Clear-water local scour at wide piers in shallow-water flow

Laboratory data for local scour depth regarding the size of wide piers are presented. Clear water scour tests were performed for various pier widths (0.06, 0.076, 0.102, 0.14 and 0.165 m), two types of pier shapes (circular and rectangular) and two types of uniform cohesionless bed sediment (d50 = 0.23 and d50 = 0.80 mm). New data are presented and used to demonstrate the effects of pier width, pier shape and sediment size on scour depth. The influence of equilibrium time (te) on scouring processes is also discussed. Equilibrium scour depths were found to decrease with increasing values of b/d50. The temporal development of equilibrium local scour depth with new laboratory data is demonstrated for flow intensity V/Vc = 0.95. On the other hand, the results of scour mechanism have shown a significant relationship between normalized volume of scoured and deposited with pier width, b. The experimental data obtained in this study and data available from the literature for wide piers are used to evaluate predictions of existing methods.

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Nose-Angle Bridge Piers as Alternative Countermeasures for Local Scour Reduction

The Baltic Journal of Road and Bridge Engineering ◽

10.7250/bjrbe.2018-13.405 ◽

2018 ◽

Vol 13 (2) ◽

pp. 110-120 ◽

Cited By ~ 2

Author(s):

Ibtesam Abudallah Habib ◽

Wan Hanna Melini Wan Mohtar ◽

Atef Elsaiad ◽

Ahmed El-Shafie

Keyword(s):

Froude Number ◽

Local Scour ◽

Bridge Piers ◽

Scour Depth ◽

Skew Angle ◽

Flow Angle ◽

Sediment Size ◽

Low Froude Number ◽

Skew Angles ◽

Depth Reduction

This study investigates the performance nose-angle piers as countermeasures for local scour reduction around piers. Four nose angles were studied, i.e., 90°, 70°, 60° and 45° and tested in a laboratory. The sediment size was fixed at 0.39 mm whereas the flow angle of attack (or skew angle) was varied at four angles, i.e., skew angles, i.e., 0°, 10°, 20° and 30°. Scour reduction was clear when decreasing nose angles and reached maximum when the nose angle is 45°. Increasing the flow velocity and skew angle was subsequently increasing the scour profile, both in vertical and transversal directions. However, the efficiency of nose angle piers was only high at low Froude number less than 0.40 where higher Froude number gives minimal changes in the maximum scour depth reduction. At a higher skew angle, although showed promising maximum scour depth reduction, the increasing pier projected width resulted in the increase of transversal lengths.

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Abutment scour in clear-water and live-bed conditions by GMDH network

Water Science & Technology ◽

10.2166/wst.2013.670 ◽

2013 ◽

Vol 67 (5) ◽

pp. 1121-1128 ◽

Cited By ~ 32

Author(s):

Mohammad Najafzadeh ◽

Gholam-Abbas Barani ◽

Masoud Reza Hessami Kermani

Keyword(s):

Back Propagation ◽

Support Vector ◽

Group Method ◽

Scour Depth ◽

Back Propagation Algorithm ◽

Clear Water ◽

Sediment Size ◽

Svm Model ◽

Vector Machines ◽

Abutment Scour

In the present study, the Group Method of Data Handling (GMDH) network has been utilized to predict abutments scour depth for both clear-water and live-bed conditions. The GMDH network was developed using a Back Propagation algorithm (BP). Input parameters that were considered as effective variables on abutment scour depth included properties of sediment size, geometry of bridge abutments, and properties of approaching flow. Training and testing performances of the GMDH network were carried out using dimensionless parameters that were collected from the literature. The testing results were compared with those obtained using the Support Vector Machines (SVM) model and the traditional equations. The GMDH network predicted the abutment scour depth with lower error (RMSE (root mean square error) = 0.29 and MAPE (mean absolute percentage of error) = 0.99) and higher (R = 0.98) accuracy than those performed using the SVM model and the traditional equations.

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Clear-water scour at bridge piers in fine and medium gravel beds

Canadian Journal of Civil Engineering ◽

10.1139/l05-022 ◽

2005 ◽

Vol 32 (4) ◽

pp. 775-781 ◽

Cited By ~ 14

Author(s):

Rajkumar V Raikar ◽

Subhasish Dey

Keyword(s):

