Laboratory Study of the Effect of pile in Reducing the scure of of spindle-shaped Bridge pier

Subject Areas : Subjects

Ali Niknam ¹ (Ph.D. Student. Department of Water Science Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran.)
Mohammad Heidarnejad ² (Associate Prof. Department of Water Science Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran.)
Alireza Masjedi ³ (Associate Prof. Department of Water Science Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran.)
Amin Bordbar ⁴ (Assistant Prof. Department of Water Science Engineering, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran.)

Received: 2020-11-23 Accepted : 2022-01-19 Published : 2022-01-21

Keywords: Scour, Spindle-shaped bridge base, pile,

Abstract :

Scour is among the most critical topics in river engineering. A large number of bridges around the world are destructed mainly due to ignoring the hydraulic function in the design of bridges. The use of roughness, collars, submerged plates, and protective piles are among the methods for controlling and reducing local scouring. This study investigated the effect of protective piles in controlling and reducing scouring around spindle-shaped piers. According to the experimental results, by installing 5 piles at an angle of 30˚ with a relative distance (L/D) of 0.5, scouring decreased by 20% relative to the pile-less spindle-shaped pier. This scour reduction can be attributed to the transport of sediments around the pile toward the pier and accumulation of sediments in the middle of piles and in front of the spindle-shaped pier. The other factor reducing local scour is the change in the flow regime and reduced velocity and vortices in front of the spindle-shaped pier. Moreover, as the relative velocity (V/Vc, the ratio of the flow velocity to the critical velocity) increased from 0.54 to 0.95, scouring increased by 165.4% on average. The water flow colliding the spindle-shaped pier and the formation of a downward flow cause scouring. An increase in the flow velocity also increases the vertical velocity and vortices and thereby scouring. The mathematical model simulated by Flow-3D is consistent with the physical model showing an acceptable error rate of 4.3%.

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