• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.341-351
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• 2015

When rainfall occurred on road tunnel, that is likely to have influence upon ventilation force in the tunnels but the tunnels ventilation system did not consider factors of rainfall. Thus, this study investigated effects of rainfall upon ventilation force in the tunnels at no rainfall and changing of rainfall by 3 dimensional numerical method. Flow rate into road tunnels decreased as many as 52.34% at rainfall of 150 mm/hr, and pressure drop of road tunnel between entrance and exit decreased as many as 22.22%, so that rainfall had influence upon ventilation force in the tunnel. The number of necessary jet fan in road tunnels is 12 at no rainfall but, when rainfall of 80 mm/hr on road tunnels, the number of necessary jet fan in road tunnels is 16, when rainfall of 150 mm/hr on road tunnels, the number of necessary jet fan in road tunnels is 17. So, factor of rainfall should be considered at estimation of ventilation system of road tunnel.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.3
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• pp.393-404
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• 2017

Side jet effect on the aerodynamic characteristics of a missile was investigated using experimental and computational methods. A couple of side jets were injected toward outward downstream at mid point of missile body. Cold air jet was used in the wind tunnel test, and cold and hot jet were used in the computation. Wind tunnel test was carried out with jet and without jet, and calculation was performed for three cases ; no jet, cold air jet, and hot mixture gas jet. From the comparison of measured and calculated data for all cases, two points could be deduced. Firstly, side jet made static stability to be unstable by increasing body normal force near the side jet exit and by decreasing tail normal force. Secondly, hot mixture gas had more significant effect on the static stability of a missile-type body than cold air jet.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2207-2212
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• 2008

The next generation of Korean high-speed train under development will be designed for the maximum operating speed of 350km/h and maximum speed of 400km/h. This high-speed operation may cause the noise and vibration problems around tunnel exit due to the higher micro-pressure wave than present level. In this study, the nose shape optimization was conducted for the countermeasure against these problems. Axi-symmetric solver was used for numerical simulation, and response surface was used for efficiency of optimization process. Also the multi-step optimization was conducted to find out more accurate optimal shape. Through these analysis and optimization, it was found out that the optimal nose shapes for minimization of micro-pressure wave are definitely different along the nose length variation. And the mechanism of micro-pressure wave reduction was closely investigated by the analysis of generation process of compression wave in tunnel. The results are expected to be used as design guideline for performance improvement of the next generatin of Korean high-speed train.

• Journal of Korean Society of Transportation
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• v.27 no.1
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• pp.17-25
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• 2009

This research analyzed the changes of drivers' visual workload with beta wave of bionic signals from brain's occipital lobe from entrance to exit section of the Yuksimnyeong tunnel which is 3.1km long in Daejeon-Tongyeong section of Jungbu expressway. There are 10 subjects who Participate our experiments and the results are as follows. First. the drivers' visual workload is higher about 41% in entrance section of the tunnel than 200m in advance of the section of the tunnel. Second, it is higher than 200m in advance of the section of the tunnel by 34.5% that the value of the drivers' visual workload who is driving in the tunnel. Third, as a result of analyzing the tunnel into 200m unit section, it is statistically different from other sections' at the 1.0km and 2.4km section from the entrance of the tunnel. If drivers sustain average visual workload for safe driving in very long tunnel, it's not desirable environment that drivers' visual workload goes under the average workload. Therefore, it would be the section where drivers who is driving in tunnel could cause a traffic accident.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.4
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• pp.28-36
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• 2024

In this study, an analytical evaluation of evacuation safety in typical road tunnels was conducted. The Fire Dynamics Simulator (FDS) was employed to perform fire simulations with varying fire sizes to determine the allowable evacuation time in road tunnels. Additionally, evacuation simulations were performed using Pathfinder, considering the width of barrier doors and the spacing of evacuation passageways, to calculate the required evacuation time. A comparison between the allowable and required evacuation times was conducted to assess the impact of fire size, passageway spacing, and barrier door width on tunnel evacuation safety. The results from the fire and evacuation simulations indicated that an increase in fire size and passageway spacing, along with a decrease in door width, resulted in an increase in the number of casualties. Conversely, increasing the barrier door width to more than 1.2meters led to a reduction in casualties as passageway spacing increased.

