This study investigated the effects of deep cryogenic treatment (DCT) on hot isostatic pressed (HIP) beryllium for inertial devices, focusing on residual stress, microstructure, tensile properties, and dimensional stability. The findings revealed that during DCT, residual stress in beryllium increased gradually due to non-uniform volumetric contraction and mismatch stress, reaching a 59.9% increase from initial levels after 200 h of DCT. DCT led to significant grain refinement and an increase in dislocation density. In 200 h DCT-treated beryllium, geometric necessary dislocation (GND) density increased 17.9%, grain size decreased 12.3%, and therefore yield strength and tensile strength improved by 4.2% and 5.6%, respectively. The dimensional stability of HIP beryllium was significantly enhanced by DCT, and the improvement tended to increase with the duration of DCT. The cumulative size changes of beryllium after 200 h of DCT during both cold exposure and cold cycling decreased significantly by 86% and 50%, respectively, compared to those of HIP beryllium. Furthermore, the residual tensile strength and retention rate increased by 12.5% and 5.5%, respectively, after undergoing room-temperature creep at 100 MPa for 1000 h.

The mechanism of SiC preparation via chemical vapor deposition (CVD) of the CH₃SiCl₃(MTS)-H₂ system remains unclear. This article integrates thermodynamic calculations, fluid dynamics simulations, and experimental validations to enable a synergistic analysis from thermodynamic equilibrium predictions to fluid dynamics-based dynamic modeling. The results systematically reveal the effects of process parameters on the SiC deposition procedure. It was found that the silicon-rich phenomenon observed at low temperatures is related to the low reactivity of CH₄ and the preferential adsorption of chlorosilanes. With increasing deposition temperature, the concentration of silicon-containing molecular species such as SiCl₂ rises, while unsaturated hydrocarbons like C₂H₂ become the dominant carbon sources at high temperature, ultimately producing nearly stoichiometric SiC coatings at 1400 °C. Notably, thermodynamic calculation results alone exhibited deviations from experimental results, whereas coupling with fluid dynamics simulations improved consistency significantly. This research method not only compensates for limitations inherent in thermodynamic calculations but also provides reliable theoretical basis and technical support for precise control of CVD parameters and optimization of SiC chemical composition.

The pH clock is critical for identifying acid-sensitive substances and elucidating the mechanisms of chemical processes using spectral techniques. Effectively controlling the rate of H⁺ release with inorganic acids is challenging due to their fast acidification property. In addition, the strong corrosiveness of inorganic acids and the slowing rate of acidification in organic acids with decreasing pH further limit their applicability in fine spectral analysis. Therefore, developing a simple, safe, acidifying agent capable of controlling H⁺ release with a well-defined identification window is crucial for advancing spectral detection technologies. This study presents niobium oxide dichloride (NbOCl₂) nanosheets as a novel acidifying agent that not only regulates the rate of H⁺ release but also has a smooth extinction spectrum, making it suitable for monitoring acid-responsive behavior. The results demonstrate that NbOCl₂ is an excellent platform for pH clocks. Using spectral dynamics and first derivative images of the time-resolved extinction data, we have quantified the key factors associated with the wavelength of the extinction spectrum. Transient absorption results further indicated that H⁺ released from NbOCl₂ nanosheets reduced absorption, with its carrier dynamics exhibiting pronounced size dependence. These properties suggest NbOCl₂ nanosheets to be an ideal candidate as an acidifying agent.

