• Tunnel and Underground Space
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• v.17 no.5
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• pp.411-427
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• 2007

Reliability in tunnel analysis is necessary to accomplish technically sound design and economical construction. For this, a thorough understanding of the construction procedure including the ground-support interaction has to be obtained. This paper describes a proper modelling technique to simulate the behavior of the steel fiber reinforced shotcrete (SFRS) which maintain the supporting capability in post-failure regime. The additional supporting effect of the steel support was also verified by 3-D analyses and a new load distribution factor were proposed. The use of the plastic moment limit (PML) alone can eliminate the occurrence of the awkwardly high tensile stress in the shotcrete and can successfully model the post-peak ductile behavior of the SFRS. But with this method, moment is limited whenever the stress caused by moment reaches tensile strength of the shotcrete irrespective of the stress by axial force. Therefore, it was necessary to find a more comprehensive method which can reflect the influence of the moment and axial force. This can be accomplished by the proper use of "liner element" which is the built-in model in FLAC. In this model, the peak and residual strength as well as the uniaxial compressive strength of the SFRS can be specified. Analyses were conducted with these two models on the 2-lane road tunnels excavated in class IV and V rock mass and results were compared with the conventional elastic beam model. Results showed that both models can reflect the fracture toughness of the SFRS which could not be accomplished by the elastic beam model.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 2008.03a
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• pp.41-49
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• 2008

• The Journal of Engineering Geology
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• v.3 no.3
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• pp.215-230
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• 1993

In-situ rock mass demonstrates the variety of structural features, and especially the mechanical and spatial characteristics of joint (or joint system) greatly affect the deformation and fallure strength of the rock mass. In this study finite element model capable of analyzing the viscoplastic behavior of reinforced jointed rock mass has been developed based on equivalent material approach. Accuracy and reliability of the numerical model have verified by simuiating the behavior of simplified block model and comparing the results with analytic solutions. Practical applicability was also demonstrated by analyzing the time-dependent behavior of underground oil storage tunnel and assessing the reinforcement effect of rockbolt.

• Journal of Korean Tunnelling and Underground Space Association
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• v.24 no.6
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• pp.617-628
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• 2022

A ground support pattern should be designed by properly integrating various support materials in accordance with the rock mass grade when constructing a tunnel, and a technical decision must be made in this process by professionals with vast construction experiences. However, designing supports at the early stage of tunnel design, such as feasibility study or basic design, may be very challenging due to the short timeline, insufficient budget, and deficiency of field data. Meanwhile, the design of the support pattern can be performed more quickly and reliably by utilizing the machine learning technique and the accumulated design data with the rapid increase in tunnel construction in South Korea. Therefore, in this study, the design data and ground exploration data of 48 road tunnels in South Korea were inspected, and data about 19 items, including eight input items (rock type, resistivity, depth, tunnel length, safety index by tunnel length, safety index by rick index, tunnel type, tunnel area) and 11 output items (rock mass grade, two items for shotcrete, three items for rock bolt, three items for steel support, two items for concrete lining), were collected to automatically determine the rock mass class and the support pattern. Three machine learning models (S1, A1, A2) were developed using two machine learning algorithms (SVR, ANN) and organized data. As a result, the A2 model, which applied different loss functions according to the output data format, showed the best performance. This study confirms the potential of support pattern design using machine learning, and it is expected that it will be able to improve the design model by continuously using the model in the actual design, compensating for its shortcomings, and improving its usability.

