• Geomechanics and Engineering
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• 제35권5호
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• pp.525-538
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• 2023

The development of a city is closely linked to the construction and operation of its subway system. However, constructing a new subway tunnel under an existing station is an extremely complex task, and the deformation characteristics and mechanical behavior of the new subway tunnel during the excavation process can greatly impact the normal operation of the existing station. Although the previous studies about the case of underpass engineering have been carried out, there is limited research on the condition of a newly-built subway tunnel that closely undercrossing an existing station with zero distance between them. Therefore, this study analyzes the deformation law and mechanical behavior characteristics of the preliminary lining of the underpass tunnel during the excavation process based on the real engineering case of Chengdu Metro Line 8. This study also makes an in-depth comparison of the influence of different excavation methods on this issue. Finally, the accuracy of numerical simulation is verified by comparing it with on-site result. The results indicate that the maximum bending moment mainly occurs at the floor slab of the preliminary lining, while that of the ceiling is small. The stress state at the ceiling position is less affected by the construction process of the pilot tunnel. Compared to the all-in-one excavation method, although the process of partial excavation method is more complicated, the deformation of preliminary lining caused by it is basically less than the upper limit value of the standard, while that of the all-in-one excavation method is beyond standard requirements.

• 한국지반공학회논문집
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• 제30권2호
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• pp.43-52
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• 2014

본 논문은 암반지층에 설치되는 굴착벽체에 발생하는 토압에 대한 단계별 굴착깊이의 영향을 조사한 것이다. 암반지층에서 발생하는 문제들을 다루기 위해 개별요소법에 근거한 수치해석적 매개변수해석을 수행하였다. 수치해석은 매개변수로서 단계별 굴착깊이, 암반종류 및 절리조건(절리면의 전단강도 및 절리경사각)을 고려하였다. 암반지층에서 발생된 토압과 토사지반에서의 경험토압인 Peck토압이 서로 비교되었다. 비교결과 암반지층에서 발생된 토압은 암반의 종류 및 절리조건에 따라서 크게 영향을 받았으며, 단계별 굴착깊이의 영향은 암반상태가 나빠질수록 증가하는 것으로 나타났다. 더불어, 암반지층에 설치된 굴착벽체에 발생하는 토압은 토사지반에 대한 Peck의 경험토압과는 크게 다를 수 있다는 결과를 얻었다.

• Geomechanics and Engineering
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• 제24권4호
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• pp.323-335
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• 2021

This paper aims to estimate the range of the excavation damaged zone (EDZ) formation caused by the tunnel boring machine (TBM) advancement through dynamic three-dimensional large deformation finite element analysis. Large deformation analysis based on Coupled Eulerian-Lagrangian (CEL) analysis is used to accurately simulate the behavior during TBM excavation. The analysis model is verified based on numerous test results reported in the literature. The range of the formed EDZ will be suggested as a boundary under various conditions - different tunnel diameter, tunnel depth, and rock type. Moreover, evaluation of the integrity of the tunnel structure during excavation has been carried out. Based on the numerical results, the apparent boundary of the EDZ is shown to within the range of 0.7D (D: tunnel diameter) around the excavation surface. Through series of numerical computation, it is clear that for the rock of with higher rock mass rating (RMR) grade (close to 1st grade), the EDZ around the tunnel tends to increase. The size of the EDZ is found to be direct proportional to the tunnel diameter, whereas the depth of the tunnel is inversely proportional to the magnitude of the EDZ. However, the relationship between the formation of the EDZ and the stability of the tunnel was not found to be consistent. In case where the TBM excavation is carried out in hard rock or rock under high confinement (excavation under greater depth), large range of the EDZ may be formed, but less strain occurs along the excavation surface during excavation and is found to be more stable.

