• Title/Summary/Keyword: 누수균열

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A study on monitoring the inner structure of dam body using high resolution seismic reflection method (고분해능 탄성파 반사법을 이용한 댐체 내부구조 모니터링 연구)

  • Kim Jungyul;Kim Hyoungsoo;Oh Seokhoon;Kim Yoosung
    • 한국지구물리탐사학회:학술대회논문집
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    • 2005.05a
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    • pp.15-20
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    • 2005
  • Defects of dam body which can be induced in seepage or leakage procedure can directly affect dam safety. Therefore, a proper inspection method should be carried out in the first place to find out their positions and sizes, After that, some reinforcement works such as grouting and the corresponding assessment could be taken in a proper way. The dam(center core type earth dam) issued in this study has been in need for intensive diagnosis and reinforcement work, because a lot of slumps similar to cracks, seepage and some boggy area have been observed on the downstream slope. High resolution seismic reflection method was performed on the crest profile twice before and after grouting work(Aug. 2001 and Nov. 2004) aimed at the dam inspection and the assessment of grouting efficiency as well. To enhance the data resolution, P-beam energy radiation technique which can reduce the surface waves and hence to reinforce the reflection events was used. Strong reflection events were recognized in the stack section before grouting work, It seems that the events would be caused by e.g. horizontal cracks with a considerable aperture, Meanwhile such strong reflection events were not observed in the section after grouting. That is, the grouting work was dear able to reinforce the defects of dam body. Hence, the section showed an well arranged picture of dam inner structure. In this sense, seismic reflection method will be a desirable technique for dam inspection and for monitoring dam inner structure as well.

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Risk Analysis Method for Deriving Priorities for Detailed Inspection of Small and Medium-sized Fill Dam (중소형 필댐의 정밀점검 우선순위 도출을 위한 간이 위험도 분석 방법)

  • Kim, Jinyoung;Kang, Jaemo
    • Journal of the Korean GEO-environmental Society
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    • v.21 no.10
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    • pp.11-16
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    • 2020
  • Korea's agricultural reservoir is one of the country's major infrastructures and plays an important role in people's lives. However, aging reservoirs are a risk for life and property. Currently, large and small dams and reservoirs have been constructed nationwide for more than 40 years of aging. Dams and reservoirs built nationwide are managed by various institutions. Therefore, it is difficult to manage all dams and reservoirs due to cost and time. Managers in the field with less management personnel and lack of expertise should be able to quickly identify risk factors for multiple reservoirs. In this study, risk factors such as seepage, leakage, settlement slide, crack and erosion were selected. To assess the risk of the items, we used the analytical hierarchical process (AHP), one of the Multi-Criteria Decision Making (MCDM) methods. The analysis showed that seepage has the greatest impact on reservoir collapse. It is judged that the priority of detailed diagnosis can be determined by evaluating the risk of dam reservoir collapse in a convenient way in advance using the calculated weight.

A study on Monitoring the Inner Structure of Dam Body Using High Resolution Seismic Reflection Method (고분해능 탄성파 반사법을 이용한 댐체 내부구조 모니터링 연구)

  • Kim, Jung-Yul;Kim, Hyoung-Soo;Oh, Seok-Hoon;Kim, Yoo-Sung
    • Journal of the Korean Geophysical Society
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    • v.8 no.1
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    • pp.1-6
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    • 2005
  • Defects of dam body which can be induced in seepage or leakage procedure can directly affect dam safety. Therefore, a proper inspection method should be carried out in the first place to find out their positions and sizes. After that, some reinforcement works such as grouting and the corresponding assessment could be taken in a proper way. The dam(center core type earth dam) issued in this study has been in need for intensive diagnosis and reinforcement work, because a lot of slumps similar to cracks, seepage and some boggy area have been observed on the downstream slope. High resolution seismic reflection method was performed on the crest profile twice before and after grouting work(Aug. 2001 and Nov. 2004) aimed at the dam inspection and the assessment of grouting efficiency as well. To enhance the data resolution, P-beam energy radiation technique which can reduce the surface waves and hence to reinforce the reflection events was used. Strong reflection events were recognized in the stack section before grouting work, It seems that the events would be caused by e.g. horizontal cracks with a considerable aperture. Meanwhile such strong reflection events were not observed in the section after grouting. That is, the grouting work was dear able to reinforce the defects of dam body. Hence, the section showed an well arranged picture of dam inner structure. In this sense, seismic reflection method will be a desirable technique for dam inspection and for monitoring dam inner structure as well.

