Effects of ice cover on the incipient motion of bed material and shear stress around side-by-side bridge piers

2019 ◽  
Vol 165 ◽  
pp. 102811
Author(s):  
Mohammad Reza Namaee ◽  
Jueyi Sui
Keyword(s):  
Shear Stress ◽  
Ice Cover ◽  
Bridge Piers ◽  
Incipient Motion ◽  
Bed Material

scholarly journals Hazards due to large wood accumulations: Local scour and backwater rise

2018 ◽  
Vol 40 ◽  
pp. 02003 ◽  
Author(s):  
Isabella Schalko ◽  
Lukas Schmocker ◽  
Volker Weitbrecht ◽  
Robert M. Boes
Keyword(s):  
Shear Stress ◽  
Flood Hazard ◽  
Local Scour ◽  
Bridge Piers ◽  
Bed Shear Stress ◽  
Large Wood ◽  
Flume Experiments ◽  
Governing Parameter ◽  
Bed Material ◽  
Movable Bed

Large wood (LW) in rivers increases the flow variability and provides habitats for various species. During flood events, transported logs can accumulate at river infrastructures and increase the flood hazard. LW accumulations result in an upstream backwater rise and may increase local scour, for instance at bridge piers. Consequently, estimates of the resulting backwater rise and local scour are necessary to improve the flood hazard assessment. This study presents the findings of flume experiments with a movable bed on local scour and backwater rise due to LW accumulations. The approach flow conditions and the bed material were varied systematically for a specific LW accumulation volume. For all experiments, the initial condition for the bed material was defined as weak transport, since the bed shear stress was slightly below the critical bed shear stress for incipient motion. The inflow Froude number was identified as the governing parameter for backwater rise due to LW accumulations. The present study confirms the hypothesis that the resulting local scour reduces backwater rise. For the local scour, the unit discharge and the grain size diameter are the decisive parameters.

Further studies of incipient motion and shear stress on local scour around bridge abutment under ice cover

2014 ◽  
Vol 41 (10) ◽  
pp. 892-899 ◽  
Author(s):  
Peng Wu ◽  
Faye Hirshfield ◽  
Jueyi Sui
Keyword(s):  
Experimental Study ◽  
Reynolds Number ◽  
Shear Stress ◽  
Open Channel ◽  
Ice Cover ◽  
Scour Depth ◽  
Incipient Motion ◽  
Clear Water ◽  
Bridge Abutments ◽  
Bridge Abutment

An experimental study was conducted to investigate the scour development around bridge abutments under ice cover with non-uniform natural sands. Two abutments and three non-uniform sediments were used in the research. The mechanism of incipient motion for non-uniform sediments under ice cover was analyzed. By introducing scour angles around two abutments, a relationship between maximum scour depth and velocity was established for clear-water scour under ice cover. Dimensionless shear stress was also calculated and compared with shear Reynolds number for non-uniform sediments. The maximum scour depth and dimensionless shear stress were investigated under both open channel, smooth cover and rough covered conditions. Results show that around the square abutment, the scour angle is smaller than that of the semi-circular abutment. For clear water scour, the maximum scour depth increases due to the presence of ice cover.

Study on Incipient Motion of Consolidated Cohesive Fine Sediment

2012 ◽  
Vol 204-208 ◽  
pp. 354-358
Author(s):  
Jun Wang ◽  
Wei Guo ◽  
Hai Tao Xu ◽  
Zhong Wu Jin ◽  
Yin Jun Zhou
Keyword(s):  
Particle Size ◽  
Shear Stress ◽  
Critical Shear Stress ◽  
Fine Sediment ◽  
Weight Increase ◽  
Unit Weight ◽  
Incipient Motion ◽  
Mean Particle Size ◽  
Dry Unit Weight ◽  
The One

The incipient motion mechanism of cohesive fine sediment is different to the one of non-cohesive sediment. It is related to the consolidation while being influenced by the dry unit weight and particle size. By means of the rectangle piping flume, the influence mechanism of dry unit weight and particle size to critical shear stress of cohesive fine sediment is studied. Experimental results show that on the condition of consolidation, the influence of dry unit weight to incipient motion is divided into two different stages, one is that when dry unit weight increase quickly, but the influence to incipient motion is not greatly, another is that when dry unit weight increase slowly, but the influence to incipient motion is very greatly, the critical dry unit weight to two stages decline as mean particle size decrease. So the mean particle size is finer, the degree of dry unit weight influence to critical shear stress is stronger, and the incipient motion is more difficult when consolidation last longer; it is also shown consolidation is more disadvantageous to incipient motion.

