Polymer nanocomposite coatings (PNCCs) are unprecedented generation of coatings engineered for displaying inexpensive and brilliant functional surface coatings with eminent corrosion guard, mechanical resistance, antimicrobial, chemical durability, electrical insulation, and UV aging features. Due to their widely anticipation in petroleum, applications in building, conveyance, aerospace, electronics, automobiles and energy, these multi-functional coatings have a tremendous leverage in human life, all technological and scientific subjects. Numerous applications have been made for multilateral polymers like polyurethane (PU), epoxy (EP), polyaniline (PANI) conductive polymer, polypyrrole (PPy), and etc, on various metallic surfaces especially, carbon steel substrate owing to their excellent resistance properties. Practically, nanomaterials can possess potential in the all-interdisciplinary domains of materials science and engineering, chemical and physical sciences, biological and health sciences. As known, the designed polymer nanocomposite coating paradigm is fundamentally constituted from polymer or resin as a vehicle and inorganic nanofillers (nanoparticles and nanocomposites). Some commercialized and excessively employed nanocontainers in polymer nanocomposite coating formulations, like ZnO, TiO₂, carbon nanotubes (CNTs), clay, SiO₂, Al₂O₃, graphene, GO, CeO₂, ZrO₂, FeTiO₃, etc were discussed. The current review covered the chemistry and potential applications of the largest utilized multifunctional polymer nanocomposite coatings such as EP, PU and other considerable PNCCs. Lately, a titanic attention was made for epoxy nanocomposites because of their distinct physicochemical characteristics, which result from the combined qualities of the nanoparticles and polymer material unity. In addition, the author incorporated some of his scientific contributions in this area represented in construction of innovative functional polymer nanocomposites for a variety of uses with high economic, industrial impacts and future orientation. Furthermore, some newly published applications of polymer nanocomposite coatings were incorporated and discussed.

Zn-Mn alloys are regarded as promising biodegradable metals for orthopedic applications owing to their moderate degradation rates and favorable osteogenic properties. However, the presence of a substantial number of second-phase particles in Zn-based alloys might induce severe localized degradation via micro-coupling corrosion, thereby compromising the mechanical integrity of the alloy during in vivo tissue regeneration. In this study, high-pressure solid solution (HPSS) treatment was conducted at 5 GPa and 380 °C for 1 h to fabricate Zn-0.5Mn alloys. Microstructural characterization revealed that the HPSS treatment facilitated the formation of a supersaturated solid solution by completely dissolving the ζ-MnZn₁₃ phase into the α-Zn matrix. The resultant strengthening mechanisms, including supersaturated solid solution strengthening, grain-size strengthening, and dislocation strengthening, collectively enhanced the compressive yield strength (σ_cys) of the Zn-0.5Mn alloy to about 183.7 MPa, approximately three times that of the as-cast (AC) Zn-0.5Mn alloy. Moreover, compared with the AC alloy, the HPSS Zn-0.5Mn alloy exhibited uniform degradation behavior with a markedly reduced degradation rate.

Zn’s natural degradability and biocompatibility make it a promising candidate for implants, however, its mechanical properties remain insufficient for bone applications. In this study, the performance of Zn was enhanced by developing Zn-Cu alloys via laser powder bed fusion (LPBF). Optimal LPBF parameters for forming stable tracks were achieved by adjusting laser power and scanning speed. Under optimized conditions of 100 W and 100 mm/s, high-density (99.58%) Zn-Cu alloys with improved hardness (68.2HV) and yield strength (160 MPa) were achieved. These improvements are attributed to solid solution strengthening, segregation strengthening, and grain refinement. The Zn-Cu alloys also demonstrated favorable degradation behavior, with a rate of 0.16 mm/year. This degradation is primarily driven by micro-galvanic corrosion between the CuZn₅ phase and Zn matrix, along with refined grains and increased grain boundary density. This work demonstrates a viable strategy for fabricating Zn-based implants with enhanced structural integrity and mechanical performance via LPBF.

