Clear-Water Scour at Pile Groups

Abstract

Groups of piles are frequently used as bridge foundations. Different group configurations, characterized by different pile spacing, skew-angle, number, and arrangement of pile group columns interact differently with the flow field and lead to different scour patterns and equilibrium scour depth. There have been a number of past studies on the characterization of scouring at pile groups, but most of them report short duration scour experiments. A priori, such short durations may be postulated to inherently carry important uncertainties into existing scour predictors. In this study, 75 long-duration laboratory tests were run under steady, clear-water flow close to the threshold for initiation of sediment motion, to address the effect of time, pile spacing, skew-angle and number of pile group columns on the equilibrium scour depth. Pile groups consisted of matrical arrangements of one, two, or three columns of four rows, with spacings of 1, 2, 3, 4.5, and 6 pile diameters; the tested skew-angles were 0, 15, 30, 45, and 90°. Important contributions were achieved on (1) the impact of the duration of tests on the shape of the scour hole as well as on the precision of coefficients involved in current predictors, (2) the most unfavorable skew angle, (3) the behavior of collapsed pile groups, (4) the maximum scour depth at pile groups composed of a single alignment, and (5) the performance of two current predictors of scour depth at pile groups. Two formulations of a predictor for the calculation of an aggregated pile group factor are suggested.

Impact Assessment of Pier Shape and Modifications on Scouring around Bridge Pier

“…In the first phase, a series of 24 runs on six different pier shapes with different diameters (D p = 5 and 10 cm) for two different median sediment sizes (d 50 = 0.71 mm and 0.98 mm), all under a clear water scour condition, were performed. The values of the most important control variables and non-dimensional parameters characterizing the experiments, including those reported by Lança et al [48], are summarized in Table 3.…”

Computational Modeling of Flow and Scour around Two Cylinders in Staggered Array

“…For instance, Briaud et al [8] reported that until 1999, approximately 60% of bridge failures in the United States was because of the local scouring around the piles and Hunt [9] documented more than 1502 bridge failure occurred from 1996 to 2005 in the United States. Numerous studies on local scour around circular pile groups have been conducted by laboratory experiments [10][11][12][13]. The objective of those works was an estimation of maximum scour depth around pile groups for safe and economic designs.…”

“…In addition to the estimation of scour depth, some studies deal with proposing scour countermeasures at pier groups [14,15]. Thus, some semi-empirical equations for maximum scour depth have been proposed [10,11,13]. However, most of these equations overestimated the maximum scour depth due to the scaling effect [16,17].…”

Local Scour at Complex Bridge Piers in Close Proximity under Clear-Water and Live-Bed Flow Regime

“…Figure 4 provides more detailed setup information of the MTA transducers at one of the piers, as well as the numbering scheme for the transducers. Previous studies, including Zhao and Sheppard [4], Lança et al [10], and Yang et al [28] have shown that, for scour at a group of piles or a stand-alone skewed Depth-averaged velocities were measured by a Nortek Vectrino+ ADV made in Norway. A relationship was found between the measured flow velocity, the reading of the electromagnetic flow meter, and the working frequency of the pump controller.…”

“…A typical complex bridge pier often consists of a wall-like column supporting the bridge deck and superstructures, a pile-cap under the column, and a group of piles supporting the pile-cap. Complex bridge piers are usually built in close proximity to each other for large bridges with multiple lanes, parallel companion bridges (especially highway-railway Previous studies have paid much attention to current-induced scour at multiple piles (Hannah [2]; Elliott and Baker [3]; Zhao and Sheppard [4]; Sumer et al [5,6]; Ataie-Ashtiani and Beheshti [7]; Amini et al [8]; Liang et al [9]; Lança et al [10]; Das and Maxumdar [11]; Wang et al [12]; Khaple et al [13]; and Kim et al [14]) and scour at complex piers (Jones and Sheppard [15]; Coleman [16]; Sheppard and Glasser [17]; Ataie-Ashtiani et al [18]; Grimaldi and Cardoso [19]; Beheshti & Ataie-Ashtiani [20,21]; Moreno et al [22][23][24]; Ferraro et al [25]; Amini et al [26]; Baghbadorani et al [27]; and Yang et al [28]), respectively. However, there is still no solution for dealing with scenarios with multiple complex piers, indicating an obvious gap of the existing knowledge.…”