• Magazine of korean Tunnelling and Underground Space Association
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• v.21 no.2
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• pp.25-40
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• 2019

• Korean Journal of Construction Engineering and Management
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• v.20 no.2
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• pp.37-43
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• 2019

After the new standards for labor hours has been released, various problems come up in construction field, such as income reduction of employees, extension of construction period and increased construction cost. Although it is expected that the impact of the new standard on the construction industry is more worse than other industries form the view of productivity, not much works have been done to identify those impacts. Thus, this research proposes the standard construction processes, excavation cycle, and unit construction period for NATM tunnel project based on 'Construction Standard Production Rates.'The study also investigated the impact of reduced labor hours on the management of work crews, construction periods and costs of tunnel projects. The results showed that under the 52 labor hour standard, the construction periods for the excavation work and whole project was increased by 20% and 8.9%, respectively, but the construction costs for the excavation work and whole project was decreased by 1.4% and 0.6%, respectively.

• Magazine of korean Tunnelling and Underground Space Association
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• v.21 no.4
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• pp.11-33
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• 2019

• Magazine of korean Tunnelling and Underground Space Association
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• v.20 no.1
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• pp.35-47
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• 2018

• Magazine of korean Tunnelling and Underground Space Association
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• v.21 no.2
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• pp.10-24
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• 2019

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.1
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• pp.137-153
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• 2019

Estimating tunnel construction time and costs are the most fundamental part of a tunnel project planning, which has been generally assessed on a deterministic basis until now. In this paper, excavation cycle time was investigated for two road tunnels and one subway tunnel, and the results were compared with the Standard of Construction Estimate (SE), which is made for the estimation of construction time and cost in a design stage. The results show that the difference in cycle time between SE and actual cycle time is 50%, 7% and 31% respectively for the three tunnels, which means that SE does not reflect practical operation time. The major reasons of the difference are skilled level of tunneling workers, the change of operation sequences for more effective operations, much more complicated working atmosphere in a tunnel than the assumption of SE etc. Finally, even though the results can not be generalized since investigated tunnels are only 3, but it is thought that SE needs to be upgraded into the model able to consider quite common situations through additional tunnel investigation and studies in the future.

• Tunnel and Underground Space
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• v.9 no.1
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• pp.20-26
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• 1999

The completion of the Bakun Diversion Tunnel is subsequently to the Main Dam construction. Therefore, the completion date is very important for the Bakun Hydroelectric Project. Generally, the tunnel lining work as a finishing phase of the tunnelling project occupies a important portion as well as an excavation and a support work of the tunnels in respect to the construction cost and period. Internal section of Bakun Diversion Tunnel is designed circular shape to reduce the roughness of the water flow with 12 meters in diameter of total length 4314.6 meters of 3 tunnels. The lining thickness is varied between 500 mm and 700 mm depending on the structural condition. From the original Tender design of the Bakun tunnels, the required quantity of steel bars was 5,985 ton designed by Reinforced Concrete (RC) through the entire tunnel linings. During the detail design stage by the consideration of the rock conditions and various load conditions, we could suggest five kinds of RC lining type including plain concrete lining type. Through the detail design modification, we could reduce the required amount of steel bars to 2,178 ton, as a half of original Bill of Quantity. Finally, this design modification give us the time and cost saving effect to catch up the construction progress in time.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.1
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• pp.37-45
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• 2021

The construction of the tunnel portal should be careful because cover depth is shallow and it is difficult to exhibit the arching effect. Tunnel stability may be reduced with additional embankment above the portal of tunnel. In this study, in order to examine the stability of the tunnel according to additional embankment above the portal of tunnel, numerical analysis was performed while changing the ground conditions and height of embankment. As a result of the numerical analysis, it was found that the allowable flexural compressive stress of shotcrete and allowable axial force of rockbolts were exceeded when the height of additional embankment was 12 m in rock mass rating V. When considering the displacement, the range of the plastic region and the behavior of the support materials, the tunnel stability seems to be greatly reduced if the height of additional embankment above the portal of tunnel exceeds 10 m.

• Journal of the Korean GEO-environmental Society
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• v.15 no.10
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• pp.23-28
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• 2014

Recent increasing of redevelopment project causes construction of new buildings after demolition of old buildings. However, the researches have been largely confirmed to analysis of behaviour characteristics of existing subway tunnel due to adjacent excavation which constructing new building so far. Accordingly, The ${\bigcirc}{\bigcirc}$ Building which will be built after demolishing existing parking lot is selected as a subject of study. And the purpose of this study is to analyze the effects on existing subway tunnel due to loading and unloading caused by demolition of upper buildings. The numerical analysis was performed by using the MIDAS/GTS program. Two cases for the numerical analysis were analyzed. The one is considering demolition of old buildings and the other is not considering it. This study is to analyze the effect on existing subway tunnel caused by demolition of upper building by analyzing numerical analysis results for tunnel displacement and lining stress. It was analyzed that the effects of considering the demolition of old buildings are larger than those of no considering it.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.5
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• pp.463-476
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• 2024

The shield TBM method can eliminate environmental hazards such as noise and vibration, and is environmentally friendly and allows safe tunnel construction even in soft ground conditions, but there are many restrictions on its application due to its high construction costs compared to the NATM. Therefore, in order to increase the applicability of the shield TBM method, it is necessary to ensure economic efficiency by reducing construction costs, and it is very important to reduce segment construction costs, which account for the largest proportion of shield TBM tunnel construction costs at about 35 to 40%. As part of this, this paper considers the changes in segment stress during tunnel construction and operation, tunnel external load conditions, etc. through analysis of long-term measurement data of shield TBMs in Japan, which has abundant experience in shield TBM construction, and compares and analyzes the differences between predicted values at the design stage and measured values during operation. Through this, we study improvements to ensure segment economic efficiency at the shield TBM design stage.