• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.60-66
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• 2020

Torrential rain causes landslide damage every year. In particular, the 2011 downpour caused landslides at numerous points throughout Mt. Woomyeon, which resulted in considerable damage to people and property. Because it occurred in an urban area, this case became a major social issue and received public attention. Measures were quickly implemented for multilateral investigations and recovery. Landslides caused by heavy rain are greatly affected by rainfall at the time. Landslides from the upper part erode the flow path, increasing the size, causing much damage to the lower part. This study selected a rural village area among the damaged areas of Mt. Woomyeon, and analyzed the change in terrain profile before and after a landslide using the DSM data obtained from airborne LiDAR. This area can be divided into three hydrological basins. For each basin, the analysis was performed on the average slope of each part of the flow path, as well as the erosion and deposition due to soil flow. As a result of the analysis, it was estimated that the total amount of soil from the Jeonwon village was 15,300㎥. These field data based on GIS can be used as basic information to predict damage in the case of a similar disaster, and it can be helpful in analyzing the results of various debris flow simulations.

• Steel and Composite Structures
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• v.49 no.1
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• pp.81-89
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• 2023

A simplified calculation method of natural vibration characteristics of high-speed railway multi-span bridge-longitudinal ballastless track system is proposed. The rail, track slab, base slab, main beam, bearing, pier, cap and pile foundation are taken into account, and the multi-span longitudinal ballastless track-beam-bearing-pier-cap-pile foundation integrated model (MBTIM) is established. The energy equation of each component of the MBTIM based on Timoshenko beam theory is constructed. Using the improved Fourier series, and the Rayleigh-Ritz method and Hamilton principle are combined to obtain the extremum of the total energy function. The simplified calculation formula of the natural vibration frequency of the MBTIM under the influence of vertical and longitudinal vibration is derived and verified by numerical methods. The influence law of the natural vibration frequency of the MBTIM is analyzed considering and not considering the participation of each component of the MBTIM, the damage of the track interlayer component and the stiffness change of each layer component. The results show that the error between the calculation results of the formula and the numerical method in this paper is less than 3%, which verifies the correctness of the method in this paper. The high-order frequency of the MBTIM is significantly affected considering the track, bridge pier, pile soil and pile cap, while considering the influence of pile cap on the low-order and high-order frequency of the MBTIM is large. The influence of component damage such as void beneath slab, mortar debonding and fastener failure on each order frequency of the MBTIM is basically the same, and the influence of component damage less than 10m on the first fourteen order frequency of the MBTIM is small. The bending stiffness of track slab and rail has no obvious influence on the natural frequency of the MBTIM, and the bending stiffness of main beam has influence on the natural frequency of the MBTIM. The bending stiffness of pier and base slab only has obvious influence on the high-order frequency of the MBTIM. The natural vibration characteristics of the MBTIM play an important guiding role in the safety analysis of high-speed train running, the damage detection of track-bridge structure and the seismic design of railway bridge.

• Journal of the Korean earth science society
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• v.34 no.6
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• pp.515-523
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• 2013

The eastern coast of South Korea is expected to be damaged by volcanic ash when Mt. Baekdusan volcano erupts. Even if the amount of volcanic ash is small, it can be fatal on the agricultural sector withering many plants and causing soil acidification. Thus, in this paper, we aim to estimate agricultural losses caused by the volcanic ash and to visualize them with Google map. To estimate the volcanic ash losses, a damage assessment model is needed. As the volcanic ash hazard depends on the kind of a crops and the ash thickness, the fragility function of damage assessment model should represent the relation between ash thickness and damage rate of crops. Thus, we model the fragility function using the damage rate for each crop of RiskScape. The volcanic ash losses can be calculated with the agricultural output and the price of each crop using the fragility function. This paper also represents the estimated result of the losses in Gangwon province, which is most likely to get damaged by volcanic ashes in Korea. According to the result with gross agricultural output of Gangwon province in 2010, the amount of volcanic ash losses runs nearly 635,124 million wons in Korean currency if volcanic ash is accumulated over four millimeters. This amount represents about 50% of the gross agricultural output of Gangwon province. We consider the damage only for the crops in this paper. However, a volcanic ash fall has the potential to damage the assets for a farm, including the soil fertility and installations. Thus, to estimate the total amount of volcanic ash damage for the whole agricultural sectors, these collateral damages should also be considered.

