• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.2
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• pp.161-169
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• 2004

In this study, a similarity rule is thoroughly discussed for tunnelling model tests which can simulate actual ground conditions. Based on this prior consideration, theoretical works are performed to simulate a real ground condition into a gravitational field with a similarity. A process is arranged to determine a lining condition in laboratory tests for a sandy ground tunnel.

• 한국터널공학회:학술대회논문집
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• 2005.04a
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• pp.282-291
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• 2005

사암 및 이암을 기반암으로 하는 산악지역에 건설되는 2-아치 (2-arch) 터널의 거동을 터널설계 단계에서 분석하기 위하여 대규모 실내 모형실험을 실시하였다. 터널이 시공될 예정인 지반과 유사한 지질공학적 특성을 가지는 콘크리트 블록을 이용하여 모형지반을 조성하였다. 모형실험은 중앙터널 (pilot tunnel) 굴착을 포함한 여러 단계의 굴착과정으로 구분하여 실시되었다. 또한 터널 .공용기간 중 터널의 거동을 연구하기 위하여 터널굴착 완료 후 상재하중을 작용시켰다. 실험결과에 의하면 대부분의 지반변위는 중앙터널 굴착에 의해 발생했으며, 그 이후 터널 굴착단계에서의 변위발생은 미미한 것으로 나타났다. 또한 대부분의 지중변위는 0.25D 이내의 범위에서 발생하였다. 여기서 D 는 터널의 폭이다. 한편 실험결과를 분석하여 경암에 시공되는 2-아치 터널의 중앙벽체(centre pillar)에 작용하는 하중에 대한 경험적인 공식을 제시하였다. 터널시공 완료 후 공용기간 중 상재하중이 작용할 경우 그 크기에 따라서는 터널굴착에 의해 발생한 것보다 더 큰 지중변위가 발생할 수 있는 것으로 분석되었다. 터널의 거동은 중앙벽체의 강성에 큰 영향을 받는 것으로 나타나 이를 터널설계에 반영하여 중앙벽체의 강성을 증가시켰다. 현재 터널시공을 위한 사전작업이 진행 중에 있으며, 터널의 굴착은 2005년 하반기에 실시될 예정이다.

• Tunnel and Underground Space
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• v.14 no.5
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• pp.381-390
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• 2004

In this study, scaled model tests were performed to investigate the deformation behaviors around twin tunnels. Eleven types of test models which had respectively different pillar widths, rock types and loading conditions were mode, where the modelling materials were the mixture of sand, plaster and water. The models with shallower pillar width were cracked under lower pressure than the models with thicker pillar width, and they showed the more tunnel convergences and the clear spatting failures. The models of hard rock were cracked under 50% higher pressure than the models of soft rock and they showed the less tunnel convergences. The failure and deformation behaviors of twin tunnels were also dependent on the loading conditions of models. Futhermore, the results of FLAC analysis were qualitatively coincident with the test results.

• Tunnel and Underground Space
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• v.18 no.4
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• pp.300-311
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• 2008

In this study, scaled model tests were performed to investigate the stability of three parallel tunnels. Seven types of test models which had respectively different pillar widths, tunnel sectional shapes, support conditions and ground conditions were experimented, where crack initiating pressures and deformation behaviors around tunnels were investigated. In order to evaluate the effect of pillar widths on stability, various models were experimented. As results, the models with shallower pillar widths proved to be unstable because of lower crack initiating pressures and more tunnel convergences than the models with thicker pillar widths. In order to find the effect of tunnel sectional shape on stability, the models with arched, semi-arched and rectangular tunnels were experimented. Among them rectangular tunnel model was the most unstable, where the arched tunnel model with small radius of roof curvature was more stable than semi-arched one. The model with rockbolt showed higher crack initiating pressure and less roof lowering than the unsupported model. The deformation behaviors of tunnels in the anisotropic ground model were quite different from those in the isotropic ground model. Futhermore, the results of FLAC analysis were qualitatively coincident with the experimental results.

• Tunnel and Underground Space
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• v.22 no.3
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• pp.205-213
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• 2012

In this study, scaled model tests were performed to investigate the stability of twin tunnels constructed in anisotropic rocks with $30^{\circ}$ inclined bedding planes under the condition of lateral pressure ratio, 2. Five types of test models which had respectively different pillar widths and shapes of tunnel sections were experimented, where both crack initiating pressures and deformation behaviors around tunnels were investigated. The models with shallower pillar width showed shear failure of pillar according to the existing bedding planes and they were cracked under lower pressure than the models with thicker pillar width. In order to find the effect of tunnel sectional shape on stability, the models with four centered arch section, circular section and semi-circular arch section were experimented. As results of the comparison of the crack initiating pressures and the deformation behaviors around tunnels, the semi-circular arched tunnel model was the most unstable whereas the circular tunnel model was the most stable among them. Furthermore, the results of FLAC analysis were qualitatively coincident with the experimental results.

