• Title/Summary/Keyword: 지하공동

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지하공동 모델의 전기비저항 특성에 관한 실험적 연구

  • Park, Gap-Jin;Kim, Hyeon-Su;Kim, Hyeon-Seung;Song, Yeong-Su
    • 한국지구물리탐사학회:학술대회논문집
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    • 2009.10a
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    • pp.93-98
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    • 2009
  • Comprehension of physical properties distribution of underground cavity must be made primarily to show the clear image of the state of the cavity. A physical scale model experiment is executed assuming that underground cavity in filled with air or water of different ratio. The state of cavity wall is considered wet. Cavity model is made of agar. As a experimental result, even if the cavity wall is wet, high air and water ratio cavity shows high anomaly.

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Rock Mechanics at Great Depth (대심도에서의 암반역학적 문제)

  • Park, Eui-Seob;SunWoo, Chun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2009.09a
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    • pp.573-583
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    • 2009
  • 심부암반에 건설되는 지하공동의 형상과 규모는 지질구조, 암반조건 및 건설방법 (굴착, 보 강)에 따라 변화될 수 있으므로 이전에 사용해오던 공동의 크기와 형상을 그대로 답습하는 관행을 탈피하고 지하공동이 갖고 있는 특수한 용도와 목적에 따라 대형화, 심부화 추세로 가고 있는 지하공동의 설계개념을 수립하여야 한다.

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The Stability of Strip Footing above Underground Cavity (지하공동에 인접한 연속기초의 안정성)

  • Oh, Se-Wook;Lee, Bong-Jik;Bae, Woo-Seok
    • Journal of the Korean GEO-environmental Society
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    • v.7 no.3
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    • pp.69-76
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    • 2006
  • In this study, an experimental study in sand ground that was prepared by raining method was performed for modeling the bearing capacity behavior of strip footing above a cavity. The critical range of bearing capacity of the strip footing affected by underground cavity was investigated by comparing results between experiment and theory. The size of the critical region depends on several factors such as footing shape, soil property, cavity size and cavity shape. The ultimate bearing capacity was more influenced by the depth of the underground cavity than the eccentricity of the underground. In addition, an underground cavity influences on not only the decrease of the bearing capacity, but also the differential settlement of a strip footing.

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A numerical study on the characteristics of small underground cavities in the surrounding old water supply and sewer pipeline (노후 상하수관 주변지반의 소규모 지하공동 형상 특성을 고려한 수치해석에 관한 연구)

  • An, Joon-Sang;Kang, Kyung-Nam;Song, Ki-Il;Kim, Byung-Chan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.2
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    • pp.287-303
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    • 2018
  • In recent years, the occurrence of ground subsidence phenomenon is frequent in Korea. The Korean government has enacted a special law on underground safety and the law will be enforced from January 1, 2018. Under this new law, underground excavation should be assessed for underground safety impacts. After excavation construction, periodic geophysical surveys should be conducted to investigate the occurrence of underground cavities. When underground cavities were discovered, the underground safety was assessed through numerical analysis. However, it is controversial because the method of numerical modeling the discovered underground cavity is due to be established. In this study, the effect of the depth of the underground cavity from the shape of the underground cavity to the underground cavity was studied using a continuum analysis program. In this study, a method to reflect the shape of the underground cavity to the numerical modeling is presented. The relationship between the shape and depth of the underground cavity, and the factor of safety calculated by the shear strength reduction method (SSR) is presented. The results of this study are expected to form the basic data on underground safety impact assessment.

A numerical study on the influence of small underground cavities for estimation of slope safety factor (소규모 지하공동이 사면안전율 산정에 미치는 영향에 관한 수치해석 연구)

  • An, Joon-Sang;Kang, Kyung-Nam;Song, Ki-Il;Kim, Byung-Chan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.21 no.5
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    • pp.621-640
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    • 2019
  • Quantitative stability assessment of underground cavities can be presented as a factor of safety based on the Shear Strength Reduction Method (SSRM). Also, SSRM is one of the stability evaluation methods commonly used in slope stability analysis. However, there is a lack of research that considers the relationship between the probability of occurrence of cavities in the ground and the potential failure surface of the slope at the same time. In this study, the effect of small underground cavities on the failure behavior of the slope was analyzed by using SSRM. Considering some of the glaciology studies, there is a case that suggests that there is a cavity effect inside the glacier in the condition that the glacier slides. In this study, the stability evaluation of underground cavities and slope stability analysis, where SSRM is used in geotechnical engineering field, was carried out considering simultaneous conditions. The slope stability analysis according to the shape and position change of underground cavities which are likely to occur in the lower part of a mountain road was analyzed by using SSRM in FLAC3D software and the influence of underground cavities on the slope factor of safety was confirmed. If there are underground cavities near slope potential failure surface, it will affect the calculation of a factor of safety. The results of this study are expected to be basic data on slope stability analysis with small underground cavities.