• Journal of Bio-Environment Control
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• v.25 no.4
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• pp.255-261
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• 2016

The present study was conducted to characterize physiological responses of aerial part according to soil water stresses in 'Mihong' peach trees. Discolorations, wilting and falling of leaves were observed in chronological order as response for waterlogging and no irrigation and the phenomena started from basal to end of shoots. Shoot growth in elongation and thickness decreased and fallen leaves were severe in waterlogged trees. Function of water uptake by roots and photosynthesis and leaf respiration decreased by waterlogging. Leaf chlorophyll contents decreased in both treatments. In waterlogging treatment, decrease of chlorophyll was observed in normal leaves with waterlogging using light microscopy. Starch content was lower in both treatment and carbohydrate content was lower in root with waterlogging. These results demonstrated that waterlogging weakened the function of soil water uptake and movement and decreased photosynthesis and fallen leaves. Finally the peach trees would wither or suffer low temperature damage through the shortage of reserve accumulations. We suggested that waterlogging damage in peach trees could be reduced to take notice of irrigation and install drainage facility to improve soil condition.

• Korean Journal of Environment and Ecology
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• v.2 no.1
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• pp.50-65
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• 1988

Trail and campground deteriorations and their environmental changes of soil and vegetation were studied in Guryong district of Mt. Chiak National Park in 1988. The Widths of both the entire trail and the bare portion as the trail condition were significantly greater on the more heavily used trail. and regressions showed the significant positive relationship between slope along the trail and maximum depth of the trail($R^2$=0.35). Deterioration types of trail which had higher frequency for a total of 63 observations were rock exposure(48%), trail deepening(29%) and root exposure(27%) in the high order. And occurence of trail deterioration was considerably influenced by slope along the trail Ecological changes of soil and vegetation of trailsides were not found at a uniform tendency but could be grouped, by the types of user's disturbance. On campsites. tree damage types and their frequencies were basic as a means of which grasp the limits of user's impact. The area with damaged trees on campsite in pine forest were larger than that in mixed forest and the frequency by damage type of trees varied according to the distance from the core of campsite and to the crown layer. Water content, pH and hardness of soil. coverage of lower trees, species and individuals per 100$m^2$, basal areas of upper and middle layer of trees had significant relationship with the distance from campsite to forest. The range influenced by user's disturbance was more than 70-80m, md Staphylea bumalda, Morns bombycis, Stephanandra incisa and Securinega suffruticosa were considered as tolerant species to user's impact.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.6
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• pp.439-447
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• 2019

In this study, experiments were conducted to establish appropriate measures for slopes with high risk of collapse and to obtain results for minimizing slope collapse damage by detecting the micro-displacement of soil in advance by installing a laser sensor and a vibration sensor in the landslide reduction model experiment. Also, the behavior characteristics of the soil layer due to rainfall and moisture ratio changes such as pore water pressure and moisture were analyzed through a landslide reduction model experiment. The artificial slope was created using granite weathering soil, and the resulting water ratio(water pressure, water) changes were measured at different rainfall conditions of 200mm/hr and 400mm/hr. Laser sensors and vibration sensors were applied to analyze the surface displacement, and the displacement time were compared with each other by video analysis. Experiments have shown that higher rainfall intensity takes shorter time to reach the limit, and increase in the pore water pressure takes shorter time as well. Although the landslide model test does not fully reflect the site conditions, measurements of the time of detection of displacement generation using vibration sensors show that the timing of collapse is faster than the method using laser sensors. If ground displacement measurements using sensors are continuously carried out in preparation for landslides, it is considered highly likely to be utilized as basic data for predicting slope collapse, reducing damage, and activating the measurement industry.

• Journal of the Korea Concrete Institute
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• v.21 no.2
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• pp.187-197
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• 2009

This paper presents a systematic approach for estimating fragility curves and damage probability matrices for different frequencies. Fragility curves and damage probability indicate the probabilities that a structure will sustain different degrees of damage at different ground motion levels. The seismic damages are to achieved by probabilistic evaluation because of uncertainty of earthquakes. In contrast to previous approaches, this paper presents a method that is based on nonlinear dynamic analysis of the structure using empirical data. This paper presents the probability of damage as a function of peak ground acceleration and estimates the probability of five damage levels for prestressed concrete (PSC) bridge pier subjected to given ground acceleration. At each level, 100 artificial earthquake motions were generated in terms of soil conditions, and nonlinear time domain analyses was performed for the damage states of PSC bridge pier structures. These damage states are described by displacement ductility resulting from seismic performance based on existing research results. Using the damage states and ground motion parameters, five fragility curves for PSC bridge pier with five types of dominant frequencies were constructed assuming a log-normal distribution. The effect of dominant frequences was found to be significant on fragility curves.

