• Proceedings of the KIEE Conference
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• 2005.07a
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• pp.539-541
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• 2005

본 연구의 목적은 배전선로에서 운용중인개폐기, 변압기, 피뢰기 등의 규정 접지저항을 확보코자 시행하는 접지공사에 필요한 접지봉을 땅속 깊이 시공할 수 있는 접지봉의 개발과 접지봉 시공용 기계식 타격장치를 개발 활용하는 효율적, 경제적인 접지공법을 연구함에 있다. 또한 접지봉의 경년열화특성을 최소화하고자 접지봉의 접속부 구조를 개선하여 경년열화 특성을 향상하는데 있다. 특히, 굴착이 곤란한 도심지에서 최소 면적만을 굴착하여 규정 접지저항을 확보하는 방법을 제시하고 접지의 설계 및 시공 둥 실무에 활용할 수 있도록 하였다.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 1995.03a
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• pp.27-40
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• 1995

한강하저의 지질은 수많은 대ㆍ소 단층들로 인해 심하게 교란되어 있어 지질상황의 변화가 매우 심하며, 터널을 굴착함에 있어 지하수의 유입을 차단하는 것이 안전시공을 위한 필수 과제로 직면한다. 본 고에서는 기 시공실적을 바탕으로 암반상태에 따른 차수그라우딩의 패턴을 비교ㆍ검토하였다. 본 구간에서는 암반상태에 따라 5가지 패턴이 적용되었으며, 경암 암반일 경우는 상부반단면만을 주입범위(주입범위 : 3.5m, 28공)로 하고 암반의 전단강도증진을 위해 강관보강을 시행하였다. 연암 암반 내지 파쇄대가 부분적으로 협재된 경우는 상부반단면만을 주입하되 주입범위 및 그라우팅 공수를 늘리는 방식(주입범위 : 5∼7, 42∼56공)으로 보강하였다. 풍화암 암반의 경우는 전단면을 주입범위로 하여 그라우팅 공수를 늘림(주입범위 : 7m, 81공)으로서 차수효과를 증진시켰다. 또한 본 공사구간 중 가장 난제였던 연약지반대(잔류토 내지 풍화토) 85m 구간은 자문회의 등을 거쳐 주입범위, 주입길이 및 주입공수, bulk head 구간을 늘려 시공하고, 굴착하면서 차수효과를 확인하는 방식을 취하였다.

• Journal of the Korean Geotechnical Society
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• v.23 no.5
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• pp.29-41
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• 2007

An assesment technique for the quantitative evaluation of tunnel safety during tunnel excavation was newly proposed in this study using displacement measurements. First of all, field measurement guidelines used at tunnel construction sites in Korea and other countries were investigated. It was found out that the criteria of the guidelines were not clear and varied depending on the construction sites. The practical use of field measurement data for the evaluation of tunnel safety was very limited due to uncertainties of the guidelines related to the interpretation of measured data during the excavation. Critical strain concept is introduced in this study for the assesment of tunnel safety during the tunnel excavation. Moreover, the characteristics of tunnel displacements caused by the tunnel excavation were investigated in detail in order to investigate the practical application of the critical strain concept. The total tunnel displacements can be subdivided into three parts: displacements occurring ahead of tunnel face, displacements occurring prior to measurements, and displacements occurring after the installation of instruments. The characteristic of each portion of displacements is analysed in this study. Finally, a general method on the use of the displacement measurement data for the critical strain concept was suggested in the concrete manner, considering the field measurement practice in Korea.

• Tunnel and Underground Space
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• v.13 no.3
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• pp.196-206
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• 2003

In order to investigate the workability of Raise Boring Machine(RBM) such as utilization, penetration rate and advance rate, a vertical shaft of 98 m in length and 3.05 m in diameter was constructed in the layer of conglomerate by using the RBM in this study. In addition, field data from tow different construction sites including water-pump power plant tunnel, roadway tunnel and mining tunnel by RBM were collected and analyzed. The results show that the average weekly bored length is 19.3 m and its average utilization is between 54.3 % and 75.1 % very higher than that of the TBM(Tunnel Boring Machine). It also turns out that the bit force increases linearly with respect to the increase of the RPM(revolution per minute) of RBM. However, the net penetration rate decreases with the increase of bit force, RPM of RBM and depth of shaft. The findings of this study can be used to provide the useful information for the design of shaft and the selection of RBM.

