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Underground cavities have complex spatial structures and geological settings, their arrangement is dense and crisscrossed. The construction system involves multiple work surfaces, levels, and processes. The close integration of construction simulation with actual production conditions is crucial for enhancing the guidance that simulation results provide for practical engineering. Therefore, from the perspective of optimizing construction organization and management, this article comprehensively considers various factors in the construction process, innovatively introduces the principle of production line balance and the concept of rule cycle, and combines technology and management, an underground cavities construction simulation system (UCCSS) is developed. In UCCSS, a hierarchical model is built and calculation are performed on models with different construction methods by modifying the parameters as per the actual engineering characteristics. The simulation results are comprehensively analysed to determine the optimal construction programme. An application case is proposed based on the construction organisation design of the long and parallel diversion tunnels at the CB Hydropower Station. The results show that the system has good practicality and credibility and can provide guidance for the construction organisation design of underground cavities with various features. [ABSTRACT FROM AUTHOR]

To improve crowd evacuation efficiency in large building spaces during fires, a spatial layout optimization method using PyroSim and Pathfinder software was proposed. Disaster-causing factors that hinder safe evacuation - such as smoke spread, fire scene temperature, CO concentration, and visibility - were compared. The arrival time of danger in fire environments was analysed, the time required for crowd evacuation was calculated, structural characteristics of building space affecting evacuation efficiency were identified, and evacuation bottlenecks in large-scale buildings were revealed. Taking the super-large building of Silk Clothing City in Jiangsu Province, China as an example, a spatial layout optimization scheme focused on evacuation efficiency was proposed and its effectiveness was verified. Results show that before spatial layout optimization, the available safe evacuation time is 145 seconds, which is shorter than the required safe evacuation time of 197.8 seconds, indicating high safety risks during evacuation in a fire. After optimizing the layout of smoke exhaust equipment, the available safe evacuation time is increased to 205 seconds, substantially enhancing crowd evacuation safety. [ABSTRACT FROM AUTHOR]

Fire is a serious threat to people's lives and property. Be aimed at the low detection accuracy of the current fire detection system, a fire detection system based on one-chip computer is proposed in this work. To achieve fire detection and warning, the system collects these signals such as smoke and temperature from the surrounding environment, and processes them with a one-chip computer. The simulation experiments of the system are conducted with Proteus, and the experimental results indicate that the system can detect accurately. [ABSTRACT FROM AUTHOR]

The displacement of air masses caused by the movement of objects or vehicles is often characterized by considerable energy content, which, with appropriate technologies, can be partially recovered. In this sense, numerous scientific works consider rail transport as a possible context for application. However, the literature in the sector highlights how using existing wind technologies in these areas involves many difficulties, mainly related to the turbulent and impulsive nature of the airflows generated. This work presents the architecture and general aspects of an innovative technology for obtaining electrical energy from variable and impulsive airflows, such as those due to the rapid transit of railway trains in tunnels, without precluding its use in other similar fields. The innovative aspect mainly concerns the independent control of two distinct typologies of bladed elements, which can also have translational movement and drag-based and lift-based aerodynamic behavior to improve the adaptability of the embodiment to the site's fluid dynamic and geometric characteristics. Furthermore, the structural simplification of the apparatus, shifting some of the technological complexity to the control systems, brings further advantages in terms of construction cost, robustness, maintenance, reuse, and transferability to different contexts. Of course, the counterpart of these benefits lies in the software and hardware of the control devices. Analytical models to determine the non-dimensional performance coefficients of the two basic types have been reported as has the architectural model of the control system. The technology shown in this work is protected by an EP and US Patent. [ABSTRACT FROM AUTHOR]

Fires not only cause devastating consequences for human life and property, but also lead to soil erosion in forests. Therefore, it is necessary to design a novel algorithm that can quickly monitor smoke from fires. Most existing smoke segmentation methods do not consider the segmentation accuracy of algorithms under limited computational resources. To address this research gap, this paper proposes a lightweight smoke segmentation algorithm based on DeepLabV3+ that achieves fast inference speed and high accuracy for different sizes smoke. To reduce the number of parameters, the feature extraction network of the DeeplabV3+ algorithm is replaced by MobileNetV2, which enhances the extraction ability of the algorithm in segment smoke images. Then, the Convolutional Block Attention Module (CBAM) is added to the encoder part to enhance the perception of the algorithm for small smoke and effectively alleviates smoke mis‐segmentation. Furthermore, a newly designed loss function is used in the network. The experimental results show that the proposed method has improved by 1.27% in Smoke IoU and 1.21% in mPA compared with other methods. The weight size has been reduced to 10.76% of the original DeepLabV3+, and the inference time is only 33.71ms. Therefore, it is a more suitable early fire detection algorithm for resource‐constrained environments. [ABSTRACT FROM AUTHOR]

With the rapid development of the national economy, China's transportation industry is experiencing accelerated development, and, at the same time, the number of long tunnels is constantly increasing. In order to examine the influence of jet fan spacing on gas transport law during the construction of long highway tunnels, this study used the Baima Highway Tunnel in Sichuan as an engineering prototype and established a numerical tunnel ventilation model based on Fluent numerical simulation software. The gas transport characteristics of jet fans in tunnels at different spacings (200 m, 400 m, 600 m, and 800 m) were studied. The results showed that with the increase in jet fan spacing (200 m, 400 m, 600 m, and 800 m), the gas concentration at the tunnel face showed a trend of decreasing and then increasing. Moreover, by analyzing the gas distribution cloud map and the wind flow line diagram, it was determined that the ventilation system effect was the best when the jet fan spacing was 600 m, which met the requirements of a gas concentration of less than 0.5% at the tunnel face and a minimum wind speed of 0.25 m/s. At the same time, according to the optimal spacing for the optimization of the site ventilation system, it was observed that after the ventilation was stabilized (after 600 s), the minimum value of the gas concentration in the left and right tunnel holes diminished from 0.38% to 0.31% and from 0.41% to 0.31%, with rates of reduction of 18.42% and 24.39%, respectively. This indicated that after optimizing the ventilation system at the tunnel site, the concentration significantly decreased compared with before the optimization. Moreover, when the jet fan spacing was 600 m compared with 200 m and 400 m, the annual energy savings were 1900.8 MW·h and 950.4 MW·h, respectively. The research results clarified the optimal layout parameters of jet fans in the Baima Highway Tunnel, providing a reference for the rational layout of jet fans in long-distance tunnels. In addition, the results of this study provide an important theoretical basis for the gas prevention and safe construction of long highway tunnels. Furthermore, this study contributes to research in energy conservation, emission reduction, and sustainable development of energy in the ventilation process during tunnel construction. [ABSTRACT FROM AUTHOR]

