• Water Engineering Research
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• 제7권1호
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• pp.21-28
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• 2006

The scouring process is complex and subject to many factors. Recently, experiments for real-time bridge scour monitoring have been active as means for a more reliable scour prediction. Riverbed materials are an important factor in bridge scouring; therefore, an accurate estimation of riverbed material is critical in predicting a scour. As a part of this approach, an ultrasonic sensor, which can not only detect river bottom during floods but can also be installed lose to the underwater structures, was developed. This sensor is able to map the river bottom using an ultrasonic waves with the characteristics of the returning wave, reflected from an object or bottom ground. The reflected wave is unique according to the situations, or materials below. Therefore, it would be possible to identify the consisting materials of a riverbed if we could reveal each characteristic in the received signals. In this study, a preliminary experiment was performed in the laboratory to identify and classify received signals, which is unique to each material. The analysis of this experiment gives the graph, which makes it possible to identify materials of the river bottom through the ultrasonic signals. The proposed graph was verified through a comparison with the actual field data measured in river.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2005년도 학술발표회 논문집
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• pp.1138-1142
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• 2005

The tidal river is a river affected by tide, which causes the water level to rise and fall two times everyday periodically. The local velocity across the river could be very fast because of the cross-sectional characteristics of the river even though it's not a rainy season. Therefore extreme local scour could take place around hydraulic structures such as piers and caissons due to backward flow velocity. For the construction of pier foundation of Ilsan-bridge In the Han River, the field observations were performed to get the velocity and water level. The numerical analysis was performed by HEC-RAS(UNET). The relationship between measured maximum velocity and calculated mean velocity is achieved, which is used to estimate the velocity and water level as the construction is proceeding. Countermeasures for scour were designed with the results of the hydraulic analysis to avoid potential damage during construction work. According to the results of monitoring, the velocity increase after temporary road embankment was negligible, from which it is considered that the degradation of main channel compensated for the constriction of cross-section by embankment.

• Structural Monitoring and Maintenance
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• 제6권2호
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• pp.85-101
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• 2019

The effects of foundation scour depth and riverbed condition on the natural frequencies of a typical cross-river integral abutment bridge have been studied. The conventional operational modal analysis technique has been employed in order to extract the modal properties of the bridge and the results have been used in the Finite Element (FE) model updating procedure. Two tests have been carried out in two different levels of water and wet condition of the riverbed. In the first test, the riverbed was in dry condition for two subsequent years and the level of water was 10 meter lower than the natural riverbed. In the second test, the river was opened to water flow from the upstream dam and the level of water was 2 meter higher than the natural riverbed. The results of these two tests have also been used in order to find to what extend the presence of water flow in the river and saturation of the surrounding soil affect the bridge natural frequencies. Finally, the updated FE model of the bridge has been applied in a series of parametric analyses incorporating the effect of piles' relative scour depth on the bridge natural frequency of the first four vibration modes.

• 한국구조물진단유지관리공학회 논문집
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• 제18권2호
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• pp.126-133
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• 2014

유체의 흐름에 의해 교량의 교각 및 교대 주변의 하상재료가 유실되는 현상을 말하는 교량 세굴은 교량 파괴의 주요원인이다. 그리고 홍수시 교량의 수위는 교량자체 안전뿐만 아니라 교량을 이용하는 사용자의 안전을 위해도 반드시 확인해야 한다. 따라서 교량의 안전관리를 위해 세굴과 수위계측은 필수적이라 할 수 있다. 본 연구는 기존의 세굴계측의 한계를 극복할 수 있는 새로운 교량세굴 측정방법을 개발하고 현장 검증을 통해 개발 기술의 우수성과 타당성을 확인하였다. 새롭게 개발된 세굴 및 수위 측정방법은 교각에 수직으로 계측장치를 설치하고 일정간격으로 설치된 온도 센서의 온도를 측정하여 수면 위치와 수중 지면의 위치를 추정하는 방법으로 대기온도와 수온, 수온과 수중 지온의 차이를 분석하여 수면 및 수중 지면의 위치를 추정하는 방법이다. 개발 기술은 절대적인 온도 차이뿐만 아니라 대기와 수중 그리고 지중의 일변화량이 서로 다르다는 점을 이용하여 수면의 위치와 수중 지면 위치를 보다 정확하게 추정할 수 있다. 개발 기술의 검증을 위해 소하천 및 실험실, 그리고 교량 교각에서 개발기술을 시범 적용하고, 매질별 온도분포 특성, 시간에 따른 온도변화 추이 등을 분석하여 개발기술이 효과적으로 교량 세굴과 수위를 계측할 수 있는 방법임을 확인하였다.

