deformation failure. In this paper, a novel control method and key technologies of automatically formed roadway (AFR) by roof cutting and confined concrete column in extremely close-distance coal seam are proposed. Furthermore, a numerical model is established to analyze the structure characteristics of overlying roof strata. Based on numerical results, the roof structure model of “voussoir beam of upper layer + short cantilever beam of lower layer” of this method is proposed. What’s more, the calculation equation of the roof bending moment and evaluation indexes is established, and the influence of different factors on roof stability control of AFR is studied. Finally, a field test is conducted to verify the effectiveness of this novel method. Field results were as follows: 1) The maximum and average support stress of working face obviously decreased; 2) The confined concrete column can provide high-strength support in dynamic influence zone; 3) The maximum deformation of AFR safety requirement can be met. This study can provide effective guidance for the application of this method in extremely close-distance coal seam.

Aiming at the problem that the distance between the main roadway and the working face in Hudi Coal Industry Panel was more than 100 m, which was still affected by mining, high stress concentration of the roadway, and difficulty of supporting overall convergence of the section, the mechanical characteristics of the core bearing strata of the overlying rock caving in the working face were studied. The correlation mechanism between the overlying rock caving and the deformation and failure of the roadway was analyzed, and the quantitative evaluation index was established to comprehensively analyze different influencing factors. Based on the key strata theory, the mechanical difference transfer model of working face mining and panel roadway deformation and failure was established. It was considered that the difference in fracture morphology was the key to the far-field stress disturbance. The regional stress control technology was proposed to block or reduce the stress transfer, so that the peak stress of the panel main roadway was reduced, and the deformation of the surrounding rock was significantly reduced, which provides a reference value for the roadway support with serious influence of mining roadway.

The surrounding rock of the soft rock roadway is seriously deformed and damaged under the superposition of mining stress and fault tectonic stress. In this paper, taking the No. 232206 intake roadway in Meihuajing coal mine as the engineering background, the deformation and failure law of the surrounding rock of the roadway in different fault protection pillar widths are obtained by numerical simulation method. On this basis, the mechanical model of the roadway under the action of hanging wall overburden migration and fault slip in normal faults is established, and the energy-driven mechanism of large deformation of the surrounding rock of the roadway was revealed. The ratio T of the energy applying on anchoring surrounding rock to the resistant energy of anchoring surrounding rock as the criterion for the deformation of the roadway. Finally, it was calculated according to the actual working conditions on site, and the control method of “stress relief-support reinforcement” was used to support the roadway with the risk of large deformation. The on-site monitoring results show that the control effect of the surrounding rock of the roadway is obvious.

Large-diameter drilling method is a prevalent method for preventing and controlling rock burst, and the spacing between the large-diameter drilling hole and anchoring hole is a critical factor influencing the roadway stability and relief effectiveness. In this study, a mechanical model for optimal matching between the large-diameter drilling hole and anchoring hole was established following the principle of synergistic control. The influence of large-diameter drilling hole diameter on the optimal spacing under the synergistic relief effect was investigated by integrating theoretical analysis, numerical simulation, and field practice. The results suggest that the hole spacing achieved a synergistic effect in a certain range when the optimal hole spacing increased linearly with the hole diameter. For instance, when the anchoring hole diameter was 20mm, an increase in the aperture ratio from 5 to 10 brought about an increase in the optimal spacing from 0.25m to 0.45m. Additionally, the vertical stress between the large-diameter drilling hole and anchor hole increased nonlinearly under the condition of constant pore ratio but varying hole spacing. Both excessively small and excessively large hole spacings were detrimental to the pressure relief effect. In the engineering practice, optimizing the hole spacing from 0.55m to 0.45m in the No.1208 working face contributed to reducing coal body drilling cuttings and the roadway moving quantity by 33% and 28%, respectively. This demonstrates that the pressure relief-support reinforcement synergistic effect should be fully considered in optimization design.

Axial chain rockbursts (ACRs) repeatedly occur in deep tunnels during Drilling and Blasting Methodology (D&B) within locked-in stress zones, severely hindering construction progress. In extremely cases, ACRs can persist for 10 days and affect areas exceeding 20 m along tunnel axis. Through integrated geological investigations and microseismic (MS) monitoring to analyze the geological characteristics, MS activity patterns, and formation mechanisms of ACRs. In tectonically active regions, locked-in stress zones arise from interactions between multiple structural planes. Blasting dynamic disturbances during tunnel excavation in these zones trigger early slippage along structural planes and fractures in the surrounding rock, with MS events developing ahead of the working face. High-energy MS events dominate during the development and occurrence stages of ACRs, extending 20–30 m (3–4 tunnel diameters) ahead of the working face. Following the ACRs, low-energy MS events primarily occur behind the working face. Tensile fracturing is the predominant failure mode during ACRs. Shear and mixed fractures primarily occur within the ACRs zone during the intra-ACR phase. Monitoring MS event locations ahead of the working face provides a reliable approach for prewarning potential ACR-prone zones.