This feasibility study investigates extracting thermal energy from the Bedretto tunnel in the Swiss Alps, which benefits from subsurface heat flux and rock overburden insulation. Using the simulation software COMSOL Multiphysics, we created a numerical model of the tunnel environment to evaluate which medium between rock, air, and water serves as the most effective heat source. Our findings indicate that flowing water is the most effective heat source. Potential applications include distributing the water to nearby villages and storing remaining heat in the subsurface. Estimates indicate that the total extractable thermal energy ranges between 0.8 MWth and 1.5 MWth after reducing the water temperature to 4 °C via a heat pump. The study identifies the most suitable energy sourcing locations based on efficiency and investment costs. Circulating water to individual heat pumps in Bedretto, with the natural elevation difference, enables water transport without a pump. Cost analyses reveal that the investment in piping and heat pumps can be amortized within the equipment's lifespan with appropriate economic models. With the same initial investments, district heating systems are viable in villages with over 30 connections. The payback periods are 10 years for 60 connections, 4.5 years for 90 connections, and immediate for 200 connections. [ABSTRACT FROM AUTHOR]

To investigate the combustion characteristics of multiple fire sources in the tunnel caused by 'jumping' discontinuous fire spread, we utilized scaled model experiments, numerical simulation software, and theoretical research. Our study focused on analyzing the influence of different fire source powers on the temperature characteristics of double fire sources in the tunnel. We examined the temperature characteristics, critical wind speed, and change rule under various wind speeds, fire source spacing, and fire source powers. Additionally, we explored the temperature characteristics, critical wind speed, and change rule of different fire source powers under varying wind speed conditions. The mathematical model for roof temperature decay and the temperature decay coefficients of dual source fires were established through the analysis of scale-down model experiments and numerical simulations. In comparison to single-source fires, the temperature variations in the tunnel of dual source fires exhibit a more intricate pattern, with higher average temperature and temperature peak values. These values are influenced by factors such as fire source spacing and power. Numerical simulation software was utilized to investigate the impact of fire source spacing at 10 m, 15 m, and 20 m, as well as the effect of varying fire source power on the temperature distribution within a tunnel under consistent fire source position and growth coefficient. The study revealed that, with consistent double fire source position and ventilation conditions in the tunnel, the upstream fire source exhibited greater power than the downstream fire source, resulting in the lowest average and peak temperatures in the tunnel. This observation could potentially enhance escape and rescue operations within the tunnel. Similarly, the lowest average and peak temperatures in the tunnel were also identified, offering potential benefits for optimizing escape and rescue strategies in tunnel scenarios. [ABSTRACT FROM AUTHOR]

In longitudinal ventilation tunnel fires, the thermal characteristics become more intricate due to the presence of blockages. This phenomenon becomes more complex when multiple blockages occur, which results in a unique interaction between the fire and longitudinal ventilation through gaps between the blockages. Most of the previous studies have only considered single obstacles or have only performed qualitative analyses and have not obtained predictive models. To fill this research gap, we conducted numerical simulations using the Fire Dynamic Simulator (FDS) to study the effects of vehicular blockages in three lanes and two fire locations. Our study highlights the differences in the flame behavior, maximum temperature rise, and smoke back-layering length in the presence of multiple blockages and reveals that as the ventilation velocity increases, the flame bifurcation angle increases and the smoke back-layering length decreases. Additionally, when the fire is in the side lane, the flame tilts towards the sidewall, leading to higher maximum temperatures compared to those in the middle lane. Based on these findings, we have developed modified formulas that predict the maximum temperature rise, smoke back-layering length, and maximum temperature ratio at different fire locations and blockage rates, which are linearly related. [ABSTRACT FROM AUTHOR]

Underground mine fires are dangerous, consume resources, and emit pollutants. Therefore, acquiring in-mine data for fire research is hazardous and expensive due to unsteady temperature changes and toxic gas emissions. Computational fluid dynamics (CFD) models are often developed to mimic airflows and combustion-associated heat transfer. However, research on the performance evaluation of the CFD turbulence models to mimic fire events is limited. This paper summarises the modelling results for a diesel pool fire event in an experimental underground mine that uses an exhaust ventilation system. A fire dynamics simulator (FDS) model was developed to show the spatio-temporal temperature evolution. Reynolds-Averaged Navier-Stokes and large eddy simulation (LES) models were developed using ANSYS Fluent to model species transportation in the transient-state combustion event. LES models showed the closest agreement with the experiments but required the most computing resources. Similar exercises will assist the mine operators in emergency preparedness and in training their safety teams. [ABSTRACT FROM AUTHOR]

This paper evaluates the influence of natural ventilation on the longitudinal temperature attenuation of cable tunnel wall fires. It took into account the effects of different fuel quantities, cable types, cable layers, and the number of cables per layer. Experimental tests were carried out in a cable tunnel. Results indicated that under natural ventilation the cable burns well. The cable total mass loss rate varies under different conditions. Moreover, under natural ventilation, cable combustion was affected by many factors. This paper analyzed the effect of natural ventilation on longitudinal dimensionless temperature attenuation. A mathematical model was proposed for longitudinal dimensionless temperature attenuation under natural ventilation cases. In addition, a predictive model for maximum temperature rise below the ceiling was proposed to address the effects of heat release rate (HRR) and ventilation on cable tunnel fires. The experimental results were compared with previous research results. Finally, this paper established a calculation equation for dimensionless fire source heat release rate. This paper provides guidance for the fire prevention of cable tunnels. [ABSTRACT FROM AUTHOR]

Underground transportation systems often involve multiple tunnels constructed closely together. Previous studies mainly focus on interaction between circular tunnels; by contrast, interaction mechanisms involving non-circular tunnels are not well understood. In this study, four physical three-dimensional centrifuge tests were performed in dry sand, simulating the response of existing circular and horseshoe-shaped tunnels to a newly excavated tunnel. Two different ratios between pillar depth and tunnel diameter (P/D) of 0.5 and 2.0 were considered. Furthermore, three-dimensional numerical back-analyses considering small-strain stiffness were undertaken. Results reveal that the ground settlement above an existing horseshoe-shaped tunnel is less sensitive to pillar depth than for circular ones. Furthermore, for P/D = 0.5, the existing horseshoe-shaped tunnel experiences both vertical and horizontal compression; more stress reduction occurs vertically than horizontally. A circular tunnel for the same pillar depth becomes compressed vertically but elongated horizontally; stress reduction around the existing circular tunnel is less vertically than horizontally. However, for P/D = 2.0, both types of tunnel become elongated vertically and compressed horizontally because of a larger reduction in vertical stresses than horizontal ones. These results demonstrate that both pillar depth and shape profoundly affect tunnel deformation mechanisms. [ABSTRACT FROM AUTHOR]