• Explosives and Blasting
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• v.35 no.4
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• pp.36-47
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• 2017

Due to civil complaints on vibrations and noises arising from blasting, mechanical excavation has been widely used for tunneling rather than the method of blasting, especially in the case of being in a close-proximity of 10M-20M range to a safety-thing. However, mechanical excavation, though less, it does increase the cost of whole construction project as the period of excavation is much prolonged from lack of constructability. This study aims to research and develop an effective blasting method that can ensure the constructability of shortened excavation period whilst not compromising the safety of the safety-things in a proximity to the blasting site by using a combination of an electronic detonator that can accurately control its delay period and a Low Vibration Explosives(LoVEX) that is effective on vibration control.

• Journal of the Korean GEO-environmental Society
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• v.23 no.12
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• pp.17-23
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• 2022

This paper analyze the precast panel retaining wall's safety factor changes based on the numerical analysis using PLAXIS 2D software. Numerical analysis conditions include construction method, nail and panel fixing method, backfill material compaction conditions, rainfall conditions. The classification according to the construction method of the precast panel retaining wall includes the top-down and bottom-up methods. The difference between the top-down and bottom-up methods is the presence or absence backfill material and the ground excavation method. The top-down method involves vertically excavating the ground and attaching the panel using mortar, but in the bottom-up method, the ground is vertically excavated and harden the backfill material. As a result of numerical analysis, the top-down method secured a higher safety factor in all cases except the rainfall conditions.

• Geotechnical Engineering
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• v.1 no.2
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• pp.81-92
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• 1985

Braced excavation for a new building was carried out at a very close proximity of an existing tall building of T.hick columns are supported by indict.ideal spread footings on sand layer The excavation was planned to reach far below the footing level of the existing building. To assess the foundation performance and stability of the existing building, the behavior of 9round subjected to loss of confinement from excavation was analytically studied using finite element method. Field instrumentation was also conducted to monitor the actual ground responses during excavation. Based on these studies, various remedial measures weere taken to minimize the adverse effects to the building, and excavation was successfully completed. This paper presents the results from the analytical studies and field monitoring, and measured and measured responses at different stages of excavation.

• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.1
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• pp.91-97
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• 2007

Loads on the pillar and ground deformation in 2-arch tunnel, which is excavated in the rock mass with regular discontinuities, depending on the dips of discontinuities and the construction sequences were experimentally studied. Large scale model tests in the biaxial test facility were performed. Tested model (width 3.3m, height 3.0m, and length 0.45m) for 2-arch tunnel in 1/10 scale were built with various dips. Test results show that discontinuities have greate affects on the behavior of the 2-arch tunnel, especially on the pillar loads and ground deformation.

• Journal of the Korean GEO-environmental Society
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• v.13 no.2
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• pp.49-57
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• 2012

Large-scale collapse happened under excavation construction in the past. But, recently the trend that it is completed safely to minimize damages is growing because of increasing levels of design review and detecting signs of problems before the outbreak of large-scale collapse with proactive planning of measurement. In this paper, through studying case collapses over the past, it put the cause of the collapse in order. And then, after reviewing general information on management and utilization of measurement methods which importantly emerging recently, the type and cause of the problem during the excavation was reviewed. And the causes of problem were analyzed by targeting the site which unusual symptoms happened on measuring results under construction. In this study, the awareness that measurement management and subsurface investigation is highly important will increase for preventing large-scale collapse in advance.

• Tunnel and Underground Space
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• v.10 no.1
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• pp.25-32
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• 2000

This paper presents two new extensions to the DDA method. The extensions consist of sequential loading or unloading and rock reinforcement by rockbolts, shotcrete or concrete lining. Examples of application of the DDA method with the new extensions are presented. Simulations of the underground excavation of the Unju Tunnel of Kyungbu High Speed Railway Project in Korea were carried out to evaluate the influence of excavation sequence and reinforcement on the tunnel stability. The results of the present study indicate that improper selection of excavation sequence could have a destabilizing effect on the tunnel stability. On the other hand, reinforcement by rockbolts and shotcrete can stabilize the tunnel. It is found that, in general, the DDA program with the three new extensions can now be used as d practical tool in the design of underground structures. In particular, phases of construction (excavation, reinforcement) can now be simulated more realistically.