Understanding of fundamental erosion characteristics of seabed sediments on which pipelines and other structures are found is critical for the design of these facilities. The erosion threshold condition of cohesive sediments is not well understood because of the complexity and variability of natural sediments. Most of the existing methods for evaluating the erosion behaviours of seabed sediment are often only applicable to the certain particular sediment types and test conditions. There appears to be a need for more research efforts in this area. In the present research, the threshold of motion of four moderately consolidated sand/clay mixtures and scores of field samples found in North West Shelf of Australia was tested in unidirectional currents, wave-induced oscillatory flow and combined waves and currents using the mini O-tube testing facility. As for unidirectional steady currents, the threshold shear stress τcr was correlated with some basic soil properties, e.g. particle size d50, mud content Pm, plasticity index PI and bulk density ρd. It was found that τcr positively correlated with mud content Pm, plasticity PI and bulk density ρd for field samples. The relationship between dimensionless threshold shear stress θcr and dimensionless median particle size D* was established as an algebraic expression for the present test results.
|Qualification||Doctor of Philosophy|
|Publication status||Unpublished - 2012|