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1
Rasool, Huda, and Thamer A. Mohammed. "Checking the Accuracy of Selected Formulae for both Clear Water and Live Bed Bridge Scour." Journal of Engineering 29, no. 2 (February 1, 2023): 99–111. http://dx.doi.org/10.31026/j.eng.2023.02.07.
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Due to severe scouring, many bridges failed worldwide. Therefore, the safety of the existing bridge (after contrition) mainly depends on the continuous monitoring of local scour at the substructure. However, the bridge's safety before construction mainly depends on the consideration of local scour estimation at the bridge substructure. Estimating the local scour at the bridge piers is usually done using the available formulae. Almost all the formulae used in estimating local scour at the bridge piers were derived from laboratory data. It is essential to test the performance of proposed local scour formulae using field data. In this study, the performance of selected bridge scours estimation formulae was validated and statistically tested using field data for existing bridges in Canada, Iraq (Kufa, Najaf), Pakistan, Bangladesh, and India. The validated formulae were HEC-18, Forehlich, and Johnson. The validation was conducted by comparing the predicted local scour depths obtained from applying the above selected formulae with the local scour depths obtained from the field data. The comparison between them was presented using a scattergram. However, statistical tests were used to present the accuracy of the local scour predictions. The tests were conducted using three statistical indices, namely, Theil’s coefficient (U), Mean Absolute Error (MAE), and Root Mean Square Error (RMSE). Among the tested formulae, the Jonson formula gave satisfactory performance since the values of U, MAE, and RMSE were found to be 0.112, 1.351, and 1.650, respectively.
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Vuong, Thi-Hong-Nhi, Tso-Ren Wu, Yi-Xuan Huang, and Tai-Wen Hsu. "Numerical Analysis of Local Scour of the Offshore Wind Turbines in Taiwan." Journal of Marine Science and Engineering 11, no. 5 (April 27, 2023): 936. http://dx.doi.org/10.3390/jmse11050936.
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Rapid expansions of the offshore wind industry have stimulated a renewed interest in the behavior of offshore wind turbines. Monopile, tripod, and jack-up wind turbines support most offshore wind turbines. These foundations are sensitive to scour, reducing their ultimate capacity and altering their dynamic response. However, the existing approaches ignore the seabed’s rheological properties in the scour process. This study focuses on the scour development around the wind turbine foundation in the Changhua wind farm in Taiwan. The simulation results explain the influence of different hydrodynamic mechanisms on the local scours in a cohesive fluid, such as regular waves, random waves, and constant currents. A newly non-Newtonian fluid model, the Discontinuous Bi-viscous Model (DBM), reproduces closet mud material nature without many empirical coefficients and an empirical formula. This new rheology model is integrated and coupled into the Splash3D model, which resolves the Navier–Stokes equations with a PLIC-VOF surface-tracking algorithm. The deformation of the scour hole, the backfilling, and the maximum scour depth are exhibited around the wind turbines. Waves, including regular and irregular waves, do not increase the scour depth compared with currents only. In the case of random wave–current coupling, the results present a signal of scour evolution. However, the scour depth is shallow at 0.033≤S/D≤0.046.
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Mondal, M. Shahjahan. "Local Scour at Complex Bridge Piers in Bangladesh Rivers: Reflections from a Large Study." Water 14, no. 15 (August 3, 2022): 2405. http://dx.doi.org/10.3390/w14152405.
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Many small-scale experimental, field, and empirical studies on bridge scour are available, however a large-scale study on local scour at a complex pier with wide variation in design parameters is still lacking. In this study, a country-wide assessment of local scour at complex piers of 239 bridges in Bangladesh is made. The hydrologic, hydraulic, and sediment data required in the assessment are obtained from secondary sources, primary measurements and samples, and numerical model simulations. An incredible number of 239 field visits are made, 1434 km of bathymetric surveys are carried out, and 478 samples of bed soils are collected and analyzed. The local scour depth is estimated using a complex pier configuration with pier, pile, and pile cap dimensions selected in consultation with structural and geotechnical engineers of bridge design. Flood frequency analysis and the HEC-RAS model simulation are used to estimate the hydrologic and hydrodynamic parameters needed in the assessment. A number of empirical formulations are used to estimate and compare the design local scours. The formulae of Melville and Coleman, Jain and Fischer, and Richardson are found to be dominant when deciding the design local scour depth at the bridge piers. Suggestions are provided to include a few additional equations in scour estimation and to develop a unified Bangladesh standard for scour depth estimation. The findings and recommendations of the study would be useful in planning and designing bridges in alluvial deltaic settings, particularly in the selection of empirical methods and mainstreaming of complex pier configuration in bridge scour assessment.
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Chavan, Vidya Subhash, Shen-En Chen, Navanit Sri Shanmugam, Wenwu Tang, John Diemer, Craig Allan, Nicole Braxtan, Tarini Shukla, Tianyang Chen, and Zachery Slocum. "An Analysis of Local and Combined (Global) Scours on Piers-on-Bank Bridges." CivilEng 3, no. 1 (December 21, 2021): 1–20. http://dx.doi.org/10.3390/civileng3010001.
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This paper examines the scour problems related to piers-on-bank bridges resulting from frequently flooded and/or constricted waterways. While local scour problems for bridge piers in riverine channels have been addressed extensively in the literature, there have been few studies addressing piers-on-bank scour scenarios. A comprehensive three-dimensional finite element analysis using the element removal (ER) technique has been performed on a recently constructed bridge with an observable scour problem on multiple piers. The analysis is further extended to study the effect of “combined scour” or extensive erosion of soil between adjacent piles. Three different loading cases were considered in the study, and the results demonstrated that the effects of local and combined scours on bridge drilled shaft foundations can be significant under the combined actions of axial, lateral loads and bending moments. Specifically, the most critical case of combined scour is when maximum moment effect is applied to the piers. The results of this study show that the interaction of soil displacement fields between adjacent piles should be investigated for bridge crossings with piers-on-bank, with a high risk of flooding during the moderate-to-low probability of the occurrence of precipitation events, as they can increase the pile head displacements and the bending moments in the soil and result in the early failure of bridges.
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Tariq, Moiz, Azam Khan, and Mujahid Khan. "Experimental Study of Scour Hole Depth around Bridge Pile Using Efficient Cross-Section." Applied Sciences 12, no. 10 (May 20, 2022): 5205. http://dx.doi.org/10.3390/app12105205.
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Extensive numerical and analytical studies exist that focus on the scours around bridge piers with different cross-sections. However, studies addressing the scour around bridge piles are rather limited and not conclusive. Therefore, the most efficient cross-section reducing the local scour around a pile group is experimentally examined herein. Accordingly, comparative scouring of three different shapes, namely, circular, rectangular and lenticular, is investigated by installing a cohesion-less bedding material around scaled bridge piles immersed in clear water. It is also shown that the available pier scour predictive models grossly underestimate the depth of pile scour holes. For example, the pier predictive models underestimate the pile scours hole by more than 50% in the case of square and circular cross-sections. It also transpires from the experimental investigation that the scour hole depth around the square shape pile is significant, around the circular pile is moderate and around the lenticular pile is minimal.
