• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.3
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• pp.275-286
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• 2007

In construction of a structure in underground space, in-situ stress in rock mass has great effect on the stability of the structure. Especially, the direction and magnitude of rock stress have influence on the excavation method, the choice of support and reinforcement method for establishing the stability of tunnel. Therefore, it is very important to consider the characteristics of in-situ stress in rock mass for tunnel stability analysis. In this study, a reasonable design method for underground structure was reviewed through the case study for tunnel design considering in-situ rock stress. For this purpose, the estimation for SRF (Stress Reduction Factor) as input parameter in rock classification using Q-System and the assesment for tunnel support were studied. Also, considering the characteristics of in-situ rock stress such as the magnitude of K and the direction of principal stress, the parameter studies for tunnel stability analysis were carried out. An improved method was proposed for obtaining the better results in the tunnel stability analysis.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.4
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• pp.397-419
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• 2012

The pressurizing support tunneling method has been developed that overcomes shortcomings of conventional trenchless methods and applied to the field. The main concept of the new method is the pressurization system which, by means of pressurization bag between outer flange of steel ribs and excavated perimeter, applies higher pressure than the pressure relaxed by excavation to the ground to prevent ground displacement. The stability of the support members and effect of displacement control of the new method were verified through 3D numerical analyses. The new method was applied to the construction of a 10.7 m wide, 7.9 m high and 85 m long ramp tunnel that passes under ${\bigcirc}{\bigcirc}$ Expressway. By applying the new method, the tunnel construction was successfully completed in 13.5 months which decreases construction time to 35% compared to conventional methods, and ground displacement was almost negligible.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.6
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• pp.124-131
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• 2010

Rock Bolt generally utilizes deformed reinforcing bar welded from structural steel of which strength is higher than required for making advantageous use of the support function of ground. In the condition with highly corrosive underground water, however, problem frequently occurs on tunnel and slope stabilization in terms of repair, rehabilitation and maintenance issues due to the destruction of Rock Bolt by corrosion of steel. A structural performance evaluation for GFRP Rock Bolt was conducted for the purpose of resolving the foregoing problem and at the same time developing a permanently-usable support material. This study intended to evaluate the safety factor of GFRP Rock Bolt by implementing the slope stability interpretation via structural analysis on the basis of its structural characteristics derived from both tensile force function test and shear force function test. It is judged based on the results that GFRP Rock Bolt would secure sufficient ground stability as an alternative material for existing Steel Rock Bolt.

• Tunnel and Underground Space
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• v.8 no.4
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• pp.261-274
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• 1998

The brief results of laboratory and field tests of yieldable steel arches are represented. The test supports were fabricated with three U-sectional beams which are 25.8 kg/m of Glocken profile. The structural analyses of semi-circular and arch supports were conducted to find out shape factor of U beam to be 1.35 and the location of 2nd plastic hinges. Load capacity of arch supports under crown loading were examined as a function of leg length. Yieldable characheristics of test supports were investigated with various bolting torque of connection part. Determination method of bolting torque were also studied. Finally, test supports were installed in-situ with torque of 21 kg .m, which showed a typical yielding procedure.

• Tunnel and Underground Space
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• v.14 no.5
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• pp.345-352
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• 2004

In a shotcrete support system, the cooperation of the ground and the shotcrete lining makes it possible to transfer the shear stress to the shotcrete lining, which is dedicated to form a stable structure. In this study, a homogeneous model ground with constant strength was produced by using gypsum and the tunnel was excavated with a top heading method under the definite initial stress. During the excavation, the stress in the ground around the tunnel and the deformation of shotcrete lining were measured, The tensile stress was generated in tangential direction in the ground near the tunnel and in the shotcrete lining due to tunnel excavation. This shows the unified behavior of the ground and shotcrete lining, which is the most typical characteristic of the shotcrete support. As a result, the rates of in-situ stress during the excavation at a top boundary line was 9% and at top arch heading 15%. It was 48% right after excavating the heading and 94% before cutting the bench.

