• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.1
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• pp.87-94
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• 2010

This study mainly focused on the subsurface settlement due to shallow and deep tunneling in sandy ground. In order to figure out theoretical deformation patterns in association with the ground loss during the progress of tunneling, laboratory model tests using aluminum rods and finite element analyses using the CRISP program were carried out. As a result of comparison between the model test and the finite element analysis, the similar deformation patterns were found. In addition, it was identified that the most K values obtained from both the FEA and the model tests were distributed between Dyer et al. (1996) and Moh et al. (1996) of the field observation data. Based on the model test data, the linear equation of K for the sandy soil could be obtained.

• Explosives and Blasting
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• v.19 no.3
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• pp.105-113
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• 2001

채석, 굴착, 가공과 같은 워터젯 응용분야에서 대상재료에 깊은 홈(kerf)을 절단할 수 있는 실험실용 회전식 슬로터(slotter)를 제작하여 암석을 대상으로 워터젯 시스템의 절단효율을 시험하였다. 고압펌프는 유율 7.5 l/min, 압력 379 MPa, 용량 75 kW급의 JETPAC을 주로 사용하였고, 암석시료는 화강석인 제천석, 거창석을 사용하였다. 시험과정에서는 물과 연마재 투입에 의한 절단 및 진동식 슬로터에 의한 슬롯절단 기초시험을 먼저 수행하고, 그 결과를 토대로 회전식 슬로터에 의한 절단시험을 실시하였다. 순수한 물에 의한 시험의 결과 고압수류의 토출압력은 절단심도에 정비례하였고, 노즐의 이송속도는 이차함수 형태의 반비례 관계를 보였다. 연마재 투입시험에서는 순수한 물에 의한 경우에 비해 연마재로 인한 충격력의 증가로 절단심도가 크게 증가하였는데, 유사한 조건하에서 3~5배 이상의 절단심도의 증가를 보였다. 진동식 슬로터에 의한 슬롯절삭에서는 생성된 슬롯의 내벽면이 바닥으로 갈수록 좁아짐으로써 넓은 폭의 슬롯형성은 가능하나 절삭심도가 제한되었다. 회전식 슬로터에 의한 시험에서 생성된 슬롯들은 평균 22 mm의 폭으로 내벽면이 바닥까지 서로 평행하여 깊은 심도까지 비트진입이 가능하였다. 절단율은 16~32 mm/sec의 속도범위에서 $40~160{\;}\textrm{mm}^2/sec$로 나타났다. 한편, 최대유율 24 l/min의 HUSKY S-200 펌프에 의한 시험결과 JETPAC 펌프에 비해 1.13~3.47 배의 절단심도를 보였다

• Journal of the Korean Geotechnical Society
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• v.33 no.10
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• pp.33-47
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• 2017

A self-supported temporary excavation method called IER is normally applicable to excavation depth ranging from 6.0 m to 7.0 m though the method depends on ground condition and overburden load. Combining IER with another method is required in deeper excavation depth in order to maintain the structural stability of the IER. In this study, we performed model tests and 3D FE analysis to check the stability of the IER adopting soil nailing method, and to propose its effective installation method. The lateral displacement of the IER using soil nailing decreased by 92% of that of IER without soil nailing. Optimum design is possible for both economic feasibility and stability when interval spacing and length of soil nails is $1.5m(S_h){\times}0.75m(S_v)$ and 86% of excavation depth, respectively. Excavation depth using IER increases 1.71 times by adopting soil nailing in increment of lateral displacement of IER right before the last excavation stage.

• Explosives and Blasting
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• v.41 no.3
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• pp.38-61
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• 2023

An Excavation Damaged Zone(EDZ) caused by blasting impact changes rock properties, in situ stress distribution, etc., and its effects are noticeable at around a radioactive waste repository located at deep underground. In particular, the increase in permeability due to the formation of cracks may significantly increase the amount of groundwater inflow and the possibility of radioactive nuclide outflow. In this study, FLAC2D and FLAC3D were used to analyze the mechanical and thermal behaviors for three categories: a)No EDZ, b)Uniform EDZ, and c)Random EDZ. It was found that the tunnel displacement in the Random EDZ case was 423% higher than that in the No EDZ case and was 16% higher than that in the Uniform EDZ case. Tunnel inflow in the Random EDZ was also 17.3% and 10.8% higher than that in the No EDZ and the Uniform EDZ case, respectively. The permeability around the tunnel was increased by up to 10 times in the corner of the tunnel wall and roof due to the stress redistribution after excavation. From the computer simulation, it was found that the permeability around the tunnel wall was partially increased but the overall tunnel inflow was decreased with increase of stress ratio. Mechanical analysis using FLAC 3D showed similar results. Slight difference between 2D and 3D could be explained with the development of plastic zone during the advance of tunnel excavation in 3D.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.113-120
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• 1999

Deep excavation,1 in the urban areas may cause terrible damages to the adjacent structures. Most damages are due to the settlement of ground during excavation work. This article introduces two actual examples of structure damage in subway construction projects. A through of attempts to find out the factors that are affecting to the settlement of ground was made through site investigations and analyses of measurement data. Some suggestions are given to prevent the repeat of trial and error in deep excavation projects. This kind of attempts are eccentrical to the development and improvement of information-oriented construction method.

