• Title/Summary/Keyword: scour depth

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Applicability Evaluation on the Analytical Formulas of the Scour Depth Estimation in the Bight River (교량세굴심 산정을 위한 만곡부하천에서의 산정식 적용성 평가)

  • Park, Soo-Jin;Park, Jae-Wan
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.13 no.10
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    • pp.4845-4852
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    • 2012
  • This research calculated the scour depth of bridge according to inflow and outflow changes of stream's flood discharge and curves by applying scour depth formula for piers and abutments, and by comparing and examining them, evaluated the applicability of scour depth formulas. Overall, if the angles of flood discharge and inflow and outflow increase, the deviation rate of scour depth in bight increased. Especially the deviation rate was 58% at the inflow and outflow angle of $105^{\circ}$ that the bridge plan for this geography need careful examination. Next, as a result of calculating the deviation rate of scour depth at the bight by scour depth formulas, in case of pier, Andru formula showed 58% deviation rate, Laursen formula showed 26% deviation rate, and CSU. formula showed 17% deviation rate. In the case of abutment, Froehlich formula shows 44% deviation rate that when applying above scour depth formulas, scour depth calculation considering repairable characteristics of bight is necessary. Finally, about inflow and outflow angles of $45^{\circ}{\sim}135^{\circ}$ that showed big deviation rate of scour depth, this research performed regression analysis of deviation rates of scour depth due to flood discharge to suggest the regression formula.

Statistical Characteristics of Pier-Scour Equations for Scour Depth Calculation (교각세굴심 산정 공식의 통계적 특성)

  • Lee, Ho Jin;Chang, Hyung Joon;Heo, Tae Young
    • 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.

Experimental Study on Local Scour around Bridge Piers by Scour Protection Devices (세굴보호장치에 의한 교각주위의 국부세굴 실험)

  • 최기봉;김응용
    • Journal of the Korean Society of Safety
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    • v.15 no.1
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    • pp.126-131
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    • 2000
  • This study based on the laboratory works, analyzes factors affecting local scour in order to understand various characteristics of the local scour surrounding bridge piers. Attached with scour protection device as a method for decreasing local scour, it carries out the laboratory experiments and calculates the scour depth. From the experiments attached with the scour protection devices, it seems possible to reduce the scour depth as the protecting plate, column and sacrificial piles are built in the same height with flume bed at pier or footing upstream interrupted falling-flow. And then it could reduce scour depth. The paper presents the following research results: First, the decreasing degree of scour depth is in order of protecting column, protecting plate, sacrificial piles and non-protecting facilities. However, it shows no meaningful difference between protecting column and protecting plate. Second, when $L_p/b$=0.5~1, the decreasing effect of scour depth reached the maximum of 40 percents.

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Analysis of Statistical Characteristics of Pier-Scour Depth Formula Using Hydraulic Experiment Data (수리모형실험 자료를 이용한 교각 세굴심 산정공식의 통계적 특성 분석)

  • Kim, Jong-Sub;Chang, Hyung-Joon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.22 no.6
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    • pp.349-356
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    • 2021
  • Since the 1960s, traffic infrastructure, such as bridges, has increased rapidly in Korea as urbanization and industrialization progressed due to economic growth. As the scale of the bridge becomes larger, stability analysis of the superstructure of the bridge is being conducted actively, but scour stability analysis for the substructure of the bridge has not been conducted sufficiently. This study is a basic investigation to prevent large-scale disasters caused by scouring in bridge piers. A simple linear regression model was used to analyze the scour depth calculated through seventeen scour depth calculation formulae, and the scour depth measured through hydraulic model experiments. As a result, the Coleman (1971) formula was the best method among the scour depth calculation formulae, and the Froehlich (1987) formula was the most effective method for calculating the scour depth. In addition, a review using a simple regression model confirmed that the scour depth calculation formulae of CSU (1993), Coleman (1971), and Froehlich (1987) can predict a similar scour depth by reflecting domestic stream characteristics. This study can calculate the scour depth reflecting the environmental conditions of Korea in future stream design.

Estimation methods of maximum scour depth in steep gravel-bed bend channel (급경사 자갈하상 만곡수로의 최대세굴심 산정공식 평가)

  • Cho, Jaewoong;Nam, A-Reum;Woo, Tae Young;Park, Sang Deog
    • Journal of Korea Water Resources Association
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    • v.49 no.6
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    • pp.529-536
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    • 2016
  • The existing methods to estimate the maximum scour depth in the bend of steep gravel bed channel have been evaluated by the hydraulic movable-bed experiments. In the $90^{\circ}$ bend steep-slope channel paved with the fluvial gravels which are uniform in size and have a mean diameter of 43mm, the maximum scour depths due to the flow discharge and the gradient of bed slope have been investigated and compared with the scour depth computed from the equations. The local scour has occurred in conditions that the bed slope is steeper than 0.02 and the $F_r$ is greater than 0.95. Except Lacey's equation and Zeller's equation, the existing methods computing the maximum scour depth overestimate the maximum scour depth in the steep channel with the very coarse gravel bed. However, Lacey's equation with the bed material size and Zeller's equation considering the approach channel gradient and the bend angle may be relatively used to estimate the scour depth in bend of the steep gravel-bed river.

