• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2005년도 지반공학 공동 학술발표회
• /
• pp.140-153
• /
• 2005

During the tunnel construction the major failure mode can be categorized as: tunnel failure just after the tunnel excavation without support, failure after application of shotcrete and finally failure after setting the concrete lining. The failure mode just after the tunnel excavation without support, can be further classified as : bench failure, crown failure, face failure, full face failure, failure due to weak strata and failure due to overburden. Moreover the failure after application of shotcrete is classified as heading face failure, settlement of shotcrete support, local failure of shotcrete lining and invert shotcrete. To find out the major causes of tunnel collapse, the investigation was done in case of the second phase of Seoul subway construction. The investigation results depicted that the major causes of tunnel collapse were due to the weak layer of rock/fault and sudden influx of ground water from the tunnel crown. While the investigation results of the mountain road tunnels construction have shown that the major causes of tunnel failure were inadequate analysis of tunnel face mapping results, intersection of faults and limestone cavities. In this paper some recent measurement in order to mitigate such tunnel collapse are presented

• 터널과지하공간
• /
• 제15권6호
• /
• pp.400-410
• /
• 2005

토사지반에서 얕은 터널을 굴착하는 경우, 터널 막장부의 파괴 메카니즘이 터널 안정성에 큰 영향을 미친다. 본 논문에서는 일련의 굴진장을 고려한 2차원 종 방향 터널 모형 실험을수행하였다. 그 결과 얕은 터널의 파괴 메카니즘은 굴진장이 길어질수록 파괴모드 1에서 파괴모드 2로 변하는 것을 알 수 있었다. 또한, 모형실험결과와 수치해석을 비교하여 터널에 작용하는 최소 지보압과 진행성 파괴 거동에 대하여 분석하였다.

• Geomechanics and Engineering
• /
• 제11권3호
• /
• pp.421-438
• /
• 2016

Explosions inside transportation tunnels might result in failure of tunnel structures. This study investigated the failure mechanisms of circular cast-iron tunnels in saturated soil subjected to medium internal blast loading. This issue is crucial to tunnel safety as many transportation tunnels run through saturated soils. At the same time blast loading on saturated soils may induce residual excess pore pressure, which may result in soil liquefaction. A series of numerical simulations were carried out using Finite Element program LS-DYNA. The effect of soil liquefaction was simulated by the Federal Highway soil model. It was found that the failure modes of tunnel lining were differed with different levels of blast loading. The damage and failure of the tunnel lining was progressive in nature and they occurred mainly during lining vibration when the main event of blast loading was over. Soil liquefaction may lead to more severe failure of tunnel lining. Soil deformation and soil liquefaction were determined by the coupling effects of lining damage, lining vibration, and blast loading. The damage of tunnel lining was a result of internal blast loading as well as dynamic interaction between tunnel lining and saturated soil, and stress concentration induced by a ventilation shaft connected to the tunnel might result in more severe lining damage.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 1994년도 가을 학술발표회 논문집
• /
• pp.231-234
• /
• 1994

Concentrated stresses due to the tunnel excavation easily cause failure around opening in the soft rock mass layer. Thus, while excavatng tunnel in the soft rock mass layerm it is very important to predict the possibility of failure or yielding zones around tunnel boundary. There are two typical methods to predict these; 1) the analysis of field monioring data and 2) numerical analysis. In this study, it was attempted to describe the time-dependent or progressive rock mass manner due to the continuous failure and fracturing caused by surrounding underground openings using the second method. In order to apply the effects of progressive failure underground, an iterative technique was used with the Hoek and Brown rock mass failure theory. By developing and simulating, three different shapes of twin tunnels, this research simulated and estimated the proper size of critical pillar width between tunnels, distributed stresses on the tunnel sides, and convergences of tunnel crowns. Moreover, results out progressive failure technique based on the Hoek and Brown theory were compared with the results out of Mohr-Coulomb theory.

• Geomechanics and Engineering
• /
• 제24권5호
• /
• pp.457-470
• /
• 2021

In this study, the pull-out behavior of a tunnel-type anchorage for suspension bridges was investigated using experimental tests and image processing analyses. The study focused on evaluating the initial failure behavior and failure mode of the tunnel-type anchorage. In order to evaluate the failure mode of tunnel-type anchorage, a series of scaled model tests were conducted based on the prototype anchorage of the Ulsan Grand Bridge. In the model tests, the anchorage body and surrounding rocks were fabricated using a gypsum mixture. The pull-out behavior was investigated under plane strain conditions. The results of the model tests demonstrate that the tunnel-type anchorage underwent a wedge-shaped failure. In addition, the failure mode changed according to the differences in the physical properties of the surrounding rock and the anchorage body and the size of the anchor plate. The size of the anchor plate was found to be an important parameter that determines the failure mode. However, the difference in physical properties between the surrounding rock and the anchorage body did not affect its size. In addition, this study analyzed the initial failure behavior of the tunnel-type anchorage through image analysis and confirmed that the failure was sequentially transferred from the inside of the tunnel to the surrounding rock according to the image analysis. The reasonable failure mode for the design of the tunnel-type anchorage should be wedge-type rather than pull-out type.

