• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.281-281
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• 2015

Shallow landslide often occurs in areas of this topography where subsurface soil water flow paths give rise to excess pore-water pressures downslope. Recent hillslope hydrology studies have shown that subsurface topography has a strong impact in controlling the connectivity of saturated areas at the soil-bedrock interface. In this study, the physically based SHALSTAB model was used to evaluate the effects of three soil thicknesses (i.e. average soil layer, soil thickness to weathered soil and soil thickness to bedrock soil layer) and subsurface flow reflecting three soil thicknesses on shallow landslide prediction accuracy. Three digital elevation models (DEMs; i.e. ground surface, weathered surface and bedrock surface) and three soil thicknesses (average soil thickness, soil thickness to weathered rock and soil thickness to bedrock) at a small hillslope site in Jinbu, Kangwon Prefecture, eastern part of the Korean Peninsula, were considered. Each prediction result simulated with the SHALSTAB model was evaluated by receiver operating characteristic (ROC) analysis for modelling accuracy. The results of the ROC analysis for shallow landslide prediction using the ground surface DEM (GSTO), the weathered surface DEM and the bedrock surface DEM (BSTO) indicated that the prediction accuracy was higher using flow accumulation by the BSTO and weathered soil thickness compared to results. These results imply that 1) the effect of subsurface flow by BSTO on shallow landslide prediction especially could be larger than the effects of topography by GSTO, and 2) the effect of weathered soil thickness could be larger than the effects of average soil thickness and bedrock soil thickness on shallow landslide prediction. Therefore, we suggest that using BSTO dem and weathered soil layer can improve the accuracy of shallow landslide prediction, which should contribute to more accurately predicting shallow landslides.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2000.05a
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• pp.71-71
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• 2000

• Spatial Information Research
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• v.11 no.3
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• pp.203-212
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• 2003

An integrated 3D GIS-based approach for understanding underground environment is proposed and applied to a land subsidence in densely populated region. Bedrock and geological discontinues were treated as main factors in this study. Because land subsidence in this study area was caused by cavity owing to dissolved limestone in percolating ground water. Ground was classified according to bedrock types using a clustering method and geological information, N value, and RQD value of boreholes were visualized and integrated by 3D-GIS. Therefore it was possible to recognize underground space easily and analyze the ground information effectively.

• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.1134-1139
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• 2005

Seismic motion amplification owing to the input motion level at bedrock is one of the important topics to understand various geomaterials behavior. The extremely valuable borehole records at Port Island were obtained during the 1995 Hyogoken Nanbu Earthquake and also before and after the main event. In this study, the seismic motion amplification at the soft reclaimed ground was discussed. Comparison of measured records with numerical simulation results were made with focus on seismic motion amplification characteristics at the soft reclaimed ground.

• Economic and Environmental Geology
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• v.1 no.1
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• pp.70-73
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• 1968

In Korea, ground water exploration by the electric method as a major prospecting tool has been carried out mainly in alluvial deposits, So it is considered to be important to understand the principle concerning the electrical and hydrological properties of alluvium. Factors which affect on the electrical and hydrological properties of alluvium were investigated. Major elements in ground water exploration are porosity and dermeability for most alluvial deposits with exceptions in some particular areas. Much water yield can be expected where alluvial materials have large porosity and small particle size while large particle size in necessary for good permeability. Problem is to locate the points which have comparatively large porosity and good permeability at a time. It is known that electrical resistivity method is proved useful to solve the above problem. The conclusion is: Localities which have greater alluvium thickness(7 to 10m) and 200 to 500 ohm -m of real resistivity value are suitable for well site in alluvial deposits in Korea where alluvium thickness is comparatively small(less than 10m in generaa) and bedrock formations are mainly composed of granite gneiss and granite.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.10a
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• pp.70-86
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• 2003

Despite its usability, TCE has been managed as a hazardous material due to the toxicity and many contamination cases were surveyed in some developed countries. U.S.EPA(Kram et al., 2001) suggested DNAPL characterization methods and approaches based on survey experiences at several sites. However, Korea has not the least assessment of contamination and trial of remediation, although there are a lot of doubtable areas where ground water would be contaminated with TCE. In this study, we try to assess the volume and extent of ground water contamination with TCE and delineate the contamination source zones in an industrial area. Ground water in this area flows through fractures and the contaminant TCE has the properties of high volatility, high density and low partitioning to soil material. Thus, we applied a variety of technical approaches to identify the contamination status; documentary, hydrogeochemical, hydrogeological and geological surveys. In addition, additional survey was performed based on the interim findings, which showed that ground water contamination was limited to the relatively small area with high concentrations to the deep place. The contamination source zone is estimated to be the asphalt test institute where a great deal of TCE has been used to analyze the amount of asphalt soluble in TCE since 1984. Based on the contamination characterization and a myriad of documents about ground water remediation, appropriate site remediation management options will be recommended later. This study is now under way and this paper was focused on describing the technical approaches used to achieve the goals of this study.

