• Tunnel and Underground Space
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• v.11 no.1
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• pp.30-35
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• 2001

Focusing on the bench length, this paper presents the results of 3-dimensional elafto-plastic FE Analysis un tunnels of full face, mini-bench and short bench excavated in weathered rock. Influences of unsupported span, horizontal to vertical stress ratio, thickness of shotcrete on the behavior of rock and support were a1so studied. Results showed that displacements of mini-bench tunnels responded more sensitively to bench lengths than those of short bench. The effects of bench excavation on upper half displacement increased with longer unsupported span. Horizontal to vertical stress ratio showed a greater influence on displacement and preceding displacement ratio or sidewall rather than those of crown and invert.

• Tunnel and Underground Space
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• v.16 no.5 s.64
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• pp.405-412
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• 2006

It is well known that shotcrete is the most important support member for the construction of large underground spaces. Generally, the strength of the field shotcrete is heavily dependent on the field mixing and spraying conditions so that it is different from the strength of the shotcrete mixed in laboratories. As a support member, the early strength of shotcrete unlike concrete is very important to the initial stabilization of the underground spaces. Therefore, the field methods to efficiently test the early strength of shotcrete have been highly required. This paper aimed to verify the pneumatic pin penetration test and the point load test for measuring the early strength of the field shotcrete. As a result of the experiments through a series of uniaxial compression, pin penetration, and point load tests for the range of the early shotcrete strength, two equations to estimate reliably the uniaxial compressive strength by the pin penetration and the point load tests were acquired.

• Tunnel and Underground Space
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• v.19 no.4
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• pp.355-365
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• 2009

This paper proposes an elasto-plastic finite difference method which is useful for the stability evaluation of concrete lining installed in a deep circular tunnel. Mohr-Coulomb criterion is assumed for the condition of yielding in both the rock mass and concrete lining. In order to take into account the installation delay of lining after the excavation, the outer boundary pressure acting on the lining was calculated with the consideration of the convergence occurred before the lining installation. The distributions of stress and displacement in the rock mass and lining were calculated based on the method proposed Lee & Pietruszczak (2008). The applicability of the proposed method was demonstrated by conducting the elasto-plastic analysis of concrete lining supporting an imaginary compressed air storage tunnel. The analysis result revealed that the exact determination of the boundary pressures acting on the concrete lining is of importance in the stability analysis of concrete lining.

• Journal of Korean Tunnelling and Underground Space Association
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• v.23 no.1
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• pp.37-45
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• 2021

The construction of the tunnel portal should be careful because cover depth is shallow and it is difficult to exhibit the arching effect. Tunnel stability may be reduced with additional embankment above the portal of tunnel. In this study, in order to examine the stability of the tunnel according to additional embankment above the portal of tunnel, numerical analysis was performed while changing the ground conditions and height of embankment. As a result of the numerical analysis, it was found that the allowable flexural compressive stress of shotcrete and allowable axial force of rockbolts were exceeded when the height of additional embankment was 12 m in rock mass rating V. When considering the displacement, the range of the plastic region and the behavior of the support materials, the tunnel stability seems to be greatly reduced if the height of additional embankment above the portal of tunnel exceeds 10 m.

• Journal of Creative Information Culture
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• v.5 no.2
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• pp.95-104
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• 2019

The changes triggered by the fourth industrial revolution will change society in ways we have never seen before. Accordingly, our education should be able to prepare for a new future in the era of the fourth industrial revolution. For the students' futures, this study presented a curriculum to improve core competencies of future talents based on analyse of current education content and related education fields. To achieve this goal, this study was carried out in the following steps. First, core competencies of future talents and the current curriculum were analyzed. Second, the educational curriculum's goals, contents, and systems were developed to enhance future talent capabilities. Third, the developed curriculum was applied in the field to verify its effectiveness. This study may be used as a reference for future education and the development of future human resources.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.4
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• pp.387-394
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• 2009

The objective of this study is to evaluate the durability and deterioration of concrete lining in the seven conventional tunnels. These tunnels were constructed about 40~70 years ago, and closed about 10~40 years ago. The field investigation and various laboratory testings were performed for this study. It was observed from the visual, examinations that the concrete linings of 7 tunnels were severely deteriorated, such as, cracks, leakages, desquamation, and exploitations. The compressive strengths obtained from rebound hardness method and uniaxial compressive strength test on core specimens largely differed depending on the locations in the tunnel. The maximum compressive strength of concrete lining was greater about 2 times than the minimum compressive strength of concrete lining in the same tunnel. The results of micro-structural analysis showed that the substances deteriorating the concrete lining, such as ettringite and thaumasite, were detected in the concrete lining of tunnel.