• Geomechanics and Engineering
• /
• 제17권1호
• /
• pp.97-107
• /
• 2019

Based on the results of Han et al. (2016), in the failure zone ahead of the tunnel face it can be obviously identified that a shear failure band occurs in the lower part and a pressure arch happens at the upper part, which was often neglected in analyzing the face stability of shield tunnel. In order to better describe the collapse failure feature of the tunnel face, a new improved failure mechanism is proposed to evaluate the face stability of shield tunnel excavated in layered soils in the framework of limit analysis by using spatial discretization technique and linear interpolation method in this study. The developed failure mechanism is composed of two parts: i) the rotational failure mechanism denoting the shear failure band and ii) a uniformly distributed force denoting the pressure arch effect. Followed by the comparison between the results of critical face pressures provided by the developed model and those by the existing works, which indicates that the new developed failure mechanism provides comparatively reasonable results.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 1999년도 봄 학술발표회 논문집
• /
• pp.309-314
• /
• 1999

In this paper, an application of finite element procedure fur tunnel failure analysis has been studied. The numerical model is applied to the simulation of a series of plane strain laboratory tests on the small scale model of a shallow tunnel. By comparing experimental and numerical results some conclusions are drawn on the effectiveness of the numerical approach. The findings from these numerical experiments show relative differences in the pattern of failure behaviour for shallow tunnels.

• Geomechanics and Engineering
• /
• 제11권6호
• /
• pp.867-877
• /
• 2016

Collapse shape of tunnel roof in layered Hoek-Brown rock media is investigated within the framework of upper bound theorem. The traditional collapse mechanism for homogeneous stratum is no longer suitable for the present analysis of roof stability, and it would be necessary to propose a curve failure mode to describe the velocity discontinuity surface in layered media. What is discussed in the paper is that the failure mechanism of tunnel roofs, consisting of two different functions, is proposed for layered rock media. Then it is employed to investigate the impending roof failure. Based on the nonlinear Hoek-Brown failure criterion, the collapse volume of roof blocks are derived with the upper bound theorem and variational principle. Numerical calculations and parametric analysis are carried out to illustrate the effects of different parameters on the shape of failure mechanism, which is of overriding significance to the stability analysis of tunnel roof in layered rock media.

• 한국터널지하공간학회 논문집
• /
• 제2권3호
• /
• pp.13-24
• /
• 2000

본 논문에서는 고속도로터널의 붕락형태와 원인분석, 보강방법에 대하여 다루었다. 고속도로터널의 붕락형태를 분석해 보면 3가지 유형으로 분류된다. 지반풍화로 인해 터널붕락이 지표면까지 함몰된 경우 35%, 불리한 암반절리로 인한 터널내 국부적인 쐐기형 암반블럭 붕락의 경우 50%, 터널굴진방향과 미끄럼면의 교차로 인해 터널내 침하가 발생한 경우 15%의 비율로 조사되었고 터널붕락이 발생된 위치는 입출구 40m 이내와 입출구와 인접한 계곡부에서 85%, 비상주차대과 본선접속부에서 15% 발생되었다. 고속도로터널에서 발생한 붕락을 파괴개념으로 분석하면 활동파괴가 83%이상을 차지하는 것으로 분석되었다.

• 한국지반환경공학회 논문집
• /
• 제10권7호
• /
• pp.167-177
• /
• 2009

본 연구에서는 터널 붕괴붕락의 유형 중 국부 암괴하중에 의한 숏크리트 라이닝의 파괴특성을 유한요소 해석을 통해 고찰하였다. 우선, 기존 터널 라이닝 파괴특성을 보다 체계적으로 파악하기 위하여 암반과 숏크리트체 강성비와 부착강도의 특성에 변화를 주어 총 9가지의 조건을 설정하였다. 각 조건에 대한 블록낙하실험(falling block test)환경에서 수치해석을 수행하여 파괴양상을 고찰해 보고 기존의 이론적 파괴 메카니즘과 비교/평가하여 보았다. 결과적으로, 기존 문헌에서 언급된 4가지 파괴모드(점착파괴(adhesive failure), 직접전단파괴(direct shear failure), 휨인장파괴(flexural failure) 및 휨전단파괴(punching shear failure))가 모두 구현되긴 하였으나, 점착파괴는 항상 타 파괴유형과 동반되어 나타나며, 별도의 파괴유형으로 분류하는 것은 부적절하다고 판단되었다. 또한 기존 관련 연구에서는 터널공학의 주요개념인 아칭효과에 대해 고려치 않고 단순보 개념하에서 라이닝의 파괴특성을 고찰하였으며, 굴착에 의해 부가되는 라이닝의 초기 축력을 고려치 않고 있다. 이에 대해 터널특성에 부합된 경계조건들을 고려하여 신규 라이닝 파괴모드를 재 고찰하였으며, 곡률이 있는 터널 라이닝조건에서는 크게 두 가지 파괴유형으로 분류할 수 있는 것으로 파악되었다.