• Journal of Industrial Technology
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• v.32 no.A
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• pp.47-55
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• 2012

Currently, we only estimate the average flood water level by the cross-sections of the river using one-dimensional numerical analysis when establishing the basic plans. However, the reliability decreases when it comes to the river bend. In river bend, the difference of water-level between the inside and the outside of the river arises by centrifugal force. And it is estimated less than what it could be estimated when establishing the plan with average estimate of flood level. It is apprehended that the exterior of the river will be under-constructed when establishing the scour depth only with the mean depth. In the case of local scour of the abutment, it is difficult to estimate its depth precisely, and it tends to be over-estimated in the case of the empirical formulas. Therefore, the modification considering the deviation of the water depth of the exterior of the river bend is needed. In observing the deviation of each formula in river bend, it is found: Andru's formula for 58%, followed by the Laursen's for 26%, and the C.S.U's for 17% in pier, while it is 44% for Froehlich's formula in abutment. Under the 500CMS of the flood discharge, the deviation of the scour depth between pier and abutment was about 10 %. However, in further flood discharge, it shows 24~58% the biggest in deviation of piers. It is concluded that the scour depth estimate should be done with 2-dimensional numerical analysis.

• Water Engineering Research
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• v.1 no.2
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• pp.159-168
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• 2000

In this paper, the increment of the local scour depth at piers by constructing the bridge between existing bridges is examined through the experiments in which 5 piers in the non-cohesive bed material in the experimental flume were installed. In the experiments the maximum distance of 25 times of the pier length and the maximum distortion width of 8 times of the pier width were utilized. Through the experimental studies, it was indicated that low flow, which can be characterized as the flow having low Froude numbers, the maximum bed configuration change is obtained when the piers are installed in the straight line in the flor direction without any distortion. However, In the high flow, which can be characterized as the flow having high Froude numbers, the maximum bed configuration change is obtained when the piers are installed with some distortion from the flow direction. The influence of the bed configuration by interaction between bridge piers is changed depending upon the Froude numbers, the distance between piers, and the distortion width between adjacent bridge piers. Also, because the scour patterns are affected by the bed configuration, the maximum scour should be increased by about 60% compared to that in a single pier if the interaction between bridge piers exists. It can be suggested that the maximum scour depth at bridge piers predicted by applying the existing equations should be increased if the interaction between bridge piers exist. Those cases are found when new bridges are constructed successively in the river in the urban area.

• Water for future
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• v.20 no.1
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• pp.41-47
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• 1987

Bridge piers are sometimes damaged by local scour. Although the problem of local scour around pier has been studied extensively, it has been difficult to estimate local scour depth quantitatively. This study is concerned with local scour around semicylindrical piers arranged in various types under the condition of clear water scour. Through dimensional analysis, it was found that scour depths were relative to Re, Fr, and Ns. In the case of semicylindrical piers, the variation of dimensionless scour depth with dimensionless time (effect of Ns, pier diameter and length, incidence angle) and the variation of scour depth with vortex intensity and resistance are investigated experimentally to obtain a formula. And formula for estimating the maximum depth of scour is obtained.

• Journal of Industrial Technology
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• v.28 no.B
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• pp.185-191
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• 2008

This study tried the 1st, 2nd dimensional numerical analysis according to the pier's shape, size and installing method in order to compare the depth of scour calculation method using the variables calculated by using the 2nd dimensional numerical analysis with the calculated depth of scour value by using the calculated variables by using the 1st dimensional numerical analysis. And then verified the problems occurring when the depth of scour is calculated by using the calculated values by using the 1st dimensional numerical analysis, as calculating the deviation depending on it.

• Journal of Korean Society of Disaster and Security
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• v.12 no.1
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• pp.1-9
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• 2019

The basic analysis of Soil and structural mechanics for the bridge substructure affected by the flow of water is sufficient in the construction of such bridges, but the stability of scour resulting from hydraulic phenomena is insufficient. In addition, it is not enough to estimate the scour depth of the bridge which reflects the watershed characteristics of the domestic river because it uses the formula for calculating the scour depth of the overseas piers in calculating the scour depth of the bridge. In this study, the application of the CSU (1993) formula, which is currently applied to the national river design criteria, was reviewed between the two formulas after calculating the scour after calculating the scour by applying another bridge deck scour calculation formula to take into account the uncertainty in the calculation of scour. In this study, in addition to the CSU (1993) formula, which is currently applied to Korean river design criteria, another scour depth calculation formula is applied to calculate uncertainty in scour depth calculation, was reviewed between the two formulas. The review confirmed that the SSE (%) showed a difference of at least 2.08%, up to 91.23%, and SSEn(%) at least 0.19%, up to 415.91%, when compared to the measured depth of the pier based on the hydraulic model experiment and the depth of the pier calculated with the nine scour depth formulas in use. In other words, it is confirmed that there are many differences between the scouring formulas of piers. The results of this study are expected to be used to estimate scour depth in future river design.

• 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.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.598-602
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• 2006

Local scour is associate with particular local types of vortex around bridge piers. This paper is method of protection local scour for the existing Busan City subway 3 Line bridge piers and Gupo large bridge piers. In order to take design of protection of local scour this bridge piers, We calculate the local scour hole of depth , scour width, riprap construction , filter construction by formulas. We had experimental hydraulic model test for this bridge piers in order to take proof for the calculation of local scour. We knew that the vortex intensifies the local flow velocities and acts to erode sediment from the scour hole and transport it downstream. As the result of hydraulic model test, we could suggest three types method of protection local scour this bridges. We knew that FHWA HEC-18(Richardson et al. 2001: Modified CSU) Formula is useful to checking calculation as application of field. One is pier protection using the sheet piles and riprap, the others are pier protection using the riprap with filter and to make renew Wall-caisson. The best method of protection for the existing Busan City subway 3 Line bridge piers and Gupo large bridge piers is pier protection using the sheet piles and riprap.

• Water for future
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• v.26 no.4
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• pp.107-115
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• 1993

The results of laboratory experiments on the clear-water local scour of cohesionless bed sediment at three types of the pier shape are presented. Based on the experimental data, the relative equilibrium depth of local scour is related to the pier shape, the geometric standard deviation of the bed material, the velocity ratio and the pier Froude number. The relative local scour depths were smallest ant the round-nosed pier and remarkably reduced at the non-uniform bed sediment, comparing with those at the uniform bed material. The effect of sediment grading on the local scour reduction was discussed and compared with Raudkivi and Ettema's experiments.

• Journal of Korea Water Resources Association
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• v.32 no.1
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• pp.49-59
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• 1999

In order to understand the present situation of bridge scouring and to provide the fundamental information for bridge design, in-situ measured data is analyzed for bridge scours at small and medium streams in the heartland of Korea. The physical parameters affecting the bridge scouring such as flow depth, velocity, pier length and width, scouring depth, and the angle between flow and pier are extensively surveyed and measured. According to the locality and the pier type data are classified to analyze. With these data, some important factors for the scour depth such as flow depth, angle and Froude number are investigated and applied to existing formulas proposed by many researchers. In addition, the computational results are compared with the measured and some of the applicable formulas in this region are recommended.

• 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.