Hard tissue repair materials that balance high strength with low modulus are highly promising, representing a transformative focus in applied biomaterials research. In this study, Ti-Nb alloys with high performance are prepared by a low-cost process for orthopedic applications. Phase composition, modulus, compressive strength and recovery properties are effectively manipulated by tailoring trace amounts of interstitial oxygen. With increasing oxygen concentration in sintered Ti-Nb alloys, the β (body centered cubic) phase was stabilized due to the lattice distortion. The elastic modulus declined from 91 to 24 GPa. The compressive strength slightly decreased from 1595 to 1404 MPa and yield strength increased from 760 to 904 MPa. Additionally, the recovery properties were enhanced by the interstitial oxygen as a shape memory alloy. The utilization of trace oxygen serves to modulate the thermoelastic martensitic transformation in Ti-Nb alloys, thereby obtaining appropriate mechanical properties. A notable reduction in modulus is achieved while maintaining high strength, which facilitates the development of orthopedic implants capable of withstanding more complex forces.

Laser welding is a highly promising joining method for Al alloys. However, certain limitations such as elevated thermal input and keyhole instability are associated with its application in medium-thickness aluminium alloy plates. To address these issues, circular oscillating laser welding combined with post-weld heat treatment was employed to improve the formation quality and mechanical properties of the welds. The effects of the frequency of circular oscillating laser on the forming quality, microstructure, and properties of the welds were analyzed. At an oscillation frequency of 200 Hz, the grain size in the weld zone was reduced compared to single laser welding, and the maximum tensile strength of the weld was observed to reach (264.96±1.33) MPa, representing approximately 61.19% of the base metal. Following the post-weld heat treatment of “solid solution and artificial aging”, the grain boundary segregation was diminished. Nanoscale precipitated phases are present in the weld zone. Furthermore, the tensile strength was augmented to (386.35±5.65) MPa, representing approximately 89.23% of the strength of the base metal. The results of this study can provide a theoretical basis and technological reference for the circular oscillating laser welding of medium-thickness 2219-T6 aluminium alloy plates.

This work examines the microstructure and corrosion properties of fine-grained Al7075 across different regions under varying cooling conditions during friction stir welding. The findings demonstrate that forced cooling significantly improves the corrosion resistance of the welded joints. Specifically, the corrosion resistance was the highest in the stir zone, followed by the thermo-mechanical affected zone, and then the heat affected zone. Forced cooling mitigates grain growth by controlling the welding thermal effects, thereby increasing the proportion of Σ3 grain boundaries. The modification of these microstructural characteristics promotes the formation of a dense oxide layer, thereby enhancing the corrosion resistance. Furthermore, forced cooling mitigates the precipitation and coarsening of the anodic phase in the stir zone, which in turn reduces the susceptibility of the joint to pitting corrosion. Additionally, the lower recrystallization texture content in the joint, resulting from forced cooling, contributes to a reduction in the number of corrosion-active sites, thereby further improving the corrosion performance of the welded joint.

In order to effectively prevent the contamination of carbon particle volatiles during high-purity SiC crystals are prepared using the physical vapor transport (PVT) method in ultra-high temperature environments (T≥2000 °C), this study innovatively attempts to protect graphite materials with SiC reinforced pyrolytic graphite (PyG) coating. It is discovered by preparing the SiC particle layer, the degree of graphitization and stability of PyG coating can be improved. The corrosion test results demonstrated that the SiC reinforced PyG coating can maintain an intact coating with a high graphitization degree after the SiC vapour corrosion test of 2050 °C-120 h. Conversely, the samples with and without PyG coating reveal porous and eroded surfaces. Furthermore, following the SiC vapour corrosion test, the PyG coating sample’s integral ratio of D-band and G-band (I_D/I_G) of Raman spectrum test data, reduced by 6.5%, while the SiC reinforced PyG coating decreased by 17.2%, indicating its excellent corrosion resistance. The application of SiC reinforced pyrolytic graphite coating in preparing the SiC single crystal might received a theoretical foundation according to this work.

