This paper deals with dispersive erosion of soil in Sistan plain in the eastern part of Iran. This area is a vast flat plain, which lies upon Hirmand (Helmand) River Delta. Zabol city, the biggest city of the Sistan area, is located nearly in the center of the plain. The transportation of huge amounts of sediments in the past periods has decreased the depth of Hamun lake, close to Zabol city. This phenomenon has currently caused a lower elevation for Zabol city than some parts of the Hamun lake. Therefore, a large embankment has been constructed around the city to protect it against Hirmand river floods. One of the problems which the city has confronted during the recent years is the erosion of the embankment. The embankment destruction has caused huge damages to the urban structures. Sistan plain is covered by fine-grained sediments such as silt and clay, therefore, there is a probability of embankment demolition in some parts due to dispersive erosion. This study was carried out to find any possible relationship between dispersivity of soil and embankment erosion in the region. Thus, 20 samples from different locations of the plain have been tested in various ways with regard to dispersivity.

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