By clarifying the problems constraining the prevention and control of thermal damage in high-geothermal tunnels—including unclear multi-source heat transfer mechanisms, imperfect quantification of thermal damage classification, and low efficiency of cooling and prevention systems—the foundation was laid for building a collaborative and proactive thermal damage control system.This research systematically analyzed the geological causes, impacts, and prevention and control technology systems related to high-geothermal tunnel hazards.The multi-source heat transfer mechanism composed of magmatic activity, rock properties, structural geology, and deep-circulating groundwater was revealed. The controlling effects of various factors on thermal anomaly formation were clarified, along with unquantified factors in thermal hazard classification, challenges in mitigation methods, and future development trends. It was found that high-geothermal conditions lead to the deterioration of the mechanical properties of surrounding rock, resulting in reduced bolt anchoring strength, cracking of concrete linings, and decreased durability.To address thermal hazards, an advanced horizontal drilling temperature detection and early warning technology was proposed, and a collaborative prevention system integrating ventilation cooling, spray cooling, thermal insulation materials, and high-temperature-resistant materials was established.Limitations of the current system and potential breakthroughs were identified. Key challenges included the lack of clear quantitative thresholds for multi-technology coordination under extreme temperatures, the limited balance between strength and thermal insulation in lightweight aggregate concrete, and the urgent need for composite materials with excellent high-temperature resistance and environmental stability.Finally, three development trends for thermal hazard prevention were proposed, facilitating a shift from passive response to active prevention and control, thereby providing safer and more economical solutions for projects such as the Sichuan-Xizang Railway.

To calculate the load-sharing ratio of surrounding rock in deeply buried pressure pipelines under internal water pressure, a computational model was established based on the power series solution method of complex variable functions. This model considered the interactions among the steel lining, concrete lining, and surrounding rock, as well as the influence of gaps. By solving the potential function for each supporting component, the stress and deformation at any point within their domains, along with the load-sharing ratio of the surrounding rock, could be determined. Subsequently, the effects of internal water pressure magnitude, gap size, and surrounding rock type on the load-sharing ratio were investigated. The calculation results agreed well with numerical simulations. The results indicated that: The pipeline expansion caused by internal water pressure decreased with increasing distance from the pipe; The load-sharing ratio of the surrounding rock was influenced to varying degrees by the internal water pressure, gap size, and surrounding rock type, with gap size being the most sensitive factor—even millimeter-scale gaps significantly reduced the ratio; The load-sharing proportion during combined bearing was determined by the stiffness of each supporting component.

To scientifically reveal the influence of clay content and dry density on the shear strength characteristics of filling medium, triaxial shear tests were performed for filling media with different clay contents and dry densities. The results indicated that the softening degree of the stress-strain curve of the filling medium was found to first decrease and then increase with the increase in clay content; with the increase in clay particles, the role of clay particles was transformed in stages as "filling, lubrication, and force-bearing", and the main force-bearing component was gradually transitioned from sand particles to clay particles. The cohesion of the filling medium was positively correlated with both clay content and dry density; furthermore, the greater the cohesion, the stronger the cementation between particles, and the less likely water inrush disasters were to occur. The internal friction angle of the filling medium was observed to increase with the increase in dry density, while it first decreased and then increased with the increase in clay content. A quantitative characterization model linking cohesion, internal friction angle, clay content, and dry density was established, and the research findings were found to have certain theoretical reference value for the prevention and control of water and mud inrush disasters in tunnel fault fracture zones.

To investigate the dynamic mechanical response of rockbolt grouted structures under confining pressure, the load transfer characteristics and damage mechanisms were analyzed, and the influence of confining pressure on the dynamic bond strength enhancement effect of rockbolts was elucidated. Numerical and experimental studies on the pullout behavior of rockbolt grouted structures under various confining pressures and loading rates were conducted.The results showed that under confining pressure, the maximum pullout load of the rockbolt increased with the loading rate, and the bonding interface exhibited significant loading rate dependence and shear enhancement characteristics.At high loading rates, the local strain at the bond interface was increased during the softening phase, while the dynamic shear stress was found to fluctuate, with the fluctuating concave point shifting closer to the loading end due to the restraining effect of the confining pressure. The fluctuation amplitude was enhanced with increasing confining pressure, attributed to the improved bearing capacity of the grouted body.A positive correlation was identified between the relative bond strength and the logarithmic rate ratio, and the bond performance of the rockbolt was found to be more sensitive to the loading rate under higher confining pressure. After yielding, the slope of the relationship curve was increased by only 11.96% when the confining pressure was raised from 0.5 MPa to 1.0 MPa, indicating that the enhancement effect of confining pressure on the dynamic bond strength of the rockbolt tended toward saturation. The dynamic peak slip of the rockbolt initially increased and subsequently decreased as the confining pressure was elevated. Localized damage to the grouted body was progressively generated, and the failure zone was observed to extend toward the concrete surface.