Waterborne acrylic coatings are widely utilized due to their cost-effectiveness, high transparency, strong resistance to weather and chemicals, impressive mechanical properties, and excellent adhesion to various substrates. In these coatings, a reactive emulsifier containing phosphate groups can be integrated into the molecular chain during polymerization, which enhances the coating’s compactness and corrosion resistance. This work focuses on the synthesis of styrene-butyl acrylate (St-BA) latex and methyl methacrylate-butyl acrylate (MMA-BA) latex using the reactive phosphate emulsifier ANPEO₁₀-P₁ through seed emulsion polymerization, achieving a conversion rate of approximately 99% and a solid content close to 50%. The resulting coatings from St-BA and MMA-BA latexes demonstrated long-term corrosion protection for carbon steel and aluminum alloy due to in-situ phosphatization, effectively preventing flash rust. Notably, the MMA-BA coating exhibited remarkable durability, enduring immersion for up to 1224 h (51 d) on Q235 carbon steel before reaching the failure threshold (∣Z∣_0.01Hz≤10⁶ Ω·cm²) on Q235 carbon steel. On 5052 aluminum alloy, the St-BA coating maintained ∣Z∣_0.01Hz>gt;10⁸ Ω·cm² for 480 h (20 d). Furthermore, the corrosion resistance of St-BA and MMA-BA coatings on Q235 steel sheet and 5052 aluminum alloy surpassed that of commercially available MMA-BA and St-BA coatings after immersion in a 3.5 wt% NaCl aqueous solution. This work also delves into the anticorrosion mechanism of MMA-BA and St-BA coatings.

This comprehensive study investigates the formation and evolution of intermetallic compounds during the solidification process of magnesium alloys using advanced micro X-ray computed tomography. By analyzing both common industrial Mg-Al-Zn alloys and a novel rare earth-containing Mg-Ni-Gd-Y alloy, we aim to characterize the nucleation, growth, and distribution of Al-Mn and eutectic intermetallics across various stages of solidification. The nondestructive imaging technique employed in this research provides high-resolution, three-dimensional insights into the microstructural development, allowing for a detailed examination of the morphology, spatial arrangement, and interconnectivity of intermetallic phases. This approach overcomes limitations of traditional two-dimensional metallographic methods, offering a more comprehensive understanding of the complex three-dimensional structures formed during solidification.

This study develops a contact performance-driven method for skiving face gear drives using a single cutter, eliminating the traditional need for separate cutters to reduce production costs and time. First, the mathematical models of the tooth flanks for the face gear drives are established based on the gear skiving processes. Then, load tooth contact analysis (LTCA) model is established to calculate the contact performance data. Next, a two-stage optimization model is employed to determine the optimal parameters of the cutting edge with improved contact performances. The effectiveness of this method is validated through simulations and rolling tests. Compared with the traditional method, the proposed method can machine both the face gear and its mating pinion with a single cutter. Simulation results show that the proposed method avoids tooth surface edge contact, with the maximum tooth surface contact stress reduced by 31.7%, the contact ratio decreases by 21.5%, and the transmission error increases by 22.3%. Rolling tests verify the consistency of tooth surface contact patterns between simulations and experiments. The proposed method provides a reference for the cutting edge design of skiving cutters for face gear pairs.

Seabed mining operations have been found to induce significant movement and deformation in overlying rock strata, posing serious threats to mining safety. The presence of geological faults further complicates these deformation patterns. This study utilized geophysical surveys and the continuum-based discrete element method (CDEM) to investigate how fault activity influences rock deformation and failure. The results demonstrate that: 1) Acting in mechanically weak zones, faults exerted a pronounced barrier effect on deformation propagation and stress redistribution within the surrounding rock, leading to markedly divergent displacement patterns on either side of the fault plane. Comparative analyses between single-fault and double-fault models revealed an 18%–22% expansion of the damage zone under the latter, together with significantly intensified deformation and failure; 2) The double-fault model exhibited a larger maximum cumulative vertical displacement and a spatial shift in the location of peak deformation, thereby posing a heightened threat to mine safety; 3) Acting in an orebody substitute, backfill effectively constrained surrounding rock deformation, enhanced its load-bearing capacity, and delayed the overburden subsidence. Nevertheless, backfill only reduced the amplitude of deformation; it could not entirely prevent settlement. These findings provide essential theoretical insights and foundational knowledge for safer submarine mining practices.

