Effect of sediment supply on suction scour under a rock berm

Abstract

This paper presents a case study of sediment transport behaviour from between armor rocks in a rock berm placed on a fine sandy seabed model. The test was conducted in the Large O-tube facility at The University ofWestern Australia under steady current and combined irregular flow conditions (live bed). Suction removal of sediment from under the rocks has been identified as a mechanism that can lead to the sinkage of a berm by previous researchers. Suction removal was not observed in the reported tests. Instead the gaps between rocks were filled up gradually with sand. The main reason for this contrasting behaviour compared to previous studies was that there was sediment supply from upstream, thanks to the recirculating nature of the O-tube flume. This supply added sediment to the rock berm in excess of that which could be mobilised through suction scour. This result suggests that the influence of sediment supply should be considered to create improved physical modelling of suction scour, and to allow better design of rock berms for stability against sinking.