• Journal of the Korea Academia-Industrial cooperation Society
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• v.12 no.4
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• pp.1796-1802
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• 2011

In this paper, the radio propagation path loss prediction simulator in tunnel was developed. It used a image theory method for analysing precise radio propagation path. And it can predict radio propagation path loss in straight and curved tunnels. The simulator can plot realtime radio propagation paths using various parameters which was input by user. And it can simulate from changing transmitter and receiver positions. The predicted path loss of simulator was compared with the measurements in Chunhyun tunnel and confirmed the validity.

• Tunnel and Underground Space
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• v.11 no.4
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• pp.289-300
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• 2001

In the design of tunnel, it contains inaccuracy of data, fuzziness of evaluation, observer error and so on. The face observation during tunnel excavation, therefore, plays an important role to raise stability and to reduce supporting cost. This study is carried out to minimize the subjectiveness of observer and to exactly evaluate the natural properties of ground during the face observation. For these purpose, fuzzy set theory and neuro-fuzzy techniques in artificial intelligent techniques are applied to the inference of the RMR value from the observation data. The correlation between original RMR vague and inferred RM $R_{_FU}$ and RM $R_{_NF}$ values from fuzzy set theory and neuro-fuzzy techniques is investigated using 46 data. The results show that good correlation between original RMR value and infected RM $R_{_FU}$ and RM $R_{_NF}$ value is observed when the correlation coefficients are ｜R｜=0.96 and ｜R｜=0.95 respectively. From these results, applicability of fuzzy set theory and neuro-fuzzy techniques to rock mats classification is proved to be sufficiently high enough. enough.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.427-432
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• 1999

When a high-speed train enters a tunnel, a compression wave is generated. This wave subsequently emerges from the exit portal of the tunnel, which causes an impulsive noise called 'Sonic boom' or 'micro-pressure wave'. In the present study, new method is presented for prediction of sonic boom noise, especially focusing on the effect of the nose shape of the train on the resultant noise. Acoustic theory for monopole source is used to represent a nose shape of the train in wave equation. Compression wave propagation in tunnel considering tunnel track condition and emission of sonic boom was calculated. The predicted compression waves and impulsive sound waves are compared with recent measurements, and show reasonable agreements.

• Journal of Institute of Convergence Technology
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• v.11 no.1
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• pp.25-28
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• 2021

Recently, the fire safety of road tunnels has been important issues in South Korea. However, proper fire safety regulations has not made for road tunnels. Due to geographical challenges in South Korea, road tunnels should be constructed to secure stable traffic flows. In the Guidelines for Installing and Managing Disaster Prevention Facilities of Road Tunnels (NFSC 603), main target vehicles are passenger cars. This guidelines cannot support big fires from larger vehicles such as cargo, oil trucks. In this study, fire safety for a road tunnel in port area was analyzed with fire dynamics theory under cargo truck fire scenario. Sujunsan road tunnel in Busan city was chosen as a target tunnel, which links between Busan port and highways to increase cargo shipping. The results show the limitations of present guidelines (NFSC 603) for road tunnel from large fire situations.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.10a
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• pp.153-160
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• 1999

It has been recognized that the assessment of concrete lining is very uncertain and subjective depending on the engineers who are in charge. T-FLAS which was based on fuzzy theory was developed in this study for the quantitative and objective assessment of the concrete lining in tunnels. Based on the application of T-FLAS on the evaluated field data, it was shown that the assessment system using fuzzy theory(T-FLAS) can be the effective and objective method for the assessment of concrete lining.

• Proceedings of the Korean Geotechical Society Conference
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• 1995.03a
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• pp.161-174
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• 1995

• Tunnel and Underground Space
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• v.3 no.1
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• pp.80-95
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• 1993

Convergence measurements play very important role in the assessment of stability of a tunnel and of the economics of rock reinforcements. The characteristics of convergences are both due to the face advance effect and the time-dependent behaviour of rocks. As the convergence law can be modeled as a specific function of two variables of distance and time, we can determine the type of function and the related parameters from the field measurements. By using the regression method based on the Levengberg-Marquardt algorithm, an analysis of convergence of two different tunnels and one numerical example is described. It is shown that the convergence can be modeled as following function, C(x)=a{1-exp(-bx)} or C(t)=a{1-exp(-bt)} in case of a tunnel excavated in elastic rocks, in case of elasto-plastic or over stressed rocks.

• Geomechanics and Engineering
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• v.12 no.2
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• pp.313-326
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• 2017

Based on the reliability theory and limit analysis method, the roof stability of a shallow tunnel is investigated under the condition of surface settlement. Nonlinear Hoek-Brown failure criterion is adopted in the present analysis. With the consideration of surface settlement, the internal energy and external work are calculated. Equating the rate of energy dissipation to the external rate of work, the expression of support pressure is derived. With the help of variational approach, a performance function is proposed to reliability analysis. Improved response surface method is used to calculate the Hasofer-Lind reliability index and the failure probability. In order to assess the validity of the present results, Monte-Carlo simulation is performed to examine the correctness. Sensitivity analysis is used to estimate the influence of different variables on reliability index. Among random variables, the unit weight significantly affects the reliability index. It is found that the greater coefficient of variation of variables lead to the higher failure probability. On the basis of the discussions, the reliability-based design is achieved to calculate the required tunnel support pressure under different situations when the target reliability index is obtained.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.67 no.9
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• pp.1249-1256
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• 2018

For the screening factor of the tunnel and overbridge structure in the electrified railway, the ITU-T regulation denotes only a theoretical estimation method, and the actual numeric values are notified differently by the official announcement of each nations. In this study, the factors which can affect the screening factor are investigated and analysed by FEM and a suitable calculation method based on multi-conductor line theory for the current pre-estimation formula for the induction noise voltage in the national notice is presented. The case studies are performed using the real data of the tunnel and the overbridge of the electrified railway, and a satisfactory formula for the determining of screening factor is derived.

• Journal of Advanced Marine Engineering and Technology
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• v.34 no.5
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• pp.718-724
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• 2010

This paper studies the differences due to the wall effect in propeller open water(POW) characteristics tested in a towing tank and in a medium size cavitation tunnel(CT). When the advanced velocity of the propeller is defined as the flow velocity measured in the plane of propeller, POW characteristics resulting from CT has a better relationship with them of towing tank. To obtain the wall effect in the propeller plane, numerical computation using the lifting panel theory is performed with and without the wall around a propeller. Then, POW results in CT are corrected based on the wall effect from numerical results. The POW results obtained from this procedure show a better agreement with the experimental results in the towing tank.