A shaking table test was performed to investigate the different responses of piles with and without cement-soil reinforcement, considering both inertial and kinematic interactions. A comparison of the dynamic shear stress – strain hysteresis curves of soil profiles on the pile side with and without cement-soil reinforced piles indicates that cement-soil reinforced piles not only bear more tremendous shear stress but also have smaller strains under the action of cyclic shear stress. Furthermore, the cement-soil on the pile side not only shares part of the shear stress and modifies the bending moment distribution but also significantly enhances the resistance of the pile-side soil, reducing the lateral displacement of the superstructure. Cement-soil reinforcement reduced shear strains, inhibited sand liquefaction, and reduced superstructure displacements by 27%–47% (instantaneous) and 40%–65% (permanent). The proportion of horizontal load sharing between cement-soil reinforcement and saturated sand is considered, along with the change pattern of the subgrade reaction after sand liquefaction. An equivalent subgrade reaction calculation method is proposed, which accounts for the horizontal load-sharing ratios of soils with two different strengths. The test results indicate that the pile stress and displacement, estimated using the equivalent subgrade reaction, are in good agreement with the observed results.

Aiming at the problem of dynamic instability of hard-brittle jointed rock surrounding in deep tunnel/roadway engineering, combining with the support concepts of “coupling rigidity with flexibility” and “overcoming rigidity by flexibility”, the prevention and control method with “rigid-flexible coupling (R-F-C)” was put forward. Through numerical simulation calculation, the impact damage process, acoustic emission (AE) evolution characteristics, and element stress/displacement evolution characteristics of unsupported surrounding rock structure model, rigid supporting surrounding rock structure model, and “R-F-C” supporting surrounding rock structure model under horizontal bidirectional impact loading were compared and analyzed. Based on the theory of stress wave propagation, the dynamic instability catastrophe mechanism of three kinds of supporting structure models induced by horizontal bidirectional impact loading was revealed. Based on the Mohr-Coulomb strength theory, the stress discrimination methods of dynamic catastrophe of surrounding rock induced by horizontal bidirectional impact loading under three kinds of supporting structures were proposed. Combined with the above numerical simulation study, the explosion impact physical and mechanical test of “R-F-C” surrounding rock supporting plate structure was further designed and carried out. Finally, combined with the “conceptual model of ball-cliff potential energy instability”, the energy driving theory and energy transformation mechanism of impact-induced rockburst under three kinds of supporting structures were discussed deeply. The research results provided a scientific basis for further promoting the effective application of “R-F-C” supporting structure in the prevention and control of dynamic instability of deep tunnel/roadway surrounding rock.

The weak and broken roof, explosive control and other problems seriously restrict the promotion of non coal pillar self-forming roadway technology. In order to solve such problems, a new method of non coal pillar self-forming roadway through non-blasting roof cutting and pressure relief was proposed in this study. A systematic research system of “theoretical analysis-physical experiment-engineering verification” was constructed with the 9103 working face of Longmenta Coal Mine as the research object. Firstly, the theoretical analysis was conducted to reveal the roof cutting mechanics mechanism of rock mass weakened by dense drilling, establish the design criteria for key drilling parameters, and obtain the key design parameters of dense drilling in the test working face. Secondly, the physical model test was conducted to make clear that the dense drilling method can directionally cut off the goaf roof along the set position, reducing the stress and deformation of the roadway surrounding rock. Finally, the field engineering tests were conducted, and monitoring results showed that the pressure relief effect of the dense drilling method was comparable to that of the directional blasting method, achieving non coal pillar self-forming roadway mining under non blasting conditions.

