Deep coal mining has become increasingly routine, and its complex geomechanical environment has led to higher intensity and frequency of rock bursts and coal and gas outbursts, while also resulting in more diverse disaster types, with their coupling giving rise to more destructive compound disasters. Therefore, investigating and elucidating the disaster-causing mechanisms of coal-rock-gas compound disasters, developing effective monitoring and early-warning systems, and exploring novel mitigation technologies are crucial for ensuring safe and efficient mine operations. This study systematically reviews the research progress and current status of coal-rock-gas compound disasters, comprehensively analyzes and summarizes three primary controlling factors influencing compound disasters: objective factors, anthropogenic factors, and natural factors. Based on the driving force sources, triggering and transformation sequence, and duration, the disaster formation model of coal-rock-gas compound disasters is refined. The full-cycle incubation and evolution process of coal-rock-gas compound disasters is dissected, and the inducing and transformation mechanisms underlying their occurrence are revealed, and the occurrence thresholds of compound disasters are defined. Based on the evolution patterns of overlying strata structures and gas distribution characteristics, coal-rock-gas compound disasters are classified into impact-induced outburst type and outburst-induced impact type. The study comprehensively describes the multi-source monitoring approaches for coal-rock-gas compound disasters, as well as a multi-parameter integrated early-warning system. A technical system integrating regional prevention and local risk mitigation for outburst elimination and rockburst pressure reduction is summarized, and a novel concept of compound disaster prevention and control based on structural regulation is proposed. The study discusses key technical challenges in the research on coal-rock-gas compound disasters, such as multi-field coupling mechanism studies, development of similar materials, refined geological exploration and modeling, optimization of monitoring and early-warning models, and exploration of novel prevention and control technologies, with the aim of further advancing research in the field of coal-rock-gas compound disasters, thereby ensuring the safe and efficient extraction of deep coal resources.

The evaluation of the hot workability and applying it to hot rolling process are crucial for the optimization of microstructure of steel. In this study, the hot workability of Q1100 steel was studied by a combination of hot compression tests, hot rolling application, and microstructure characterization. The results show that the established recrystallization kinetic models can effectively predict stress variation during hot deformation. The calculated DRX volume fraction is positively related to deformation temperature, and negatively related to the strain rate and Zener-Hollomon parameter. Then the relationship between hot working parameters and microstructure evolution was established by drawing the hot processing maps. The hot processing maps were further applied to hot rolling. When the steel is rolled inside the optimum hot processing window, the macroscopic surface of the steel plate is relatively flat, and its microstructure is mainly composed of continuous dynamic recrystallization (CDRX) grains. The orientation difference between CDRX grains and the adjacent grains is small. When the steel is rolled inside the flow instability region, cracks appear on the macroscopic surface, and the microstructure includes deformed grains and discontinuous dynamic recrystallization (DDRX) grains. The DDRX grains have a large orientation difference with adjacent grains.

High-entropy alloy (HEA) coatings can effectively improve the wear properties of light alloys. CeO₂ and Y₂O₃ are two common rare-earth oxides that are often used as dopants to modify the structure and properties of the HEA coatings. In this paper, the HEA coatings of undoped (H₀), doped with CeO₂ (H₁), Y₂O₃ (H₂), and CeO₂+Y₂O₃ (H₃) were prepared by extremely high-speed laser cladding (EHLC). The effects of rare-earth biphasic particles and their synergistic effects on the microstructure and wear properties of the coatings were investigated. The results show that single CeO₂/Y₂O₃ doping can effectively improve the body-centered cubic (BCC) phase content and refine the grain structure of the coating, but when CeO₂ and Y₂O₃ are co-doped, the BCC phase content of the coating can be improved more significantly, and the grain refinement is more obvious. Furthermore, the synergistic action of CeO₂ and Y₂O₃ in the H₃ coating resulted in a significant enhancement of the effects of solid solution strengthening, lattice distortion, and fine-grain strengthening within the microstructure. This resulted in a substantial increase in the microhardness of the H₃ coating, reaching 970.36HV, with a wear rate of merely 1.87×10⁻⁵ mm³/(N·mm). In comparison with the H₀, H₁, and H₂ coatings, the hardness increased by 1.54 times, 1.51 times, and 1.26 times, respectively. Concurrently, the wear rates decreased by 15.77%, 12.83%, and 11.23%, respectively. The primary wear mechanisms observed in the coatings include abrasive wear, adhesive wear, and oxidative wear.

