• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.12
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• pp.8-14
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• 2019

A drop structure, one of the representative river-crossing structures, is constructed to stabilize a riverbed. On the other hand, the structure interrupts the continuity of the river and causes the destruction of the hydro-ecological environment. Therefore, laboratory experiments of a natural type of drop structure with low differences were performed, and the empirical formula of a local scour hole is proposed. Four experimental flow rates were tested for various types of the drop structure models with 28 test cases. Based on the scour test, it was confirmed that the maximum scour depth occurs rather than the result of applying the previously proposed scour depth formulae. Correlation analysis of the major factors of scour hole at the downstream of the drop structure revealed a strong correlation between the upstream flow characteristics, drop structure height, and total crossing length of the drop model. In addition, the depth and length estimation formula of the maximum scour hole were proposed using the dimensionless variables and validated. In the future, it is also expected that more accurate scour prediction and calculation can be derived by conducting experimental studies and numerical analysis considering the various bed materials and flow conditions.

• Journal of Korea Water Resources Association
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• v.34 no.6
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• pp.641-649
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• 2001

This study analyzed the general scour characteristics around group pile foundations through laboratory experiments. The experiments were performed for the pile groups consisting of 4, 9, 15 and 35 piles to investigate the effects of pile number, mean velocity and the angle of attack on the scour hole shape, and the magnitude and the position of maximum scour depth. Results reveal that the maximum scour depth for 4 and 9 piles have almost same values with single pier case regardless of approach velocity. The scour depth for 15 and 35 piles, however, increases as the mean velocity increases and reaches up to 2.2 times of maximum scour depth for single pier case. As the number of piles increase, the single scour holes are superposed and the overall scour hole turned out to be rectangular shape. The experimental results for the case of 35 piles indicate that the scour depth has the maximum value at angle of attack of 35 degree and that the main scour hole is formed in diagonal direction.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.455-465
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• 2006

In this study, the effect of scour was evaluated by regional and geotechnical characteristics and back data were accumulate for the design against scour through the local erosion characteristics evaluation of the Inchon coast. The erosion characteristics for the undisturbed soil samples collected near the main locations at the Incheon 2nd bridge, the Hwangyeong bridge, and a coast road in Songdo, are determined quantitatively through the scour rate tests. On the basic soil properties test, the bed around the Inchon coast chiefly consists of fined grained soils, and the soil samples were classified as silty clay(ML) or clay(CL) under the Unified Soil Classification System. On the scour rate test, the critical shear stress increases when the undrained shear strength increases as of the general trend of fine grained soils, and the average scour rate for the maximum velocity by 100 year flood is 173mm/hr at the Incheon 2nd bridge, 67mm/hr at the Hwangyeong bridge and 10mm/hr at a coast road in Songdo, respectively. Comparing to the scour rate of coarse grained soil, that of the bed around the Inchon coast is turned out to be very low. Therefore, the relative ability of the bed around the Inchon coast to resist erosion is assumed to be very high.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.2B
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• pp.169-175
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• 2008

The clear-water scour experiments were conducted to shed light on the unsteadiness of the horseshoe vortex around a bridge pier since the fluctuations of velocity components and unsteadiness of the horseshoe vortex can be considered as one of the main factors on local scour. The characteristics of the flow speed and turbulence around a bridge pier was examined using an Acoustic Doppler Velocimeter (ADV) and the flow visualization with kaolin clay particles upstream of a bridge pier. The outcomes of this study on the turbulence characteristics related with scour mechanism were presented with the quadrant analysis, the integral time scales, and the bed shear stresses before and after scouring, respectively. The bed shear stress before scouring was approximately quadruple times higher than that of the equilibriums state. It implies that the unsteadiness of the horseshoe vortex would play a significant role in the initial development of scour depth. Therefore, the bimodal distribution of flow velocity was identified as one of the mechanical properties of the horseshoe vortex and the unsteadiness of horseshoe vortex can be one of the major characteristics to understand the flow sturucture and local pier scour.