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Xie, Liquan, Yehui Zhu, Huang Li, Yan-hong Li, Yuanping Yang, and Tsung-chow Su. "Local Scour Near Flexible Flow Deflectors." Water 12, no. 1 (January 4, 2020): 153. http://dx.doi.org/10.3390/w12010153.
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Rigid flow deflectors are usually used on water flow beds to protect engineering structures such as breakwater in coasts and to regulate flow routes in open channels. To reduce its side-effects, i.e., local scour at the toe of deflectors, a flexible flow deflector is proposed, and the corresponding local scour was investigated in this study. A flume experiment was conducted to investigate local scour. To show the advantage of flexible deflectors, a control experimental test was also conducted using a traditional rigid deflector under the same blockage area configuration and the same flow conditions. The flow field near the flexible deflector was also measured to reveal the local flow field. The results show that the bed-scour develops near the toe edges of both flexible and rigid deflectors, but the maximum and averaged scour depths for the flexible deflector are smaller. This advantage of flexible deflector in scour depth is mainly caused by its prone posture, which induces the upward stretching and enlarging horizontally rotating vortex and the upward shifted vertically rotating vortex. The former dissipates more turbulent energy and the latter results in smaller bed shear stress, which lead to smaller scour depth directly. In addition, the up- and down-swaying movement of the flexible deflector can also assistant to dissipate more turbulent energy, thereby damping the intense of the horseshoe vortices and thus weakening scour depth as well. The results of this study provide an elementary understanding on the mechanisms of a flexible flow structure and an alternative deflector-device to reduce scour depth.
7
Enomoto, Yota, Katsuya Hamachi, and Taro Arikawa. "SCALE EFFECT IN LOCAL SCOUR AROUND AN OFFSHORE PILE." Coastal Engineering Proceedings, no. 37 (September 1, 2023): 88. http://dx.doi.org/10.9753/icce.v37.structures.88.
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Accurately predicting scour is important for its prevention around the foundations of offshore wind turbines. Many studies on local scour around piles have been conducted. Chen et al. (2022) conducted scour analysis using largescale experiments and examined the maximum scour depth. However, the relationship between scour depth and time has not yet been investigated. Furthermore, only a few studies have comprehensively examined the scale effects and similarity laws. In this study, experiments for analyzing local scour around a pile were conducted at different scales, 1/13, 1/65, and 1/130, to verify the scale effects and corresponding similarity laws regarding scouring time.
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Sang, Liansheng, Jun Wang, Tiejie Cheng, Zhixing Hou, and Jueyi Sui. "Local Scour around Tandem Double Piers under an Ice Cover." Water 14, no. 7 (April 6, 2022): 1168. http://dx.doi.org/10.3390/w14071168.
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Compared to the scour around a single pier, the local scour process around tandem double piers is much more complicated. Based on laboratory experiments in a flume, we conducted the scour process around tandem double piers under an ice-covered flow condition. The results showed that when the pier spacing ratio L/D = 2 (where L = the pier spacing distance, and D = the pier diameter), the rear pier (the downstream one) will intensify the horseshoe vortex process behind the front pier, and the scour depth around the front pier will increase by about 10%. As the pier spacing ratio L/D increases, the scour depth around the front pier will gradually decrease. When the pier spacing ratio L/D = 5, sediment scoured around the front pier begins to deposit between these two piers. To initiate a deposition dune between piers, the pier spacing distance under an ice-covered condition is about 20% more than that under an open flow condition. The results also showed that the existence of the rear pier will lead to an increase in the length of the scour hole but a decrease in the depth of the scour hole around the front pier. The local scour around the front pier interacts with the local scour of the rear pier. The maximum scour depth of the scour hole around the rear pier increases first, then decreases and increases again afterward. When the pier spacing ratio L/D = 9, the scour depth around the rear pier is the least. With an increase in the pier spacing ratio, the influence of the local scour around the front pier on the local scour around the rear pier gradually decreases. When the pier spacing ratio L/D is more than 17, the scour around the front pier has hardly any influence on that around the rear pier. The scour depth around the rear pier is about 90% of that around the front pier.
9
McGovern, David J., Suzana Ilic, Andrew M. Folkard, Stuart J. McLelland, and Brendan J. Murphy. "EVOLUTION OF LOCAL SCOUR AROUND A COLLARED MONOPILE THROUGH TIDAL CYCLES." Coastal Engineering Proceedings 1, no. 33 (December 15, 2012): 113. http://dx.doi.org/10.9753/icce.v33.sediment.113.
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This paper presents the results of an experiment designed to assess the time-development of scour around an offshore wind turbine collared monopile over a number of tidal cycles. One collar shape and location was investigated. The scour developed more slowly and the scour depth was shallower than for the case of a smooth monopile throughout the majority of the first half-cycle. This difference reduced quite rapidly during the second half-cycle and the scour depth at the end of two tidal cycles was essentially the same as for the smooth monopile. The time development of the scour was compared with results from existing empirical models for the time-development of scour under unidirectional flow. As expected, these models give a much smoother evolution of scour and different scour rates than those measured. Time variation in scour depth was better reproduced with a simplified approach for prediction of the time-varying development of scour. This also highlighted a problem with estimation of the time scale for the development of the equilibrium scour depth. Further investigations are needed before this alternative scour protection is completely rejected.
10
Mohamed, M. S., and J. A. Mccorquodale. "Short-term local scour." Journal of Hydraulic Research 30, no. 5 (September 1992): 685–99. http://dx.doi.org/10.1080/00221689209498888.
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Qi, Hongliang, Tiangang Yuan, Wen Zou, Weiping Tian, and Jiachun Li. "Numerical Study on Local Scour Reduction around Two Cylindrical Piers Arranged in Tandem Using Collars." Water 15, no. 23 (November 24, 2023): 4079. http://dx.doi.org/10.3390/w15234079.
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Local scour occurring near bridge piers has become a major problem all over the world, which has caused countless bridge damage events. Explorations regarding local scour reduction measurements have become a research hotspot in the field. Much effective research has been conducted on scour reduction for single piers. However, studies on local scour reduction around multiple piers that are arranged in tandem have rarely been reported. Therefore, the effect of the span and the local scour reduction measurement (collar) on the characteristics of the local scouring behavior around two piers arranged in tandem are explored in this research, with numerical simulations in clear-water conditions. The results show that the local scour depth of the downstream pier increases gradually with an increase in the pier spacing, due to the weakened sheltering effect of the upstream pier. The local scouring of both the upstream and downstream piers can be reduced if the upstream pier is protected by a collar. The local scour reduction efficiency of the upstream pier can reach 52~55%. The local scour reduction efficiency of the downstream pier decreases rapidly from 84.3% to 8.3% with an increase in the pier spacing. If the pier spacing, G, is greater than 4.0D (D is the diameter of the pier), the local scour depth around the downstream pier is larger than that around the upstream pier. Therefore, if the local scour depth of the upstream pier is considered safe and acceptable, it is used as the reduction target of the downstream local scour depth. A collar must be adapted for use around the downstream pier when G/D > 4.0. If both the piers are protected by collars of the same size (W = 3.0D), the local scour reduction efficiency of the downstream pier is about 15% more than that of the upstream pier. The local scour depth around the downstream pier is 64.5% of that around the upstream pier. Therefore, the size of the collar around the downstream pier can be decreased to save costs. The local scour reduction efficiency for the downstream pier reduces from 66.7% to 39.8% when the downstream collar size (W) decreases from 3.0D to 2.0D. To ensure that the local scour depth around the downstream pier is no greater than that of the upstream pier, the downstream collar should be larger than 2.25D. These results can serve as a reference for the local scour reduction of two piers arranged in tandem.
