scholarly journals New stochastic modeling strategy on the prediction enhancement of pier scour depth in cohesive bed materials

2020 ◽  
Vol 22 (3) ◽  
pp. 457-472 ◽  
Author(s):  
Ahmad Sharafati ◽  
Ali Tafarojnoruz ◽  
Zaher Mundher Yaseen
Keyword(s):  
Group Method ◽  
Scour Depth ◽  
Cohesive Soils ◽  
Reliable Prediction ◽  
Pier Scour ◽  
Bed Materials ◽  
Modeling Strategy ◽  
Generalized Likelihood Uncertainty Estimation ◽  
Cohesive Bed ◽  
Improvement Index

Abstract Scouring around the piers, especially in cohesive bed materials, is a fully stochastic phenomenon and a reliable prediction of scour depth is still a challenging concern for bridge designers. This study introduces a new stochastic model based on the integration of Group Method of Data Handling (GMDH) and Generalized Likelihood Uncertainty Estimation (GLUE) to predict scour depth around piers in cohesive soils. The GLUE approach is developed to estimate the related parameters whereas the GMDH model is used for the prediction target. To assess the adequacy of the GMDH-GLUE model, the conventional GMDH and genetic programming (GP) models are also developed for evaluation. Several statistical performance indicators are computed over both the training and testing phases for the prediction accuracy validation. Based on the attained numerical indicators, the proposed GMDH-GLUE model revealed better predictability performance of pier scour depth against the benchmark models as well as several gathered literature studies. To provide an informative comparison among the proposed techniques (i.e. GMDH-GLUE, GMDH, and GP models), an improvement index () is employed. Results indicated that the GMDH-GLUE model achieved = 6% and = 3%, demonstrating satisfying performance improvement in comparison with the previously proposed GMDH model.

Analysis of Clear-Water Scour at Bridge Contractions in Cohesive Soils

2002 ◽  
Vol 1797 (1) ◽  
pp. 3-10 ◽  
Author(s):  
Oktay Güven ◽  
Joel G. Melville ◽  
John E. Curry
Keyword(s):  
Scour Depth ◽  
Cohesive Soils ◽  
Clear Water ◽  
Maximum Value ◽  
Total Head ◽  
Long Time ◽  
Simplifying Assumptions ◽  
Bed Materials ◽  
Cohesive Bed ◽  
Made In

A new, simplified theory for the analysis of the time-dependent development of the depth of scour at bridge contractions in cohesive soils under clear-water conditions is presented. The new theory is an extension of the clear-water scour theory for a long contraction currently used for non-cohesive bed materials. It is based on the “scour rate in cohesive soils” concepts introduced recently by Briaud and his colleagues at Texas A&M University. A description of the simplifying assumptions made in the development of the theory and several applications with different bed soils and flow conditions are presented to illustrate the effects of various assumptions on the estimate of the scour depth. Limitations of the theory are also discussed. The results indicate that a very long time may be required in some cohesive soils for the scour depth to reach its maximum value for a given flow condition. The results also indicate that significant differences in the estimate of the scour depth may occur depending on the assumptions made about the behavior of the water surface elevation and the total head in the contraction during the development of the scour in the contraction.

Evaluation of Selected Pier-Scour Equations Using Field Data

1996 ◽  
Vol 1523 (1) ◽  
pp. 186-195 ◽  
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.

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

2013 ◽  
Vol 67 (5) ◽  
pp. 1121-1128 ◽  
Author(s):  
Mohammad Najafzadeh ◽  
Gholam-Abbas Barani ◽  
Masoud Reza Hessami Kermani
Keyword(s):  
Back Propagation ◽  
Support Vector ◽  
Group Method ◽  
Scour Depth ◽  
Back Propagation Algorithm ◽  
Clear Water ◽  
Sediment Size ◽  
Svm Model ◽  
Vector Machines ◽  
Abutment Scour

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

scholarly journals Scour around Piers under Waves: Current Status of Research and Its Future Prospect