In order to further improve the degradation resistance and osteogenic property of the micro arc oxidation (MAO) coating of Mg alloys, the Mg alloy samples were oxidized in phosphate electrolyte, silicate electrolyte, first phosphate electrolyte + second silicate electrolyte, and first silicate electrolyte + second phosphate electrolyte. And the corrosion resistance, cytotoxicity, and osteogenic property of the samples were studied. The results showed that the Na₂SiO₃-MAO coated sample had more micropores than the CaP-MAO coated sample. The composite micro-arc oxidation (MAO) coatings obviously improved the degradation resistance of the alloy. Moreover, the samples fabricated first in silicate electrolyte and then in phosphate electrolyte showed the best corrosion resistance with the corrosion current density of only 0.1 µA/cm², which was two orders of magnitude lower than the single silicate Na₂SiO₃-MAO coated (10.9 µA/cm²). Besides, the cytocompatibility of the MAO coated samples was good, presenting no cell toxicity. The extract from the Na₂SiO₃+CaP coated sample promoted cell proliferation, reaching almost 100% after 5 d. Na₂SiO₃+CaP coated sample showed the best osteogenic property with bone volume/total volume (BV/TV) about 55% after 8 weeks implantation in calvarial region (parietal bone) of the skull. The results indicated that the Na₂SiO₃+CaP coated magnesium alloy exhibited the best corrosion resistance and osteogenic property.

Stretchable polymer semiconductor film (SPSF) is the core to fabricate the flexible optoelectronic devices, due to its excellent strain-tolerance capacity. Softness of polymer chain realized via introducing flexible segment at the backbone and side-substituents is the effective strategy to obtain SPSFs, but easily causing the relatively instable film morphology and weak energy dissipation ability. Herein, we proposed a convenient side-chain cross-linked strategy to prepare the stretchable SPSF with an outstanding morphological stability for flexible polymer light-emitting diodes (PLED). Styrene group is introduced as ended cross-linking unit into the side chain of fluorene to prepare the intrinsically stretchable alter-copolymers semiconductors poly(9, 9-diphenyl-4-((6-(4-vinylphenoxy)hexyl)oxy)-9H-fluorene)-alt-(1,8-bis(4-phenoxy)octane) (PCm-alt-C8). Interestingly, PCm-alt-C8 cross-linked film easily obtained via thermal treatment at 180 °C, had stable morphology, excellent solvent resistance and deep-blue emission simultaneously. Compared to the controlled PEt-alt-C8, PCm-alt-C8 cross-linked films also present an excellent strain-tolerance capacity with larger crack initiation strain rates and the elongation at break (both enhanced by about 90%). More important, stretchable PCm-alt-C8 cross-linked films showed a stable electroluminescent and electrical property with large stretching degree (>30%) and hundreds of cycles of cycling stretch deformations, suggesting their excellent strain-tolerance capacity. Therefore, side-chain cross-linking is a universal strategy for the preparation of high-performance SPSF in flexible optoelectronics.

The scattered metal germanium (Ge) often exists in sphalerite via multiple substitution mechanisms, forming Ge-bearing sphalerite. This paper aims to investigate the effects of four different Ge substitution mechanisms on the crystal structure and electronic properties of sphalerite using density functional theory (DFT), namely: (1) Zn²⁺↔Ge²⁺, (2) 2Zn²⁺↔Ge⁴⁺+vacancy, (3) 3Zn²⁺↔Ge⁴⁺+2Cu⁺, and (4) 3Zn²⁺↔Ge⁴⁺+Fe²⁺+vacancy. The results indicate that the four forms of Ge substitution mechanisms introduce impurity energy levels into the forbidden band interval of sphalerite, leading to a significant decrease in band gap and an enhancement of electrical conductivity. And the impurity energy levels are mainly contributed by atomic orbitals of Ge 4s, Cu 3d, and Fe 3d. The Ge—S bonds in (1)-type Ge-bearing sphalerite exhibit weak covalency, while those in the other three types of Ge-bearing sphalerite show significantly stronger covalency. Frontier orbital analysis suggests that all four forms of Ge substitution mechanisms enhance the interaction between sphalerite and butyl xanthate, with the order of interaction intensity being: (4)-type>(3)-type>(2)-type >(1)-type≈ideal sphalerite.

