• Korean Journal of Environment and Ecology
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• v.33 no.5
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• pp.578-586
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• 2019

The purpose of this study was to investigate the change of spatial distribution of Korean red pine (Pinus densiflora Siebold & Zucc.) in Hallasan National Park by surveying the distribution and crown density and analyzing by the elevation, slope, orientation, and regional habitat in 2006 and 2015. The total area of the Korean red pine forest was 1,259.9 ha in 2015, which increased by 51.4 ha, or 4.1%, compared to 1,208.5 ha in 2006. For the past 10 years, the area of sparse density with crown density of 11% to 40% of Korean red pine increased by 59.8 ha, the area of moderate density with crown density of 41% to 70% increased by 59.0 ha, and the area of dense density with 71% or more crown density increased by 67.3 ha. In terms of the altitude above sea level, the Korean red pine forest area between 1,010 m and 1,400 m was the largest at 1,003.0 ha or 79.6% of the total area in 2015. The area between 1,100 m and 1,300 m increased, and the area of dense density decreased significantly while the areas of moderate density and sparse density increase. There was no notable change according to the land slope, and the area increased from 2006 regardless of the slope. By direction, 56.4% were distributed in the southwest and southeast directions centered on the south-facing slope with the increase of 27.8 ha over the 10 years while the northwest and northeast directions centered on the north-facing slope decreased by 7.6 ha. Regarding the distribution change of the Korean red pine forest by the region, the Yeongsil area showed an increase of 25.5 ha, or 49.6% of the total area increase, in 2006 while the Ibseog-oreum area including the right side on the Sanbeoleum mountain valley increased by 20.4 ha. The distribution in the Gaemideung area that includes Jogeundeule increased by 7.4 ha while that of Sogbat in Sungpanak Trail decreased by 1.9 ha. This study analyzed the changes in the distribution area and crown density of the Korean red pine forest according to the altitude, slope, direction, and regional habitat in Hallasan National Park. The expansion of Korean red pine forest distribution was limited to the areas where the grass and the shrub was the dominating vegetation structure, or the forest gap was created by the disturbance. On the other hand, the distribution area of the Korean red pine forest surrounded by deciduous broad-leaved forests or mixed vegetation structure is considered to result from the change in density more than the area due to competition with deciduous broad-leaved trees.

• Tunnel and Underground Space
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• v.22 no.2
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• pp.106-119
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• 2012

Roughness of rock joint has generally been characterized based upon geometrical aspects of a two-dimensional surface profile. The appropriate description of joint roughness, however, should consider the features of roughness mobilization at contact areas under normal and shear loads. In this study, direct shear tests were conducted on the replicas of tensile fractured gneiss joints and the influence of the shear direction on the shear behavior and effective roughness was examined. In this procedure, a joint surface was represented as a group of triangular planes, and the steepness of each plane was characterized using the concepts of the active and inactive micro-slope angles. The contact areas at peak strength which were estimated by a numerical method showed that the locations of the contact areas were mainly dependent on the distribution of the micro-slope angle and the shear behavior of joint was dominated by only the fractions with active micro-slope angles. Therefore, a three-dimensional coefficient for the quantification of rock joint roughness is proposed based on the distribution of active micro-slope angle: active roughness coefficient, $C_r$. Comparison of the active roughness coefficient and the peak shear strength obtained from the experiment suggests that the active roughness coefficient is the effective parameter to quantify the surface roughness and estimate the shear behavior of rock joint.

• Journal of Korean Society of Forest Science
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• v.108 no.4
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• pp.552-561
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• 2019

In korea, debris-flow disasters are induced by typhoon and localized torrential rainfall annually. These disasters are particularly severe in the Korean national park due to its geomorphological characteristics. This study was conducted to analyze the landslide characteristics and forest environmental factors of landslide areas located in rugged mountain range in the Korean national park (Mt. Seorak, Mt. Jiri, and Mt. Sobaek). Overall, landslides occurred at 474 sites. The average area of the landslide scar among these sites was 1,212 ㎡. The average landslide sediment was 1,389 ㎥, average landslide length was 75 m, and the average width was 12.9 m. The landslides frequently occurred in regions with igneous rock and coniferous forest. In addition, slope gradient degree (31°-40°), slope gradient direction (N), vertical slope (concave), cross slope (concave), altitude (401-800 m), position (middle), stream order (first order), forest type (mixed), parent rock (igneous), and soil depth (<46 cm). The relationship between landslide soil volume and environmental factors showed positive correlation. The variables of vertical slope (complex), altitude (<1,201 m), and soil depth (<46 cm) correlated significantly at 1 % level.

