• Geomechanics and Engineering
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• v.9 no.1
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• pp.57-81
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• 2015

Water inrush and mud outburst always restricts the tunnel constructions in mountain area, which becomes a major geological barrier against the development of underground engineering. In view of the complex disaster-causing mechanism and difficult quantitative predictions of water inrush and mud outburst, several theoretical methods are adopted to realize dynamic assessment of water inrush in the progressive process of tunnel construction. Concerning both the geological condition and construction situation, eleven risk factors are quantitatively described and an assessment system is developed to evaluate the water inrush risk. In the static assessment, the weights of eight risk factors about the geological condition are determined using Analytic Hierarchy Process (AHP). Each factor is scored by experts and the synthesis scores are weighted. The risk level is ultimately determined based on the scoring outcome which is derived from the sum of products of weights and comprehensive scores. In the secondary assessment, the eight risk factors in static assessment and three factors about construction situation are quantitatively analyzed using fuzzy evaluation method. Subordinate levels and weight of factors are prepared and then used to calculate the comprehensive subordinate degree and risk level. In the dynamic assessment, the classical field of the eleven risk factors is normalized by using the extension evaluation method. From the input of the matter-element, weights of risk factors are determined and correlation analysis is carried out to determine the risk level. This system has been applied to the dynamic assessment of water inrush during construction of the Yuanliangshan tunnel of Yuhuai Railway. The assessment results are consistent with the actual excavation, which verifies the rationality and feasibility of the software. The developed system is believed capable to be back-up and applied for risk assessment of water inrush in the underground engineering construction.

• Tunnel and Underground Space
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• v.28 no.3
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• pp.247-257
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• 2018

High-speed trains have been developed widely in many countries in order to transport large quantity of people and commodities rapidly. When a high speed train enters a tunnel, aerodynamic resistance is generated suddenly. The resistance caused from air pressure induces micro pressure wave and discomfort to passengers in a train. Therefore, a pressure relief system should be installed in a tunnel to reduce the resistance acting against the running train in a tunnel. Additionally, the shape of a grain should be streamlined in order to reduce aerodynamic resistance caused by a high-speed train. The cross-section of a tunnel also should be carefully designed to reduce discomfort of passengers. This study represents the effect of pressure relief ducts installed between two running tunnels. The pressure relief duct was integrated with a cross-passage in order to save cost and construction time. One-dimensional network numerical simulations were carried out in order to estimate the effect of pressure relief systems.

• Tunnel and Underground Space
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• v.15 no.5 s.58
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• pp.359-368
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• 2005

In case the overburden of a tunnel is too low to adopt NATM, cut and cover method generally can be chosen as alternative. However, in tunneling some area with very low or no overburden between two mountains, the cut and cover method requires additional construction of a couple of tunnel portals and the maintenance of portal slopes until backfilling is completed. As a solution for this problem, increasing the tunnel overburden by raising the ground level can be effective. This paper presents the case study for tunneling at C240 site in Taiwan High Speed Railway(THSR) in which soil-cement filling method was used for pre-banking before tunnel excavation. Cement content of filling material was $2\~4\%$ and thickness of filling a round was $130\~250\;mm$. The stability evaluation for the soil-cement slope and concrete lining of low cover tunnel was conducted by numerical analysis.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.2
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• pp.153-166
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• 2015

Long subsea tunnel to be built below the seabed, as compared to the general railway tunnel, is subject to many restrictions in terms of spatial limitation when vertical or inclined shafts are built for the purpose of ventilation and fire safety. So, the construction of some artificial island is required to provide ventilation. But, because of construction difficulty and cost increase, it is necessary to minimize the artificial island construction. The longer ventilation distance is, the more fresh air requirement is needed. When supply airflow becomes excessive, duct size is restricted by the limitations of structure clearance and fan pressure and power increase exponentially. Therefore, in order to build a long subsea tunnel, it is necessary to overcome these practical problems and to develop technical solution that can keep the comfortable condition of tunnel environment during construction. In this study, as on ventilation method development suitable for long subsea tunnel, through comparison of temporary ventilation capacity calculation methods during construction phase, domestic and abroad, the application of Swiss SIA 196 code is found suitable for long subsea tunnel. And, through experiment on leakage of the duct connector, we confirmed that the leakage ratio per 100 m of domestic duct connection type is between 1.5~3.0%. Based on S-class duct of SIA 196 code, ventilation distance is 10.2 km, So, ventilation distance can be longer if duct connection method is improved. So, we confirmed that the improvement of leakage ratio is key issue in the construction-phase ventilation of long subsea tunnel.