Simultaneously preparing sodium silicate solution with high modulus and obtaining aluminum concentrate with high Al/Si ratio from activated roasting clinker is the key to a new method for clean utilization of coal fly ash. This study systematically investigates the leaching mechanism of SiO₂ from activated roasting clinker in sodium silicate solution and proposes an optimized leaching process. The colloidal particles formed by the condensation of siloxane groups increase the diffusion resistance of the leaching agent in the capillary pores, and the SiO₂ deep inside the pores is difficult to contact with the leaching agent, which is an important reason for the insufficient leaching of SiO₂ in high-modulus sodium silicate solution. A two-stage countercurrent leaching process proposed can simultaneously prepare sodium silicate solution with modulus greater than 2.5 and aluminum concentrate with high Al/Si ratio exceeding 11. This work provides a potential application solution for the development of clean and economically feasible technologies for the utilization of fly ash.

Distillation temperature, as a pivotal thermodynamic parameter in vacuum purification of metals, governs impurity migration through volatility-stratified mechanisms. This study establishes theoretical distribution models for high-volatility (Na and Se), medium-volatility (Fe and Cu), and low-volatility (Ni and Cr) impurities, revealing dual-threshold effects on impurity removal: low-to-medium temperatures (≤550 °C) effectively suppress volatilization, while elevated temperatures promote co-evaporation. At the optimal 550 °C, tellurium purity reaches 5N8 with >90% yield. Spatial fractionation analysis demonstrates high-volatility impurities enriching in the upper condensation zone (X/L<0.25), whereas medium/low-volatility impurities accumulate in the lower zone and residues. Remarkably, residual impurities show significant enrichment versus raw materials—Na 4.04 times, Fe 13.3 times, Cu 53.6 times, Ni 7.17 times, and Cr 15.12 times, through formation of non-volatile compounds/solid solutions. Temperature-space coupling effects drive distinct deviation patterns: fluctuations in high-volatility impurities vs. temperature-progressive deviations in medium/low-volatility species. The impurity concentration of model-experiment deviations (mean±SD) are quantified as: Se 0.265±0.12, Na 0.224±0.02, Cu 0.146±0.06, Fe 0.133±0.13, Cr 0.101±0.07, and Ni 0.122±0.08.

Rock failure is accompanied by abnormal stress accumulation and sudden release. However, the invisible internal structure and complex stress environment make it challenging to effectively capture temporal precursors and spatial distribution of stress mutation in the failure process. This paper integrates acoustic emission (AE), traveltime tomography, and critical slowing down theory as a method for investigating granite failure under biaxial compression. The proposed method is applied to monitor the spatial-temporal evolution of stress and identify precursors to stress mutations during rock failure. It not only can investigate expansion trend of micro-cracks and reveal stress evolution patterns through velocity, but also can characterize temporal precursors and spatial distribution of stress mutation. Experiment results show: (1) Traveltime tomography reveals stress-velocity correlations that velocity increases (crack closure/elastic stages) reflect micro-crack compaction and stress concentration, while velocity decreases (stable/unstable stages) indicate fracture propagation; (2) Intermediate principal stress critically modulates these patterns that higher intermediate principal stress amplifies early-stage velocity heterogeneity (local stress concentration) but induces premature micro-fracturing in elastic stages (local velocity drops), resulting in diminished overall velocity changes; (3) Autocorrelation coefficient and spatial variance effectively characterize stress mutation thresholds in time- and space-domain respectively. The autocorrelation coefficient detects critical slowing phenomena prior to instability, while spatial variance pinpoints stress anomaly localization. These indexes provide earlier warnings than conventional AE rate thresholds, validated by spatial-temporal alignment with macroscopic fractures. The proposed method enhances real-time monitoring of stress redistribution, offering technical support for early warning and risk mitigation in deep mining engineering.

