Search Results (122)

This research addresses the critical safety issue of harmful gas influx during tunnel excavation through unconventional gas-bearing structures. It focuses on six tunnels affected by shale gas influx along the Zhangnan Expressway of northwestern Hunan, China. The research reveals the geochemical characteristics, distribution patterns, and accumulation mechanisms of harmful gas in the shale formations of northwestern Hunan. The research adopts an integrated approach of “geological background analysis—multi-parameter testing—comprehensive evaluation”. It is based on geological and borehole data, field geological surveys, as well as laboratory and field tests. The research systematically analyzes the gas-bearing structural characteristics, geochemical parameters, and reservoir physical properties of the shale gas area in the Zhangnan Expressway. The geological regularities are summarized. The results show that the Longmaxi Formation of the Silurian system and the Qixia Formation of the Permian system serve as source rocks in the tunnel sites. The reservoirs are characterized by ultra-low porosity and permeability, with limited late-stage hydrocarbon generation potential. The gas-related hazard during tunnel construction and operation is primarily associated with the release of existing free and adsorbed gas. According to the calculation standards for absolute gas emission rates during construction, three tunnels are classified as micro-gas tunnels and three as non-gas tunnels. Two accumulation patterns are proposed: the self-sourcing composite accumulation pattern with micro-scale migration, and the accumulation pattern of self-generated and self-storage type of water pressure confinement. Enhanced monitoring, ventilation, and grouting sealing are recommended. This study develops an integrated “geology—testing—evaluation” assessment method for shale-gas-bearing tunnels. It provides important guidance for controlling harmful gas hazards in such tunnels and guaranteeing the sustainable development of tunnel construction. Full article

Road tunnel fires can produce rapid heat accumulation and severe thermal loading, particularly when fixed firefighting systems are not activated during the early stages of fire development. Although previous tunnel fire studies have examined ventilation effects and individual fire scenarios, only a limited number have quantitatively evaluated the performance of water-mist fixed firefighting systems under substantially different fire intensities using identical tunnel geometry and operating conditions. This gap restricts the ability to assess suppression efficiency across both moderate and severe tunnel fire scenarios. Computational fluid dynamics modelling, particularly the FDS–LES framework, enables controlled comparison of such scenarios that would be difficult, costly, or unsafe to reproduce in full-scale tunnel experiments, while providing detailed information on temperature field development and heat propagation. This study evaluates the influence of a water-mist fixed firefighting system on temperature development and the spatial extent of high-temperature zones in a road tunnel. Numerical simulations were performed in PyroSim using the Fire Dynamics Simulator (FDS) and the Large Eddy Simulation (LES) approach. Four scenarios were analyzed under identical tunnel geometry, ventilation conditions, and operational settings, combining two heat release rates (30 MW and 200 MW) with suppressed and unsuppressed fire conditions. The 30 MW case represented a passenger vehicle or light commercial vehicle fire, whereas the 200 MW case represented a severe heavy goods vehicle fire. The results showed that, in the 200 MW scenario, activation of the fixed firefighting system reduced the maximum temperature from 950 °C to 700 °C (−26%), while in the 30 MW scenario the maximum temperature decreased from 310 °C to 160 °C (−48%). Minimum temperatures were reduced from 550 °C to 200 °C in the 200 MW scenario and from 290 °C to 110 °C in the 30 MW scenario. The water-mist system also limited the propagation of the high-temperature layer beneath the tunnel ceiling, with a more pronounced relative effect under the lower heat release rate. Although complete suppression of the 200 MW fire was not achieved, the system reduced peak temperatures and limited the extent of critical high-temperature zones. The main contribution of this study is the quantitative comparison of water-mist suppression performance under moderate and severe tunnel fire conditions using the same tunnel configuration, which provides practical evidence for assessing peak-temperature reduction, high-temperature zone limitation, and thermal loading mitigation in road tunnel fire safety design. Full article

