• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.376-383
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• 2005

In this study, we conducted geophysical investigations for the organization of integrated geophysical methods to detect underground cavities of ground subsidence area at the field test site, located at Yongweol-ri, Muan-gun. We examined the applicability of geophysical methods such as electrical resistivity, electromagnetic, and microgravity to cavity detection with the aid of borehole survey results. Underground cavities are widely present within the limestone bedrock overlain by the alluvial deposits in the area of the test site where the ground subsidences have occurred in the past. The limestone cavities are mostly filled with groundwater and clays in the test site. Thus, cavities have low electrical resistivity and density compared to the surrounding host bedrock. The results of the study have shown that the zones of low resistivity and density correspond to the zones of the cavities identified in the boreholes at the site, and that the geophysical methods used are very effective to detect underground cavities. Furthermore, we could map the distribution of cavities more precisely with the test results incorporated from the various geophysical methods. It is also important to notice that the microgravity method is a very promising tool since it has rarely used for the cavity detection in korea. Beyond the investigation of underground cavities, the geophysical methods are required to provide useful information for the reinforcement design for the ground subsidence areas. It is, therefore, necessary to develop integrated geophysical technique incorporating different geophysical methods to precisely map underground cavities and image the subsurface of the ground subsidence areas.

• 지질공학
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• 제27권3호
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• pp.305-312
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• 2017

The most effective way to distinguish subsurface interfaces that produce various geophysical responses is through the integration of multiple geophysical methods, with each method detecting both a complementary and unique set of distinct physical properties relating to the subsurface. In this study, shallow seismic reflection (SSR) and ground penetrating radar (GPR) surveys were conducted at the Cheongju-Gadeok site of the Korea National Groundwater Monitoring Network to map the water table, which was measured at 12 m depth during the geophysical surveys. The water table proved to be a good target reflector in both datasets, as the abrupt transition from the overlying unsaturated weathered rock to the underlying saturated weathered rock yielded large acoustic impedance and dielectric constant contrasts. The two datasets were depth converted and integrated into a single section, with the SSR and GPR surveys conducted to ensure subsurface imaging at approximately the same wavelength. The GPR data provided detailed information on the upper ~15 m of the section, whereas the SSR data imaged structures at depths of 10-45 m. The integrated section thus captured the full depth coverage of the sandy clay, water table, weathered rock, soft rock, and hard rock structures, which correlated well with local drillcore and water table observations. Incorporation of these two geophysical datasets yielded a synthetic section that resembled a simplified aquifer model, with the best-fitting seismic velocity, dielectric constant, and porosity of the saturated weathered layer being $v_{seismic}=1000m/s$, ${\varepsilon}_r=16$, and ${\phi}=0.32$, respectively.

• 지구물리와물리탐사
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• 제9권4호
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• pp.271-278
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• 2006

국내 지반침하의 주요 원인 중의 하나인 석회암 공동에 대한 조사는 단순한 지반침하 원인의 규명 이외에 지반 침하 지역 또는 예상지역의 보강 설계 및 사후 관리에 이르기까지 폭넓은 지반 정보를 제공하는 역할을 수행한다는 측면에서 매우 중요하다고 할 수 있다. 지반침하지역 공동탐지에 유용하게 사용되는 물리탐사기법으로 한 종류의 지반 물성을 이용하는 단위 물리탐사기술보다는 여러 가지 물성의 지하를 조명하는 복합 물리탐사기술에 대한 연구가 필요하다. 본 연구에서는 지반침하조사 시 지하공동 탐지를 위한 복합 물리탐사 시스템 구축의 일환으로 전라남도 무안군 무안읍 용월리에 과거 석회암 공동에 의한 지반침하 경력이 있는 지역을 현장 실험장으로 이용하여 다양한 종류의 물리탐사를 실시하였다. 그 중 전기비저항탐사, 전자탐사 그리고 고정밀 중력탐사 결과로부터 지하 공동의 위치 및 분포를 추정 해석하고, 시추조사 결과와 비교함으로서 단위 물리탐사 기술의 공동탐지 적용성에 대하여 고찰하였다. 시추조사결과, 실험장 지역 기반암내 공동은 대부분 지하수 또는 물로 포화된 점토로 채워져 있어 주위 기반암에 비하여 매우 낮은 전기비저항 및 밀도를 가지며, 넓은 지역에 걸쳐 망구조로 분포하고 있는 것으로 해석된다. 실험장에 적용한 전기비저항, 전자 및 고정밀 중력 탐사 결과, 저비저항대와 음의 중력 이상대 분포 지역이 시추 조사에서 확인된 지하 공동의 분포 위치와 상당 부분 일치함을 보여 이들 각 탐사법들이 지하 공동 분포 파악에 효과적임이 입증되었다. 또한 개별 탐사 기법 해석과 아울러 각종 탐사결과를 종합함으로써 보다 정확한 지하공동의 분포 해석이 가능하였으며, 특히 국내에서의 사용이 미비하였던 고정밀 중력탐사기법이 지하공동 탐지에 매우 유용함을 확인하였다.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2003년도 Proceedings of the international symposium on the fusion technology
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• pp.410-415
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• 2003

