• Geophysics and Geophysical Exploration
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• v.24 no.3
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• pp.73-77
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• 2021

Induced polarization (IP) is useful for mineral exploration and hydrogeological studies by visualizing the electrochemical reactions at the interface between polarized minerals and groundwater. Frequency-domain IP (FDIP) is not actively applied to field surveys because it takes longer to acquire data, despite its higher data quality than conventional time-domain IP. However, data quality is more important in current mineral exploration as the targets gradually shift to deep or low-grade ore bodies. In addition, the measurement time reduced by automated instrumentation increases the potential for FDIP field applications. Therefore, we demonstrate that FDIP can detect mineral exploration targets by performing geophysical logging in the boreholes of a skarn deposit, in South Korea. Alternating current (AC) resistivity, percent frequency effect (PFE) and metal factor (MF) were calculated from impedance values obtained at two different frequencies. Skarn zones containing magnetite or pyrite showed relatively low AC resistivity, high PFE, and high MF compared to other zones. Therefore, FDIP surveys are considered to be useful for mineral exploration.

• Tunnel and Underground Space
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• v.33 no.6
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• pp.483-494
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• 2023

Measurement of the physical properties of rocks or minerals is an important factor in determining the distribution of the underground medium as well as mineral resource investigations. Resistivity and induced polarization, which are widely used in Korea, are methods for measuring electrical properties, which are representative properties of obtaining subsurface information. In order to precisely analyze the exploration data obtained from various sites, it is important to accurately measure the material properties. Electrical properties of rock is measured using two-electrode or four-electrode method. Compared to the four-electrode method, the two-electrode method is generally used because it is very easy to contact the sample and the electrode, but there is a problem in that the impedance of the electrode and the sample is measured together. In this study, the time-domain the induced polarization effects were measured using the 2-electrode method and the 4-electrode method for artificial samples mixed with graphite and cement having induced polarization characteristics, and the results were compared. Although the 4-electrode method has difficulties in installing potential electrodes, it was confirmed that it is effective in measuring electrical properties because it can reduce the problem caused by the impedance of potential electrodes compared to the 2-electrode method.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.2
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• pp.75-81
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• 2010

In this study, when concrete properties are changed by concrete mix proportions or blending of admixtures, the characteristics of electro-chemical method for corrosion assessment of the embedded steel are compared and its causes are analyzed. According to the results, when the ratio of corroding area was less than 10%, the half-cell method was affected by concrete properties. In the case of specimen blended admixtures, it is possible to assess the high-corroded steel qualitatively using the half-cell method. For the polarization resistance method, though the corroding area was less than 10%, it has not affected by concrete properties. However, in case of specimen blended admixtures, the corrosion level of steel was underestimated than OPC specimens having a similar corroding area.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.2
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• pp.331-337
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• 1994

The scatting problem by E-polarized plane wave with obique incidence on a tapered resistive strip grating with zero resistivity(perfectly conducting) at strip-edges is analyzed by the method of moments in the spectral domain. Then the induced surface current density on the strip is expanded in a series of Chebyshev polynomials of the second kind. The expasion coefficients are calculated numerically in the spectral domain, the numerical results of the geometric-optical reflection coefficient for the tapered resistivity in this paper are compared with those for the existing uniform resistivity. And the position of sharp variation points in the magnitude of the geometric-optical reflection coefficient can be moved by varying the incident angle and the strip spacing, It is found out that these sparp variation points are due to the transition of higher mode between the propagation mode and the evanescent mode.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.688-693
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• 2000

Recently great efforts and investment have been made in order to evaluate concrete durability by steel corrosion. But most of study is relatively or qualitatively estimated, therefore it has a great limitation in evaluating a remaining service life of concrete. In this research, steel corrosion rate was measured quantitatively by polarization resistance method and multi-regressed considering chloride, carbonation, coverage depth, relative humidity, W/C, and the use of deicing salts. And a half cell potential method was used at th same time for the purpose of comparing with polarization resistance method.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 1999.05a
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• pp.45-45
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• 1999

일반 구조용 탄소강은 수용액 중에 노출될 때 부식에 의한 손상을 받기 쉽다. 부식의 양지를 위한 방법으로 사용 매체 중에 부식억제제를 첨가하여 탄소강의 부식속도를 낮추는 방법은 흔히 사용되는 방법이다. 부식억제제는 부식억제의 원리에 따라 양극부식억제제, 음극부식억제제 그리 고 이들의 혼합부삭억 세제 둥 여러 종류가 목적에 따라 사용되고 있다. 일반적으로 부식억제제의 성능 평가에는 무게감량볍, 표면분석법, 분극거동측정, 부석전위, 선 형분극법에 의한 부식속도 측정 등 다양한 방법이 시도되고 있다. 이 중에서 전기화학적 평가볍 은 부삭억제제의 작용 기구 규명 등을 위하여 많이 사용되고 있다. 한편 제품의 개발 단계에서 실질적인 평가법으로 갈리 사용하고 있는 방법은 무게 감량법인데 이 방법은 전면부식에 의한 금 속 손실량을 측정하여 부식억제능을 측정하는 방법이다. 그러냐 실제로 부삭억제제가 사용되고 있는 환경에서의 부식양상을 판찰하여보면 전면부식에 의한 손상보다는 국부부식에 의한 손상이 보다 치명적언 경우를 종종 목격할 수 있다. 이러한 관점에서 가존의 무게감량법은 한계가 있다. 따라서 본 연구에서는 이러한 국부부식을 보다 효과적으로 평가하기 위해 새로운 시험법을 도 입 상용 부식억제제의 종류별로 비교하였다. 부식억제제로는 수용액 중의 부식억제제로 널리 사용되고 있는 Nalco 39L과 본 연구실에서 SK해미칼과 공동 개발한 GH-110 등에 대하여 MCA(Multiple Crevice Assembly)를 이용 틈부식 저항성을 평가하였다. 또한 박막화된 전기저항형 부석속도 측정 센서를 틈부식 형태의 부식측정 에 적용하는 연구를 행하였다. 시험에 사용한 재갚는 천연가스의 감압 온도보상용으로 운전하는 가스히터의 주 구성 재료인 저탄소강을 사용하였으며 열화된 부식억제제 용액으로 사용기간이 서로 다른 수용액들에 대하여 평가 방법을 적용하여 비교하였다 다양한 부식억 제 제 수용액을 비교한 결과 MCA(Multiple Crevice Assembly)를 이용한 틈부식 억제능 시험은 실제 현장 사험 결과와 어느 정도 일치하는 결과를 보였다. 새로운 틈부식 저항성 측정법으로 시도한 철박막을 이용 틈부식 측정법은 육안 검사를 실시하지 않고도 틈부식의 전행 여부를 확인할 수 있는 가능성을 확인하였다.

