In order to solve the problem of ambiguity and limitation of application scope in the establishment of safety prevention and control measures for high-temperature tunnel construction, a method of generating prevention and control measures for high-temperature tunnels based on C-CBR is proposed. Firstly, the index system of the cloud case base is constructed for the tunnel high ground temperature and heat damage problem and combined with the analytic hierarchy process(AHP)-entropy weighting method for the comprehensive weighting calculation. Secondly, the cloud historical case base is constructed based on the three basic characteristic indexes of the cloud model, namely expectation, entropy, and hyperentropy, and the principle of case-based reasoning, and the collaborative filtering algorithm is applied to preliminarily filter the historical cases which are in line with the requirements. And then, the cloud model algorithm which integrates the shape-distance is introduced to achieve the integration between target cases and historical case base. Then, the integrated shape-distance cloud model algorithm is introduced to achieve similarity matching between the target cases and the historical case base, to correct the similarity and update the historical case base to generate the optimal similarity prevention and control measures; finally, the optimal similarity prevention and control measures are fully compared with the actual prevention and control measures in the field. The results show that the corrected similarity between the optimal historical case and the target case generated based on C-CBR is 0.746 0, which is a good match, and the the target case similar prevention and control measures are basically in line with the actual prevention and control measures of the project, which makes the generation method more applicable to different tunnels with high ground temperatures under construction.

To explore the potential early warning value of construction safety hazard data and improve the efficiency of hazard identification and control, this study investigated a data-driven approach for the association analysis and early warning strategy of construction safety hazards by integrating text mining, association rule mining, and complex network theory. First, 1 405 construction safety inspection records in 2023 were standardized and dimensionally reduced using text mining techniques, resulting in the extraction of 67 safety hazard features. Then, 70 frequent itemsets and 125 strong association rules were obtained using the Apriori algorithm, and the types of hazard associations were identified. Subsequently, a hazard feature network was constructed based on complex network theory. Key hazard features were identified through structural and node-level indicators, combined with feature modularity analysis. Finally, a feature-driven early warning strategy was proposed. The results show that text mining effectively reduces the dimensionality of unstructured hazard data. The hazard feature network based on association rules successfully reveals hidden associations within the data and enhances the reliability of early warning information, providing clear direction and reference for on-site hazard detection. The early warning strategy helps address the issues of disorder and inefficiency in traditional hazard inspections.

In order to solve the problem of difficulty in determining the number of modes and quadratic penalty factors in the process of variational mode decomposition, a GWO-VMD algorithm was proposed. Based on the Longlong Tunnel gas explosion method construction, an integrated acquisition module was used to collect vibration signals during the rock-breaking process. The phase space reconstruction recursive graph (RP) similarity model was used to accurately distinguish the GWO-VMD principal components of the signals. The real signal with interference removed was reconstructed, revealing the distribution characteristics of the energy of the gas explosion signal in the time-frequency domain, and quantifying the accuracy error of the digital electronic detonator. The results show that compared with traditional variational mode algorithms, the GWO-VMD algorithm has significant advantages in improving the signal-to-noise ratio and adaptive feature extraction of gas explosion signals, and has strong time-varying frequency tracking performance. It can accurately identify the detonation accuracy of digital detonators and effectively identify the related of tunnel-blasting detonator disaster sources.

In order to address the floor heave issue during the mining of fully mechanized top-coal caving faces in ultra-thick coal seams, the floor heave mechanism was investigated through field investigations, theoretical analysis, and numerical simulations. Corresponding control technologies were proposed. The ZF1409 working face in a coal mine in Shaanxi province was selected as the engineering case. Key findings include: Severe floor heave predominantly occurs during periodic weighting periods. Higher shield support resistance is observed, particularly in areas with mudstone-dominated floor strata or thin residual coal beneath the floor. The sliding surface of the floor stratum primarily consists of weak mudstone with low ultimate bearing capacity. Floor heave initiates when the applied load exceeds the ultimate bearing capacity. The frictional resistance and cohesion generated by the self-weight of the rock mass along the sliding surface are overcome. Numerical modeling of the ZF1409 face reveals that shield support resistance plays a critical role in floor heave evolution. Under fully mechanized top-coal caving conditions in ultra-thick coal seams, the sudden rupture of the near-field key stratum forms a cantilever beam structure, causing rapid escalation of shield resistance and subsequent floor heave. Implementing underground regional hydraulic fracturing technology to precondition the near-field key stratum effectively mitigates floor heave by optimizing stress redistribution.

In order to constrain the definition and scope of marine nuclear safety and to ultimately support the comprehensive objectives of protecting human health, guaranteeing radiation safety for the marine environment and organisms, and maintaining marine biodiversity and ecological service functions, the evolving concepts from safety, marine safety, and nuclear safety, to marine nuclear safety were comprehensively tracked. Assessing techniques of marine nuclear safety including background baseline method, activity limit method, dose limit method, and radiation risk method were established to evaluate the discharging of artificial radionuclides into the ocean. To protect human health and ecological and environmental safety, priority directions including source identification, bioconcentration, and transfer of radionuclides and their associated nuclear safety assessment in seafood based on "Big Food Concept", assessment of radiation dose on marine biotas and protection, and radionuclides-driven synergistic effects of multiple pollutants were proposed and suggested for the future development of marine nuclear safety. In summary, this study systematically examines the conceptual framework and scope of marine nuclear safety, evaluates the advantages and applicability of four assessment methodologies to address multi-level nuclear safety management needs, and identifies three key research directions to advance the high-quality development of marine nuclear safety assessment technologies in the context of climate change and human activity.

