Southcote, Berkshire of chalk, with geological surveys also finding flint samples. A map produced by the Geological Survey of Great Britain in 1860 identifies the area as being predominantly Plastic Clay (now known as the Lambeth Group) and chalk north of the river, with flint and gravel samples typical of the Bagshot Formation south of the Kennet. More specifically, the 2000 survey showed different types of gravel, including Winter Hill (variably clayey and sandy), Lynch Hill (sand and gravel with lenses of silt, clay or peat), and head (a polymict deposit usually formed by periglacial solifluction or gelifluction). The survey also identified
Dilatancy (granular material) 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 dense granular material is to dilate (expand in volume) as it is sheared. This occurs because the grains in a compacted state are interlocking and therefore do not have the freedom to move around one another. When stressed, a lever motion occurs between neighboring grains, which produces a bulk expansion of the material.