• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.71-80
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• 2005

More than 100 bridges have been annually collapsed or seriously damaged by scouring in Korea. It is extremely hard to understand the complicated scour mechanism and estimate the scour depth with accuracy in fields, however since scouring is a very complex manifestation of sediment transport unable to describe with a simple mathematical tool. In order to obtain the reasonable solution to bridge scouring, therefore, the interdisciplinary co-operation is strongly recommended. In this study the special task force team for the scour problems around Incheon 2nd bridge piers is made, in which all kinds of scour oriented researches such as oceangraphic survey, hydraulic model test, numerical simulation, scour rate test, real-time scour monitoring, etc will be carried out. This paper provides this interdisciplinary procedure in details.

• Magazine of the Korean Society of Agricultural Engineers
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• v.28 no.1
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• pp.41-50
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• 1986

This paper attempts to qualitatively characterize scour erosion processes near USGS constriction type-I structures with vertical embankments and abutments. The scour dimensions and rates of sand beds around the structure models were measured in a rectangular flume. The test results showed that scour took place at a rapid rate at initial stages, which were followed by a stage of slow and general scour with greater extends. The maximum scour depth was observed near upstream corner of embankments. Empirical relationships for scour dimensions were derived, that were based on the results from a dimensional analysis of scour processes.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.593-596
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• 2008

The scour phenomenon involves the erosive potential of flowing water and the relative ability of the soil to resist erosion. The scour phenomenon in cohesive soils is much different from that in non-cohesive soils. Granular soils resist erosion by their buoyant weight and the friction between the particles. The soil particles are dislodged individually from the bed under the action of the eroding fluid. Scour in cohesive soils is much slower and more dependent on soil properties than that in non-cohesive soils. Therefore the analysis models for estimating erosion characteristics of cohesive soils should consider not only flowing water but also the relative ability of the soil to resist erosion. In this study, erosion characteristics for the clay-silt mixed soil will be analyzed as a fundamental study for development of bridge scour analysis and design system considering scour resistance capacity of a soil. For this analysis, the relationship between scour characteristics and soil properties was evaluated through scour rate test with Kaolinite samples remolded using various loading and contents of silt.

• 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.

• Proceedings of the Korean Geotechical Society Conference
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• 2002.03a
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• pp.337-342
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• 2002

A new apparatus called the EFA (Erosion Function Apparatus) has been built and tested to measure the erodibility of fine-grained soils. The EFA is a simple test to predict the erosion rate of fine-grained soils along with the corresponding velocity and shear stress. In addition, it is advantageous in predicting the scour rate for actual soil samples from bridge sites. The plot of erosion rate versus shear stress is the result of an EFA test. It Indicates the critical shear stress at which erosion starts and the rate of erosion beyond that shear stress. In order to measure the erodibilities of various soils, 14 Shelby Tube soil samples are collected from the actual bridge sites and tested using the EFA. The results of the EFA tests which are the relationships between erosion rates and shear stresses are presented in this paper and research continues to develop the correlation between the erosion function and the soil properties.

• Journal of Korean Society of Disaster and Security
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• v.12 no.3
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• pp.51-57
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• 2019

In recent years, the occurrence of localized torrential rain has increased due to the increase in heavy rainfall and massive typhoons caused by abnormal weather. As a result, the flow rate of small and medium-sized rivers in Korea is rapidly increasing, affecting the safety of bridges and increasing the risk of scour. However, the domestic bridge construction technology does not reflect the watershed characteristics of domestic rivers because the bridge scour depth calculation formula developed overseas is used to calculate the bridge scour depth. Therefore, this study is a basic study for prevention of bridge damage according to scouring phenomenon, and a comparative analysis was performed between the experimental data measured through hydraulic model test and the scour depth formulas applied in Korea. In addition, the statistical analysis between experimental data and scour depth formula shows that Coleman's (1971) formula estimates the best scour depth. The results of this study are expected to be used to calculate more accurate bridge scour depth in river design and bridge design.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.1
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• pp.163-168
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• 2020

Since the industrialization in the 1960s, Korea has been expanding its transportation infrastructure, such as building bridges. Owing to bridge construction, studies on stability review have been carried out, and stability-securing technology has been developed. On the other hand, these were applied mainly to the upper part of the bridge, so applications to the lower part are limited. In particular, scour at the bridge pier causes erosion in the riverbed and bridge collapse. Hence, prevention studies and countermeasures are needed. In this study, an empirical formula was developed to evaluate the scour depth of a bridge, which was calculated through multiple linear regression analysis using the hydraulic model study data conducted in previous studies. The formula, which had a value of 0.91, was applied to the model test data that was not used for development to verify the developed formula. When the pier scour depths were compared in 23 cases, the error rate was less than 20% in 16 cases (70%). The empirical formula developed in this study is applicable to pier scour-depth calculations. Further research will be needed to develop a more accurate empirical formula for pier scour-depth calculations, and it is expected to reduce bridge damage caused by scour.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.118-125
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• 2011

Conventional erosion function apparatus (EFA) which has been used to measure the hydraulic resistance of soil was improved to consider direction change of the current flow. Using improved apparatus, hydraulic resistance capacities of the artificially composed clayey soil and sandy soil were compared. Test result shows that scour rates which were measured under the bi-directional flow were much higher than those measured under unidirectional flow for both type soils. Scour rate of sandy soil was higher than that of clayey soil. Velocity averaged scour rate of specimen which was consolidated under the relatively large consolidation pressure is higher than that of specimen which is consolidated under small consolidation pressure, which means scour problem under bidirectional flow may be more serious for the deep seabed ground.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.24 no.1
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• pp.26-35
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• 2012

Until now, study on the hydraulic resistance characteristics of the ground at the river and the ocean current has been focused on the behavior under uni-directional flow without the direction change of flow. However, recent research result shows that scour rate which were measured under the bi-directional flow was much higher than those measured under uni-directional flow for both fine grained and coarse soil. Since the direction of inflow and return flow at the shore, where the structure will be constructed, is not always $180^{\circ}$, effect of the incidence angle on the hydraulic resistance capacity of the ground should be examined. Using the improved EFA which can consider the direction change of flow, hydraulic resistance capacities of the artificially composed clayey fine grained soil and clayey sandy soil under $0^{\circ}$, $90^{\circ}$, $135^{\circ}$, $180^{\circ}$ flow angle of incidence were assessed. Test result shows that hydraulic resistance capacity decreases and scour rate increase with the increase of the incidence angle between inflow and return flow. For the low consolidation pressure condition, hydraulic resistance capacity of the fine grained soil decreases rapidly. While the hydraulic resistance capacity of the coarse grained soil decreases more rapidly than fine grained soil under high consolidation pressure. Eventually since the larger the incidence angle between inflow and return flow, the larger the scour rate. Hydraulic resistance capacity under bi-directional flow($0^{\circ}{\longleftrightarrow}180^{\circ}$) should be examined for the design purpose.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.3
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• pp.154-161
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• 2017

The purpose of this study was to investigate the change of length, opening width, and number of openings effecting on topography change around artificial reefs under erosive wave condition. Hydraulic model test was conducted to see sediment transport around the structures and the relation among the installation condition of the artificial reefs, generated velocity, wave deformation, and topographic change was reviewed. Experimental results show that the sediment transport rate was reduced; however, the scour around the structures was increased under the condition of having a single opening compared to the structures having a plurality of openings which shows inversely proportional to the size of Lr/W.