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Hassan, Zahraa F., Ibtisam R. Karim, and Abdul-Hassan K. Al-Shukur. "Effect of Interaction between Bridge Piers on Local Scouring in Cohesive Soils." Civil Engineering Journal 6, no. 4 (April 1, 2020): 659–69. http://dx.doi.org/10.28991/cej-2020-03091498.
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Local scour at the piers is one of the main reasons of bridge foundation undermining. Earlier research studies focused mainly on the scour at a single bridge pier; nevertheless, modern designs of the bridges comprise wide-span and thus group of piers rather than a single pier are usually used to support the superstructure. The flow and scour pattern around group of piers is different from the case of a single pier due to the interaction effect. Reviewing the literature of local scour around bridge piers group revealed that the local scour around bridge piers group founded in cohesive soil bed was not investigated, and most of the scour studies were related to scour in cohesionless soils. The objective of the present study is to investigate the effect of the interaction between two in-line (tandem) circular bridge piers of variable spacings founded in cohesive soil on the local scour. A set of laboratory flume experiments were conducted under the clear-water scour condition to investigate this effect. This study is the first that investigates experimentally the scour around group of bridge piers in cohesive bed. It was found that the maximum scour depth at the upstream pier of the two in-line piers occurred at a spacing of two times the diameter of the pier, scour at the downstream pier was reduced due to a sheltering effect, the interference effect will be reduced for pier spacings larger than three times of the pier diameter. A recent pier scour equation was used to estimate the scour depths at the two in-line piers in cohesive soil and compare the estimated value with the measured scour depths in the laboratory. The comparison indicated that the proposed scour equation overestimates the scour depths at both the upstream and the downstream pier.
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Khassaf, Saleh I., and Mohammed Ridha Sadeq. "Experimental Study of Local Scour around Circular pier Fitted with Collar." Kufa Journal of Engineering 3, no. 2 (May 26, 2014): 87–100. http://dx.doi.org/10.30572/2018/kje/321259.
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Scour is defined as the erosion of streambed sediment around an obstruction in a flow field. Bridge pier scouring is a significant problem in the safety estimation of bridges. In this study, the use of rectangular collar for reducing the effect of local scour at a circular pier in a laboratory flume was presented. The study was conducted using 6.6 m laboratory flume in length and 0.4 m in width. Experiments were conducted for various sizes of rectangular collars fitted at the bed elevation on the scour depth at the circular pier with clear-water scour condition. The time development of scour depth at the circular pier with and without a collar of circular installed was conducted. In collars observed that size of a collar plate increases, the scour decreases. Results showed that the maximum reduction in scour depth equal to 100% (no scour hole). Dimensional analysis technique was used, and from the experimental data an empirical formula was derived. It was found that the predicated scour depth from the formula performs well as compared to the observed scour depth.
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Hafez, Youssef I. "Mathematical Modeling of Local Scour at Slender and Wide Bridge Piers." Journal of Fluids 2016 (June 14, 2016): 1–19. http://dx.doi.org/10.1155/2016/4835253.
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Most existing equations for predicting local scour at bridge piers suffer from overprediction of the scour depths which results in higher foundation costs. To tackle this problem, a mathematical model for predicting bridge pier scour is developed herein based on an energy balance theory. The present study equation was compared to commonly used bridge scour equations using scour field data in USA. The developed equation has several advantages among which we have the following: it adds to the understanding of the physics of bridge pier scour, is valid for slender and wide piers, does not suffer from overprediction of scour depths, addresses clear water and live bed scour, and includes the effects of various characteristics of the bed material such as specific gravity (or density), porosity, size, and angle of repose. In addition, the developed equation accounts for the debris effect and aids in the design of scour mitigation methods such as collars, side bars, slots, and pier protective piles.
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Oh, Hyun Sik, and Ho Jin Lee. "Characteristics of Local Scour Around the Double Pile in Waves." Journal of Korean Society of Coastal and Ocean Engineers 34, no. 5 (October 31, 2022): 169–75. http://dx.doi.org/10.9765/kscoe.2022.34.5.169.
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Scour in a flow field affected by waves, such as river estuaries or shallow waters, is more difficult to predict than scour in a currents. The main issue in predicting the scour around circular files, such as undersea bridges, is the maximum scour depth and the point of occurrence. In the case of two or more adjacent circular piles, the location and depth of maximum scour according to the spacing between piles and the arrangement method show a lot of difference compared to the case of a single pile. In this paper, the KC number are calculated as dimensionless variables representing the strength of the flow. And the correlation between pile gap size and relative scour depth was analyzed.
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Wang, Shunyi, Kai Wei, Zhonghui Shen, and Qiqi Xiang. "Experimental Investigation of Local Scour Protection for Cylindrical Bridge Piers Using Anti-Scour Collars." Water 11, no. 7 (July 21, 2019): 1515. http://dx.doi.org/10.3390/w11071515.
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Local scour of bridge piers is one of the main threats responsible for bridge damage. Adopting scour countermeasures to protect bridge foundations from scour has become an important issue for the design and maintenance of bridges located in erodible sediment beds. This paper focuses on the protective effect of one active countermeasure named an “anti-scour collar” on local scour around the commonly used cylindrical bridge pier. A cylindrical pier model was set up in a current flume. River sand with a median particle size of 0.324 mm was selected and used as the sediment in the basin. A live-bed scour experimental program was carried out to study the protective effect of an anti-scour collar by comparing the local scour at a cylindrical bridge pier model with and without collar. The effects of three design parameters including collar installation height, collar external diameter and collar protection range, on the scour depth and scour development were investigated parametrically. According to the experimental results, it can be concluded that: the application of an anti-scour collar alleviates the local scour at the pier effectively; and the protection effect decreases with an increase in the collar installation height, but increases with an increase in the collar external diameter and the protection range. Design suggestions for improving the scour protective effect of the anti-scour collar are summarized and of great practical guiding significance to the development of anti-scour collars for bridge piers.
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Liang, Bingchen, Shengtao Du, Xinying Pan, and Libang Zhang. "Local Scour for Vertical Piles in Steady Currents: Review of Mechanisms, Influencing Factors and Empirical Equations." Journal of Marine Science and Engineering 8, no. 1 (December 19, 2019): 4. http://dx.doi.org/10.3390/jmse8010004.
