• Title/Summary/Keyword: 단극배열

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The Crosshole Resistivity Method Using the Mixed Array (혼합배열을 사용하는 시추공간 전기비저항 탐사)

  • Cho In-Ky;Han Sung-Hoon;Kim Ki-Ju
    • Geophysics and Geophysical Exploration
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    • v.5 no.4
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    • pp.250-256
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    • 2002
  • Resistivity tomography has become an important tool to image underground resistivity distribution. This method has been widely applied to site investigation for engineering and environmental purpose. In resistivity tomography, various electrode arrays can be used and each array has both merits and demerits. For example, the pole-pole array has high signal to noise ratio (S/N ratio), but its resolution is too low. The dipole-dipole array has low S/N ratio, but its resolution is very high. The Pole-dipole may has intermediate Snf ratio and resolution. The modified Pole-dipole array, recently proposed, shows reasonable S/N ratio and resolution, which are comparable to the pole-dipole array. These electrode arrays except the pole-pole array, however, have the problem that the apparent resistivity can diverge at some special electrode Positions. Also, the Pole-Pole array may not reflect the doe resistivity of an anomalous body. In this study, we propose a new electrode array, mixed array, where pole-dipole and modified pole-dipole ways are selectively used with the relative positions of current and potential electrodes. The mixed array has the same level of S/N ratio and resolution as the pole-dipole array and the apparent resistivity does not diverge in the receiver hole. Furthermore, the apparent resistivity using the array can reflect the true resistivity of the anomalous body.

A Study on the Modified Electrode Arrays in Two-Dimensional Resistivity Survey (2차원 전기비저항 탐사를 위한 변형된 전극배열법에 관한 연구)

  • Kim Jung-Ho;Yi Myeong-Jong;Song Yoonho;Chung Seung-Hwan
    • Geophysics and Geophysical Exploration
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    • v.4 no.3
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    • pp.59-69
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    • 2001
  • Five kinds of modified electrode arrays were proposed to overcome the weak points of the commonly used arrays using dipole and/or pole in two-dimensional resistivity surveys. The modified pole-pole array was suggested to overcome the inefficiency caused by distant earthing in pole-pole array. Four kinds of modified arrays using dipole were designed to enhance the signal-to-noise ratio of the conventional dipole-dipole and pole-dipole arrays through boosting up the measured potential difference. In the numerical experiments using the two-dimensional modeling and inversion, the effects of the ambient electrical noise and the resolving power were examined and the results showed the validity of the modified arrays proposed in this study.

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A problem in the cross-hole resistivity method using pole-pole array (단극배열을 이용한 시추공-시추공 전기비저항 탐사법의 문제점)

  • Jo, In Gi;Choe, Gyeong Hwa
    • Journal of the Korean Geophysical Society
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    • v.1 no.1
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    • pp.51-58
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    • 1998
  • A numerical program has been developed to model 2-D resistivity responses for a pole-pole array configuration in cross-hole resistivity measurements. Apparent resistivity and secondary potential were computed using the program for a cylindrical inhomogeneity in an uniform host medium excited by a point source of current in a borehole. Surprisingly apparent resistivity in the receiver hole turns out to be lower than the one of surrounding medium regardless of the conductivity of cylindrical inhomogeneity. Using only cross-hole data, therefore, it is impossible to interpret the conductivity of inhomogeneity. To overcome this problem, 3-D measurement and interpretation are necessary. If 3-D data acquisition is impossible, inline data should be used to get the information about the conductivity of inhomogeneity.

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A Study to Estimate the Seawater Leakage Zone of the Embankment using SP and Pole-pole Array Resistivity Survey (SP 및 단극배열 전기비저항탐사를 이용한 방조제 누수지점 탐지)

  • Song Sung-Ho;Lee Kyu-Sang;Kim Jin-Ho;Jang Eui-Woong
    • 한국지구물리탐사학회:학술대회논문집
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    • 2000.09a
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    • pp.19-40
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    • 2000
  • We applied both SP monitoring and pole-pole array resistivity surveys and SP survey and dipole-dipole array resistivity survey to leakage problems in several embankments and dike, respectively, to estimate and detect the zone of leakage. The embankment is generally affected by tidal variation and has low resistivity characteristics due to the high saturation of seawater. According to this situation, SP monitoring and resistivity survey using pole-pole electrode array, which is relatively more effective to the conductive media, were carried out to delineate the leakage zones of sea water through the embankment. We checked out electrical conductivity(EC) and temperature variations along the inner part of the embankment to detect the zone of seawater leakage and found that the measured EC value agreed to that of seawater in the leakage zone and the temperature was lower than that of the vicinity of leakage zone. SP monitoring results were coincide with tidal variations at each embankment. Based on the survey results, it is concluded that both SP monitoring and the pole-pole array resistivity method are quite effective for investigation of seawater leakage zones in the embankment.

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Behavior of Normalized Voltage Curves in the Resistivity Method (전기비저항 탐사에서 전위감쇠곡선의 거동특성)

  • Cho, In-Ky;Lee, Keun-Soo
    • Geophysics and Geophysical Exploration
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    • v.13 no.4
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    • pp.364-369
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    • 2010
  • Resistivity data should be edited before the inversion because resistivity data are contaminated by a lot of noise. Generally, outlier or data violating pants-leg effect in dipole-dipole array were used to be rejected in the apparent resistivity pseudo-section. For more precise data editing, normalized voltage curves are used. In this study, we analyzed the behavior of normalized voltage curves for pole-pole, pole-dipole and dipole-dipole arrays in the presence of threedimensional inhomogeneities, and finally re-examined the validity of normalized voltage curves in the editing process of resistivity data.

