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3.3 Sand Investigations

3.3.1 Choice of Sand: Fluidising Properties, Availability and Health Risks

The sand grains for marine seabeds are assumed to most likely be nearly spherical if they are fine and had a chance to be rubbed against each other to create more rounded surface; resulting on a favourable void fraction.


It would therefore be ideal to use very fine sand, since it is both better for fluidisation and in relation to the model anchor leg that is a lot smaller than the actual anchor would be. Sand grain sizes were categorised in 1922 by Wentworth, C K, seen in Table 1, where silica sand is between 0.1-0.5 mm [Bri09]20. Silica sand is industrial and can therefore be found in various sizes depending on use.
Table 1 The canonical definition of sediment grain size from [Wen22]21

Very small particles of sand may enhance health risks such as silicosis (lung disease). The investigation of purchasing smallest possible grained sand led to researching silica flour, which is very fine silica sand. It ranges from 3 to 10 m in particle size [Dav08]22. It was then discovered that there is definite risk of silicosis present up to 5 m diameter particles and health risk can occur up to 10 m [Par11]23. Silica flour was therefore ruled out completely.


Fine sand is more difficult to find, especially when the grain size must to be known. A small amount of sharp sand, which is used for building, was therefore experimented with to see if this could be used for the anchor leg.



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