• Title/Summary/Keyword: non-destructive geophysical survey

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Geophysical exploration for the Site Charcteristics of Iljumun Gate in Hwanseongsa Temple (지구물리탐사를 이용한 경산시 환성사 일주문 지반조사)

  • Kim, Ki-Hyun;Suh, Man-Cheol
    • 한국지구물리탐사학회:학술대회논문집
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    • 2008.10a
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    • pp.131-136
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    • 2008
  • We performed a non-destructive geophysical survey such as an elastic wave survey, electric specific resistance survey, plate loading test, etc. in order to grasp the structure and status of the ground around the pillar gate and to provide the directions and design data for preservation and maintenance during reconstruction. The result of electric specific resistance survey shows 50-1300 ohm-m range of general electric specific resistance distribution. Besides, the positions around 1m south of stone pillars, between stone pillar No.3 and 4, and 1m north of stone pillar No.2 and 3 show abnormality of relatively lower electric specific resistance than their surroundings. The abnormality of low electric specific resistance appearing between stone pillar No.3 and 4 shows consistency with the abnormal section appearing from the result of elastic wave reflection survey. The result of a plate loading test shows that allowable bearing force is over $10.70tf/m^2$, and the settlement amount at this time was calculated as 19.635mm. The design load during reconstruction of pillar gates was calculated as $16.37t/m^2$ by applying assumption values, which is far more than the allowable bearing force, so it is judged that a measure to strengthen the foundation ground is necessary.

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STUDIES ON THE CHARACTERISTICS OF STONE STRUCTURES BY GEOTECHNICAL AND DYNAMIC STRUCTURAL ENGINEERINGS (석조구조물의 효율적 유지관리를 위한 지질공학적 및 구조동역학적 특성연구)

  • HoWoongShon;SungMinLee
    • Journal of the Korean Geophysical Society
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    • v.6 no.4
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    • pp.277-294
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    • 2003
  • Structures show the phenomena of deformation and lowering of function with time-lapse by artificial environments and changes of geotechnical conditions or accumulation of initial deformation elements. This study aims the structural assessment of cultural property, Chum-Sung-Dae, located in Kyeongjucity, Korea. It was built about 1,300 years ago, and has undergone deformation and ground-subsidence with time-lapse. Non-destructive evaluation techniques were applied to the Chum-Sung-Dae, to protect it from survey. Because of this reason, 3D precise laser scanning surveying system was applied to measure the exact size of Chum-Sung-Dae, displacement and declining angles. Geophysical exploration also was applied to study the subsurface distribution of geotechnical parameters or physical properties. Natural frequencies were measured from real and model of Chum-Sung-Dae to study the dynamic characteristics of vibration and/or earthquake load and stiffness of structures.

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GEOTECHNICAL ENVIRONMENT SURVEY (2) (고심도 지반환경 조사 - 비파괴 물리탐사의 적용 (2))

  • HoWoongShon;SeungHeeLee;HyungSooKim
    • Journal of the Korean Geophysical Society
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    • v.6 no.4
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    • pp.261-268
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    • 2003
  • Lots of various utilities are buried under the surface. The effective management of underground utilities is becoming the very important subject for the harmonious administration of the city. Ground Penetrating Radar(GPR) survey including other various underground survey methods, is mainly used to detect the position and depth of buried underground utilities. However, GPR is not applicable, under the circumstances of shallow depth and places, where subsurface materials are inhomogeneous and are composed of clay, salt and gravels. The aim of this study is to overcome these limitations of GPR and other underground surveys. High-frequency electromagnetic (HFEM) method is developed for the non-destructive precise deep surveying of underground utilities. The method is applied in the site where current underground surveys are useless to detect the underground big pipes, because of poor geotechnical environment. As a result, HFEM survey was very successful in detecting the buried shallow and deep underground pipes and in obtaining the geotechnical information, although other underground surveys including GPR were not applicable. Therefore this method is a promising new technique in the lots of fields, such as underground surveying and archaeology.