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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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Muhardiono, Iman. "STUDY OF PILLAR DIMENSION VARIATIONS MODELLING ON RIVER GEOMORPHOLOGY." Jurnal PenSil 12, no. 3 (September 29, 2023): 304–13. http://dx.doi.org/10.21009/jpensil.v12i3.32680.
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The behavior of river flow patterns on the condition of the pillar dimensions can affect the geomorphology conditions of the river, namely the unbalanced local scouring between sediment transport and sediment supply so that it will affect the strength of the pillar. This study aims to study the effect of pillar dimensions on scour depth and channel base changes in the pillar area. The method of observation was carried out by simulations using Nays2DH with the same parameters for each test of each dimension with discharge (Q) = 0.5 m3/s, sediment diameter (D50) = 0.35 mm, channel width (B) = 5 m, channel length (L) = 25 m, slope (i) = 0.005 and drainage time (t) = 7200 s. The simulation results show the basic scour pattern of the channel which has the smallest value, the diamond type pillar. Degradation - Basic channel agitation on diamond type pillars, showing a pattern that tends to be evenly distributed compared to semi rounded, rectangle, or octagonal types. Period (t) 7200 s downstream of the pillar, semi rounded type scours change <0.3 m, rectangle type scours changes <0.4 m, octagonal type scours changes <0.4 m, and diamond type scours changes <0.2 m. So the dimensions of the diamond type are more effective in reducing the depth of scour.
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Muhawenimana, Valentine, Nadine Foad, Pablo Ouro, and Catherine A. M. E. Wilson. "Local Scour Patterns around a Bridge Pier with Cable-Wrapping." Fluids 8, no. 1 (December 21, 2022): 3. http://dx.doi.org/10.3390/fluids8010003.
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The performance of cable flow-altering bed scour countermeasures was experimentally evaluated based on the scour reduction, bed morphology, and the effects on the flow field. An unprotected 40 mm diameter pier was compared to piers protected with spiral cables (2, 4, 6, 8 and 10 mm diameters) wrapped at a 15-degree angle for two-bed sediment sizes with median grain sizes of 0.86 and 1.83 mm, for a cylinder Reynolds number of 7120. The scour depth was reduced by the cables by up to 52 percent compared to the unprotected pier case, a reduction that increased with increasing cable diameter for both sediment beds. Scour depth and sediment deposition varied by sediment size, where the scour hole was up to 45 percent deeper for the finer sediment bed than that of the coarser bed. Velocity and turbulence statistics showed that cables attenuated the flow within the scour hole by diminishing the downflow and horseshoe vortex, whereas in the case of finer sediment, spatially averaged turbulent kinetic energy and Reynolds shear stresses were respectively up to 1.4 and 1.8 times higher for the unprotected pier than the protected pier, resulting in scour depth reduction. The presence of the cable also reduced the vortex shedding frequency in the pier wake as indicated by a Strouhal number of around 0.175. The results demonstrate the potential of cable threading as a flow-altering scour countermeasure to reduce bridge pier scour.
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Li, Qiang, Xinquan Wang, Kenneth Gavin, Shengxiang Jiang, Hongguo Diao, Mingyuan Wang, and Kangyu Wang. "Scour Effect on the Lateral Bearing Behaviour of Monopiles Considering Different Slenderness Ratios." Water 16, no. 2 (January 9, 2024): 226. http://dx.doi.org/10.3390/w16020226.
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Scour leads to the loss of soil around monopile foundations for offshore wind turbines, which affects their structural safety. In this paper, the effect of scour on the lateral behaviour of monopiles was extensively investigated using finite element analysis, and calibration and comparison were undertaken using centrifuge tests. Piles with three slenderness ratios, i.e., 3, 5 and 8, were studied by keeping the diameter constant and varying the embedment length. Three scour types (local narrow, local wide and global) and four scour depths (0.5D, 1D, 1.5D and 2D; D signifies the pile diameter) were considered in this investigation. The results indicate that the lateral resistance of the pile is the greatest in the case of local narrow scour, followed by that in the cases of local wide scour and global scour. When the scour depth is larger than 1D, the influence of the scour type on the pile lateral bearing behaviour is insignificant. The influence of the scour type and scour depth on the pile lateral bearing behaviour is broadly similar for piles with slenderness ratios of 3, 5 and 8. However, the piles featured with smaller embedment lengths show a larger decrease rate in their lateral capacity, which means the effect of scour should cause more concern on small slenderness ratio monopiles.
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Wang, Jun, Zhixing Hou, Hongjian Sun, Bihe Fang, Jueyi Sui, and Bryan Karney. "Local scour around a bridge pier under ice-jammed flow condition – an experimental study." Journal of Hydrology and Hydromechanics 69, no. 3 (August 10, 2021): 275–87. http://dx.doi.org/10.2478/johh-2021-0014.
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Abstract The appearance of an ice jam in a river crucially distorts local hydrodynamic conditions including water level, flow velocity, riverbed form and local scour processes. Laboratory experiments are used for the first time here to study ice-induced scour processes near a bridge pier. Results show that with an ice sheet cover the scour hole depth around a bridge is increased by about 10% compared to under equivalent open flow conditions. More dramatically, ice-jammed flows induce both greater scour depths and scour variability, with the maximum scour depth under an ice-jammed flow as much as 200% greater than under equivalent open flow conditions. Under an ice-jammed condition, both the maximum depth and length of scour holes around a bridge pier increase with the flow velocity while the maximum scour hole depth increases with ice-jam thickness. Also, quite naturally, the height of the resulting deposition dune downstream of a scour hole responds to flow velocity and ice jam thickness. Using the laboratory data under ice-jammed conditions, predictive relationships are derived between the flow’s Froude number and both the dimensionless maximum scour depth and the dimensionless maximum scour length.
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Lantz, Wyatt D., Brian M. Crookston, and Michele Palermo. "Evolution of local scour downstream of Type A PK weir in non-cohesive sediments." Journal of Hydrology and Hydromechanics 70, no. 1 (February 12, 2022): 103–13. http://dx.doi.org/10.2478/johh-2021-0035.
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Abstract A large-scale piano key weir laboratory study was conducted to investigate the evolution of the scour process occurring in the downstream basin for two non-cohesive granular bed materials, including the analysis of scour-hole geometry and patterns at equilibrium. It was observed that hydraulic conditions, particularly tailwater level, significantly affect the scour mechanisms and equilibrium morphology, eventually resulting in scour depths that exceeded the weir height. Unprecedented insights on the scour dynamics are also provided, along with tools to estimate the time evolution and maximum scour depth, its location in the streamwise direction, and the maximum scour length.
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Liu, Qin, Zhe Wang, Ning Zhang, Hongyu Zhao, Lei Liu, Kunpeng Huang, and Xuguang Chen. "Local Scour Mechanism of Offshore Wind Power Pile Foundation Based on CFD-DEM." Journal of Marine Science and Engineering 10, no. 11 (November 11, 2022): 1724. http://dx.doi.org/10.3390/jmse10111724.
