Prediction of pile scour characteristics under currents considering seabed macroscopic and microscopic parameters

The geomechanical properties of the seabed have a vital influence on scouring around the pile, which are ignored by most of the studies on scour theory, resulting in large errors in the prediction of scour. In this paper, a series of experiments of scour in the sandy seabed with different seabed parameters are carried out. The critical starting shear stress of the seabed increases with increasing relative seabed density, which in turn reduces the scour depth. A new formula for calculating the scour depth considering the geomechanical parameters of the seabed is proposed, and the error of the scour depth calculation formula is less than 20%. According to the formula, the influence of the relative densities on the scour depth is found to be related to the ratio of the current and the critical motion shear stress of sediments. The paper found that the friction coefficient (microscopic parameter) and relative densities (macroscopic parameter) of the particles are the main parameters affecting the scour depth of the seabed. Therefore, in engineering, the design of scour protection can be carried out by the method of compaction plus grouting. The work of this paper can used in practice to predict the scour depth of offshore foundations.