• Geophysics and Geophysical Exploration
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• v.11 no.4
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• pp.368-372
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• 2008

This study evaluates the usefulness and capability of surface electrical resistivity technique for identifying the weak zones or subsurface cavities in karst area with limestone formation. Weak zones or cavities near surface can be potentially dangerous and several problems are associated with collapse of roads or buildings accompanied by subsidence phenomena. In this paper, both two and three dimensional resistivity investigation were conducted to investigate subsidence along a road in Yongweol-ri, Muan-gun, South Korea. The results of the resistivity survey using dipole-dipole array provide a clear view of the weathered regolith, the distribution of weak zones or cavities and bedrock. Several low resistivity areas were identified and subsequent drilling led to the discovery of several weak zone or clay-filled underground cavities. The drilling results show excellent correlation with the resistivity images. It is illustrated, the ability of electrical technique to produce high resolution images of subsurface, which are useful for subsidence assessment. Also the results of this study have demonstrated that two and three dimensional electrical resistivity surveys are useful for delineating the subsidence area. Based on resistivity imaging, the map of hazardous zone has been developed.

• The Journal of Engineering Geology
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• v.30 no.3
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• pp.289-302
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• 2020

To determine the shallow subsurface structure and sliding surface of land creeping in 2016 at Hadong-gun, Gyeongsangnam-do, geophysical surveys (electric resistivity, and refraction seismic methods, borehole televiewer) and slope stability analysis were conducted. The subsurface structure delineated with borehole lithologies and seismic velocity structures provided the information that the sediment layer on the top of the slope was rather as thick as 20 m and the underlying weathered rock (anorthosite) was thinner than 1 m. Based on the tension cracks observed during the geological mapping, televiewer scanning was performed at the borehole BH-2 and detected the intensive fracture zones at the ground-water level, associated with the slip weak zones mapped in dipole-dipole electrical resistivity section. Downslope sliding and slightly upward pushing at the apex of high resistive bedrock explains the curved slip plane of the land creeping. Such a convex structure might play a role of natural toe abutment for preventing the downward development of slip weak zones. In slope stability analysis, the safety factors of the slip weak zone are calculated with varying the groundwater levels for dry and rainy seasons and the downslope is founded to be unstable with safety factor of 0.89 due to fully saturated material in rainy season.

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

• Journal of the Korean earth science society
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• v.26 no.5
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• pp.436-442
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• 2005

We have performed multiple geophysical surveys comprised of gravity, magnetic and resistivity methods at the Yangsan fault zone which runs through the Eonyang area, the eastern part of Kyeongsang in southeast Korea. The gravity and magnetic data provide information about geological structures. Furthermore, sections of electrical resistivity show the sharp contrast of electrical resistivity distribution across the fault zone. Since the fractured zone tends to be more conductive than fresh host rocks, the electrical resistivity survey is effective in determining the detailed structure of the fault zone. We have made gravity measurements at a total of 71 points alongside two profiles across the fault zone, and carried out an electrical resistivity survey with a dipole-dipole array at the same location using 40m dipole length. In addition, we have analyzed the aeromagnetic data on the corresponding area. The multiple geophysical properties appear to be abruptly changed in electrical resistivity, gravity and aeromagneticclearly show the different appearance across the fault zone. The fault is identified by its sub vertical attitude which is well known in the Yangsan fault zone. We have also confirmed that the magnitude of the response of the fault is much larger in the southern part of the survey area than the northern area. These results most likely to provide basic information for the further studies about the physical properties and the structures at the Yangsan fault.

• Geophysics and Geophysical Exploration
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• v.12 no.3
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• pp.239-245
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• 2009

To verify the reinforcing effect of grouting materials composed of colloid cement and ordinary portland cement on the water leakage region in a small scale dike, we performed a tubecasing method and applied surface electrical resistivity survey including electrical resistivity tomography (ERT) to find resistivity variation before and after grouting. Hydraulic conductivities after grouting show 10 times lower than those of before grouting. These variation indicates that the cement grout blocks the leakage pathway effectively. As the results of dipole-dipole resistivity survey along the dike, resistivity distribution after grouting did not represent noticeable spatial variation in time. Resistivity monitoring results at the dike with vertical electrical sounding (VES) showed that the region of decreasing apparent resistivity was occupied by the grout after grouting. Predicted resistivities from the inversion of ERT data well matched with results of VES at the same regions. From the ERT using check holes to inspect the effect of grouting, we could find that the ERT is quite effective to identify spatially the grout region in a dike.