One of the main challenges of current metal-oxide-semiconductor field effect transistors (MOSFETs) is the exponential increase in the tunneling- (and leakage-) current through the gate dielectric material while shrinking the gate dielectric material thickness. Over the last two decades, many researchers have attempted to find an alternative material for the gate dielectric of transistors that has the advantages of the current silicon oxide gate dielectric of MOSFETs but without its disadvantages. In the search for an excellent gate dielectric, researchers have compared the key electrical parameters with those of current gate dielectric materials. They applied equations, approaches, and relationships for their evaluations and estimations, which may be incomplete relationships and most likely did not lead to the correct evaluation probability. Among the cases, the great importance is the relationship with the leakage-current from the gate dielectric layer in organic field-effect transistors (OFETs) or thin-film transistors (TFTs). In these discussions and evaluations based on the conventional leakage-current relationship, interactions related to particle exchange and pinch-up displacement in the charge carrier transport channel, particularly the overlap of the wave functions of electrons (or holes) in the channel and at the interface layers, have not been considered. The novelty and specific objectives of the present work are: modifying the Hamiltonian operators based on self-energy (Σ), the retarded Green’s function (G^R), creation (C⁺)/annihilation (C) operators, and the overlapping wave functions of the charge carriers in the gate and substrate systems; obtaining a more complete leakage-current density (J) relationship than the existing relationships; and comparing the electrical characteristics measurement results of five small molecule polymers: PEIE (0.8 nA/cm²), Ps (1 nA/cm²), PFS (2 nA/cm²), ph (4 nA/cm²), PMMA (20 nA/cm²) with previously reported findings. The obtained results can be highly useful for optimizing organic thin-film transistor formulations for potential use in next-generation nanoelectronic devices with lower energy consumption.

A porous wollastonite ceramic with high porosity and low density has been successfully fabricated at low temperature with silicate tailings and electrolytic manganese slag (MS) as primary raw materials in this study. The influences of calcination temperature, SiC, and MS addition amounts on porosity, water adsorption, pore size distribution, bulk density, and bending strength were systematically studied. The results showed that 0.4 wt% of SiC was optimal for the ceramic foaming at a sintering temperature of 1140 °C. The porosity of ceramics reduced from 78.4% to 63.7%, bulk density elevated from 0.96 to 1.13 g/cm³, and bending strength increased from 8.43 to 11.22 MPa as the MS increased from 8.33 wt% to 41.67 wt%. Moreover, the best corrosion resistance performance reached to 99.55% with 8.33 wt% MS content and a sintering temperature of 1160 °C. This work is of significance for the solid waste utilization.

In response to the growing demand for sustainable construction materials, this study overcomes the inherent brittleness and poor fracture resistance of red mud-based geopolymer (RBG) through the strategic combination of surface modified nano-TiO₂ (NT) and sodium polyacrylate (SPA). The NT was functionalized with silane coupling agent to improve dispersibility and interfacial bonding, while SPA was added to enhance fracture toughness. Under the condition of ambient curing, the optimum mixture containing 3 wt% (glycidoxypropyltriethoxysilane)-modified NT (GNT) and 0.5 wt% SPA, which achieved a 28 days compressive strength of 43.40 MPa and a flexural strength of 8.16 MPa. The performance index meets the Portland cement (PC 42.5) standards. Microstructural analyses (XRD, FT-IR and SEM-EDS) revealed that the formation of geopolymer gel was increased, the crystallinity was reduced, and the degree of polymerization was improved, which confirmed the effectiveness of this method in production high-toughness and environmentally friendly geopolymer.

Brucite, diaspore, and limonite, as typical hydroxide minerals, exhibit similar surface properties due to their high content of–OH. This study investigated the effect of traditional anionic collector sodium oleate (NaOL) on the flotation performance and surface properties of brucite, diaspore, and limonite. The flotation experiment results show that adding 40 mg/L NaOL at pH 11 can significantly increase the flotation recovery of brucite compared to diaspore and limonite. The results of contact angle, Zeta potential, and XPS indicate that NaOL can exhibit strong adsorption on the surfaces of the three minerals, but the adsorption effect on the brucite surface of is stronger than that on diaspore and limonite, resulting in differences in floatability among the three minerals. This is mainly due to the weak interlayer interaction force of brucite, which can expose more Mg²⁺ sites during the grinding process, resulting in brucite being able to adsorb more oleate ions. DFT calculations further indicate that sodium oleate has greater adsorption energy on brucite surface and can stably undergo chemical adsorption through covalent bonding between O in the carboxyl group and metal sites on the surface of hydroxides. This study provides molecular level insights into the design of highly efficient selective collectors for metal hydroxide minerals.

