Asperity (Geotechnical engineering)

In Geotechnical engineering the term asperity is mostly used for unevenness (roughness) of the surface of a discontinuity, grain, or particle with heights in the range from approximately 0.1 mm to many decimetre. Smaller unevenness is normally considered to be a material property (often denoted by material friction or basic material friction).

An often used definition for asperities in geotechnical engineering:
Unevenness of a surface are asperities if these cause dilation if two blocks with in between a discontinuity with matching asperities on the two opposing surfaces (i.e. a fitting discontinuity) move relative to each other, under low stress levels that do not cause breaking of the asperities.

Materials science recognizes asperities ranging from the sub-visual (normally less than 0.1 mm) to the atomic scale.

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