• Journal of the Korea Academia-Industrial cooperation Society
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• v.17 no.6
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• pp.737-743
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• 2016

Coastal hazards such as high waves are expected to increase due to global climate change. Therefore, we investigated new armor unit structures for disaster prevention. Recently, a concrete caisson has been used in many breakwaters against high waves in South Korea, but the demand for concrete armor unit has increased due to the high cost and many installation requirements. Though many new armor units have been developed over the world since Tetrapod in 1950, few have been used due to lack of systematical development. The representative armor units in current use have many advantages, but they cannot be applied to waves higher than 8 m. One of the new armor units developed by the design guide based on recent trend and hydraulic model experiments were conducted. The new armor unit was developed as a single layer due to cost effectiveness. However, the thickness is close to 1.5 times by overlapping the alphabet A and V. It showed higher overtopping compared to a double layer because of the thickness and the high packing density. It has a high interlocking vertically but low horizontally. It shows good stability at 9 m in model testing.

• Journal of Wetlands Research
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• v.22 no.1
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• pp.31-38
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• 2020

Weirs are to secure amount water of streams and drop structures are to enhance stabilization of stream bed and bridges are to connect isolated region, which are called stream crossing structures. In the stream design criteria, directions for minimum size of structures are suggested to secure stability of stream crossing structures. However the sizes of almost all existing weirs and drop structures are not satisfied with the stream design criteria and only 22 percent of the peirs of bridges are satisfied. To enhance hydraulic stability of existing weirs and drop structures, it is required that the ratio of bed protection to apron should be above 3.3. According to factual survey of structures in the sample streams, it has been shown that the longitudinal slope of rapid works with 1:20 is the most reasonable to design velocity if existing weirs and drop structures are rehabilitated into rapid works. It has been known that violating freeboard and span length of piers should make existing bridges reconstructed or removed. However, comprehensive review including deterioration level of bridges, special regulation for span length, etc. should be considered to determine rehabilitation plan of bridges. In this study, a procedure has been suggested to improve hydraulic stability of weirs, drop structures and piers of bridges. Sound environment of stream and reduction of natural disaster could be achieved by improving stability of cross structures, which could be obtained by governmental budget and active stream management including observance of design criteria.

• Korean Journal of Remote Sensing
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• v.35 no.6_3
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• pp.1221-1233
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• 2019

Estimating damage in each sector that can be caused by volcanic ash deposition, is very important to prepare the volcanic ash disaster. In this study, we showed predicted-Korean-volcanic-ash damage of each sector by using volcanic ash diffusion simulation and spatial-data-based volcanic ash damage sector in previous study. To this end, volcanic ash related base maps were generated by collecting and processing spatial information data. Finally, we showed Korean-volcanic-ash-deposition damages by sector using the collected Mt. Aso volcanic ash scenarios via overlapping analysis. As a result, volcanic-ash-related damages were expected to occur in the 162 and 134 districts for each Aso volcanic ash scenarios, since those districts exceeds the minimum volcanic ash damage criterion of 0.01 mm. Finally, we compared possible volcanic ash damages by sectors using collected and processed spatial data, after selecting administrative districts(Scenario 190805- Kangwon-do, Kyungsangbuk-do; Scenario 190811-Chuncheon-si, Hongcheon-si) with the largest amount of volcanic ash deposition.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8879-8888
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• 2015

When the disaster like earthquake in urban area occur, due to the collapse accidents for subway, tunnel space with buildings or underground area, enormous property and human damage are happened. Specially, since it is difficult to identify survived status of humans within collapsed debris and accurately buried locations of the humans, inputs of considerable time and manpower for rescuing them are required. Besides, secondary damage can be occurred by additional collapses. The aim of this study is to propose a stochastic location positioning method that enables to provide aid information by determining locations of mobile devices for buried persons in 2-D plane using wireless communication technologies. This study selected a detection method for buried persons based on Wi-Fi signal, and identified characteristics of signal strengths by distance unit. Using these methods, a stochastic location detection model in 2-D plane was built. It is expected that this technology will be utilized as a core technology that can protects safety and human life of the public by providing data for rescuing quickly buried persons in cases of national disasters for future.

• Journal of the Korean Association of Geographic Information Studies
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• v.12 no.1
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• pp.54-63
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• 2009

Various methods have been employed for acquiring beach surface data, which are used to monitor shoreline changes due to beach erosion. This study explores the possibility of constructing and implementing a surface model of beach using data acquired with a terrestrial laser scanner and RTK-GPS. Digital images and three-dimensional data of beach areas acquired at 20 cm intervals using a laser scanner were used to create a digital surface model covered with digital image. Seven months later, the beach area was surveyed using an RTK-GPS, and another beach model was constructed using the data collected with an accuracy of 1.9 cm. The use of a terrestrial laser scanner is expected to ensure acquisition of good quality results and help deal with seasonal changes in beach areas. Because readings obtained with the RTK-GPS are dependent on the number of sampling points in beach model, difficulties are encountered when fixing the survey points. However, RTK-GPS could be used to implement a three-dimensional model by correcting the hidden parts in images obtained using a terrestrial laser scanner. Therefore, an RTK-GPS and a terrestrial laser scanner can be used in combination to obtain more precise data for the construction of beach model data.

