Journal of Hydraulic Research
2017
Bridge scour; flood waves; local scour; temporal scour; unsteady hydraulics
The time-dependent bridge pier scour during flood waves is analysed. Scour experiments were conducted in a novel installation able to produce complex hydrographs with high precision. Experimental data were used to test scour formulas including a new mathematical model. Results confirm the reliability and superior performance of the proposed dimensionless, effective flow work based model under steady and unsteady hydraulic conditions. Analyses highlight the impact of different hydrographs on scour, demonstrating the strong control by the hydrograph shape of the temporal evolution of scour depth and scour rate, although final scour after a flood only depends on the total effective flow work exerted by the hydrograph on the sediment bed. Hysteresis between flow discharge and scour rate is reported and explained. Flow acceleration is shown to play a minor role in scouring. The proposed model is a promising alternative for computation of local scour under highly unsteady hydraulic conditions.
OSCAR LINK,
Professor, Department of Civil Engineering, University of Concepción, Concepción, Chile
Email: olink@udec.cl (author for correspondence)
CRISTIAN CASTILLO,
MSc Student, Department of Civil Engineering, University of Concepción, Concepción, Chile
Email: criscastillo@udec.cl
ALONSO PIZARRO,
PhD Student, Department of European and Mediterranean Cultures, University of Basilicata, Matera, Italy
Email: alonso.pizarro@unibas.it
ALEJANDRO ROJAS,
Associate Professor, Department of Electric Engineering, University of Concepción, Concepción, Chile
Email: arojasn@udec.cl
BERND ETTMER,
Professor, Department of Water and Waste Management, University of Applied Sciences Magdeburg, Magdeburg, Germany
Email: bernd.ettmer@hs-magdeburg.de
CRISTIÁN ESCAURIAZA,
Associate Professor, Departmento de Ingeniería Hidráulica y Ambiental, Pontificia Universidad Católica de Chile, Santiago, Chile
Email: cescauri@ing.puc.cl
SALVATORE MANFREDA,
Associate Professor, Department of European and Mediterranean Cultures, University of Basilicata, Matera, Italy
Email: salvatore.manfreda@unibas.it