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Imaging Inner Structure of Bukbawi at Mt. Palgong Provincial Park Using Ground Penetrating Radar (지하투과레이더를 활용한 팔공산 도립공원 북바위 내부구조 연구)

  • Kim, Hyeong-Gi;Baek, Seung-Ho;Kim, Seung-Sep;Lee, Na Young;Kwon, Jang-Soon
    • Economic and Environmental Geology
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    • v.50 no.6
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    • pp.487-495
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    • 2017
  • A granite rock body, called 'Bukbawi', located on a mountaineering trail at Mt. Palgong Provincial Park is popular among the public because it resembles a percussion instrument. If someone hits the specific surface area of this rock body, people can hear drum-like sound. Such phenomenon may be geologically associated with exfoliation process of the granite body or miarolitic cavity developed after gasses escaped during formation of granite. To understand better the inner structure causing drum-like sound, we carried out a non-destructive ground-penetrating radar survey. In this study, as our primary target is very close to the surface, we utilized 1 GHz antennas to produce high-resolution near-surface images. In order to construct 3-D internal images, the measurements were conducted along a pre-defined grid. The processed radargrams revealed that the locations associated with 'drum' sound coincide with strong reflections. In addition, both reflection patterns of fracture and cavity were observed. To further quantify the observed reflections, we simulated GPR scans from a synthetic fracture in a granite body, filled with different materials. The simulated results suggest that both exfoliation process and miarolitic cavity may have contributed to the 'drum' phenomena. Furthermore, the radargrams showed a well-developed cavity signature where two major reflection planes were crossed. Thus, our study is an example of non-destructive geophysical studies that can promote Earth Science in the broader community by examining geological structures attracting the public.

Quantitative Evaluation of Leak Index from Electrical Resistivity and Induced Polarization Surveys in Embankment Dams (전기비저항 및 유도분극 탐사에 의한 저수지 누수지수 산출)

  • Cho, In Ky;Kim, Yeon Jung;Song, Sung Ho
    • Geophysics and Geophysical Exploration
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    • v.25 no.3
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    • pp.120-128
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    • 2022
  • There are 17,000 reservoir dams in Korea, of which more than 85% were built over 50 years ago. Old embankment dams are weakened by internal erosion and suffusion phenomena due to preferential leakage paths and this ongoing weakening can cause their failure. Therefore, early warning associated with leakage in an embankment dam is crucial to prevent its failure. An electrical resistivity survey is a non-destructive, real-time and in-situ technique for detecting the development of leakage zones and general conditions of embankment dams. Because of its advantages, the electrical resistivity survey is widely used for reservoir safety inspections. However, the electrical resistivity survey is still not officially included in the precise safety inspection of reservoir dams because it cannot present a quantitative index of dam safety. In this study, we propose a method for calculating the leak index according to the water content evaluated from the electrical resistivity survey and/or induced polarization survey. Particularly, by proposing a quantitative leak index calculation method from monitoring surveys and independent surveys, we provide a theoretical basis for including electrical resistivity and induced polarization surveys as components of the precise safety inspection of reservoirs dams.

Studies on the characteristics of stone structures by shape reversal, geotechnical and dynamic structural engineerings (석조구조물의 효율적 유지관리를 위한 형상역공학적, 지반공학적 및 구조동역학적 특성연구 - 첨성대를 중심으로 -)

  • Shon, Bo-Woong;Kim, Seong-Beom
    • 한국지구물리탐사학회:학술대회논문집
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    • 2004.08a
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    • pp.25-48
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    • 2004
  • Structures show the phehomena of deformation and lowering of function with time-lapse by artificial environments and changes of geotechnical conditions or accumulation of initial deformation elements. This study aims the structural assessment of cultural property, Chum-Sung-Dae, located in Kyeongju city, Korea. It was built about 1,300 years ago, and has undergone deformation and ground-subsidence with time-lapse. Non-destructive evaluation techniques were applied to the Chum-Sung-Dae, to protect it from survey Because of this reason, 3D precise laser scanning surveying system was applied to measure the exact size of Chum-Sung-Dae, displacement and declining angles. Geophysical exploration also was applied to study the subsurface distribution of geotechnical parameters or physical properties. Natural frequencies were measured from real and model of Chum-Sung-Dae to study the dynamic characteristics of vibration and/or earthquake load and stiffness of structures.

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