• 한국지구물리탐사학회:학술대회논문집
• /
• 2007.06a
• /
• pp.179-184
• /
• 2007

The electrical resistivity method has been widely used for the efficient maintenance of tunnel. In this case, the main purpose of the survey is to find out resistivity distribution around the tunnel. However, resistivity data are severely distorted by the tunnel, which make it hard to detect anomalous zones developed around the tunnel. In this study, using the finite element modeling, we analyze resistivity data distorted by the tunnel. Finally, we propose a simple method to correct the tunnel effect.

• Journal of international Conference on Electrical Machines and Systems
• /
• v.2 no.1
• /
• pp.45-50
• /
• 2013

This paper presents design of induction motor in very low temperature for LNG main cargo pump and comparison of two motors. One is the motor for using in room temperature and another is the motor for using very low temperature. This paper designs with Equivalent circuit Method and uses Finite Element Method to analysis. The motor for very low temperature considers variation of coil resistivity due to temperature change and compare torque characteristic with the motor for room temperature. Design element of motor for very low temperature considers resistivity variation following temperature change on going through this paper. The result shows that two types of motors are almost same torque curve characteristic even though they are not the same environment.

• Computers and Concrete
• /
• v.23 no.6
• /
• pp.399-408
• /
• 2019

Structural health monitoring is important for the safety of lives and asset management. In this study, numerical models were developed for the piezoresistive behavior of smart concrete based on finite element (FE) method. Finite element models were calibrated with experimental data collected from compression test. The compression test was performed on smart concrete cube specimens with 75 mm dimensions. Smart concrete was made of cement CEM II 42.5 R, silica fume, fine and coarse crushed limestone aggregates, brass fibers and plasticizer. During the compression test, electrical resistance change and compressive strain measurements were conducted simultaneously. Smart concrete had a strong linear relationship between strain and electrical resistance change due to its piezoresistive function. The piezoresistivity of the smart concrete was modeled by FE method. Twenty-noded solid brick elements were used to model the smart concrete specimens in the finite element platform of Ansys. The numerical results were determined for strain induced resistivity change. The electrical resistivity of simulated smart concrete decreased with applied strain, as found in experimental investigation. The numerical findings are in good agreement with the experimental results.

• 한국지구물리탐사학회:학술대회논문집
• /
• 2003.11a
• /
• pp.362-369
• /
• 2003

A infiltration experiment of river water has been conducted to evaluate the applicability of electrical resistivity monitoring methods in an area containing gravelly deposits in Nagaoka, Japan. Apparent resistivity data, which are inverted to obtain the resistivity distribution, are measured with a newly developed system. This system can collect 490 data in an hour and be controlled with PC to store the data. Subsurface resistivity sections, which are obtained from two-dimensional nonlinear inversion of time-lapse apparent resistivity data, enable us to estimate the direction of the flow and the rate of infiltration. The infiltration rate is estimated to be $4.4{\times}10^4m/s$ in the early stage of the experiment when the infiltration process is dominant.

• Economic and Environmental Geology
• /
• v.33 no.5
• /
• pp.417-424
• /
• 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.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.62 no.4
• /
• pp.186-191
• /
• 2013

Earth equipments are essential to protect ITS facilities from abnormal situation. In this research, an estimation algorithm of earth parameters and equivalent resistivity is introduced. Traditional estimation methods can be divided into graphic method and numerical method. The result of graphic method is varied by the ability of expert or repeated calculation and it is hard to estimate the parameters precisely. The numerical method requires special techniques such as optimizing theory, and numerous calculations, whose results can be varied with initial values. The proposed algorithm is based on the relationship between apparent resistances and earth parameters and approximates the nonlinear characteristics of earth using ANN(artificial neural networks). The effectiveness of proposed method is verified in case studies.

• Journal of Korea Soil Environment Society
• /
• v.1 no.1
• /
• pp.29-38
• /
• 1996

Among many geophysical prospecting methods, GPR(Ground Penetration Radar) and electrical resistivity method have been applied to a open waste dumping landfill for measuring of the site area and depth. The surveying was limited to a boarder of the site and inside area because of the field situation. The data of GPR were recorded by 50MHz antenna, and dipole array was used for electrical resistivity survey in the same survey line for the integrated interpretation. The result of GPR clearly indicated the horizontal boarder of site. However, the data of GPR did not have enough to measure the depth of site clearly. The electrical resistivity method may show the effective information by integrated interpreation. These results coincided with results of the boring test. Therefore, a combination of GPR and electrical resistivity is a good method for surveying of suspective open waste dumping landfill area and it's depth.

• Geomechanics and Engineering
• /
• v.20 no.6
• /
• pp.475-484
• /
• 2020

The prediction of the ground conditions ahead of a tunnel face is very important, especially for tunnel boring machine (TBM) tunneling, because encountering unexpected anomalies during tunnel excavation can cause a considerable loss of time and money. Several prediction techniques, such as BEAM, TSP, and GPR, have been suggested. However, these methods have various shortcomings, such as low accuracy and low resolution. Most studies on electrical resistivity tomography surveys have been conducted using numerical simulation programs, but laboratory experiments were just a few. Furthermore, most studies of scaled model tests on electrical resistivity tomography were conducted only on the ground surface, which is a different environment as compared to that of mechanized tunneling. This study performed a laboratory experimental test to extend and verify a prediction method proposed by Lee et al., which used electrical resistivity tomography to predict the ground conditions ahead of a tunnel face in TBM tunneling environments. The results showed that the modified dipole-dipole array is better than the other arrays in terms of predicting the location and shape of the anomalies ahead of the tunnel face. Having longer upper and lower borehole lengths led to better accuracy of the survey. However, the number and length of boreholes should be properly controlled according to the field environments in practice. Finally, a modified and verified technique to predict the ground conditions ahead of a tunnel face during TBM tunneling is proposed.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.48 no.2
• /
• pp.49-55
• /
• 1999

This paper proposes an efficient 2D Finite Element Method(FEM) taking into account the end-ring of three phase squirrel-cage induction motors. The parameters of the squirrel-cage induction motor such as conductivity of secondary conductor have an effect on the characteristics of a motor. Especially, if the characteristic analysis is done without considering the end-ring, the good results can not be obtained. Therefore, we calculated a new resistivity of the secondary conductor including the end-ring's resistance to apply the 2D FEM. Then, the performances of the motors are analyzed by using the new resistivity of secondary conductor which contains the end-ring resistivity. The validity of the proposed method is verified by comparing the numerical results with experimental ones.

• Geophysics and Geophysical Exploration
• /
• v.4 no.4
• /
• pp.124-132
• /
• 2001

Electrical resistivity survey has been conducted for delineating geological fault structure in Kaekok-ri near Kyungju. In general, electrical resistivity survey has an advantage of searching buried faults and its traces compared with other geophysical survey methods. Distribution of electrical conductivity in the ground is influenced by the ratio of pores, groundwater and clay minerals. These properties are evidenced indirectly to explain for weathering condition, faults and fracture Bones. Thus the electrical resistivity survey can be an effective method to find buried faults. We have carried out two dimensional (2-D) interpretation by means of smoothness-constrained least-squares and finite element method. Field data used in this paper was acquired at Kaekok-ri, Wuedong-eup, Kyungju-si, where is Ulsan Fault and is close to the region in which debatable quaternary fault traces were found recently. The dipole-dipole array resistivity survey which could show the 2-D subsurface electrical resistivity structure, was carried out in the area with three lines. The results showed good property of fault, fracture zone and fault traces which we estimated were congruous with the results. Through this study, 2-D electrical resistivity survey interpretation for fault is useful to apply.