**The study of convergent and divergent slots on scour reduction around abutment**

*Ain Shams Engineering Journal*( IF 1.949 )

**Pub Date : 2020-11-19**

*, DOI:*

*10.1016/j.asej.2020.07.031*

Mehran Sehat; Amir Abbas Kamanbedast; Amin Bordbar; Alireza Masjedi; Mohammad Heidarnejad

Bridges are among the oldest, most important and basic communication structures mainly built on the rivers. Many of them are annually destroyed due to the local scouring phenomenon. The current study used convergent and divergent slot tools on abutments, and performed 45 tests to reduce the detrimental effects of this phenomenon around the rectangular bridge abutment. Experiments were performed in clear water, subcritical flows, and flow states $\frac{V}{{V}_{c}}=0.54\text{,}0.65\text{,}0.76\text{,}0.86\text{,}\phantom{\rule{5.0pt}{0ex}}and\phantom{\rule{5.0pt}{0ex}}0.95$ The results showed that, similar to the non-slotted abutment, the flow was downward near the water surface in all slotted abutment models. The maximum scour depth, in all slotted abutment models, was observed at the reference point, indicating a generally similar scour-affected bed topography around non-slotted and slotted bridge abutments. The effective flow intensity and pressure gradient were reduced due to part of the flow passing through the slot, which in turn caused significant changes in the depth and dimensions of the scour hole around the abutment and downstream sedimentation in different slot and flow models. Also, the results suggested the more significant impact of the convergent slot on scour reduction than a divergent one. Both convergent and divergent slots managed to limit scouring. The abutments with convergent slots and H2/H1 ratios of 0.8, 0.6, 0.4, and 0.2 reduced scouring by 35, 39, 42, and 50%, respectively, compared to the non-slotted reference model. On the other hand, abutments with divergent slots and H2/H1 ratios of 1.8, 1.6, 1.4, and 1.2 lowered scouring by 5, 9, 21, and 34%, respectively, in comparison with the non-slotted reference model.