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The local scour around offshore pile foundations often seriously affects the normal operation of offshore wind power. The most widely used numerical simulation method in the study of local scour is the Euler two-fluid model (TFM). However, the contact effect between sediment particles is neglected in this model. Thus, the momentum and energy transfer between sediment particles and the fluid is not realistically reflected, which limits its significance in revealing the mesoscopic mechanism of local scour. Therefore, the computational fluid dynamics-discrete element method (CFD-DEM) numerical model was applied in this study, which fully considers the contact between solid particles and momentum transfer between two phases. The model was first verified by experimental data of a local scour test under clear water scour. Then, the mechanism of local scour was further discussed from macro and micro perspectives. The results showed that CFD-DEM could be effectively used to study the local scour around a pile foundation. The local scour was comprehensively affected by flow velocity, gravity, fluid force, drag force, and interaction between particles, etc. Although the maximum average drag force happened in the area about 90° from the direction of incoming flow, the maximum scour depth always occurred at about 45°. Corresponding findings and conclusions can be used for future reference when designing and protecting the offshore wind power pile.
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Annad, Mohamed, and Abdelouahab Lefkir. "New Formula for Calculating Local Scour around Bridge Piers." Advanced Engineering Forum 45 (April 4, 2022): 57–64. http://dx.doi.org/10.4028/p-9xgtbb.
Full textAbstract:
Several researchers working on the axes of solid particle transport, river flow, as well as the vulnerability of structures built on rivers have focused their work on the phenomenon of local scour, where many scour formulas have been proposed. Most of these formulas have been developed using laboratory data, estimated from simplified scaled-down models. This led to uncertainties and considerable inaccuracies in the scour estimation, sometimes causing serious consequences for the stability of structures subject to scour. These formulas were rarely tested using field data, where, until recently, there was very little data to validate them. This study aims to propose a new local scour formula using multiple nonlinear regression (MNLR). The data used is in situ data from an extensive database. The new proposed formula includes different parameters of the three fields involved in the triggering and development of the local scour, namely; the bridge, the flow, and the suspended characteristic of the eroded particle. The results obtained in the training phase and the validation show relatively better performances of the new formula compared to the existing empirical formulas.
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Zhang, Li, Hao Wang, Xianqi Zhang, Bo Wang, and Jian Chen. "The 3-D Morphology Evolution of Spur Dike Scour under Clear-Water Scour Conditions." Water 10, no. 11 (November 5, 2018): 1583. http://dx.doi.org/10.3390/w10111583.
Full textAbstract:
By changing the alignment angle of spur dike, this study focused on the evolution of scour hole morphology in three alignments under clear-water scour conditions, including the 3-D structure of the scour hole, 2-D profile morphological evolution process and the evolution characteristics of the local bed shear stress. The results show that the plane area and volume of the scour hole both are power functions over time, which is similar to the evolution characteristics of scour depth. Local scour includes three stages: The initial stage, development stage and balance stage. The local bed shear stress presents successively: τb > τc, τb = τc and τb < τc. Based on this characteristic, the evolution mechanism between scour hole morphology and the local bed shear stress is further clarified. Furthermore, although the alignment of the spur dike significantly affects the longitudinal and vertical dimension erosion rates of the scour hole, the scour hole morphology is not only relatively constant but also has a specific proportion, and the evolution process is orderly in the whole process of evolution. To the scouring equilibrium state, the length of the scour hole on the upstream and downstream of the spur dike is approximately in line with the golden section feature. The related results provide technical support for scour parameter design and scour hole protection of spur dike in flood period.
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Shi, Li, Yongzhou Cheng, Yuwei Zheng, Bo Xia, and Xiaoyun Huang. "Experimental Study on Local Scour at the Monopile Foundation of an Offshore Wind Turbine under the Combined Action of Wave–Current–Vibration." Journal of Marine Science and Engineering 12, no. 6 (June 7, 2024): 963. http://dx.doi.org/10.3390/jmse12060963.
Full textAbstract:
Monopile foundations are the most widely used offshore wind turbine foundations. The experiments were conducted to investigate the influencing factors of local scour around the monopile under the action of wave–current–vibration. The study analyzed the characteristics of local scour, including the maximum scour depth, the development of scour hole shape, and the shape of the scour hole profile. The dimensionless influencing factors (vibration intensity, Froude number, Keulegan–Carpenter number, and combined wave–current parameter) are subsequently analyzed. An empirical formula is developed to predict the local scour depth of a monopile under the combined influence of wave–current–vibration. The formula provides a theoretical underpinning for engineering design.
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ZHOU, Daocheng, Bo ZHANG, and Dongsheng QIAO. "Analysis of the Effect of Local Foundation Scouring on the Structural Dynamic Effect of a Cable-Stayed Bridge Across The Sea." Engineering Materials and Structures 2, no. 1 (March 28, 2023): 1–14. http://dx.doi.org/10.48014/ems.20230114001.
Full textAbstract:
The foundation scour reduces the restraining effect of the foundation on the bridge foundation, resulting in the reduction of the lateral bearing capacity of the bridge foundation. For the cross-sea bridge, the dynamic effect of foundation scour on the bridge structure is more significant, thus affecting the safety of the structure. In this paper, the maximum possible local scouring depth of the foundation is first calculated to make the simulated foundation scouring condition conform. to the actual project. Then, the m-method is adopted to calculate the stiffness value of the foundation soil spring and establish an elastic restraint model that reflects the restraint of the foundation soil on the bridge foundation, thus setting up the finite element model of the bridge with regard to the foundation scouring. On this basis, taking Qiongzhou Strait cross-sea highway and railway dual-purpose cable-stayed bridge as an example, the effect of foundation scour on the dynamic effect of cross-sea cable-stayed bridges under the action of wind and waves is analyzed, and the influence law of the local scour depth of the foundation on the dynamic effect of the structure is determined. The maximum scour depth of 12m is considered to increase the displacement of the top of the tower by 14. 65%, mainly because the foundation scours reduces the restraint effect of the foundation soil on the bridge foundation, resulting in the reduction of the lateral bearing capacity of the bridge foundation. Therefore, for the cross-sea cable-stayed bridge without foundation soil treatment, the detection and monitoring of foundation scour should be strengthened or the preventive maintenance and reinforcement treatment of foundation soil should be done in advance to ensure the safe operation of the bridge structure.
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Crowley, Raphael, William Cottrell, and Alexander Singleton. "An Examination of the Dependency between Maximum Equilibrium Local Scour Depth and the Grain Size/Structure Size Ratio." Water 12, no. 11 (November 6, 2020): 3117. http://dx.doi.org/10.3390/w12113117.
Full textAbstract:
This paper begins by demonstrating how the Florida Department of Transportation (FDOT) local scour equations take the ratio between grain size and structure size into account when computing equilibrium local scour depth and contrasts this with the well-known Colorado State University (CSU) equation that does not take sediment information into account. Then, a relatively recent empirical formulation from the J-L. Briaud research group for computing local equilibrium scour depth is presented that appears to take the structure size/grain size ratio into account indirectly. Next, a possible explanation for the dependency between local equilibrium scour depth and the structure/grain size ratio is presented that was originally developed by D. Max Sheppard in 2004. This explanation shows that superimposing the pressure gradient around a particle with the pressure gradient around a pile leads to the dependency between equilibrium scour depth and the grain size/structure size ratio. Finally, a new formulation for local equilibrium scour depth based upon turbulent energy spectrum decay is presented. This new formulation reduces the local scour problem to a problem whereby turbulent diffusivity must be better understood. However, this new formulation also appears to show a dependency between equilibrium scour depth and the grain size/structure size ratio. Overall, the analysis presented herein provides several reasons, explanations, and pieces of evidence to suggest that the grain/structure size ratio is an important parameter to consider when computing local equilibrium scour depth.
