• Journal of Korean Tunnelling and Underground Space Association
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• v.13 no.3
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• pp.199-214
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• 2011

A crack is the main cause to affect the integrity of tunnel lining as well as leakage, spalling, exposed rebar, corrosion, carbonation and so on. Since the 1980, NATM has prevailed on excavation method and geotechnical philosophy in tunnel. Although the pattern of cracks has been reported by several engineers' effort, it was only focused on longitudinal cracks of lining. Eleven operational NATM tunnels have been conducted with the precise inspection for safety and diagnosis by KISTEC (Korea Infrastructure Safety and Technology Incorporation). With those results, the crack patterns by the spatial distribution and appearance for each tunnel have been analyzed and the cause of occurrence for seven common types of cracks in NATM tunnels was classified. Additionally, the longitudinal crack on lining above duct slab was figured out by numerical simulation and field inspection. Each crack has been analyzed by CCD (Charge-Coupled Device) scanner image with 3D configuration. Each type of cracks is also explained with output of experimental and condition of construction. Defined cracks on NATM tunnels will be good example for periodical inspection and precise inspection for safety and diagnosis.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.2
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• pp.155-170
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• 2020

In this paper, a risk management system applicable to NATM tunneling projects is proposed. After investigating case histories in NATM tunnel collapse, this paper analyzes the potential risk factors and their corresponding risk events during NATM tunnel construction. The risk factors are categorized into three groups: geological, design and construction risk factors. The risk events are also categorized into four types: excessive deformation, excessive deformation with subsidence, collapse inside tunnels, and collapse inside tunnels with subsidence. The paper identifies risk scenarios in consideration of the risk factors and proposes a risk analysis/evaluation method for the NATM tunnel risk scenarios. Based on the evaluation results, the optimal mitigation measure to handle the risk events is suggested. In order to effectively facilitate a series of risk management processes, it is necessary to develop a risk register and a management ledger for risk mitigation measures that are customized to NATM tunnels. Lastly, the risk management for an actual NATM tunnel construction site is performed to verify the validity of the proposed system.

• 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)

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.4
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• pp.437-447
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• 2009

It is easily found by several references of NATM that the cracks on the lining concrete of NATM are more developed than those of the conventional tunnel methods. Based on the results of research, the new method is proposed to control and protect the axial cracks on the tunnel linings. Also, the efficiency of proposed method is evaluated using the Distinct Element Method.

• 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.

• Tunnel and Underground Space
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• v.20 no.2
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• pp.73-81
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• 2010

The paper presents the application of FE simulations of NATM tunnel using different constitutive models. The results from a series of two dimensional plane strain finite element analyses of medium-liner interaction for NATM are presented. Four types of constitutive models are considered, namely, linear elastic, elasto-plastic Mohr-Coulomb, Hardening-Soil, Soft-Soil model. The design for tunnels requires a proper estimate of surface settlement and lining forces. It is shown that the advanced constitutive model gives better predictions for both ground movement and structural forces.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.5
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• pp.717-733
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• 2019

In this study, lining thickness distribution and its behind state (particularly, its void state) were analyzed using the GPR survey data performed on three currently operating NATM tunnels. Results of GPR analysis showed that void areas were mostly detected between concrete lining and primary support, particularly, near the crown of the tunnels. The lining thickness in the left-hand side of the tunnel was different from that of the right-hand side by 8.6~253.5 mm when measured in transverse direction. It was also found that longitudinal cracks were prevailed in the area lining thickness was sharply changed. Longitudinal thickness distribution at the crown was also studied and tested by performing 3 goodness-of-fit tests in order to find the most suitable thickness distribution. Normal distribution (or similar distribution) fit most suitably to the measured data if the measured average thickness was larger than designed one; Gamma and/or Inverse Gauss distribution fit to the measured data reasonably well if the measured average thickness was less than the designed value of thickness. Since actual lining thickness can be a potential index when assessing the state and safety of the unreinforced NATM tunnel lining, measuring of the lining thickness with GPR survey might be needed rather than assuming the thickness is always constant and same with the designed value.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.73-73
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• 2011