• Tunnel and Underground Space
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• v.25 no.6
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• pp.487-495
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• 2015

The specification for selecting railway ballast in France is introduced in this study and the effectiveness of selection for railway ballast is studied for the case of a quarry located in northen France. The quality of railway ballast is, in general, estimated depending on the grain distribution and mainly of the resistance against abrasion. The resistance against abrasion is obtained by both Los Angeles abrasion test and Micro Deval test, which determine the ballast quality suitable whether for high speed railway or classical railway. This study analyzed the correlation between the abrasion index obtained from the abrasion tests for the aggregates sampled at three different stages among ballast production procedure at the quarry. A high correlation is determined between Los Angeles Abrasion index (LA) and Micro Deval index (MDA) and also between abrasion indices of different aggregates. Particularly, this correlation between the abrasion indices allows to estimate the quality of ballast at the final stage from the aggregates at the site in a quarry within the margin of error.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.319-332
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• 2015

The pressure wave formed by the piston effects of the train proceeds within the tunnel when a train enters the tunnel with a high speed. Depending on the condition of tunnel exit, the compression waves reflect at a open end, change to the expansion waves, transfer to tunnel entrance back. Due to interference in the pressure waves and running train, passengers experience severe pressure fluctuations. And these pressure waves result in energy loss, noise, vibration, as well as in the passengers' ears. In this study, we performed comparison between numerical analysis and field experiments about the characteristics of the pressure waves transport in tunnel that appears when the train enter a tunnel and the variation of pressure penetrating into the train staterooms according to blockage ratio of train. In addition, a comparative study was carried out with the ThermoTun program to examine the applicability of the compressible 1-D model(based on the Method of Characteristics). Furthermore examination for the adequacy of the governing equations analysis based on compressible 1-D numerical model by Baron was examined.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.1
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• pp.59-76
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• 2020

As a continuous increase in demand for the transportation infrastructure in the metropolitan area, the renovation of existing metropolitan and urban railway lines for the rapid transport system requires the construction of sidetrack that can operate local and express trains simultaneously. However, the construction of sidetrack after stopping the operation of the existing subway line causes a lot of economic losses, therefore it is essential to study the tunnel enlargement scheme during the operation of the existing subway tunnel. Accordingly, in this paper, basic research on the enlargement plan of the existing subway tunnel was carried out for the renovation of the existing subway line. In order to investigate the method for the sidetrack construction, the Government Complex Gwacheon station on the Gwacheon line of subway line 4 was selected as a virtual research station. Subsequently, four construction plans including tunnel cross-sectional plan for each section were reviewed and constructability and economic feasibility were compared. Finally, the stability assessment was conducted for the selected construction plan which was considered to be relatively unstable by 3-D full numerical analysis considering the sidetrack construction process.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.5
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• pp.339-357
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• 2021

As the construction of trans infrastructure using the underground tunnel have been rapidly increased, various nearby excavation of existed underground facility including subway structure has been occurred in urban tunnelling. The concern and worry relating to the safety and stability of the existed facility by nearby excavation is becoming the key issues in urban tunnelling. In this study, it was conducted for existed the subway station structure at Seoul subway line which was closely located in the new Dongbuk urban metro railway to determine the behavior characteristics of station structure according to adjacent tunnel construction. Also, it was reviewed the evaluation of the safety zone and excavation method for subway structure. And after a review of damage evaluation, track irregularities and structural calculation by using a numerical analysis, stability of the subway structure according to nearby tunnel excavation was evaluated to be secured. This study is expected to be applied as useful reference in advance if you need to review the effects of existed structure according to nearby construction in complex urban tunnelling.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.4
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• pp.397-404
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• 2008

Excessive amount of groundwater flowed into tunnel, while constructing Incheon international airport railway. Tunnel passes under subway line no. 2 with only 1.76 m below. To protect the existing structure, TRcM excavation method was applied. As station and construction shaft are already constructed, which are located back and forth of TRcM section, 86.4 ton per day of groundwater inflow is against expectation. To identify mechanism of excessive water inflow, hydraulic back analyses were performed. Then, hydro-mechanical coupled analysis were also performed with the hydrogeologic parameters identified, whose results are investigated for checking the stability of adjacent structures to the tunnel under construction. And a number of mechanical analyses were also performed to check the hydro-mechanical coupling effect. The result from the mechanical analysis shows that subsidence and tunnel ceiling displacement will be 0.85 mm and 1.32 mm. The result of hydro-mechanical couple analysis shows that subsidence and maximum tunnel ceiling displacement will be 1.2 mm and 1.72 mm. Additional displacements caused by groundwater draw down were identified, however, displacement is minute.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.249-256
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• 2015

Quantitative Mokpo-Jeju undersea tunnel is currently on the basis plan for reviewing validation. As for the cross section shape for express boat of 105 km line, sing track two tube is being reviewed as the Euro tunnel equipped with service tunnel. Also, 10 carriage trains have been planned to operate 76 times for one way a day. So, in this study, quantitative risk assessment method is settled, which is intended to review the optimal space between evacuation connection hall of tunnel by quantitative risk analysis method. In addition to this, optimal evacuation connection hall space is calculated by the types of cross section, which are Type 3 (double track single tube), Type 1 (sing track two tube), and Type 2 (separating double track on tube with partition). As a result, cross section of Type 2 is most efficient for securing evacuation safety, and the evacuation connection space is required for 350 m in Type 1, 400 m in Type 2, and 1,500 m in Type3 to satisfy current domestic social risk assessment standard.