• Korean Journal of Environment and Ecology
• /
• v.36 no.1
• /
• pp.87-101
• /
• 2022

This study analyzed changes in the vegetation structure of 16 permanent plots (experimental and control) installed in Wando Arboretum in 1996 to monitor the long-term change process of evergreen broad-leaved forests in warm temperate. Especially, this study discusses the effects of trial treatment (selection cutting and plant introduction), introduced as a restoration technique in 1996, on vegetation development. In communities dominated by Quercus acuta in the canopy (permanent plots 1 through 3), this species's mean important percentage (MIP) decreased, and the evergreen broad-leaved species was introduced from outside increased, likely to change the vegetation structure in the future. The expansion of the evergreen broad-leaved species group was also confirmed in Q. acuta-deciduous broad-leaved forests (permanent plots 5 and 7) and Pinus densifloraforests (permanent plots 9 and 10). In the experimental plots where thinning was carried out, the zoochory (the dispersal of seeds by birds), Cinnamomum yabunikkei, Neolitsea sericea, Machilus thunbergii, etc., and the expansion of the influence of evergreen broad-leaved species were remarkable, so it is considered to have effectively promoted the vegetation development in warm temperate forests. Although evergreen broad-leaved species were planted in the experimental plot to change vegetation structure, it seems the effect on the change was weak due to the small amount of planting. Compared to other vegetation types, the change in the vegetative structure of the pine forest to an evergreen broad-leaved forest was clear due to the decline of P. densiflora and P. thunbergii.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.28 no.7
• /
• pp.1111-1119
• /
• 2022

Tourism projects through islands in the waters of Sinan-gun became active, and as a result, a total of 13 marine bridges connecting islands were completed. However, the marine bridge constructed in the fairway is dangerous for traffic. Particularly, in the case of the marine bridge connecting two islands, the width of the fairway is extremely narrow, therefore the risk is higher. In this study, we evaluated the risk of collision between marine bridge piers and ships using the IALA Waterway Risk Assessment Program (IWRAP), a risk assessment model for port waterways, based on a maritime traffic survey on the coastal bridge in Sinan-gun. The results, indicated that No.1 Sinan bridge had the highest probability of collision and most of the transit ships were coastal passenger ships. In addition, No.1 Sinan bridge was the place where the most collision accidents occurred among the marine bridge piers in the target sea, and the cause this study was analyzed. An analysis of the satellite images of the sea environment of No.1 Sinan bridge using an image processing method, confirmed that obstacles that could not be seen in the chart existed nearby the bridge. As a result, traffic was observed to be concentrated in one direction, unlike two-way traffic, which is a method of inducing traffic of bridges to avoid obstacles. The risk cause analysis method using the image processing technique of this study is expected to be used as a basic research method for analyzing the risk factors of island bridge in the future.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.35 no.1
• /
• pp.1-12
• /
• 2023

Along with the growing interest in renewable energy development, Korea's west coast is one of the favorable regions for tidal power. Tidal power using tidal barrages that work like hydroelectric dams is a representative method of tidal power through long-term operation, but the promotion of tidal power projects is being delayed or stopped due to impacts on ecological changes, reproduction, water column processes and hydrology. In order to reduce the high construction cost and environmental cost problems caused by tidal power using tidal barrages, in this study, field experiments were conducted to develop and verify the performance of tidal power generation devices applicable to sea areas where dykes are already installed. As a result of conducting five cases of experiments using two water tanks, pipe lines, open channels, and water turbine and generator, the possibility of developing a power generation system capable of generating more than 10 kW output and more than 60% efficiency were confirmed. The results of this study can be used for small-scale tidal power by utilizing the existing dykes of the west coast.