3-D Inversion of 3-D Synthetic DC Resistivity Data for Vein-type Ore Deposits (국내 맥상광체조사를 위한 3차원 전기비저항 모델링자료의 3차원 역산 해석)

  • Lee, Ho-Yong;Jung, Hyun-Key;Jeong, Woo-Don;Kwak, Na-Eun;Lee, Hyo-Sun;Min, Dong-Joo
    • Journal of the Korean earth science society
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    • v.30 no.6
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    • pp.699-708
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    • 2009
  • Recently as the interest in the development of domestic ore deposits has increased, we can easily find some studies on exploration geophysics-based ore-deposit survey in literature. Based on the fact that mineralized zone are generally more conductive than surrounding media, electrical resistivity survey among several geophysical surveys has been applied to investigate metallic ore deposits. Most of them are grounded on 2-D survey. However, 2-D inversion may lead to some misinterpretation for 3-D geological structures. In this study, we investigate the feasibility of the 3-D electrical resistivity survey to 3-D vein-type ore deposits. We first simulate 2-D dipole-dipole survey data for survey lines normal to the strike and 3-D pole-pole survey data, and then perform 3-D inversion. For 3-D ore-body structures, we assume a width-varying dyke, a wedge-shaped, and a fault model. The 3-D inversion results are compared to 2-D inversion results. By comparing 3-D inversion results for 2-D dipole-dipole survey data to 3-D inversion results for 3-D pole-pole survey data, we could note that the 2-D dipole-dipole survey data yield better inversion results than the 3-D pole-pole data, which is due to the main characteristic of the pole-pole array. From these results, we are convinced that if we have certain information on the direction of the strike, it would be desirable to apply 2-D dipole-diple survey for the survey lines normal to the strike. However, in most cases, we do not have any information on the direction of the strike, because we already developed the ore deposit with the outcrops and the remaining ore deposits are buried under the surface. In that case, performing 3-D pole-pole electrical resistivity survey would be a reasonable choice to obtain more accurate interpretation on ore body structure in spite of low resolution of pole-pole array.

Application of SP and Pole-pole Array Electrical Resistivity Surveys to the Seawater Leakage Problem of the Embankment (방조제 누수지점 탐지를 위한 SP및 단극배열 전기비저항탐사의 적용)

  • 송성호;이규상;김진호;권병두
    • Economic and Environmental Geology
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    • v.33 no.5
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    • pp.417-424
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    • 2000
  • We applied SP monitoring and resistivity surveys using the pole-pole electrode array to seawater leakage problems in the Youngsan estuary dam and the Eoeun embankment to estimate and detect the zone of seawater leakage. The embankment is generally affected by tidal variation and has low resistivity characteristics due to the high saturation of seawater. For this reason, SP monitoring and the pole-pole array resistivity surveys, which are relatively more effective to the conductive media, were carried out to delineate the leakage zones of sea water through the embankment. We checked out electrical conductivity (EC) and temperature variations along the inner part of Youngsan estuary dam to detect the zone of seawater leakage and found that the measured EC value agreed to that of seawater in the leakage zone and the temperature was lower than that of the vicinity of leakage zone. SP monitoring results were coincided with tidal variations at each embankment. At the leakage zones in the Youngsan estuary dam and the Eoeun embankment, SP anomalies are in the range of -60~-85 mV and -20~-50 mV, respectively, and true resistivity values obtained by 2-D inversion are 3~15 ohm-m and below 0.3 ohm-m, respectively. Both SP monitoring and the pole-pole array resistivity method are found to be quite effective for investigation of seawater leakage zones in the embankment.

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도서지역 지하수 장기관측자료를 이용한 해수침투 사례분석

  • 김진호;송성호;이규상;설민구
    • Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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    • 2003.04a
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    • pp.172-175
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    • 2003
  • 우리나라 서남해 도서지역의 암반대수층을 통한 해수침투 실태 파악과 합리적인 지하수 이용관리 계획을 수립하기 위하여 농림부와 농업기반공사가 운영중인 해수침투 관측망에 대한 대략적인 소개와 일부 지역의 운영 사례를 제시하였다. 강화도 숭뇌지역 운영사례에서는 2002년 1월 1일부터 11월 30일까지의 수위, 전기전도도, 수온 등 세 항목의 지하수 장기관측 결과와 전기전도도 검층, 변형된 단극배열 전기비저항 탐사 및 지하수 시료들의 이온분석 결과를 바탕으로 관측정의 해수유입 실태를 파악하였으며, 소유역에 대한 개략적인 해수침투 유형파악이 가능함을 확인하였다.

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Resistivity Tomography in an Inclined Borehole to Surface Purvey Using a Pole-dipole Array (단극-쌍극자 배열을 이용한 경사시추공-지표 탐사에서 전기비저항 토모그래피)

  • Park Jong-Oh;Kim Hee-Joon;Park Chung-Hwa
    • The Journal of Engineering Geology
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    • v.16 no.3 s.49
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    • pp.255-263
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    • 2006
  • In an electrical tomographic survey using an inclined borehole with a pole-dipole array, we must consider several factors: a singular point associated with zero potential difference, a spatial discrepancy between electrode and nodal point in a model due to a inclined borehole, and a variation of geometric factors in connection with a irregular topography. Singular points which are represented by the normal distance from current source to the ground surface can be represented by serveral regions due to a irregular topography of ground surface. The method of element division can be applied to the region in which the borehole is curved, inclined or the distance between the electrodes is shorter than that of nodal points, because the coordinate of each electrode cannot be assigned directly to the nodal point if several electrodes are in an element. Test on a three-dimensional (3-D) synthetic model produces good images of conductive target and shoves stable convergence.