• Journal of the Korean Society of Hazard Mitigation
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• v.3 no.2 s.9
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• pp.139-145
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• 2003

This study is to propose reduction effect of scour depth and a optimum size of circular collar through experimental analyses with various collar sizes. To do so, we carried out hydraulic model experiments. In the case of with considering the collar, the effect of reduction of scour depth increased according to the increase of collar size. When size of collar is 2 as the ratio of collar diameter(W) to pier diameter(D), scour depth is decreased about 67% and deposition height is increased about 70%. The optimal size of collar proposed in this study is W/D=2 by analyzing reduction effect of scour depth, size of scour hole, and deposition height.

• Journal of Environmental Science International
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• v.11 no.10
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• pp.1075-1080
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• 2002

The hydrological frequency of the flood in July 2000 at Seosi stream basin in Gurye and the bed scour of the stream channel were estimated to investigate the bed scour related with Jeongjang bridge collapse. The storm over the basin in July 2000, 303mm/day was 103year frequency rainfall and the equivalent flood was 2580cms. As the results of 100year and 30year flood application, flood level 30.78~31.38m and mean velocity 3.79~4.03m/s were appeared. And the purification project of Seosi stream increased the velocity of the section near to Jeongjang bridge by the improvement of conveyance at the downstream. The local scour at pier was the major factor of bed scour at Jeongjang bridge site and the total scour at pier No.6 was increased from 2.32m to 2.45m by the purification project.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2B
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• pp.187-195
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• 2006

A bridge scour management system is developed to evaluate the vulnerability of bridge piers to scour and to help establish effective disaster measures, taking into account the locality and scour characteristics in Korea. This system is programmed using the techniques of the geographical information system(GIS) for the storage, retrieval, and display of information regarding to bridge scour. The system functions are basically divided into two parts; prioritization and maintenance. Bridges are initially screened and prioritized for bridge scour inspection and evaluation using the basic information which is obtained from the office review. The bridge scour evaluation including site investigation is performed and the vulnerability of bridge piers is categorized into six groups taking into account the local scour depth, foundation bearing capacity, foundation type, foundation depth, and present scour condition. The system tabulates and plots all the data and the results.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.2
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• pp.128-137
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• 2012

This paper deals with the local scour around a pipeline exposed to combined waves and current in the shallow water zone. To investigate the characteristics of the scour around a pipeline on the sea bed, experiments were performed according to the various pipe diameters, wave periods, wave heights, and current velocities. Wave generator and current generator were used for the experiments. Two current directions were used ; co-direction and counter direction to the waves. With the experimental results, the correlations between the scour depths and non-dimensional parameters such as Keulegan-Carpenter number(KC), Froude number(Fr), Ursell number(Ur) and velocity ratio were analysed. The relative scour depths were found obviously to be dominated by the wave component when the velocity ratio function approaches zero and those are gorverned by the current component when the velocity ratio approaches unity. Velocity ratio function was approved to be a proper parameter which is able to express the change of the scour in the combined wave and current zone. Also considering the orbital velocity and the current velocity into Fr numer and KC number respectively, scour depths show more favorable correlationship with the parameters.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.1
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• pp.216-222
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• 2006

This study is a simulative Paper on scour around piers. As materials on the river bed have been changing through erosion, transportation and accumulation, so does the waterway's section. Analyzing them through the BOSS SMS. this study deals with the local-scour characters with the change of shapes in row piers which have been built in the identical direction of water flow.

• Journal of the Korean Geotechnical Society
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• v.18 no.2
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• pp.13-21
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• 2002

A new method called S-SRICOS is proposed to predict the local scour depth around bridge piers. The S-SRICOS method is a simplified version of the SRICOS method which was developed to predict the scour depth versus time curve around bridge piers. The SRICOS method which considers the time effect based on the soil properties and the hydraulic parameters can handle a multi-flood hydrograph and multi-layer soil systems with the SRICOS program. An attempt was made to simplify the method to the point where only hand calculations would be required. The concept of the equivalent time was developed leer this purpose. The S-SROICOS method requires only 4 parameters such as pier width, design bridge life, design velocity corresponding to the design bridge life, and initial scour rate of the soil. The S-SRICOS method was verified against 55 cases of the scour depth results using the SRICOS method.