Road tunnel ventilation systems have traditionally been designed to dilute vehicle-generated pollutants and control smoke during fires. However, the thermal environment, including temperature and humidity, is not the variable taken into consideration. Despite the operation of its ventilation system, Boryeong Subsea Tunnel (6.9 km), the longest subsea road tunnel in Korea, has experienced severe condensation since its opening in December 2021. As hot, humid ambient air enters the tunnel and meets wall surfaces cooled by seawater and the surrounding ground, condensation and fog may form, reducing visibility. To investigate the causes of condensation and develop a decision-making tool for prediction, a variety of tasks were carried out: (1) field measurements of temperature, humidity, tunnel wall temperature, and tunnel air velocity; (2) development of a 1D model for condensation rate quantification; and (3) 3D CFD simulations. Condensation occurred mainly from June to September, with the most severe conditions in July and August. Both the 1D model analysis and the CFD simulations showed good agreement with field measurement data, with wall temperature errors within 7.3%. Under current traffic conditions (with a peak of approximately 250 veh/h), the annual condensation volume was estimated at approximately 12,415 ton/year. Under the design traffic volume (1550 veh/h), heat from vehicles was found to effectively suppress condensation. The Condensation Contour Map (CCM) was developed as a decision support tool to predict the likelihood and amount of condensation based on the tunnel air temperature and humidity conditions. The results of this study clearly indicate that condensation should be explicitly considered in the design and operation of long subsea road tunnels. Full article

High rock temperature (HRT) and its associated thermal hazards, alongside secondary mechanical risks such as swelling pressures induced in clay layers, pose severe threats to the construction safety of deep-buried tunnels. This study aims to quantitatively reveal the evolution laws of the surrounding rock temperature field under varying heat source conditions. A combined approach of physical model testing and numerical analysis was adopted. Utilizing an independently developed test system with a 1:13 geometric similarity ratio, the coupled rock-heat-ventilation environment was simulated. A transient conduction-convection 3D numerical model was established in COMSOL and verified against experimental data under benchmark conditions. The research confirms that under the influence of localized block heat sources, the temperature field in the far-field region follows a significant linear attenuation law rather than the traditional exponential distribution, with a prototype-equivalent gradient of approximately 0.69 °C/m. Furthermore, the study quantitatively identifies 8 m³ as the critical volume for heat source geometric saturation, beyond which the incremental temperature rise efficiency decreases by 25%. It is further revealed that the effective cooling depth of conventional ventilation is only approximately 0.35 m, indicating a significant “ventilation shielding effect” within the deep surrounding rock. Full article

The performance of native landraces of Capsicum annuum L. under contrasting production systems remains poorly understood, limiting their evaluation under locally relevant production scenarios. This study evaluated the phenological and productive responses of five genotypes (four native landraces and one commercial cultivar) under two systems representing locally relevant production conditions: open-field (OF) and a substrate-based hydroponic system under low-technology, passively ventilated tunnel-type greenhouse conditions (GH), to describe genotype-specific responses under contrasting production conditions during the 2023 growing season in Puebla, Mexico. Agroclimatic and agronomic variables were analyzed using independent ANOVA by system and canonical correlation analysis (CCA). The GH system exhibited restrictive microclimatic conditions, with maximum temperatures exceeding 48 °C and photosynthetically active radiation reduced by approximately 53% compared to OF conditions. Environmental conditions were not standardized between systems; therefore, the results reflect the contrasting microclimates of locally relevant production systems and provide a context-specific assessment of genotype performance. Under the specific conditions evaluated, yield was lower in GH compared to OF across all genotypes. The commercial cultivar Serrano Tampico achieved the highest yield (1.118 kg per plant under OF), while Mixteco Largo and Cola de Ratón produced the highest number of fruits. The CCA identified genotype-specific associations between environmental and agronomic variables, suggesting distinct performance patterns under contrasting production conditions, with native landraces exhibiting better agronomic performance under OF conditions. Overall, the results provide a context-specific characterization of genotype performance under contrasting production conditions. Full article

