Sanaz Sayevand - Department of civil engineering, University of Hormozgan, Bandar abbas, Iran
Masoud Dehghani - Assistant professor,Department of civil engineering, University of Hormozgan, Bandar abbas, Iran

Dispersive clay soils collapse or disperse to form dissolved slurry when in contact with water. These soilsare highly prone to erosion often leading to tunnel and gully erosion. Unlike other forms of erosion,dispersion and tunnel erosion result from an imbalance in soil chemistry. Dispersion of soil occurs whenit is wetted and the clay particles are forced apart. Thus dispersive soils erode under small seepagevelocity leading to problems of stability of earth and earth retaining structures. The extent of dispersiondepends on mineralogy and clay chemistry as well as the dissolved salts of the pore fluid. Soil dispersivityis mainly due to the presence of exchangeable sodium present in the structure. The attractive forces areless than the repulsive forces under saturated conditions and this will help the particle to segregate andto move in suspension. Many structures are built, on and through clay soils, because of their lowpermeability. In the past dispersive clay soils were not recognized, and failure of several structuresoccurred before dispersive action was identified. This article presents description of characteristics andproblems of dispersive clay soils, tests for identifying and approaches for minimizing erosion risk indispersive soil

dispersive Soil, Sodium, piping, Chemical test, Physical test