• The Journal of Engineering Geology
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• v.22 no.3
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• pp.331-341
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• 2012

Granitoid rocks are generally high-quality rock from a geotechnical perspective, because they rarely contain systematic joints or fragmented fault zones. Although the rock type at the Sanhak site is granite, a collapsed slope has a deep soil layer and shows no residual structures such as discontinuities or faults; surface avalanches from this slope can be observed in several places. To study the stability of this slope, we investigated rainfall duration, variation in pore-water pressure, and the factor of safety considering three cases (current cross-section, initial planning cross-section, revised planning cross-section). With increasing duration of rainfall, the groundwater level rises, up to 20 m in height from ground surface. In the initial planning cross-section, safety was secure for rainfall of 2 days duration, but inadequate for rainfall of 4 days duration. In the revised planning cross-section, however, safety factors were secure for rainfall of 4 days duration. Therefore, to ensure permanent stability at the Sanhak site, a slope degree of 1:1.8 should be maintained during cutting.

• Journal of Korean Society of Forest Science
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• v.20 no.1
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• pp.51-60
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• 1973

The trend and achievments of soil erosion control research in Japan were investigated through observation tours and reference work and following facts were found to be important aspects which should be considered in the soil erosion control research program in Korea. Experiments on forest and water relations, and ground water phenomena at the water source zone in Tokyo University. Studies on land-slides and erosion control dam in Kyoto University. Studies on mud-flow and snow avalanches in Hokkaido University. Studies on sanddune fixation and disaster damage prevention forests in Kyushu University. Studies on forest denudations in Nagoya University. Studies on Greening-works and soil erosion prevention chemicals in Tokyo Agriculture University. Training on planning of erosion control works and prevention of disaster damages in Forest Research Institute. Experiments on soil erosion phenomena and infiltration in Tohoku Branch, FRI. Experiments on erosion and surface stratum failure of steep slopes and their prevention methods in Railway Technical Research Institute.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.181-194
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• 2013

Landslides are known as gravitational mass movements that can carry the flow materials ranging in size from clay to boulders. The various types of landslides are differentiated by rate and depositional features. Indeed, flow characteristics are observed from very slow-moving landslides (e.g., mud slide and mud flow) to very fast-moving landslides (e.g., debris avalanches and debris flows). From a geomechanical point of view, shear-rate-dependent shear strength should be examined in landslides. This paper presents the design of advanced ring-shear apparatus to measure the undrained shear strength of debris flow materials in Korea. As updated from conventional ring-shear apparatus, this apparatus can evaluate the shear strength under different conditions of saturation, drainage and consolidation. We also briefly discussed on the ring shear apparatus for enforcing sealing and rotation control. For the materials with sands and gravels, an undrained ring-shear test was carried out simulating the undrained loading process that takes place in the pre-existing slip surface. We have observed typical evolution of shear strength that found in the literature. This paper presents the research background and expected results from the ring-shear apparatus. At high shear speed, a temporary liquefaction and grain-crushing occurred in the sliding zone may take an important role in the long-runout landslide motion. Strength in rheology can be also determined in post-failure dynamics using ring-shear apparatus and be utilized in debris flow mobility.

• Journal of Environmental Policy
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• v.5 no.4
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• pp.1-18
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• 2006

Recently, the damage by fresh flood increases in Gangwon-do and Gyeongsangbuk-do of the north-eastern area of Korea. Even though the recent pattern of rain fall keeps changing, there is no strategy to mitigate damage by disaster. For the appropriate measure and policy for decreasing damage, an index for vulnerability is necessary to provide evidence of local climate change. The present work analyzes the flooding damage cost during the past 20 years. During 80's, the southern area of Korea was seriously damaged by over-floods on the agricultural ground. After that time, the loss and damage has decreased in the southern area but the middle part has shown slight but distinct increases of damage. The absolute coast of damage in the northern part has kept constant. However, the relative regional damage to the total country damage has kept increasing over 20 years in the same area. The surface area of floods is strongly correlated with the regional damage cost in the southern part but the north-eastern part has weak correlation between flooded area and cost. It implies that the recent damage in the north-eastern mountain area was not caused by flood itself but the other factors such as avalanches. The present work expects that the damage cost can be a good proxy value for index for climate change impact assessment.