To investigate the long-term stability of soft-hard interbedded rock masses with initial damage induced by earthquakes and periodic drying and wetting, this study prepared samples with different initial damage through cyclic loading and unloading (CLU) experiments followed by cyclic drying and wetting (CDW) experiments, and finally conducted creep experiments. The study analyzed the effects of initial damage on creep mechanical behavior, crack evolution, and explored failure precursor information, revealing the damage failure mechanisms. The results show that the structural characteristics of the rock mass control its macroscopic failure mode. Initial damage promotes microcrack development, influences the fracture mode, and increases the proportion of high-frequency (200–280 kHz) acoustic emission events during creep. Meanwhile, initial damage exacerbates creep characteristics, increasing the creep rate, shortening total creep failure time, and reducing long-term strength. The damage failure is attributed to: the generation of internal cracks and pores in the rock caused by CLU; mineral hydrolysis and expansion-contraction due to CDW, resulting in weakened intergranular cementation; and full development of cracks and pores under creep stress. Additionally, the deformation difference coefficient and the coefficient of variation of RA/AF values can serve as precursor indicators for creep failure.

Conglomerate rock’s complex and heterogeneous microstructure significantly affects its mechanical properties, especially under dynamic loading. However, research on their dynamic behavior and fracture mechanisms is limited. Through uniaxial compression tests and split Hopkinson pressure bar (SHPB) impact tests, the dynamic compressive mechanical properties and fracture mechanisms of conglomerate rock were studied. Nanoindentation and high-resolution X-ray computed tomography were employed to analyze the micro-mechanical behavior and internal structure of the conglomerate rock. Results indicate significant differences in mechanical properties between different gravel particles and cementing materials, with initial fractures primarily distributed at the gravel-cement interfaces. The dynamic mechanical properties of conglomerate rocks exhibit a clear strain rate dependency. Based on the stress – strain curves and failure characteristics, the dynamic compressive mechanical behavior can be categorized into two types using a critical strain rate. The dynamic compressive strength, peak strain, and toughness of conglomerate rock increased with the strain rate, with the strength at 54 s⁻¹ being 2.6 times that at 6 s⁻¹. The dynamic compressive fracture mechanism of conglomerate rock is related to the strain rate and microstructure; at low strain rates, gravel distribution is the key factor, whereas at high strain rates, gravel content becomes critical.

Irradiating hard rocks by a high-power laser can reduce localized hardness in the rocks; however, continuous lasers produce a large amount of melt that inhibits further heat absorption. Pulsed lasers allow rocks to absorb and dissipate energy and avoid melt formation. In this study, 200 W nanosecond pulsed laser was used to irradiate granite. The effects of laser parameters on the thermal cracking morphology, temperature field, warming pattern, and Leeb hardness of the granite surface were analyzed. The optimal laser parameters for softening granite were determined by performing objective optimization in MATLAB using granite’s melting point as the reference. Nanoindentation techniques were employed to assess the softening characteristics of the granite surface along the longitudinal direction. The results showed that three main forms of thermal damage occurred on the granite surface: oxidative decomposition, spalling, and melting. The damage state was affected by the average laser power, with the pulse width and repetition frequency affecting surface damage differently. Appropriate laser parameters effectively controlled the melt damage on the granite surface, and irradiation with nanosecond pulsed lasers effectively reduced surface hardness. However, excessive power can generate large amounts of hard melts and weaken the softening effect.