현재의 NATM터널에 대한 물량은 설계도면을 기반으로 산출되는데, 이러한 방법은 수작업에 많이 의존하게 되므로 실수로 인한 물량의 오류와 사람의 능력에 따른 물량의 차이가 나타나게 된다. 본 연구는 BIM기반의 모델에서 자동적으로 물량을 산출하여 물량산출의 오류나 차이점을 바로잡고 설계변경에 따른 물량산출작업을 효율적으로 수행하려는 프로젝트에 필요한 BIM 모델링을 통한 물량산출 프로세스의 가이드라인을 제시한다. 또한, 여러 BIM 프로그램들은 각각의 모델링 및 물량산출 방식을 가지고 있어서 하나의 프로세스로 통합하기 어려운 문제가 있기 때문에 본 연구에서는 Autodesk사의 Revit Structure에 적합한 작업 프로세스에 대한 가이드라인을 제시하며 NATM 터널의 전체 구간이 아닌 본선구간만을 대상으로 한다. 본 연구는 전체적인 NATM 터널의 BIM기반 물량산출 모델링 프로세스를 BIM 모델링과 BIM 물량산출로 분리하였다. BIM 모델링 프로세스는 물량산출의 대상과 범위 설정, 모델링을 위한 CAD도면 작성, 패밀리 파일의 설정, 공종별 모델링 작업으로 구성된다. 물량산출의 대상과 범위 설정 단계에서는 NATM 터널의 CAD 파일과 수량 산출서를 분석하여 물량산출을 위한 공종별 물량산출 범위를 확정하고, 도면에 표시되지 않는 물량정보를 파악하여 물량 값을 정확하게 산출할 수 있도록 하며, 모델링을 위한 CAD도면 작성 단계에서는 Revit Structure 특성을 고려하여 모델링에 참조하는 CAD 도면을 Revit Structure에서의 모델링에 적합하게 편집해야한다. 그리고 패밀리 파일의 설정과 공종별 모델링 작업 단계에서는 CAD도면과 Revit Structure의 패밀리 파일과의 단위를 일치시키고 NATM 터널의 특성에 맞게 공종별 모델링을 실시한다. BIM 물량산출 프로세스는 모델링 데이터의 분할, 패밀리의 재구성, 물량산출로 구성된다. 모델링 데이터의 분할단계에서는 물량산출의 목적에 맞게 CAD에서 기준선을 작성하여 공종별 모델링이 작성된 패밀리 파일로 불러온 다음 모델을 분할해야한다. 그리고 패밀리의 재구성과 물량산출단계에서는 분할된 공종별 모델의 패밀리 파일을 프로젝트 파일로 불러온 다음 물량산출의 목적에 맞게 재배치하여 물량을 산출한다.

• Geotechnical Engineering
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• v.1 no.1
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• pp.31-46
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• 1985

An extensive program of tunnel instrumentation has been Implemented in the construction of the Seoul Subway Line 3 and 4, in which the NATM was adopted as the main tunnelling technique. Among more than ten instrumented sections in the downtown area, five representative test sections were selected for analysis in this study, with an emphasis on the surface settlement and crown settlement. Variations of the surface and crown settlement. Variations of the governing factors, such as ground conditions, tunnel geometry, and construction conditions are described in this paper. Possible mechanisms for ground deformations occurring at different stages of tunnel construction are formulated, based on overall interpretation of the field observations and data obtained.

• Journal of Korean Tunnelling and Underground Space Association
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• v.21 no.1
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• pp.1-29
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• 2019

Related to the previous paper on the typical crack pattern of tunnel lining with NATM, the characteristic defects in reinforced cement concrete lining of NATM tunnel have analyzed with the precise inspection with safety and diagnosis (PISD) by KISTEC. Depending on the reinforcing materials, steel rebar, steel fiber, and glass fiber have been implemented to reinforcing lining in various NATM tunnel constructions. Reinforcing lining with rebar are prevailed on NATM tunnel to countermeasure the weak geological circumstances, to pursuit the economical tunnel sections, and to resist the risk of tunnel deterioration. By the special act on the safety control of public facilities, the reinforced NATM tunnels for more than 1 km length are scrutinized closely to characterize defects; crack, reinforcement exposure, and lack of lining. Crack resistance by reinforcing is shown in comparison with the normalized crack to the length of tunnel. Typical exposed reinforcements in lining have exemplified with various sections. The lack of lining due to the mal-construction, spalling, fire, earthquake and leaching has been analyzed. The cause and mechanism with the field inspections and other studies has also been verified. Detailed cases are selected by the above concerns as well as the basic information from FMS (Facilities Management System). Likewise the previous paper, this study provides specialized defects in reinforced lining of NATM and it can be widely used in spreading the essential technics and reporting skills. Furthermore, it would be advised and amended for the detail guideline of Safety Diagnosis and PISD (tunnel).