In order to explore the effect of gas injection pressure of power plant on the adsorption gas desorption efficiency of coal seam, NMR technology was used to quantitatively study the dynamic change process of CH₄ competitive adsorption under different gas injection pressure of power plant. The influence law of gas injection pressure on methane desorption, desorption efficiency and unit time recovery efficiency was obtained. The experimental results show that when anthracite coal adsorbs CH₄, the T₂ spectrum shows a bimodal characteristic. As time increases, the peak of T₂ spectrum of adsorbed CH₄ increases, while the peak of T₂ spectrum of free CH₄ decreases. With the increase of time, the adsorption rate of CH₄ by coal slows down. During the competitive adsorption process of power plant flue gas and CH₄ from coal, the T₂ spectrum exhibits three-peaks characteristics. As time progresses, the T₂ spectrum peaks of adsorbed CH₄ decreases, while the T₂ spectrum peaks of free CH₄ increases. The integrals of adsorbed and free T₂ spectra show an exponential function with the adsorption time, and a linear function with the pressure of flue gas injection in the power plant. The power plant flue gas injection pressure shows a linear increase with CH₄ desorption efficiency. The injection of 3.5 MPa power plant flue gas increases the total desorption of adsorbed CH₄ from coal samples in the sample tank by 0.016 mol, enhances the recovery efficiency per unit time by 3.440%, and increases the total desorption efficiency by 20.631%, compared to 1.5 MPa.

In view of the booming of flight flow of urban logistics UAVs and low airspace utilization due to isolation mode of operation, safe and efficient cross-operation needs to be implemented. The crossing separation model was constructed by studying the crossing operation collision risk at the same altitude, and the core parameters such as lateral error, vertical error and longitudinal proximity rate were determined. By introducing the Event model method and constructing separation model, the failure probability of airborne CDR system was further considered. By using event tree analysis method, a comprehensive model of urban logistics UAV crossing separation was proposed and constructed. Results show that the required crossing separation is 158 m for the target safety of level 1.5×10^-8 and 155 m for the target safety of level 1×10^-6 when the route angle is 60 degrees. With the increase of crossing angle, the required separation generally shows an upward trend. When it approaches 180°, that is, opposite direction operation, the required separation increases sharply, which is consistent with the actual cognition.

In order to investigate and predict the internal failure and instability characteristics of gas hydrate coal samples under triaxial action, laboratory triaxial compression tests were first conducted based on the gas hydrate solidification method. Using scanning electron microscope(SEM) images as reference, composite Clump particle templates were constructed to establish biaxial compression models through discrete element method (DEM). The models were featured different particle shapes (irregular and spherical) and saturation levels (40%, 60%, 80%), followed by simulated triaxial compression tests. A comparative analysis was then performed from both macroscopic and mesoscopic perspectives to examine the effects of Clump particles versus spherical particles on the mechanical behavior of gas hydrate-bearing coal. The results demonstrate that the peak strength of specimens increases with hydrate saturation for both particle shapes. The enhancement becomes less pronounced at higher saturation levels. Irregular particle specimens exhibit significantly greater strength than spherical ones, with maximum strength improvement reaching 142.01%. Both saturation and particle shape show limited influence on failure modes. All specimens exhibit bulging failure and X-shaped shear band distribution. Spherical particle specimens display substantially more particle rotations and larger failure zones compared to irregular particles. During loading, irregular particles form stable load-bearing networks through interlocking, supported by their notably higher average coordination number than spherical particles. These findings confirm the superior performance of irregular particle models in characterizing the mechanical behavior of gas hydrate-bearing coal.

In order to explore the effect of high fluid slurry materials on the micromechanical properties of coal, the transition area formed by different slurry materials and coal after grouting was scanned by scanning electron microscopy (SEM). Nanoindentation tests were carried out to analyze the effects of high fluid slurry materials on the microstructural characteristics and micromechanical properties of coal. Structural defects existed in the consolidated surface after grouting of ordinary cement materials. In view of this, the structural modification and mechanical strengthening mechanism of the transition area of the heterogeneous body were analyzed. The results show that the mechanical properties of the transition area between the high flow grouting material and the coal body are the weakest in the heterogeneous structure. This area is easy to break. The indentation modulus and indentation hardness in the transition zone between high flow grouting material and coal increase with the increase of mechanical properties of coal structure surface. After the ordinary cement grouting, the transition zone between the material and the coal body is large. The crystal density is low, there are obvious cracks between the material and the coal body, and the micromechanical properties are weak. After grouting, the high flow grouting material has close microstructure in the transition zone with coal. The transition zone with consolidated surface is small. Meanwhile, the interface transition zone (ITZ) has good micromechanical properties. These characteristics are helpful to improve the ability of gas extraction borehole deformation resistance.

In order to reduce the risk of traffic accidents in expressway agglomerate fog environment, the expressway agglomerate fog zone was divided into transition zone and conflict zone, and driving simulation tests were designed and carried out. Firstly, Analysis of Variance(ANOVA)and non-parametric tests were used to analyze the driving behavior in the two zones. Then, Pearson correlation analysis was used to explore the correlation characteristics of the driving behavior indicators between transition zone and conflict zone. Finally, a binary logistic regression model was used to explore the mechanism of the influence of driving behavior on the collision risk. The study shows that: in transition zone, driving experience and visibility change rate have a significant effect on speed standard deviation and inner boundary speed. Compared with novice drivers, experienced drivers have 36.8% lower speed standard deviation and 13.5% higher inner boundary speed. Visibility change rate has a statistically significant difference on speed standard deviation and inner boundary speed. Different visibility change rates correspond to different inner boundary speed and speed standard deviation. In conflict zone, time to collision (TTC) was significantly positively correlated with visibility, and reaction time was significantly negatively correlated with visibility. TTC, reaction time and collision rate were all significantly negatively correlated with the conflict distance. The speed adjustment behavior in the transition zone significantly affects collision risk in conflict zone.