A comparative study on stability evaluation of caverns by 2D continuum analysis in terms of shape factor (2차원 연속체 해석에 의한 지하공동 형상비별 안정성 평가 비교)

  • You, Kwang-Ho;Jung, Ji-Sung
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.10 no.2
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    • pp.193-205
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    • 2008
  • The construction of underground structures such as oil and food storage caverns are recently increasing in our country. The stability of those underground caverns are greatly influenced by their shape and size. In this study therefore, the effect that the shape of an underground cavern have on its stability were analyzed in terms of safety factor. To this end, caverns with 5 different shapes were investigated and sensitivity analyses were performed based on rock class, overburden, and lateral earth pressure coefficient. The proper amount of shotcrete and rockbolt as supports of a cavern was also assumed based on the shape and site of the cavern and rock conditions. This study is expected to be helpful in designing and evaluating the stability of caverns in future.

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The effect of the shape factor of an underground cavern in good rock conditions on its stability by 2D discontinuum analysis (2차원 불연속체 해석에 의한 양호한 암반 내의 지하공동 형상비가 안정성에 미치는 영향 검토)

  • You, Kwang-Ho;Jung, Ji-Suug
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.11 no.2
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    • pp.189-198
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    • 2009
  • Recently the concern about the construction of underground structures such as oil and food storage caverns is increasing in Korea and abroad. The stability of those underground caverns is greatly influenced by shape factor and the size of excavation area as well as the joint conditions. In this study, therefore, the effect of the shape factor of an underground cavern on its stability was analyzed in terms of safety factor. To this end, four different shape factors of a cavern excavated in good rock conditions were investigated and sensitivity analyses were performed based on overburden, lateral earth pressure coefficient, joint spacing, properties, and orientation. The stability of a cavern is evaluated in terms of safety factor estimated numerically based on the shear strength reduction technique. In future, this study is expected to be helpful in designing and evaluating the stability of caverns excavated in discontinuous rock masses.

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Three-dimensional Finite-difference Time-domain Modeling of Ground-penetrating Radar Survey for Detection of Underground Cavity (지하공동 탐지를 위한 3차원 시간영역 유한차분 GPR 탐사 모델링)

  • Jang, Hannuree;Kim, Hee Joon;Nam, Myung Jin
    • Geophysics and Geophysical Exploration
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    • v.19 no.1
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    • pp.20-28
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    • 2016
  • Recently many sinkholes have appeared in urban areas of Korea, threatening public safety. To predict the occurrence of sinkholes, it is necessary to investigate the existence of cavity under urban roads. Ground-penetrating radar (GPR) has been recognized as an effective means for detecting underground cavity in urban areas. In order to improve the understanding of the governing physical processes associated with GPR wave propagation, and interpret underground cavity effectively, a theoretical approach using numerical modeling is required. We have developed an algorithm employing a three-dimensional (3D) staggered-grid finite-difference time-domain (FDTD) method. This approach allows us to model the full electromagnetic wavefield associated with GPR surveys. We examined the GPR response for a simple cavity model, and the modeling results showed that our 3D FDTD modeling algorithm is useful to assess the underground cavity under urban roads.

A numerical study on the 3-Dimensional shape characteristics of small underground cavities (소규모 지하공동 3차원 형상 특성을 반영한 수치해석에 관한 연구)

  • An, Joon-Sang;Kang, Kyung-Nam;Son, Ki-Il;Kim, Woo-Seok;Kim, Byung-Chan
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.5
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    • pp.787-807
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    • 2018
  • When conducting the underground safety impact assessment under the special law in Korea, it is essential to investigate the occurrence of underground cavities. When underground cavities were discovered, the underground safety was assessed through numerical analysis. The previous study has suggested the stability evaluation based on the factor of safety by changing the 2D shape of the small underground cavity. In this study, the effects of small underground cavities considering 3D shapes were examined using a continuum analysis program and compared with the 2D results presented in previous study. If the 3-Dimensional shape of the underground cavity is found close to the sphere type, it would be reasonable to evaluate the factor of safety by the shear strength reduction method regardless of the size and position of the cavity. If a high-aspect ratio underground cavity with a depth of 2 m or more from the ground surface and an aspect ratio (a/b) of 2.0 or more is in the vertical direction, not only the factor of safety but the failure mode shape should be cautions in the stability evaluation using the shear strength reduction method. The results of this study are expected to be basic data on underground safety impact assessment.