Dilatancy (granular material) / internal erosion. The use of appropriate filters is critical to managing these materials; I like a #4 sized clear gravel / coarse-grained sand as a commercial aggregate which is generally readily available. Some non- woven filter fabrics are also suitable. As with all filters, D15 and D50 compatibility criteria should be checked. Dilatancy (granular material) Dilatancy is the volume change observed in granular materials when they are subjected to shear deformations. This effect was first described scientifically by Osborne Reynolds in 1885/1886 and is also known as Reynolds dilatancy. Unlike most other solid materials, the tendency of a compacted
Silt out zero visibility. Always using guidelines during penetration dives is an important safety measure as it helps divers find their way out. Surface supplied divers are generally at less risk from silt out as they are connected to the surface by an umbilical and can not get lost, but they may become disorientated, and unable to work effectively. It is also more likely for them to have an umbilical snag in bad visibility, and if assistance is required from the stand-by diver, this is more difficult in a silt out. A severe silt out will make the video cameras on a