In recent years the tunnel construction is increasing worldwide because of development of science and technology and increasing of transportation demand. Tunnels are complex structures normally rectangular cross section or semicircular and constructed to connect between different sections of roads. Because of the importance, the construction and extension of road tunnels are also continuously increasing along with the development. According to data from the Korea Expressway Corporation, the number of road tunnels, which was 1,332 in 2010, increased rapidly by about 2.1 times over 10 years to a total of 2,742 in 2020. The extension of road tunnels is also on the trend of increasing, with a total of 945 km in 2010 reaching 2,157 km in 2020. The benefits of a double-deck tunnel are emphasized, particularly in terms of construction cost and convenience. This tunnel design incorporates a central slab, dividing the tunnel into upper and lower spaces. The versatility of a double-decker tunnel is evident in its ability to accommodate various uses for both levels. For instance, the upper level can function as vehicle roads, while the lower level can be designated for train tracks. In this study, the effect of RWS and modified hydrocarbon fire curve was applied to the concrete tunnel bracket through simulation to analyze the temperature after the fire occurrence.

본 연구는 특수한 조건에서의 줄눈 콘크리트포장의 설계 및 성능에 관한 분석을 목적으로 한다. 줄눈 콘크리트포장은 시멘트 콘크리트 포장의 한 형태로, 오랜 기간 도로 포장형식으로 사용되어 왔다. 이 포장 방식은 철근을 사용하지 않는 대신, 콘크리트 슬래브의 균열을 줄눈을 통해 유도하고, 다월바와 타이바를 통해 슬래브에 생기는 응력을 줄이는 방식이 다. 대한민국의 다양한 지역 환경과 계절적 특성은 도로 포장설계에 주요한 인자로 적용된다. 특히, 슬래브의 부등건조수 축이 평탄성 문제의 주요 원인으로 지적되며, 이는 온습도의 변화에 의해 발생한다. 본 연구에서는 3차원 유한요소해석 을 활용하여 줄눈 콘크리트포장 슬래브의 거동을 분석하고, 콘크리트 슬래브의 두께, 줄눈 간격, 타이바 및 다웰바의 배 치 등 주요 설계 변수의 영향을 평가한다. 이러한 설계 인자들이 슬래브의 응력과 변위에 미치는 영향을 확인하며, 다양 한 환경 조건 하에서의 설계 방법의 유효성을 검증한다. 본 연구는 줄눈 콘크리트포장의 실제 배치 방식을 모델링하여, 기존 설계 방식의 보안 사항을 파악하고, 설계 기준 내에서의 주요 인자 변화를 통해 부등건조수축을 완화할 수 있는 방 안을 제시한다. 이를 통해, 특수 환경 조건에서의 온습도 영향을 고려한 효율적인 포장 설계 방안을 도출함으로써, 도로 포장의 평탄성과 내구성 향상에 기여하고자 한다.

PURPOSES : This study aimed to identify factors affecting the duration of traffic incidents in tunnel sections, as accidents in tunnels tend to cause more congestion than those on main roads. Survival analysis and a Cox proportional hazards model were used to analyze the determinants of incident clearance times. METHODS : Tunnel traffic accidents were categorized into tunnel access sections versus inner tunnel sections according to the point of occurrence. The factors affecting duration were compared between main road and tunnel locations. The Cox model was applied to quantify the effects of various factors on incident duration time by location. RESULTS : Key factors influencing mainline incident duration included collision type, driver behavior and gender, number of vehicles involved, number of accidents, and post-collision vehicle status. In tunnels, the primary factors identified were collision type, driver behavior, single vs multi-vehicle involvement, and vehicles stopping in the tunnel after collisions. Incidents lasted longest when vehicles stopped at tunnel entrances and exits. In addition, we hypothesize that incident duration in tunnels is longer than in main roads due to the reduced space for vehicle handling. CONCLUSIONS : These results can inform the development of future incident management strategies and congestion mitigation for tunnels and underpasses. The Cox model provided new insights into the determinants of incident duration times in constrained tunnel environments compared to open main roads.

PURPOSES : This study investigates the factors affecting extra-long tunnel accidents by integrating data on tunnel geometry, traffic flow, and traffic accidents and derives the underlying implications to mitigate the severity of accidents. METHODS : Two processes centered on three key data points (tunnel geometry, traffic flow, and traffic accidents) were used in this study. The first is to analyze the spatial characteristics of extra-long tunnel traffic accidents and categorize them from multiple perspectives. The other was to investigate the factors affecting extra-long tunnel traffic accidents using the equivalent property-damage-only (EPDO) of individual accidents and the aforementioned data as the dependent and independent variables, respectively, by employing an ordered logistic regression model. RESULTS : Gyeonggi-do, Gyeongsangnam-do, and Gangwon-do are three metropolitan municipalities that have a significant number of extra-long tunnel accidents; Busan and Seoul have the most extra-long tunnel accidents, accounting for 23.2% (422 accidents) and 18.6% (339 accidents) of the 1,821 accidents that occurred from 2007 to 2020, respectively. In addition, approximately 70% of extra-long tunnel traffic accidents occurred along tunnels with lengths of less than 2 km, and Seoul and Busan accounted for over 60% of the top 20 extra-long tunnels with accidents. Most importantly, the Hwangryeong (down) tunnel in Busan experienced the most extra-long tunnel traffic accidents, with 77 accidents occurring during the same period. As a result of the ordered logistic regression modeling with EPDO and multiple independent variables, the significant factors affecting the severity of extra-long tunnel traffic accidents were determined to be road type (freeway, local route, and metropolitan city road), traffic flow (speed), accident time (year, summer, weekend, and afternoon), accident type (rear end), traffic law violations (safe distance violation and center line violation), and offending vehicles (van, sedan, and truck). CONCLUSIONS : Based on these results, the following measures and implications for mitigating the severity of extra-long tunnel traffic accidents must be considered: upgrading the emergency response level of all road types to that of freeways and actively promoting techniques for regulating high-speed vehicles approaching and traversing within extra-long tunnels are necessary. In addition, the emergency response and preparation system should be reinforced, particularly when the damage from extra-long tunnel traffic accidents is more serious, such as during the summer, weekends, and afternoons. Finally, traffic law violations such as safe distance and centerline violations in extra-long tunnels should be prohibited.