Nowadays, both process data management and numerical analysis are necessary for decision‐making in a tunnel project from its early design stage to the construction phase. Traditional generation of simulation models largely depends on tunnel design and reports, which are error prone due to the involvement of manual intervention. This article presents the application of a digital workflow to efficiently transfer automatically acquired data from tunnel projects to computational simulations. The application workflow is developed and executed through a web‐based environment. Project data from the Victory Boogie Woogie tunnel is retrieved from the process controlling software PROCON via web services to generate numerical simulations for settlement predictions at different tunnel sections. The simulated results are validated using real measured settlements in the project to prove the quality of the simulation model. Different scenarios of applying operational steering parameters are then investigated, utilising the simulation model, which can be used to support the on‐site engineers as an assistance system to drive the tunnel boring machines. The work has been carried out within the framework of the transfer project T2 of the Collaborative Research Center "Interaction Modeling in Mechanized Tunneling" (SFB 837), which aims to implement and test a digital twin for process control under practical conditions in the tunnelling industry. [ABSTRACT FROM AUTHOR]

The deposition and dynamics of smoke layers in large-space building fires are governed by a complex interplay of factors, making the prediction of such dynamics using traditional mathematical models challenging. In response, this study introduces a Back Propagation (BP) neural network model, devised from field simulation data, to efficiently forecast the temporal progression of smoke layers. It was observed that the model exhibits minimal training errors and high processing speeds, thereby fulfilling the stringent accuracy demands of fire engineering. Specifically, the model achieved a minimum relative error of 0.0005 and a maximum of 0.0845 across various prediction points, underscoring its reliability and precision. The ability of this BP neural network model to predict smoke layer changes significantly enhances the design optimization of smoke control systems swiftly and accurately in large buildings and supports rapid, informed decision-making during fire emergencies. Moreover, the model facilitates the development of engineering calculation models tailored for the quick prediction of fire smoke dynamics, which are essential for both theoretical research and practical applications. This approach not only conserves experimental resources but also advances the implementation of scientific, effective rescue operations in the event of large space building fires. [ABSTRACT FROM AUTHOR]

To understand the stratification of the smoke layer in a road tunnel, numerical simulations are employed to model tunnel fires with varying heat release rates. The different simulations cases are carried out with FDS (Fire dynamic simulations). These simulations are conducted to examine the influence of tunnel slope and longitudinal airflow on the smoke stratification along the downstream side of tunnel. The aim is to explore the relationship between longitudinal airflow and temperature ratio taking into account the tunnel slope. As a result, a quantitative analysis, based on Newman's theory, is conducted to assess the clarity of the smoke layer stratification, a Froude number (Fr = 0.63) is obtained. The slopes in tunnels can have a substantial impact on smoke flow during a fire, primarily driven by thermal buoyancy and the stack effect. With a slope less than 1.5°, the stratification improves. Similarly, clear stratification occurs when the longitudinal airflow is less than 1 m/s. However, a balance between inertia force and buoyancy force is crucial for maintaining clear stratification. Increasing both the longitudinal airflow and the tunnel slope serves to disturb the stratification of the smoke layer. [ABSTRACT FROM AUTHOR]

Previous studies have mainly focused on the situation that the tunnel's continuous flame region was lower than the ceiling height. For tunnels with longitudinal ventilation, the temperature characteristics of strong fire plumes are still unclear. In this paper, the maximum temperature rise beneath the ceiling for strong fire plume conditions in a small‐scale tunnel is studied using fire dynamics simulator. Results show that when the effective height (the distance from the burner surface to the ceiling of the tunnel) is 0.65 m, the maximum temperature rise beneath the ceiling in this work shows a good correlation with Li's model and Kurioka's model. However, as the effective height decreases to 0.55 and 0.50 m, the maximum temperature rise would be significantly lower than the previous model. Therefore, a dimensionless coefficient is introduced to modify the maximum temperature rise model for a strong fire plume, which involves the effective height coefficient, heat release rate, and longitudinal ventilation. A calculation model for the maximum temperature rise beneath the tunnel ceiling in the condition of strong fire plumes is established. The temperature attenuation data along the tunnel are given by statistics. The relationship between the dimensionless temperature rise and the dimensionless position parameter is established, and a unified model under various heat release rates is obtained. [ABSTRACT FROM AUTHOR]

To investigate the improvement induced by horizontal smoke baffles during lateral smoke exhaust, an immersed road tunnel with various horizontal smoke baffles positioned below the lateral exhaust vent was studied numerically. Together with the velocity field characteristics, the temperature distribution was investigated near the lateral smoke exhaust vent, followed by the analysis of lateral smoke exhaust efficiency under different horizontal smoke baffles. Results showed that after installing the horizontal smoke baffle, there was a significant decrease in the extracted cold air, while the high‐temperature smoke in the exhaust vent increases, indicating the plug‐holing is effectively suppressed. It is known that the efficiency of smoke exhaust increases when the length exceedance ratio of the horizontal smoke baffle is smaller than 100%, while it changes slightly when the baffle length continues to increase. When the width ratio of horizontal baffle is smaller than 40%, the efficiency of smoke exhaust increases with the baffle width and then changes slightly with a wider smoke baffle. With a larger aspect ratio, the wider and shorter lateral exhaust vent is beneficial for improving the lateral smoke exhaust. Under the current conditions, the case shows the optimal smoke exhaust performance with a horizontal baffle length exceedance ratio of 100%, a baffle width ratio of 40%, and exhaust vent aspect ratio of 3:1. Finally, an empirical model is developed to describe the improvement of smoke exhaust efficiency caused by horizontal smoke baffle. These outcomes are helpful to the design of lateral smoke extraction system in road tunnels. [ABSTRACT FROM AUTHOR]

In complex underground conditions, the excavation of deep foundation pits has a significant impact on the deformation of retaining structures and nearby subway stations. To investigate the influence of deep excavation on the deformation of adjacent structures, a three-dimensional numerical model of the foundation pit, existing subway station, and tunnel structure was established using FLAC 3D software, based on the Shenzhen Bay Super Headquarters C Tower foundation pit project. The study analyzed the deformation characteristics of retaining structures, adjacent subway stations, and tunnels during different stages of deep excavation, and the accuracy of the numerical simulation results was validated through field monitoring data. The results indicate that during the excavation process of the foundation pit, the lateral horizontal displacement of the retaining structure is generally small, with a typical "concave inward" lateral deformation curve; the horizontal displacement value of the contiguous wall section is less than that of the interlocking pile section. The bending moments of the retaining structure show a distribution pattern with larger values in the middle and smaller values at the top and bottom of the pit, with a relatively uniform distribution of internal support forces. The maximum displacement of the nearby subway station is 8.75 mm, and the maximum displacement of the subway tunnel is 2.29 mm. The research findings can provide references for evaluating the impact of newly built foundation pits near subway stations and contribute to the rational design and safe construction of new projects. [ABSTRACT FROM AUTHOR]