• Journal of Korean Tunnelling and Underground Space Association
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• v.16 no.5
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• pp.487-495
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• 2014

In this study, in order to suggest the design method for supports in the room-and-pillar underground structure, the case study was carried out. In the case study, shape of rock pillar and room was mainly considered. From the analysis, a displacement at the roof, the maximum principle stress and plastic state were examined. To optimize variables in the case study, cases from the Seoul metro station were analyzed, then a target depth of the underground structure and ground conditions were determined. And the height of rock pillar and room were chosen from the assumed purpose of underground space, i.e. living/office and warehouse. Total cases of analysis was 180 cases including 3 types of ground condition, 5 types of rock pillar and 6 types of roof span. It is expected that results from analysis can be used to determine the installation of support in room-and-pillar underground structure with stability, utilization efficiency of underground space and applicability of vehicles.

• Tunnel and Underground Space
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• v.11 no.2
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• pp.96-108
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• 2001

A concrete lining of NATM tunnel is the final product of a process that involves planning and evaluation of user needs, geotechnical investigations, analysis of ground-lining interaction, construction, and observations and modifications during construction. The designer must consider the lining in context of the many function, construction, and geotechnical requirements. Also, the loss of supporting capacity of shotcrete lining due to poor rock qualities and shotcrete erosion must be considered. The values, shapes, and estimating methods of rock load and water pressure are very different with every designers. Estimating methods of rock loads used in the design of NATM tunnel concrete lining are investigated. Structural analyses are done in various load combinations, and the member forces(moment, axial force and shear force) are compared. The adequate load combination of rock load and water pressure is proposed.

• Computational Structural Engineering
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• v.2 no.4
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• pp.27-29
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• 1989

터널의 굴삭과 지보방법에 대한 개념을 도입한 NATM(New Austrian Tunnelling Method)이 등장한 이후, 이 신공법에 대한 연구와 그 응용작업이 급속히 수행되어 왔으며, 현재는 세계각국에서 이 공법을 널리 사용하고 있는 실정이다. 우리나라에서도 1982년 서울 지하철 건설공사에서 본격적으로 사용하여, 현재는 터널 설계에 있어서 일반적 설계방향으로 정착되어 가고 있다. 이런 추세에 따라, 본 Program이 개발되었으며, 그에 관계된 내용을 이글에서 소개코자 한다.

• Tunnel and Underground Space
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• v.16 no.3 s.62
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• pp.218-231
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• 2006

Anisotropic/heterogeneous rock mass shows various deformation behavior types due to tunnelling because deformation behavior is largely controlled by the spacial characteristics of geological factors such as faults, joints and fractured zone in rock mass. In this paper 2-dimensional numerical analysis on the several influencing factors is performed considering fractured zone located near tunnel. This numerical analysis shows that deformation behavior of tunnel are very different according to the width and the location of fractured zone and supper method. However, 3-dimensional analysis is necessary to consider 3-dimensional geometrical characteristics sufficiently since discontinuity and fractured zone have 3-dimensional geometry. Also flexible design/construction guidelines for tunnelling are required to cope with uncertain ground condition and circumstance for technically safe and economic tunnel construction.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2002.10a
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• pp.31-42
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• 2002

최근 지하철 터널은 사용자 편의성, 도심지 접근성 및 원활한 교통처리 등을 고려하여 지반조건이 불리한 상황에서도 터널로 계획되는 경우가 많아지고 있다 따라서 시공중의 터널안정성확보, 굴착에 따른 인접구조물의 침하영향, 발파진동영향 등을 종합적으로 고려한 지보패턴 및 보조·보강공법의 결정이 매우 중요하나 정량적인 판단기준의 부재로 인하여 주로 경험적인 설계에 의존하는 경우가 많다. 본 연구에서는 도심지 지하철 터널의 복합적인 거동특성을 고려하기 위하여 여러 가지 예상위험요소의 정량화 방안을 제안하고, 다변량 통계분석기법을 활용하여 여러 가지 위험 요소들의 특성을 함축적으로 나타내는 소수의 총합적인 지표(안정성인자, 환경성인자)로 대표화 할 수 있음을 검증하였다. 안정성 인자 및 환경성 인자를 이용한 서울시 지하철 00공구 설계사례를 통해 정량화지표(Multiple Index)의 터널설계에의 적용성을 평가하고 이의 설계시 활용방안을 제안하고자 하였다.