• Fire Science and Engineering
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• v.25 no.3
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• pp.51-56
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• 2011

The full-scale experiments are carried out to investigate the fire suppression characteristics of water-based fire fighting systems in a road tunnel. Applied systems are the low-pressure water spray system at 3.5 bar and the high-pressure water mist system at 60 bar. The water flow rate of the high-pressure system is one sixth only of the water spray system. A passenger car and a heptane fuel pan with area of $1.4m^2$ are used as fire sources. A blower system is installed at the tunnel exit to realize the longitudinal ventilation conditions (0.9~3.8 m/s) in the tunnel. Temperatures from the fire source to the down-stream direction are measured by K-type thermocouple trees. The experimental results show that the cooling effect of the high pressure water mist system in the test conditions were equivalent to that of the low pressure water spray system for B-class fire.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.5
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• pp.136-143
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• 2010

There are three parts of tunnel which are influenced by outside temperature, entrance, exit and vent. These parts showed different tendency of deterioration(very rapid deterioration speed, wide range of defects, etc) compared with last parts of tunnel. Therefore, it needs to have different points of view when civil engineers analyze the defects on these parts and apply the retrofit or rehabilitation methods for them. However, when we conduct maintenance works, precise inspection and precise safety diagnosis, these defects had been neglected because those were considered as unimportant defects and caused from temporary weather and temperature change. In this study, two urban tunnels were analyzed to decide the range of tunnel which are influenced by outside temperature using a thermal camera, and to find out the causes of defects on these parts. From the results, the main points of maintenance were presented.

• Fire Science and Engineering
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• v.18 no.2
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• pp.49-56
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• 2004

Today's popular ventilation systems include the combined jet fans and electrostatic precipitation systems or the combined jet fans and vertical shaft system. Tunnels with these two ventilation systems applied have been designed and opened, more and more interest has been put in maintenance of a tunnel after opening. Therefore. it is to become more important to come up with the optimal operation mode and the method for the evaluation of ventilation system. In this study, to evaluate a tunnel ventilation and its economy, a dynamic simulation program was developed which can simulate the unsteady-state tunnel air velocity and concentration of pollutants according to the traffic flow variations and operation condition of a ventilation system. We clarified the effectiveness usage on tunnel ventilation by using it and also we could found the most economical ventilation operation mode by application in real exit tunnel. We obtained that combination of fan system and electrostatic precipitation system was more economical than jet fan priority operation mode.

• Geomechanics and Engineering
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• v.32 no.1
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• pp.111-123
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• 2023

The slope of an open cut tunnel is located above the exit of the Leijia tunnel on the Changgan high-speed railway. During the excavation of the open cut tunnel foundation pit, the slope slipped twice, a large landslide of 92500 m³ formed. The landslide body and unstable slope body not only caused the foundation pit of the open cut tunnel to be buried and the anchor piles to be damaged but also directly threatened the operational safety of the later high-speed railway. Therefore, to study the stability change in the slope of the open cut tunnel under heavy rain and excavation conditions, a 3D numerical calculation model of the slope is carried out by Midas GTS software, the deformation mechanism is analyzed, anti-sliding measures are proposed, and the effectiveness of the anti-sliding measures is analyzed according to the field monitoring results. The results show that when rainfall occurs, rainwater collects in the open cut tunnel area, resulting in a transient saturation zone on the slope on the right side of the open cut tunnel, which reduces the shear strength of the slope soil; the excavation at the slope toe reduces the anti-sliding capacity of the slope toe. Under the combined action of excavation and rainfall, when the soil above the top of the anchor pile is excavated, two potential sliding surfaces are bounded by the top of the excavation area, and the shear outlet is located at the top of the anchor pile. After the excavation of the open cut tunnel, the potential sliding surface is mainly concentrated at the lower part of the downhill area, and the shear outlet moves down to the bottom of the open cut tunnel. Based on the deformation characteristics and the failure mechanism of the landslides, comprehensive control measures, including interim emergency mitigation measures and long-term mitigation measures, are proposed. The field monitoring results further verify the accuracy of the anti-sliding mechanism analysis and the effectiveness of anti-sliding measures.

• International Journal of Fluid Machinery and Systems
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• v.10 no.1
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• pp.19-29
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• 2017

An objective of this study is to demonstrate the validity of using a small wind turbine to recover the fluid energy flowing out of an exhaust duct for the generation of power. In these experiments, a butterfly wind turbine of a vertical axis type (D = 0.4 m) is used. The output performance is measured at various locations relative to the exit of a small wind tunnel (W = 0.65 m), representing the performance expected in an exhaust duct flow. Two-dimensional numerical analysis qualitatively agrees with the experimental results for the wind turbine power coefficient and rate of energy recovery. When the turbine is far from the duct exit (more than 2.5 D), an energy recovery rate of approximately 1.3% is obtained.