An increase in RE element content in Mg alloys promotes the grain boundary precipitate, which affects the mechanical properties. However, the influence of grain boundary precipitates on microstructure of Mg-RE alloys during ageing and their role on ductility of the aged alloy is unclear. In this work, hot extrusion and ageing treatment were performed for Mg-9Gd-2Y-xNd-0.2Zr (x=1 wt.% and 3 wt.%) alloys, and grain boundary precipitates were formed in the extruded Mg-9Gd-2Y-3Nd-0.2Zr alloy due to the increase of Nd content. The extruded alloys exhibit a complete dynamic recrystallization (DRX) microstructure and a texture with the <0001> orientation parallel to the extrusion direction (ED). In addition, a large amount of fiber microstructures distributed by the second phase along the ED were formed in the Mg-9Gd-2Y-3Nd-0.2Zr alloy, while only a small amount of the second phase was observed in the Mg-9Gd-2Y-1Nd-0.2Zr alloy. After ageing treatment, a large amount of β′ phase precipitated inside the grains. The strength of the Mg-9Gd-2Y-1Nd-0.2Zr alloy increased from 202 MPa to 275 MPa but the elongation decreased from 12.8% to 2.6%, and the strength of the Mg-9Gd-2Y-3Nd-0.2Zr alloy increased from 212 MPa to 281 MPa but the elongation decreased from 13.7% to 6.2%. Among them, the Mg-9Gd-2Y-3Nd-0.2Zr alloy showed good overall mechanical properties, especially the elongation of the aged alloy was 58% higher than that of the Mg-9Gd-2Y-1Nd-0.2Zr alloy. The increase in ductility of the aged Mg-9Gd-2Y-3Nd-0.2Zr alloy attributed to the grain boundary precipitate promotes the formation of a large number of precipitation free zones (PFZs) with widths of 130–150 nm during ageing treatment.

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To weaken the basal texture and in-plane anisotropy of magnesium alloy, non-basal slips are pre-enhanced by pre-rolling with a single pass larger strain reduction at elevated temperatures. Then Mg alloy sheets with the thickness of 1 mm are achieved after five passes rolling at 300 °C. A double peak and disperse basal texture is generated after pre-rolling at higher temperatures when the non-basal slips are more active. So, the texture intensity of pre-rolled samples is reduced. Moreover, the distribution condition of in-grain misorientation axes (a method to analyze the activation of slips) shows that the pyramidal slip is quite active during deformation. After annealing on final rolled sheets, the texture distributions are changed and the intensity of texture reduces obviously due to static recrystallization. In particular, the r-value and in-plane anisotropy of pre-rolled samples are obviously lower than those of sample without pre-rolling.

Cold-rolling was conducted on AZ31 magnesium alloy with fine and coarse grains to produce plates with high density of shear bands and

twins, respectively. Then, these two kinds of plates are subjected to isothermal annealing to reveal the effect of shear bands and

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twins on recrystallization behavior. During annealing, static recrystallization occurs firstly in shear band zones and

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twin zones, which has different effect on texture and mechanical properties. With the increase of annealing temperature, strong basal texture remains in annealed SG-17% while the basal texture is weakened gradually in annealed LG-15%. Recrystallized grains from twin zones have a random orientation which is responsible for the weakened basal texture in annealed LG-15%. In addition, micro-hardness decreases gradually with the prolonged annealing time due to static recrystallization. LG-15% has a lower recrystallization activation energy because

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twins are benefit for the nucleation and growth of recrystallization grains. After 500 °C annealing, the yield strength decreases significantly with a significant improvement in failure strain. The annealed LG-15% has a much higher compressive strain than annealed SG-17% due to texture weakening effect.