Temporal Variation of Local Scour Depth in the Downstream of Weir with Shapes (보 형상 변화에 따른 하류부 세굴의 시간적 변화)

  • Yeo, Chang Geon;Lee, Seungoh;Yoon, Sei Eui;Song, Jai Woo
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.31 no.4B
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    • pp.353-360
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    • 2011
  • The objectives of this study were to analyzes temporal variation of local scour depth in the downstream of weir with shapes. Prediction of maximum or equilibrium scour depth was the main focus of engineers and researchers in the downstream of weir. However, it is necessary to analyzes temporal variation of local scour depth in the downstream of weir to predict real time scour depth. Experiment were performed with various weir shapes like sharp crest and inclined stepped with time variation and non-dimensional scourhole shapes, scour depths were proposed. A formula for predicting scour depths with temporal variation for weir were proposed through non-linear regression analysis. Temporal variation of scour depths could be estimated with suggested formula and 4 input data (Equilibrium scour depth, weir height, overflow depths, and water depth downstream). Suggested formula could make it possible to design a apron and bed protection economically in the downstream of a weir by considering flood duration time.

Review on Applicability of Local Scour Depth Calculation Formula in River (하천 세굴심 산정을 위한 교각 세굴심 산정식의 적용성 검토)

  • Min, ByungYun;Chang, HyungJoon;Lee, HoJin;Kim, SungDuk
    • 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.

Experimental Estimation of Shear Stresses at Pier-Front (교각전면부 하상재료의 입도분포에 따른 전단응력 산정에 관한 실험적 연구)

  • Park, Yoon Sung;Kang, Jun Ku;Yeo, Woon Kwang
    • Proceedings of the Korea Water Resources Association Conference
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    • 2004.05b
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    • pp.429-433
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    • 2004
  • According to researchers, the influential factors of scouring are generally divided into three factors: the flow conditions, the type and position of structures, and the characteristics of bed materials. In addition, scouring is affected by the 3-dimensional turbulent boundaries, the unsteady flow, the movement of sediment in the scour-hole area, the approach flow velocity and depth, the width of bridge foundation/pier, and the particle size of bed materials. However, it is difficult to estimate the scour depth near bridge piers when all conditions are factored in at once. Therefore, for reasonably accurate estimates of scour depth, it is essential to consider sufficiently the flow force and resisting force for scour. That is, to determine the shear stress concerning the bed material distribution is needed. In this study, the experiments were performed under the condition of a steady state of flow. As a result, scouring occurred at velocity ratios of 0.476,$(V/V_c=0.476)$, and the scour depth was increased linearly as the velocity ratio increased. in addition, the average values of shear stress ratio at zero scouring depth in both rectangular and circular piers were approximately 7$(\tau_c/\tau_{approach})$ and in the case for same size bed particle material. The results of this study can be used for the fundamental material for estimating the scour depth of bed materials.

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An Experimental Study on Reduction Effect of Scour Depth arounding Uniform Cylindrical Pier with Various Size of Circular Collar (원환 크기의 변화에 따른 균등원통교각 주위의 세굴심 감소효과에 관한 실험적 연구)

  • Sim, Ou-Bae;Song, Jai-Woo
    • 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.

Pier Scour Prediction in Pressure Flow

  • Choi, Gye-Woon;Ahn, Sang-Jin;Kim, Jong-Sup
    • Korean Journal of Hydrosciences
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    • v.6
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    • pp.23-37
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    • 1995
  • In this experimental paper, the maximum scour depth at pier was student. The model of the pier of San Gye bridge in the Bocheong stream was set for the experimental studies. Several model verification processes were conducted through the roughness comparisons between model and prototype, pursuing scour depth variations with time depending upon channel bed variation, the comparison of the ratios between falling velocities and shear velocities in the model and prototype, and the comparison of pier scour depths between experimental data and field measuring data. The experiments were conducted in the free flow conditions and pressure flow conditions. The maximum scour depth at piers in the pressure flow conditions is almost twice as much as compared to the free flow conditions. Also, the maximum scour depth variations are indicated in the figures based on the Froude numbers, opening ratios, water depths and approaching angles in the free surface flow conditions.

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