Abstract
This research explores the effects of different spans of two columns of tandem piers on the characteristics of x-velocity near the river bed based on computational fluid dynamics (CFD) simulations. With a span shorter than 27.5D (D is the diameter of piers), the shape and the lateral range of the x-velocity increases with the increase of distance downwards the x-direction. For the area between the tandem piers and the wall, the VRi/VR1 (the ratio of the x-velocity at the i-th row to the x-velocity of the first row in each model) near the wall increases up to 1.26. For the area between the two columns of tandem piers, the profile of VRi/VR1 changes from a “∩-shape” to an “M-shape” in each model. RAVC (average velocity change ratio) of different spans increases gradually and tends to be stable with the increases of the span. The largest RAVC is about −17.66% with a span of 0.52 m. The RMV (the ratio of the maximum x-velocity among piers in each row in different models to the maximum x-velocity of the two piers arranged side by side) of piers in the first row of different models is around 0.95. The RMV becomes 0.82 at the second pier in each model when the span is shorter than 27.5D, and increases to 0.91 if the span is longer than 27.5D. If the span is longer than 27.5D, the RMV of different piers are close to each other from the 2nd pier to the last one.
Highlights
In the past two decades, many highways have been constructed in China, especially in the western mountainous areas
Tandem piers of longitudinal bridges are distributed in the riverbed, which significantly disturbs river flow fields and causes soil erosion and scour
In comparison with the single pier, the values of turbulence kinetic energy and turbulence intensities decrease around the tandem piers
Summary
In the past two decades, many highways have been constructed in China, especially in the western mountainous areas. To minimize the effects of highway infrastructures on the local environment and biological systems, longitudinal bridges are more frequently adopted. Unlike the conventional bridges that are cross over the river, the longitudinal bridges are built in the river and extended along the river. This eliminates building embankment and tunnels that cause significant effects on the local environment. Half a year after the Xi’an-Hanzhong highway was opened to the public on September 2007, many longitudinal bridges of the Xi’an-Hanzhong highway have found severe scour issues as shown, which affected the foundation safety of bridges Half a year after the Xi’an-Hanzhong highway was opened to the public on September 2007, many longitudinal bridges of the Xi’an-Hanzhong highway have found severe scour issues as shown in Figure 2, which affected the foundation safety of bridges
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