• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.9-12
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• 2002

The purpose of this study is to understand the high saline water phenomenon of Handong-ri area in the eastern coast of Jeju Island, were investigate the tidal effect of groundwater level, variation of electric conductivity and temperature, geological logging on the monitoring wells, chemical water quality, and ratios of oxygen istope of groundwater and seawater Results in investigating variation of interface zone of freshwater and saline water represented that the hyaloclastites formed at below groundwater table is developing toward the coast; this area consisted of stratum of good permeability. Hyaloclastites is presumed the main path of the high salinity water There are a lot of movement by the tide at upper layer. Salinity of lower layer spreads to upper up step in proportion to tidal energy. Because of hydrogeological characteristics, Interface zone of freshwater and saline water is made, High salinity of groundwater occur in east coastal area of Jeju Island. Therefore, I think that high saline groundwater phenomenon is natural condition by simple mixing.

• Geophysics and Geophysical Exploration
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• v.15 no.4
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• pp.219-226
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• 2012

This study provides an analysis on results of neutron logging for various borehole environments through numerical simulation based on a Monte Carlo N-Particle (MCNP) code developed and maintained by Los Alamos National Laboratory. MCNP is suitable for the simulation of neutron logging since the algorithm can simulate transport of nuclear particles in three-dimensional geometry. Rather than simulating a specific tool of a particular service company between many commercial neutron tools, we have constructed a generic thermal neutron tool characterizing commercial tools. This study makes calibration chart of the neutron logging tool for materials (e.g., limestone, sandstone and dolomite) with various porosities. Further, we provides correction charts for the generic neutron logging tool to analyze responses of the tool under various borehole conditions by considering brine-filled borehole fluid and void water, and presence of borehole fluid.

• Economic and Environmental Geology
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• v.43 no.3
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• pp.259-267
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• 2010

Resistivity logging instruments were designed to measure electrical resistivity of formation, which can be directly interpreted to provide water-saturation profile. Short and long normal logging measurements are made under groundwater level. In some investigation sites, groundwater level reaches to a depth of a few meters. It has come to attention that the proximity of groundwater level might distort short and long normal logging readings, when the measurements are made near groundwater level, owing to the proximity of an insulating air. This study investigates the effects of the proximity of groundwater level (and also the proximity of earth surface) on the normal by simulating normal logging measurements near groundwater level. In the simulation, we consider all the details of real logging situation, i.e., the presence of wellbore, the tool mandrel with current and potential electrodes, and currentreturn and reference-potential electrodes. We also model the air to include the earth’'s surface in the simulation rather than the customary choice of imposing a boundary condition. To obtain apparent resistivity, we compute the voltage, i.e., potential difference between monitoring and reference electrodes. For the simulation, we use a twodimensional, goal-oriented and high-order self-adaptive hp finite element refinement strategy (h denotes the element size and p the polynomial order of approximation within each element) to obtain accurate simulation results. Numerical results indicate that distortion on the normal logging is greater when the reference potential electrode is closer to the borehole and distortions on long normal logging are larger than those on short normal logging.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.139-145
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• 2010

An integrity testing for stone columns was attempted using crosshole S-wave logging. The method is conceptionally quite similar to the crosshole sonic logging (CSL) for drilled piers. The critical difference in the logging is the use of S-wave rather than P-wave, which is used in CSL, because swave is the only wave sensing the stiffness of slower unbounded materials than water. An electro-mechanical source, which can generate reversed Swave signals, was utilized in the logging. The stone column was delineated using the S-wave travel times across the stone column, the S-wave velocity profile of the crushed stone($V_{cs}$-profile) and that of surrounding soil($V_s$-profile). In the calculation of $V_{cs}$-profile of the crushed stone, its friction angle and Ko (coefficient of lateral earth pressure at rest) are recommended to be used. The calculation of the column diameter is not much affected by the values of friction angle and Ko.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.121-122
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• 2014

This study contemplated the descending air current from the smoke layers related to the smoke logging phenomenon in the sprinkler applied design for effective evacuation safety design. As a result, database on the average particle diameter, particle velocity and distribution of sprinkling was obtained and the relationship between the water amount and particle diameter was obtained. Also, in relation to descending air current, the movement of smoke layer to the bottom at the descending air current velocity of 0.6m/s was observed and stable descending air current was observed in existence of fire source over 100kW in size.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.693-696
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• 2005

