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Scour of the soil by flowing water around bridge supports is the number one reason for bridge collapse. Predicting the depth of the scour hole is an integral part of the bridge foundation design, as it impacts the depth of the piles. Indeed, the scour depth must be ignored in the vertical and horizontal resistance of the piles. This paper presents a method to calculate the maximum depth of the scour hole around bridge supports when subjected to a constant water velocity. Most existing methods take into account the water velocity and the geometry of the obstacle but not the soil type. The method presented in this paper keeps those important variables and adds the paramount influence of the soil erosion characteristics. It is developed on the basis of 94 flume tests, some of them very large laboratory-scale tests, as well as dimensional analysis and experience. It applies to pier scour, contraction scour, and abutment scour. The method is evaluated by comparing the maximum scour depth predictions against measured data from 10 databases of pier, contraction, and abutment scour depths. [ABSTRACT FROM AUTHOR]

Damage to bridge crossings during flood events endangers the lives of the traveling public and causes costly disruptions to traffic flow. The most common causes of bridge collapse are scouring of the streambed and banks and erosion of highway embankments. This study couples a synthetic river flow simulation technique with a scour model for cohesive soils and determines the expected scour depth for a given lifetime of the bridge. A fractionally differenced autoregressive integrated moving average model generates synthetic streamflow sequences of the same length as the expected lifetime of the bridge. The scour model predicts the progression of scour depth through time in a multilayered soil. The model is used to determine the scour depth associated with different replicates of the synthetic flow sequences of the same length as the lifetime of the bridge. The probability distribution of scour depth is estimated by repeating this simulation procedure over a number of independent realizations of streamflow series for a given life of the bridge. This approach provides a framework for the probabilistic design and risk analysis of bridge foundations subjected to scour. [ABSTRACT FROM AUTHOR]

Compares the depth of scour in sand and in clay and investigated the effects of the Reynolds number, Froude number and approach flow depth on scour depth. Experimental equipment and procedure; Discussion on hyperbolic extrapolation; Experimental results and data analysis; Conclusions.

Proposes the Scour Rate In COhesive Soils (SRICOS) method to predict the scour depth versus time around a cylindrical bridge pier of diameter founded in clay. Total number of bridges collapsed in the United States; Division of scour; Details on shear stress; Maximum depth of scour; Method improvements; Conclusions.

Presents comments on a study undertaken by researchers on closure to flume tests for scour in clay at circular piers. Accuracy of scour depth equation that correlates constant y[subs]/D to constant R with that of constant FD; Pier reynolds number values for different scour tests performed; Comparisons between scour depth versus time curve and exponential and hyperbolic model.