• Journal of the Korean GEO-environmental Society
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• v.14 no.12
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• pp.61-69
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• 2013

As construction for road and train tunnel is increasing, various geotechnical conditions can be faced during the construction stage. Especially, if the tunnel is located in limestone area, the cavity is mostly to locate in tunnel planning location. One or some cavities which can be harmful for tunnel safety are predicted. Hence, this study was fulfilled to confirm the influence between tunnel and cavity using laboratory scale down model test and numerical analysis. The scale down model test was carried out to confirm the failure load of the model ground about the interval length of cavity and tunnel and to analyze behaviour characteristics of the model ground on the cavity shape. From the model test result, the failure load decrease in accordance with decreasing of interval length between cavity and tunnel within 0.5D. The numerical analyses were carried out for verification about scale down model test. From the numerical analysis result, tunnel safety decreases in the case of the interval between cavity and tunnel within 0.5D.

• Tunnel and Underground Space
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• v.15 no.6 s.59
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• pp.400-410
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• 2005

During excavation of shallow tunnels in soft ground, failure mechanism around the tunnel face have major influence on the stability of tunnels. In this paper, a series of laboratory tests under plane strain condition on the small scale of a shallow tunnel considering unsupported tunnel length has been performed. The results have shown that tunnel failure mechanism changes from failure mode 1 to failure mode 2 as unsupported tunnel length increases. By comparing the experimental and the numerical results, the loosening pressure for the shallow tunnel and progressive failure have been investigated.

• Tunnel and Underground Space
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• v.22 no.1
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• pp.22-31
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• 2012

In this study, scaled model tests were performed to investigate the stability of an asymmetrical twin tunnels constructed in rock mass comprising alternating layers of sandstone and shale. Each of tunnels had a differently shaped section, where the one was already constructed tunnel including lining structure but the other was planned to be under construction. Four types of test models which had respectively different pillar widths and loading conditions were experimented, where both crack initiating pressures and deformation behaviors around tunnels were investigated. The cracks of pillar mainly began to appear at the interfaces of alternating layers, following additional shear displacement between layers was confirmed as one of the most important factors of pillar failure in case of the model of pillar width 0.5D. The models with shallower pillar widths proved to be unstable because of lower crack initiating pressures and more tunnel convergences than the models with thicker pillar widths. The failure and deformation behaviors of tunnels were also dependent on the loading conditions, where the model of coefficient of lateral pressure 1.0 was more stable than the other model. Futhermore, the results of FLAC analysis were qualitatively coincident with the experimental results.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2008.10a
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• pp.365-376
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• 2008

본 논문은 1차로 마제형 터널에서의 지반과 지보재의 상호 거동을 규명하기 위한 연구로서 터널의 주지보재인 숏크리트의 균열, 파괴하중 및 변형하는 거동양상을 실물크기의 터널모형실험을 통해 확인하였다. 이때 실험은 측압계수를 0.5, 1.0, 2.0으로 설정하여 각각 측압계수에 따른 결과를 확인하였다. 또한 실제 실험과 같은 조건을 설정한3차원 수치해석을 실시하여 각각의 결과를 비교 검증하였다. 터널모형 실험은 측압조건을 설정할 수 있도록 11개의 실린더를 사용하여 실험을 수행하였다. 3차원 수치해석 모델링은 터널모형실험과 가능하면 같은 조건으로 해석하기 위하여 모형실험으로부터 로드셀 및 LVDT를 통해 얻은 하중-변위곡선이 수치해석 시에도 재현되도록 하였다.

• Journal of Korean Tunnelling and Underground Space Association
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• v.7 no.1
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• pp.3-12
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• 2005

The behaviors of the ground in crossed zone and the existing upper tunnel in shallow cover due to the excavation of new lower tunnel Rectangularly crossed to that was studied. Model tests were performed in the large scale test pit, the size was '$4.0m(width){\times}3.8m(height){\times}4.1m(length)$'. Test ground was constructed uniformly by sand in middle density. Results of the model tests show that earth pressure and settlement of the ground in crossed zone were redistributed due to the longitudinal arching effect by the excavation of lower tunnel. Upper tunnel blocks stress flow due to the longitudinal arching effect by excavation of lower tunnel.