Effective fire prevention in mine workings and tunnels requires a thorough theoretical analysis of the heat and mass transfer processes within these structures. This involves using established models to calculate non-isothermal air flow dynamics in long tunnels and mine workings. While the ventilation of tunnels has been extensively studied, significant challenges persist regarding mine ventilation systems, particularly due to their complex and branched topology. This study aimed to address these challenges and gaps in mine ventilation. We designed a laboratory bench to simulate an inclined mine working with a heat source (fire) and validated a mathematical model of heat and mass transfer in such settings. Using experimental measurements, we verified the model's accuracy. It is important to note that our experimental and theoretical analyses focused solely on the thermal effects of a fire, without considering the release of harmful impurities. Using the validated model, we conducted multiparameter simulations to identify the conditions leading to the formation of a thermal slug in an inclined mine working and the subsequent reversal of air flow. The simulation data enabled us to determine the dependency of the critical heat release rate on the aerodynamic parameters of the mine working. Additionally, we evaluated the changes in average air density within a mine working at the critical heat release rate. These findings are crucial for the further development of a network-based method to analyze air flow stability in mine ventilation networks during fires. [ABSTRACT FROM AUTHOR]

Simple Summary: Positive and negative pressure ventilation systems are widely used in poultry farming to control the internal environment of poultry houses, especially in tropical regions, in which hot and humid climates can pose challenges to the thermal regulation of animals. Knowing that thermal stress impacts the quality of animal meat, this study aimed to evaluate the thermal performance and quality of poultry meat in these two types of shed. The main results found here were that the negative pressure system presents lower temperatures and air enthalpy, and the animals reared in this system have better quality meat. We recommend the negative ventilation system for broiler producers in tropical regions due to its ability to provide better thermal indicators and chicken meat quality. This study aimed to evaluate the thermal performance and meat quality in broilers reared in positive pressure tunnel ventilation (PP) and negative pressure tunnel ventilation (NP) in production houses. 320 Cobb broilers (40 broilers per house) were used. Pectoralis major muscles from 40 broilers (10 broilers per house) were randomly selected and analysed for L* (lightness), a* (redness), b* (yellowness), pH, drip loss (DL), cooking loss (CL) and shear force (SF). Air temperature and humidity of the transportation and slaughterhouse waiting room were recorded in the last week of rearing. Subsequently, the enthalpy comfort index (ECI) was calculated. Air temperature and ECI were higher (p < 0.05) in positive pressure sheds, whereas relative humidity was higher (p < 0.001) in negative pressure sheds. There was no statistically significant difference between the enthalpy comfort index during transport and lairage (p > 0.005). Meat quality defects (high L*, DL, CL, SF) were found in PP and NP. It was observed that b* was higher in PP, although pH and CL were higher in NP. Differences in pH, b* and CL indicate that broilers from PP had a higher level of heat stress. In conclusion, differences in pH, b*value and cooking loss in breast broilers indicate that birds in PP had a higher level of heat stress. Additional studies investigating pre-slaughter handling methods to minimise injuries and heat stress are recommended in order to improve animal welfare and meat quality. [ABSTRACT FROM AUTHOR]

Excavations of foundation pits around tunnels can induce alterations in stress and deformation within the tunnel, thereby influencing the safety of pre-existing tunnels, especially those with curved tunnel segments. This study focuses on investigating the effects of excavation processes and diverse construction methods on underlying curved tunnels, including excavation sequencing, reinforcement techniques, and support strategies. The efficacy of different construction methods in controlling deformation was assessed by a numerical analysis using finite difference software. The results show that adopting a skip excavation approach, positioned at a distance three times that of the excavation width, effectively diminishes heaving at the foundation pit bottom. In situations where tunnels intersect foundation pits at small angles, the generation of the hoop effect through intermittent reinforcement minimizes lateral extrusion forces, thereby enhancing control over both vertical and horizontal deformation of the curved tunnel. Deformation control within the tunnel, ranked from the least to the most effective, includes configurations of discontinuous reinforcement without a bottom plate, discontinuous main reinforcement, no reinforcement, damaged lining with discontinuous reinforcement, discontinuous reinforcement, and portal reinforcement. Moreover, the incorporation of a bottom plate in conjunction with discontinuous reinforcement methods proves efficient in restraining tunnel heave within safety limits. This study provides insights into safeguarding curved tunnels during irregular foundation pit excavation, offering potential time and cost savings through improved protective measures. [ABSTRACT FROM AUTHOR]

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The contour shaping effect of hard granite tunnels is relatively unsatisfactory, and the research on the influence of various blasting parameters on this effect lacks sufficient depth. This paper aims to analyze the blasting law of density coefficient based on stress–strain and damage changes, dynamically examine the blasting process from macro–micro perspectives, and achieve a comprehensive assessment of blasting safety by focusing on vibration speed control. Finally, drawing upon an actual project, an optimized scheme for tunnel blasting involving density coefficient adjustment and plugging length optimization is proposed. The reliability of simulations is verified through field tests while ensuring effective guidance for the actual project. The results indicate that a density coefficient of 1.0 yields the highest peak in effective stress, resulting in superior connectivity within the peripheral hole crushing area under stress wave superposition. Consequently, tunnel excavation achieves better molding effects, effectively controlling the occurrence of over-under cutting at the tunnel shoulder and promoting more uniform diameter distribution of crushed stones after blasting. Moreover, employing a blocking length of 30 cm facilitates enhanced development of internal rock fissures while effectively controlling particle dispersion mode and distance. This approach improves large-scale undercutting within the middle and bottom sections of the hand face rock mass, enhances explosive utilization rate, reduces diffusion of harmful gases, minimizes peak vibration velocity around the excavation surface, and mitigates disturbance caused by blasting on initial support. [ABSTRACT FROM AUTHOR]

Engineering construction (such as water conservancy project, road engineering, and so on) in mountain areas bring mass of waste soil and rock fragment, whose stability is critical to the ecological environment and the safe operation of engineering facilities. The biggest waste dump of the Pumped Storage Power Station Project in Hunyuan County, Shanxi Province, China, with a volume of 7 million m³ and a maximum height of 240 m, is to be located at the origin of Mahua Valley. To assess the potential risk of the waste dump, reconnaissance, geomorphological analysis was undertaken to provide basic data. The potential failure area and volume was determined utilizing Flac3D depending on strength reduction method. The kinematic process and the potential hazards after failure was presented by Particle flow code. The results showed that the factor of safety of the waste dump under heavy precipitation was 1.15, less than the stability requirement of slope in hydropower station, and the potential failure volume was about 4.8 million m³. The scenario-based debris mass run-out paths indicated that, considering the worst cases scenario, the ground ventilation platform and ventilation tunnel exit on the right bank of the gully might be destroyed rapidly by landslide debris. Besides, the debris flow would accumulate at the gully mouth, and even run into the lower reservoir. Thus, more attention should be taken to increase the stability of the waste dump. These results are useful information for decision support and future hazard assessment of such engineering project. [ABSTRACT FROM AUTHOR]

Tunnels with natural ventilation and extraction have become the focus of ventilation research in recent years. It is significant to study the characteristics of smoke in tunnel fires to ensure the safety of people and the tunnel structure. Previous research has mainly focused on natural ventilation in horizontal tunnels, and there are few studies on sloped tunnels. In this paper, we studied the smoke characteristics of natural ventilation extraction in slope tunnel fires both experimentally and theoretically. The small-scale experimental results showed that the position of the fire source, heat release rate (HRR), and the size of the shaft had little effect on the deflection angle of the fire plume. The deflection angle of fire plume was only related to the tunnel slope and increased with the tunnel slope. The slope had no effect on the smoke temperature distribution on the downside of the tunnel, while the smoke temperature on the upside decreased with the increase in the slope. The calculation models of the maximum smoke temperature rise and the smoke temperature distribution were obtained based on the experimental results and theoretical analysis. Compared with the experimental data, the developed semi-empirical models could provide a reliable prediction of smoke temperature. [ABSTRACT FROM AUTHOR]