• Korean Journal of Environment and Ecology
• /
• v.36 no.6
• /
• pp.575-581
• /
• 2022

Brown rats (Rattus norvegicusBerkenhout, 1769) were eradicated from Sasudo Island (33°55'13.04" N, 126°38'19.98" E), an uninhabited island designated as Natural Monument No. 333 and the largest breeding site for the streaked shearwater (Calonectris leucomelasTemminck, 1835) in South Korea. Twelve eradication studies were conducted from November 2015 to February 2021. The survey was conducted using a line census method that entailed slow wandering throughout the island and identifying starting and returning points. Capture traps were installed around traces of Rattus norvegicus,such as excrement and identified holes. As a result, 2 to 6 individuals were captured at each instance, except for the last time, when no individuals were captured. It is hypothesized that brown rats arrived at Sasudo Island via vessels arriving at the island for leisure and fishing. After the damage to streaked shearwater caused by brown rats was confirmed in 2006, entry to Sasudo Island was strictly prohibited through security measures, and marine clean-up programs that began in 2013 and continuous capturing since 2015 have been successful in eradicating brown rats. To maintain and manage the condition in Sasudo Island, preservation and management measures, such as strict visitor control, are necessary to prevent the inflow of new brown rats in the future.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.29 no.2
• /
• pp.127-138
• /
• 2023

A variety of decarbonized energy sources are being developed globally to realize carbon neutrality (Net Zero) by 2050 as a measure to address the global climate crisis. As the Korean government has also established a Renewable Energy 3020 policy and promoted energy development plans using solar or wind power, large-scale offshore development projects not present before in coastal waters, such as offshore wind farms, are being promoted. From ships' point of view, offshore facilities present obstacles to safe navigation, and with the installation of marine facilities, ship collisions or contact accidents between ships and marine facilities may occur in the narrowed water areas. In addition, there are concerns about environmental pollution and human casualties caused by marine accidents. Accordingly, we review overseas and domestic offshore wind farm development plans, analyze whether institutional devices are in place to ensure the safe passage of ships in wind farm areas, and study the safe operation of large-scale offshore wind farms and safe passage of ships along the Korean coast by comparing overseas legislative cases with domestic laws and presenting a proposal to illuminate the legal blind sectors.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2020.06a
• /
• pp.150-150
• /
• 2020

본 연구에서는 수리모형실험을 통하여 원형 다단 실린더 게이트 형식의 취수시설에서 발생하는 공기연행을 분석하였다. 수리모형실험의 원형은 경상북도 청도군에 위치한 운문댐의 "운문댐 안전성 강화사업"에서 계획되고 있는 신설취수탑을 기준으로 상사법칙은 Froude상사법칙을 적용하고 1/20의 모형 축척을 가지는 취수탑의 국부모형에 하류단 수위를 고려하기 위해 유량조절시설을 설치하여 실험을 실시하였다. 실험조건은 크게 두 가지로 구분하였으며, 수면으로부터 유입구 상단부까지의 거리 ∆h1(m)과 유입부 저수지 저류 수위와 하류단 유량조절시설간의 수위차인 ∆h2(m)이며, ∆h1에 대한 조건은 0.01m~0.06m로 0.01m 간격으로 6가지, ∆h2에 대한 조건은 0.10m~1.70m로 0.20m간격으로 9가지로 이를 조합하여 총 54개 CASE에 대해 진행하였다. 실험결과 공기연행 발생 시 그에 따른 영향을 평가하기 위해 발생 정도에 따라 미발생(Not Occur), 간헐적(Intermittent), 빈번한(Frequent), 지속적(Continuation), 공기 폭발(Air Explosion)로 분류하였으며, 각 공기연행 발생 시 취수유량의 감소율 및 영향을 분석한 결과 간헐적 공기연행 발생 시 최대 약 3.75%의 취수유량 감소, 빈번한 공기연행 발생 시 취수유량은 전체적으로 10%, 최대 약 13.19% 감소하였으며, 지속적 공기연행 발생 시 발생 이후 ∆h2증가에 의한 취수유량의 증가가 거의 이루어지지 않으며, 최대 56.25%의 취수유량이 감소, 공기 폭발 발생 시 취수유량의 영향은 지속적 발생과 비슷하나 관내 공기 포집 후 유입구로 방출 시 관에 강한 충격을 주어 안정성에도 큰 영향을 미칠 것으로 판단되어, 이에 안정성 및 취수유량 감소율을 고려하여 빈번, 지속, 공기 폭발 발생 영역에서의 취수는 적합하지 않으며, 공기연행 미발생 및 간헐적 발생 영역에서의 취수 시 목표 취수유량이 1.00~4.00(㎥/s)일 때 ∆h1= 0.40m 이상, 4.00~9.30(㎥/s) 일 때 ∆h1= 0.60m 이상, 9.30~9.53(㎥/s) 일 때 ∆h1=0.80m 이상, 9.53~9.65(㎥/s) 일 때 ∆h1= 1.00m 이상에서 취수유량 감소율 3.75% 이내로 취수유량의 확보가 가능하다. 이러한 결과는 원형 다단 실린더 게이트 형식의 취수시설에 대해 취수 시 수면와류에 의한 Air Core와 그에 따른 공기연행의 발생 조건과 영향을 수리모형실험을 통해 확인함으로써 실제 운용 시 보다 안정적이고 효율적인 운용에 대한 자료로 활용될 수 있을 것으로 판단되며, 추가로 수치해석을 통한 비교 및 공기연행과 관내 공기포집 정도에 대한 연구를 통해 보다 정확한 자료제시가 가능할 것으로 판단된다.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2021.06a
• /
• pp.303-303
• /
• 2021

