• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 가을 학술발표회 논문집
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• pp.201-208
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• 1999

The NATM(New Austrian Tunnelling Method) has been used for tunnelling since 1980's. But Collapses of tunnel under construction take place frequently, especially at urban areas because of adjacent buildings, underground conduits and traffic loads. This paper is a case study on the reinforcement method of subway tunnel at urban areas. In this study, ground inspection, geological investigation, laboratory test and numerical analysis by means of FDM program were carried out. The tunnel excavation was stopped because of over excessive brake of tunnel crown and shotcrete was installed to prevent deformation of adjacent ground as the temporary method. From the result of field survey and geological investigation, it is found that the soft weathered soil was distributed to the ground of tunnel invert unlike original investigation. The results of the analysis and the study show that the SGR(Space Grouting Rocket) method and Umbrella method can be applied for the stability of tunnel excavation and in addition the reinforcement of concrete lining is required for long-term stability of tunnel.

• 한국지반공학회지:지반
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• 제14권2호
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• pp.107-126
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• 1998

터널굴착으로 발생되는 지반침하는 지상구조물의 변형을 유발할 수도 있으므로 터널굴착 전에 지상구조물의 안전성 평가가 요구된다. 이러한 변형에 대한 구조물의 안전성을 평가하기 위하여 본 연구에서는 터널현장의 지반침하를 예측하고, 이를 기반으로 지상구조물의 안정성 평가를 수행하는 전문가 시스템 NESASS(Neural Network Expert System for Adjacent Structure Safety analysis)를 개발하였다. NESASS는 인공신경망을 이용, 터널현장의 지반침하 계측자료로 작성된 데이터베이스 자료를 학습자료로 하여 학습을 수행하고, 이를 기반으로 터널현장의 지반침하 트라프를 추론한다. 또한 일반구조물의 안전성을 평가하는데 이용되고 있는 인자, 즉 각변형(angular distortion)과 처징비 (deflection ratio) 등을 이용하여 지상건물의 안전성을 평가함과 아울러 Dulacska의 균열평가 모델 을 이용하여 건물의 균열양상을 예측한다. 본 연구에서는 서울지하철 현장을 대상으로 113개 계측측선의 지반침하 계측자료를 수집 정리하고 지반침하의 주 영향인자들을 선정하여. 이들을 데이터베이스화하였다. 그리고 인공신경망 구조에 관련된 매개변수 연구를 수행하여 구축된 데이터베이스에 대한 최적 인공신경망 모델을 선정하였다. 또한 현장자료와의 비교를 통하여 NESASS의 지반침하 예측능력을 조사하고, 현장자료를 이용하여 지상구조물에 대한 안전성 평가의 신뢰성을 평가함으로써 NESASS의 실무 적용성을 확인 하였다.

• Geomechanics and Engineering
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• 제12권2호
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• pp.185-195
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• 2017

With the rapid development of urban underground traffic, the study of soil deformation induced by subway tunnel construction and its settlement prediction are gradually of general concern in engineering circles. The law of soil displacement caused by shield tunnel construction of adjacent buildings is analyzed in this paper. The author holds that ground surface settlement based on the Gauss curve or Peck formula induced by tunnel excavation of adjacent buildings is not reasonable. Integrating existing research accomplishments, the paper proposed that surface settlement presents cork distribution curve characters, skewed distribution curve characteristics and normal distribution curve characteristics when the tunnel is respectively under buildings, within the scope of the disturbance and outside the scope of the disturbance. Calculation formulas and parameters on cork distribution curve and skewed distribution curve were put forward. The numerical simulation, experimental comparison and model test analysis show that it is reasonable for surface settlement to present cork distribution curve characters, skewed distribution curve characteristics and normal distribution curve characteristics within a certain range. The research findings can be used to make effective prediction of ground surface settlement caused by tunnel construction of adjacent buildings, and to provide theoretical guidance for the design and shield tunnelling.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.1496-1503
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• 2005