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

• The Journal of Engineering Geology
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• v.15 no.1
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• pp.19-27
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• 2005

The Sambo mine is located in Hae-je Myeon, Moo-an Gun, Chollanamdo, which consists of host gneiss and rhyolite possessing quartzite veins with other compositions such as gold, silver, and sublimated sulfur. The ore grade estimated from the core was 0.05～10.9g/t or less in gold and 0.05～389g/t or less in silver, indicating a partial mineralization. The purpose of this paper is to understand the subsurface structures and the distribution of mineralized bodies in the Sambo mine using a combined method of Schlumberger, Wenner, and Dipole-di-pole resistivity surveys on the surface and the resistivity tomography survey in boreholes. The result of three-dimensional resistivity inversion showed that the mineralized body is extended to 240m long in the N10°～20°E direction, with 30m wide and 80 m thick from the surface. The low resistivity zones (<1,000ohm-m) determined from the resistivity image were in good agreement with the mineralized bodies and weak zones identified from the logged cores.

• Economic and Environmental Geology
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• v.35 no.2
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• pp.155-162
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• 2002

There are many typical epithermal deposits scattering in the Taran of central Kalimantan. Indonesia. To get the shallow geological information, we carried out the geophysical exploration: spontaneous potential survey, in-suite magnetic susceptibility measurement and relistivity survey method in this area for a few weeks from September 30th to October 27th in 1997. SP survey (Fluke 27 multimeter)/magnetic susceptibility (EK -7 meter) measurement was carried out with a 250m$\times$10m lattice net in N45$^{\circ}$W direction. The dipole-dipole array resistivity survey was conducted with an electrode spacing of ${\alpha}$=30 m and electrode separation index n=7 at the line 5. The result shows that was the gold bearing quartz vein area can be divided into two type lone: low sulfidation type and high sulfidation type zone. The low resistivity value in the survey line 5 indicated a fracture Bone associated with the high sulfidation zone.

• The Journal of Engineering Geology
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• v.30 no.4
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• pp.525-539
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• 2020

A site containing buried solid waste and treated water and oil storage containers from a leather manufacturing plant was studied through soil and groundwater pollution and electrical resistivity surveys with the aim of identifying areas polluted by leachate generated by landfilling with leather waste and leakage wastewater. It was found that TPH and Zn exceeded environmental standards for soil pollution and, for leachate and groundwater, Cr(VI) concentrations exceeded standard levels for groundwater quality. An electrical resistivity survey was used to elucidate soil and groundwater pollution characteristics and diffusion pathways. Ten survey lines were set up with an electrode spacing of 5 m in a dipole-dipole array. The hydraulic characteristics of soil determined by groundwater contamination surveys matched well the low-resistivity-anomaly zones. Electrical resistivity surveys of areas containing contaminated soil and groundwater that have irregular strata due to waste reclamation are thus useful in highlighting vertical and horizontal pollutant diffusion pathways and in monitoring contaminated and potentially contaminated areas.

• Geophysics and Geophysical Exploration
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• v.24 no.4
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• pp.139-148
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• 2021

Negative apparent chargeability data in time-domain induced polarization (IP) survey are very often considered as noise and rejected before the inversion stage. Negative IP data can, however, occur naturally as a consequence of the distribution of chargeable zones in the ground. In some cases, the negative apparent chargeability values may account for most of the data measured. Negative IP data are caused by the geometry of chargeable zones and electrode positions. Negative apparent chargeability data appear most frequently when a dipole-dipole array is used. In this study, the effect of negative apparent chargeability data on inversion results is analyzed through the numerical 2D time-domain IP modeling and nonlinear inversion. The results demonstrate clearly that negative apparent chargeability data have to be included in the inversion as they contain important information on the distribution of subsurface chargeability.