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Liao, Chung-Ta, Keh-Chia Yeh, Yin-Chi Lan, Ren-Kai Jhong, and Yafei Jia. "Improving the 2D Numerical Simulations on Local Scour Hole around Spur Dikes." Water 13, no. 11 (May 23, 2021): 1462. http://dx.doi.org/10.3390/w13111462.
Full textAbstract:
Local scour is a common threat to structures such as bridge piers, abutments, and dikes that are constructed on natural rivers. To reduce the risk of foundation failure, the understanding of local scour phenomenon around hydraulic structures is important. The well-predicted scour depth can be used as a reference for structural foundation design and river management. Numerical simulation is relatively efficient at studying these issues. Currently, two-dimensional (2D) mobile-bed models are widely used for river engineering. However, a common 2D model is inadequate for solving the three-dimensional (3D) flow field and local scour phenomenon because of the depth-averaged hypothesis. This causes the predicted scour depth to often be underestimated. In this study, a repose angle formula and bed geometry adjustment mechanism are integrated into a 2D mobile-bed model to improve the numerical simulation of local scour holes around structures. Comparison of the calculated and measured bed variation data reveals that a numerical model involving the improvement technique can predict the geometry of a local scour hole around spur dikes with reasonable accuracy and reliability.
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Williams, Priscilla, Ram Balachandar, and Tirupati Bolisetti. "Examination of Blockage Effects on the Progression of Local Scour around a Circular Cylinder." Water 11, no. 12 (December 13, 2019): 2631. http://dx.doi.org/10.3390/w11122631.
Full textAbstract:
An evaluation of scour estimation methods has indicated that the effects of blockage ratio are neglected in both scour modelling and development of new predictive methods. The role of channel blockage on the mechanism and progression of local scour is not well understood, and further analysis is required in order to incorporate this effect into scour estimation. In the present investigation, local scour experiments were carried out under varying blockage ratio. The results were compared with data from literature in order to explore the effects of blockage ratio (D/b, where D is the pier diameter, and b is the channel width) on equilibrium scour depth (dse/D, where dse is the depth of scour at equilibrium). It was determined that D/b had a small influence on both dse/D and the progression of scour depth (ds/D) when relative coarseness D/d50 < 100 (where d50 is the median diameter of sediment), and that the influence appeared to be amplified when D/d50 > 100. The efficacy of scour estimation methods used to predict the progression of local scour was also dependent on D/d50. A method of scour estimation used to predict dse/D was evaluated, and it was similarly found to be particularly effective when D/d50 < 100. In future work, further experiments and analysis in the range of D/d50 > 100 are required in order to establish the role of D/b under prototype conditions and to refine existing scour estimation methods.
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Al-Jubouri, Muhanad, Richard P. Ray, and Mahmoud Saleh Al-Khafaji. "Unraveling Debris-Enhanced Local Scour Patterns around Non-Cylindrical Bridge Piers: Experimental Insights and Innovative Modeling." Sustainability 15, no. 22 (November 14, 2023): 15910. http://dx.doi.org/10.3390/su152215910.
Full textAbstract:
Bridge structures face a critical threat from localized scour-induced damage, prompting urgent attention to civil infrastructure resilience. Prior research has primarily focused on the influence of pier shapes on scour patterns. However, the exploration of the combined effects of various debris shapes, each possessing distinct properties, on predictive scour depth models around the non-cylindrical pier has hitherto remained less researched. This study explored the complex dynamics governing local scour around bridge piers, focusing on the influence of surface and near-surface debris. This research shed light on changes in scour depth by investigating factors like pier geometries, debris arrangements, and submersion depths. The experiments and analysis revealed the effects of various pier shapes—cylindrical, square, rectangular, oblong, oval, and lenticular—on scour patterns. Different geometries influenced primary scour zones and affected areas, with square piers causing the deepest scour and lenticular ones showing shallower instances. Scour depths typically peaked upstream across geometries, but ogival and lenticular shapes exhibited unique patterns. The research also introduced a formula that integrated debris attributes into predictive scour depth modeling, validated with favorable accuracy. Ultimately, this predictive model advances scour prediction, particularly in debris-laden flows, offering valuable insights for engineering and management practices in understanding real-world scour mechanisms and hydraulic dynamics.
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Kadono, Takuma, Sho Kato, Shinichiro Okazaki, Toshinori Matsui, Yoshio Kajitani, Masahide Ishizuka, and Hidenori Yoshida. "Effects of Dynamical Change in Water Level on Local Scouring around Bridge Piers Based on In-Situ Experiments." Water 13, no. 21 (October 27, 2021): 3015. http://dx.doi.org/10.3390/w13213015.
Full textAbstract:
To evaluate the stability of bridge piers affected by the local scouring, the existing formulas for estimating the maximum local scour depth have been developed based on the results of experiments conducted under a constant water level. However, the applicability of these formulas to the cases where the water level rises and falls, such as a water level change in a real river, is not clear. In this study, water flow experiments were conducted on cylindrical and oval bridge pier models to investigate the effect of iterated water level change on the progression of local scour around piers. Results of experiments with cylindrical and oval pier showed that the local scour depth and length increased by an iterated action of the water level change; however, these values converged after the number of iterated actions reached a certain time. The local scour length at upstream of the bridge pier was approximately 1.8 times larger than the theoretical value, which was calculated through the local scour depth and angle of repose in water. The local scour length is an important parameter for defining the streambed protection zone, which is one of the measures against local scour, and we showed that the streambed protection zone needs to be defined more widely.
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Dou, Xiping, Xinzhou Zhang, Xiao-dong Zhao, and Xiangming Wang. "LOCAL SCOUR CHARACTERISTICS OF GROINS AT TIDAL WATERWAYS AND THEIR SIMULATION." Coastal Engineering Proceedings 1, no. 32 (January 31, 2011): 66. http://dx.doi.org/10.9753/icce.v32.sediment.66.
Full textAbstract:
For the channel regulation in tidal rivers, groins are often used as typical hydraulic structures. Precisely predicting the local scour depth at the groin head is the key for the project of river regulation. The local scour of groins for tidal rivers is significantly different from that for the undirectional steady flow of general rivers. In the present paper, a three-dimendional (3D) mathematical model for turbulence and sediment transport are establishmented. The local scour near the groin under the actions of tidal current and steady flow are simulated by established 3D turbulence and sediment transport numerical model.The differences of the scour development and the scour pattern near the groin under these two actions are compared.
