• Journal of the Korean GEO-environmental Society
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• v.20 no.12
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• pp.33-39
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• 2019

The upsurge of population, internal migration, economic activities and developmental works has brought significant land use and land cover (LULC) change over the period of 1990 and 2010 in the Bagmati basin of Nepal. Along with alteration on various other ecosystem services like water yield, water quality, soil loss etc. carbon sequestration is also altered. This study thus primary deals with evaluation of LULC change and its impact on the soil carbon storage for the period 1990 to 2010. For the evaluation, InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) Carbon model is used. Residential and several other infrastructural development activities were prevalent on the study period and as a result in 2010 major soil carbon reserve like forest area is decreased by 7.17% of its original coverage in 1990. This decrement has brought about a subsequent decrement of 1.39 million tons of carbon in the basin. Conversion from barren land, water bodies and built up areas to higher carbon reserve like forest and agriculture land has slightly increased soil carbon storage but still, net reduction is higher. Thus, the spatial output of the model in the form of maps is expected to help in decision making for future land use planning and for restoration policies.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.03a
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• pp.940-945
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• 2010

There are human casualties that caused by slope-stability related disasters such as landslide and debris flow during typhoon and rainy season every year in Korea. These disaster sites can be analyzed systematically using digital topographic data and aerial photogrammetry. In this study, geographical factors such as slope degree, geology, height, and soil depth are analyzed in four landslide-disaster sites from Muju, Jinan, and Jangsu County based on digital elevation maps generated by ArcGIS. Each site showed different characteristics in geology and geography and it is found that GIS can be utilized for the visualization of steep-slope failure areas.

• Journal of the Earthquake Engineering Society of Korea
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• v.22 no.3
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• pp.193-199
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• 2018

This study aims to create a disaster management system after an earthquake. Japan's earthquake disaster management system, including the Disaster Countermeasures Basic Act, addresses all of the disaster phases of prevention, mitigation, preparedness and emergency response as well as recovery and reconstruction with roles and responsibilities among the national and local governments clearly defined. Korea's earthquake disaster management system are including the Disaster Countermeasures Basic, but when the 9.12 earthquake occurred, problems such as insufficient early response, study on the earthquake lack were revealed. This study conducted a field survey and analyzed coping process after Po Hang earthquake. Therefore, this study have found that Disaster Management Headquarters are operated rapidly. They are coped with urgent safety inspection for damage facilities and soil liquefaction with advanced equipment. And The headquarters interviewed with victims. So they found out What the victims needed. However, when carrying out relief activities, Research of temporary housing and allocation of donations was not rapid. Further, this study have found that earthquake specialists were lack and disaster information transfer was not working. This study will be utilized as fundamental data in planning disaster management system after an earthquake.

• Geomechanics and Engineering
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• v.30 no.2
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• pp.211-218
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• 2022

This study characterizes Proctor and geophysical properties in a broad range of grading and fines contents. The results show that soil index properties such as uniformity and fines plasticity control the optimum water content and peak dry unit trends, as well as elastic wave velocity. The capillary pressure at a degree of saturation less than S = 20% plays a critical role in determining the shear wave velocity for poorly graded sandy soils. The reduction in electrical resistivity with a higher water content becomes pronounced as the water phase is connected A parallel set of compaction and geophysical properties of sand-kaolinite mixtures reveal that the threshold boundaries computed from soil index properties adequately capture the transitions from sand-controlled to kaolinite-controlled behavior. In the transitional fines fraction zone between F_F ≈ 20 and 40%, either sand or kaolinite or both sand and kaolinite could dominate the geophysical properties and all other properties associated with soil compaction behavior. Overall, the compaction and geophysical data gathered in this study can be used to gain a first-order approximation of the degree of compaction in the field and produce degree of compaction maps as a function of water content and fines fraction.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2017.11a
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• pp.239-240
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• 2017

철도노반 현장의 저성토구간의 연약지반구간에 대하여, 성토높이 3m 이내인 저성토구간의 경우 열차하중에 따른 연약지반의 처리를 어떻게 하는 것이 향후 재난발생을 예방할 수 있는지에 대하여 설계기준 원문을 대상으로 적용방법에 대한 분석을 실시하였다.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2022.10a
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• pp.307-308
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• 2022

본 논문에서는 현장에서 발생된 점토에 양질토사를 혼합하여 노상 및 노체에 대한 쌓기 재료로 사용하기 위한 기초 연구로서 사용적합성 여부를 실험하여 분석하였다. 본 연구와 같은 방법을 현장에 적용할 경우에 공사비 절감이 가능할 것으로 판단된다.