Dimensional Analysis As Applied To Scouring Around Bridge Piers In Alluvial Rivers

1983 ◽  
pp. 59-66
Author(s):  
Abdul Aziz Ibrahim
Keyword(s):  
Froude Number ◽  
Dimensional Analysis ◽  
Bridge Pier ◽  
Bridge Piers ◽  
Alluvial Rivers ◽  
Contraction Ratio ◽  
Scouring Process ◽  
Bed Material

Percubaan telah dibuat untuk menganalisa masalah hakisan dasar di sekitar tiang jambatan di dalam sungai lanar dengan penggunaan cerakinan dimensa. Proses hakisan sekitar tiang jambatan dipengaruhi oleh sebilangan angkubah-angkubah kompleks yang berkaitan. Hakisan di sekliling tiang jambatan didapati bergantung kepada dimensa jambatan dan saluran, Nombor Froude, nisbah pengecutan, ciri-ciri bahan dasar, dan parameter-parameter berhubung dengan alat-alat mengawal hakisan. Data terdahulu juga digunakan bagi menyokong kemasukan dan penyisihan beberapa angkubah yang penting. An attempt has been made to analyse the problem of the erosion around bridge piers in alluvial rivers with the help of dimensional analysis. The scouring process in the vicinity of a bridge pier is controlled by a number of complex interrelated variables. Scour around bridge piers is shown to depend primarily on the dimension of the pier and channel. Froude number, contraction ratio, properties of the bed material and parameters related to devices controlling the scour. Previous data are also employed to support the inclusion or exclusion of some of the important variables.

scholarly journals Bed Shear Stress Influence on Local Scour Geometry Properties in Various Flume Development Conditions

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2346 ◽  
Author(s):  
Kiraga ◽  
Popek
Keyword(s):  
Shear Stress ◽  
Sediment Transport ◽  
Mutual Influence ◽  
Three Dimensional ◽  
Critical Shear Stress ◽  
Water Structure ◽  
Correlation Coefficients ◽  
Bed Shear Stress ◽  
Hole Dimensions ◽  
Bed Material

Numerous approaches in sediment mobility studies highlighted the key meaning of channel roughness, which results not only from bed material granulation but also from various bed forms presence, caused by continuous sediment transport. Those forms are strictly connected with the intensity of particle transport, and they eventuate from bed shear stress. The present paper comprised of local scours geometric dimensions research in three variants of lengthwise development of laboratory flume in various hydraulic properties, both in “clear-water” and “live-bed” conditions of sediment movement. Lots of measurements of the bed conformation were executed using the LiDAR device, marked by a very precise three-dimensional shape description. The influence of the bed shear stress downstream model on scours hole dimensions of water structure was investigated as one of the key factors that impact the sediment transport intensity. A significant database of 39 experimental series, lasting averagely 8 hours, was a foundation for delineating functional correlations between bed shear stress-and-critical shear stress ratio and geometry properties of local scours in various flume development cases. In the scope of mutual influence of bed shear stress and water depth, high correlation coefficients were attained, indicating very good and good functional correlations. Also, the influence of bed shear stress and the total length of the scour demonstrated a high correlation coefficient.

Local scour at piled bridge piers including an examination of the superposition method

2014 ◽  
Vol 41 (5) ◽  
pp. 461-471 ◽  
Author(s):  
Ata Amini ◽  
Bruce W. Melville ◽  
Thamer M. Ali
Keyword(s):  
Bridge Piers ◽  
Prediction Methods ◽  
Scour Depth ◽  
Superposition Method ◽  
Clear Water ◽  
Laboratory Flume ◽  
Pile Cap ◽  
The Individual ◽  
Comparison Of The Results ◽  
Bed Material

An experimental investigation of clear water scour at complex piers is presented. Five complex piers, comprising different configurations of piles, pile cap, and column, were tested in a laboratory flume using uniform bed material. The piers were tested for a range of possible elevations relative to the streambed elevation. Experiments were undertaken using the complex piers and also using the individual components of each complex pier. A comparison of the results for the intact piers and for their components enabled an evaluation of the prediction methods involving superposition of scour depths at piles, pile cap, and pier column. The superposition method is found to give inadequate estimates of total scour depth in many cases.