Traditional road tunnel ventilation systems suffer from high energy consumption and limited effectiveness in fire smoke control. Thus, there is a pressing need to develop advanced air purification technologies that integrate low energy demand with efficient smoke mitigation capabilities. In this study, a self-developed negative ion purification system was implemented, and systematic full-scale experimental investigations were conducted in both a test tunnel and an operational road tunnel to evaluate its performance in air purification and smoke suppression under normal operation and fire conditions. Key parameters, including negative ion concentration, particulate matter concentration, carbon monoxide (CO) concentration, and smoke distribution characteristics, were measured to elucidate smoke evolution behavior and the underlying mechanisms influenced by negative ions. The results show that the negative ion purification system can rapidly establish a high-concentration negative ion field within the tunnel space. Under normal operating conditions, negative ions markedly reduce particulate matter concentrations and their fluctuations, thereby effectively improving tunnel air quality. Under fire conditions, the system maintains high purification efficiency, with significant reductions in particulate matter concentration observed in the test tunnel and clear suppression of longitudinal particulate transport in the real tunnel. In particular, PM10 exhibits a higher removal efficiency. In addition, negative ions promote particle agglomeration and gravitational settling, accelerate CO dilution and dispersion, and significantly improve tunnel visibility. The results demonstrate that the negative ion purification system exhibits strong applicability and considerable engineering potential across different spatial scales and fire scenarios. Full article

Large-section tunnels produce a large amount of dust after drill-and-blast construction. If not removed in a timely manner, the dust will seriously endanger workers’ health. For the purpose of enhancing the working conditions within the tunnel during construction, this investigation employs an integrated methodology that combines computational simulations with on-site measurements. Drawing upon the principles of gas–solid two-phase flow theory, the coupled diffusion law of airflow and dust in large-section tunnels is investigated. A two-factor orthogonal experiment combined with economic analysis is employed to determine the optimal ventilation parameters for the forced ventilation system. The findings indicate that, when the initial ventilation configuration is applied, the airflow field is divided into three stages, and dust diffusion is primarily driven by airflow. The average dust concentration in the 1.6 m breathing zone at 600 s post-blasting is measured to be 36.8 mg/m³. While satisfying the ventilation demand stipulated for the tunnel, the optimal ventilation parameters are determined as an outlet air velocity of 18 m/s and a duct-to-face distance of 40 m. Under these conditions, the dust concentration is reduced to 1.5 mg/m³, representing a 95.9% improvement in dust removal efficiency. Additionally, the hourly electricity cost at 18 m/s is USD 4.39 lower than that at 20 m/s. This study provides valuable insights for optimizing forced ventilation parameters in large-section tunnels, significantly reducing pollutant levels while saving costs. Full article

Air curtain systems have been proposed as a supplementary smoke control strategy for vehicle tunnels, particularly where structural constraints limit the installation or upgrading of conventional ventilation systems. However, most previous studies rely on numerical simulations or fixed experimental facilities, while flexible experimental platforms and the influence of vehicle obstruction on smoke behavior remain less explored. This study experimentally investigates the smoke confinement performance of an air curtain using a 1:18 modular detachable scaled vehicle tunnel model. The modular configuration enables flexible assembly and adjustment of the experimental setup for different test conditions. A series of laboratory experiments was conducted using a liquefied petroleum gas (LPG) burner to simulate a vehicle fire. Temperature measurements and smoke visualization were performed under different air curtain jet velocities and vehicle obstruction conditions to analyze the interaction between the air curtain jet and buoyancy-driven smoke flow. The results show that the air curtain significantly restricts the upstream propagation of hot smoke and modifies the thermal field inside the tunnel. When the jet velocity reached approximately 5 m/s, the temperature in the protected region decreased by about 25–35% compared with the case without an air curtain. In addition, the presence of vehicle models altered the airflow structure and increased heat accumulation in the middle region of the tunnel cross-section. These results demonstrate that the proposed modular tunnel model provides a reliable experimental platform for tunnel fire research and highlights the importance of considering vehicle obstruction effects in tunnel smoke control studies. Full article