• 한국지반환경공학회 논문집
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• 제18권2호
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• pp.5-19
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• 2017

국내 건축물 시공을 위한 지하 굴착은 안정성, 경제성 및 굴착 주변 여건 등을 고려하여 재래식 버팀대 공법(Strut, Ground Anchor)에서 점차 Top-Down 공법을 개량한 내부 영구 지지체 공법으로 변화하고 있다. 본 연구에서는 국내에서 범용적으로 사용되고 Top-Down 공법, New Top-Down 공법, S.P.S 공법, S.T.D 공법 및 B.R.D 공법 등 내부 영구 지지체 공법 현장을 선정하여 재래식 버팀대 공법과 공사비 및 공기를 비교 분석하였다. 또한 공사 중 흙막이 벽체의 계측 자료를 분석하여 흙막이 벽체의 안정성을 확인하였다. 그 결과 깊은 굴착 및 기반암층이 지표면으로부터 가까운 경우 영구 지지체 공법이 재래식 버팀대 공법보다 경제성과 시공성이 우수함을 알 수 있었다

• 한국터널지하공간학회 논문집
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• 제7권4호
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• pp.335-341
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• 2005

대단변 NATM터널에서 지반자체로 막장의 안정을 유지하기 위해 분할굴착공법을 사용한다. 분할굴착을 해야 한다면 더 나은 응력 상태를 유지할 수 있는 분할굴착공법을 강구해야할 것이다. 따라서 본 연구에서는 터널의 단면분할 굴착공법 중 CD굴착 (중벽분할굴착)공법에서 굴착순서에 따른 응력분포를 수치해석적인 방법을 이용하여 검토하고, 막장주변의 응력집중을 최소로 하는 최적의 막장 이격거리와 굴착순서를 도출하였다. 해석에 사용한 프로그램은 국내에서 상용화되고 있는 3차원 연속체 해석 프로그램인 FLAC-3D Ver 2.1을 사용하였고, 암반등급 3과 5에 대해 막장거리 2m, 4m, 6m, ${\cdots}$, 20m, 40m를 적용하여 안정성 검토를 행하였다.

• 한국지반공학회논문집
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• 제21권10호
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• pp.99-112
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• 2005

도심지에서의 지반굴착은 배면지반의 변위와 그에 따르는 건물의 손상을 유발시킨다. 굴착에 의한 지반변위의 예측과 굴착면 주변에 위치한 건물의 손상 위험도 평가는 설계단계에서 필수적인 요소이다. 본 논문에서는 기존의 굴착에 의한 지반변위 예측기법인 Peck의 방법과 Bowles의 방법을 조합하여 지보굴착에 따르는 배면지반 변위예측방법을 제안하였다. 또한, 배면지반의 Green-field 뒤틈각과 수평변형률을 이용한 인접건물 손상위험도 평가기법을 제안하였다. 이 기법은 싱가폴에서 시공중인 대규모 지반굴착공사의 설계에 성공적으로 적용되었다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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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.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2003년도 봄 학술발표회 논문집
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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.

• 터널과지하공간
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• 제7권1호
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• pp.1-12
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• 1997

Engineering rock mass classification is extensively used to determine the reasonable support system throughout the tunneling process in the field. Selection of support system based on the results of engineering rock mass classification is simple and straight-forward. However, this method cannot consider the effect of in-situ stresses, mechanical properties of support material, and support installation time on the behavior or rock-support system To handle the various conditions encountered in the underground excavation sites rock-support system. To handle the various conditions encountered in th eunderground excavation sites rock-support interaction program has been developed. This program can analyze the interaction between rock mass and support materials and also can simulate the tunnel excavation-support insstallation process by controlling the support installation time and the stiffness of support system. Practical applicability of this program was verfied by comparing the results of support design to those from rock mass classification for virtual underground excavation at the drilling site KD-06 in Geoje island.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1992년도 봄 학술발표회 논문집
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• pp.118-125
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• 1992

The ground deformation due to the tunnel excavation is dependent on various factors such as ground condition, geometry of the tunnel, excavation method, installation of support members, construction condition of each excavation stage, etc. And the distance from the facing effects significantly the stress conditions of the supported and unsupported ground due to the 3-dimensional structural nature of the excavated tunnel. The concept of ground characteristic line has been applied to properly consider the loading condition given by staged tunnel excavation so that the imaginary supporting pressure is applied against the surface of excavated ground. Discussions on the results of the performed finite element analysis were mainly made with respect to the ground settlement, tunnel displacement, earth pressure, stress mobilized in supporting members.