• Tunnel and Underground Space
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• v.21 no.5
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• pp.394-405
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• 2011

In this paper, we applied coupled non-isothermal, multiphase fluid flow and geomechanical numerical modeling using TOUGH-FLAC coupled analysis to study the complex thermodynamic and geomechanical performance of underground lined rock caverns (LRC) for compressed air energy storage (CAES). Mechanical stress in concrete linings as well as pressure and temperature within a storage cavern were examined during initial and long-term operation of the storage cavern for CAES. Our geomechanical analysis showed that effective stresses could decrease due to air penetration pressure, and tangential tensile stress could develop in the linings as a result of the air pressure exerted on the inner surface of the lining, which would result in tensile fracturing. According to the simulation in which the tensile tangential stresses resulted in radial cracks, increment of linings' permeability and air leakage though the linings, tensile fracturing occurred at the top and at the side wall of the cavern, and the permeability could increase to $5.0{\times}10^{-13}m^2$ from initially prescribed $10{\times}10^{-20}m^2$. However, this air leakage was minor (about 0.02% of the daily air injection rate) and did not significantly impact the overall storage pressure that was kept constant thanks to sufficiently air tight surrounding rocks, which supports the validity of the concrete-lined underground caverns for CAES.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.4
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• pp.397-404
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• 2008

Excessive amount of groundwater flowed into tunnel, while constructing Incheon international airport railway. Tunnel passes under subway line no. 2 with only 1.76 m below. To protect the existing structure, TRcM excavation method was applied. As station and construction shaft are already constructed, which are located back and forth of TRcM section, 86.4 ton per day of groundwater inflow is against expectation. To identify mechanism of excessive water inflow, hydraulic back analyses were performed. Then, hydro-mechanical coupled analysis were also performed with the hydrogeologic parameters identified, whose results are investigated for checking the stability of adjacent structures to the tunnel under construction. And a number of mechanical analyses were also performed to check the hydro-mechanical coupling effect. The result from the mechanical analysis shows that subsidence and tunnel ceiling displacement will be 0.85 mm and 1.32 mm. The result of hydro-mechanical couple analysis shows that subsidence and maximum tunnel ceiling displacement will be 1.2 mm and 1.72 mm. Additional displacements caused by groundwater draw down were identified, however, displacement is minute.

• Tunnel and Underground Space
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• v.33 no.1
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• pp.10-28
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• 2023

Long-term shear behavior of the rock discontinuities should be analyzed and its stability should be evaluated to ensure the long-term stability of a high-level radioactive waste disposal repository. The long-term shear behavior of the discontinuities can be modeled with creep and RSF models. The shear creep test, velocity step test, and slide-hold-slide test can be performed to determine their model parameters or analyze the shear behavior by experiments under various conditions. Testing apparatuses for direct shear, triaxial compression, and biaxial shear were mainly used and improved to reproduce the thermo-hydro-mechanical conditions of local bedrock, and it was confirmed that the shear behavior could vary. In order to design a high-level radioactive waste disposal site in Korea, the long-term behavior of rock discontinuities should be investigated in consideration of rock types, thermo-hydro-mechanical conditions, metamorphism, and restoration of shear resistance.

• Tunnel and Underground Space
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• v.25 no.1
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• pp.68-75
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• 2015

Rock mass includes such discontinuities as fault, joint, bedding, crack, schistosity, cleavage. The rock mass behavior, therefore, is influenced by the discontinuity behavior. In this study, a stability and deformation analysis method considering discontinuities in rock mass is proposed, and then applied to the rock collapse disaster site. As the method, the stability analysis by the stereographic projection method was carried out in an actual site, the deformation analysis program by the finite element method including the joint element was developed, and performed. To demonstrate the applicability of this developed stability and deformation analysis method considering discontinuities in rock mass, the analysis results are examined and compared with the failure behavior at the rock mass.