• Journal of the Korean Wood Science and Technology
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• v.28 no.2
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• pp.10-18
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• 2000

Nondestructive testing(NDT) by using ultrasonic sound is widely applied to wood for grading, moisture and defect detecting, estimating degree of decay, etc. Before practicing such application, basic relationships between ultrasonic transmission and wood properties shall be studied first. In this study, ultrasonic NDT was applied to larch and red pine to investigate the effects of moisture content and slope of grain on ultrasonic transmission speed. Specimens for testing about moisture content were prepared to have moisture content of green state, 30%, 20%, 10% and oven-dry state. Specimens for testing about slope of grain were prepared to have grain angle of 0, 15, 30, 45, 60, 75 and 90 degree in the tangential direction. Ultrasonic transmission speed was inversely proportional to moisture content in low range of moisture content under around 30% that was considered to be close to fiber saturation point. In high moisture content range above 30%, the ultrasonic transmission speed was almost constant. The same trend was observed in the relationships between compressive strength and moisture content. Slope of grain also had inversely proportional relationship with ultrasonic transmission speed and compressive strength. The relationship between compressive strength and ultrasonic transmission speed could be expressed by a linear equation.

• Journal of the Korean GEO-environmental Society
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• v.24 no.10
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• pp.41-49
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• 2023

Structures such as bridge columns installed on the asymmetric ground such as mountain areas and sloping ground are subject to various loads such as wind, temperature, earthquake, and etc. The pile foundation is generally applied to bridge columns on the asymmetric ground in order to stably support structures. The behavior of the pile foundation supporting bridge columns changes due to various load conditions. In particular, ground-pile-structure interactions should be studied to analyze the behavior of the pile foundation that supports bridge columns effected by dynamic loads such as earthquakes. The pile foundation installed on the asymmetric ground effected by the earthquake has the complicated dynamic interaction between the foundation and the ground due to the ground slope, the difference in soil resistance according to the shaking direction, and the ground movements. In this study, the 1g shaking table tests were conducted to confirm the effect of the slope of the sloping ground on the dynamic behavior of group piles supporting the superstructure installed at the berm of the sloping sandy soil which is the asymmetric ground. The result shows that the acceleration of the pile cap and the superstructure decrease as the slope of the sloping ground increase, and the slope of the dynamic p-y curve of the pile decrease.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.2
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• pp.117-125
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• 2015

Quantitative risk assessment (QRA) of railway is to create a variety of scenario and to quantify the degree of risk by a result of the product of accident frequency and accident. Quantitative risk Assessment is affected by various factors such as tunnel specifications, characteristics of the fire, and relation of smoke control and evacuation direction. So in this study, it is conducted that how the way of smoke control and the relation of smoke control and evacuation direction affect quantitative risk assessment with variables (the tunnel length (2, 3, 4, 5, 6 km) and the slope (5, 15, 25‰)). As the result, in a train fire at the double track tunnel (Area = $97m^2$), it is most efficient to evacuate to the opposite direction of smoke control regardless of the location of train in train fire. In addition, under the same condition, index risk in mechanical ventilation up to 1/10.

• Advances in materials Research
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• v.4 no.4
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• pp.215-226
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• 2015

Experiment on roughness and micro pit defects of SUS 430 ferrite stainless steel was investigated in laboratory. The relation between roughness and glossiness with reduction in height, roll surface roughness, emulsion parameters was analyzed. The surface morphology of micro pit defects was observed by SEM, and the effects of micro pit defects on rolling reduction, roll surface roughness, emulsion parameters, lubrication oil in deformation zone and work roll diameter were discussed. With the increasing of reduction ratio strip surface roughness Ra(s), Rp(s) and Rv(s) were decreasing along rolling and width direction, the drop value in rolling direction was faster than that in width direction. The roughness and glossiness were obtained under emulsion concentration 3% and 6%, temperature $55^{\circ}C$ and $63^{\circ}C$, roll surface roughness $Ra(r)=0.5{\mu}m$, $Ra(r)=0.7{\mu}m$ and $Ra(r)=1.0{\mu}m$. The glossiness was declined rapidly when the micro defects ratio was above 23%. With the pass number increasing, the micro pit defects were reduced, uneven peak was decreased and gently along rolling direction. The micro pit defects were increased with the roll surface roughness increase. The defects ratio was declined with larger gradient at pass number 1 to 3, but gentle slope at pass number 4 to 5. When work roll diameter was small, bite angle was increasing, lubrication oil in micro pit of deformation zone was decreased, micro defects were decreased, and glossiness value on the surface of strip was increased.