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Evaluation of the Pull-out Resistance of the SMA Wire Connector (SMA 와이어를 이용한 연결재의 인발저항성능 평가)

  • Jung, Chi-Young;Woo, Tae-Ryeon;Lee, Jong-Han;Cheung, Jin-Hwan
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.1
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    • pp.130-137
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    • 2019
  • Precast concrete (PC) structure is one of the type of the structures which is made in a facility prior to installing it to a construction field. The contact surfaces between two PC structures should be treated for obtaining enough binding force by inducing prestressing force. However, in the many cases, the contact surface causes the crack and leakage of water. These cracks and water leakage can cause the corrosion of the rebar, and the corrosion of the rebar can severely reduce the long-term durability. In this study, the SMA wire connector is suggested to solve the problem with the contact surfaces between two PC structures. The pull-out resistance of the suggested SMA wire connector is evaluated by conducting the tests to find the effect of the number of wires, shape of connector part, and shape memory effect. As a result of this study, the empirical formula is suggested to estimate the pull-out resistance related with the effects of the shape of the connector, shape memory effect, and the adhesive force. The validity between the estimated pull-out resistance and the measured value is confirmed.

Application of Damage Index for Limit State Evaluation of a Steel Pipe Tee (강재 배관 Tee의 한계상태 평가를 위한 손상지수의 적용)

  • Kim, Sung-Wan;Yun, Da-Woon;Jeon, Bub-Gyu;Kim, Seong-Do
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.4
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    • pp.30-39
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    • 2022
  • Maintaining structural integrity of major apparatuses in a nuclear power plant, including piping system, is recognized as a critical safety issue. The integrity of piping system is also a critical matter related to the safety of a nuclear power plant. The actual failure mode of a piping system due to a seismic load is the leakage due to a fatigue crack, and the structural damage mechanism is the low-cycle fatigue due to large relative displacement that may cause plastic deformation. In this study, in-plane cyclic loading tests were conducted under various constant amplitudes using specimens composed of steel straight pipes and a steel pipe tee in the piping system of a nuclear power plant. The loading amplitude was increased to consider the relative displacement generated in the piping system under seismic loads, and the test was conducted until leakage, which is the limit state of the steel pipe tee, occurred due to fatigue cracks. The limit state of the steel pipe tee was expressed using a damage model based on the damage index that used the force-displacement relationship. As a result, it was confirmed that the limit state of the steel pipe tee can be quantitatively expressed using the damage index.

A Study on Efficient Deconstruction of Supporters with Response Ratio (응답비를 고려한 효율적인 버팀보 해체방안에 관한연구)

  • Choi, Jung-Youl;Park, Sang-Wook;Chung, Jee-Seung
    • The Journal of the Convergence on Culture Technology
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    • v.8 no.5
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    • pp.469-475
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    • 2022
  • As the recent structure construction is constructed as a large-scale and deep underground excavation in close proximity to the building, the installation of retaining wall and supporters (Struts) has become complicated, and the number of supporters to avoid interference of the structural slab has increased. This construction process becomes a factor that causes an increase in construction joints of a structure, leakage and an increase in wall cracks. In addition, this reduced the durability and workability of the structure and led to an increase in the construction period. This study planned to dismantle the two struts simultaneously as a plan to reduce the construction joints, and corrected the earth pressure by assuming the reaction force value by the initial earth pressure and the measured data as the response ratio. After recalculating the corrected earth pressure through the iterative trial method, it was verified by numerical analysis that simultaneous disassembly of the two struts was possible. As a result of numerical analysis applying the final corrected earth pressure, the measured value for the design reaction force was found to be up to 197%. It was analyzed that this was due to the effect of grouting on the ground and some underestimation of the ground characteristics during design. Based on the result of calculating the corrected earth pressure in consideration of the response ratio performed in this study, it was proved analytically that the improvement of the brace dismantling process is possible. In addition, it was considered that the overall construction period could be shortened by reducing cracks due to leakage and improving workability by reducing construction joints. However, to apply the proposed method of this study, it is judged that sufficient estimations are necessary as there are differences in ground conditions, temporary facilities, and reinforcement methods for each site.