• Journal of fish pathology
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• v.20 no.2
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• pp.147-160
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• 2007

Four strains of water mold, ChS-E0511, RaT-E0511, RaT-A0512 and MaS-F0512, were isolated from salmonid fish and/or their eggs taken from culture farms in Yangyang, Milyang and Pyeongchang, Korea in 2005. Descriptions of their morphological aspects, the results of the phylogenetic analysis conducted, and the sequence of the small sub-unit 18S rRNAs of the isolates confirmed that they all belong to the species Saprolegnia parasitica. Only one species, ChS-E0511, which was isolated from fertilized eggs of the chum salmon, was classified as part of the S. parasiticaGroup 1 according to its oogonia and gemmae production. The chemotherapeutic effects of various chemicals on the ChS-E0511 strain were assessed from the inhibitory effects of growth in GY media and the relative ratio of eyed eggs to fertilized eggs of the rainbow trout. Malchite green, a prohibited substance in food animals, was better than others, such as the Opuntia ficus-indicaextract, 2-bronopol, and sodium chloride. These results suggest that the fungi isolated from salmonids and/or their eggs identified as S. parasitica were composed of more than two groups. These isolates will be useful in an intensive evaluation of therapeutic agents.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.5
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• pp.455-468
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• 2013

In recent, various types of steel pipe-roof methods, which is reinforced by mortar after propulsion of steel pipe into the ground, have been used for the construction of trenchless underpass. Integrated steel pipe-roof has flexural stiffness and can resist against overburden load and reduce the stress acting on the concrete underpass structures. Due to arching effect, vertical and horizontal stress distribution around the steel pipe-roof is changing. In this study, therefore, the characteristic of stress distribution around the underpass induced by the construction of integrated steel pipe-roof is investigated by using numerical method. To examine the soil-structure interaction, interface element is introduced. Results show that vertical stress acting on the concrete structure placing inside the steel pipe-roof is significantly reduced due to arching effect and flexural stiffness of integrated steel pipe-roof. Design load can be reduced and effective design of underpass will be available if the earth pressure reduction due to arching effect is considered in the design stage.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2021.04a
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• pp.28-29
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• 2021

애기똥풀(Chelidonium majus L. subsp. asiaticum H.Hara)의 지상부는 백굴채라고 불리며 항암, 항균 등의 효능을 가지고 있어 예로부터 약용으로 이용되었다. 그러나 천연 약용소재로 개발가치가 높음에도 불구하고 실생묘의 대량 확보를 위한 종자번식 관련 연구가 전무한 실정이다. 본 연구에서는 애기똥풀의 발아 및 휴면 특성을 분석함으로써 추후 종자번식을 위한 기초자료를 제공하기 위해 수행되었다. 실험재료로 사용된 애기똥풀 종자는 2019년 6월 경상북도 봉화군에서 채종하였으며 정선 후 건조상태로 실온(25℃)에 보관하였다. 종자의 1000립중은 0.57±0.01g이며, 배종비는 0.21±0.12로 조사되어 형태적으로 미성숙한 배를 가지고 있다. 종자의 활력은 테트라졸륨 검정을 통해 79%로 확인되었다. 종자의 기본 함수율은 7.64±0.25%였으며, 침지 2일 차에 최대함수율(32.6±0.34%)에 도달하였다. 초기 발아검정은 25/15℃ (light/dark, 16/8h)챔버에서 명조건과 암조건으로 구분하여 30일간 진행하였으며, 암조건은 알루미늄 호일로 광을 완전히 차단하고 최종 발아율만 조사하였다. 발아율을 조사한 결과, 명조건은 0.75±0.80%, 암조건은 5.50±1.55%로 조사되어 형태적인 휴면과 생리적인 휴면을 모두 갖는 것으로 판단하였다. 애기똥풀의 생태적인 환경을 고려하여 12주의 Summer temperature(S12, 25/15℃, 16/8h)로 층적하고 연속하여 Autumn temperature(A, 15/10℃, 16/8h)를 4주(A4)와 8주(A8)로 달리하여 종자의 휴면타파를 유도하였다. 층적 후 발아율은 모두 증가되었으며, S12-A4(54%)는 S12-A8(24.5%)에 비해서 휴면타파에 효과적이었다. 휴면타파 효과의 증진을 위해 층적처리한 종자를 500ppm의 GA₃와 GA₄₊₇에 각 24시간동안 4℃에서 침지시킨 뒤 동일한 조건에 파종하였다. GA₃가 처리된 S12-A4는 발아율이 82.0%, S12-A8는 30.8%로 유의적으로 증가하였으나 GA₄₊₇ 처리는 S12-A4(48.5%)와 S12-A8(21.3%)에서 발아율 향상 효과가 없었다. 결론적으로 애기똥풀의 휴면타파를 위해서 12주의 Summer temperature와 4주의 Autumn temperature 변온층적과 추가 GA₃ 처리가 휴면타파를 위한 효과적인 처리방법으로 판단된다.

• Journal of Plant Biotechnology
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• v.41 no.2
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• pp.94-99
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• 2014

This study was conducted to elucidate the effect of light sources and explant types on in vitro shoot multiplication and rooting of a rare and endangered plant Abeliophyllum distichum. Both apical buds and axillary buds were used as explants under 4 different light sources, cool white florescent light (F), 100% blue light-emitting diode (LED) (B), 50% blue and 50% red LED mixture (BR), and 100% red LED (R). Clear difference was observed in terms of shoot proliferation by light sources types but not by position-dependent explant types. Multiple shoot induction rates were enhanced under both B and BR light sources. Spontaneous rooting was induced in shoot induction medium under B light source. Both the rates of rooting and numbers of roots per explant were higher in apical bud explants compared to axillary bud explants. Interestingly R light source stimulated shoot elongation but inhibited root development. Therefore, our results suggest that the use of apical bud explants under B or BR light sources is suitable for in vitro micropropagation of a rare and endangered plant species, Abeliophyllum distichum.