Since 1970, a number of earth dams in northeast Thailand have suffered serious tunnel and surface erosion from rainfall, and several have failed during the first reservoir filling. The behavior is typical of dams containing dispersive clay. This paper describes the testing program undertaken to evaluate the embankment and foundation materials, and discusses the results. Laboratory testing included chemical analysis of the saturation extract, the U.S. Soil Conservation Service dispersion test and X-ray diffraction. Some correlation was found between the test results and the extent of the damage to various embankments.

In the search for nondispersive soil, the Emerson Crumb Test has been used for initial indications in the field, as well as being used, with modifications, in the laboratory.

A description is given of measures being adopted to repair two damaged dams with dispersive soil where nondispersive soil is not available. The repairs involve the replacement of eroded material and the prevention of any serious future damage to existing and new materials by physical and chemical treatments.