• Geophysics and Geophysical Exploration
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• v.20 no.2
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• pp.100-113
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• 2017

Induced polarization (IP) method is based on the measurement of a polarization effect known as overvoltage of the ground. IP techniques have been usually used to find mineral deposits, however, nowadays widely applied to hydrogeological investigations, surveys of groundwater pollution and foundation studies on construction sites. IP surveys can be classified by its source type, i.e., time-domain IP estimating chargeability, frequency-domain IP measuring frequency effect (FE), and complex resistivity (CR) and spectral IP (SIP) measuring complex resistivity. Recently, electromagnetic-based IP has been studied to avoid the requirement for spike electrodes to be placed in the ground. In order to understand IP methods in this study, we: 1) classify IP surveys by source type and measured data and illustrate their basic theories, 2) describe historical development of each IP forward modeling and inversion algorithm, and finally 3) introduce various case studies of IP measurements.

• Geophysics and Geophysical Exploration
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• v.24 no.4
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• pp.164-170
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• 2021

Frequency-domain and time-domain induced polarization methods can provide spectral information about subsurface media. Analysis of spectral characteristics has been studied mainly in the frequency-domain, however, time-domain induced polarization research has recently become popular. In this study, assuming a homogeneous half-space model, an inversion method was developed to extract Cole-Cole parameters from the measured secondary potential or electrical resistivity. Since the Cole-Cole parameters of chargeability, time constant, and frequency index are not independent of each other, various problems, such as slow convergence rate, initial model problem, local minimum problem, and divergence, frequently occur when conventional nonlinear inversion is applied. In this study, we developed an effective inversion method using the initial model close to the true model by introducing a grid search method. Finally, the validity of the developed inversion method was verified using inversion experiments.

• Proceedings of the Korean Nuclear Society Conference
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• 1996.11b
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• pp.481-486
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• 1996

원자력 발전소의 증기 발생기 전열관으로 사용되는 합금 600MA는 미세 구조에 관계없이 가성 용액에서 입계 균열이 발생한다. 본 연구에서는 합금 600 2종과 합금 690 2종의 이음매없는 관 및 진공 용해한 합금 690M 2종의 MA 및 TT재에 대한 부식 조건의 변화에 응력 부식 균열 특성을 일정연신율법(CERT) 및 C-ring법으로 평가하였다. 가성 응력 부식 균열 저항성에 미치는 TT처리의 효과는 용액 조건에 관계없이 TT처리를 행하게 되면 응력 부식 균열에 대한 저항성이 증가하는 것으로 나타났으며, 분극 저항성과는 직접적인 관계가 나타나지 않고 다른 미세 조직 등에 의한 영향을 더 크게 받고 있는 것으로 판단된다. 가성 용액에서의 응력 부식 균열 저항성에 미치는 SO$_4$$^{=}$ 이온의 첨가 효과는 TT처리의 유무에 관계없이 응력 부식 균열 저항성을 크게 감소시키고 있다. 한편 합금 690의 가성 응력부식 균열 저항성에 미치는 Mo의 효과는 Mo이 첨가될수록 응력 부식 균열 저항성이 증가하는 것으로 나타났다.

• Geophysics and Geophysical Exploration
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• v.19 no.4
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• pp.212-219
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• 2016

The development of more advanced geophysical exploration techniques is necessary because the orebodies as yet discovered are increasingly changing in characteristics from shallow/high-grade to deep/low-grade. In this work, laboratory measurement of physical properties of rock samples and a field survey and interpretation of spectral induced polarization (SIP) have been conducted in a skarn metallic deposit, Gagok mine. The purpose of this study is that the applicability of SIP in the exploration of skarn metallic deposits is verified by the comprehensive interpretation between SIP characteristics of rocks obtained from the laboratory measurements and inverted survey results from the field data. In order to understand the SIP characteristics of each lithology, the data of eighty nine rock samples utilized in the previous studies were revaluated. The field survey was carried out using frequency of 0.25 Hz along a survey line designed for intersecting lithological boundaries and evaluating mineralized zones. The mineralized rocks were more conductive (low-resistivity) and capacitive (high-chargeability or strong-phase) than other rocks. Thus, SIP can be one of the very useful tools for the mineral exploration of the skarn deposits.