PURPOSES : In this study, a model was developed to estimate the concentrations of particulate matter (PM2.5 and PM10) in expressway tunnel sections. METHODS : A statistical model was constructed by collecting data on particulate matter (PM2.5 and PM10), weather, environment, and traffic volume in the tunnel section. The model was developed after accurately analyzing the factors influencing the PM concentration. RESULTS : A machine learning-based PM concentration estimation model was developed. Three models, namely linear regression, convolutional neural network, and random forest models, were compared, and the random forest model was proposed as the best model. CONCLUSIONS : The evaluation revealed that the random forest model displayed the least error in the concentration estimation model for (PM2.5 and PM10) in all tunnel section cases. In addition, a practical application plan for the model developed in this study is proposed.

PURPOSES : This study provides fundamental information on the temperature variations in tunnel structures during severe fire events. A fire event in a tunnel can drastically increase the internal temperature, which can significantly affect its structural safety. METHODS : Numerical simulations that consider various fire conditions are more efficient than experimental tests. The fire dynamic simulator (FDS) software, based on computational fluid dynamics (CFD) and developed by the National Institute of Standards and Technology, was used for the simulations. The variables included single and multiple accidents involving heavy goods vehicles carrying 27,000 liters of diesel fuel. Additionally, the concrete material characteristics of heat conductivity and specific heat were included in the analysis. The temperatures of concrete were investigated at various locations, surfaces, and inside the concrete at different depths. The obtained temperatures were verified to determine whether they reached the limits provided by the Fire Resistance Design for Road Tunnel (MOLIT 2021). RESULTS : For a fire caused by 27,000 liters of diesel, the fire intensity, expressed as the heat release rate, was approximately 160 MW. The increase in the carrying capacity of the fire source did not significantly affect the fire intensity; however, it affected the duration of the fire. The maximum temperature of concrete surface in the tunnel was approximately 1400 ℃ at some distance away in a longitudinal direction from the location of fire (not directly above). The temperature inside the concrete was successfully analyzed using FDS. The temperature inside the concrete decreased as the conductivity decreased and the specific heat increased. According to the Fire Resistance Design for Road Tunnel (MOLIT 2021), the internal temperatures should be within 380 ℃ and 250 ℃ for concrete and reinforcing steel, respectively. The temperatures were found to be approximately 380 ℃ and 100 ℃ in mist cases at depths of 5 cm and 10 cm, respectively, inside the concrete. CONCLUSIONS : The fire simulation studies indicated that the location of the maximum temperature was not directly above the fire, possibly because of fire-frame movements. During the final stage of the fire, the location of the highest temperature was immediately above the fire. During the fire in a tunnel with 27,000 liters of diesel, the maximum fire intensity was approximately 160 MW. The capacity of the fire source did not significantly affect the fire intensity, but affected the duration. Provided the concrete cover about 6 cm and 10 cm, both concrete and reinforcing steel can meet the required temperature limits of the Fire Resistance Design for Road Tunnel (MOLIT 2021). However, the results from this study are based on a few assumptions. Therefore, further studies should be conducted to include more specific numerical simulations and experimental tests that consider other variables, including tunnel shapes, fire sources, and locations.

This study attempted to analyze the comparative advantage in terms of disaster safety costs in verifying the effectiveness and economic feasibility of the high-performance water-bulwark system in the pole tunnel, which was recently promoted as a part of the acceleration of vehicles. The tunnel to be analyzed was divided into a short tunnel(Anyang, Cheonggye) and a long tunnel(Suraksan, Sapaesan). As a result, it was analyzed that 25% of the improvement effect would occur if one lane was secured by applying the Water-Bulwark System. It was analyzed that this is because the time value cost, which accounts for a large proportion of the traffic congestion cost of short tunnels and pole tunnels, differs depending on the congestion time and traffic volume, not the length of the tunnel.

This paper presents a computational fluid dynamics (CFD) analysis to investiagate the effect of expansion chamber on overpressure reduction in protective tunnels subjected to detonation of high explosives. A commercial CFD code, Viper::Blast, was used to model the blast waves in a protective tunnel with a length of 160 m, width of 8.9 m and height of 7.2 m. Blast scenarios and simulation matrix were establihsed in consideration of the design parameters of expansion chamber, including the chamber lengths of 6.1 m to 12.1 m, widths of 10.7 m to 97 m, length to width ratios of 0.0 to 5.0, heights of 8.0 m and 14.9 m, and ratios of chamber to tunnel width of 1.2 to 10.9 m. A charge weight of TNT of 1000 kg was used. The mesh sizes of the numerical model of the protective tunnel were determined based on a mesh convergence study. A parametric study based on the simulation matrix was performed using the proposed CFD tunnel model and the optimized shape of expansion chamber of the considered tunnel was then proposed based on the numerical results. Design recommendations for the use of expansion chamber in protective tunnel under blast loads to reduce the internal overpressures were finally provided.