The flotation separation of high pyrite content secondary copper ores faces challenges including elevated pH levels, poor xanthate selectivity, and higher costs associated with its combination with Z-200. In this work, a composite thionocarbamate collector (TJ-215), with low-cost raw materials and a short synthetic route, showed a better selectivity for chalcocite than Z-200 when pH>8. Zeta potential analysis indicated a stronger interaction between TJ-215 and chalcocite. These results were achieved through the synergistic coordination of NH—C=S and C=N—OH in TJ-215 molecule, compared with the single thiourea group, NH—C=S, in Z-200 molecule. At low-alkaline condition, the NH—C=S in TJ-215 formed Cu—S, Cu—N bonds with Cu atoms, and the C=N—OH combined with Cu to form a Cu—O bond. The results of this study provide guidance on the replacement of Z-200 by TJ-215 in the separation of chalcocite from pyrite in weak alkaline conditions.

Graphite has the potential to mediate the reduction process of Cr(VI) by oxalic acid (OA), but a reasonable modification is required to enhance the mediation of electron transfer. In this study, biosynthetic Schwertmannite (Sch) modified graphite (Sch@G) was pyrolyzed at 700°C for Cr(VI) remediation. Biosynthetic Sch particles were successfully loaded on the graphite, providing high specific surface area and abundant O-containing functional groups. The removal efficiency of Cr(VI) reached 90.42% within 60 min, facilitated by the synergistic between 1 g/L Sch@G and 1 mmol/L OA. Additionally, the comparative experiments exhibited a significant capacity of Sch@G in a wide pH range (pH 2–10), the removal efficiency was 97.9% within 60 min even at pH 10. Furthermore, the catalyst presented superior environmental adaptability in solutions containing various types of anions (Cl⁻, SO₄²⁻, NO₃⁻, H₂PO₄⁻). Mechanism analysis revealed that the catalyst greatly promotes the transfer of electrons from OA to Cr-contaminants, along with the release of low-valent Fe from Sch, enabling efficient electrons transfer to the Cr-contaminant. Meanwhile, the addition of OA could complex OA-Cr(VI) compound, lowering the activity of Cr(VI) and facilitating the subsequent Cr(VI) removal. Generally, the synergistic effect of the catalyst and OA can form an efficient system that enables rapid and effective remediation of Cr(VI) contamination across a wide pH range. Thus, the catalyst presents as a promising graphite-based biomaterial for the rapid and effective remediation of Cr(VI) contaminants from wastewater.

With the dramatic accumulation of the end-of-life lithium-ion batteries, their recycling is attracting extensive attention worldwide. To address the problem of low lithium recovery in the current typical hydrometallurgy recovery process, this research uses sodium bisulfate as an auxiliary roasting reagent to extract lithium from spent lithium-ion batteries through sulphation roasting, which can enhance the lithium recovery rate significantly. A systematic study of the sulphation roasting process and the mechanisms was carried out with experiments, thermodynamic calculations, and characterization of the roasted sample phases. The results showed that at a roasting temperature of 600 °C, NaHSO₄·H₂O/spent LiNi_xCo_yMn_zO₂ cathode powders (S-NCM) mass ratio of 1.2, and roasting time of 60 min, 95% selective dissolution of lithium was acquired, while the leaching rates of Ni, Co, and Mn were confined under 1%. During roasting, the NCM layered structure collapses and the lithium is transformed into the LiNaSO₄ phase, while the transition metals transform into Ni₆MnO₈ and MnCo₂O₄ phases. The removal of impurity ions from the lithium-rich leaching solution and the generation of Li₂CO₃ were achieved by a combination of thermodynamic calculations and experiments.