The challenge of managing sustainable water supply is growing more complex as a result of global climate change. The utilization of dams and reservoirs is essential for effective water resource management. These systems are of utmost importance in the storage and utilization of water throughout the entire year. In water resource planning for these systems, a significant emphasis is placed on predicting inflow to dams. In recent years, there has been notable advancement in artificial intelligence approaches, which have the potential to decrease prediction uncertainties. This study conducts a comparison between implementing machine learning models, specifically the group method of data handling (GMDH), random forest (RF), and adaptive neuro-fuzzy inference system (ANFIS), and the probabilistic Bayesian network method as well as long short-term memory networks (LSTM). This study presents a novel comparison between two black box approaches, analyzing probabilities across three different time scales: monthly, seasonal, and annual. Three temporal approaches were employed to estimate the inflow rate to Zayanderud dam, considering 10 scenarios and identifying influential variables. The results obtained from the simulation showed that the GMDH method, a complex neural network technique, exhibited superior performance in all three temporal scales: monthly, seasonal, and annual. The obtained results were evaluated through the utilization of four statistical indicators. The NS coefficient for the annual approach is 0.98, for the seasonal approach is 0.93, and for the monthly approach is 0.95. Additionally, the mean squared error (MSE) was 0.07, 0.09, and 0.11 for the annual, seasonal, and monthly approaches, respectively. The results showed that the transfer inflow from the Koohrang tunnels and Cheshmeh Langan tunnel greatly influenced the predictions in all three approaches. Furthermore, the precipitation parameter (R) displayed sensitivity solely in the annual and monthly assessments, while no correlation was evident in the seasonal approach. [ABSTRACT FROM AUTHOR]

The article discusses the features of arrangement of smoke protection systems in double-track subway tunnels. The calculation method for the smoke ventilation system parameters is presented, taking into account the factor of longitudinal slope, the heat release power of the fire source, as well as the tunnel characteristics. There are proposed the various schemes of supply and exhaust smoke ventilation systems in double-track tunnels of the Moscow Metro.

AbstractDespite the recognized fact that power transformers (PT) are highly efficient technology, part of their electrical energy is counted as heat losses. Therefore, the cooling system is a critical factor in the life span and performance of the PTs, and hence the adopted thermal energy design can be strongly effective. This study revolves around the innovative development of a novel generation of fixed ventilation fans for PTs, achieved through Computational Fluid Dynamics (CFD) simulations and practical experiments. The proposed CFD model was developed adopting ANSYS FLUENT 19.2. The proposed CFD model was verified by comparing the numerical and experimental results of the cooling air temperature and velocity. A standard k-ε model was used to simulate the airflow of the investigated cooling system numerically. A thermal analysis of a four-sided power transformer was performed, and an analysis of the optimum position to install the cooling fan on the radiator was presented. The most effective number of used fans was also determined. The main results showed that two fans were found to be the best performance among the tested candidate alternatives. The two cooling fans’ size, material, and cover shape were also studied and added to the proposed model. Besides, the utilization of a thermoelectric generator was considered in this study in order to recycle some of the lost heat into output power. An experimental prototype mimicking the actual cooling system for the power transformer was designed and fabricated. Results showed that the selected material has achieved a high Calculated Factor of Safety (FoS) equal to 237, indicating that the utilization of the designed parts is of high safety. [ABSTRACT FROM AUTHOR]

Historic timber structures face substantial fire loads and complex fire risks. Subsequent renovations and utilization may influence their fire safety performance. Therefore, accurately predicting indoor fire development in historic buildings and assessing their fire safety performance is crucial. Numerical fire simulation is currently at the forefront of analyzing and assessing fire risks in historic buildings. However, there is a shortage of globally accessible historic building fire data. This paper proposes a method to determine fire scenarios, peak heat release rates, and development curves of indoor fires in wooden historic buildings through a fire load investigation. Using the Guangzhou ancestral hall as an example, PyroSim fire dynamics simulation software is employed to calculate fire development and assess the available safe evacuation time. The simulation results are subsequently input into the Pathfinder evacuation simulation software to ascertain the required safe evacuation time for indoor occupants. A comparative assessment is conducted to evaluate the fire safety performance before and after the renovation of historic buildings. The research findings indicate that installing closed glass curtain walls in the courtyards of ancestral hall buildings in Guangzhou accelerates the infiltration of smoke during fires, leading to rapid fire spread and long-distance ignition, significantly reducing the time available for safe evacuation. Therefore, when renovating and utilizing the ancestral hall buildings in Guangzhou, the installation of ventilation and smoke extraction systems should be prioritized to slow down fire development. Additionally, controlling the number of indoor occupants is an effective management measure to mitigate fire damage in historic buildings. [ABSTRACT FROM AUTHOR]

Tunnels for subways and railways are a vital part of urban transportation systems, where shield tunneling using assembled segmental linings is the predominant construction approach. With increasing operation time and varying geological conditions, shield tunnels usually develop defects that compromise both structural integrity and operational safety. One common issue is the separation of segment joints that may cause water/mud penetration and corrosion. Existing inspection strategies can only detect openings after their occurrence, which cannot provide early warnings for predictive maintenance. To address this issue, this work proposes a multi-point seam contact pressure monitoring method for joint opening identification. It first derived the theoretical correlation between contact pressure distribution and segment opening; then, a finite element model was established to explore the stress and deformation responses under combined axial and bending loads. Finally, multi-point piezoelectric film sensors were implemented on a scaled segment model to validate the theoretical and numerical analyses. Results indicate that the multi-point monitoring method can effectively identify opening amounts at the segment joints with an average error of 8.8%, confirming the method's feasibility. These findings support the use of this monitoring technique for early detection and assessment of joint openings in shield tunnels. [ABSTRACT FROM AUTHOR]

Ventilation problems are critical in tunnel engineering, and the loss of air volume in ventilation ducts is generally estimated using empirical methods. The air volume calculation makes it difficult to meet the accuracy requirements, resulting in resource waste or insufficient air supply. In this study, the forced ventilation system of the tunnel under construction was investigated based on the computational fluid dynamics method. The mechanism of air leakage on airflow distribution and pollutant transport in the tunnel is determined. Air leakage reduces the distribution peak of pollutants and effectively accelerates the emission of harmful gases. However, this effect decreases with distance from the air duct inlet. Through the calculation results of nearly one hundred models, it is found that the air leakage of the duct can be fitted by logarithmic function and verified by empirical equation. The matching degree between the fitting function of the model and the empirical equation depends on the length of the tunnel. On this basis, the calculation formula of effective air volume near the working face is derived. This study can be applied to the ventilation engineering of the tunnel under construction and provide a theoretical basis for the calculation of the effective air supply. [ABSTRACT FROM AUTHOR]