소양호 유역의 만대가아자운지구는 2015년 비점오염원 관리지역으로 재지정 되면서 흙탕물 저감을 위해 중앙정부 차원에서 발생원 관리대책, 유출경로 관리정책 및 양한 비점오염 저감시설 등의 노력을 기울이고 있다. 하지만 상류 유역에서는 지속적으로 흙탕물이 발생되고 있으며, 뚜렷한 비점오염 저감효과가 나타나지 않고 있다. 본 연구에서는 정밀조사를 통해 흙탕물 발생 우심 소유역을 분석하고자 하였다. 정밀조사를 위해 관리지역별 하천 및 구거를 분석하였으며, 이를 통해 만대·가아·자운지구별 각 57지점, 31지점, 72지점에서 강우시 수질 모니터링을 수행하였다. 만대지구의 탁도는 167 NTU~7,970 NTU, SS농도는 164.3 mg/L~5,718.0 mg/L 로 관리지역 중 탁도 및 SS 농도가 높았으며, 시행계획상 구분된 소유역별 평균 탁도와 평균 SS농도는 만대천 상류구간이 가장 낮고, 상명천 소유역과 청룡안골, 방추골천, 방추골일천이 흐르는 소유역에서 높게 나타났다. 가아지구의 탁도는 17 NTU~962 NTU, SS농도는 17.8 mg/L~1,020.0 mg/L 로 조사되었으며, 평균 탁도와 평균 SS농도는 가아지구 말단 소유역에서 가장 낮고, 상류 소유역에서 높게 나타났다. 가아천 상류는 탁도 410 NTU와 SS농도 575.0 mg/L, 하류는 탁도 167 NTU, SS농도 197.3 mg/L로 나타나 상류에서 하류로 갈수록 탁도와 SS농도가 낮아졌으며, 상류 유역은 비점저감시설이 밀집해 있음에도 불구하고 다량의 흙탕물이 발생하는 것으로 나타났다. 그러나, 자운지구는 비점오염저감시설이 집중적으로 설치된 상류 유역에 비해 하류 소유역에서 탁도와 SS농도가 높은 것으로 조사되었다. 자운지구의 탁도는 7 NTU~761 NTU, SS농도는 10.8 mg/L~1,199.0 mg/L로 조사되었으며, 평균 탁도와 평균 SS농도는 자운지구의 하류 소한천 소유역이 가장 낮고, 조항천 말단 소유역에서 높게 나타났다. 정밀조사 결과 탁도 및 SS농도가 높게 나타나는 소유역은 공통적으로 고랭지밭의 비율이 높게 나타났기 때문에 고랭지밭에서 발생되는 흙탕물을 효과적으로 관리하기 위해서는 최근 환경부에서 시범 추진하고 있는 농경지 완화조성, 토지 매수사업, 식생완충대 조성 등의 발생원 관리대책 확대 추진이 필요할 것으로 판단된다. 또한 소양호 유역의 비점오염원관리지역은 2020년 비점오염원 관리대책 시행계획이 수립되어 향후 2026년 비점오염 저감 대책이 추진됨에 따라 지속적이고 정밀한 모니터링이 필요할 것으로 판단된다.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.12 no.6
• /
• pp.407-416
• /
• 2010