The surrounding rock of the gob-side entry driving (GSED) is subjected to multiple high ground pressure effects in extra-thick coal seams, resulting in severe damage and significant control challenges. This study proposes a novel technology of cutting periodically fractured key blocks (CPFKB) to relieve pressure on the surrounding rock. The mechanism of CPFKB in mitigating ground pressure is elucidated, and an analytical model is built. Meanwhile, a discrimination method is given for determining the scientific parameters of CPFKB and when and in which form they fall into a gob. The results indicate that severed blocks exhibit four instability modes: sliding instability, rotational instability, simultaneous rotational-sliding instability, and stable hinge. Cutting angle exerts a significant influence on interfacial stress of severed blocks. Low-inclination cutting angles tend to induce simultaneous rotational-sliding instability, while high-inclination cutting angles typically result in initial rotation followed by sliding instability. The probability of instability markedly increases during mid-to-late stages of rotation compared to early phases. The GSED with narrow coal pillars in extra-thick coal seams using longwall top-coal caving mining is conducive to the implementation of CPFKB. Furthermore, a hydraulic fracturing technique with 75° cutting angle for CPFKB is introduced, and it achieves good practical results.

With increasing mining depth in metal mines, the stability of roadway support structures is significantly affected by the complex surrounding rock. This study performs biaxial compression and bolt pull-out experiments on anchorage body specimens with different structural plane dip angles to explore failure mechanisms of anchorage structures and evolutionary law of bolt anchorage force. Results show the dip angle notably impacts the bearing capacity and failure modes of anchorage specimens. Their peak stress exhibits a V-shaped trend: decreasing from 54.80 MPa to 19.65 MPa as dip angles increase from 0° to 45°, with failure mode transitioning from tensile to shear; at 60°, it becomes a tensile-dominated mixed mode. Bolt anchoring significantly enhances bearing capacity (most remarkably by 153.22% at 45°) and changes failure from brittle to ductile. Pull-out tests reveal two failure modes: slip at the bolt-rock interface and bolt fracture. At 45°, bolt fracture occurs under a 14.55 kN peak pull-out load, matching the bolt’s yield strength. This failure mechanism involves two key factors: structural plane sliding that shears the bolt, and mechanical interlocking that restricts pull-out, substantially increasing anchorage force. These findings provide insights for stability assessment and support design of roadway structures in complex geological environments.

Due to the unique geological structure in the Guizhou region, issues such as stress concentration and inefficient resource utilization efficiency arise during repeated mining of close-distance coal seam. This study focuses on the Longfeng Coal Mine in Guizhou, investigating the evolution of stress arches and abutment pressure distribution under repeated mining conditions through similarity simulations, numerical simulations, and theoretical analysis. The study introduces a novel composite stress arch model, which more accurately represents stress evolution under complex mining conditions compared to traditional single arch theories. The model highlights the gradual transformation of a single stress arch into a composite structure, accounting for the increasing complexity of the stress distribution. Based on these evolution characteristics, a mechanical model of composite arches under nonlinear loading was developed. The calculation results and field monitoring data show that after repeated mining, the stop-mining coal pillar width should be optimized between 65 and 70 m. The research reveals the coupling relationship between the evolution of composite arches and the distribution of abutment pressure, which aids in optimizing coal pillar design, enhancing resource recovery rates, and ensuring the stability of roadways and stopes.

Hot-stage polarizing microscopy technique was employed to investigate the mesoscopic fracture evolution characteristics of granite throughout the entire process from room temperature to real-time high temperature and then to cooling. The study analyzed the influence of mineral types, temperature, cooling medium, and the heating and cooling progress on the microcrack development in granite. Additionally, the contributions of heating and cooling to the damage of granite were discussed. The research indicates that crack evolution follows a characteristic trend: the number of small cracks increases, and larger cracks form through the coalescence and propagation of smaller ones during heating. The thermal fracture threshold for granite was identified at 300 °C. The three main minerals in granite exhibit distinct area change behaviors with temperature. After natural cooling, mineral areas show a slight increase compared to the pre-treatment state. Following thermal shock in water, these areas decrease marginally relative to their extent at 600 °C yet remain significantly larger values than initial ones. Thermal shock cooling induces more extensive fracturing in granite compared to natural air cooling. Furthermore, the heating process contributes more significantly to the overall damage than the subsequent cooling stage. This study enhances the understanding of mesoscopic evolution in thermal disturbances treated rocks and provides a theoretical basis for assessing rock stability in high-temperature engineering environments.