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Heterogeneous structure exhibits superiority in improving mechanical properties, whereas their effects on fatigue damage properties have rarely been studied. In this work, we employed a high-throughput gradient heat treatment method (757–857 °C) to rapidly acquire the solution microstructure of the Ti-6554 alloy with different recrystallization degrees (0%, 40% and 100%), followed by the same aging treatment. The results showed that the β-hetero structure exhibited a yield strength (σ_YS) of 1403 MPa, an increase of 6.7%, and a remarkable improvement in uniform elongation (UE) of 109.7%, reaching 6.5%, compared to the homogeneous structure. Interestingly, introducing a heterogeneous structure not only overcame the traditional trade-off between strength and ductility but also enhanced fatigue crack propagation (FCP) performance. During FCP process, β-hetero structure, through hetero-deformation induced (HDI) strengthening effects, promoted the accumulation of geometric necessary dislocations (GNDs) within coarse α_S phase, enabling faster attainment of the critical shear stress of twinning and increasing twinning density. This facilitated stress relief, improved plastic deformation in the crack tip zone, and increased the critical fast fracture threshold from 30.4 to 36.0 MPa·m^1/2 showing an enlarged steady state propagation region. This study provides valuable insights on tailoring fatigue damage tolerance through heterogeneous structure for titanium alloys.

In this work, ultrasonic energy field assistance combined with tempering treatment is proposed to improve the microstructure and mechanical properties of A517Q alloy steel fabricated by laser directed energy deposition (LDED). The effects of ultrasonic vibration (UV) and tempering treatment on microstructure evolution, microhardness distribution and mechanical properties of deposition layer were studied in detail. The microstructure of UV assisted LDED sample after tempering is mainly composed of tempered sorbite (TS). Due to the improvement of microstructure inhomogeneity and grains refinement, UV assisted LDED sample with tempering treatment obtains excellent mechanical properties. The ultimate tensile strength (UTS), yield strength (YS) and elongation after breaking (EL) reach 765 MPa, 657 MPa and 19.5%, the increase ratios of UTS and YS are 14.5% and 33.8% while maintaining plasticity compared to original LDED sample, respectively. It is obvious that ultrasonic vibration combined with tempering is a potential and effective method to obtain uniform microstructure and excellent mechanical properties in metal laser directed energy deposition field.

The ductile-to-brittle transition temperature (DBTT) of high strength steels can be optimized by tailoring microstructure and crystallographic orientation characteristics, where the start cooling temperature plays a key role. In this work, X70 steels with different start cooling temperatures were prepared through thermo-mechanical control process. The quasi-polygonal ferrite (QF), granular bainite (GB), bainitic ferrite (BF) and martensite-austenite constituents were formed at the start cooling temperatures of 780 °C (C1), 740 °C (C2) and 700 °C (C3). As start cooling temperature decreased, the amount of GB decreased, the microstructure of QF and BF increased. Microstructure characteristics of the three samples, such as high-angle grain boundaries (HAGBs), MA constituents and crystallographic orientation, also varied with the start cooling temperatures. C2 sample had the lowest DBTT value (−86 °C) for its highest fraction of HAGBs, highest content of <110> oriented grains and lowest content of <001> oriented grains parallel to TD. The high density of {332} <113> and low density of rotated cube {001} <110> textures also contributed to the best impact toughness of C2 sample. In addition, a modified model was used in this paper to quantitatively predict the approximate DBTT value of steels.

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The orientation effect of θ′ precipitates in stress-aged Al-Cu alloys has ambiguous interpretations. One view is that θ′ precipitates prefer to grow on the habit planes perpendicular to the applied compressive stress, while the other view suggests growth on habit planes parallel to the applied stress. In this study, stress-aged Al-4 wt.%Cu single crystal was sampled from three different <100>_Al zone axes to observe the distribution of θ′ precipitates. A hybrid Monte-Carlo/molecular dynamics simulations were used to investigate the orientation effect of θ′ precipitates. The simulation results are consistent with experimental observations and indicate that θ′ precipitates prefer to grow on the habit planes that are parallel to the direction of the applied compressive stress, not along the planes perpendicular to it. It is also found that 1/2<110> perfect dislocations are generated as θ′ precipitates plates grow thicker, and the reaction of 1/2<110> perfect dislocations decomposing into 1/6<112> Shockley dislocations lead to an increase in the length of θ′ precipitates. The former does not enhance the orientation effect, whereas the latter leads to a more significant orientation effect. Additionally, the degree of the orientation effect of θ′ precipitates is determined by the reduction of 1/2<110> dislocations with a positive correlation between them.