Accurate prediction of rockburst intensity levels is crucial for ensuring the safety of deep hard rock engineering construction. This paper introduced an expert system for rockburst intensity level prediction that employs machine learning algorithms as the basis for its inference rules. The system comprises four modules: a database, a repository, an inference engine, and an interpreter. A database containing 1114 rockburst cases was used to construct 357 datasets that serve as the repository for the expert system. Additionally, 19 types of machine learning algorithms were used to establish 6783 micro-models to construct cognitive rules within the inference engine. By integrating probability theory and marginal analysis, a fuzzy scoring method based on the SoftMax function was developed and applied to the interpreter for rockburst intensity level prediction, effectively restoring the continuity of rockburst characteristics. The research results indicate that ensemble algorithms based on decision trees are more effective in capturing the characteristics of rockburst. Key factors for accurate prediction of rockburst intensity include uniaxial compressive strength, elastic energy index, the maximum principal stress, tangential stress, and their composite indicators. The accuracy of the proposed rockburst intensity level prediction expert system was verified using 20 engineering rockburst cases, with predictions aligning closely with the actual rockburst intensity levels.

The development of metallic mineral resources generates a significant amount of solid waste, such as tailings and waste rock. Cemented tailings and waste-rock backfill (CTWB) is an effective method for managing and disposing of this mining waste. This study employs a macro-meso-micro testing method to investigate the effects of the waste rock grading index (WGI) and loading rate (LR) on the uniaxial compressive strength (UCS), pore structure, and micromorphology of CTWB materials. Pore structures were analyzed using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP). The particles (pores) and cracks analysis system (PCAS) software was used to quantitatively characterize the multi-scale micropores in the SEM images. The key findings indicate that the macroscopic results (UCS) of CTWB materials correspond to the microscopic results (pore structure and micromorphology). Changes in porosity largely depend on the conditions of waste rock grading index and loading rate. The inclusion of waste rock initially increases and then decreases the UCS, while porosity first decreases and then increases, with a critical waste rock grading index of 0.6. As the loading rate increases, UCS initially rises and then falls, while porosity gradually increases. Based on MIP and SEM results, at waste rock grading index 0.6, the most probable pore diameters, total pore area (TPA), pore number (PN), maximum pore area (MPA), and area probability distribution index (APDI) are minimized, while average pore form factor (APF) and fractal dimension of pore porosity distribution (FDPD) are maximized, indicating the most compact pore structure. At a loading rate of 12.0 mm/min, the most probable pore diameters, TPA, PN, MPA, APF, and APDI reach their maximum values, while FDPD reaches its minimum value. Finally, the mechanism of CTWB materials during compression is analyzed, based on the quantitative results of UCS and porosity. The research findings play a crucial role in ensuring the successful application of CTWB materials in deep metal mines.

The cemented tailings backfill (CTB) with initial defects is more prone to destabilization damage under the influence of various unfavorable factors during the mining process. In order to investigate its influence on the stability of underground mining engineering, this paper simulates the generation of different degrees of initial defects inside the CTB by adding different contents of air-entraining agent (AEA), investigates the acoustic emission RA/AF eigenvalues of CTB with different contents of AEA under uniaxial compression, and adopts various denoising algorithms (e.g., moving-average smoothing, median filtering, and outlier detection) to improve the accuracy of the data. The variance and autocorrelation coefficients of RA/AF parameters were analyzed in conjunction with the critical slowing down (CSD) theory. The results show that the acoustic emission RA/AF values can be used to characterize the progressive damage evolution of CTB. The denoising algorithm processed the AE signals to reduce the effects of extraneous noise and anomalous spikes. Changes in the variance curves provide clear precursor information, while abrupt changes in the autocorrelation coefficient can be used as an auxiliary localization warning signal. The phenomenon of dramatic increase in the variance and autocorrelation coefficient curves during the compression-tightening stage, which is influenced by the initial defects, can lead to false warnings. As the initial defects of the CTB increase, its instability precursor time and instability time are prolonged, the peak stress decreases, and the time difference between the CTB and the instability damage is smaller. The results provide a new method for real-time monitoring and early warning of CTB instability damage.