In the construction and operation stage of urban shield tunnels, joint leakage of shield is always an urgent problem to be solved. In order to further explore the waterproof performance of elastic rubber gaskets at segment joints, the finite element software ABAQUS (2022) was used to establish a fluid-solid coupling calculation model. The dynamic simulation of the leakage process at the segment joints under water pressure revealed the whole process of leakage at the segment joints and the instant water pressure value when the waterproof system failed. The results show that during the whole process from segment assembly to joint leakage, the elastic rubber gasket has experienced four key stages: gasket compression, confined water pushing, water wedge and final leakage. When the opening amount of the gasket is 6 mm and 10 mm, the contact stress between the gasket shows a "W" symmetrical distribution of high at both ends and low in the middle, and the peak of the contact stress at both ends of the interface is about twice as much as that in the middle. The waterproof threshold of the gasket is closely related to the opening amount of the gasket, and the waterproof threshold has the same trend with the initial contact stress between the gaskets. [ABSTRACT FROM AUTHOR]

Given the influence of air intake from inclined shafts in existing tunnel ventilation systems on train comfort and aerodynamic safety, a numerical analysis method is used to study the comfort and aerodynamic safety of operating trains under three conditions—inclined shaft closed and inclined shaft open without and with air intake—and to explore the variation law of transient pressure and aerodynamic force (lift coefficient, transverse force coefficient, and overturning moment coefficient). Combined with practical engineering and requirements, the influence of inclined shaft air intake on train operation comfort and aerodynamic safety is analyzed. Through this research, the influence of using air intake from the inclined shaft of an existing tunnel, a ventilation scheme of the new Wushaoling Tunnel, on the comfort and aerodynamic force of trains is revealed, and the comfort and aerodynamic safety of trains in an actual project are evaluated, verifying the rationality of the ventilation scheme of the Wushaoling Tunnel. [ABSTRACT FROM AUTHOR]

To investigate resistance change in the fire area of a roadway caused by roadway fires, a mathematical calculation model for thermal resistance is developed. Theoretical research is conducted to analyze the factors influencing resistance change through theoretical derivation, revealing that temperature is a key factor contributing to the change in thermal resistance. By leveraging the correlation between changes in CO concentration and temperature on the downwind side of the roadway within the fire zone, researchers developed mathematical models to predict temperature increases at various points downwind of the fire source. These models were then used to determine the mathematical relationship governing the change in thermal resistance. The accuracy of the numerical simulation software was validated using Fluent numerical simulation software and scaled-down model experiments. Full-scale numerical simulation experiments were conducted to investigate the fire characteristics of roadway fires and validate the thermal resistance mathematical model. The results indicate that the thermal resistance in the numerical simulation is 7.55 Pa at 20m from the fire source and 5.54 Pa at the end of the roadway. The decrease in resistance is linear. The minimum error between the thermal resistance calculated by the mathematical model and the gradient of the pressure drop in the numerical simulation is 0.03 Pa, approximately 2.3%. Furthermore, the fitting degree of the pressure drop in each section is as high as 97.7%. The calculation model demonstrates high accuracy and offers a theoretical foundation for investigating fire resistance in tunnel fire. [ABSTRACT FROM AUTHOR]

Urban utility tunnels have developed rapidly in recent years. The effective ventilation system maintains the air quality of the utility tunnel. In order to improve the ventilation performance of utility tunnel, a three-dimensional model of utility tunnel was established according to the design drawings. Based on Fluent 14.0 software, a flow model was established. And numerical simulation methods were used to study the optimization of air ducts and ventilation methods. The utility tunnel used top ventilation and interlayer ventilation. The ventilation methods of different ventilation areas of urban utility tunnels are compared. The results showed that the combination of operational gain and ventilation zone length mainly affected the ventilation effect. Based on the simulation results, a comprehensive ventilation mode consisting of top ventilation, natural ventilation at 400 m long entrance and mechanical outlet exhaust was proposed. Electric valve, fire door, exhaust fan and induction fan could be opened in the urban public utility tunnel at low speed. This new combination method is considered the optimal combination method for the maximum ventilation speed of urban utility tunnels. [ABSTRACT FROM AUTHOR]

This investigation, utilizing the Fire Dynamics Simulator (FDS), explored the impact of dual fire source scenarios within tunnels, particularly focusing on temperature distribution and natural smoke exhaust in tunnels equipped with shaft ventilation. The study compared these scenarios against those involving a single fire source by varying the spacing between fire sources and adjusting longitudinal wind speeds. It was found that the speed of smoke propagation accelerated as the distance between fire sources increased, under a constant power of the individual fire sources. The temperature profiles of the tunnel ceiling under various scenarios exhibited considerable consistency. At lower longitudinal wind speeds, the temperature upstream of the fire source was higher compared to the downstream area, with the minimum temperature recorded at the shaft entrance. Notably, the critical wind speed, defined for a single fire source scenario with power equivalent to the combined power of two closely spaced fire sources, decreased with increasing distance between the fire sources, revealing a finite limit. In the shaft, a pattern was observed where the smoke temperature, gas mass flow, and carbon monoxide concentration initially increased and then decreased with a rise in longitudinal wind speed, reaching optimal efficiency in smoke exhaust at a wind speed of 2m/s. The complexities inherent in dual fire source scenarios were more pronounced compared to single fire source scenarios, presenting increased risks to safety and health during a fire. This study underscores the need for strategic planning in tunnel design, particularly in accommodating ventilation systems that can effectively respond to varying fire source scenarios. [ABSTRACT FROM AUTHOR]