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Effects of ultrasonic bonding parameters on atomic diffusion, microstructure at the Al-Au interface, and shear strength of Al-Au ultrasonic bonding were investigated by the combining experiments and finite element (FE) simulation. The quantitative model of atomic diffusion, which is related to the ultrasonic bonding parameters, time and distance, is established to calculate the atomic diffusion of the Al-Au interface. The maximum relative error between the calculated and experimental fraction of Al atom is 7.35%, indicating high prediction accuracy of this model. During the process of ultrasonic bonding, Au₈Al₃ is the main intermetallic compound (IMC) at the Al-Au interface. With larger bonding forces, higher ultrasonic powers and longer bonding time, it is more difficult to remove the oxide particles from the Al-Au interface, which hinders the atomic diffusion. Therefore, the complicated stress state and the existence of oxide particles both promotes the formation of holes. The shear strength of Al-Au ultrasonic bonding increases with increasing bonding force, ultrasonic power and bonding time. However, combined with the presence of holes at especial parameters, the optimal ultrasonic bonding parameter is confirmed to be a bonding force of 23 gf, ultrasonic power of 75 mW and bonding time of 21 ms.

Graphene oxide (GO) reduced by Stachys lavandulifolia extract (SLE) was produced and characterised. The anti-corrosion behaviour of epoxy coatings containing GO and rGO nanosheets was investigated. FESEM-EDS, FT-IR, and Raman spectroscopy were used to examine the microstructure and chemical composition of the nanosheets and epoxy coatings. EIS experiment was used to explore the corrosion behaviour of the coatings. The O/C ratio for GO and rGO-SLE was found to be 2.5 and 4.5, indicating a decrease in the carbon content after the reduction of GO, confirming the adsorption of SLE onto the GO nanosheets. The successful reduction of GO in the presence of SLE particles was confirmed by disappearing the C=O peak and a significant decrease in the C—O—C bond intensity. The epoxy/rGO-SLE coatings exhibited the highest double-layer thickness and excellent corrosion resistance compared to neat epoxy and epoxy/GO coatings, emphasizing the significant role of rGO in enhancing the protective performance of epoxy coatings. The highest values for total charge transfer and film resistances and the inhibition efficiency were observed to be 6529 Ω·cm² and 90%, respectively, for the epoxy/rGO-SLE coated steel plate. It was also found that the epoxy/0.15 wt.% rGO-SLE coating demonstrates the best corrosion resistance performance.

The goethite residue generated from zinc hydrometallurgy is classified as hazardous solid waste, produced in large quantities, and results in significant zinc loss. The study was conducted on removing iron from FeSO₄-ZnSO₄ solution, employing seed-induced nucleation methods. Analysis of the iron removal rate, residue structure, morphology, and elemental composition involved ICP, XRD, FT-IR, and SEM. The existing state of zinc was investigated by combining step-by-step dissolution using hydrochloric acid. Concurrently, iron removal tests were extended to industrial solutions to assess the influence of seeds and solution pH on zinc loss and residue yield. The results revealed that seed addition increased the iron removal rate by 3%, elevated the residual iron content by 6.39%, and mitigated zinc loss by 29.55% in the simulated solution. Seed-induced nucleation prevented excessive nuclei formation, fostering crystal stable growth and high crystallinity. In addition, the zinc content of surface adsorption and crystal internal embedding in the residue was determined, and the zinc distribution on the surface was dense. In contrast, the total amount of zinc within the crystal was higher. The test results in the industrial solution demonstrated that the introduction of seeds expanded the pH range for goethite formation and growth, and the zinc loss per ton of iron removed was reduced by 50.91 kg (34.12%) and the iron residue reduced by 0.17 t (8.72%).

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Rich-nickel layered ternary NCM811 has been widely used in the field of electric vehicles ascribed to its high theoretical specific capacity. However, poor cycling stability and rate-performance hindered its further development. Herein, different amounts of nitrogen-doped carbon were wrapped on the surface of NCM811 via a facile rheological phase method by regulating the amount of dopamine hydrochloride. The effects of the coating amounts on the structure and electrochemical performance are investigated. The DFT calculation, XRD, SEM and XPS reveal that an appropriate amount of nitrogen-doped carbon coating could uniformly form a protective layer on the NCM811 surface and the introduced N could anchor Ni atoms to inhibit the Li⁺/Ni²⁺ mixing, but excessive amount would reduce Ni³⁺ to Ni²⁺ so as to conversely aggravate Li⁺/Ni²⁺ mixing. Among the samples, the NCM811-CN0.75 sample exhibits the most excellent electrochemical performance, delivering a high-rate capacity of 151.6 mA·h/g at 10C, and long-term cyclability with 82.2% capacity retention after 300 cycles at 5C, exhibiting remarkable rate-performance and cyclability.