• 한국지반환경공학회 논문집
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• 제15권9호
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• pp.37-45
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• 2014

해상 기초구조물은 수평하중에 지배적인 영향을 받으며, 세굴 발생으로 인한 모노파일의 근입깊이 및 지반강성의 감소는 구조물의 안정성을 저하시키게 된다. 본 연구의 목적은 전기비저항 모니터링 기법을 이용하여 기초구조물의 연직 세굴심도를 평가하고, 전단파 토모그래피를 통해 지반강성의 공간적 분포 및 변화양상을 파악하는 것이다. 해상 기초구조물에서의 세굴현상을 모사하기 위하여 하단이 고정된 모형 모노파일을 중앙에 위치시킨 후 모래 및 시멘트를 이용하여 모형 지반을 조성하였다. 전기비저항을 측정하기 위하여 모형 모노파일에 수평 및 수직배열로 구분하여 전극쌍을 설치하였으며, 전단파 측정을 위해서 사각형 프레임에 벤더 엘리먼트를 $7{\times}7$로 배열하였다. 세굴도 변화에 따라 위치별 전기비저항과 전단파 토모그래피 이미지를 측정하였다. 실내실험을 통해 세굴도 변화에 따른 위치별 전기비저항 변화와 전단파 토모그래피를 관찰하였고, 각 단계별 지반 변화양상을 파악하였다. 위치별 전기비저항의 변화를 통해 최대세굴심도 평가가 가능했으며, 전단파 토모그래피를 통해 세굴로 인한 지반의 전단강성 변화를 추정할 수 있었다. 본 논문에서 제시한 전기비저항과 전단파 토모그래피는 세굴현상으로 인한 해상 기초구조물 주변의 지반특성을 모니터링하기 위한 매우 효과적인 방법이 될 수 있음을 보여준다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.1305-1312
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• 2006

본 연구는 하천유황 모니터링을 위하여 유비쿼터스 기반의 무선통신기술 인프라를 이용하여 개발한 하천정보 수집용 계측시스템에 관한 것이다. 이 시스템은 사용자에 의하여 자유이동하면서 하천의 수심, 수질 및 유속(유량)을 실시간으로 관측 및 모니터링 할 수 있도록 하였다. 개발된 하천부이 시스템은 하천의 수위, 수질(수온, pH, 탁도, 전도도 등) 자료를 획득함과 동시에 획득 장소의 위치정보를 획득할 수 있도록 GPS 모듈을 추가하였다. 또한 이 하천부이는 무선RF 조정이 가능하여 원하는 위치에서의 정보를 손쉽게 획득할 수 있도록 하였다. 획득된 자료는 자료 중계기(Gateway system)의 Zigbee 무선통신을 이용하여 전송하게 하였으며, GIS 모니터링 툴을 이용하여 자료를 확인하고, 확인된 자료는 CDMA 원거리 무선통신을 이용하여 서버컴퓨터로 전송할 수 있게 하였다. 서버컴퓨터에 전송된 하천의 정보는 DB 자동구축과 함께 웹기반의 실시간 모니터링이 가능하도록 하였다. 연구개발 결과는 독립적인 하천정보 모니터링 시스템으로 활용 가능할 뿐만 아니라 하천교량 세굴과 그 밖의 호수 및 해양 환경 모니터링 시스템 등으로 국내외에 많은 분야에 활용될 수 있을 것으로 판단된다.