To investigate the influence of different Talbot grading indices (n-values) on the fatigue damage deterioration and instability behavior of grouted reinforcement body, an increasing-amplitude fatigue loading test was conducted on grouted reinforcement specimens with different n-values using the multi-functional electro-hydraulic servo-controlled rigidity test system (MTS-815). Acoustic emission (AE) technology was employed to monitor the entire testing process. The fatigue mechanical response mechanism, AE characteristic parameters, and damage modes were analyzed. The results demonstrate that as n-value increases, the mechanical characteristics of the specimens initially increase and then decrease. AE parameters, including the cumulative AE ring counts and energy counts, follow the same trend, and spectral characteristics exhibit a strong correlation with crack evolution. The cumulative AE ring counts damage model reveals a three-phase behavior for the specimens under different n-values. The b-value, which characterizes the scale distribution of cracking events, correlates with the volumetric strain growth rate, showing a more sensitive response. Differences in n-values directly affect the distribution of RA/AF signals and damage modes. The findings provide valuable insights into predicting the destabilization of grouted reinforcement specimens under fatigue disturbance and offer necessary theoretical support for the design and stability control of excavation in fragmented surrounding rock.

With the continual deterioration of mining conditions, the deformation and failure of surrounding rock in roadways with weak roofs under intense mine pressure during close-distance coal seam extraction has become a critical issue restricting the safe and efficient mining of coal. To address the issue of increased surrounding rock damage caused by blasting pressure relief in such roadways, this study proposes an innovative non-explosive method for roof cutting and pressure relief with dense drilling (RCPRDD) to protect the roadway. A combined approach of laboratory experiments, theoretical analysis, numerical simulation, and field testing was employed to clarify the rock weakening effects and mechanisms induced by dense drilling. An optimal design method for drilling diameter and spacing was established, and the effectiveness of this method was validated. The research results indicate that the degree of rock weakening induced by dense drilling is primarily related to the drilling density coefficient. As the drilling density coefficient increases, the rock weakening effect becomes more pronounced. At the same time, dense drilling exerts a significant amplifying effect on the tensile stress experienced by the side roof of the roadway goaf. A functional relationship between the dense drilling weakening coefficient and the drilling density coefficient was established, providing a theoretical basis for the selection of key parameters for dense drilling. The method was ultimately implemented in a field engineering test, effectively reducing the stress in the coal body of the advanced roadway, controlling the deformation and failure of the surrounding rock, and achieving the goal of protecting the roadway. This demonstrated the feasibility and effectiveness of the RCPRDD. The research findings provide a scientific basis for controlling roadway deformation under similar conditions.

Microwave fracturing offers significant potential for efficient hard rock fragmentation. This study investigates real-time heating and fracture characteristics of ten granitoid minerals under 2 kW microwave irradiation for 3 min. Chlorite, amphibole, and altered plagioclase were identified as highly microwave-sensitive, exhibiting high mass and P-wave velocity decay, rapid heating rates (>2.5 °C/s) and violent rupture. Mineral surface temperature non-uniformity, quantified by the coefficient of variation (V_T), evolved through distinct increasing, decreasing, and stabilizing phases, reflecting shifts in dominance between heat accumulation and transfer. Temperature gradients revealed the spatial relationship between hotspots and rupture points, with shallow melting influencing surface temperature distribution. Undamaged minerals exhibited significant temperature gradient spatiotemporal variability but ultimately stabilizing. These results enable prediction of microwave heating behavior in hard rocks containing analogous minerals and enhance our understanding of microwave-induced weakening mechanisms.

Precise differential travel-time measurement is essential for earthquake relative locating. The waveform cross-correlation (WCC) technique is widely regarded as the most effective method for calculating the differential travel-time of seismic phases. However, for earthquake pairs with large magnitude differences, substantial biases can arise due to disparities in the duration of the initial pulse, potentially leading to significant mislocations, particularly for mainshocks. To overcome this limitation, we propose to use the dynamic time warping (DTW) algorithm to optimize differential travel-time calculation. Using high-quality earthquake waveform data from the San Andreas Fault (2012–2019), we systematically compared the performance of DTW and WCC, respectively. Our results demonstrate that DTW substantially improves differential travel-time measurements, especially in cases involving large magnitude differences. In addition, we tested the robustness of DTW using noisy seismic data, demonstrating its superior resilience to noise.