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Copper is a versatile material, commonly utilized in power transmission and electronic devices, but its relative high reactivity necessitates a long-lasting protective technique. Here, we report a method that combines plasma-enhanced non-equilibrium magnetron sputtering physical vapor deposition (PEUMS-PVD) and anodization to construct a self-healing three-dimensional Ti/Al-doped TiO₂ nanotubes/Ti₃AlC₂ coating on the surface of Cu substrates. This novel strategy enhances the corrosion resistance of copper substrates in marine environments, with corrosion current densities of up to 4.5643×10⁻⁸ A/cm². Among them, the doping of nano-aluminum particles makes the coating self-healing. The mechanistic analysis of the corrosion behaviors during early immersion experiments was conducted using electrochemical noise, and revealed that during the initial stages of coating immersion, uniform corrosion predominates, with a minor occurrence of localized corrosion.

Preparing multifunctional coatings with both anti-corrosion and anti-biofouling properties is crucial. Copper has been in the spotlight as an effective biocide, especially in the recent past concerning its impact on causing environmental hazards. Reducing the amount used and increasing its efficiency have become the focus of researchers. The hybridization of titanium dioxide nanoparticles (NPs) with copper metal-organic frameworks (MOFs) can significantly improve antimicrobial performance due to its photocatalytic properties. Composites (TiO₂-Cu-BTC) of titanium dioxide nanoparticles and copper 1,3,5-benzenetricarboxylate acid (Cu-BTC), obtained by three up-sampling methods, namely hydrothermal, mechanical stirring, and in-situ growth, were doped into epoxy resin (TiO₂-Cu-BTC/EP) to enhance its anticorrosion and antifouling properties. The loaded forms were determined by field emission scanning electron microscopy and confirmed using Fourier infrared spectroscopy and X-ray diffraction spectroscopy. The lethality of the composite coating against Escherichia coli (E. coli) increased by 12% after 3 h of exposure to light, and the impedance value increased by 1 × 10¹⁰ Ω. The efficiency of the coating was greatly improved.

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It is still challenging for exploring high-active photocatalysts to efficiently remove Levofloxacin (LFX) by activating peroxymonosulfate (PMS). Herein, we constructed a novel Z scheme ZnFe₂O₄/g-C₃N₄/CQDs (ZCC) heterojunction by anchoring ZnFe₂O₄ on tubular-like g-C₃N₄ induced by CQDs (denoted as CNC) using microwave-assisted thermal methods. The ZCC exhibits the highest photocatalytic activity in activating PMS for LFX degradation, endowing a removal rate ∼95.3%, which is 4.8 and 7.3 times higher than that of pure ZnFe₂O₄ (19.8%) and g-C₃N₄ (13.1%), separately. The enhanced photocatalytic activity of ZCC can be attributed to the distinctive morphology of CNC, enhanced light response, increased specific surface area and abundant pore structure. Besides, the formed Z scheme heterojunction and CQDs acting as a transmission bridge of the photogenerated charges (e⁻ and h⁺) can accelerate transfer and inhibit recombination of e⁻ and h⁺. Radical capture experiments and electron spin resonance (ESR) measurements revealed that SO₄^•− and O₂^•− play a predominant role in degradation process of LFX. Liquid chromatography-mass spectrometry (LC-MS) was applied to identify intermediates and propose feasible degradation pathways of LFX. In conclusion, this study presents a promising strategy for regulating the photocatalytic activity of g-C₃N₄ by simultaneously integrating CQDs induction and Z scheme heterojunction construction.