Platform screen door (PSD) systems can reduce particulate matter (PM) levels at subway platforms, but transient particle migration between tunnels and platforms still occurs during door operation. Existing control measures, such as tunnel cleaning, ventilation optimization, onboard dust removal devices, and air curtain systems, mainly target background PM concentrations and generally function as passive mitigation strategies. However, the transient dynamics of tunnel-to-platform PM migration during PSD operation remain insufficiently understood. In this study, field measurements and numerical simulations were used to investigate PM migration under realistic subway operating conditions. Field observations were conducted to characterize the spatial distribution of PM and its relationship with tunnel piston wind. A numerical model based on the Discrete Phase Model (DPM) was then developed to simulate particle transport under different PSD operating sequences. The effects of PSD opening delay and opening duration on particle migration were examined to evaluate their influence on migration rates. The results show that adjusting the timing of PSD operation can significantly reduce tunnel-to-platform PM migration, whereas conventional air curtain configurations may enhance interzonal particle exchange under certain conditions. These findings improve the understanding of PSD-related PM transport and provide potential operational strategies for improving air quality in underground rail transit systems. Full article

The article discusses the development and design of intelligent mine ventilation systems, which are an important part of the construction and modernization of modern mines, as well as key technical support for the implementation of intelligent mining technologies. A high-fidelity simulation environment is constructed using neural networks based on field data. In the process of mine ventilation control, due to the complexity of the tunnel environment, it is difficult to investigate the implicit relationship between the ventilation system outlet control parameters and the concentration of gas and dust, oxygen, and carbon dioxide in the tunnel. Hence, it is difficult to obtain an overall control strategy based on experience. This article explores the possibility of applying reinforcement learning to intelligent shaft ventilation systems, a dynamic process in which model parameters, such as strategies and value functions, are updated through continuous interaction with the environment. Full article

Fire accidents in road tunnels can cause a significant number of fatalities and severe damage to tunnel structures. The tunnel European directive applies to the trans-European road network and requires the use of active smoke control systems in most tunnels longer than 1000 m. Research has investigated whether shorter tunnels without active smoke control systems are safe. If smoke contaminates the lower layer where people evacuate, it can impair visibility. This disturbs egress and may cause intoxication and, eventually, death. The FireFoam computer code was applied to the Memorial Tunnel fire ventilation tests for validation. This work investigates the effect of varying the heat release rate (HRR), ranging from 6 to 100 MW, under a wind velocity of 0.77 m/s and in the absence of wind. Results show that high HRR moves the start of lower layer smoke contamination closer to the fire source, reducing the distance from 390 m at 14 MW to as close as 210 m at 100 MW. An analytical model was developed to predict the distance from the fire source where smoke can contaminate the lower layer and was subsequently improved to account for HRR variation. Full article

Energy-efficient operation of highway tunnel ventilation systems remains challenging, and optimal power allocation among multiple fans is essential for reducing overall energy consumption. This study begins with a quantitative analysis of multi-fan synergistic effects, decoupling the interactions into sequential transverse and longitudinal superpositions. An equivalent predictive model is then established for rapid and accurate calculation of the overall ventilation supply, where a neural-network surrogate model is integrated to predict the superposition effects. Building on this model, an improved particle swarm optimization (PSO) algorithm is applied to determine the optimal power allocation, demonstrating robust applicability across tunnels of different lengths and fan configurations. Validation against CFD simulations shows that the predictive model yields an error of about 3%. By enhancing both transverse and longitudinal synergies, the optimized power allocation scheme can reduce ventilation energy consumption by 36%. Thus, the proposed framework provides a practical and scalable solution for multi-fan power allocation in highway tunnel ventilation systems. Full article