• 한국환경복원기술학회지
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• 제10권3호
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• pp.71-87
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• 2007

In order to improve and manage rationally for Youngdam creek in Haman-gun, the channel change, water quality and ecological adaptation etc. were evaluated by monitoring during three years. The distinct differences of channel characteristics appeared in the extents of bed excavation and the revetment methods because overall reconstruction was occurred intense disturbance of width expansion and levee construction etc. The scour and deposition were caused according to channel characteristics of ripple and pool, and the adaptation of vegetation was distinguished from each revetment methods clearly. Water quality was maintained first class on the basis of BOD as 0.5~1.5mg/${\ell}$. The vegetation appeared in 380 species close-to-nature river improvement before, but 64 species it after one year, 159 species it after two year and 158 species it after three year. The animal life appeared in 123 species of close-to-nature river improvement before, but 103 species it after one year, 116 species it after two year and 119 species it after three year.

• 한국환경복원기술학회지
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• 제16권2호
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• pp.137-153
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• 2013

In order to assess the effects of ecosystem and landscape in around spur dikes, this study had carried out monitoring on the changes of ecosystem and morphologic characteristics in around spur dikes that had been settled in bend of Youngcheon River. The study site was a short reach with length 190m, spur dikes were installed in March, 2008. Monitoring of the site had been started in May 2008 and had been completed September 2011. The results are as follow ; 1) Spur dikes that were installed for channel stabilization are performing effectively hydraulic functions at flooding time. 2) Spur dikes that were installed in water colliding front of river bend brought about sediment deposition between those and formed pools around front of those. Therefore, it was verified to create various physical characteristics in the aspect of channel topography and flow consequently. 3) The survey results that was carried out in October 2008 showed to emerge 25 species of plant, 9 species of fish and 17 species of benthic macroinvertebrates, but the survey results in October 2010 showed to emerge 74 species of plant, 12 species of fish and 19 species of benthic macroinvertebrates. In particular, plant species that emerged in 2011 increased about three times more than those in 2008.

• 한국환경과학회지
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• 제27권7호
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• pp.477-488
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• 2018

In this study, heavy metal levels at the sediment monitoring network site upstream of the Gangjeong-Goryeong weir in the Nakdong River were surveyed from 2012 to 2016. We assessed the sediment pollution level using various pollution indexes based on ICP-MS analysis. The stream sediment pollution assessment standard, established through Regulation No. 687 of the National Institute of Environmental Research (2015), pollution load index (PLI), potential ecological risk index (RI), and mean PEL Quotient (mPELQ) were used to evaluate the sediment pollution level. We verified the representativeness of the monitoring point through the distribution of sedimentation and scour behavior by river bed surveying using anacousticDopplercurrentprofiler.

• Geomechanics and Engineering
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• 제25권1호
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• pp.49-58
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• 2021

The resistance of soil to the tractive force of flowing water is one of the essential parameters for the stability of the soil when directly exposed to the movement of water such as in rivers and ocean beds. Biopolymers, which are new to sustainable geotechnical engineering practices, are known to enhance the mechanical properties of soil. This study addresses the surface erosion resistance of river-sand treated with several biopolymers that originated from micro-organisms, plants, and dairy products. We used a state-of-the-art erosion function apparatus with P-wave reflection monitoring. Experimental results have shown that biopolymers significantly improve the erosion resistance of soil surfaces. Specifically, the critical shear stress (i.e., the minimum shear stress needed to detach individual soil grains) of biopolymer-treated soils increased by 2 to 500 times. The erodibility coefficient (i.e., the rate of increase in erodibility as the shear stress increases) decreased following biopolymer treatment from 1 × 10-2 to 1 × 10-6 times compared to that of untreated river-sands. The scour prediction calculated using the SRICOS-EFA program has shown that a height of 14 m of an untreated surface is eroded during the ten years flow of the Nakdong River, while biopolymer treatment reduced this height to less than 2.5 m. The result of this study has demonstrated the possibility of cross-linked biopolymers for river-bed stabilization agents.