• Tunnel and Underground Space
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• v.33 no.1
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• pp.1-9
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• 2023

Roadheaders have been operated in the construction of Korean tunneling projects. The note introduces operation manual and management case of transverse type roadhead in a Korean tunneling site. The cutting and reaction forces of axial and transverse type cutting heads were qualitatively analyzed. The shaping surfaces of tunnel faces were visualized in both cases of fixed and auto-controlled telescopic cylinder conditions. Excavating with fixed cylinder, concave surfaces were shaped on tunnel face. The total processes of sumping and shearing were illustrated for excavating hard rock tunneling. The supplementary graphical explanations for total tunneling procedures in Korea were provided.

• Explosives and Blasting
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• v.21 no.3
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• pp.1-10
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• 2003

터널굴착발파공법의 하나인 V-cut발파공법은 터널굴착기술이 발전되는 과정에서 초기에 개발되어진 기술이나 작업의 간편성과 효율성으로 인하여 많은 터널굴착공사에서 이용되고 있는 발파공법이다. V-cut발파공법은 일자유면 상태에서 V형으로 심발공을 발파하고 심발공에 의해 형성된 자유면을 이용하여 확대공으로 굴착공간을 넓히는 발파 방법이며 심발발파의 굴진장에 의해 단일발파당 굴진장이 결정된다. V-cut발파법이 개발된 이래 V-cut발파의 굴진장을 증대시키기 위한 방법으로 심발발파공의 구속저항을 감소시키기 위해 보조심발공을 발파하여 형성된 자유면에 의해 심발공의 최소저항선거리를 줄여 발파하였으나 심발공의 구속저항이 감소되지 않아 발파효율이 증대되지 않았으며 발파진동 또한 가장 크게 발생하였다. 이와 같은 현상은 최소저항선거리의 감소효과에 대한 발파기술상의 이론에 문제가 있기 때문이다. 본 연구에서는 V-cut발파법의 심발공에 대한 구속저항감소효과가 발현될 수 있는 조건들을 검토하여 최소저항선거리의 감소효과가 발현될 수 있는 조건을 제시 하여 심발공의 발파효율을 증대시키고 발파진동이 적어지는 발파방법을 제안하려 한다.

• Explosives and Blasting
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• v.36 no.4
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• pp.16-25
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• 2018

In order to reduce ground vibration during tunnel excavation, a free surface blasting method has been applied in which a partial free surface is formed on the excavation surface and controlled blasting is performed. In this study, the ground vibration reduction due to artificial joints was evaluated by forming artificial joints on center cut using diamond wire saw and comparing the ground vibration caused by center cut blasting. As a result of comparison, ground vibration was reduced by artificial joints center cut blasting more than normal center cut blasting, and the ground vibration reduction effect of horizontal artificial joints center cut blasting was evaluated more than that of vertical artificial joint center cut blasting.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 1995.03a
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• pp.109-120
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• 1995

절리가 발달된 경암질 암반내에서 터널을 굴착할 때에 발생하는 심각한 문제중의 하나는 암반내에 존재하는 불연속면과 굴착에 의하여 형성되는 자유면에 의하여 생성된 블록의 낙반 사고이다. R.E. Goodman, Gen-hua shi$^{3)}$ 등에 의하여 제안된 블록이론은 암반사면이나 지하공동에 존재하는 절리들의 방향성을 조사하여 우세한 방향의 절리들에 의하여 발생하는 블록들의 안정, 불안정 및 낙반의 가능성 여부를 판정할 수 있도록 하였다. (중략)

• Tunnel and Underground Space
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• v.26 no.6
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• pp.475-483
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• 2016

A numerical analysis model capable of predicting the shape, the size and the potentiality of collapse of tetrahedral blocks considering the persistence obtained from the field survey of joint distribution around the underground excavation surface has been developed. Numerical functions of analyzing both the exposed trace distribution on the excavation surface and the formation of tetrahedral block controlled by the extent of joint surface have been established and linked to the previously developed three dimensional deterministic block analysis model. To illustrate the reliability of advanced numerical model the case of underground excavation in which the collapse of rock block had practically taken place was studied. Representative orientations of joint sets was determined based on the joint distribution pattern observed on the excavation surfaces. The formation of block on the roof of underground opening was analyzed to unveil the potential tetrahedral block the shape of which was very similar to the collapsed rock block. Mechanisms of collapse process has been also analyzed by considering the three dimensional shape of tetrahedral block.