Intergrown ferromanganese ore resources are typical strategic mineral resources with huge reserves and abundant hematite, pyrolusite, and other valuable minerals, which is of great significance for its development and utilization. This paper adopts a combination of phase transformation and magnetic separation to explore the phase transformation mechanism of Fe minerals and Mn minerals during the roasting process. The analysis of the properties of the raw ore shows that the Fe-containing and Mn-containing minerals of the intergrown ferromanganese ore are hematite and pyrolusite, respectively. The optimal conditions for controlling the mineral phase were obtained, including roasting temperature of 600 °C for 30 min, and a grinding fineness of <0.074 mm accounting for 50%. Meanwhile, a Fe grade of 61.05% with a recovery of 80.77%, and a Mn grade of 61.60% with a recovery of 87.81% were acquired. The precise mineral phase transformation (MPT) could be realized via adjusting the roasting conditions. Hematite is transformed into magnetite, while pyrolusite is transformed into manganosite, and then they were effectively separated and concentrated via magnetic separation.

To mitigate the detrimental effects of sulfur and enhance the enrichment efficiency of valuable elements in desulfurized diasporic bauxite, the effects of CaO dosage, caustic alkali concentration, reaction temperature and time on the digestion behavior of alumina, sulfur and gallium were illustrated, and the digestion thermodynamics and mechanism were also revealed. During high-temperature Bayer process, alumina and gallium were digested synergistically, while pyrite is digested to S²⁻ and SO₄²⁻. Appropriate CaO dosage promotes the digestion of alumina and gallium, and facilitates the precipitation of sulfur as calcium sulfoaluminate hydrate, effectively removing sulfur from the solution. Excess CaO leads the formation of hydrogarnet, wherein Ga³⁺ incorporates into the crystal lattice by substituting for Al³⁺, reducing the digestion efficiency of gallium. Under the right conditions (CaO dosage = 3%, T = 260°C, t = 60 min, caustic alkali concentration = 260 g·L⁻¹), the corresponding alumina and gallium digestion efficiencies reach 90.82% and 77.58%, respectively, with a significantly reduced sulfur concentration of 1.32g·L⁻¹ in the solution. This work provides theoretical guidance for the efficient co-extraction of alumina and gallium from high-sulfur bauxite via the Bayer process.

Piezoelectric enhanced photocatalytic purification of polluted wastewater is currently one of the better strategies for environmental pollution control. This work proposes a novel and efficient approach for the purification of tetracycline hydrochloride (TC) wastewater via core-shell MoS₂/ZnO heterojunction activated by peroxodisulfate (PDS), where the MoS₂/ZnO heterojunction was fabricated via a hydrothermal route. By exploiting the intrinsic piezoelectric properties of both MoS₂ and ZnO, the heterojunction generates an internal electric field that facilitates the separation of photogenerated electron-hole pairs, thereby accelerating the photocatalytic purification. Under the optimized conditions, the TC purification efficiency can reach 91.2% with the collaborative assistance of PDS activation, and the MoS₂/ZnO heterojunction also exhibited excellent recyclability, maintaining a purification efficiency of 90.76% over five cycles. The MoS₂/ZnO heterojunction demonstrated robust photocatalytic activity under visible-light irradiation and aeration, with the purification kinetics conforming to a pseudo-first-order model. And the purification pathways of TC were systematically investigated, and the dominant reactive oxygen species involved in the process were identified. This work elucidates the underlying piezoelectric-photocatalytic mechanism and provides a sustainable strategy for the efficient removal of antibiotic contaminants from aqueous environments, offering significant potential for practical environmental remediation applications.

Current analytical methods for predicting the lateral deformation of diaphragm walls require complex calculation processes, including numerous parameters with uncertain accuracy, which are difficult to use in practical engineering applications. In this study, we propose a novel analytical approach for calculating diaphragm wall deformation. First, a differential element moment balance method for calculating earth pressure is proposed using a simplified calculation. The excavation effect on the sliding wedge and multiple factors of the ground were considered. Subsequently, the work performed by the earth pressure and internal support structure was calculated. Based on plate theory, a calculation model for the diaphragm wall deformation was established, accounting for the interaction between the ground and internal support structure. Finally, the analytical model was solved using the principle of minimum potential energy and the Ritz method. The proposed method was validated by comparing field measurement data with numerical simulations. A parametric study was conducted to explore the sensitivities of the influencing factors on the lateral deformation of the diaphragm wall, from which a design scheme for the diaphragm wall was presented under the given deformation control standard.

