Scour at uniform cylindrical piers founded in cohesionless sediments has received much attention over the last decades and there are extensive laboratory data for these conditions in literature. However, a few investigators demonstrated that foundation geometry significantly affects scour. This paper presents an experimental study on local scour at piers founded on piles when the top elevation of the pile cap is located at the initial (undisturbed) bed level. Experiments were carried out in a 1 m wide and 20 m long rectangular straight channel at the University of Basilicata, Italy. The bed material was a nearly uniform sand with grain size d50=1.7 mm and sediment gradation equal to 1.5. All the tests were run under plane bed conditions and steady flow regime. The experimental data provide new insights on the temporal variation of scour depth, scour hole length, and scour volume. They are first compared with the predicted values according to HEC-18 approach and results show the suitability of this approach at the equilibrium stage. Then the temporal scour progress is compared to that for uniform cylindrical piers highlighting differences and the shielding effects by the pile cap.
Temporal variation of local scour at bridge piers with complex geometries
OLIVETO, Giuseppe
2012-01-01
Abstract
Scour at uniform cylindrical piers founded in cohesionless sediments has received much attention over the last decades and there are extensive laboratory data for these conditions in literature. However, a few investigators demonstrated that foundation geometry significantly affects scour. This paper presents an experimental study on local scour at piers founded on piles when the top elevation of the pile cap is located at the initial (undisturbed) bed level. Experiments were carried out in a 1 m wide and 20 m long rectangular straight channel at the University of Basilicata, Italy. The bed material was a nearly uniform sand with grain size d50=1.7 mm and sediment gradation equal to 1.5. All the tests were run under plane bed conditions and steady flow regime. The experimental data provide new insights on the temporal variation of scour depth, scour hole length, and scour volume. They are first compared with the predicted values according to HEC-18 approach and results show the suitability of this approach at the equilibrium stage. Then the temporal scour progress is compared to that for uniform cylindrical piers highlighting differences and the shielding effects by the pile cap.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
