• Journal of Soil and Groundwater Environment
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• v.12 no.5
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• pp.98-104
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• 2007

A survey was performed to evaluate the distribution of radon concentrations in groundwater of South Korea. Groundwaters of 615 wells were sampled for this study during the four years from 1999 to 2002. The results showed radon values ranging from 4 pCi/L to 40,010 pCi/L with a mean and a median of 1,862 pCi/L and 920 pCi/L, respectively. The samples were classified into five groups according to the rock types; granite, sedimentary rocks, metamorphic rocks, Ogcheon metamorphic rocks, and Cheju volcanics. Mean radon concentrations were highest (2,595 pCi/L) in granites and lowest (238 pCi/L) in Cheju volcanic rocks. The groundwaters generally showed the highest radon content (2,298 pCi/L) in the weathered and the fractured bedrock complex and the lowest level (672 pCi/L) in the alluvium. The results showed that the radon concentrations in South Korea are low relative to those reported from other countries. But further investigations are suggested to confirm our results.

• Journal of Conservation Science
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• v.11 no.1 s.14
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• pp.1-14
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• 2002

After the construction (1398 year at first, secondarily reconstructed at 1448 year), the Soongryemoon (South Gate) had been preserved to late 19c without large damages. The present shape of the gate have been kept after the repairments of two times (1953, 1963). However, the rocks constituting the walls of the gate have been strongly weathered, exfoliated and cracked due to severe changes in the environment as traffic increase, air pollution and the subway which may seem also to cause the structural unstability. The rocks composed of the walls of the gate are almost of granites. On the rocks such deteriorations as onion structure, surface exfoliation, cracks, and edge breakout are developed. These deteriorations may be caused genetically by strong weathering, differential load due to possibly structural unstability, impact and unknown reasons. For the establishment of conservation plan, the factors of these deterioration phenomena and structural unstability must be quantitatively analyzed and diagnosed in detail.

• Conservation and Restoration of Cultural Heritage
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• v.1 no.1
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• pp.29-37
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• 2012

The West Stone Pagoda at Gameunsaji Temple Site constructed in the 7th century is mainly composed of dark grey dacitic tuff bearing small numerous dioritic xenoliths. These xenoliths resulted in small holes due to differential weathering process from the host rocks. Physical strength of the pagoda was decreased due to weathering and damage caused by petrological, biological and coastal environmental factors. The southeastern part of the pagoda was extremely deteriorated that the rock surface showed exfoliation, fracture, open cavity, granular decomposition of minerals and salt crystallization by seawater spray from the eastern coast. The stone blocks were intersected by numerous cracks and contaminated by subsequent material such as cement mortar and iron plates. Also, the pagoda was colonized by algae, fungi, lichen and bryophytes on the roof rock surface and the gaps between the blocks. As a result of ultrasonic test, the rock materials fell under Highly Weathered Grade (HW) or Completely Weathered Grade (CW). Thus, conservational intervention is essentially required to prevent further weakening of the rock materials.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.263-266
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• 2007

In this paper, analysis results on the failure of slope behind a Plant Complex of Gimhae due to typhoon Rusa in 2002 are introduced. The left side of the slope was reinforced by soil nails and the right side of the slope was going to construct slope reinforcement works. In the slope failure, the damage area is about $34,000m^2$, the lower width of slope failure is about 230m, the upper width of slope failure is about 50m, and the height of slope failure is about 120m. The elevation of a bedrock in the right side of the slope was lower than the left side of the slope. Due to the depth of weathered soils and weathered rocks in right side of the slope was thick, it will be expected that the effects of pore-water pressure during the rainfalls are large. For the analysis of the failure mechanism, 3-dimensional numerical analysis was carried out by FLAC-3D.

• Geotechnical Engineering
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• v.13 no.2
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• pp.101-124
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• 1997

Adjacent ground surface settlements by deep excavations are analyzed by field observations in the areas where excavations are performed in sandy soils or weathered soils underlain by rocks, First, the magnitude and the distribution of ground surface settlements, which are developed before main excavation activities (e. g., diaphragm wall installation and center pile installation) , are measured and analyzed. Secondly, the magnitude and the distribution of ground surface settlements by main excavation are measured and analyzed. And the results are compared with the predictions obtained by the empirical methods. Through case studies performed on the excavation sites where adjacent ground surfaces or structures are damaged by excavation activities, upper limit location of ground surface cracks are investigated.