• Journal of the Korean GEO-environmental Society
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• v.16 no.11
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• pp.13-19
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• 2015

Construction materials using soil which is the most common material around us have many advantages, but their long-term durability and sensation of walking as pavements have problems. Therefore, they are used after compaction or mixed with various hardening agents such as lime and cement for strength enhancement. However, studies on the behavior of pavement materials mixed with environment-friendly hardening agents or admixtures to improve walking property are still insufficient. In this study, therefore, in order to evaluate the appropriate mixing ratio and field application characteristics of pavement materials using mixed soils with environment-friendly hardening agents and natural materials such as wood chips, mechanical tests were performed to evaluate the rational mixing ratios and the ball test was performed as an elasticity test to evaluate the field applicability. The results suggest that the content of wood chips should be selected at 1.5% or lower according to the purpose of the structure, and the hardening agent at 10~15%. The evaluation results for GB/SB coefficient ratio which indicates the walking property show that the appropriate mixing ratio of the hardening agent in terms of the sensation of walking is 15% of lower, but different mixing ratios should be chosen according to the proportion of wood chips.

• The Journal of Engineering Geology
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• v.26 no.1
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• pp.63-70
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• 2016

The aim of this study is the safety and an accident prevention in limestone terrain by the underground tunneling. The geology of the study area consists of a Paleozoic sedimentary sequence dominated by limestone, sandstone, shale, and carbonaceous shale. The sequence gently dips to the northeast but the joint contains steep with variable trend. A significant fracture zone is developed in the limestone and shale beds, sub-parallel to bedding, and follows in part the limestone-sandstone contact. Monitoring of groundwater levels in the area shows marked fluctuations in the water table, which repeatedly rose to a level of -4 m before sinking to -15 m. These cycles occurred in mid-May, 2007 and in early and middle June. The data indicate that these fluctuations were unrelated to rainfall that occurred during the study period. We infer that the fluctuations were associated with the development of underground karstic networks along the deep fracture zone, and overlying ground subsidence is likely related to the rapid sinking of groundwater and the associated strong downward suction force.

• Fire Science and Engineering
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• v.27 no.6
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• pp.8-14
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• 2013

This research is to evaluate the fire extinguishing performance at a mixing ratio of pressurized air in the fire extinguishing system of compressed air foam (CAF) which injects compressed air into foam liquid and then discharging. The experimental device is made use of exclusive foam extinguishing facility for compressed air foam that is produces based on Canada National Laboratory and UL 162 standard, apply model of oil fire (B Class) 20 unit in accordance with "Standard of Model Approval and Product Inspection for Fire Extinguishing Agent" to the fire Extinguishing model. Compressed air is injected through the air mixture and study the tendency depending on increasing air foam ratio 1 : 4, 1 : 7, 1 : 10. In addition, the comparison experiments between synthetic surfactants foam and AFFF carry out with it at the air foam ratio 1 : 4. As a result, in the condition of same discharging flow, fire extinguishing effect of AFFF is the fastest at the air foam ratio 1 : 7 and the slowest at 1 : 10. Moreover, the fire extinguishing effect of AFFF in the comparison expeiments between AFFF and synthetic surfactants foam is faster than the other.

• Fire Science and Engineering
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• v.27 no.6
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• pp.104-114
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• 2013

This study is intended to figure out the effects of supervisors' transformational leadership on organizational culture and innovation in the fire fighting organization. To achieve this, a survey was carried out to fire officers from the National Emergency Management Agency and Seoul Metropolitan Fire & Disaster Headquarters. The results are as follows. First, the effect of supervisors' transformational leadership on organizational culture showed that supervisors' transformational leadership had an effect on group culture, norm culture and rational culture by sub-factors of organizational culture in the fire fighting organization. Second, the effect of organizational culture on organizational innovation showed that group culture and rational culture had an effect on organizational innovation. Third, the effect of supervisors' transformational leadership on organizational innovation showed that supervisors' transformational leadership had an effect on organizational innovation. As for findings stated above, supervisors' transformational leadership had positive effects on organizational culture and innovation in the fire fighting organization. Consequently, supervisors' energetic and change-seeking leader-ship for junior staffs with existing organization-and new generation-oriented new thinking system can contribute to rational culture and development-oriented innovation based on norms in the group.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.31 no.6_1
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• pp.471-481
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• 2013

Recently, the frequency of debris flow disaster has increased, which is one of the natural disasters during extremely heavy rainfall condition. This paper described the analysis method about deposition characteristics of debris flow using topographic characteristics of debris flow path. First, we observed topographic changes by differencing high- resolution LiDAR DEMs acquired before and after the occurrence of debris flow event. We assumed that deposition on outside of debris flow path was generated by movements due to the inertia of debris flows. Then, we analyzed three topographic characteristics of debris flow path: slope in flow direction, transition angle of flow path, and the net efficiency(L/H) of debris flows defined by the ratio of transport length(L) and elevation difference(H). We applied this method to Umyeon Mountain debris flow event in July 2011. The results showed that deposition on outside of debris flow path due to the inertia of debris flows was significantly related to the transition angle of debris flow path. Also, we figured out that there were more frequent such depositions in locations where the ratio of 'transition angle / (L/H)' is over 8.