Previous earthquakes indicate that near-source canyon topographic effect (NCTE) can substantially amplify the seismic responses of canyon-crossing bridges (CCBs). While the conventional practices are to make disaster response decisions based on the deterministic approaches, it cannot provide a holistic view regarding the impacts of uncertainties of ground motions on CCBs. Thus, this study adopts the performance-based assessment in a probabilistic framework to evaluate the seismic fragility of CCBs considering NCTE. For this purpose, a numerical model of a typical tall-pier CCB across a V-shaped canyon is constructed using the OpenSees. Eighteen ground motions combined with NCTE are simulated using the region-matching method. PGA, Sa(T1), and PGV are compared to determine the optimal intensity measure (IM). The probabilistic seismic demand models and fragility curves are constructed. The results show that PGV is the optimal IM for ground motions considering NCTE. The NCTE can significantly increase the damage probability of CCBs. The damage probability of the side bearing is the most sensitive to NCTE among the vulnerable components. The side pier bearings and the side piers on the illuminated canyon side are the most vulnerable components in cases with and without consideration of NCTE, respectively.

To reduce the subjectivity of conventional instability criteria in deep rock engineering, this study develops an energy-driven criterion grounded in cusp catastrophe theory and embeds it within an improved nonlinear Hoek-Brown (H-B) strength-reduction framework. We derive an explicit algebraic transformation that maps a quartic energy potential to the standard cusp form and introduce the mutation eigenvalue Δ as a physically interpretable measure of proximity to the vanishing of the energy barrier. Building on this, failure staging is diagnosed in practice by the concurrence of a slope mutation in displacement-reduction-factor curves, a threshold jump of total plastic strain-energy increment typically exceeding threefold between adjacent reduction steps, and video-confirmed crack through-connection. Integrating Δ with the nonlinear reduction scheme yields reproducible integral safety factors. Two representative cavern layouts (Model A/B) are validated by scaled physical model tests and companion simulations: global failure occurs at K_S=2.33 (A) and K_S=2.73 (B), with relative deviations from tests (2.30 and 2.90) of +1.3% and −5.9%, respectively, coinciding with the energy-jump threshold and the multi-evidence diagnosis. Compared with the equivalent Mohr-Coulomb parameter approach, the improved nonlinear scheme produces smaller (more conservative) safety factors by 5.7% and 2.5%, while better matching the observed destabilization process. The framework clarifies the role of Δ as an energy-based instability indicator and offers a practical, verifiable criterion for cavern stability assessment.

In deep underground engineering, rock brittleness is closely associated with rockburst and feasibility of hydraulic fracturing. The loading rate plays a crucial role in determining the severity of rockburst and cuttability. By conducting uniaxial compression tests and single-cycle loading-unloading experiments, the brittle evolution of four types of granite under different loading rates was investigated. During the uniaxial compression process, acoustic emission parameters were used to characterize the crack evolution patterns. Additionally, the macroscopic failure process of the specimens and the post-failure rock fragments were recorded with a high-speed camera, providing multi-scale validation. This study proposes a quantitative brittleness index based on rock fracture energy, and its validity is verified by analyzing the rock failure process and the macroscopic characteristics of rock fragments.: This work contributes to advancing research on rock brittleness indices considering the coupling between energy evolution and kinematic mechanisms. The research results indicate that as the loading rate increases from 0.1 mm/min to 5 mm/min, the quantitative evaluation index (B_s) for brittleness increases from 0.17 to 0.28, while the qualitative evaluation indices M_F (projectile mass ratio) and $\overline{l}$ (average lumpiness) increase from 0.3261 to 0.4184 and from 32.96 mm to 38.12 mm, respectively. With increasing loading rates, the brittleness of the rock increases significantly. A series of qualitative and quantitative results, including fractal characteristics and acoustic emission parameters, reveal the crack evolution patterns of granite under different loading rates and confirm the rationality of the brittleness index. This study provides theoretical guidance for practical deep underground engineering applications.

