• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.4
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• pp.135-140
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• 2005

In case of rock bolt useable by tunnel reinforcement methods at field is applied problem of typical rock bolt pull test diagram method propositional in documents and is not thesis of clearness analysis basis about result of rock bolt pull test. So this paper suggested in consideration of foreign basis and field condition that the first, "suggestion of apposite diagram method at tight ground and difference application of rock bolt pull test method at loose and tight ground" and the second, "thesis of estimation basis non-thesis of design and specification, test etc".

• Geomechanics and Engineering
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• v.13 no.1
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• pp.63-77
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• 2017

The failure mechanism of a deep hard rock tunnel under high geostress and high geothermalactivity is extremely complex. Uniaxial compression tests of granite at different temperatures were conducted. The complete stress-strain curves, mechanical parameters and macroscopic failure types of the rock were analyzed in detail. The brittleness index, which represents the possibility of a severe brittleness hazard, is proposed in this paperby comparing the peak stress and the expansion stress. The results show that the temperature range from 20 to $60^{\circ}C$ is able to aggravate the brittle failure of hard rock based on the brittleness index. The closure of internal micro cracks by thermal stress can improve the strength of hard rock and the storage capacity of elastic strain energy. The failure mode ofthe samples changes from shear failure to tensile failure as the temperature increases. In conclusion, the brittle failure mechanism of hard rock under the action of thermal coupling is revealed, and the analysis result offers significant guidance for deep buried tunnels at high temperatures and under high geostress.

• 한국터널공학회:학술대회논문집
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• 2005.04a
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• pp.87-104
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• 2005

Rock masses represent natural systems that are inherently complex and in which multiple mechanisms occur. Rock engineering systems such as tunnel and slope interact with surrounding systems through an exchange of both mass and energy. Accordingly the complex nature of rock masses calls for a system approach, and the open nature of rock engineering even requires the engineering to be controlled by a system approach for surrounding environments. However, traditional methods cannot take all variables and their interactions into account and are limited to the system with single mechanisms. Therefore, they are not proper for a complex and open system, and also cannot portray the whole system. Thus, a system approach is indispensable to rock engineering for dealing with the whole of a complex and open system. In this paper Mechanism Path Analysis Methodology (MPAM) Is Introduced for a system approach to rock engineering. The analysis by the methodology gives us all the information of systems behavior in the context of the whole system in order to accomplish the optimum design in accordance with the project objectives and analysis purposes. As an application a conventional model for the evaluation of TBM tunneling performance system is analyzed by MPAM and the result is compared with that by a traditional method.

• Tunnel and Underground Space
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• v.16 no.3 s.62
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• pp.203-208
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• 2006

This report is to introduce an article to compare 3 kinds of methods as RMR, Q-system and RMi published in Tunnel and Tunnelling Technology 2003. As rock mass classification is applied to estimate the amount of the support as an empirical design method, an attempt has been made to evaluate the parameters for classifications and their variations by Professor Nilsen and his team in Norway. Representability and reproducibility in measuring the field parameters are discussed and sensitivity of rating values in the three methods is also analyzed in this research. Although some parameters have high variation in rating among the 5 observers, the rock mass class has been found to be quite similar.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.6
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• pp.443-450
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• 2010

A concrete lining of NATM tunnel had been considered as interior materials. But recently we consider it as structural materials. Therefore we must consider various loads. Relaxed rock load is a main load which decides thickness and reinforcement presence of concrete lining. In practice conservatively, Terzaghi's rock load theory has been accepted to estimate relaxed rock loads in urban subway tunnel design. This study investigates the equations of relaxed rock loads used in the design of NATM concrete lining. Structural analysis are executed based on various equations of relaxed rock loads, and concrete lining forces are compared.

