ABSTRACT
Dispersive soils are readily eroded because the clay particles deflocculate and detach from the clay surface. Clay dispersion is dependant on two main factors: the nature of the exchangeable cations on the clay surface and the presence of salts in the pore water. If the forces of repulsion due to the adjacent negatively charged clay surfaces overcome forces of attraction between the clay particles, the clay particles repel one another, deflocculate and go into suspension, even in still water. Dispersivity can not be identified using routine soil mechanics tests, but specialised physical and chemical tests have been devised to assess the potential dispersivity of a soil. However, since no single test can be used with complete certainty to identify dispersivity it is necessary to combine a number of the tests into a rating system, using a weighting system dependent upon the reliability of each test employed.
