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

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6D
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• pp.541-552
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• 2010

The light rail transit (LRT) having bus lines as subsystem is being constructed or planned in the suburban area of metropolitans and medium size cities. However, there is difficulty in establishing the service coverage (SC) of the LRT because the LRT is a completely new transit mode in Korea. The purpose of this study is to provide the basic data and techniques to be used for establishing the SC of the future LRT by understanding the SC characteristics of buses and subways and building models to estimate the walking distances of their users. Busan City is selected as the study city and the SC's of buses and subways are surveyed simultaneously. A total of 9 variables for 82 stations are collected and the cluster analysis is conducted about the variables. The station areas are divided to three types of CBD (Central Business District), sub-CBD and regional center based on the analysis. A station in each area is selected as the study station. At the walking distance (WD) analysis for each mode, the 80 percentile WD of the subway is 672 m and that of the bus is 472 m. In comparing the SC's of both modes by the type of station areas, there are not significant differences between the SC's of sub-CBD and regional center except CBD. At analysis of the relationship between the personal attributes and the WD, for subway users the WD of female is longer than that of male and apartment residents use subway more positively than single house residents do. For the models to estimate the walking distances, the simple regression models were built employing the income as independent variable by dividing the stations into CBD abd non-CBD stations.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2D
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• pp.167-173
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• 2009

In general, an influenced area of merging section is defined as 500 m including 100 m upstream and 400 m downstream. However, from an observation of the actual traffic flow, it is found that merging effect influences more on downstream than upstream. In this study, an influenced area of merging section on freeway is analyzed by using turbulence which is defined as conflicts between vehicles. In order to overcome the limits of existing traffic flow detection system established with intervals of about 500 m, this study uses raw data collected from the detectors which are established in entrance ramps with similar road conditions. To divide data of each point into similar road conditions, the data of total 72 hours is sorted by Level of Service. An influenced area analyzed by standard deviation of speed is 700 m section of highway, including 300 m upstream and 400 m downstream, for both right and left ramps. It is the result including upstream 200 m more than previous studies.

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

• The Journal of the Acoustical Society of Korea
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• v.42 no.4
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• pp.285-297
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• 2023

The present study aims to investigate the acoustic performance of the creative convergence classrooms in Korea used by elementary school students under the age of 9 introduced through the school space innovation project. In order to do this, acoustic performances of three creative convergence classrooms were measured. The measured acoustic parameters were background noise levels, Reverberation Time (RT), D₅₀, Speech Transmission Index (STI), and Inter-Aural Cross Correlation (IACC). Also, acoustic parameters including Transmission Loss (TL) and standardized level difference (D_nT) have been measured for the analysis of sound insulation performance of walls. In addition, the noise level was measured according to the opening conditions of doors and windows in the classroom. As a result, background noise level was measured at an average of 28.0 dB(A) to 32.8 dB(A) when the air conditioner was not operated, and the RT did not exceed 0.6 s. There were differences in IACC according to various desk layouts, and IACC values were high in the center line and the seats near the sound source. In particular, higher IACC was measured at the seats on the center line facing the source squarely. Regarding noise level in the classroom according to the opening conditions of doors and windows, the standards were exceeded when all windows, or windows and doors front onto the corridor were opened.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.3B
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• pp.297-306
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• 2008

In order to determine the effects of lock gate expansion at the Lake Youngsan and Yeongam as well as increase in the width of the connecting channel of the two lakes on flood control downstream of the Youngsan River, an unsteady hydraulic flood routing was conducted by combining the Lake Youngsan and Yeongam as a single connected system. The coupled operation of the two lakes was found to have little effect when the widths of the lock gates and the connecting channel are set at the current level. It was also found that increasing the width of the connecting channel as well as the lock gate of the Lake Yeongam is an effective means of reducing the stage of the Lake Youngsan, whereas an increase in the width of the Lake Youngsan's lock gate had a relatively smaller effect. The extended width of the connecting channel leads to a rise in the stage of the Lake Yeongam. In order to reduce the elevated stage, The Lake Yeongam's lock gate must be expanded along with the Lake Yeongsan's lock gate. The analysis found that the stage of the Lake Yeongsan can be effectively controlled through adjustment of opening and shutting criteria of the connecting channel's lock gate, when diversion discharge between the lakes is increased as a result of expanding the width of the connecting channel.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.6A
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• pp.597-605
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• 2009