• The Journal of Engineering Geology
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• v.3 no.3
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• pp.279-293
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• 1993

In recent yeaes, the collapses of man made structures have been encountered from time to time due to the deformation of the ground in korea. Furthermore, the possibilities of casasters from the ground deformation suCh as landslide and active fault are atrracting our attention to the deformation monitoring. In this study, two-coordinate tilt which was monitored during six months in order to develop tediniques for prevention of disasters from the ground deformation. The two-coordinate tilt which was detected by a tilt-sensor installed in shallow depth on the slope with the sensitivity of 0.0001 arc.sec in every 10 minutes was recorded continously to PC through the interface with 200-m line coonection. The observed digital tilt data. together with the relevant meteorological data were analyzed in reference to engineering application. During the whole observation period of six months, the net tilt is 10.06 arc.sec to the west and 73.88 arc.sec to the south. Consequently the ground has a tilt of 74.56 arc.sec to the direction of $S7.75^{\circ}W$ with average tilting of 0.02 arc.sec/hour. In spite of such fast and large tilting, it is interpreted in view of engineering aspects that the site is much safe from danger, since both East-West and North-South components of tilt converge as time goes by. Two categories of deformational events are recognized ; one is toward the direction of surface slope and the other is to the direction of increased pore pressure. Tiks are acenain to have a close relation with precipitation of rain. The daily variation of two-coordinate tilt is delayed 4.3 hours in average after the variation of atmospheric temperature. A certain correlation between atmospheric pressure and deformation might be revealed.

• The Journal of Engineering Geology
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• v.16 no.4 s.50
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• pp.437-453
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• 2006

More than 3,000 landslides were occurred by torrential rains in Gangneung area due to the typhoon Rusa in 2002. In order to analyze the landslide origin and its geometric characteristics, 1,365 landslide data were collected from the field survey of Sacheon, Jumunjin, and Yeongok areas in which the intensive landslides took place. The average landslide size in the study area was composed of 10m width, 30m length, and $21^{\circ}{\sim}35^{\circ}$ slope angle, and the plane view of landslides A-type (i.e. wide shape of lower part) that contains approximately 50.5% of the landslides commonly occurred. In particular the area of Sacheon heavily damaged by mountain fires had more occurrence of landslides than other areas. The landslides of uniform tendency of slope direction were examined resulted from the contribution of topographic characteristics due to the weathering and wind direction during heavy rainfalls. In order to analyze the direction of joint, 249 orientation data were collected from the study area. The window method was employed to determine the characteristics of joint density in 51 locations of the study area. The results showed that many landslides occurred in the areas of joint density with the range of $0.05{\sim}0.1$.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.5
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• pp.27-35
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• 2019

The purpose of this study is to analyze the displacement characteristics in slow-moving landslide area using digital elevation model and airborne LiDAR when unpredictable disaster such as slow-moving landslide occurred. We also aimed to provide basic data for establishing a rapid, reasonable and effective restoration plan. In this study, slow-moving landslide occurrence cracks were selected through the airborne LiDAR data, and the topographic changes and the scale of occurrence were quantitatively analyzed. As a result of the analysis, the study area showed horseshoe shape similar to the general form of slow-moving landslide occurrence in Korea, and the direction of movement was in the north direction. The total area of slow-moving landslide damage was estimated to about 2.5ha, length of landsldie scrap 327.3m, average width 19.3m, and average depth 8.6m. The slow-moving landslides did not occur on a large scale but occurred on the adjacent slope where roads were located, caused damage to retaining walls and roads. The field survey of slow-moving landslides was limited by accessibility and safety issues, but there was an advantage that accurate analysis was possible through the airborne LiDAR. However, because airborne LiDAR has costly disadvantages, it has proposed a technique to mount LiDAR on UAV for rapidity, long-term monitoring. In a slow-moving landslide damage area, information such as direction of movement of cracks and change of scale should be acquired continuously to be used in restoration planning and prevention of damage.