A new tunnel auxiliary method is proposed in this paper which utilizes the concept of cavity expansion for tuunel reinforcement by forming an umbrella arch on the roof of tunnel. When an inflatable pipe is inserted and expanded by pressure in the bore hole of umbrella arch, the ground around the bore hole can be compacted so that the stress condition above the tunnel perimeter is favorably changed. In order to verify the reinforcement effect of new concept, pilot-scale chamber test, trapdoor test and numerical analysis were performed and compared. In pilot-scale chamber test, three types of inflatable pipes are tested to verify the capability of expansion, and the results arc compared with analytical results obtained by applying cavity expansion theory and with results obtained from finite clement analysis, and the experimental results showed agreeable matches with analytical and numerical ones. Numerical analysis of a tunnel and trapdoor test applied with the inflatable pipes are also performed to figure out the reinforcement effect of the proposed techniques, and the results implied that the new method with 3 directional inflatable pipe (no pressure to downward direction) can contribute to reduce tunnel convergence and face settlement.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.1B
• /
• pp.1-9
• /
• 2009

This study is focused on the analysis of loop characteristics of stage-discharge relation which is widely used for the production of discharge data and the simulation of loop stage-discharge relation using the numerical model. Analysis of consecutive stage and discharge data at 3 points revealed that loop of stage-discharge relationship is very strong. This means that the existing single stage-discharge relation may include large amount of error. Various flood events are simulated in mainstream of Han river with one-dimensional numerical model. The calculated stage data are compared with measured data. Especially continuous field-flow measurements concurrently collected with an Acoustic Doppler Velocity Meter (ADVM) on Hangang bridge in the case of 2007 flood event are used to verify the model applicability of estimating flows in open channels. This comparison shows that numerical model is an accurate and reliable alternative for making the real stage-discharge relation. Simulation of stage-discharge relation by a numerical model at Paldang and Hangang bridge showed good agreements with measured one, so it may be possible to generate real loop stage-discharge relation with properly calibrated and verified numerical model. It can be concluded that results of this study can contribute to error analysis of conventional single stage-discharge relation and development of loop stage-discharge relation with numerical model.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.27 no.6
• /
• pp.79-85
• /
• 2023

Skid resistance pavement is an accessory to the road and is a facility for the safe driving of cars by increasing the skid resistance of road pavement. In particular, in bad weather conditions such as snow, rain, and black ice, the skid resistance performance of skid resistance pavement greatly affects the safety of road traffic and drivers. However, BPT(British Pendulum Tester) has a test area of only 0.009 m², making it difficult to represent the overall packaging surface. A reliable method of evaluating slip resistance performance is needed for maintaining non-slip packaging. In this study, the conventional BPT test and the skid resistance performance evaluation method of the PFT(Pavement Friction Tester) and µGT(Micro Grip Tester) tests were compared through guidelines and standard investigations and applied to the field skid resistance performance evaluation. In addition, skid resistance pavement with different skid resistance performance was installed at the test-bed and actual road demonstration sites to compare BPN(British Pendulum Number), SN(Skid Number), GN(Grip Number), and to derive correlations for each performance evaluation method. As a result of the experiment, SN and GN showed similar skid resistance performance, and the GN value was derived similar to BPN × 0.01.