The safety of expressway bridges was estimated by checking the external condition rank based on the nondestructive inspection and material test and by measuring load carrying capacity based on the result of load test. Although the load carrying capacity of the bridges was clearly low compared to the design standard, it was examined that many of the bridges have good external condition rank relatively. Also, it can be assured that load carrying capacity shows a considerable difference according to various condition even though the bridges have similar construction year and a structural type. Therefore, this study showed various problems of the current safety measurement of expressway bridges by considering the status of the expressway bridges, external condition rank, and method of safety diagnosis and repair, rehabilitation for maintenance. Based on the existing data of over 400 expressway bridges, the load carrying capacity was analyzed quantitatively considering bridge type, serviced life, design live load, external condition rank and traffic count as variables. The result of this study will be expected to provide the basic information for a reasonable safety assessment of expressway bridge.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.2
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• pp.175-188
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• 2009

When a new tunnel is excavated by the drill and blast method near pre-existing underground structures or tunnels due to the region restricted condition such as urban area, the ground will be relaxed by the excavation. In this case, issues can be created in terms of stability of pre-existing underground structures. One of major factors determining the stability of pre-existing underground structures can be a separation distance between pre-existing underground structures and a newly excavated tunnel. The region of ground relaxation defined by the plastic zone due to new excavation can be varied by separation distance. In this study, in other to estimate an influence of new tunnel excavation in terms of separation distance on the stability of pre-existing large pipelines, two-dimensional scaled model tests using plaster were performed for six models which have a different separation distance, The results show that based on the analysis of induced displacement during tunnel construction, the displacement decreases as the separation distance between large pipeline and new tunnel is increased until the distance is 2.5 times of pipeline diameter. Beyond this point, however, the displacement has become stabilized.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.353-359
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• 2010

Cementitious matrix based composites are vulnerable to the drying shrinkage crack during the curing process. In this study, the drying shrinkage induced fracture behavior of the fiber reinforced concrete is simulated and the effects of the fiber reinforcement conditions on the fracture characteristics are analysed. The numerical model is composed of conduit elements and rigid-body-spring elements on the identical irregular lattice topology, where the drying shrinkage is presented by the coupling of nonmechanical-mechanical behaviors handled by those respective element types. Semi-discrete fiber elements are applied within the rigid-body-spring network to model the fiber reinforcement. The shrinkage parameters are calibrated through the KS F 2424 free drying shrinkage test simulation and comparison of the time-shrinkage strain curves. Next, the KS F 2595 restrained drying shrinkage test is simulated for various fiber volume fractions and the numerical model is verified by comparison of the crack initiating time with the previous experimental results. In addition, the drying shrinkage cracking phenomenon is analysed with change in the length and the surface shape of the fibers, the measurement of the maximum crack width in the numerical experiment indicates the judgement of the crack controlling effect.

• Korea Science and Art Forum
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• v.16
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• pp.157-169
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• 2014

Lake Biwa Canal was a dream project that reminds us the passion and innovation of Kyoto Citizens more than water supply. It is a modernization project combining engineering knowledge and scientific technology, which started transportation by ship through big-scale civil construction as well as supplying electricity as the first waterpower plant in Japan, and it overcame the physiographic limit through adopting unique method of waterway transportation. Lake Biwa Canal, which has tangible and intangible culture heritage value as the traditional space of Kyoto, the Old Capital of 1200 years, conceives a cultural meaning that is connected through various mutual relation as well as scientific technologic factor. Lake Biwa Canal is not only the function for supplying water to gardens and temples of Kyoto region, but it is also a cultural fruit that is formed by complex causal relationship of various contents such as geographical and environmental background, the phases of the times, local development policy, political circumstances and religions. This study is aimed at interpreting the value of Lake Biwa Canal multilaterally by the convergence of cultural and technological aspects through the view of the world which the age tried to pursue, focusing on the construction of Lake Biwa Canal which was accomplished in the process of promoting the modernization of Kyoto.