• Tunnel and Underground Space
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• v.21 no.4
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• pp.281-286
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• 2011

The west underground express way is a recent initiated BTO (Build-Transfer-Operate) project for releasing heavy traffic of the existing west express way which is notorious on-ground road for extremely traffic stuck area in the west of Seoul, South Korea. The new express way for light vehicles is the first double-deck tunnel ever designed in South Korea and 10.91 km long including both open cut structures and concrete lining with middle-deck in bored tunnel. Because the new express way is going through underground of heavily populated area, mechanical & electrical design for the safety of drivers in tunnel is one of the most important parts among many design issues. This paper discusses M & E design focuses including ventilation-evacuation plan and various safety facilities.

• Geomechanics and Engineering
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• v.16 no.1
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• pp.35-47
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• 2018

This paper investigates the mechanisms of tunnel spalling and massive tunnel failures using fracture mechanics principles. The study starts with examining the fracture propagation due to tensile and shear failure mechanisms. It was found that, fundamentally, in rock masses with high compressive stresses, tensile fracture propagation is often a stable process which leads to a gradual failure. Shear fracture propagation tends to be an unstable process. Several real case observations of spalling failures and massive shear failures in boreholes, tunnels and underground roadways are shown in the paper. A number of numerical models were used to investigate the fracture mechanisms and extents in the roof/wall of a deep tunnel and in an underground coal mine roadway. The modelling was done using a unique fracture mechanics code FRACOD which simulates explicitly the fracture initiation and propagation process. The study has demonstrated that both tensile and shear fracturing may occur in the vicinity of an underground opening. Shallow spalling in the tunnel wall is believed to be caused by tensile fracturing from extensional strain although no tensile stress exists there. Massive large scale failure however is most likely to be caused by shear fracturing under high compressive stresses. The observation that tunnel spalling often starts when the hoop stress reaches $0.4^*UCS$ has been explained in this paper by using the extension strain criterion. At this uniaxial compressive stress level, the lateral extensional strain is equivalent to the critical strain under uniaxial tension. Scale effect on UCS commonly believed by many is unlikely the dominant factor in this phenomenon.

• Tunnel and Underground Space
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• v.14 no.4
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• pp.269-274
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• 2004

In this study reduced-scale experiments were conducted to determine the backlayering distance in tunnel fires. The 1/20 scale experiments were carried out under the Froude scaling using ethanol square pool fire ranging from 8 to 1km in each side with total heat release rate from 2.47 to 12.30 ㎾. It has been found that ventilation velocity increases with aspect ratio(tunnel height/tunnel width). At L$\_$B/$\^$*/ ＜5 the ventilation velocity increases proportional to the backlayering distance from 0.25 power of the heat release rate. However at L$\_$B/$\^$*/ $\geq$5 the ventilation velocity varies as the 0.3 power of the heat release rate.

• Tunnel and Underground Space
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• v.21 no.6
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• pp.427-438
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• 2011

Segment lining is a key permanent lining structure to maintain the shield tunnel stability in shield tunnel operation. Moreover, segment lining generally accounts for the largest proportion in the shield tunnel construction costs. As a result, technical improvements to increase its economic feasibility have been actively carried out. This study aims to propose the development directions of high-performance segments from their recent cutting technologies. In addition, based on over 2,100 world-widely collected segment design data, a series of statistical analyses of segment key design parameters such as thickness, width and the number of divisions as well as segment materials were carried out to approximately estimate them in a design stage.

• Tunnel and Underground Space
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• v.19 no.2
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• pp.71-76
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• 2009

The GK immersed tunnel as a part of Busan-Geoje Fixed Link Project, is the first attempt in Korea. In spite of existing of many difficulties in construction like the absent of construction cases in Korea, the connection work under approximately 50 m below sea level and weak ground condition, etc., now eight caissons were installed successfully on the accurate position and we are going to install upto the twelfth caisson in this year. The purpose of this paper is to introduce design and construction conditions of the GK immersed tunnel to advise the tunnel designers who will handle the similar project.