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.77-84
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• 2003

Deep excavations in the urban areas have been frequently going on in large scale. Soil-nailing and Earth-anchor supporting methods are generally used in deep excavation. These construction methods cause ground disturbances during drilling process, and damages of adjacent structures and ground due to the differential settlement throughout construction period, and unexpected behaviors of supporting system according to the characteristics of drilling machine and ground condition. This article introduces two actual examples of adjacent deep excavation for the construction of university buildings in granitic Seoul area. The important results of construction and measurements obtained using Crawler drilling machine for Soil-nailing and Earth-anchor supporting methods are summarized. And some suggestions are given to improve and develop the technique of design and construction in the deep excavation projects having similar ground condition and supporting method.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.106-109
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• 2004

지표하부 상층 오염지하수의 침투로 인한 암반 지하수의 오염을 방지하기 위하여 지하수 개발과정에서 반드시 지표하부 지하수 오염방지를 이행하도록 지하수법에 규정하고 있다. 널리 알려진 지표하부 오염방지 공법으로서는 팩카그라우팅 공법(packer Grouting Method), 트레미공법(Tremie Method)과 브레든 헤드 공법(Bradenhead Method)이 있다. 그러나, 현재 대다수의 지하수 개발 현장에서는 단순히 강관을 굴착공에 억지박음함으로써 지표하부 오염방지에 가름하는 사례가 다반사이며 깊은 심도의 경우에도 종래 공법으로는 한계를 가질 수밖에 없는 실정이었다. 따라서, 본 연구에서는 차폐 팩카(Protection Packer)를 이용하여 고, 저심도의 어느 지하수 심정에서나 용이하게 역주입 상향그라우팅이 가능한 여건이 될 수 있도록 시공 사례를 통해 연구를 수행하였다.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.537-544
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• 2005

We find out many soft ground deep excavation cases where results of careless overexcavation accelerate the advance of loosening zone of adjacent ground, bucklings of struts and bottom heaves happen due to delayed supporting time. This article introduces a soft ground deep excavation case where steel pipe sheet piles were used with struts as an earth retaining system. There were 2 times of buckling in the supporting system and heaving of bottom ground due to overexcavation and insufficient penetration depth of the steel pipe sheet piles. The effort of this article aims to improve and develop the technique of design and construction in the coming projects having similar ground condition and supporting method.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.09a
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• pp.210-212
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• 2003

동위원소희석법에 의한 열이온화 질량분석법(ID-TIMS)을 이용하여 한국지질자원연구원과 에너지기술연구 원내 지하수와 강우 희토류원소의 함량을 측정/해석하였다. 분석결과를 토대로 지하수의 희토류원소 함량은 강우의 함량과 비교해 볼 때, 상대적으로 낮은 값을 보여준다. 그리고 굴착 심도가 더 깊은 한국지질자원연구원의 지하수내 희토류원소 함량이 한국에너지기술연구원의 지하수내 함량보다 더 낮은 값을 보여준다. 이는 강우가 지하로 흘러들어 가면서, 희토류원소와 대수층 구성암석과의 흡착반응에 의해 심부로 갈수록 함량이 낮아졌을 가능성이 크다고 판단된다. 뿐만 아니라, 강우의 경우, 희토류원소의 W형-테트라드 효과가 매우 현저하게 나타나고, 지하수에서는 M형과 W형의 테트라드 효과가 동시에 존재하는 특성이 강한데, 이는 희토류원소의 수화수 및 화강암 대수층과의 물-암석 반응에 의한 결과인 것으로 사료된다.

• Journal of the Korean Geotechnical Society
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• v.16 no.2
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• pp.23-30
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• 2000

The use of strut-preloading method is gradually increasing in braced excavations in Korea. And it is necessary to analyze the effects of strut preloading on the wall deflection, wall bending moment and strut axial force, etc. In this study, by using the analysis method of beams on elasto-plastic foundations, measured data and calculated results of 2 sites are compared and parametric studies of correlation between preloading and earth retaining structures in sandy soils are carried out in strut preloading application. As results, about 50%~75% of design strut load is effective as preloading force in considering the displacement and member forces of earth retaining structures. And the effective stiffiness of strut should be at least 25% of th ideal value in order to restrain the excessive increase of wall deflection and bending moments. As one of some methods to prevent excessive movements in braced excavation, to preload the strut is confirmed as more effective way than to increase the stiffiness of strut in braced wall, if the excessive axial force of strut due to preloading can be avoided.