Studying the fracture behavior of rock-concrete interface (RCI) of various lithologies under temperature and loading is crucial for the safety of structural systems involving these interfaces. In this study, the implications of temperature and interface strength factor (ISF) on the fracture mechanics of rock-concrete composite specimens with varying lithologies were studied using three-point bending numerical experiments with rock-concrete bi-material (RCB) notched semi-circular bending (NSCB) specimens. The findings indicate that the fracture toughness (K_IC) and fracture energy (G_f) of RCI with various lithologies are negatively correlated with temperature, and SCI is most significantly affected by temperature. Meanwhile, at higher temperatures, the K_IC and G_f of RCI exhibited lower sensitivity to the ISF, indicating that the failure of the specimen was driven by thermal effects. Furthermore, the length of the fracture process zone (r_c) of the RCB specimens of varying lithologies exhibited a linear increasing trend with increasing temperature. This phenomenon indicates a transition from brittle to ductile materials. This study provides critical insights for ensuring the long-term safety and enhancing the disaster resilience of major infrastructure in extreme environments.

Layered rock masses represent complex geological formations characterized by pronounced anisotropy in strength. This study monitors stress/deformation during construction to summarize layered rock mass deformation and support stress characteristics based on Yunwushan Tunnel. Shale shows greater vault settlement and asymmetric support deformation than sandstone. The excavation was optimized by establishing a numerical model, analyzing the advanced support effect, and redesigning the anchor rod to control the asymmetric large deformation. The results show that: 1) It is effective to set a transition section before the sudden change of rock mass, and the optimal distance for setting the transition section is 6 m. 2) The implementation of advance small pipe support has been shown to effectively mitigate settlement in the tunnel arch, whereas anchor bolt support is effective in controlling the horizontal convergence of the surrounding rock. 3) Adjusting the angle of the anchor bolt is a cost-effective reinforcement method when facing asymmetric deformation. 4) It is recommended to flexibly adjust the angle of the anchor bolts and increase the advance small pipe support in mountain tunnel projects under the transformation of rock strata. These outcomes may serve as a valuable reference for the design and construction of similar engineering projects.

Affected by the depositional environment, coal seams in the weathered and oxidized zone and their overlying strata are characterized by developed fractures and poor self-stability, leading to difficulties in roadway and working face roof management. This paper analyzes the failure characteristics of coal-rock masses in this zone. Combined with model tests and numerical simulation methods, it investigates the stress distribution status, deformation-failure characteristics, and movement-fracture laws of the overlying strata in a fully mechanized top-coal caving working face. The results indicate: (1) Weathering and oxidation significantly degrade strength and increase plastic deformation in coal-rock masses; (2) Under mining-induced disturbance, overlying strata stress is released from the in-situ state and sharply reduced, forming stress concentration zones ahead of the coal wall and at face ends; (3) During mining, fractures propagating upwards from the coal wall trigger rib spalling and top-coal collapse, forming combined cantilever and articulated rock beam structures. The overlying strata sequentially undergo four deformation-failure stages: “bed separation, immediate roof fracture, main roof fracture, and high-level strata collapse”. The research findings can provide a basis for the safe mining of fully mechanized top-coal caving faces in weathered and oxidized coal.

The development of coalbed methane in China is constrained by complex geological conditions characterized by low permeability, low saturation, low reservoir pressure, and high adsorption (“three lows and one high”), posing significant challenges to its efficient development. The liquid nitrogen-induced fracturing and permeability enhancement technology can effectively promote the expansion and connection of macroscopic and microscopic fractures, thereby improving the permeability of coal seams. In this study, industrial micro-CT scanning technology, the VRA-UNet method, and fractal dimension calculation methods are employed to conduct an in-depth analysis of the action mechanism of liquid nitrogen cold soaking on the fracture structure of coal bodies with different metamorphism degrees. The results indicate that liquid nitrogen cold soaking promotes the generation, expansion, and connection of new fractures inside coal bodies to form fracture networks. Via Matlab programming and VG Studio MAX image analysis software, fracture extraction and calculation are performed on CT-scanned coal samples; it is statistically found that the quantitative fracture indices of coal increase after liquid nitrogen cold soaking. Compared with the fracture spectrum peak proportions of raw coal samples, the fracture spectrum peak proportions of anthracite, bituminous coal, and lignite increase by 8.375%, 12.680%, and 79.939% respectively after liquid nitrogen cold soaking. By combining the VRA-UNet method for coal fracture identification, the box-counting method is used to calculate that the fractal dimension of coal fractures after liquid nitrogen cold soaking is larger than that of raw coal samples. The research findings of this paper will provide theoretical and technical support for the efficient development of coalbed methane and the improvement of coal seam gas extraction rates.