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This study investigates the instability characteristics of dynamic disasters resulting from disruption caused by extracting resources underground. Utilizing the split Hopkinson pressure bar (SHPB) system, the dynamic response mechanism of coal energy evolution is examined, and the energy instability criterion is established. The validity of the instability criterion is explored from the standpoint of damage progression. The results demonstrate that the energy conversion mechanism undergoes a fundamental alternation under impact disturbance. Moreover, the energy release rate as well as the energy dissipation rate undergo comparable changes across distinct levels of impact disturbance. The distinction between the energy release rate and the energy dissipation rate (DRD) increases as coal mass deformation grows. Prior to coal facing instability and failure, the DRD experienced an inflection point followed by a sharp decrease. In conjunction with the discussion on the damage evolution, the physical and mechanical significance of DRD remains clear, which can essentially describe the whole impact loading process. The phenomenon that the inflection point appears and DRD subsequently suddenly decreases can be employed as the energy criterion prior to the failure of instability. Furthermore, this paper provides significant reference for the prediction of dynamic instability of coal under dynamic disturbance.

Breakage is an important step in the resource processing chain. However, the mechanical crushing methods commonly used today suffer from low energy efficiency and high dust levels. Promoting environmental protection and improving energy efficiency are crucial to advancing China’s circular economy. Mining companies are actively exploring novel and innovative technologies to significantly cut down on operating costs and minimize emissions of dust and pollutants generated during processing. Recently, high voltage pulse discharge (HVPD) technology has received widespread attention and has been reported to have good application prospects in resource processing. This paper presents an extensive review of the operational principles of HVPD and the unique characteristics it engenders, such as non-polluting, selective material fragmentation, pre-weakening, pre-concentration, and enhanced permeability of coal seams. Additionally, this review explores the potential and obstacles confronting HVPD in industrial contexts, offering fresh insights for HVPD optimization and providing guidance and prospects for industrial deployment and further development.

With the growing awareness of environmental protection and the increasing demand for rare earth elements (REEs), it has become necessary to efficiently remove and recover REEs from mine wastewater. In this study, jarosite (Jar) and schwertmannite (Sch) were biosynthesized using Acidithiobacillus ferrooxidans for the adsorption of REEs. Additionally, the adsorption capacities of Jar and Sch for La³⁺, Ce³⁺, Pr³⁺, Nd³⁺, Sm³⁺, Gd³⁺, Dy³⁺, and Y³⁺ in mine wastewater were improved by mechanical activation. XRD, FTIR, BET, and SEM-EDS analyses revealed that mechanical activation did not alter the phase of the material, but increased the amount of surface -OH and SO₄²⁻ groups, as well as the specific surface area. This significantly enhanced the adsorption performance of Jar and Sch for REEs. The optimum adsorption time and pH were determined through batch adsorption experiments. Besides, the adsorption kinetics were studied and found to align well with the pseudo-second-order model. Furthermore, the thermodynamic parameters (ΔG^Θ, ΔH^Θ and ΔS^Θ) and adsorption isotherms were analyzed. The results indicated that mechanically activated schwertmannite (M-Sch) exhibited superior adsorption performance for REEs compared to mechanically activated jarosite (M-Jar). Moreover, M-Sch was reusable and exhibited high adsorption efficiency of REEs in actual mine wastewater, exceeding 92%.

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Surface pretreatment can change the surface properties of minerals, placing them in either a favorable or an unfavorable state for flotation. To solve the separation problem associated with magnesite and dolomite, surface pretreatment experiments with citric acid, tartaric acid, and tannic acid (TA) on magnesite and dolomite as well as flotation experiments on pretreated samples were performed in this study. Experimental results demonstrated that when citric acid and tartaric acid are used for surface pretreatment, the separation effect of magnesite and dolomite is poor. However, when TA is used, the separation effect of magnesite and dolomite improves. SEM and BET analysis indicated that surface pretreatment with TA changes the surface morphology of the two minerals, resulting in additional concave pores on the dolomite surface, and a significant increase in pore size and specific surface area. The adsorption quantity test and contact angle measurement demonstrated that after surface pretreatment with TA, the magnesite adsorption capacity on sodium oleate (NaOL) slightly decreases and the dolomite adsorption capacity on NaOL considerably decreases. XPS detection concluded that the surface pretreatment of TA on the magnesite surface mainly relies on physical adsorption with weak adsorption ability and poor ability to act on Mg sites. The TA surface pretreatment action on the dolomite surface is mainly through chemical adsorption, and it is strongly and selectively adsorbed on the Ca site of dolomite through O. Actual ore rough selection experiments reveal that TA pretreatment successfully removes dolomite from magnesite, resulting in a high-quality magnesite concentrate characterized by a MgO grade of 45.49% and a CaO grade of 0.75%.