• Geomechanics and Engineering
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• v.18 no.6
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• pp.639-650
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• 2019

Time-domain commercial codes are widely used to evaluate the seismic behavior of tunnels. Those tools offer a good insight into the performance and the failure mechanism of tunnels under earthquake loading. Viscous damping is generally employed in the dynamic analysis to consider damping at very small strains in some cases, and the Rayleigh damping is commonly used one. Many procedures to obtain the damping parameters have been proposed but they are seldom discussed. This paper illustrates the influence of the Rayleigh damping formulation on the tunnel visco-elastic behavior under earthquake. Four Rayleigh damping determination procedures and three soil shear velocity profiles are accounted for. The results show significant differences in the free-field and in the tunnel response caused by different procedures. The difference is somewhat decreased when the soil site fundamental frequency is increased. The conventional method which consists of using solely the first soil natural mode to determine the viscous damping parameters may lead to an unsafe seismic design of the tunnel. In general, using five times site fundamental frequency to obtain the damping formulation can provide relatively conservative results.

• Journal of the Korean Geotechnical Society
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• v.40 no.1
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• pp.39-46
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• 2024

Artificial recharge systems have been employed to solve drought problems due to global climate change. Despite the increased usage, the applications of artificial recharge systems are limited by clogging problems, which reduce recharge rates. In this study, the soil texture and mineral characteristics of alluvial soil in a planned artificial recharge system area were investigated to evaluate the possibility of chemical clogging during the injection of stream water. The primary minerals contained in the clastic particles are quartz, K-feldspar, plagioclase, and biotite, and the secondary minerals filling the pore space are illite, kaolinite and Fe-oxide. The fact that carbonate and sulfate are observed as secondary minerals in the pore space suggests that chemical clogging has not occurred by the interaction between the groundwater and surface water in the study area. Thus, monitoring soil properties, e.g., the formation and growth of secondary minerals in the pore space, is required to investigate the possibility of chemical clogging in artificial recharge systems.

• Journal of the Society of Disaster Information
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• v.20 no.2
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• pp.270-283
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• 2024

Purpose: Considering the rising frequency of earthquakes in Korea, it is crucial to revise the rainfall thresholds for landslide triggering following earthquake events. This study was conducted to provide scientific justification and preliminary data for adjusting rainfall thresholds for landslide early warnings after earthquakes through soil physical experiments. Method: The study analyzed the change in soil shear strength by direct shear tests on disturbed and undisturbed samples collected from cut slopes. Also, The study analyzed the soil strength parameters of remolded soil samples subjected to drying and wetting conditions, focusing on the relationship between the degree of saturation after submergence and the strength parameters. Result: Compaction water content variation in direct shear tests showed that higher water content and saturation in disturbed samples led to a significant decrease in cohesion (over 50%) and a reduction in shear resistance angle (1~2°). Additionally, during the ring shear tests, the shear strength was observed to gradually decrease once water was supplied to the shear plane. The maximum shear strength decreased by approximately 65-75%, while the residual shear strength decreased by approximately 53-60%. Conclusion: Seismic activity amplifies landslide risk during subsequent rainfall, necessitating proactive mitigation strategies in earthquake-prone areas. This research is anticipated to provide scientific justification and preliminary data for reducing the rainfall threshold for landslide initiation in earthquake-susceptible regions.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.143-152
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• 2016

To estimate the stability of a debris flow it is necessary to know the mass of surface soil, cohesion, slope, and friction angle. Given that the mass of surface soil is a function of soil thickness and mass density, it is important to obtain reliable estimates of soil thickness across a wide area. The objective of this paper is to estimate soil thickness using the elastic wave velocity with a new standard velocity. Tests are performed in debris-flow hazard areas, after which four profiles are selected to obtain the elastic wave velocity. Dynamic cone penetration tests are carried out to find the soil thickness at 18 points. The elastic wave velocity shows the area consists of 3~4 layers, and soil thicknesses are predicted by utilizing the new standard. The elastic wave velocity and dynamic cone penetration tests yield large differences in soil thickness. Therefore, this study shows that the new standard is useful not only in estimating soil thickness but also in improving the reliability of estimates of soil thickness.