Bridge Piers ◽

Geometric Standard Deviation ◽

Scour Depth ◽

Size Factor ◽

Clear Water ◽

Envelope Curve ◽

Gravel Beds ◽

Sediment Size ◽

Gravel Size ◽

Equilibrium Scour Depth

An experimental investigation on scour at circular and square piers in uniform and non-uniform gravels (fine and medium sizes) under clear-water scour at limiting stability of gravels is presented. From the experimental results, it is observed that the equilibrium scour depth increases with decrease in gravel size. The variation of equilibrium scour depth with gravel sizes departures considerably from that with sand sizes. Consequently, the resulting sediment size factors for gravels, obtained from envelope curve fitting, are significantly different from the existing sediment size factor for sands. The influence of gravel gradation on scour depth is also prominent in non-uniform gravels. The time scales to represent the time variation of scour depth in uniform and non-uniform gravels are determined. For uniform gravels, the non-dimensional time scale increases with increase in pier Froude number and gravel size, whereas for non-uniform gravels, it decreases with increase in geometric standard deviation of particle size distribution of gravels.Key words: bridge pier, gravel beds, scour, erosion, sediment transport, open channel flow, hydraulic engineering.

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Investigation of Local Scour around L-Shape Submerged Groynes in Clearwater Conditions

Tikrit Journal of Engineering Sciences ◽

10.25130/tjes.28.3.12 ◽

2021 ◽

Vol 28 (3) ◽

pp. 159-169

Author(s):

Saleh Issa Khassaf ◽

Budoor Mohammed Rashak

Keyword(s):

Froude Number ◽

Local Scour ◽

Scour Depth ◽

Contour Lines ◽

Low Profile ◽

Scour Hole ◽

Number Flow ◽

Flow Intensity ◽

Good Determination ◽

New Formula

Submerged Groynes are low profile linear structures that are generally located on the outside bank to form Groynes fields and prevent the erosion of stream banks by redirecting high-velocity flow away from the bank. This research was studied in detail through two major stages. The first stage of the study is based on laboratory experiments to measure the development of local scour around L-shape submerged Groyne with the time, and special attention is given to the effects of different hydraulic and geometric parameters on local scour. Also; maps were drawn showing contour lines that represented the bed levels for maximum scour depth after reaching the equilibrium case. The result showed that a decrease in the scour depth ratio due to the increasing submerged ratio, and the number of Groynes. While the scour hole geometry will increase with the Froude number, flow intensity, and the spacing between Groynes, the decreasing percentage in the scour hole was measured to be about (4.3) % and (4.4) % for decreasing the spacing between Groynes from (2Lg) to (1.5Lg). Besides, it was range about (11.1) % and (14.0) % when reducing the spacing from (1.5Lg) to (Lg) under the same value of maximum Froude number. The second stage of the study is based on experimental results. A new formula was developed by using statistical analysis and it was found that a good determination coefficient.

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Effect of Reynolds Number on Local Scour Around a Monopile in Steady Current

Volume 7A: Ocean Engineering ◽

10.1115/omae2019-96735 ◽

2019 ◽

Author(s):

Xiaofan Lou ◽

Kaibing Zhang ◽

Zhenhong Chen

Keyword(s):

Reynolds Number ◽

Time Scale ◽

Time History ◽

Local Scour ◽

Circular Cylinders ◽

Scour Depth ◽

Clear Water ◽

Number Range ◽

Steady Current ◽

Equilibrium Scour Depth

Abstract The effect of Reynolds number (Re) on the local scour around a monopile encountering steady current was investigated experimentally in a water flume. The experiment was performed using circular cylinders with different diameters under two different freestream velocities, covering both clear-water and live-bed scours and a Reynolds number range of approximately 9,000–60,000. The time-series of the scour depth was recorded during the whole scour process and the scour pit was scanned after the scour process reached equilibrium. Results are presented in terms of the equilibrium scour depth, the time-scale of the scour process and the three-dimensional scour profile at different Reynolds numbers. For both clear-water and live-bed scours, the time history of the scour process indicate that the time-scale becomes larger as Re increases. It is also found that the normalized equilibrium scour depth, as well as the normalized scour radius, decrease with the increasing Re. An empirical equation of the equilibrium scour depth is derived as a function of Reynolds number based on the experimental results so as to better account for Re effect in the scour design.

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Physical Modeling of Spatial and Temporal Development of Local Scour at the Downstream of Bed Protection for Low Froude Number

Water ◽

10.3390/w11051041 ◽

2019 ◽

Vol 11 (5) ◽

pp. 1041 ◽

Cited By ~ 1

Author(s):

Sung Won Park ◽

Jin Hwan Hwang ◽

Jungkyu Ahn

Keyword(s):

