A thesis submitted in partial fulfillment of the requirements for the degree of Master of Science, School of Engineering and Technology

Thesis (M. Sc.) - Asian Institute of Technology, 1982

Tests on the physical, chemical and mineralogical properties on the soils from 3 selected sites of dispersive soils and 1 selected site of nondispersive soil are carried out in the field and laboratory during this study. In order: to find out the relationship between clay contents and dispensability of the soil, some specimens are artificially mixed with a certain amount of clay in the laboratory and tested by means of pinhole tests. The artificial soils are dispersed in pinhole tests regardless of its clay content. For the relationship between the dispersity and a water content and/or a density of the specimen on natural soils, pinhole tests are also carried out at a different water content and different tamps per layer. Natural soils are dispersed in pinhole tests regardless of their water content and a number of tamps per layer. Chemical properties on the soil saturation extract and reservoir water are also determined by means of sodium adsorption ratio(SAR), exchangeable sodium percentage(ESP) and pH. The dispersive soils in the region have ranges of 1.8-6.7 SAR, 1.4-7.9 ESP and 5.4-9.0 pH, while a nondispersive soil has only 0.5 SAR, no ESP and 4.3 pH. The main minerals of the clay fraction in the soil are montmorillonite, kaolinite and illite which are analyzed by the X-ray diffraction method. The dispersive soils in this region have somewhat higher SAR, ESP and pH value chemically, and higher content of a montmorillonite mineralogically than those of the nondispersive soil. The dispersive soil area has distinct features, i.e., a pseudocarps and cloudy water which are good indicators of the dispersive soil area in the field.