Aiming at the problem of large deformation of arch shoulder in deep high stress roadway of Hudi Coal Mine, through field sampling, experimental test and numerical simulation, the deformation mechanism of arch shoulder under the coupling action of high stress, soft and hard rock strata of roof, weakening of surrounding rock and disturbance of space staggered roadway was revealed. Through the research results, the high stress increases the range of the plastic zone, and the soft and hard rock strata lead to the change of the expansion form of the plastic zone. With the decrease of the vertical distance of the space staggered roadway, the insufficient bearing capacity of the supporting material and other factors lead to the increase of the deformation of the shoulder angle and the side, forming the deformation characteristics of the arch shoulder. Based on this, the active and passive collaborative control technology is proposed, and the targeted support concept of “unloading control + strong support + collaborative” is adopted. The optimization scheme controls the deformation of roadway within 8% of the section size, significantly reduces the range of plastic zone, effectively solves the problem of difficult support of arch shoulder deformation.

This study integrates true triaxial hydraulic fracturing experiments with finite-discrete element method (FDEM) numerical simulation to systematically investigate the control mechanisms of interface strength and inclination angle on hydraulic fracture propagation in coal measure strata under different in-situ stress conditions. The results indicate that the fracture propagation path at the rock interface is jointly controlled by the interface strength coefficient (η), the interface inclination angle (θ), and the vertical stress difference coefficient (k). When fractures propagate from soft rock to hard rock, the interface strength coefficient (η) plays a dominant role. The larger the η, the more likely the hydraulic fracture is to penetrate the interface along the direction of vertical stress. Conversely, when fractures propagate from hard rock to soft rock, vertical stress primarily controls the propagation path. A larger vertical stress difference coefficient promotes interface crossing, while a smaller coefficient tends to cause the fracture to extend laterally along the interface. The interface inclination angle (θ) influences the magnitude and direction of the vertical stress component along the interface. A smaller (θ) facilitates interface penetration by hydraulic fractures, whereas a larger (θ) leads to fracture propagation along the interface. The complexity of the hydraulic fracture network increases with higher (k) and (θ) values. Moreover, the complexity of hydraulic fracture morphology exhibits a non-monotonic trend, initially decreasing and then increasing with rising (k) and (θ). This research provides an important theoretical basis for the design and control of hydraulic fracturing in coal measure strata.

This study establishes a nonlinear vehicle–track coupled dynamic model that explicitly accounts for the effects of substructure deformation. Based on the vehicle–track coupled dynamics framework, the track structure is modeled using an energy-based approach, in which displacement functions of track layers are expanded into modified Fourier series. The static rail geometry and interlayer contact relations are derived through the principle of stationary potential energy. Considering the dynamic excitation from moving trains, a cross-iterative algorithm is employed to obtain the system responses, thereby enabling unified analysis of static track deformation and dynamic vehicle–track interactions. The results demonstrate that the proposed model effectively reveals the coupling mechanism between substructure deformation parameters, rail surface geometry, and system dynamics. The critical conditions for avoiding void formation under cosine-type and angular-type subgrade settlements follow power-law and linear relations, respectively. For a cosine-type settlement with a wavelength of 15m and amplitude exceeding 35mm, vehicle ride quality deteriorates significantly. Moreover, interlayer separation induced by substructure deformation leads to repeated “contact–separation–recontact” impacts, which may degrade long-term structural performance. This study provides a unified theoretical and computational framework for quantitatively assessing the effects of substructure deformation on high-speed train safety and track structure durability.