• Journal of Korean Society of societal Security
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• v.2 no.4
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• pp.75-81
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• 2009

This paper presents the geotechnical characteristics of tunnel co \l apse based on the case studies. For domestic cases, most collapses are likely to happen along the weakest zone of shear strength due to the change of stresses induced by excavation specially when soft or weathered rock exist in front of a tunnel. In other words, the collapse of a tunnel occurs along the highly weathered fractured zone due to blasting and excavation. In Europe, collapses have been occurred by one joint group even though the ground is relatively fresh and for the rocks of which RQD is over 50%. In addition, the amount of ground water flow does not seem to be seriously affected by the RQD range.

• Journal of The Geomorphological Association of Korea
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• v.19 no.4
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• pp.39-57
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• 2012

The volcanic edifice of Ulleungdo is largely divided into a shield volcano underwater and a tholoide above seawater. The geological features of the volcano above seawater are basically alkali volcanic rocks that are further divided into five geological strata: agglomerates and tuffs trachyte and phonolite trachytic pumice trachyandesite, and sedimentary layer. The topography of Ulleungdo consists of volcanic landform on the whole, and such volcanic landform is weathered and eroded into various weathering landform, stream landform, coastal landform, structural landform, etc. Major volcanic topography includes caldera basin, central cone, and columnar joint, whereas weathering topography features, tafoni, gnamma, tor, weathered cave, talus, etc. In major coastal topography are sea cliff, wave-cut platform, sea stack, sea arch, sea cave, shingle beach, coastal terrace, etc. For stream topography, its development is minimal except for waterfalls.

• The Journal of Engineering Geology
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• v.21 no.3
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• pp.213-219
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• 2011

Transient/time-domain electromagnetic (TEM) soundings were carried out on reclaimed land, since the TEM sounding has good resolution of a conductive and thin overburden. The reclamation material is marine clay dredged from the seafloor, which is currently undergoing consolidation in the upper part of the dredged layer. The conductivity of the marine-origin clay is generally more than 0.3 S/m. The aim of the TEM sounding was to determine the depths of weathered and soft rocks overlain by thick and conductive overburden. The TEM responses were measured at delay times of 0.050-20.575 ms with a $30{\times}30$ m coincident loop array. Data from the TEM inversion and core logging indicate that the resistivities of the conductive overburden are less than 2 ${\Omega}$-m, while those of the weathered and soft rocks are 10-20 and 70 ${\Omega}$-m, respectively. The depth to weathered rock is 26-58 m and the depth to soft rock is 46-75 m.

• Economic and Environmental Geology
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• v.56 no.6
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• pp.629-646
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• 2023

Host rock of Cheonjeon-ri petroglyph is shale belonging to the Daegu Formation of Cretaceous Gyeongsang Supergroup. The rocks were hornfelsified by thermal alteration, and shows high density and hardness. The petroglyph forms weathered zone with certain depth, and has difference in mineral and chemical composition from the unweathered zone. As the physical deterioration evaluations, most of cracks on the surface appear parallel to the bedding, and are concentrated in the upper part with relatively low density. Breakout parts are occurred in the upper and lower parts of the petroglyph, accounting for 6.0% of the total area and occurs to have been created by the wedging action of cracks crossing. The first exfoliation parts occupying the surface were 23.8% of the total area, the second exfoliations covered with 9.3%, and the exfoliation parts with three or more times were calculated as 3.4%. It is interpreted that this is not due to natural weathering, and the thermal shock caused by the cremation custom here in the past. As the ultrasonic properties, the petroglyph indicates highly strength in the horizontal direction parallel to bedding, and the area with little physical damage recorded mean of 4,684 m/s, but the area with severe cracks and exfoliations showed difference from 2,597 to 3,382 m/s on average. Physical deterioration to the Cheonjeon-ri petroglyph occurred to influence by repeated weathering, which caused the rock surface to become more severe than the inside and the binding force of minerals to weaken. Therefore, it can be understood that when greater stress occurs in the weathered zone than in the unweathered zone, the relatively weathered surface loses its support and exfoliation occurs.

• Economic and Environmental Geology
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• v.39 no.6 s.181
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• pp.771-786
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• 2006

Imha lake has a high turbid water which keeps up during a few months, as comparing to other dams. Origins of the high turbid water derive from suspended materials which compose of micro particles of clay and rock-forming minerals. They are the weathered products from surface rocks that relate with particular geology in drainage field of the Imha dim. Accordingly we have fundamentally surveyed the kinds, properties, distribution and structures of general geology, found a few particular geology that source clay materials, and traced the passage that their weathered products enter the dam. We have suggested the basic origins of increase in turbid degree from detecting kinds and behavior of the suspended materials cause high turbid water in the Imha lake.