In deep underground engineering construction, the dominant rock failure mode, whether by tension or shear, influences the engineering instability. Therefore, the critical triggering conditions that induce shear or tensile fractures in rocks urgently need further investigation. This paper designs direct shear tests on intact limestone under different normal stress conditions, using binarization methods supplemented by scanning electron microscopy to explore the two-dimensional fracture damage characteristics of limestone joint surfaces. Based on the three-dimensional morphological characteristics of limestone joint surfaces, a method for automatically identifying the three-dimensional curvature of rock joint surfaces is proposed, quantifying the changes in curvature distribution under different normal stresses. Further analysis focused on the proportion of shear damage and high-curvature areas on the upper and lower joint surfaces of limestone. The study examined changes in the cumulative energy of pre-peak acoustic emission and damage under varying effective normal stress-to-shear stress ratios. These results were used to identify and validate the critical threshold range for inducing shear fractures in limestone. The conclusions indicate that the proportion of shear damage area of limestone joint surfaces is positively correlated with effective normal stress. The proportion of high curvature of limestone joint surfaces decreases with increasing normal stress. Both the rapid growth stage of shear damage area and the rapid descent stage of high curvature proportion occur in the effective normal stress to shear stress ratio range of [1.4, 1.6]. The cumulative energy of pre-peak acoustic emission and damage under different effective normal stress to shear stress ratios increase sharply around the ratio of 1.6, further verifying that the effective normal stress to shear stress ratio range of [1.4, 1.6] is the critical threshold range for inducing shear fractures in limestone.

Rock-like specimens containing a joint with different inclination angles and roughness were prepared using 3D printing technology. Then, true triaxial compression loading experiments were conducted on those jointed specimens. The increase in roughness leads to an increase in the axial strength and peak strain. With the increasing inclination angle, the axial strength initially decreases from 30° to 60° and then increases from 60° to 90°. While the peak strain first rises from 30° to 45° and then declines from 45° to 90°. The variation in failure mode results from differences in lateral stress on the joints under different strike directions. Specimens with joint strike parallel to the intermediate principal stress predominantly showed matrix or matrix-joint mixed shear failure, whereas those parallel to the minimum principal stress exhibited matrix shear failure. The analysis results of acoustic emission signals indicate the crack number and shear crack percentage increase with the increasing roughness and first decrease (30° to 60°), then increase (60° to 90°) with the increasing inclination angle. The research results can provide some guidance for the design and support of underground engineering with jointed surrounding rock.

The shape of underground chambers in deep mining varies due to their geological environment and intended use, which results in different failure modes under the influence of mining activities. However, the effect of chamber shape on the mechanism of structural integrity under dynamic load is still unclear. In this paper, granite samples with circular (C), rectangular (R), long ellipse (EL), and short ellipse (ES) holes were prepared. The dynamic mechanical response and cracking mechanism of granite were systematically analyzed using the split Hopkinson pressure bar (SHPB) test system and the hybrid finite and discrete element method (HFDEM). The results indicate that the dynamic strengths of granite with EL and ES represent the maximum and minimum values within the range of close strain rates, respectively. When EL granite is subjected to dynamic load, the axial stress concentration (in the load direction) is weak, and the transverse stress shows relative dispersion, which is the primary reason for its highest dynamic strength. The failure of granite with various holes primarily involves a tensile-shear mixed fracture, with relatively few pure type II cracks. The chamber’s transverse span is the primary factor influencing the distribution range of the fracture area.

High-speed railway (HSR) bridge piers in high-altitude areas frequently face the challenge of early-age thermal cracking. This study employed numerical simulation methods to analyze the early-age temperature field, deformation field, and cracking risk of HSR bridge piers, considering three factors: binder content, cement types, and formwork types. The results show that the cracking risk slightly increases with a higher content of cementitious materials. However, this risk can be mitigated by selecting cements with lower heat of hydration and formwork materials with higher thermal conductivity. A variable termed “representative temperature rise for unit concrete” was proposed to integrate these three factors and comprehensively reflect the inherent thermal property of the pier. Subsequently, three linear regression models for predicting the demolding age of HSR bridge piers were established. These models empower engineers to determine the earliest feasible time for formwork removal without the need for complex computational analyses.

This paper proposed a RIME-VMD-BiLSTM surrogate model to rapidly and precisely predict the seismic response of a nonlinear vehicle-track-bridge (VTB) system. The surrogate model employs the RIME algorithm to optimize the variational mode decomposition (VMD) parameters (k and α) and the architecture and hyperparameter of the bidirectional long- and short-term memory network (BiLSTM). After comparing different combinations and optimization algorithms, the surrogate model was trained and used to analyze a typical 9-span 32-m high-speed railway simply supported bridge system. A series of numerical examples considering the vehicle speed, bridge damping, seismic intensity, and training strategy on the prediction effect of the surrogate model were conducted on the extended OpenSees platform. The results show that the BiLSTM model performed better than the LSTM model, whereas the prediction effects of the single-LSTM and BiLSTM models were relatively poor. With the introduction of the VMD and RIME optimization techniques, the prediction effect of the proposed RIME-VMD-BiLSTM model was excellent. The abovementioned factors had a significant influence on the seismic response of a VTB system but little impact on the prediction effect of the surrogate model. The proposed surrogate model exhibits notable transferability and robustness for predicting the VTB’s nonlinear seismic response.

Precise solutions for wheel-rail adhesion are important to the traction and braking of the high-speed trains under wet conditions. Current models predominantly rely on Hertzian contact theory assumptions. The present work proposes a novel non-Hertzian wheel-rail adhesion model to clarify the adhesion mechanisms under wet conditions. The non-Hertzian elastohydrodynamic lubrication (EHL) model was developed to obtain wheel-rail normal contact pressure under wet conditions with rough surfaces. The non-Hertzian extended creep force (ECF) model, which considers the effects of pressure and temperature on the elastic-plastic characteristics of the third body layer (3BL), was used to solve the tangential problems based on wheel-rail normal contact results. The numerical model was also validated by the high-speed wheel-rail adhesion laboratory tests. The wheel-rail rolling contact characteristics at different wheelset lateral displacements are investigated. The results reveal that the distributions of normal pressure, film thickness, tangential stress, and temperature show typical non-Hertzian characteristics. Finally, the effects of train speed and surface roughness on the adhesion characteristics are studied at different lateral displacements. The findings show that the present model can be used for the prediction of high-speed railway adhesion characteristics.