A three-dimensional numerical model of a multi-story subway station structure was developed,taking the Panyu Square Station on Guangzhou Metro Line 18 as a case study, to simulate the flooding process under extreme conditions. The spatiotemporal evolution of water depth, inter-floor flow rate, and pedestrian walking resistance was analyzed,and the distribution differences under various water ingress conditions were compared. The results showed that the station inundation process could be divided into three distinct stages: channel diffusion, parallel diffusion, and stable ascent. The platform level water level increased in a near-linear manner over time, with its growth rate strongly correlated to the total water ingress rate. In contrast, the station hall water level exhibited a two-stage pattern: initial growth followed by stabilization. The location of water ingress points was found to significantly influence the water level distribution. Higher water levels were observed near the ingress points in the station hall, whereas on the platform level, elevated levels occurred in areas farther from these points. Analysis of inter-floor flow evolution identified a distal surge phenomenon, in which water at the distal end of the platform ingress point rapidly reached the ceiling and flowed back to the station hall. The distribution of the pedestrian walking resistance coefficient indicated that higher resistance occurred both near the water ingress points at the concourse level and near the exits of inter-floor passages at the platform level. The findings of this research provide a scientific reference for monitoring, early warning, and emergency evacuation management during flooding disasters in subway stations under extreme conditions.

To reveal the coupled deterioration mechanism of water erosion and wet-dry cycling in gypsum breccia within underground engineering, gypsum breccia from a tunnel project in Shanxi Province was selected as the research object. The samples were subjected to ten wet-dry cycles, and the apparent deterioration characteristics as well as the water absorption-dissolution evolution behavior of the gypsum breccia under cyclic wet-dry conditions were systematically analyzed. Using nuclear magnetic resonance(NMR)technology, the pore structure deterioration characteristics of gypsum breccia during the wet-dry process were characterized. By comparing the deterioration morphology of samples under static water and flowing water conditions(with a flow rate of 10 L/h), the additional deterioration effect of water flow on the wet-dry deterioration process of gypsum breccia was further investigated. On this basis, a wet-dry deterioration model of gypsum breccia was developed based on the disturbed state concept(DSC)theory, combined with P-wave velocity and porosity test results. The results showed that the interfacial bonding strength between different material zones of the gypsum breccia was weakened by wet-dry cycles, while water flow was found to accelerate gypsum dissolution and deteriorate the shallow pore structure of the samples. The deterioration of gypsum breccia was jointly accelerated by the combined actions of wet-dry cycles and hydraulic erosion. A significant correlation was observed between the attenuation of P-wave velocity and the development of the pore structure in the gypsum breccia. The DSC-based wet-dry deterioration model was shown to accurately describe the mechanical deterioration behavior of gypsum breccia under different hydraulic conditions during cyclic wet-dry processes. The findings provide valuable reference data for the engineering design of tunnels in gypsum breccia strata.

Based on the blasting construction of a large-scale underground water-sealed cavern reservoir project, field vibration monitoring was conducted to analyze the propagation law of blasting vibration in the surrounding rock of the cavern group.The peak particle velocity(PPV)of the surrounding rock was found to occur during the detonation of the perimeter holes or floor holes. The attenuation of PPV in the surrounding rock of the blasting cavern was in good agreement with the Sadovsky formula. A significant difference in vibration was observed between the two side walls of adjacent caverns. An amplification effect was identified for the PPV on the side wall facing the blast, while the PPV on the opposite side wall was only 5% to 10% of that on the blast-facing side. Furthermore, the PPV on the cavern side wall was found to decrease in a wavy pattern with increasing horizontal distance from the blasting source. The research results provide a reference for the monitoring, prevention, and control of blasting vibration in underground caverns.

To provide scientific guidance for optimizing pipe design and predicting blockage risks, this study first established a numerical simulation model for muck transport in discharge pipes based on the CFD-DEM coupling method. The accuracy of the model was validated by comparing the simulated particle settling velocity with experimental data. Subsequently, the effects of pipe flow velocity(v), slurry concentration(s_c), pipe inclination angle(θ), and muck particle radius(r)on transport characteristics were systematically investigated. The results indicated that an increase in v significantly enhanced the average transport velocity of muck. Specifically, when v was raised from 2 m·s^-1 to 5 m·s^-1, the average velocity increased from 0.56 m·s^-1to 3.53 m·s^-1. In contrast, increasing s_c demonstrated limited effectiveness in mitigating blockage risks. Moreover, larger pipe inclination angles(θ)led to a sudden decrease in the average transport speed upon the muck entering the ascending pipe segment, suggesting that steep inclination angles should be avoided in engineering practice. Furthermore, smaller muck exhibited higher transport efficiency, whereas larger ones posed a greater blockage risk.