• Proceedings of the KAIS Fall Conference
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• 2011.12a
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• pp.25-28
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• 2011

본 연구는 반도체 산업에서 반도체장비유지보수에 사용되어지는 반도체장비 유지보수 분야의 전문기술인력을 효과적으로 양성할 수 있는 반도체장비 유지보수의 자격종목을 개발하고자 하는데 그 목적이 있다. 연구의 목적을 달성하기 위하여 반도체장비 유지보수 분야의 국내외 실태 조사, 문헌조사를 통하여 반도체장비 유지보수 관련 교육훈련기관 및 검정 수요 예상 인력을 파악했으며, 유사자격제도(전자부품장착기능사, 전자부품장착산업기사, 생산자동화기능사, 생산자동화산업기사 등)를 분석하였고, 직무분석을 통하여 반도체장비유지보수기능사의 직무 및 교육내용을 분석하였다. 또한 반도체장비 유지보수 자격종목 신설에 대한 설문조사를 실시했으며, 반도체장비유지보수기능사 자격종목의 출제기준 및 채점 방법을 제시했고, 필기시험과 실기시험에 대한 모의 검정시험도 실시하였다. 이러한 결과를 토대로 반도체장비유지보수기능사에 대한 교육프로그램을 만들었으며, 자격검정을 실시할 수 있는 출제기준을 제시하였다.

• Tunnel and Underground Space
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• v.18 no.2
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• pp.107-117
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• 2008

In this study, the failure and deformation characteristics of steel fiber reinforced shotcrete (SFRS) which is a primary tunnel support was investigated to find out ground-support mutual behavior. To this end, a mock-up of a tunnel was made and experimented with the conditions of lateral earth pressure coefficient 0.5 and 1.0. During the tests, 11 hydraulic cylinders were used for loading. for better simulation of the lateral earth pressure effect, these cylinders were controlled separately by two groups; crown and side wall. Meanwhile, the deformation of shotcrete was measured by 11 LVDTs. Backfill material was also used fur better load transfer from hydraulic cylinders to shotcrete. For the validation of the mock-up test results, 3D numerical analysis is carried out. To do numerical analysis under the same condition as a mock-up test, the load history curve which was obtained during the test was tried to be simulated using an individual FISH routine in the numerical analysis.

• 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.

• Journal of the Korean GEO-environmental Society
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• v.24 no.4
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• pp.13-22
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• 2023

In this paper, through experimental research, the period when rock bolts exert support effects is presented as grout strength and through numerical analysis, the rock bolt pull-out behavior according to ground conditions and strength reduction factors is analyzed. As a result, it is determined that rock bolts exhibit their reinforcing effect at a grout strength of 5 MPa (cured for 18 hours). The influence of the boundary interface strength reduction factor was found to be significant for rock bolt displacement in weak ground conditions, for shear stress between grout and ground in highly elastic ground conditions, and for grout stress in all ground conditions. These findings are expected to contribute to the establishment of specific standards for rock bolt testing and numerical analysis, and to facilitate improved design and implementation of rock bolt reinforcement.

• Tunnel and Underground Space
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• v.22 no.5
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• pp.297-309
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• 2012

The stability assessment of abandoned gangway for the purpose of services was performed. Among the many factors that affect the stability of openings, the span of the opening in a given rock mass condition provides an important element of design. In this paper, the stability of gangway was assessed by the critical span curves proposed by Lang, the modified Mathews'stability graph method and using support measures of the Q system. In the evaluation of stability as a whole the gangway is considered as stable. But the rockfalls of wedge-shaped blocks were expected in the area in which the horizontal joints of low angle appear. The support measures such as local rock bolts are required to use for commercial purposes of the abandoned gangway. And entrance section may require the particular attention as unstable section. Since there are so many spalling due to bad blasting in the roof and sidewall of gangway, the scaling operations should be followed primarily.

• Journal of Korean Society of Steel Construction
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• v.29 no.5
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• pp.353-359
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• 2017

The purpose of this study is to evaluate the strength and behavior of the composite member in case of concrete filled steel tube embedded in concrete for application concrete filled steel tube to steel rib support in tunnel. A total of six beam specimens were prepared for steel tube in-filled with plain concrete and aerated concrete, and static bending tests were performed. As a result, the member of concrete steel tube embedded with plain concrete showed higher strength than those with aerated concrete. However, it was found that the flexural strength of member with reinforcing bar around the steel tube is more influenced by the amount of the reinforcing bar than the type of the filled concrete.