The 12th International Conference on Scour and Erosion (ICSE 2025)

Scour development around monopile foundations in non-cohesive single layer soils is relatively well studied. However, the fundamental scour mechanisms in layered soils are not yet fully understood. Existing literature on this topic indicates layered soils present a very different behavior from the single layer case. In this study scour tests on a monopile physical model, built on a 1:100 geometrical scale following Froude similitude, were carried out with different non-cohesive layered soils under the clear-water regime. The results showed that: (1) when compared with a soil composed of a single fine sand layer, layered soils with an overlaying or underlaying wide graded fine sand may present a smaller equilibrium scour depth, (2) fine sand soils with overlaying coarser sand layer may present smaller scour depths than a coarse sand with overlaying fine sand, (3) scour development in layered soils can show similar behavior as often reported for mixed sands, particularly after 25% of the time-scale to reach equilibrium.