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Ying, Qiang. "Formula Type of Local Scour Depth on Spur Dike Nose." Applied Mechanics and Materials 641-642 (September 2014): 271–74. http://dx.doi.org/10.4028/www.scientific.net/amm.641-642.271.
Full textAbstract:
This passage introduces the formation process of scour hole, analyzes the main factors contributed to the local scour hole’s depth and classifies today’s calculation methods of scour depth into three categories. Then, given the conditions where those methods can be applied and drawbacks of those methods, this article also recommends some suggested formula in calculation.
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Xiang, Qiqi, Kai Wei, Fang Qiu, Changrong Yao, and Yadong Li. "Experimental Study of Local Scour around Caissons under Unidirectional and Tidal Currents." Water 12, no. 3 (February 27, 2020): 640. http://dx.doi.org/10.3390/w12030640.
Full textAbstract:
Local scour around caissons under currents has become one of the main factors affecting the safety of foundation construction and operation in coastal and offshore bridge engineering. Local scour occurs not only in the operation stage, when the caisson has settled into the sediment, but also in the construction stage, when the caisson is suspended in water. In this study, the local scour induced by unidirectional and tidal currents around settled caissons with different cross-sections (circular, square, and diamond) was experimentally investigated. Circular and square caissons were selected to investigate the difference in local scour of suspended caissons under unidirectional and tidal currents. The main findings from the experimental results were: (1) the temporal development of scour under tidal current was slower than that of unidirectional current; (2) the effect of current type can significantly influence the size and location of maximum scour depth around circular and square caissons; (3) the appropriate choice of cross-section could reduce the maximum scour depth around the settled caisson; (4) the maximum scour depth of tidal current was smaller than that of unidirectional current when the caisson was settled into the sediment, while the opposite effect occurred when the caisson was suspended in water.
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Stahlmann, Arne, and Torsten Schlurmann. "PHYSICAL MODELING OF SCOUR AROUND TRIPOD FOUNDATION STRUCTURES FOR OFFSHORE WIND ENERGY CONVERTERS." Coastal Engineering Proceedings 1, no. 32 (January 27, 2011): 67. http://dx.doi.org/10.9753/icce.v32.sediment.67.
Full textAbstract:
As a step to further develop the share of renewable energies, the first German offshore test site alpha ventus has been installed in the North Sea in 2009 in water depths of 30 m, where experience shall be gained and made available for
future offshore wind farms. Regarding converter foundations in deep water, it is well known that in most cases scour phenomena occur around the structures. Due to the complexity of the tripod foundations, significant knowledge gaps in scour progression in general and especially in detail as well as its probable effects on the stability and durability are given. Therefore, investigations on scouring phenomena around complex foundation structures like the tripod are
carried out within the research project. The investigation method consists of a unique combination of local scour monitoring as well as physical and numerical modeling, whereas the physical modeling part was carried by means of 1:40 laboratory tests and 1:12 large-scale physical model tests in wave flumes. The results show that scours around the tripod foundation do not only occur directly around the foundation piles, but also in the near-field of the structure. Compared to first in-situ measured scours in the test site, at least a good qualitative agreement of the modeled scour depths and evolutions could be shown.
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HUSAIN, D., A. QURAISHI, and A. ALIBRAHIM. "Local Scour at Bridge Abutments." Journal of King Abdulaziz University-Engineering Sciences 10, no. 1 (1998): 141–53. http://dx.doi.org/10.4197/eng.10-1.10.
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Sheppard, D. Max. "Overlooked Local Sediment Scour Mechanism." Transportation Research Record: Journal of the Transportation Research Board 1890, no. 1 (January 2004): 107–11. http://dx.doi.org/10.3141/1890-13.
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Melville, B. W. "Local Scour at Bridge Abutments." Journal of Hydraulic Engineering 118, no. 4 (April 1992): 615–31. http://dx.doi.org/10.1061/(asce)0733-9429(1992)118:4(615).
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Ettema, R., E. A. Mostafa, B. W. Melville, and A. A. Yassin. "Local Scour at Skewed Piers." Journal of Hydraulic Engineering 124, no. 7 (July 1998): 756–59. http://dx.doi.org/10.1061/(asce)0733-9429(1998)124:7(756).
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Chiew, Y. M., and B. W. Melville. "Local scour around bridge piers." Journal of Hydraulic Research 25, no. 1 (January 1987): 15–26. http://dx.doi.org/10.1080/00221688709499285.
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Khanbilvardi, R. M., M. W. Akhtar, and A. S. Rogowski. "LOCAL SCOUR AROUND CYLINDRICAL OBJECTS." Journal of the American Water Resources Association 24, no. 4 (August 1988): 839–45. http://dx.doi.org/10.1111/j.1752-1688.1988.tb00935.x.
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Song, Feihu, Jun Wang, Zhenhua Zhang, Tiejie Cheng, Guowei Li, and Jueyi Sui. "Local Scour around Side-by-Side Double Piers in Channel Bends under Ice-Covered Conditions—An Experimental Study." Water 15, no. 13 (June 21, 2023): 2317. http://dx.doi.org/10.3390/w15132317.
Full textAbstract:
The pier scour process is normally intensified in the presence of an ice cover, which poses risks to the longevity and safety of bridges. In the present study, the impact of the densimetric Froude number, locations, and pier spacing of side-by-side piers on the local scour depth under ice-covered flow conditions were investigated based on clear water scour experiments in an S-shaped laboratory flume. The results demonstrated that the local scour at piers along the convex bank was more substantial than that along the concave bank when other factors stayed identical. The densimetric Froude number clearly has more impact on local scour at piers along the convex bank than that along the concave bank. Different from the mechanism of the pier scour in a straight channel, the scour depth around a pier along the convex bank in the S-shaped flume increases as the distance between two piers (or pier spacing) increases, while it decreases around the piers along the concave bank. Similar scour patterns were observed when the side-by-side piers were installed at different bend apex cross-sections. The maximum local scour depths at piers along the convex bank measured at different bend apex cross-sections were relatively unchanged when other influencing factors were held constant. However, the maximum scour depth around piers along the concave bank decreased as the bends increased toward downstream.
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Pandey, Manish, Su-Chin Chen, P. K. Sharma, C. S. P. Ojha, and V. Kumar. "Local Scour of Armor Layer Processes around the Circular Pier in Non-Uniform Gravel Bed." Water 11, no. 7 (July 11, 2019): 1421. http://dx.doi.org/10.3390/w11071421.
Full textAbstract:
Flume experiments have been carried out under clear water scour conditions to analyze the maximum equilibrium scour depth and scour processes in armored streambeds. A total of 85 experiments have been carried out using different diameters of circular piers and non-uniform gravels. A graphical approach for dimensionless scour depth in equilibrium condition around the circular pier in armored streambeds has been developed. As per this curve, the maximum dimensionless scour depth variation with dimensionless armor particle size depends on the densimetric particle Froude number (Frd50), and the decreasing rate of dimensionless scour depth decreases with the value of Frd50.
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Wu, Peng, and Ram Balachandar. "Local scour around bridge abutments including effects of relative bed coarseness and blockage ratio." Canadian Journal of Civil Engineering 43, no. 1 (January 2016): 51–59. http://dx.doi.org/10.1139/cjce-2014-0487.
