SCARCOST

Scour around Offshore Structures (SCARCOST)

Scour around a Group of Piles

This EU MAST funded project was to study the potential risk for scour in the vicinity of coastal structures, and to prepare and disseminate practical guidelines, to be developed from the research programme and also taking into account all “state-of-the-art” knowledge.

The project was divided into two sub-projects. In the first sub-project, attention was primarily concentrated on the water column with flow processes and the resulting scour with some input from sediment parameters. In the second sub-project, processes associated with the sediment are the major concern. The first sub-project basically consists of the following research themes: 1) Flow and scour processes around vertical cylinders, simulating individual piles or individual large cylinders (such as platform legs, or bridge piers), or pile groups; 2) Flow and scour processes around breakwaters (such as detached breakwaters and submerged breakwaters); and 3) The effect of turbulence on sediment transport/scour where the incorporation in the sediment transport/scour calculations of the turbulence generated by the structure itself is the main focus of the study. Techniques to be used in all the three research themes are mainly the laboratory experiments, while the third theme involves also some theoretical study.

The second sub-project, on the other hand, had the following research themes: 1) Wave-generated pore pressure and scour around breakwater element (a field study where the wave generated pore pressure and its association with scour around a cylindrical shaped breakwater element is the major concern of the investigation); 2) Non-linear modelling of wave-induced pore pressure with the purpose of studying the liquefaction initiation mechanisms in relation to the loss of bearing capacity for small objects on the seabed (such as armour blocks), and also in relation to both the general scour and the local scour processes; 3) Wave bottom pressures and wave kinematics in the surf zone, two important flow processes with regard to the generation of pore pressures in the surf zone; 4) Sediment transport/scour by accounting for the effect of momentary liquefaction; 5) Penetration of blocks into the seabed (in the absence of filters) due to the reduction of soil stiffness caused by the building up of pore pressure under wave action; and finally 6) Cyclic stiffness of loose sand at small confining stresses. The first theme in this sub-project involves a field study, while the other themes involve theoretical studies, and laboratory investigations.

My Role: CI

Publications

• Nicholson, J. and O’Connor, B.A. (1998), Effect of enhanced turbulence on suspended sediment transport due to a current and waves. Report No.CE/04/98, Department of Civil Engineering, The University of Liverpool, 1998.
• Rose, C.P., Li, M. and O’Connor, B.A. (2000), Computational experiments to examine the effect of grid generated turbulence on velocity and shear stress characteristics in a steady flow. University of Liverpool, Dept. of Civil Engineering, Report No. CE/02/00, 15 pp.