Characterization of Durability and Deterioration Eroded by Chemical Attack on the Concrete Lining in Conventional Tunnel (화학적 침식을 받은 재래식 터널 콘크리트 라이닝의 내구성능 및 열화특성)

  • Kim, Dong-Gyou;Lee, Seung-Tae;Jung, Ho-Seop
    • Journal of the Korean Geotechnical Society
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    • v.23 no.12
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    • pp.25-32
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    • 2007
  • This study is to evaluate the effect of chemical attack on durability and deterioration of lining concrete in tunnel. Surface examination, nondestructive inspection, uniaxial compressive strength test, carbonation test, chloride diffusion test, micro-structural analysis were performed to analyze the deterioration of lining concrete in tunnel constructed 70 years ago. From surface examination results, the tunnel had been repaired and reinforced in several times. It has many cracks, water-leakage, efflorescence and exploitation. Compressive strengths obtained from nondestructive inspection and uniaxial compressive strength test have measured $17.5{\sim}34.7MPa$, and $12.8{\sim}40.3MPa$, respectively. Carbonation depth specimen cored from concrete lining has ranged from 3mm to 27mm. From chloride diffusion test, most specimens have low permeability. And the XRD analysis was able to detect ettringite and thaumasite, which were confirmed by SEM and EDS results to be the causes for the deterioration of lining concrete.

Geological Environments and Deterioration Causes of the Buddhist Triad Cave in Gunwi, Korea (군위 삼존석굴의 지질환경과 훼손원인)

  • 황상구;김수정;이현우
    • Economic and Environmental Geology
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    • v.35 no.5
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    • pp.407-420
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    • 2002
  • The Buddhist Triad Cave in Gunwi (National treasure No. 109) consists of porphyritic biotite granite, and it has been deteriorated into microorganic smears, white films, brown rusts, granular decay, color changes, and joints by the same weathering factors as rain, moisture, temperature variation and microorganic living. Main origin is probably the rain that leaks into the cave along joints in Palgongsan granite, and then its moisture grows many microorganism and is frozen over during winter. The granites around the cave regularly develop two NEE and NWW joint sets that are conjugate to be a joint system. The NEE set extends far away with narrow joint spacings and affects the leakage of the rains, and is divided into 4 joint zones, among which J$_{m}$ and J$_{3}$ immediately affect the leaking water into the cave. An extensional Joint, in northern wall of the cave, was formed by toppling of the block between J$_{m}$and J$_{3}$joint zones from widening the Jm aperture by roots of a big pine tree, and passes through the J$_{m}$joint zone. This bypass allows no circulation of small rain, but a good circulation of heavy rain from influx to the cave for a long pathway. Many Joints and cracks, in the ceiling near the cave entrance, immediately get through the J$_3$ joint zone, and have a good circulation of small rain 10 mm. Both J$_{m}$and J$_{3}$ joint zones are, therefore, chief influxes that cause leakage of the rains.

Evaluation on Flexural Performance of Precast Bridge Decks with Ribbed Connection (요철형 이음단면을 갖는 프리캐스트 교량 바닥판의 휨성능 평가)

  • Shin, Dong-Ho;Park, Se-Jin;Oh, Hyun-Chul;Kim, In-Gyu;Kim, Young-Jin
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.19 no.3
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    • pp.1-9
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    • 2015
  • Due to the increasing number of deteriorated bridges worldwide, the importance of maintenance and replacement of existing bridges are being emphasized. Cast-in-place concrete deck which is mainly applied to deck replacement of existing bridges have problems such as deterioration concerns by initial crack, labor cost increase, difficulties of maintenance and replacement, construction time increase, and indirect cost increase by traffic congestion. On the contrary, a precast concrete deck is considered as an effective alternative because of its quality assurance and accelerated construction. The connection method ensuring the required strength and durability is especially important, because the connection part of the precast concrete deck is vulnerable to cracks and leakage. Therefore, this study proposes precast bridge decks with ribbed connection which are more improved than existing bridge deck joints, and flexural performance is verified through various parameter tests.

Fatigue Performance of Precast Decks using Ribbed Loop Joints in a Two-Girder Continuous Composite Bridge (2거더 연속합성형교 요철형 루프이음 프리캐스트 바닥판의 피로성능)

  • Lee, Han-Joo;Yeo, Woon-Young;Shin, Dong-Ho;Kim, In-Gyu;Park, Se-Jin
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.1
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    • pp.85-93
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    • 2019
  • Structural performance and serviceability of precast deck system are mostly determined by connection details between precast decks. Particularly, since the bridge deck is under repeated loads such as traffic loads, fatigue behavior and performance of joints should be investigated. In this study, a two-girder continuous composite bridge specimen was fabricated using the asymmetric ribbed loop joints, and static and fatigue load tests were conducted to evaluate the structural behavior and the crack pattern of the bridge deck. From the test results, the proposed precast deck system resulted in sufficient fatigue performance and failure strength. Therefore, the proposed precast deck system can be applied to the connection part of precast decks effectively.