With the evolution of geophysical surveys from traditional two-dimensional (2D) to three-dimensional (3D) models, the resulting large data volumes pose significant challenges to inversion, particularly when resolving large-scale 3D structures. A direct solver for solving an ill-conditioned linear system resulting from the finite-difference approximation of a boundary value problem requires more memory and time than iterative solvers. To overcome this limitation, an efficient iterative solver for 3D finite-difference approach is introduced to calculate the 3D gravitational potential and the associated gravitational field. Firstly, the boundary value problem associated with 3D gravitational potential is discretized using central finite-difference technique based on right rectangular prismatic grids. The resulting large unsymmetric sparse systems are then solved using the generalized minimal residual algorithm (GMRES) iterative solver in combination with incomplete LU factorization. Secondly, to obtain high-accuracy partial derivatives of gravitational potential, a high-degree Lagrange interpolation scheme is employed. Finally, three density models are applied to test the accuracy, reliability, and flexibility of our 3D finite-difference algorithm. All computational results demonstrate that our method provides an accurate approximation of the gravitational field and is applicable to 3D forward modeling.

The tunnel face stability is investigated in inclined layered soils under steady unsaturated seepage and seismic loading. The rigorous estimate of the maximum face pressure is provided during tunnel excavation. The modified pseudo-dynamic method is applied to capture the spatial and temporal characteristics of seismic forces. A spatial distribution formula for suction stress under steady seepage conditions is derived for inclined layered soils. The study examines how inclined stratification influences the shape of failure mechanisms, the suction head profile, and variations in seismic acceleration. The spatial and temporal changes in suction stress and seismic loading are integrated into the energy equilibrium formulation based on a three-dimensional discretized failure model, and the critical face support pressure can be calculated via an integrated optimization strategy. The distributions of seismic acceleration ratios are obtained under various dynamic parameter conditions and the spatial variation of suction stress in the soil ahead of the tunnel face under different hydraulic hysteresis scenarios. The proposed analytical approach is compared with previous research, and the differences in results under different representations of seismic waves are also discussed. The research results can provide a valid framework to evaluate the influence of seismic excitation, steady-unsaturated infiltration, hydraulic hysteresis, and inclined stratification on tunnel face stability.

This study analyzed the interaction between sequentially installed combined support systems and the surrounding rock. Six distinct forms of elastic-brittle-plastic rock masses with reinforcement were analyzed, along with the critical displacements that governed their transition behaviors. Virtual support pressure was introduced to assess the spatial influence of the tunnel face. It was determined by integrating the longitudinal displacement profile with the proposed ground characteristic curve solutions under various ground conditions. Considering the timing of support installation, the support-rock interaction was divided into three phases. A method was presented to determine the evolution of this interaction based on critical displacements. An analytical approach was further proposed to describe the complete process of support system-rock interaction using displacement coordination. The analytical results are validated against numerical simulations and field measurements, and the method’s advantages are demonstrated through comparisons with existing models and the convergence-confinement approach. Finally, the effects of surrounding rock and support parameters are examined. The results indicate that residual cohesion, the friction angle of reinforced ground, and reinforcement thickness strongly influence tunnel behavior. Additionally, increasing the stiffness or advancing the installation of secondary support substantially raises secondary support pressure.

The periodic fluctuations in water levels in reservoir areas subject slope rocks to both wet-dry cycles and cyclic shear stresses. Understanding the deterioration mechanisms of rocks under these conditions is crucial for ensuring their long-term stability. In this study, limestone samples were collected from the site, then mechanical tests and acoustic emission (AE) were conducted. The multifractal detrended fluctuation analysis (MF-DFA) was used to analyze the AE time series of the samples. The results indicate that the primary causes of decreased shear strength are the shearing of micro-asperities on the sample surface under cyclic shear, and the erosion of soluble mineral crystals under wet-dry cycles. The MF-DFA spectra revealed that the frequency of frictional damage events exceeded that of micro-asperity shear failures. Wet-dry cycles were found to decrease shear strength primarily by facilitating the shearing of existing micro-asperities, while their capacity to generate new micro-asperities was weak. The MF-DFA characteristics with time of AE can serve as an early warning indicator of sample deformation and failure. Compared to existing methods, this approach exhibits better early warning performance. The findings provide valuable insights for the assessment and early warning of long-term stability of geotechnical bodies in reservoir areas.

