Effect of Interaction between Bridge Piers on Local Scouring in Cohesive Soils

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

E3S Web of Conferences ◽

10.1051/e3sconf/20184002003 ◽

2018 ◽

Vol 40 ◽

pp. 02003 ◽

Cited By ~ 2

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.

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Laboratory Flume Experiments on the Formation of Spanwise Large Wood Accumulations: Part II-Effect on local scour

Water Resources Research ◽

10.1029/2019wr024789 ◽

2019 ◽

Vol 55 (6) ◽

pp. 4871-4885 ◽

Cited By ~ 15

Author(s):

I. Schalko ◽

C. Lageder ◽

L. Schmocker ◽

V. Weitbrecht ◽

R. M. Boes

Keyword(s):

Local Scour ◽

Large Wood ◽

Flume Experiments ◽

Laboratory Flume

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Prediction of maximum scour depth around piers with debris accumulation using EPR, MT, and GEP models

Journal of Hydroinformatics ◽

10.2166/hydro.2016.212 ◽

2016 ◽

Vol 18 (5) ◽

pp. 867-884 ◽

Cited By ~ 52

Author(s):

Mohammad Najafzadeh ◽

Mohammad Rezaie Balf ◽

Esmat Rashedi

Keyword(s):

Polynomial Regression ◽

Gene Expression Programming ◽

Laboratory Data ◽

Experimental Studies ◽

Local Scour ◽

Bridge Piers ◽

Scour Depth ◽

Effective Parameters ◽

Pier Scour ◽

Debris Accumulation

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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Mathematical Modeling of Local Scour at Slender and Wide Bridge Piers

Journal of Fluids ◽

10.1155/2016/4835253 ◽

2016 ◽

Vol 2016 ◽

pp. 1-19 ◽

Cited By ~ 7

Author(s):

Youssef I. Hafez

Keyword(s):

Local Scour ◽

Bridge Pier ◽

Angle Of Repose ◽

Bridge Piers ◽

Bridge Scour ◽

Pier Scour ◽

Bed Scour ◽

Bed Material ◽

Bridge Pier Scour ◽

Mitigation Methods

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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Debris flow impact on a flexible barrier: laboratory flume experiments and force-based mechanical model validation

Natural Hazards ◽

10.1007/s11069-020-04489-5 ◽

2021 ◽

Vol 106 (1) ◽

pp. 735-756

Author(s):

R. Brighenti ◽

L. Spaggiari ◽

A. Segalini ◽

R. Savi ◽

G. Capparelli

Keyword(s):

Debris Flow ◽

Model Validation ◽

Mechanical Model ◽

Flume Experiments ◽

Flexible Barrier ◽

Laboratory Flume

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Evaluation of Selected Pier-Scour Equations Using Field Data

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198196152300123 ◽

1996 ◽

Vol 1523 (1) ◽

pp. 186-195 ◽

Cited By ~ 3

Author(s):

Mark N. Landers ◽

David S. Mueller

Keyword(s):

Field Measurements ◽

Bridge Piers ◽

Critical Ratio ◽

Scour Depth ◽

Flow Depth ◽

Clear Water ◽

Pier Scour ◽

Logarithmic Space ◽

State Highway ◽

Federal Highway

Field measurements of channel scour at bridges are needed to improve the understanding of scour processes and the ability to accurately predict scour depths. An extensive data base of pier-scour measurements has been developed over the last several years in cooperative studies between state highway departments, the Federal Highway Administration, and the U.S. Geological Survey. Selected scour processes and scour design equations are evaluated using 139 measurements of local scour in live-bed and clear-water conditions. Pier-scour measurements were made at 44 bridges around 90 bridge piers in 12 states. The influence of pier width on scour depth is linear in logarithmic space. The maximum observed ratio of pier width to scour depth is 2.1 for piers aligned to the flow. Flow depth and scour depth were found to have a relation that is linear in logarithmic space and that is not bounded by some critical ratio of flow depth to pier width. Comparisons of computed and observed scour depths indicate that none of the selected equations accurately estimate the depth of scour for all of the measured conditions. Some of the equations performed well as conservative design equations; however, they overpredict many observed scour depths by large amounts. Some equations fit the data well for observed scour depths less than about 3 m (9.8 ft), but significantly underpredict larger observed scour depths.

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Enhancing scour protection in river bends: a novel slotted bank-attached vane

Water Science & Technology Water Supply ◽

10.2166/ws.2020.116 ◽

2020 ◽

Vol 20 (6) ◽

pp. 2175-2184

Author(s):

Mohamad Azizipour ◽

Farshid Amirsalari Meymani ◽

Mohammad Mahmoodian Shooshtari

Keyword(s):

Effective Area ◽

Local Scour ◽

Flume Experiments ◽

Rectangular Slot ◽

Outer Bank ◽

Scour Hole ◽

Submerged Vane ◽

River Bends ◽

Scour Protection ◽

Control Erosion

Abstract One of the most effective approaches for bank control erosion is using bank-attached vanes. In spite of the superiority of the bank-attached vanes to spur dikes, the vanes' tips are still vulnerable to local scour caused by flow–structure interaction. In this study, slotted bank-attached vanes are proposed to reduce local scour at the tip of the triangular submerged vane. For this, a rectangular slot is created parallel to the chord of the vane with an area of ten percent of the effective area of the vane surface. Two types of conventional vanes and slotted vanes were installed at different angles of attack of 23, 30, 40 and 60 degrees in an arch flume. Experiments were carried out in clear water conditions with different flow regimes with Froude numbers of Fr = 0.287, 0.304 and 0.322. The results show that the slotted vane outperforms the conventional vane by reducing maximum scour depth by about 70, 20, 17 and 54 percent for different angles of attack of 23, 30, 40 and 60 degrees, respectively. The proposed slotted vane also resulted in reduction of scour hole volume around the vane and formed the scour hole away from the outer bank.

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