High ground temperature and unloading disturbance have emerged as critical factors impacting the property of cemented gauge-fly ash backfill (CGFB). The characteristics of energy and damage in CGFB were analyzed under conditions of high ground temperature and unloading by conducting triaxial unloading tests with different initial confining pressures on CGFB that had been cured at various temperatures. Based on dissipative energy, triaxial unloading confining pressure damage constitutive model of CGFB was constructed. It has been demonstrated that the ratio of elastic strain energy in CGFB decreases and the ratio of dissipated energy increases at the end of unloading increases under higher curing temperature. The change in the elastic energy consumption ratio curve of CGFB, which shifts from a gradual increase to a swift rise at a certain “inflection point”, can be utilized as a criterion for evaluating the failure of the unloading strength of CGFB. The triaxial unloading damage constitutive model for CGFB divides the damage progression into three distinct phases: initial damage stage, accelerated damage development stage, and rapid damage growth stage. The research findings offer a theoretical foundation for evaluating the extent of damage to CGFB caused by the combined influences of elevated ground temperature and unloading.

The effect of real-time high temperature and thermal treatment on the mechanical characteristics and crack evolution of granite with different grain sizes (i.e., 0.5 mm, 0.7 mm and 1.0 mm) is investigated by numerical simulation employing a grain-based model, and the impact of initial cracks on thermal-induced strengthening is also examined by integrating random cracks within the model before tests. The results revealed that thermal stress, induced by the mismatch in thermal expansion coefficient between various minerals, is the primary distinction between rock specimens in real-time high temperature and thermal treatment. With increasing temperature, the thermal stress gradually accumulates in quartz minerals under real-time high temperature but releases after thermal treatment. The high local contact force significantly affects the peak stress and crack evolution. Uniaxial compression simulation results demonstrate that progressive accumulation of thermal stress induces degradation in macroscopic peak strength and increase of microcrack density. The grain size controls the ratio of intergranular contacts to intragranular contacts, and leads to an increase in strong contact number in the intragrain and a decrease in strong contact number in the intergrain. The strengthening of uniaxial compression strength in the experiment can be well simulated by controlling the number of pre-existing initial cracks in the numerical model. Our conclusions are beneficial to a better understanding of the underlying mechanisms of thermal damage and thermal strengthening of granite for deep geological engineering.

To study the influence of support timing and support strength on the mechanical properties and deformation damage characteristics of a single-sided unloaded rock mass, a true triaxial perturbation unloaded rock testing system was used to conduct rock damage tests on sandstone with different support timing and strength paths. Based on the acoustic emission monitoring system, the spatial and temporal evolution characteristics of the whole process of rock body loaded instability under two stress paths were studied, and the mechanism of the reinforcing effect of stress support on the unloaded rock mass was analyzed. The results show that, within the scope of this study, both earlier applications of shoring and an increase in shoring strength can effectively improve the ultimate bearing capacity of the unloaded rock, which increases the ultimate bearing capacity of the unloaded rock mass by 60.31% and 54.96%, respectively; There is a phenomenon of rebound deformation of the rock mass during sudden changes in stress (single-sided unloading, stress support), which shows opposite expansion and compression platforms on the stress–strain curve; The crack evolution of unloaded rock under different stress support conditions shows the state law of “initial crack activations→middle steady state expansion→late main crack penetration”, and the lagging support significantly accelerates the crack evolution from local activation to main penetration; The single-sided unloading and stress-supporting stages have less influence on the unloading deformations σ_1u, σ_2u and support deformations σ_1t, σ_2t in the σ₁ and σ₂ directions, while they show significant response characteristics to σ_3u, σ_vu and σ_3t, σ_vt, and with the increase of the support strength, the stress-supporting stages σ_3t, σ_vt gradually increase and exceed the deformations generated by the unloading stages σ_3u, σ_vu; The increase of support strength can effectively compensate for the rock stress loss caused by unloading, which makes the maximum, minimum, and volumetric strain support coefficients during the loading and unloading of the rock body increase gradually while the effect on the intermediate principal strain support coefficient is small; During loading, the support strength of rock masses seeks a new bearing area by regulating stress equilibrium states. This process primarily manifests as a shift in the locations of the crushing zone and the main bearing area, accompanied by a corresponding transformation in failure patterns. Consequently, the rock mass transitions from asymmetric three-zone damage under no or weak support to approximate symmetric three-zone damage under strong support. Simultaneously, the main load-bearing area of the rock mass shifts from deep bearing in the unsupported to middle bearing under strong support as the support strength increases.

