• Title/Summary/Keyword: scour depth

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Estimation of Local Scour at Piers Using Artificial Neural Network (인공신경망을 이용한 피어의 국부세굴 평가)

  • Park, Hyun-Il;Shin, Jong-Hyun
    • Journal of the Korean Geotechnical Society
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    • v.24 no.11
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    • pp.17-24
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    • 2008
  • It is known that scour at bridge piers is one of the leading causes of bridge failure. However, the mechanism of flow around a pier structure is so complicated that it is difficult to establish a general empirical model to provide accurate estimation for scour. Especially, each of the proposed empirical formula yields good results for a particular data set but can't show reliable predictability for various scouring data set. In this study, an alternative approach, that is, artificial neural networks (ANN), is proposed to estimate the local scour depth with numerous field data base. The local scour depth was modeled as a function of seven variables; pier shape, pier width, pier length, skew angle, stream velocity, water depth, $D_{50}$. 426 field data were used for the training and testing of ANN model. The predicted results showed that the neural network could provide a better alternative to the empirical equations.

Scour around spherical bodies due to long-crested and short-crested nonlinear random waves

  • Myrhaug, Dag;Ong, Muk Chen
    • Ocean Systems Engineering
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    • v.2 no.4
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    • pp.257-269
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    • 2012
  • This paper provides a practical stochastic method by which the maximum equilibrium scour depth around spherical bodies exposed to long-crested (2D) and short-crested (3D) nonlinear random waves can be derived. The approach is based on assuming the waves to be a stationary narrow-band random process, adopting the Forristall (2000) wave crest height distribution representing both 2D and 3D nonlinear random waves, and using the regular wave formulas for scour and self-burial depths by Truelsen et al. (2005). An example calculation is provided.

A Experimental Study on the Depth of Scour to Formula Estimated of the Pattern Pier (원형 교각의 세굴심 산정식 개발에 대한 실험적 연구)

  • Baek, Kyung-Won;Park, Soo-Jin;Lee, Yeong-Seop;Choi, Han-Kuy
    • Journal of the Korean Society of Hazard Mitigation
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    • v.10 no.2
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    • pp.83-90
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    • 2010
  • This study was intended to compare and evaluate the value obtained from the existing formula for calculating the depth of scour and the valey from experimental model through the investigation of hydraulic characteristics and pier data in the area of rivers at Gangwon Province, and the sensitivity analysis, which is a statistical method, of the elements affecting the scour of the pier was carried out. As a result, a deviation between the values of existing formulas and experimental model reached about 1.09%$^{\circ}$63.98%, indicating that existing formula was found not to be appropriate at the rivers in Gangwon Province. A sensitivity analysis was carried out based on value obtained from experimental model and consequently, the elements affecting the scour were size of pier accounting for 64% and water depth accounting for 36%. Finally, a formula for calculating the scour of the pattern piers at the rivers in Gangwon Province was developed using the regression analysis.

Scour Protection Effect around the Monopile Foundation (모노파일 기초 주변의 세굴방지 효과에 관한 연구)

  • Kim, Seon Min;Kim, Jong Kyu;Kim, Yong Kwan;Seo, Seong Ho
    • Journal of the Korean Society for Marine Environment & Energy
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    • v.20 no.2
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    • pp.84-90
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    • 2017
  • In this research, a three-dimensional Computational Fluid Dynamics(CFD), scour characteristics around monopile was grasped and the effect of circular ring type scour protection on reducing protection was assessed. When Torsethaugen(1975) found that the scour area and its depth were coincided quantitatively On the ground of previous findings, after scour was assessed in terms of sea current velocity, we also found that the tendency of maximum scour depth and its width were increased as the sea current velocity was increased. The experiments were performed by attaching ring-circular typed scour protection under the bottom in order to reducing scour around the constructs of monopile type and showed reduced scour approximately by 68.5%. In addition, there were reduction of downward flow and bottom velocities, suggesting that scour protection reduce the effect of downward flow on scour.

