Dispersivity is the tendency of some clayey or cohesive soils exposed to saturation by surface or groundwater to separate into individual particles instead of forming small clumps or aggregates of particles known as flocs.
Dispersivity results in poor behavior of compacted soil embankments, particularly those that impound water, and can lead to failure caused by erosion associated with soil piping, internal erosion into cracks, fissures, and joints, or other macro-scale openings, or migration of soil fines into pore space between larger soil grains, such as gravel or cobbles. Dispersive soils have monovalent exchangeable cations, predominantly sodium, Na+, in the pore water, whereas nondispersive soils have divalent cations (calcium, Ca2+; magnesium, Mg2+; sodium, Na2+; potassium, K2+). Dispersive soils can be associated with weathering products derived from residual soils formed on marine shale, alluvial deposits transported from drainage basins containing marine...
- ASTM (2011) Standard test method for dispersive characteristics of clay soil by Double Hydrometer. American Society for Testing and Materials Test D4221-11. http://www.astm.org/Standards/D4221.htm. Accessed 30 Apr 2016
- ASTM (2013a) Standard test methods for identification and classification of dispersive clay soils by the Pinhole Test. American Society for Testing and Materials Test D4647/D4647M-13. http://www.astm.org/Standards/D4647.htm. Accessed 30 Apr 2016
- ASTM (2013b) Standard test methods for determining dispersive characteristics of clayey soils by the Crumb Test. American Society for Testing and Materials Test D6572-13e2. http://www.astm.org/Standards/D6572.htm. Accessed 30 Apr 2016