Offshore structures are constantly subjected to the complex forces of the marine environment, including wind, sea waves, currents, and seismic loadings. Among these, wind and sea wave forces persist throughout the structure’s lifetime. This study proposes a dynamic analysis approach that incorporates both time and frequency domain methods to investigate the structural responses of offshore structures under the combined effects of wind and wave forces. A wind-wave-pier coupling dynamic model is first developed using a small-scale single pier, with corresponding dynamic equilibrium equations established. Fluctuating wind and sea waves are simulated using the weighted amplitude wave superposition (WAWS) method and linear superposition, respectively. Wind and wave load histories are then derived via Fourier transforms. The structural dynamic responses under different loading scenarios (wind only, wave only, and combined wind and wave) are analyzed using the Newmark-β method. Additionally, the effects of varying wind and wave parameters on structural responses are evaluated. The simulation results demonstrate that the structural responses to wind-wave coupling are smaller than the superimposed effects of wind and wave forces acting independently. When wind speeds are relatively low, wave forces dominate structural displacement and serve as the primary source of vibration.

This paper proposes a passive control method to reduce peak values of slipstream and turbulent kinetic energy in a high-speed train wake by attaching vortex generators (VGs) onto the upper surface of the tail car. The impact of the VGs is assessed through the improved delayed detached eddy simulations (IDDES) after validating predictions against previous experimental measurements and other numerical predictions for the base case. The simulations indicate that strategically installed VGs can reduce the average slipstream velocity (U_slipstream) and the upper limit of slipstream velocity (U_{slipstream, max}) by ∼17% and ∼15%, respectively, as well as moving the peaks downstream by approximately train height, thus reducing the danger posed by slipstream to waiting passengers and trackside workers. Analysis shows that the wake turbulent kinetic energy diminishes as the vortex generators decelerate the downwash flow and reduce shear production in the wake. It is also found that the presence of VGs significantly impacts the flow on the upper surface near the tail by modifying the unsteady trailing longitudinal vortices through the formation of additional counter-rotating longitudinal vortices from the VGs. These latter vortices prevent the merging of vortical airflow around the trailing nose tip, which is otherwise induced by the longitudinal vortex of the train. They also reduce vortex intensity through cross-annihilation and cross diffusion as the wake advects downstream, limiting outwards advection through interaction with the image pair, and contributing to a decrease in the peak slipstream value. The method proposed offers a simple approach to wake control leading to significant slipstream benefits.

The safe driving and operation of trains is a necessary condition for ensuring the safe operation of trains. In particular, heavy-haul trains are characterized by the difficulty in driving and operation. Considering the uncertainties in train driving and operation, this paper analyzes the relationship between the safety of heavy-haul electric locomotive-hauled trains and driving and operation. It studies the auxiliary intelligent driving safety operation control methods. Through K-means to identify the characteristics of drivers’ driving manipulation, the hidden Markov model adaptively adjusts the train driving and operation sequence, and conducts auxiliary driving reconstruction for heavy-haul locomotive driving and operation. Based on the train running curve and the locomotive traction/braking characteristics, it smoothly controls the exertion of the traction/braking force of heavy-haul locomotives, thereby optimizing the driving safety control of heavy-haul trains in the vehicle-environment-track system. Finally, the train operation simulation and optimized driving verification are carried out by simulating some track sections. The results show that the proposed method can correct and pre-optimize driving operations, improving the smoothness of heavy-haul trains by approximately 10%. It verifies the effectiveness of the proposed train assisted driving control reconstruction method, facilitating the smooth and safe operation of heavy-haul trains.