The Aeroacoustics Laboratory in the Department of Aerospace Engineering at Penn State currently serves several areas of experimental research. Most notable in the laboratory is the Anechoic Chamber of which the Aeroacoustics Wind Tunnel is an integral part. In recent years the dominant areas of research have included model aircraft exhaust jets and model rotors for helicopter applications involving detailed noise experiments. In the jet noise area, the applications have included aircraft in both flyover and take-off configurations. In the flyover application the air flow surrounding the exhaust jet has a significant effect on the radiated noise and must be simulated to produce experimental results that will be most useful in preliminary design of noise suppression applications. The Aeroacoustics Wind Tunnel at Penn State serves the purpose for this simulation. During aircraft take-off, the aircraft airspeed is in a range exceeding 250 ft per second, or Mach number of over M = 0.22. In the years preceding 2022, the velocity of the free jet flow of the Penn State facility was limited to less than 200 ft/sec. This paper reports on a project to design upgrades to the existing wind tunnel to improve the test section flow velocity to values closer to the 250 ft/sec target. The approach began with a preliminary design of the return flow ducting to convert the open jet, open return wind tunnel to a closed return tunnel. The concept is to make use of the flow energy in the exhaust of the tunnel to boost the input energy to the inlet fan that drives the flow to the test section. An integral part of the preliminary design involved making use of an upgraded flow analysis computer code to predict the gain in test section velocity of the new facility. For the available horsepower of two fans in the facility, the configurations of the existing and upgraded wind tunnel were entered into this analysis code based on a quasi-one-dimensional formulation. The code included empirical data formulated to include the various shapes of the components of the tunnels. The relative flow velocities in each section used simple incompressible continuity to calculate all velocities in the component sections. The average dynamic pressure in each section is calculated from the flow (constant) density and the velocity squared. Each section had a non-dimensional pressure loss parameter calculated from empirical data (from the relevant literature). The basic code (using the Excel algorithms) was based on a predictor-corrector concept in which the calculation was initialized with the estimated velocity and pressure of the flow at the entrance to the test section. The loss in each following section is estimated to determine the loss in the total pressure and the cumulated loss compared to the gains made at the two fans in the circuit. The initial guess is adjusted based on the total pressure value at the end of the circuit. During the related experiments, measurements of the total and dynamic pressure were performed at several joints between sections and compared to the values predicted in the analysis code. Various settings of the horsepower of the drive fans were used and the results were compared to flow measurements for the tunnel configurations (predominantly for the open return and closed return tunnel setups available before and after the upgrade project.) Results of the analysis and experiments are presented and analyzed together with the remaining activities planned for the coming months. [ABSTRACT FROM AUTHOR]

When there is a fire in a tunnel, the heat released by the combustion is difficult to dissipate and the temperature inside the tunnel would rise rapidly. Longitudinal ventilation (LV) has been commonly adopted as the smoke control strategy in tunnel fires, which is essential to safeguard the tunnel structure and the trapped people. Besides the smoke control method by LV, the water mist system (WMS) can provide a powerful cooling effect for the high-temperature smoke in the tunnel. This article aims to investigate the impact of WMS on the smoke back-layering (BL) length with LV and the mutual effect process between the smoke spread and the WMS. The findings show that the BL length is restricted more effectively by the combined action of water mist and LV. Upon activation of the WMS, the water mist's effect inhibits the smoke's ability to spread upstream and causes the smoke layer to settle down, which disturbs the stability of the smoke layer. An unstable layer of smoke is more likely to be blown downstream by longitudinal ventilation. All water mist particle diameters show a significant reduction in smoke back-layering with an increased flow rate. The BL length would gradually reduce as the particle diameter is decreased. The tendency of flow rate and particle diameter on the BL length shows similar effects to the critical velocity (V cr). The V cr is reduced with the rising flow rate and increased with expanding particle diameter. [ABSTRACT FROM AUTHOR]

The Thu Thiem road tunnel located deep under the Saigon River is currently ventilated by a system of 12 jet fans that push dust and dirty air out into the environment. These jet fans are driven by Induction Motors (IMs) modeled by mathematical equations on the structural nonlinear dq coordinate system, so the conventional linear controllers partly fail to meet the response requirements. Therefore, this paper proposes the application of the exact linearization control method for the current loop in the Field Oriented Control (FOC) structure of an IM that drives a jet fan of the Thu Thiem road tunnel. This is a control method based on a linearization model with cascaded loops. The stator current controller controls two currents: isd controls the flux, and isq controls the torque. The control design is verified by the simulation results on Matlab/Simulink with data collected from the jet fan system of the Thu Thiem road tunnel. [ABSTRACT FROM AUTHOR]

The design of anchor bolt in tunnel engineering mostly depends on empirical method and analogy method. In order to study the mechanical effect of surrounding rock in prestressed anchor bolt support system, a mechanical coupling model of prestressed anchor bolt and surrounding rock is established. Considering the damage effect of surrounding rock excavation, the analytical expressions of stress distribution and radial displacement of surrounding rock after tunnel excavation are derived by elastic-plastic mechanics theory. The finite difference software FLAC3D is used to verify and analyze the influence of prestressed anchor parameters on the state of surrounding rock. The results show that the maximum tangential stress and the radius of plastic zone of surrounding rock in theoretical analysis and numerical simulation are 4.77 MPa, 15 m and 4.49 MPa, 15.86 m respectively. The stress distribution and displacement of tunnel surrounding rock calculated by theoretical analysis and numerical simulation are basically the same. The rationality of theoretical analytical solution is verified in IV and V grade surrounding rock strata. With the increase of pre-tightening force, the radial displacement of surrounding rock in plastic zone and the radius of plastic zone gradually decrease, while the elastic zone is basically unaffected. When the length of the free section of the bolt is located in the plastic zone, the radial displacement of the plastic zone and the radius of the plastic zone of the surrounding rock gradually decrease with the increase of the length of the bolt. In practical engineering, the pre-tightening force of bolt should be increased as much as possible. The increase of bolt length has limited control effect on the displacement of surrounding rock and the development of plastic zone. The length of free section of bolt should be controlled in plastic zone. [ABSTRACT FROM AUTHOR]

The cumulative length of subways and tunnels in China has reached nearly 25 000 kilometers, bringing huge demand for underground construction. The monitoring for construction safety has become more significant, due to complicated environment and rapid-onset natural disasters, which raises the frequency of accidents in underground construction. The informatization engineering of monitoring and early-warning on natural disasters is built to achieve construction safety, through promoting integrated monitoring on multi-hazard and disaster chains, and practicing intelligent algorithms on comprehensive quick accurate perception and early-warning of construction hazards. The integrated network architecture for intelligent safety monitoring with edge-computing ability is established, realizing the visualization of monitoring data analysis through researches on AD hoc transmission based on directional antenna network bridge, development of IoT edge computing software and researches on accessing to IoT platform for multiple types of sensors, and development of the front-end and back-end of the monitoring system. The introduction of IoT and cloud computing sustains accessing to platform for huge amount of sensors and full exploiting of big-data mining, improving intelligent safety hazard identification, and reducing safety risks in construction. Based on the instant response of edge devices and interval data acquisition of sensors, and the capability for more than 100 000 sensors to access the system simultaneously, the complete monitoring system for underground constructions with second-level warning is established. [ABSTRACT FROM AUTHOR]

The aircraft wake vortex is an important factor affecting flight safety; as an important part of the aircraft, the powered nacelle will inevitably have an important impact on the aircraft wake vortex, so it is of great practical significance to research it. The present study focused on the numerical simulation of the wake flow of large aircraft (as the front aircraft) and the comparative analysis of the influence of engine jets on the wake flow. In order to meet the accuracy requirements and control the consumption of computing resources, LES and RANS methods were compared, and the RANS method was finally selected for subsequent calculation. The dynamic effect of jet flow was simulated by simplifying the boundary conditions of the inlet fan and outlet bypass as the mass flow boundary condition. The simulation results showed that the engine nacelle will have a significant impact on the morphology of the aircraft wake flow (position and strength of the main vortex in the wake flow system), which is caused by the vortices formed under the shear flow and separated flow of the nacelle. However, the nacelle will not significantly change the total strength of the wake vortex (half-plane circulation). The engine jet intensity causes additional turbulent mixing, which will accelerate the fusion of the nacelle vortex and ultimately change the intensity ratio of the inner wing vortex and the wingtip vortex, affecting the trajectory of the wake of the mean vortex. The study provides a corresponding reference for the following research on a wake vortex by a powered nacelle. [ABSTRACT FROM AUTHOR]