Three-dimensional numerical simulation of local scour in the vicinity of circular side-by-side bridge piers with ice cover

2020 ◽  
Author(s):  
Mohammad Reza Namaee ◽  
Jueyi Sui ◽  
Yongsheng Wu ◽  
Natalie Linklater
Keyword(s):  
Laboratory Experiments ◽  
Transport Model ◽  
Numerical Models ◽  
Three Dimensional ◽  
Ice Cover ◽  
Local Scour ◽  
Bridge Piers ◽  
Accurate Estimation ◽  
Scour Depth ◽  
Cold Regions

Local scour around piers is one of the primary causes of collapse of bridges that cross rivers. The most severe scouring occurs in cold regions where ice cover significantly changes the velocity profile. Having an accurate estimation of the maximum scour depth around bridge piers, especially in cold regions, is necessary for a safer design of piers. In this study, 3-D numerical models are compared to laboratory experiments to examine the process of local scour around bridge piers with and without smooth and rough ice cover. By using the equation of Meyer-Peter Müller, the sediment transport model is validated to approximate the transport of the sediment particles. Numerical results showed good agreements with experimental observations where the maximum scour depth and Turbulent Kinetic Energy (TKE) around bridge piers were the highest under rough ice cover conditions.

scholarly journals Experimental study on incipient shear stress of consolidated cohesive sediment

2020 ◽  
Vol 13 (18) ◽  
Author(s):  
Caiwen Shu ◽  
Guangming Tan ◽  
Peng Chen ◽  
Jun Wang ◽  
Ping Lv
Keyword(s):  
Experimental Data ◽  
Shear Stress ◽  
Bulk Density ◽  
Cohesive Sediment ◽  
Experimental Results ◽  
Incipient Motion ◽  
Motion Mechanism ◽  
Cohesive Particles ◽  
Sediment Mixtures ◽  
Consolidation Time

Abstract This paper analyzes the incipient motion mechanism of consolidated cohesive sediment. An experimental device based on previous studies was designed to investigate the influencing factors of the incipient shear stress, including the consolidation time, the density of dry bulk, cohesive particles content, and the composition of sediment mixtures. The experimental results indicated that the incipient shear stress of cohesive sediment increased with the increase of consolidation time, dry bulk density, and content of cohesive particles. The incipient motion mechanism of cohesive particles was further investigated using experimental data and theoretical analysis. A formula of the incipient shear stress for cohesive sediment was proposed herein, which is related to both the content of cohesive particles and the relative dry bulk density. The proposed formula was validated by the experimental data, and the calculated values of incipient shear stress using the formula were in good agreement with the experimental results.

Initiation of motion conditions for shale sediments

1983 ◽  
Vol 10 (3) ◽  
pp. 549-554 ◽  
Author(s):  
L. Magalhaes ◽  
T. S. Chau
Keyword(s):  
Shear Stress ◽  
Critical Shear Stress ◽  
Shear Stresses ◽  
Single Particles ◽  
Channel Stability ◽  
High Lift ◽  
Flume Tests ◽  
Load Transport ◽  
Bed Load Transport ◽  
Bed Material

Critical shear stresses for erosion of alluvial shale particles were investigated in a laboratory flume. Tests in the incipient motion conditions of individual particles showed that entrainment of shale bed particles takes place at mean shear stress values 40–50% smaller than other types of non-cohesive and coarse granular material. The low density and platy shape of the shale particles may induce high lift forces, which would account for a decrease in the resistance to erosion of shale channels and greater rates of bed-load transport. Keywords: channel stability, critical shear stress, flume tests, initiation of motion, shale gravels, single particles, weak bed material movement.

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