KIGAM (Korea Institute of Geoscience and Mineral Resources) launched a new project to develop the low-temperature geothermal water in the area showing high geothermal anomaly, north of Pohang city, for large-scale space heating. Surface geologic and geophysical surveys including Landsat 1M image analysis, gravity, magnetic, Magnetotelluric (MT) and controlled-source audio-frequency MT (CSAMT), and self-potential (SP) methods have been conducted and the possible fracture zone was found that would serve as deeply connected geothermal water conduit. In 2004, two test wells of 1.1km and 1.5km depths have been drilled and various kinds of borehole survey including geophysical logging, pumping test, SP monitoring, core logging and sample analysis have followed. Temperature of geothermal water at the bottom of 1.5km borehole reached over $70^{\circ}C$ and the pumping test showed that the reservoir contained huge amount of geothermal water. Drilling for the production well of 2 km depth is on going. After test utilization and the feasibility study, geothermal water developed from the production well is going to be provided to nearby apartments.

• Korean Journal of Soil Science and Fertilizer
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• v.22 no.2
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• pp.146-155
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• 1989

A series of the experiments were conducted to evaluate the effects of the water-logging in continuous cropping soils of cucumber. Some of the results obtained from these experiments are summarized as follow: The values of pH in water-logged treatments were from 5.50 to 5.90. Those of EC were less than 0.3 mmhos/cm, were lower than those of control plot. The ratios of Ca/Mg, Ca/K, Mg/K respectively 2.5, 4.8, 2.0, were similar to the standard values. These changes were suitable for cucumber planting. And the number of bacteria among the microflora were determined increased from $10^6$ to $10^7\;cells/g$ dry soil, while that of the Fungi, Fusarium spp, Pythium spp, and Phythophthora spp decreased. In proportion to these changes of microflora, the ratios of B/F in water-logging plot were higher than in the control plot. The contents of Biomass-C were showed 10.47mg/100g soil to 36.12 mg/100g soil, and the contents of that in water-logging were more than in control plots.

• The Journal of Engineering Geology
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• v.12 no.3
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• pp.257-271
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• 2002

The vertical distribution of hydraulic conductivity of 3 boreholes located at Kongju National University was estimated by the ambient flow and the pump-induced flow measurements using a heat-pulse flowmeter. The ambient flow measurements showed that a great amount of groundwater (1~2 m$^3$/day) flowed in the boreholes through the conductive fractures. The analyzed conductivity profiles we similar to those of the packer test performed for the same boreholes. The conductive fractures in which the differential net flow changed greatly could be identified by the BIPS logging. The water-quality logging data showed that quality of groundwater changed abruptly at some depths of the boreholes. This change in water quality can be attributed to the presence of conductive fractures that have resulted in the mixing of groundwater of different quality flowing in different fracture channels. However, compared to the flowmeter test, the water-quality logging showed low capability in identifying locations of conductive fractures.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.2200-2204
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• 2009

In this paper the analysis of natural cause of Beijing Storm inundation and the effect of the human activities has been taken. Flood risk can hardly be eliminated solely by projects. Pre-warning system established is an efficient measure to minimize the influence of flood. Several main functions of this system and their examples are described in the paper, such as: monitoring, forecast, scheme, warning, dynamic decision-making and information publication.

• Geophysics and Geophysical Exploration
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• v.10 no.4
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• pp.353-360
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• 2007

We practiced fresh water injection test to identify its applibility as a method of seawater intrusion mitigation technique, and monitored the change of borehole fluid conductivity and the behavior of injected fresh water using borehole multichannel electrical conductivity monitoring and well-logging, and DC resistivity and SP monitoring at the surface. Well-logging and multichannel EC monitoring showed the decrease of fluid conductivity due to fresh water injection. We note that such an injection effect lasts more than several month which means the applibility of fresh water injection as a seawater intrusion control technique. Although SP monitoring did not show meaningful results because of weather condition during monitoring and the defects of electrodes due to long operation time, DC resistivity monitoring showed its effectiveness and applicability as a monitoring and assessment techniques of injection test by means of imaging the behavior and the front of fresh water body in terms of the increase of resistivity with reasonable resolution. In conclusion, we note that geophysical techniques can be an effective method of monitoring and evaluation of fresh water injection test, and expect that fresh water injection may be an practical method for the mitigation of seawater intrusion when applied with optimal design of injection well distribution and injection rate based on geophysical evaluation.