The study on the lateral earth pressure is briskly preformed for various conditions such as type of retaining walls, ground condition, and type of supporting systems. It is not simple to determine the distribution of lateral earth pressure accurately, however, because the lateral earth pressure is affected by various factors. This study is performed to analyze the behavior of earth retaining walls for new excavation contacting with existing excavation by comparing with the site measuring values before and after new excavation. On the base of observation, the distribution of strut axial forces is similar to that of ganeral earth retaining walls, but strut axial forces is increased by removal of existing earth anchors. When new excavation is performed contacting with existing excavation, the axial force of strut is decreased because of soil exclusion in the behind walls, but that force is increased after new exeavation. The analysis result show that the installation of strut in middle part makes a effect to not only 1 adjacent strut, but 3-5 adjacent struts. Also during new excavation strut axial forces is decreased by relaxation of total earth retaining wall system.

• Geomechanics and Engineering
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• 제19권4호
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• pp.315-327
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• 2019

Deep excavations for development of subway systems in metropolitan regions surrounded by adjacent buildings is an important geotechnical problem, especialy in Tabriz city, where is mostly composed of young alluvial soils and weak marly layers. This study analyzes the wall displacement and ground surface settlement due to deep excavation in the Tabriz marls using two dimensional finite element method. The excavation of the station L2-S17 was selected as a case study for the modelling. The excavation is supported by the concrete diaphragm wall and one row of steel struts. The analyses investigate the effects of wall stiffness and excavation width on the excavation-induced deformations. The geotechnical parameters were selected based on the results of field and laboratory tests. The results indicate that the wall deflection and ground surface settlement increase with increasing excavation depth and width. The change in maximum wall deflection and ground settlement with considerable increase in wall stiffness is marginal, however the lower wall stiffness produces the larger wall and ground displacements. The maximum wall deflections induced by the excavation with a width of 8.2 m are 102.3, 69.4 and 44.3 mm, respectively for flexible, medium and stiff walls. The ratio of maximum ground settlement to maximum lateral wall deflection approaches to 1 with increasing wall stiffness. It was found that the wall stiffness affects the settlement influence zone. An increase in the wall stiffness results in a decrease in the settlements, an extension in the settlement influence zones and occurrence of the maximum settlements at a larger distance from the wall. The maximum of settlement for the excavation with a width of 14.7 m occurred at 6.1, 9.1 and 24.2 m away from the wall, respectively, for flexible, medium and stiff walls.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.268-275
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• 2006

Excavation works of cylindrical shafts and tunnels for the construction of a variety of infrastructures have been frequently going on in the urban areas. When ground excavations of cylindrical shafts and shallow tunnels proceed in the ground condition of high water level and silt particle component, ground water drawdown involving soil particle migration causes loosening of ground around tunnels and shafts, causes settlement and deformation of ground. Damages due to ground sinking and differential settlement can occur in the adjacent ground and structures. The extent and possibility of damage relevant to ground water drawdown and soil particle migration can't be so precisely expected in advance that we will face terrible damages in case of minor carefulness. This paper introduces two examples of construction management where using incremental deformation graph of inclinometer, we noticed the possibility of soil migration due to ground water drawdown in the excavation process of vertical shaft and shallow tunnel, analysed a series of measurement data in coupled connection, properly prepared countermeasures, so came into safe and successful completion of excavation work without terrible damages. 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.

