• Journal of Korea Water Resources Association
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• v.53 no.8
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• pp.627-636
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• 2020

Debris flow disasters primarily occur in mountainous terrains far from cities. As such, they have been underestimated to cause relatively less damage compared with other natural disasters. However, owing to urbanization, several residential areas and major facilities have been built in mountainous regions, and the frequency of debris flow disasters is steadily increasing owing to the increase in rainfall with environmental and climate changes. Thus, the risk of debris flow is on the rise. However, only a few studies have explored the characteristics of flooding and reduction measures for debris flow in areas designated as steep slopes. In this regard, it is necessary to conduct research on securing independent disaster prevention technology, suitable for the environment in South Korea and reflective of the topographical characteristics thereof, and update and improve disaster prevention information. Accordingly, this study aimed to calculate the amount of debris flow, depending on disaster prevention performance targets for regions designated as steep slopes in South Korea, and develop an independent model to not only evaluate the impact of debris flow but also identify debris barriers that are optimal for mitigating damage. To validate the reliability of the two-dimensional debris flow model developed for the evaluation of debris barriers, the model's performance was compared with that of the hydraulic model. Furthermore, a 2-D debris model was constructed in consideration of the regional characteristics around the steep slopes to analyze the flow characteristics of the debris that directly reaches the damaged area. The flow characteristics of the debris delivered downstream were further analyzed, depending on the specifications (height) and installation locations of the debris barriers employed to reduce the damage. The experimental results showed that the reliability of the developed model is satisfactory; further, this study confirmed significant performance degradation of debris barriers in areas where the barriers were installed at a slope of 20° or more, which is the slope at which debris flows occur.

• Journal of Korean Tunnelling and Underground Space Association
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• v.17 no.3
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• pp.403-413
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• 2015

This paper presents the cutter bit damage due to the rotation speed of shield TBM cutter head in the mixed ground. The efficient of cutter bits and disk cutter are very important for tunnelling in mixed ground. In particular, this research is focused on the performance of cutter bits during excavation in mixed ground which is consist of the weathered soil and rock formation. In order to carry out this research, the experimental works are prepared performed by using the scaled shield TBM cutter bits evaluation machine developed. The mixed ground is prepared considering with a scale effect of tunnel size. Three different rotation speeds of shield TBM cutter head (i.e. 2, 3, 4 rpm) are applied in the experimental work. The drag forces acting on the cutter bits are measured at each cutter bit during rotation of cutter head. It is also analysed the variation of drag forces due to the rotation speed of shield TBM cutter head. The results of this research are clearly shown that the drag forces acting on the cutter bits are jumped up at the boundary between weathered soil and rock. It is also indicated that the jamping drag forces are increased with increasing the rotation speed of the cutter head. It is found from the research that the higher rotation speed of shield TBM cutter head will be high risk in the mixed ground. It is, therefore, suggested that the use of lower rotation speed of shield TBM cutter head is recommended for reducing the cutter bit damage in practice.

• Journal of Environmental Impact Assessment
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• v.25 no.4
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• pp.296-306
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• 2016

There is a growing interest in establishing a regional climate change adaptation policy as the climate change impact in the region and local scale increases. This study focused on the analysis of 32 regions on its characteristics of local climate change adaptation plans. First, statistic program R was used for conducting cluster analysis based on the frequency and budgets of adaptation plan. Further, we analyzed damage frequency from newspapers regarding climate change impacts in eight categories which were caused by extreme weather events on 2,565 cases for 24 years. Lastly, the characteristics of climate change adaptation plan was compared with damage frequency patterns for evaluating the adequacy of climate change adaptation plan on each cluster. Four different clusters were created by cluster analysis. Most clusters clearly have their own characteristics on certain sectors. There was a high frequency of damage in 'disaster' and 'health' sectors. Climate change adaptation plan and budget also invested a lot on those sectors. However, when comparing the relative rate among regional governments, there was a difference between types of damage and climate change adaptation plan. We assumed that the difference could come from that each region established their adaptation plans based on not only the frequency of damage, but vulnerability assessment, and expert opinions as well. The result of study could contribute to policy making of climate change adaptation plan.

• The Journal of Engineering Geology
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• v.17 no.3
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• pp.419-424
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• 2007

The contents were investigated by the monitoring survey from the soils and tailings caused by numerous abandoned mines in Korea. Cause heavy metals due to abandoned metal mines are raising significant environmental problems. But it is an important key such as a leaching and a transfer mechanism to evaluate contamination levels caused by abandoned mines. In this study the column test was carried in order to calculate a leaching level from soils and tailings. It was demonstrated that the leaching of Pb, Cd and Mn was expressed with similar behaviors and that of As and Cu was expressed with similar behaviors. For Zn, the leaching behavior was shown a serious leaching level with 40 mg/kg during the 45days. This was explained by Zn high contents of soils Zn in a natural world and ORP conditions where the leaching of Zn was occurred easily. Hence it was necessary that the survey of ORP was a key as well as total contents for the management of abandoned metal mines. We could estimate the chemical forms of heavy metals using the physical index such as ORP and pH and reduce the risk from heavy metals caused by abandoned metal mines.

• Journal of the Korean Society of Marine Environment & Safety
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• v.23 no.2
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• pp.139-145
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• 2017

Recently, gusts, typhoon and tsunamis have been occurring more frequently around the world. In such an emergency situation, a moored vessel can be used to predict and analyze other vessel behavior, but if the mooring system is destroyed, marine casualties can occur. Therefore, it is necessary to determine quantitatively whether a vessel should be kept in the harbour or evacuate. In this study, moored ship safety in an exclusive wharf according to swell effects on motion and mooring load have been investigated using numerical simulations. The maximum tension exerted on mooring lines exceeded the Safety Working Load for intervals 12 and 15 seconds. The maximum bollard force also exceeded 35 tons (allowable force) in all evaluation cases. The surge motion criteria result for safe working conditions exceeded 3 meters more than the wave period 12 seconds with a wind speed of 25 knots. As a result, a risk rating matrix (risk category- very high risk, high risk and moderate risk) was developed with reference to major external forces such as wind force, wave height and wave periods to provide criteria for determining the control of capabilities of mooring systems to prevent accidents.