Traditional methods for measuring segment dislocation in shield tunnels suffer from disadvantages such as high equipment costs and low computational efficiency. To address these issues, an intelligent inspector based on a Client/Server(C/S)architecture was designed and developed. For the hardware, the Raspberry Pi 4B was employed as the main control module, integrated with a binocular camera equipped with a CMOS sensor and an LED display, to enable real-time image acquisition and display. On the software side, a decoupling of the front-end and back-end functions was implemented based on the TCP/IP protocol. The client(front-end), deployed on the intelligent inspector, handled camera invocation, image acquisition, data transmission, and result visualization. The server(back-end), deployed on a consumer-grade computer, was responsible for data listening, invoking the core binocular vision ranging algorithm, and returning the results. The proposed inspector was applied to a section of the Fuzhou Binhai Express Line shield tunnel. The experimental results showed that the calculated values agreed well with the measurements from a weld gauge, achieving a sub-millimeter accuracy in segment dislocation measurement. A single detection took only 5.40 seconds, effectively improving inspection efficiency while ensuring measurement accuracy. This study provides a new approach for the rapid and accurate inspection of segment dislocation in shield tunnels.

To address the issues of image quality degradation and single feature expression in tunnel face images, an intelligent rock mass evaluation method integrating multi-scale progressive enhancement and deep semantic modeling was proposed. A multi-scale image enhancement framework combining spatial domain filtering and transform domain denoising was employed, by which the signal-to-noise ratio was increased by 12.7 dB with significantly enhanced visibility of key geological structures including fractures and joints. A four-dimensional comprehensive evaluation index system was constructed based on the gray-level co-occurrence matrix, improved local binary pattern, and RGB color moments for quantitative rock mass characterization.The ResNet architecture was improved through integration of multi-scale feature extraction and dual attention mechanisms(channel attention + spatial attention), while a weighted cross-entropy-label smoothing composite loss function was adopted to address class imbalance. Based on a constructed database of 5 000 tunnel face images, the model accuracy of 94.27% was achieved on the test set(4.93% higher than the baseline model)with a computational complexity of 4.8 G FLOPs(floating point operations). Practical case verification indicated that the proposed method could provide real-time,objective geological decision support for tunnel construction,significantly improving the intelligence level of rock mass classification.

To comprehensively assess the overall deformation of tunnel cross-sections, a deformation monitoring method based on 3D laser scanning technology was applied in a large-deformation tunnel project. According to the principles of 3D laser deformation monitoring and point cloud processing, the monitoring process was divided into four stages: pre-operation preparation, point cloud data acquisition, point cloud data processing, and deformation analysis. The standard workflow for tunnel deformation monitoring using 3D laser scanning was systematically established. Specific field operation procedures were adaptively modified according to the environmental characteristics of large-deformation tunnels. The monitoring results provided comprehensive representations including deformation nephograms, cross-sectional profiles, and deformation time-history curves. These outputs enabled: rapid evaluation of overall deformation within monitored sections, visual identification of high-deformation zones, assessment of deformation impacts on tunnel clearances, and quantitative analysis of deformation values and convergence trends at specific locations, demonstrating holographic characteristics. The 3D laser deformation monitoring technique shows significant potential for widespread application. However, relevant technical specifications and operational standards should be established in current regulations to improve the technical level of tunnel deformation monitoring.

Aiming at the lack of systematic research on temporary support system design for secondary lining in large-section and deep shafts, this study investigated the feasibility and stability of the full-hall scaffolding method, using Shaft No. 3 of the Xiaping drainage system in Shenzhen as the engineering case. Based on standardized design codes, a scaffolding scheme and key reinforcement measures suitable for deep shafts were developed. A three-dimensional finite-element model of the disk-coupler steel-tube scaffold was established in MIDAS/CIVIL, incorporating typical construction load cases including concrete lateral pressure, structural self-weight, and operational loads. Member stresses, displacements, and linear buckling modes were analyzed. The model accuracy was validated using monitoring data. Results showed that under the maximum construction load, the vertical post exhibits a maximum axial stress of 34.72 MPa, the maximum displacement at the horizontal joint reaches 21.17 mm, and all modal critical load factors exceeded 4, satisfying the safety reserve requirements specified in current codes. The findings demonstrated methodological and practical innovations: the study not only filled the gap in research on the mechanical behavior and stability of full-hall scaffolding in deep-shaft conditions, but also provided technical references and engineering experience for the design and wider application of large-section temporary support systems in underground construction.