• Geomechanics and Engineering
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• 제33권2호
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• pp.195-202
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• 2023

In this study, the ground settlement in backside of retaining wall and the behavior of the retaining wall were analyzed according to the method of groundwater drawdown due to excavation by using two-dimensional(2D) finite element analysis. Numerical analysis was performed by applying 1) fixed groundwater level, 2) constant groundwater drawdown, and 3) transient groundwater drawdown. In addition, the behavior of the retaining wall according to the initial groundwater level, ground conditions, and surcharge pressure in backside of retaining wall was evaluated. Based on the numerical analysis results, it was confirmed that when the groundwater level is at 0.1H from the ground surface (H: Excavation soil height), the wall displacement and ground settlement are not affected by the method of groundwater drawdown, regardless of soil conditions (dense or loose) and surcharge pressure. On the other hand, when the groundwater level is at 0.5H from the ground surface, the method of groundwater drawdown was found to have a significant effect on wall displacement and ground settlement. In this case, the difference in ground settlement presents by up to 4 times depending on the method of groundwater drawdown, and the surcharge load could increase the ground settlement by up to 1.5 times.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2008년도 추계학술대회 논문집
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• pp.891-896
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• 2008

절리암반에서 기존 터널에 근접하여 사면을 굴착하면 터널의 거동은 절리와 사면의 경사에 따라 영향을 받는다. 본 연구에서는 실대형 실험을 실시하여 터널에 근접하여 사면을 굴착시 사면각도와 절리각도에 따른 터널의 내공변위, 터널 라이닝의 부재력 등의 특성을 분석하였다. 분석결과 절리각도와 사면각도가 크면 클수록, 터널 내공변위와 모멘트는 커지는 경향이 있으며, 절리각도와 사면각도에 따라 지중변위 크기와 방향이 다르게 나타나고 있어 향후 사면보강에 있어 효율적 방안제시가 가능할 것이다.

• 터널과지하공간
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• 제20권5호
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• pp.369-377
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• 2010

근접굴착 시 기존터널의 안정성을 확보하는 방안을 연구하였다. 흙막이벽체의 수평변위가 생기지 않도록 선행하중을 가하였다. 이를 위해 선행하중을 가하지 않은 경우와 선행하중을 가한 경우에 대해 실대형 시험을 실시하였다. 지표면에 건물하중이 없는 경우와 건물하중이 있는 경우(0 m, 1D, 2D)에 대하여 각각 실험을 실시하였다. 그 결과 선행하중을 적용시켜 흙막이벽체의 변위를 억제시켰을때 벽체배면에 있는 기존터널의 안정성이 크게 향상되는 것을 확인할 수 있었다. 본 논문에서는 흙막이벽체와 기존터널의 거동에 대하여 연구하였다. 기존터널은 지름 12 m를 사용하였으며 1:10의 축척으로 2.0 m(폭) ${\times}$ 6 m(높이) ${\times}$ 4.0 m(길이)의 크기를 가진 대형토조에서 실험을 수행하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 봄 학술발표회 논문집
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• pp.395-402
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• 2000

Recently, the deep excavations have been peformed to utilize the under ground space. As the ground excavation is deeper, the damage of the adjacent structure and the ground occurs frequently. The analysis of the retaining structures is necessary to the safety of the excavation works. There are many methods such as elasto-plastic, FEM, and FDM to analyze the displacement of the retaining structure. The elasto-plastic method is generally used in practice. In this thesis, GEBA-1 program by the Nakamura-Nakajawa elasto-plastic method was developed. The program for Windows was used the Visual Basic 6.0, and the Main of the program consists of three subroutines, SUB1, SUB2, and SUB3. The lateral displacement of the wall was analyzed by the developed program GEBA-1, SUNEX, and EXCAD, and compared with the measured displacement by the Inclinometer(at three excavation work sites). The excavation method of each site is braced retaining wall using H-pile. Each excavation depth is 14m, 14m, or 8.2m. The results of the analyses are the followings ① In the multi-layer soil, the lateral displacement by the GEBA-1 and EXCAD which is considering the distribution of the strut load is equal to the measured displacement. Elasto-plasto programs can't consider the change of the ground water in clay. Therefore, the analysis displacement was expected only 20% of the measured wall displacement. ③ At the final excavation step, the maximum lateral displacement of analysis and field occurred 7∼18m at the 85∼92% of the excavation depth. ④ The maximum lateral displacement in clay, as 50mm, occurred on the ground surface.