Ground subsidence has occurred in the downtown of Muan-eup in Korea. Integrated geophysical survey, including two-dimensional resistivity, CSMT(Controlled source magnetotelluric), magnetic, borehole logging, GPR and resistivity tomography, has been conducted to investigate the cause of subsidence and ground conditions. Since the target area is in the city downtown, there were no spaces for surface geophysical methods. To get regional geology and to facilitate the detailed geophysical interpretation in the survey area, two-dimensional resistivity, CSMT and magnetic surveys have been applied in the outer region of the downtown. From these results, we could accurately define the Gwangju fault system and estimate the geologic conditions in the downtown. For the detailed survey of the downtown area, resistivity tomography and borehole logging data have been acquired using a few tens of densely located boreholes. Among these survey results, borehole logging data provided the guide to classification of the rock type and we could define the geologic boundary of granite and limestone formations. From the resistivity tomograms of 42 sections, which are densely located enough to be interpreted in a three-dimensional manner, we could delineate the possible weak zones or cavities in the limestone formations. In particular, resistivity tomograms in the subsided area showed the real image of ground subsidence. The map of hazardous zone has been derived from the joint interpretation of these survey results and we could provide the possible reinforcement strategy in this area.

• 한국지구물리탐사학회:학술대회논문집
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• 한국지구물리탐사학회 2008년도 공동학술대회
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• pp.113-118
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• 2008

Among the geophysical methods, Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) comprise the most promising techniques in resolving buried archaeological structures in urban territories. In this work, two case studies which involve an integrated geophysical survey employing the surface three dimensional (3D) ERT and GPR techniques, in order to archaeologically characterize the investigated areas, are presented. Totally more than 4000 square meters were investigated from the test field sites, which are located at the centre of two of the most populated cities of the island of Crete, in Greece. The ERT and the GPR data were collected along dense and parallel profiles. The subsurface resistivity structure was reconstructed by processing the apparent resistivity data with a 3D inversion algorithm. The GPR sections were processed with a systematic way applying specific filters to the data in order to enhance their information context. Finally, horizontal depth slices representing the 3D variation of the physical properties were created and the geophysical anomalies were interpreted in terms of possible archaeological structures. The subsequent excavations in one of the sites verified the geophysical results, enhancing the applicability of ERT and GPR techniques in the archaeological exploration of urban territories.

• Journal of Power Electronics
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• 제17권4호
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• pp.905-913
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• 2017

To enhance the zero-voltage switching (ZVS) range and power density of the phase-shift full-bridge (PSFB) ZVS converters used in geophysical exploration, an additional resonant inductor is used as a leakage inductance and a blocking capacitor which is equivalent to interlayer capacitance is integrated into a novel integrated inductor-capacitor-transformer (L-C-T). The leakage inductance and equivalent interlayer capacitance of the novel integrated L-C-T are difficult to determine by conventional methods. To address this issue, this paper presents accurate and efficient methods to compute the leakage inductance and equivalent interlayer capacitance. Moreover, the accuracy of this methodology, which is based on electromagnetic energy and Lebedev's method, is verified by an experimental analysis and a finite element analysis (FEA). Taking the problems of the novel integrated L-C-T into consideration, the losses of the integrated L-C-T are analyzed and the temperature rise of the integrated L-C-T is determined by FEA. Finally, a PSFB ZVS converter prototype with the novel integrated L-C-T is designed and tested.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2004년도 Proceedings of ISRS 2004
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• pp.662-663
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• 2004