The full‐scale façade standard test is widely employed as a comprehensive method to assess the façade fire spread. Within this approach, the calibration test without combustible façade decouples the intricate interaction between gas‐phase combustion and material pyrolysis, which simplifies diagnostics and provides an ideal scenario for model validation. This paper presents large eddy simulations (LES) accompanied by comparisons of calibration tests in accordance with JIS A 1310. The calibration tests were conducted to obtain the flame morphologies, gas‐phase temperature, and heat flux of over‐ventilated façade fires, and the LES modeling is complemented by the modified eddy dissipation model for combustion, the one‐equation model for the sub‐grid scale turbulence, and the discrete ordinate method with the gray mean absorption‐emission approach for thermal radiation. The accuracy of LES data is discussed by comparing with measurements, and the mesh resolution is optimized as 2.5 cm for achieving mesh independency with good qualitative agreement. Furthermore, simulations are conducted to investigate the impact of sidewall distances on façade flame spread. The results highlight that the enhancement of sidewall in façade flame spread occurs under external heat release rate, and the 0.2 m sidewall distance for the designated JIS test is identified as a critical threshold increasing façade thermal load. [ABSTRACT FROM AUTHOR]

In the construction process of tunnel inlet sections, the rock mass can sustain unsymmetrical pressure due to asymmetrical terrain on the two sides of the tunnel. The fact that the inlet sections are usually under shallow buried conditions with strongly weathered rock mass exacerbates the issue. This paper discusses optimization strategies of the initial support of a shallow buried tunnel based on the analytical results of asymmetrical loading characteristics. Numerical simulation is performed with particle flow code (PFC) using the Jianshanji tunnel project as an example. The simulation results show that the bench excavation has slightly less total deformation than the full-section excavation but the deformation range is wider, especially in the tunnel arch. Both lining support and slope reduction treatments can effectively improve rock deformation, with lining support demonstrating better performance in controlling deformation and adjusting stress distribution. Based on the simulation results, the bench excavation and lining support are used in the actual project, and the corresponding optimization control measures were adopted to address deformation issues, including crushed-stone backfilling for compression resistance, advanced grouting reinforcement, and grouting. The field data show that the tunnel stability is effectively improved by adopting the optimization schemes, which further validates the effectiveness of the proposed unsymmetrical control method. [ABSTRACT FROM AUTHOR]

In open-cut assembled subway tunnels, foundation pit enclosure piles are typically cast in place. However, this conventional approach limits the functionality of the piles to serving as retaining structures during excavation, resulting in resource inefficiency and the underutilization of prefabrication techniques. To address this issue, a fully prefabricated pile-wall composite scheme is proposed for cut-and-cover tunnels to optimize the retaining effect of the piles and leverage the benefits of prefabricated technology. In this scheme, the retaining pile and lining are both prefabricated. The pile is the temporary retaining structure during pit excavation and a part of the sidewall. This scheme was researched and applied in Jinan, China. Field monitoring and numerical simulation were used to investigate the load transfer within the fully prefabricated pile-wall composite structure (PPWS) and its mechanical response, respectively. The results show: (1) The development of lateral earth pressures on the PPWS experienced three stages. The lateral earth pressure distribution indicates that the PPWS can fully activate the retaining effect of precast piles. (2) Following the backfilling of the joints, the horizontal displacement at the bottom of the precast pile reduced by 0.39 mm. Numerical simulation results indicate the effectiveness of precast pile restraint in PPWS. (3) The PPWS exhibited uniform deformation transition at the joints. The joints play a crucial role in coordinating deformation between the precast piles and sidewalls, utilizing the restraining effect of the precast piles. [ABSTRACT FROM AUTHOR]

Despite its perceived historical rarity, fire is an important disturbance in tropical rainforests. Very large rainforest fires have been observed multiple times in recent decades, often during years of strong El Niño‐Southern Oscillation droughts. Fire in rainforest has major short‐term consequences for humans and wildlife by converting forest to fire‐prone fern, shrub, and grass, but the long‐term effects remain to be seen. Borneo's indigenous groups have been using fire to clear land for centuries, yet the prevalence and spatial patterns of premodern fire across forest types in Borneo are not well understood. This research set out to reconstruct fire in a 1500‐ha primary rainforest spanning 800 m of elevation in Indonesian Borneo with the goal of elucidating the role humans have played in rainforest fire. We found that humans played an important role in the occurrence of fire in recent centuries. Evidence of fire—charcoal >2 mm—is more abundant in forest types where humans would be more likely to live and/or practice swidden agriculture. However, pyrogenic material is ubiquitous across the study area, showing that all forest types have experienced fire. A set of 50 radiocarbon dates showed that in lowland areas—where human‐caused fire is most likely—fire occurred throughout the last 3200 years, peaking 1300–1600 ce. The upland areas lacked evidence of fire before 1250 ce but otherwise had a similar pattern to the lowlands. The period of high fire coincides with regional demographic changes as well as regional droughts documented elsewhere in Southeast Asia. In upland areas, fires likely burned only under regional drought when fires could more easily spread upslope. Although forest plot studies at this site show little structural evidence of past fires, tree diversity is lower than expected in the most burned areas (alluvial benches). Thus, our results suggest that land clearance was a major source of fire, but the current intact state of these rainforests indicates that they were largely resilient to fires and land use hundreds of years ago. Recent fires mirror patterns of fire spread that occurred hundreds of years ago, though their severity and extent are likely much greater. [ABSTRACT FROM AUTHOR]

To obtain the heat exchange situation and energy saving potential in the tunnel during winter ventilation, a numerical simulation study was conducted to investigate the temperature distribution characteristics in the extra-high voltage power tunnel with extra-long ventilation interval when the outdoor air temperature is from 1 °C to 12 °C in winter. The user-defined programs of ANSYS Fluent 19.2 software were used to complete the simulation of the entire length of the power tunnel. The heat transfer characteristics of the tunnel in winter and the potential for energy saving in ventilation were analyzed, and the critical ventilation volume that can achieve the maximum energy saving effect in winter was defined and given. The results show that the power tunnel with extra-long ventilation interval has a potential to reduce the ventilation volume and thus realize energy saving. The soil is exothermic in the front section of power tunnels and endothermic in the back section in winter. Soil heat release is affected by outdoor air temperature, while soil heat absorption is affected by the outdoor air temperature and the ventilation volume. The lower the outdoor temperature in winter, the smaller the critical ventilation volume, and the greater the potential for ventilation energy saving. When the outdoor temperature is from 1 °C to 12 °C in winter, the maximum possible energy saving rate is 91%. [ABSTRACT FROM AUTHOR]

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