The impact of repeated low-temperature thermal cycles on dolomite rock’s thermomechanical behavior was examined, with a focus on how loading mode and cycle number (N) affect its properties. Dolomite samples were subjected to 0, 50, 100, and 500 thermal cycles, with fluctuations between 20 and 60 °C being applied. Tensile strength, fracture toughness, elastic modulus, fracture velocity, and ultrasonic wave speeds were measured before and after the thermal cycles. An initial improvement in dolomite’s performance was shown, with a peak reached around 336 cycles, followed by deterioration between 336 and 500 cycles. Specifically, increases of approximately 25.11% and 32.5% in pure modes I and II fracture toughness, respectively, were observed at optimal cycle numbers, before a decrease was seen at 500 cycles. Higher elastic modulus, fracture velocity, and acceleration were exhibited by mode II specimens compared to mode I. No phase changes or chemical decomposition within the rock were indicated by X-ray diffraction and chemical analysis. The influence of mineral expansion and microcrack generation on the dolomite’s structure was revealed by ultrasonic wave tests. The findings highlight how temperature fluctuations affect rock masses, which is crucial for understanding dolomite’s vulnerability to damage from thermal stress and loading conditions.

In order to reveal the mechanism of surface hydration differences for different types of montmorillonite crystals, the hydration processes of sodium, potassium, and calcium montmorillonite were simulated by molecular dynamics. These simulation results show that with the increase of the number of water molecules, the interlayer spacing of montmorillonite expands in a step-by-step manner, accompanied by volume expansion, decrease in density, and increase in self-diffusion coefficients of water molecules and cations. In addition, as the water molecular layer accumulates, the peak values of the radial distribution function between Na⁺/K⁺/Ca²⁺ ions and Ow/Hw (oxygen or hydrogen atoms in water molecules) gradually decrease. The degree of polymerization of water intensifies before decreasing, while the elastic modulus and acoustic velocity are gradually decreasing. It is worth noting that Na⁺ ion shows the highest tendency to hydrate, followed by Ca²⁺, and then K⁺. Among the cations studied, Ca²⁺ ion has the highest hydration coordination number, hydration number and hydration radius. As a result, calcium montmorillonite exhibits the widest intensity range and the largest acoustic velocity. These findings can provide references for engineering practices such as oil and gas exploration, tunnel excavation, slope stabilization, and deep geological disposal.

Weak rock-concrete interfaces significantly affect the stability of underground supporting structures. This study aims to investigate the effects of interface inclination on the creep behavior and failure mechanisms of composite specimens. Seven rock-concrete composite specimens with different inclination angles under hydrothermal curing at 60 °C were prepared, and uniaxial and graded loading creep tests were completed. The results show that with increasing interface inclination, the compressive strength of the composite specimens initially decreases and then increases, with the minimum strength observed at inclinations between 60° and 75°. Three typical failure patterns were identified: axial failure, composite failure, and interface failure. The creep failure strength exceeded the uniaxial compressive strength, indicating improved time-dependent deformation resistance under elevated temperature curing. The instantaneous strain initially decreases and then increases as the interface inclination angle grows. Compared to 0° inclination, specimens with 45°, 60°, 75°, and 90° inclinations exhibited reductions in instantaneous strain of 2.64%, 18.84%, 23.29%, and 0.73%, respectively. The steady-state creep rate and creep ratio exhibited a decrease-stabilization-increase trend with increasing stress levels. Creep strain increased with increasing stress levels for all inclinations, with a sharp increase near the failure stage. A nonlinear constitutive model considering interface inclination and creep damage was developed based on damage theory. A nonlinear damage-based constitutive model incorporating interface inclination effects was developed, and its theoretical predictions closely matched the experimental data in all creep stages. These findings provide a quantitative understanding of creep failure mechanisms in rock-concrete interfaces and provide practical references for enhancing the safety of underground support systems.

To simultaneously address low to mid frequency noise absorption and stringent thickness constraints, a novel cross-bridged hex structure with embedded necks was developed from conventional honeycombs. The acoustic performance of these metamaterials was systematically investigated via theoretical analysis, experimental verification, and numerical simulation. Results demonstrate that an exponential 2 penalty factor objective achieves superior uniformity of sound absorption within 500–1000 Hz band, surpassing both average-driven and multi-level reward methods. Among the four tested optimization algorithms, a hybrid CMAES + LBFGS scheme reduced the final penalty by up to 98%, highlighting its capacity for effectively navigating the complex design space of cross-bridged structures.