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The deformation behavior of hot-rolled AZ31 magnesium (Mg) alloy sheet was analyzed when subjected to uniaxial tension along its normal direction at temperatures ranging from 100 to 400 °C and strain rates ranging from 0.5 to 100 mm/min. Based on the stress – strain curves and the dynamic material model, the hot processing map was established, which demonstrates that the power dissipation factor (η) is the most sensitive to strain rate at 400 °C via absorption of dislocations. At 400 °C, sample at 0.5 mm/min possesses η of 0.89 because of its lower kernel average misorientation (KAM) value of 0.51, while sample at 100 mm/min possesses η of 0.46 with a higher KAM value of 1.147. In addition, the flow stress presents a slight decrease of 25.94 MPa at 10 mm/min compared to that at 100 mm/min and 100 °C. The reasons are twofold: a special ∼34° texture component during 100 °C-100 mm/min favoring the activation of basal slip, and dynamic recrystallization (DRX) also providing softening effect to some extent by absorbing dislocations. Difference in activation of basal slip among twin laminas during 100 °C-100 mm/min results in deformation inhomogeneity within the grains, which generates stress that helps matrix grains tilt to a direction favorable to basal slip, forming the special ∼34° texture component.

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In this work, the effect of ultrasonic vibration modes on the mechanical properties and relaxation of residual stress in 6061-T6 aluminum alloy was studied. A new ultrasonic vibration Johnson-Cook model was proposed, and the relaxation and distribution of residual stress under ultrasonic vibration were predicted and analyzed using the finite element method (FEM). The mechanical properties of 6061-T6 aluminum alloy under different ultrasonic vibration modes were analyzed through experiments involving notched specimen tensile testing and scanning electron microscopy (SEM) analysis. The findings indicate that ultrasonic vibration treatment during deformation, unloading, and load-holding, as well as treatment with its natural ultrasonic frequency, can effectively release residual stress; however, treatment with its natural frequency has the highest rate of release up to 65.4%. Ultrasonic vibration treatment during deformation better inhibits fracture under the same conditions. The FEM results are in good agreement with the experimental results, and it can be used as a valid tool for predicting residual stress release under ultrasonic vibration.

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Installing the splitter plates is a passive aerodynamic solution for eliminating vortex-induced vibration (VIV). However, the influences of splitter plates on the VIV and aerostatic performances are more complicated due to aerodynamic interference between highway and railway decks. To study the effects of splitter plates, wind tunnel experiments for measuring VIV and aerostatic forces of twin decks under two opposite flow directions were conducted, while the surrounding flow and wind pressure of static twin decks with and without splitter plates are numerically simulated. The results showed that the incoming flow direction affects the VIV response and aerostatic coefficients. The highway deck has poor vertical and torsional VIV, and the VIV region and amplitude are different under different directions. While the railway deck only has vertical VIV when located upstream. The splitter plates can impede the process of vortex generation, shedding and impinging at the gap between twin deck, and significantly reducing the surface fluctuating pressure coefficient, thus effectively suppressing the VIV of twin decks. While, the splitter plates hurt the upstream deck regarding static wind stability and have little effect on the downstream deck. The splitter plates of appropriate width are recommended to improve VIV performances in twin parallel bridges.

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Steel tube slab (STS) structure, a novel pipe-roof structure, of which steel tubes are connected with flange plates, bolts and concrete, is an increasingly popular supporting structure for underground space development. Whilst the load-bearing of pipe-roof structures has been the subject of much research, uncertainties of deformation mechanism and the derivation of reliable calculation methods remain a challenge. For efficient design and wider deployment, this paper presents a bidirectional bending test to investigate the bending stiffnesses, load capacities and deformation mechanisms. The results show that the STS specimens exhibit good ductility and experience bending failure, and their deformation curves follow a half-sine wave upon loading. On this basis, the development of an STS composite slab deformation prediction model is proposed, along with the estimation for its bending stiffness. Theoretical predictions are shown to be in good agreement with the experimental measurements, with a maximum error of less than 15%. The outcomes of this investigation can provide references for the design and application of STS structures.