Equilibrium State ◽

Froude Number ◽

Fixed Bed ◽

Local Scour ◽

Dominant Factor ◽

Scour Depth ◽

Dimensionless Time ◽

Temporal Development ◽

Low Froude Number ◽

Bed Protection

Local scour at the downstream of the river bed protection is one of the most important parameters for the design criteria and sustainable management of the hydraulic structures. Previously, various researches on its process in the equilibrium state have been suggested with experimental and numerical approaches. In this study, relatively long-term laboratory experiments of local scouring at the downstream of fixed bed in an open channel were conducted with mono-granular sediment bed and analyzed about maximum scour depth and its temporal development. In particular, we conducted experiments with relatively low Froude number (less than 0.5) and their duration of tests was exceeded over 700 hours. We modified the relationship between the dimensionless time and length scales of the maximum scour depth of the local scour hole based on the turbulent shear layer thickness. A new functional relationship between dominant factors and the maximum scour depth in the equilibrium state were suggested and compared with previously suggested formula. Also, from the results by nonlinear regression, Froude number was founded as a dominant factor on the prediction of equilibrium maximum scour depth.

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Local Scour for Vertical Piles in Steady Currents: Review of Mechanisms, Influencing Factors and Empirical Equations

Journal of Marine Science and Engineering ◽

10.3390/jmse8010004 ◽

2019 ◽

Vol 8 (1) ◽

pp. 4 ◽

Cited By ~ 6

Author(s):

Bingchen Liang ◽

Shengtao Du ◽

Xinying Pan ◽

Libang Zhang

Keyword(s):

Influencing Factors ◽

Local Scour ◽

Future Research ◽

Scour Depth ◽

Empirical Equations ◽

Research Directions ◽

Fundamental Knowledge ◽

Future Research Directions ◽

Flow Intensity ◽

Bridge Failure

Scour induced by currents is one of the main causes of the bridge failure in rivers. Fundamental knowledge and mechanisms on scour processes due to currents are often taken as a basis for scour studies, which are the focus of this review. Scour development induced by waves and in combined wave–current conditions are also briefly discussed. For the design of structure foundations, the maximum scour depths need to be estimated. The mechanisms of local scour and predictions of maximum local scour depths have been studied extensively for many years. Despite the complexity of the scour process, a lot of satisfying results and progresses have been achieved by many investigators. In order to get a comprehensive review of local scour for vertical piles, major progresses made by researchers are summarized in this review. In particular, maximum scour depth influencing factors including flow intensity, sediments, pile parameters and time are analyzed with experimental data. A few empirical equations referring to temporary scour depth and maximum scour depth were classified with their expressing forms. Finally, conclusions and future research directions are addressed.

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Recognizing of the best different artificial intelligence method for determination of local scour depth around group piers in equilibrium time

Arabian Journal of Geosciences ◽

10.1007/s12517-020-05738-4 ◽

2020 ◽

Vol 13 (19) ◽

Author(s):

Arash Adib ◽

Syed Hossein Tabatabaee ◽

Abdolgafour Khademalrasoul ◽

Mohammad Mahmoudian Shoushtari

Keyword(s):

Artificial Intelligence ◽

Local Scour ◽

Scour Depth ◽

Equilibrium Time

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Study of the time-dependent clear water scour around circular bridge piers

Journal of Hydrology and Hydromechanics ◽

10.1515/johh-2016-0048 ◽

2017 ◽

Vol 65 (1) ◽

pp. 26-34 ◽

Cited By ~ 7

Author(s):

Aysegul Ozgenc Aksoy ◽

Gokcen Bombar ◽

Tanıl Arkis ◽

Mehmet Sukru Guney

Keyword(s):

Empirical Relation ◽

Local Scour ◽

Bridge Piers ◽

Geometric Standard Deviation ◽

Dimensionless Time ◽

Clear Water ◽

Relative Water ◽

Median Diameter ◽

Flow Intensity ◽

Experimental Findings

Abstract The local scour around bridge piers influences their stabilities and plays a key role in the bridge failures. The estimation of the maximum possible scour depth around bridge piers is an important step in the design of the bridge pier foundations. In this study, the temporal evolution of local scour depths as well as the equilibrium scour depths were analyzed. The experiments were carried out in a rectangular flume by using uniform sediment with median diameter of 3.5 mm and geometric standard deviation of 1.4. The diameters of the tested circular bridge piers were 40 mm, 80 mm, 150 mm and 200 mm. The flow and scour depths were determined by ultrasonic sensors. The experiments were realized in clear water conditions with various constant flow rates. The experimental findings were compared with those calculated from some empirical equations existing in the literature. A new empirical relation involving the flow intensity, the relative water depth and the dimensionless time is also introduced. The advantage of this proposed relation is that the only parameter requiring the calculation is the critical velocity, other parameters being known geometric and hydraulic parameters. The performance of this relation was tested by using experimental data available in the literature, and a satisfactory compatibility was revealed between the experimental and numerical results.

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