• Journal of the Korean GEO-environmental Society
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• v.13 no.9
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• pp.75-82
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• 2012

This paper is the results of analysis for the causes and characteristics of landslide according to heavy rain occurred in west area of Gangwon province which is affected by typhoon such as Ewiniar and Bilis in 2006. West side of Gangwon province is topographically weak for the landslide and debris flow since it is covered by soil of weathered rock such as Gneiss and Granite. From the results of analysis for the rainfall characteristics, it was found that landslide occurrence is closely related to the accumulated rainfall amount less than 3 days. Furthermore, it was found that regional difference of occurrence frequency is effected by 1-hour maximum rainfall intensity. From the results of analysis for the landslide data of 860 locations occurred in west side, it was shown that failure mode was changed from transition slide to liquidity slide. Occurrence frequency was high at the slope angle of $20{\sim}30^{\circ}$ slope length of 11~20, and slope width of 6~10. Landslide of west side is the typical landslide of Gneiss and Granite and the type of small scale which has narrow slope width.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.3
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• pp.237-246
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• 2021

With climate change, debris flow has been increasing due to the collapse and erosion of shallow slopes caused by extreme rainfall. It is preferred to an economical and eco-friendly method rather than reinforcement of soil slopes with the earth anchor or nailing method. In this study, a soil improvement agent was developed by utilizing insitu soil, leaf mold, and used harbal medicine to help sufficient vegetation. In addition, to prevent surface erosion, shear strength of the soil was increased by using micro cement and hemihydrate gypsum as additives. The optimum mix ratio of the mixture is determined by increasing the shear strength by checking the erosion progress of the ground surface layer due to rainfall through an laboratory test. The safety factor of soil slope has been improved on the slope surface reinforced by the improvement agent, and the strength of erosion has been increased, making it efficient to cope with heavy rain during wet season.

• The Korean Journal of Petroleum Geology
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• v.10 no.1_2 s.11
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• pp.23-33
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• 2004

The Lago Sofia conglomerate in southern Chile is a lenticular unit encased within mudstone-dominated, deep-sea successions (Cerro Toro Formation, upper Cretaceous), extending from north to south for more than $120{\cal}km$. The Lago Sofia conglomerate is a unique example of long, gravelly deep-sea channels, which are rare in the modern environments. In the northern part (areas of Lago Pehoe and Laguna Goic), the conglomerate unit consists of 3-5 conglomerate bodies intervened by mudstone sequences. Paleocurrent data from these bodies indicate sediment transport to the east, south, and southeart. The conglomerate bodies in the northern Part are interpreted as the tributary channels that drained down the Paleoslope and converged to form N-S-trending trunk channels. In the southern part (Lago Sofia section), the conglomerate unit comprises a thick (> 300 m) conglomerate body, which probably formed in axial trunk channels of the N-5-trending foredeep trough. The well-exposed Lago Sofia section allowed for detailed investigation of sedimentary facies and large-scale architecture of the deepsea channel conglomerate. The conglomerate in Lago Sofia section comprises stratified conglomerate, massive-to-graded conglomerate, and diamictite, which represent bedload deposition under turbidity currents, deposition by high-density turbidity currents, and muddy debris flows, respectively. Paleocurrent data suggest that the debris flows originated from the failure of nearby channel banks or slopes flanking the channel system, whereas the turbidity currents flowed parallel to the orientation of the overall channel system. Architectural elements produced by turbidity currents represent vertical stacking of gravel sheets, lateral accretion of gravel bars, migration of gravel dunes, and filling of channel thalwegs and scoured hollows, similar to those in terrestrial gravel-bed braided rivers. Observations of large-scale stratal pattern reveal that the channel bodies are offset stacked toward the east, suggestive of an eastward migration of the axial trunk channel. The eastward channel migration is probably due to tectonic tilting related to the uplift of the Andean protocordillera just west of the Lago Sofia deep-sea channel system.

• The Journal of Engineering Geology
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• v.27 no.2
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• pp.125-132
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• 2017

Approximately 64 percent of Korean territory is covered with mountains, and there is occurred a continuous mountain disaster such as landslide, debris flow and slope failure around mountain slopes due to heavy rainfall and typhoon in the summer season. Even in such a reality, the development of mountain areas is being carried out through the development and expansion of social infrastructures centered on mountain areas, but systematic management is insufficient. Constructions of a forest road facility for mountain slopes can be a cause of mountain disasters intensively in the summer season due to artificially changing the mountain area. In this unstable mountain environment, efforts to build a disaster-resistant environment are urgently needed. This research is to analyze the stability of mountain slopes according to soil depth (1~5 m) and mountain slope ($20{\sim}60^{\circ}$) considering the characteristics of rainfall infiltration under extreme rainfall conditions. As a result, the stability of the mountain slope was found to be different according to the depth of soils and the saturation area of the soil layer. As well as the stability of the mountain area was found to be lower than that of the natural mountain area. Specially, rainfall infiltration occurs at the upper slope of the forest road. For this reason, the runoff phenomenon of rainfall infiltration water occurs clearly when the depth of soil layer is low.