Full textAbstract:
Based on laboratory scale experiments, the role of relative bed coarseness, approach flow depth, and blockage ratio on local scour around semi-circular bridge abutments are discussed. The results reveal that the approach flow depth and relative bed coarseness have a very strong influence on the scour geometry. With the increase of relative bed coarseness, the scour width and scour depth decrease correspondingly. Larger blockage ratios result in larger scour but the relative effects is the smallest compared to the approach flow depth and relative bed coarseness. An empirical equation is developed based on the experimental results. The study provides additional support for considering relative bed coarseness, flow depth, and blockage ratio in scour prediction formulae.
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Kantarzhi, I. G., and A. V. Kuprin. "NATURAL PROCESSES AS JUSTIFICATION FACTORS FOR DECISIONS ON PORT HYDRAULIC STRUCTURES." Геоэкология. Инженерная геология. Гидрогеология. Геокриология, no. 1 (January 1, 2023): 34–40. http://dx.doi.org/10.31857/s0869780923010046.
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The effects of sea waves and currents on harbour hydraulic structures are analysed from published open source data and the characteristics of scour from waves, including tsunami waves, are considered. Local bottom scour threatening the general stability of gravity-type engineering structures can arise under the effect of storm waves and currents, jets from ship propulsion devices and tsunami waves near hydraulic engineering structures. The types of scour mechanisms from sea waves have been investigated, i.e., local, general, and overtopping scour. There is a lack of sufficient measurement data for general scour to verify the calculation methods. Generally, general scour does not damage a structure, although it can contribute to its destruction by other types of scour when they overlap. Therefore, existing studies mainly focus on the analysis of local scour. The relationship between local scour and ground liquefaction and their influence on the stability of marine hydraulic structures is established. Failure mechanisms of hydraulic structures due to erosion by tsunami waves are analyzed: leeward and seaward toe scour, crown armour failure, parapet wall failure, sliding failure. The tsunami wave scour enhancement parameter is given, which is the fraction by which the pore pressure gradient reduces the frictional forces resisting scour. Significant ground instability occurs when the scour amplification parameter Λ exceeds a value of 0.5 (Λ ≥ 0.5). The parameter Λ can be used to assess areas where instantaneous liquefaction may be responsible for scour and sediment movement and to further recalculate erosion depths obtained without considering liquefaction. Liquefaction from a tsunami wave may penetrate up to 28% of the maximum erosion depth due to shear forces. The liquefaction phenomenon may occur due to a sudden drop in the water level in the area of return flow concentration. Consequently, the liquefaction phenomenon must be considered in the stability and erosion analysis around the structure.
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Najafzadeh, Mohammad, Mohammad Rezaie Balf, and Esmat Rashedi. "Prediction of maximum scour depth around piers with debris accumulation using EPR, MT, and GEP models." Journal of Hydroinformatics 18, no. 5 (March 19, 2016): 867–84. http://dx.doi.org/10.2166/hydro.2016.212.
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Pier scour phenomena in the presence of debris accumulation have attracted the attention of engineers to present a precise prediction of the local scour depth. Most experimental studies of pier scour depth with debris accumulation have been performed to find an accurate formula to predict the local scour depth. However, an empirical equation with appropriate capacity of validation is not available to evaluate the local scour depth. In this way, gene-expression programming (GEP), evolutionary polynomial regression (EPR), and model tree (MT) based formulations are used to develop to predict the scour depth around bridge piers with debris effects. Laboratory data sets utilized to perform models are collected from different literature. Effective parameters on the local scour depth include geometric characterizations of bridge piers and debris, physical properties of bed sediment, and approaching flow characteristics. The efficiency of the training stages for the GEP, MT, and EPR models are investigated. Performances of the testing results for these models are compared with the traditional approaches based on regression methods. The uncertainty prediction of the MT was quantified and compared with those of existing models. Also, sensitivity analysis was performed to assign effective parameters on the scour depth prediction.
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Alwan, Husam Hadi, Hayder H. H. Kamonna, and Noor Alaa Hashim. "EVALUATION OF LOCAL SCOUR DEVELOPMENT DOWNSTREAM AN APRON OF DIFFERENT ANGLES FOR AN OGEE SPILLWAY." Kufa Journal of Engineering 7, no. 3 (October 9, 2016): 1–12. http://dx.doi.org/10.30572/2018/kje/731198.
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Local scour downstream of hydraulic structures, such as low head and high head structures, spillways, and culverts is an important research field due to its significant practical value. In this study laboratory experiments were conducted to compute the local scour downstream apron of an ogee spillway under different slopes of apron to study its effect on the characteristics of the scour. Developed physical models for spillway and aprons are installed into the water in the channel where conducted under subcritical flow and clear-water condition by using uniform cohesionless (soil) as bed material with a medium grain size (d50 = 0.65 mm). Four angles of an apron were used (0 ̊, 2.73 ̊, 5.19 ̊, and 7.43 ̊) to show the effect of the slope for apron on local scour. It is found that the slope of an apron is one of the important parameter to reduce the local scour depth and the extent of scour hole. The influence of slope for aprons angle showed a reduction of about (53, 46, and 35) % in the maximum scour depth and about (33, 49, and 33) % in the maximum scour length compared with horizontal apron for angles (2.73 ̊, 5.19 ̊, and 7.43 ̊), respectively.
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Ben Meftah, Mouldi, Diana De Padova, Francesca De Serio, and Michele Mossa. "Secondary Currents with Scour Hole at Grade Control Structures." Water 13, no. 3 (January 28, 2021): 319. http://dx.doi.org/10.3390/w13030319.
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Most studies on local scouring at grade control structures have principally focused on the analysis of the primary flow field, predicting the equilibrium scour depth. Despite the numerous studies on scouring processes, secondary currents were not often considered. Based on comprehensive measurements of flow velocities in clear water scours downstream of a grade control structure in a channel with non-cohesive sediments, in this study, we attempted to investigate the generation and turbulence properties of secondary currents across a scour hole at equilibrium condition. The flow velocity distributions through the cross-sectional planes at the downstream location of the maximum equilibrium scour depth clearly show the development of secondary current cells. The secondary currents form a sort of helical-like motion, occurring in both halves of the cross-section in an axisymmetric fashion. A detailed analysis of the turbulence intensities and Reynolds shear stresses was carried out and compared with previous studies. The results highlight considerable spatial heterogeneities of flow turbulence. The anisotropy term of normal stresses dominates the secondary shear stress, giving the impression of its crucial role in generating secondary flow motion across the scour hole. The anisotropy term shows maximum values near both the scour mouth and the scour bed, caused, respectively, by the grade control structure and the sediment ridge formation, which play fundamental roles in maintaining and enhancing the secondary flow motion.
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Ahmad, N., T. Mohamed, F. H. Ali, and B. Yusuf. "Clear-water local scour at wide piers in shallow-water flow." Water Practice and Technology 9, no. 3 (September 1, 2014): 331–43. http://dx.doi.org/10.2166/wpt.2014.035.
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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.