Author(s): Bruce Melville
Linked Author(s): Bruce W. Melville
Keywords: Scour; Hydraulic structures; Monopile foundations; Riprap protection; Pressure scour; Sluice gates
Abstract: Three cases of scour at hydraulic structures are discussed as shown in the photographs. Experimental data analyses are used to derive simple design relationships, the data being derived from flume tests undertaken at The University of Auckland (UoA) as well as other data where appropriate. A common theme is testing under mobile bed flow conditions using the water and sediment recirculating flumes at UoA, these including 2400 mm wide and 1500 mm wide flumes, both capable of generating flows exceeding 1 m³/s. For each type of scour, countermeasures are discussed. Research of scour at off-shore monopile foundations is being undertaken currently (at the time of writing) as part of a major project headed by Hohai University. Laboratory studies at UoA are presented, namely the effects of monopile vibration on scour depth, with and without riprap protection. The experiments are being done in the 2400 mm flume under clear-water and live-bed conditions, for a range of vibration amplitudes and frequencies. Results to date show that vibration amplitude leads to deeper scour. The riprap protection experiments show that larger riprap is more effective as a countermeasure, as expected. An extensive, current (at the time of writing) UoA laboratory program of scour due to superstructure submergence (‘pressure scour’ at bridges) is presented. The results are used to show the effects of the independent parameters (flow intensity, superstructure geometry and superstructure submergence) on scour depth under clear-water and live-bed conditions. Laboratory data for scour downstream from sluice gates are presented and analyzed to derive a simple design methodology. The dataset comprises previous UoA experiments and data from other studies, but are dated. In the authors opinion, new experimental studies of this important topic are warranted. Young researchers are encouraged to consider this topic.
Year: 2023