Field Investigation of Bridge Scours in Small and Medium Streams(2) (우리나라 중.소 하천의 세굴특성 조사연구(2))

  • Yeo, Un-Gwang;Gang, Jun-Gu
    • 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.

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Prediction of Scour Potential Distributions in a Shallow Plunge Pool (얕은 감세지내의 세굴능 분포형태의 예측)

  • 손광익
    • Water for future
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    • v.27 no.3
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    • pp.35-43
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    • 1994
  • Because a failure to provide enough plunge pool depth can create a risk to the structural stability of the psillways or dams, many researchers have proposed experimental formulas for claculating ultimate scour depth under jet issued from spillways and pipe culverts. For the design purposes of a plunge pool, scour potential distribution is important as much as the ultimate scour depth is. In this study scour potential distributions near the jet impinging point on a porous plane which can simulate a real cohesionless movable flat bed has been measured. Experimental results showed that scour potential distributions are geometrically similar to each other provided the angle of jet impact was the same. Statistical analysis of experimental results showed that scour potential distributions for the design purposes of a plunge pool could be expressed by a single equation within a range of this experiment. The proposed formula for the prediction of scour potential distributions agrees well with experimental measurements.

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Analysis of Scour Phenomenon around Offshore Wind Foundation using Flow-3D Model (Flow-3D 모형을 이용한 해상풍력기초 세굴현상 분석)

  • Park, Young-Jin;Kim, Tae-Won
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.18 no.11
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    • pp.690-696
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    • 2017
  • Various types of alternative energy sources to petroleum are being developed both domestically and internationally as clean energy that does not emit greenhouse gases. In particular, offshore wind power has been studied because the wind resources are relatively limitless and the wind power is relatively smaller than onshore. In this study, to analyze the scour phenomenon around offshore wind foundations, mono pile and tripod pile foundations were simulated using a FLOW-3D model. The scour phenomenon was evaluated for mono piles: one is a pile with a 5 m diameter and d=1.69 m and the other is a pile with a 5 m diameter. Numerical analysis showed that in the latter, the falling-flow increased and the maximum scour depth occurred more than 1.7 times. For a tripod pile foundation, the measured velocity and the maximum wave condition were applied to the upstream boundary condition, respectively, and the scour phenomenon was evaluated. When the maximum wave condition was applied, the maximum scour depth occurred more than about 1.3 times. When the LES model was applied, the scour depth reached equilibrium, whereas the numerical results of the RNG model show that the scour phenomenon occurred in the entire boundary area and the scour depth did not reach equilibrium. To evaluate the scour phenomenon around offshore wind foundations, it is reasonable to apply the wave condition and the LES turbulence model to numerical model applications.

A Case Study of Pier Scour Considering Soil Erodibility (지반의 침식특성을 이용한 교각세굴 사례 연구)

  • 곽기석;정문경;이주형;박재현
    • Journal of the Korean Geotechnical Society
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    • v.20 no.3
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    • pp.67-74
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    • 2004
  • A case study was performed to verify the applicability of existing formulae for predicting bridge scour in cases where its piers are founded in fine-grained soils. The object of study was the Kanghwa Choji Bridge area where the streambed consists of mainly clayey soil. Site investigation included: direct measurement of scour depths around piers using an ultrasonic probe; and collection of undisturbed soil samples which were later used to determine geotechnical properties and scour rate under different stream velocities. Scour depth prediction was made by employing several conventional methods and compared with the measured value. All methods, not taking soil's intrinsic property against erosion into consideration, overestimated scour depth by a factor of 3.6 to 6.5. On the other hand, the SRICOS method yielded a reasonably acceptable overestimation by a factor of 1.7.

Bridge Scour Prioritization and Management System (I) - System Development - (교량세굴 위험도 결정 및 유지관리 시스템 개발(I) - 시스템 개발 -)

  • Kwak, Kiseok;Park, Jae Hyun;Chung, Moon Kyung;Woo, Hyo Seop
    • 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.