• Journal of the Korean Geosynthetics Society
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• v.4 no.4
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• pp.23-37
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• 2005

The factors affecting the long-term design strength of geogrid can be classified into factors on creep deformation, installation damage, temperature, chemical degradation and biological degradation. Especially, creep deformation and installation damage are considered as main factors to determine the long-term design strength of geogrid. Current practice in the design of a reinforced soil structures is to calculate the long-term design strength of a geosynthetic reinforcement damaged during installation by multiplying the two partial safety factors, $RF_{ID}$ and $RF_{CR}$. This method assumes that there is no evaluation of synergy effect between installation damage and creep deformation of geogrids. This paper describes the results of a series of experimental study, which are carried out to assess the combined effect of the installation damage and the creep deformation for the long-term design strength of geogrid reinforcements. A series of field tests was carried out to assess installation damage of various geogrids with respect to different fill materials, and then creep tests are conducted to evaluate the creep deformation of both undamaged and damaged geogrids. The results indicated that the tensile strength reduction factors, RF, considering the combined effect between the installation damage and the creep deformation is less than that calculated by the current design method.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.27 no.4
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• pp.385-397
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• 1982

The climatic impacts have been the environmental constraints with soil characteristics to achieve self sufficiency of food production in Korea. In this paper, the distribution and appearance of impacts and the changes in climatological status due to recent trend of early transplanting of rice are widely discussed to derive some countermeasures against the impacts, being focussed on cultural A long term analysis of the climatic impact appearances of the last 74 years showed that drought, strong wind, flood, cold spell and frost were the major impacts. Before 1970's, the drought damage was the greatest among the climatic impacts; however, the expansion and improvement of irrigation and drainage system markedly decreased the damage of drought and heavy rain. The appearance of cold damage became more frequent than before due to introduction of early transplanting for more thermophilic new varieties. Tongillines which were from Indica and Japonica crosses throw more attention to cold damage for high yields to secure high temperature in heading and ripening stages and lead weakness to cold and drought damage in early growth stage after transplanting. The plants became subject to heavy rain in ripening stage also. For the countermeasures against cold damage, the rational distribution of adequate varieties according to the regional climatic conditions and planting schedule should be imposed on the cultivation. A detoured water way to increase water temperature might be suggestable in the early growth stage. Heavy application of phosphate to boost rooting and tillering also would be a nutritional control method. In the heading and ripening stages, foliar application of phosphate and additional fertilization of silicate might be considerable way of nutritional control. Since the amount of solar radiation and air temperature in dry years were high, healthy plants for high yield could be obtained; therefere, the expansion of irrigation system and development of subsurface water should be performed as one of the national development projects. To minimize the damage of strong wind and rainfall, the rational distribution of varieties with different growing periods in the area where the damage occurred habitualy should be considered with installation of wind breaks. Not only vertical windbreaks but also a horizontal wind break using a net might be a possible way to decrease the white heads in rice field by dry wind. Finally, to establish the integrated countermeasures against the climatic impacts, the detailed interpretation on the regional climatic conditions should be conducted to understand distribution and frequency of the impacts. The expansion of observation net work for agricultural meteorology and development of analysis techniques for meteorological data must be conducted in future together with the development of the new cultural techniques.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.11 no.3
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• pp.1-11
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• 2008

Although landslides were frequently occurred under Tripterygium regelii and Rubus sp. vegetations, the damage of landslide was not observed in sasa (Sasa borealis) stands. These phenomena may be affected by forest vegetation types. This result suggested that the landslide occurred in Jirisan (Mt.) National Park may be closely related to water retention capacity at Sasa borealis stands. This study compared and analyzed the water retention capacity of each soil horizon of sasa, larch (Larix leptolepis) and mongolian oak (Quercus mongorica) stands. Soil bulk density in A horizon was lower in sasa (0.776g/$cm^3$) than in mongolian oak (0.828g/$cm^3$) and in larch stands (1.282g/$cm^3$). Water permeability in A horizon was 0.02055cm/sec for sasa, 0.00575cm/sec for mongolian oak, and 0.0007cm/sec for larch stands, respectively. The water permeability of sasa stand was about 3.6 times and about 29 times higher than in mongolian oak and in larch stands, respectively. This result indicates that water infiltration of soil surface during a rain event is more rapid in sasa than in other two stands. Soil organic matter content in B horizon was lower in larch (0.7%) than in mongolian oak (6.5%) and in Sasa (3.3%) stands. The solid ratio in A horizon was highest in larch among three stands, but that of mongolian oak and larch stands showed a similar rate. Pore space rates was 70.7% for A horizon and 70.6% for B horizon of sasa, 68.9% for A horizon and 70.6% for B horizon of sasa, 68.9% for A horizon and 70.6% for B horizon of mongolian oak forests and 51.7% for A horizon and 49.2% for B horizon of larch forests, respectively. According to pore space rates, the water retention capacity may be poor in larch stand compared with other two stands. Soil strength in sasa and mongolian stands was over 25kgf/$cm^2$ from 40cm depth, while the strength was over 25kgf/$cm^2$ from 25cm depth in larch stand. The result indicates that tree growth and water permeability in larch stand could be limited due to high soil strength. Larch stand was poor for soil pore space development to be offered to the water retention capacity, but water retention capacity of A horizon soil in sasa stand was high than that of other two stands. Therefore, establishment of sasa stand under larch stand could help to prevent landslides.