In general, mineral resources prospect is performed in several methods including geological survey, geological structure analysis, geochemical exploration, airborne geophysical exploration and remote sensing, but data collected through these methods are usually not integrated for analysis but used separately. Therefore we compared various data integration techniques and generated final mineral resources potentiality map.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.491-498
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• 2004

In recent years, as an effort to grasp the leading position in the field of maritime trading, new ports and container terminals arc now under construction. Old ports are extended. At the beginning, stones were thrown down to form stone embankments, that is stone-dams, in the outer and inner boundaries of the planned reclamation-land. S.C.P(Sand Compaction Pile) works are often needed to improve the stability of stone-dams, where marine sediments arc relatively thick. Here, interests are centered on the shape of stone body. In this, drilling work won't provide a sufficient resolution. In addition, the result corresponds to only one borehole point information. Thus, the aim of this paper is to introduce an affordable technology, that is, a combined geophysical method(seismic tomography + Televiewer) enables to get the whole information about stone-dam section. The measuring and evaluating procedure is described in detail with an emphasis on dealing with the use of seismic detonator, proper borehole deployment and integrated data analysis. Examples of field experiments at Busan new port are illustrated, which will prove the benefit of combined geophysical method.

• 한국토양환경학회지
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• 제1권1호
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• pp.29-38
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• 1996

폐기물 매립지의 수평크기와 심도 파악을 위해 여러 물리탐사법중에서 GPR과 전기비저항 탐사에 의한 조사가 시험으로 수행되었다. 탐사는 조사대상지역의 현장여건으로 인해 경계부와 매립지 중심부 일부에 제한되었다. GPR탐사에서는 50MHz 안테나를 이용하였고 전기비저항탐사는 쌍극자 배열법으로 수행되어졌으며, 복합해석을 위한 중복탐사가 이루어졌다. GPR 탐사에 의한 쓰레기 매립지 수평경 계 해석은 가능하였으며, 심도는 수평경계를 포함한 일부 구간에서만 확인되었다. 전기 비저항탐사는 매립지내의 물성을 제공함으로서 비교해석이 가능하다면 효과적인 정보획득이 가능할 것으로 예상된다. 이 해석결과는 주변의 사추결과와 잘 일치되었으며, 따라서, 매립지의 수평적 크기와 규모 파악을 위한 조사시 두 조사법의 조합은 적합하다고 판단된다.

• 지질공학
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• 제2권2호
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• pp.113-130
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• 1992

지하 심부에 발달된 파쇄대 및 단층등은 지하수의 유통통로가 되어 심부 지하수 개발과 직접적인 관련이 있다. 그러므로 지표에서 지하 파쇄대 및 단층을 탐지함은 심부 지하수 개발 대책 수립에 대단히 중요하다. 본 연구에서는 이와 같은 문제에 대한 물리탐사법의 확립을 위해 경주 보문 관관단지내에서 다수의 물리탐사법을 동원하여 종합적인 탐사를 실시 그 자료를 해석하였다. 경주지역은 자력탐사, VLF 전자탐사, 쌍극자 배열 전기탐사, CSAMT 탐사등이 실시되었다. 자려탐사의 목적은 관입암으로 추정되는 화성암의 분포상황의 파악에 VLF 전자탐사는 지표천부의 파쇄대의 탐지에 있다. 쌍극자 배열 전기탐사는 비교적 천부으 비저항 분포 및 단층 파쇄대의 탐지에 CSAMT 탐사는 비교적 심부까지의 비저항 분포 및 단층 파쇄층 탐지에 있다. 경주지역 탐사자료의 종합적인 해석 결과 자력탐사에 의해 퇴적암 하부에 발달하는 화강암의 분포상황을 파악할 수 있었으며, VLF 탐사로써 지표천부의 다수의 파쇄대를 확인하였다. 자력탐사와 전기탐사 그리고 전기탐사의 종합적인 해석에 의해 거의 남북 방향으로 달리는 구조선 및 비저항 분포 상태를 파악할 수 있었으며 이에 의하여 시추가 추천되었다.