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2212 ◽  
Author(s):  
Ainal Hoque Gazi ◽  
Mohammad Saud Afzal ◽  
Subhasish Dey
Keyword(s):  
Process Development ◽  
Future Prospect ◽  
Review Article ◽  
Current Status ◽  
Scour Depth ◽  
Pier Scour ◽  
Scour Hole ◽  
The Future ◽  
Bridge Failure

In this review article, the current status of research on pier scour under waves is presented. This includes a summary of different bridge failure events due to scour, scour mechanism, scour depth predictors under waves, influence of pier shape on scour depth formation, shape of scour hole around piers, and many others. Further, this article describes the scour process, development of scour depth predictors, and the complexity involved in the scour related calculations. Finally, the future scope of research is delineated.

Hydrographs and Estimates of Scour Depth Excess for Pier Scour Prediction

2011 ◽  
Vol 2262 (1) ◽  
pp. 193-199
Author(s):  
Francis C. K. Ting ◽  
Ryan J. Larsen ◽  
Allen L. Jones
Keyword(s):  
Scour Depth ◽  
Pier Scour

Group method of data handling to predict scour depth around bridge piers

2012 ◽  
Vol 23 (7-8) ◽  
pp. 2107-2112 ◽  
Author(s):  
Mohammad Najafzadeh ◽  
Hazi Mohammad Azamathulla
Keyword(s):  
Bridge Piers ◽  
Group Method ◽  
Scour Depth ◽  
Data Handling

Prediction of Scour at Bridge Pier Foundations Founded on Rock and Other Earth Materials

2000 ◽  
Vol 1696 (1) ◽  
pp. 67-70 ◽  
Author(s):  
George W. Annandale
Keyword(s):  
Laboratory Data ◽  
Bridge Pier ◽  
Scour Depth ◽  
Stream Power ◽  
Index Method ◽  
Pier Scour ◽  
Bridge Pier Scour

The erodibility index method, which can be used to predict scour thresholds for rock and other earth materials, is described. The scour threshold is defined by a relationship between the erodibility index and stream power that is based on analysis of field and laboratory data. An explanation of how the method is applied to calculate scour depth is presented, followed by a case study to calculate bridge pier scour.

Flow-Field Complexity and Design Estimation of Pier-Scour Depth: Sixty Years since Laursen and Toch

2017 ◽  
Vol 143 (9) ◽  
pp. 03117006 ◽  
Author(s):  
Robert Ettema ◽  
George Constantinescu ◽  
Bruce W. Melville
Keyword(s):  
Flow Field ◽  
Scour Depth ◽  
Pier Scour

Multi-lens pier scour monitoring and scour depth prediction

2014 ◽  
Vol 167 (2) ◽  
pp. 88-104 ◽  
Author(s):  
Wen-Yi Chang ◽  
Franco Lin ◽  
Jihn-Sung Lai ◽  
Lung-Cheng Lee ◽  
Whey-Fone Tsai ◽  
...  
Keyword(s):  
Scour Depth ◽  
Pier Scour ◽  
Depth Prediction ◽  
Scour Monitoring

scholarly journals Local scour protection using geocell for downstream of spillway

2021 ◽  
Vol 9 (3B) ◽  
Author(s):  
Enes GUL ◽  
◽  
Talha SARICI ◽  
Omerul Faruk DURSUN ◽  
◽  
...  
Keyword(s):  
Local Scour ◽  
Hydraulic Structures ◽  
Scour Depth ◽  
Percentage Reduction ◽  
Confinement System ◽  
Bed Materials ◽  
Scour Protection

Local scour is an important problem for hydraulic structures. The local scour in the downstream of dams causes problems such as the damage of the dam body stabilization, erosion of the slopes, and the submergence of the turbines. There are many studies investigating the local scour prediction of the downstream of the hydraulic structures, but in recent years, these studies have been replaced by studies of local scour reduction. The new idea of confining the bed materials using the geocell is becoming a popular solution. This solution can be especially used for the reinforcement of the soils. In this study, the preventability of the local scour downstream of chute channel by cellular confinement system, also known as geocell, was investigated. As a result, in case of using geocell, percentage reduction of the maximum scour depth up to 40.63% was observed.

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