The extensive mining area and multitude of working sites in Maping Phosphate Mine result in a complex ventilation system. This complexity manifests as uneven airflow distribution at working faces, posing considerable challenges for efficient ventilation management. An intelligent ventilation management system based on the Python PyQt5 library was developed for Maping Phosphate Mine to improve ventilation efficiency, lower dust concentration at the working face, and enhance safety by addressing uneven air volume distribution. The implementation of an integrated system, comprising a 3D ventilation network model, remote control capabilities, and smart algorithms, has successfully realized zonal planning and on-demand ventilation in the mine’s underground workings. To adapt to the fluctuating air demand at the tunneling face, a remote intelligent control scheme for louvered dampers was implemented. This dynamic demand-based strategy achieves precise distribution of air volume throughout the ventilation network. The research results demonstrate that the system effectively addresses the uneven distribution of air volume, thereby improving the overall ventilation environment and reducing the risk of ventilation-related accidents. The system serves dual purposes: it provides an intelligent ventilation control mechanism and integrates seamlessly with the key subsystems for underground safety production. This synergy is instrumental in advancing the mine’s digitalization and intelligent transformation initiatives. Field test results indicate that the system achieved a 30% reduction in energy consumption and a 70% decrease in dust concentration at the working face, respectively. Full article

With the rapid expansion of urban areas, short naturally ventilated traffic tunnels (NVTTs) have become prevalent in modern cities. However, their enclosed design and inadequate ventilation often lead to the accumulation of vehicle emissions, especially during peak traffic periods, which poses significant threats to public health. Previous studies have shown that airflow in such tunnels is caused by ambient crosswinds (ACWs), which contribute to the dilution of pollutants. Based on this, a geometrical model including traffic tunnels belonging to a complex traffic system of the Second Ring Road in Wuhan City was established, followed by a mathematical model describing the fluid flow and pollutant transformation. The current flow characters and pollutant dispersion mechanism of CO and NO_X were analyzed. Among them, the number and speeds of vehicles are measured to calculate the strength of the pollutant source. Then, the data was set as the initial contaminant source strength in Ansys Fluent 14.0 to compute the pollutant dispersion of the whole domain. The results indicate the following: (1) The airflow direction inside the tunnel varies with changes in ambient wind direction and wind speed. Specifically, variations in ambient wind direction result in changes in airflow direction in both tunnels. In contrast, changes in wind speed do not affect the airflow direction in both tunnels; only in the downstream tunnel does the airflow direction change with increasing westward wind speed. By comparison, in the upstream tunnel, the airflow direction remains unchanged regardless of the westward wind speed; (2) Pollutant accumulates along the downstream airflow in both the tunnels; (3) The mass fraction level of contaminate stratification differs along the tunnels. The pollutant tends to form y-component layering near the upwind opening and x-component stratification at the downwind opening of the two tunnels. Full article

Drill-and-blast tunnel construction continuously releases high-intensity dust during drilling, blasting, and shotcreting, while conventional forced ventilation is often insufficient to control dust migration and worker exposure. This study develops three-dimensional Euler–Lagrange gas–solid two-phase models for these three typical processes to clarify the spatiotemporal dispersion of polydisperse dust and to explore effective control strategies. The simulations show that all processes generate a persistent high-concentration dust belt near the tunnel face, and a low-velocity recirculation zone at the crown acts as a structural hotspot of dust accumulation that is difficult to purge by longitudinal ventilation. Particle size strongly affects dispersion behaviour: coarse particles rapidly settle near the source under gravity, whereas fine and medium-sized particles remain suspended for long periods and can be transported over long distances, particularly after blasting. Based on these findings, a rail-mounted purification system with a dynamically adjustable position along the tunnel is proposed, and its preferred deployment zones are determined to work synergistically with the main airflow. The system is designed to perform near-source and crown-targeted removal, providing an engineering-oriented “dynamic local purification plus overall ventilation dilution” pathway for improving air quality in drill-and-blast tunnel construction. Full article