Abstract
An important issue in river engineering is to control scour around bridge piers and abutments using either a collar or a slot. This study examines the use of a slot or a collar, either alone or in conjunction with one other, to reduce scour at bridge abutments. In research on abutments equipped with slots only, collars only, and a combination of both were tested 15, 9, and 18 times, respectively. According to the results, in abutments equipped with slots only, the closer the slot is to the channel wall, the better the performance. At the same time, according to the results of research on collars, mere protection of the upstream face of the abutment is not sufficient to prevent down flows due to the presence of horseshoe and wake vortices, but the downstream faces of collars play a substantial role in reducing scour. With an increase in collar length, the scour depth decreases and the scour hole shifts downstream farther away from the abutment. Finally, it was found that the slot–collar combination model takes a more proactive role in reducing scour compared to collars only or slots only. The most robust combinatorial model used managed to fully control scour around abutments. For combinatorial models, scour showed a 42–100% decrease under different flow conditions in an erodible bed.
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Abbreviations
- \( \left( {d_{\text{s}} } \right)_{\text{max} } \) :
-
Maximum depth of the scour hole with no slot and collar \( \left[ L \right] \)
- \( \left( {d_{\text{s}} } \right)_{{{\text{sc}}_{\text{max} } }} \) :
-
Maximum depth of scour hole with collar and slot \( \left[ L \right] \)
- \( \rho \) :
-
Flow density \( \left[ {ML^{ - 3} } \right] \)
- \( \rho_{\text{s}} \) :
-
Density of the sediment particles \( \left[ {ML^{ - 3} } \right] \)
- \( g \) :
-
Gravity acceleration \( \left[ {LT^{ - 2} } \right] \)
- \( L_{\text{a}} \) :
-
Abutment length \( \left[ L \right] \)
- \( B_{\text{a}} \) :
-
Abutment width \( \left[ L \right] \)
- \( Z_{\text{c}} \) :
-
Vertical distance between the collar and the sediment bed \( \left[ L \right] \)
- \( L_{\text{c}} \) :
-
Collar length at the upstream \( \left[ L \right] \)
- \( B_{\text{cv}} \) :
-
Collar length at the downstream \( \left[ L \right] \)
- \( B_{\text{ch}} \) :
-
Collar width \( \left[ L \right] \)
- \( d_{50} \) :
-
Mean particle size \( \left[ L \right] \)
- \( V \) :
-
Mean flow velocity \( \left[ {LT^{ - 1} } \right] \)
- \( \mu \) :
-
Dynamic viscosity \( \left[ {ML^{ - 1} T^{ - 1} } \right] \)
- \( V_{\text{c}} \) :
-
Critical velocity at the movement threshold of the sediment particles \( \left[ {LT^{ - 1} } \right] \)
- \( y \) :
-
Depth of flow \( \left[ L \right] \)
- \( B \) :
-
Channel width \( \left[ L \right] \)
- \( t \) :
-
Scour time \( \left[ T \right] \)
- \( t_{\text{e}} \) :
-
Equilibrium time \( \left[ T \right] \)
- \( \alpha \) :
-
Angle of the flow collision with the abutment \( \left[ - \right] \)
- \( {\text{Fr}} \) :
-
Froude number \( \left[ - \right] \)
- \( {\text{Re}} \) :
-
Reynolds number \( \left[ - \right] \)
- \( G_{\text{s}} \) :
-
Relative density of the sediment particles \( \left[ - \right] \)
- \( \left( { \Pr } \right)_{\text{s}} \) :
-
Percentage of scour depth reduction \( \left[ - \right] \)
- \( \sigma_{\text{g}} \) :
-
Standard deviation of the sediments \( \left[ - \right] \)
- \( W_{\text{s}} \) :
-
Slot width \( \left[ L \right] \)
- \( B_{\text{s}} \) :
-
Slot depth \( \left[ L \right] \)
- \( H_{\text{s}} \) :
-
Slot height \( \left[ L \right] \)
- \( X_{\text{s}} \) :
-
Slot distance from the abutment nose tip \( \left[ L \right] \)
- \( \theta_{\text{s}} \) :
-
Slot angle with respect to the flow \( \left[ - \right] \)
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Osroush, M., Hosseini, S.A. & Kamanbedast, A.A. Countermeasures Against Local Scouring Around Bridge Abutments: Combined System of Collar and Slot. Iran J Sci Technol Trans Civ Eng 45, 11–25 (2021). https://doi.org/10.1007/s40996-020-00443-4
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DOI: https://doi.org/10.1007/s40996-020-00443-4