• Korean Journal of Agricultural Science
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• v.6 no.2
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• pp.125-133
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• 1979

The characteristics of landslides occurred in August 5, 1979 in pyeongchangkun were surveyed and indentified as follows. 1. Deep limestone regions. Distinct differences in soil texture between A1 and B horizon could be observed on soil profile, which is attributed to the clay illuviation. The clay illuvial horizon is supposed to be an important cause of large scale mudflows on middle slopes by the lubricant action of ground water flowing between top soil and subsoil. 2. Shallow limestone regions. Very shallow top soils (less than 50cm) laid on tilted bedrock stratification provide a proper condition of mass soil movement if the top soil is saturated and ground water flows between top soil and bedrock when concentrated heavy rainfalls shower. 3. Granite regions. Weathering granitic bedrock produces very coarse textured top soils which are very cohesionless and have many pores. Therefore, the soil has high infiltration ratio and is easy to be saturated by water and to be detached from the bedrock. The landslides abrase very severely both sides of gully with high potential energy when they flow down. The following methods for landslide prevention can be recommended. 1. The original parts of landslides on top of the gully must be treated by intensive planting of deep rooting species and check dams. 2. Clear-cutting and crop planting on steep slope (more than 25 degrees) should be controlled and prohibited. 3. Establishment of landslide prevention forest should be practised on proper site.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2005.04a
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• pp.429-432
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• 2005

Geophysical investigations, as a non-invasive method, were conducted at the former gas station site contaminated with fuel hydrocarbons. GPR (Ground Penetrating Radar) survey was performed to locate buried objects such as USTs (Underground Storage Tanks) and fuel pipes which might serve as a origin of the site contamination. Additional GPR investigation and a resistivity survey were conducted to map water table and to characterize shallow geologic structures of the site. The results of the study have shown that seven USTs including one unknown UST and buried fuel pipes are present, and that the groundwater elevation varies with topography from approximately 1.5 to 3m below the surface and the water table is located in the residual soils above the bedrock in the site. The results also show that the geophysical methods can be a very useful tool for the characterization of the contaminated site.

• The Journal of Engineering Geology
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• v.27 no.2
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• pp.153-164
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• 2017

The geological factors for causing ground subsidence are very diverse. It can be affected by any geological or extrinsic influences, and even within the same geological factor, the soil depression impact factor can be determined by different physical properties. As a result of reviewing a large number of papers and case histories, it can be seen that there are seven categories of ground subsidence factors. The depth and thickness of the overburden can affect the subsidence depending on the existence of the cavity, whereas the depth and orientation of the boundary between soil and rock are dominant factors in the ground composed of soil and rock. In case of soil layers, more various influencing factors exist such as type of soil, shear strength, relative density and degree of compaction, dry unit weight, water content, and liquid limit. The type of rock, distance from the main fracture and RQD can be influential factors in the bedrock. When approaching from the hydrogeological point of view, the rainfall intensity, the distance and the depth from the main channel, the coefficient of permeability and fluctuation of ground water level can influence to ground subsidence. It is also possible that the ground subsidence can be affected by external factors such as the depth of excavation and distance from the earth retaining wall, groundwater treatment methods at excavation work, and existence of artificial facilities such as sewer pipes. It is estimated that to evaluate the ground subsidence factor during the construction of underground structures in urban areas will be essential. It is expected that ground subsidence factors examined in this study will contribute for the reliable evaluation of the ground subsidence risk.

• The Journal of Engineering Geology
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• v.17 no.4
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• pp.517-523
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• 2007

Geophysical surveys(seismic refraction, electrical resistivity, and ground penetrating radar) were performed to delineate the weathering zone associated with vadose water in Chojeong area and investigate the fault related fracture zones. On the basis of seismic velocity structures, weathering layer for the southwestern part is interpreted to be deeper than for the northeastern part. The depth to bedrock(i.e., thickness of weathered zone) from seismic refraction data attempted to be correlated with drill-core data and groundwater level. As for the investigation of geological discontinuities such as fault related fracture zone, seismic refraction, electrical resistivity, and ground penetrating data are compositely employed in terms of velocity and resistivity structures for mapping of surface boundary of the discontinuities up to shallow depth. Surface boundaries of fracture zone are well indicated in seismic velocity and electrical resistivity structures. Accurate estimation of weathered zone and fracture zone can be successfully available for mapping of attitude of vadose water layer.