• Tunnel and Underground Space
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• v.14 no.2
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• pp.154-166
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• 2004

A numerical stability analysis was conducted on the large oil storage caverns excavated in a rock mass under high initial horizonal stress. The behaviors of the surrounding rock mass, rockbolts, and shotcrete were analyzedr and stability of the support members were assessed. For a proper support system design, the effect of the modelling technique, cavern shape and rockbolt length on the stability of the cavern was investigated. Results show that installation timing of supports and the change in cavern shape due to stepwise excavation affect the stress induced in support members. Also found was desperate need for a numerical technique which can properly reflect the behavior of the steel fiber reinforced shotcrete.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 1996.03a
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• pp.83-94
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• 1996

지하 암반구조물의 안정적 설계 및 효율적 시공을 위해서는 공동설계 및 거동예측에 필요한 지질공학적 자료의 획득이 가장 중요하다. 현재 절리 등의 불연속면을 포함한 현장암반의 역학적 특성계수 및 응력 상태에 대한 조사기법들이 다양하게 개발되어 신뢰성 있는 분석결과를 제공하고 있다. (중략)

• Journal of the Korean Geosynthetics Society
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• v.18 no.4
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• pp.287-297
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• 2019

In this study, a series of finite element numerical analyzes were performed considering the pavement thickness and traffic load for the purpose of stability analysis on the cavity ground. In order to verify the validity of this numerical method, the previous numerical analysis was used to simulate the mechanical behavior of cavity ground, and the results were compared and analyzed. Also, from the numerical results, it was possible to confirm the dynamic behavior of the ground by confirming the change of ground void ratio, surface settlement, and shear stress, and using the relationship between stress ratio, non-destructive depth and surface settlement, the safety of the was analyzed. As a result, as the pavement thickness decreased and the traffic load increased, the non-destructive depth and the overall stability of the ground decreased with the increase of surface settlement.

• The Journal of Engineering Geology
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• v.18 no.3
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• pp.339-347
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• 2008

This study was carried out to assess quantitatively the safety of a tunnel by using critical strains in the ground. Critical strain is a new material property of the ground. It can be applied as deformation limits in the ground due to excavation using the measured displacement at the tunnel construction site. To achieve this purpose, the critical strain concept was reviewed and applied to assess the tunnel safety. First of all, the calculated excavation displacements of a circular tunnel by commercial programs were investigated and inputted into a feedback analysis module to calculate strains in the ground. Then the safety of tunnels was evaluated based on the critical strain concept. Subsequently the measured displacements obtained in the field are utilized practically to assess the safety of tunnels using the critical strain concept. Through this study, it was confirmed that the critical strain concept is useful to assess the safety of tunnels quantitatively.

• Tunnel and Underground Space
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• v.29 no.1
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• pp.64-74
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• 2019

Behavior of a rock block consisting of rock joints during excavation of an underground opening is an important factor for the mechanical stability of the opening. In this study, the behavior of a rock block under different geostatic stress and joint property conditions was analyzed quantitatively. The behavior of the rock block analyzed by 3DEC numerical analysis was compared with that of the theoretical calculation, and the error between the theoretical value and the numerical analysis result was analyzed under various geostatic stress and joint property conditions. The result of the stability analysis of a rock block showed less than 5% of error with numerical simulation result, which verified the applicability of the purposed analytic solution.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.47.2-47.2
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• 2010

빗물을 노상 침투시키는 투수성포장은 물순환 보전과 차량 주행 안전성 확보와 같은 효과를 기대할 수 있다. 지금까지 보도나 주차장 같이 비교적 교통조건이 열악하지 않은 구간에 적용되고 있지만 우수 침투로 인해 노상이 연약화 될 것을 우려하여 현재까지 차도에 적용하지 못하고 있으며 설계 방법 또한 정립되어 있지 못한 실정이다. 본 연구에서는 투수성포장의 포장단면을 설계하기 위한 방안으로 단지내 포장을 투수성포장으로 설계할 경 물의 침투로 인해 노상의 지지력이 약화 된다고 가정하고 노상 지지력의 약화에 따른 포장층의 역학적 거동 특성을 유한요소 해석을 통하여 분석하여 구조적 안정성을 확보할 수 있는 포장두께를 분석하였다. 또한 설계 개념에서 노상의 지지력 저하에 따른 포장두께의 할증방안과 할증두께를 분석하였다.