• 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.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 1994.03a
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• pp.1-11
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• 1994

현재 국내 터널의 설계와 시공은 대부분 NATM의 원리를 적용하고 있다. 그러나 터널의 설계 접근방법과 시공의 상황을 살펴보면 NATM을 국내 지질에 적용하는 것이 항상 최적이 아니라는 것을 알수 있으며, 국내 터널의 시공에 있어서도 NATM과 다른 개념의 도입과 정확한 이해가 필요하다는 것을 많은 기술자가 느끼고 있다. 따라서 보다 경제적이고 안전한 터널 시공방법의 결정을 위해 NATM의 개념과 다른 터널 설계 및 시공방법으로 노르웨이 터널 시공법(Norwegian Method of Tunnelling, NMT)을 소개하고자 한다. (중략)

• 한국지구물리탐사학회:학술대회논문집
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• 2005.09a
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• pp.37-42
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• 2005

Remote seismic tomography is regarded as one of the most valuable geophysical technique for the estimation of the rock mass classification in the tunnel area where hard data information such as drill logs are absent. But the results of rock mass classification based on the remote seismic tomography tend to be overestimated in practice. In this study, we propose the effective method to implement the seismic reference velocity ratio based on semblance for the improvement of rock mass classification. Also, to verify its feasibility, proposed technique was tested by using the real field data.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.2
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• pp.141-150
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• 2009

When constructing a subsea tunnel in discontinuous rock mass, fluid flow in joints has a great influence on the behavior of the tunnel so that hydro-mechanical coupled analysis should be performed for the stability estimation. In practice, relaxed rock load is generally used for the design of tunnel concrete lining. In a continuum analysis, a method based on the distribution of local safety factor around a tunnel was proposed for the estimation of a potential relaxed zone. However, in the case of discontinuous rock mass in which joints are developed, the whole stability of tunnels depends on the behavior of the joints. In this study, therefore, a method is proposed for the estimation of a potential relaxed zone occurred by the excavation of a tunnel in discontinuous rock mass. The suggested method is validated by sensitivity analysis and the comparison with the results of continuum analysis.

• Tunnel and Underground Space
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• v.17 no.1 s.66
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• pp.1-8
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• 2007

In Norway, about 30 subsea tunnels have been constructed over the last 20 years. The minimum depth of 17 subsea tunnels is 56 m and rock cover are between 23 and 49 m. As the project areas for subsea tunnel are covered by water, special investigation techniques need to be applied and the investigation results are more uncertain than that of most conventional tunnel projects. The indefinite potential of water inflow and the salinic character of ingress water represent considerable problems for tunnel equipment and rock support materials. The least stable conditions are represented by major faults or weakness zones containing heavily crushed rock and clay gouge. This paper introduces the Oslofjord subsea tunnel project including minimum rock cover requirement, risk of water inflow, investigation costs, construction costs, and traffic & operation costs.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.10a
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• pp.247-267
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• 2005

이암층 역암층 그리고 화산암층과 같은 특수지질 불량구간에서 터널과 암반사면의 합리적인 시공을 달성하기 위해서는 먼저 대상지질에 대한 지질조건과 암반특성을 정확히 이해하는 것이 필요하며, 이를 바탕으로 지반특성에 적합한 보강대책을 수립하도록 하여야 한다. 본 고에서는 포항지역과 경주지역에서의 미고결 이암 및 역암층 그리고 제주도 화산암층에서의 암반 구조물에 대한 설계 및 시공사례를 검토하고 전형적인 미고결 지층으로 알려진 신생대 지층에서의 터널과 암반과 같은 암반구조물에 대한 설계 및 시공상의 제반 문제점을 고찰하므로서 이에 대한 합리적인 대책을 수립하고자 하였다.

• Journal of the Korean Geotechnical Society
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• v.16 no.5
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• pp.63-74
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• 2000

지하구조물 걸설시 발파에 의한 암반의 굴착공법이 일반적으로 사용된다. 그러나 발파에 의한 암반의 굴착은 잔존암반의 손상과 진동을 유발하는 문제점을 가지고 있다. 현재까지는 이러한 암반의 손상과 진동문제를 해결하기 위해 현장계측을 기초로한 경험적인 방법이 이용되어 왔으나 여러 가지 한계점을 지니고 있는 것이 현실이다. 따라서 수치해석에 의한 터널 발파의 모델링을 이용하면 이러한 한계점을 보완할수 있을 것이다. 본 논문에서는 발파에 의한 발파공 주위 암반의 거동을 유한요소해석을 이용하여 규명하고, 토로터널의 표준발파패턴을 기초로 하여 외과공 발파와 외곽공에 인접한 주변공 발파에 의한 암방의 손상의 손상을 비교하여 발파패턴의 적절성을 평가하고자 하였으며, 이를 근거응 발파에 의한 암반의 손상을 최소하기 위한 발파패턴의 최적화를 도모하였다.

• Journal of the Korea Construction Safety Engineering Association
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• s.45
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• pp.60-70
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• 2008

Mechanized tunnelling by TBMs has been extensively adopted for last two decades. Nevertheless, only few case histories have been reported. Unlike NATM tunnels, the case histories of the weak zone have been seldom reported for the mechanized tunnelling, even in the other countries. In this study, a collapse of TBM tunnel occurred in the severely altered weak rock zones between volcaniclastic rocks and granitic rocks was briefly described. A systematic geotechnical investigation, which was performed to examine the cause of the collapse, was carried out at the site and then characteristics of the rocks in the zones were evaluated. Moreover, This study propose a guide line of estimateing the possibility of collapse in TBM tunnels through comparing experimental results with surveying results of general rocks.

• Tunnel and Underground Space
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• v.16 no.6 s.65
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• pp.495-505
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• 2006

Calculating the distribution of stresses and displacements around a circular tunnel excavated in infinite isotropic rock mass subjected to hydrostatic stress condition is one of the basic problems in rock engineering. While closed-form solutions for the distribution are known if rock masses are considered as elastic, perfectly plastic, or brittle-plastic media, a few numerically approximated solutions based on various simplifying assumptions have been reported for strain-softening rock mass. In this study, a simple numerical method is introduced for the analysis of strain-softening behavior of the circular tunnel in Mohr-Coulomb rock mass. The method can also applied to the analysis of the tunnel in brittle-plastic or perfectly plastic media. For the brittle-plastic case where closed-formsolution exists, the performance of the present method is verified by showing an excellent agreement between two solutions. In order to demonstrate the strain-softening behaviors predicted by the proposed method. a parameter study for a softening index is given and the construction of ground reaction curves is carried out. The importance of defining the characteristics of dilation in plastic analysis is discussed through analyzing the displacements near the surface of tunnel.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.1
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• pp.91-97
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• 2007

Loads on the pillar and ground deformation in 2-arch tunnel, which is excavated in the rock mass with regular discontinuities, depending on the dips of discontinuities and the construction sequences were experimentally studied. Large scale model tests in the biaxial test facility were performed. Tested model (width 3.3m, height 3.0m, and length 0.45m) for 2-arch tunnel in 1/10 scale were built with various dips. Test results show that discontinuities have greate affects on the behavior of the 2-arch tunnel, especially on the pillar loads and ground deformation.