• Journal of Korean Tunnelling and Underground Space Association
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• v.15 no.1
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• pp.49-57
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• 2013

The conventional blasting method generates serious blasting vibration and underbreak/overbreak in spite of its high efficiency for rock excavation. To overcome these disadvantages, this paper introduces an alternative excavation method that combines the conventional blasting process with the free surface on the perimeter of the tunnel face using waterjet cutting technology. This proposed excavation method has advantages of (1) reducing vibration and noise level; (2) minimizing underbreak and overbreak; and (3) maximizing excavation efficiency. To verify the effects of the proposed excavation method, field tests were performed with a smooth blasting method at the same excavation conditions. Test results show that the vibration is reduced by up to 55% and little underbreak/overbreak is generated compared with the smooth blasting method. In addition, the excavation efficiency of the proposed method is greater than that of the smooth blasting method. The proposed blasting method with a free surface using waterjet cutting can be applied to urban excavation construction as well as to underground structure construction.

• Journal of the Korean Geotechnical Society
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• v.24 no.2
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• pp.27-36
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• 2008

This paper analyzed the effects related to the difference of the geometrical shape of the ground excavation by comparing the displacements of the earth retaining wall of the strut resulting from the change of the excavation breadth B and the excavation length L, adopting the three dimensional FDM analysis. It appeared that the displacement of the earth retaining wall of the strut increases in accordance with the increase of L/B and it decreases as it becomes nearer from the center to the comer where the temporary structural system forms, and the wale member is closured because of the effects of the confining effect by the closure of the earth retaining wall and the wale member. This paper proposed a formula in which the results of three dimensional FDM analysis which considers the shape of the excavation plane can be obtained from those of two dimentional FDM analysis which does not consider the shape of the excavation plane. And the results of the formula were compared with those of the site instrumentation analysis.

• Journal of the Korean Geotechnical Society
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• v.17 no.5
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• pp.17-27
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• 2001

지하 굴착공동의 천장면에 형성되는 잠재적 키블록의 존재성과 운동학적 거동 양상 및 안정성을 해석적으로 분석할 수 있는 시스템을 개발하였다. 천장에서 측정된 절리들의 상대적인 위치와 방향성 자료를 이용하여 데이타베이스를 구축하였으며, 굴착설계도와 연계된 전산절리도를 작성하였다. 잠재적 키블록의 존재성과 거동양상은 사면체로 가정된 블록 옆면의 3차원 공간에서의 평면식을 절리의 방향성에 의거하여 구성하며 대수학적으로 분석되었다. 블록의 안정성 분석은 자중에 의해 미끄러짐이 발생되는 블록면의 공간 기하학적 특성을 고려하여 수행하였다. 개발된 분석시스템의 현장활용성을 검증하기 위하여 언양 자수정동굴에서 키블록 형성 및 거동양상을 조사하여 분석결과와 비교하였다.

• Explosives and Blasting
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• v.26 no.1
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• pp.49-55
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• 2008

Mechanical excavation techniques employing tunnel boring machines (TBM) and rock splitters have been proposed to minimize rock damage for tunnel and underground waste repository facilities. Such a mechanical excavation, however, is extremely expensive and not applicable in all cases. For these reasons, controlled blasting using notched charge holes have been suggested to achieve crack growth along specific directions and inhibit growth along other directions. This study introduces a dynamic fracture process analysis code to simulate fracture processes of rock which has a notched charge hole.

• Journal of Korean Tunnelling and Underground Space Association
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• v.14 no.3
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• pp.261-275
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• 2012

This paper presents numerical analysis of the mud cake infiltration behaviour which is influenced tunnel face stability during excavation by slurry shield TBM. This analysis method can make useful data to select proper shield TBM type and to set up the construction plan. But effective analysis did not proposed until now. In this paper, we carried out numerical analysis using by $PFC^{2D}$ fluid coupling simulation which is suitable for sandy soil modelling. As a analysis result, we checked that the slurry infiltration behaviour varied with soil permeability and slurry characteristic(specific weight, viscosity etc). This analysis method is helpful safety excavation through anticipating the proper slurry viscosity at the design stage and verifying the slurry quality at initial excavation stage.