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In existing studies, most slope stability analyses concentrate on conditions with constant temperature, assuming the slope is intact, and employ the Mohr-Coulomb (M-C) failure criterion for saturated soil to characterize the strength of the backfill. However, the actual working temperature of slopes varies, and natural phenomena such as rainfall and groundwater infiltration commonly result in unsaturated soil conditions, with cracks typically present in cohesive slopes. This study introduces a novel approach for assessing the stability of unsaturated soil stepped slopes under varying temperatures, incorporating the effects of open and vertical cracks. Utilizing the kinematic approach and gravity increase method, we developed a three-dimensional (3D) rotational wedge failure mechanism to simulate slope collapse, enhancing the traditional two-dimensional analyses. We integrated temperature-dependent functions and nonlinear shear strength equations to evaluate the impact of temperature on four typical unsaturated soil types. A particle swarm optimization algorithm was employed to calculate the safety factor, ensuring our method’s accuracy by comparing it with existing studies. The results indicate that considering 3D effects yields a higher safety factor, while cracks reduce slope stability. Each unsaturated soil exhibits a distinctive temperature response curve, highlighting the importance of understanding soil types in the design phase.

Because of actual requirement, shield machine always excavates with an inclined angle in longitudinal direction. Since many previous studies mainly focus on the face stability of the horizontal shield tunnel, the effects of tensile strength cut-off and pore water pressure on the face stability of the longitudinally inclined shield tunnel are not well investigated. A failure mechanism of a longitudinally inclined shield tunnel face is constructed based on the spatial discretization technique and the tensile strength cut-off criterion is introduced to modify the constructed failure mechanism. The pore water pressure is introduced as an external force into the equation of virtual work and the objective function of the chamber pressure of the shield machine is obtained. Moreover, the critical chamber pressure of the longitudinally inclined shield tunnel is computed by optimal calculation. Parametric analysis indicates that both tensile strength cut-off and pore water pressure have a significant impact on the chamber pressure and the range of the collapse surface block. Finally, the theoretical results are compared with the numerical results calculated by FLAC^3D software which proves that the proposed approach is effective.

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The surrounding rock is prone to large-scale loosening and failure after the excavation of shallow large-span caverns because of the thin overlying strata and large cross-section span. The rational design of bolt support is very important to the safety control of surrounding rock as a common support means. The control mechanism and design method of bolt support for shallow-buried large-span caverns is carried out. The calculation method of bolt prestress and length based on arched failure and collapsed failure mode is established. The influence mechanism of different influencing factors on the bolt prestress and length is clarified. At the same time, the constant resistance energy-absorbing bolt with high strength and high toughness is developed, and the comparative test of mechanical properties is carried out. On this basis, the design method of high prestressed bolt support for shallow-buried large-span caverns is put forward, and the field test is carried out in Qingdao metro station in China. The monitoring results show that the maximum roof settlement is 6.8 mm after the new design method is adopted, and the effective control of the shallow-buried large-span caverns is realized. The research results can provide theoretical and technical support for the safety control of shallow-buried large-span caverns.

This work aims to reveal the mechanical responses and energy evolution characteristics of skarn rock under constant amplitude-varied frequency loading paths. Testing results show that the fatigue lifetime, stress-strain responses, deformation, energy dissipation and fracture morphology are all impacted by the loading rate. A pronounced influence of the loading rate on rock deformation is found, with slower loading rate eliciting enhanced strain development, alongside augmented energy absorption and dissipation. In addition, it is revealed that the loading rate and cyclic loading amplitude jointly influence the phase shift distribution, with accelerated rates leading to a narrower phase shift duration. It is suggested that lower loading rate leads to more significant energy dissipation. Finally, the tensile or shear failure modes were intrinsically linked to loading strategy, with cyclic loading predominantly instigating shear damage, as manifest in the increased presence of pulverized grain particles. This work would give new insights into the fortification of mining structures and the optimization of mining methodologies.

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