A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Civil Engineering

Thesis (M.Eng.) - Asian Institute of Technology

Drained triaxial tests were conducted in a Triaxial apparatus, specially designed for unsaturated soils, in order to analyze the shear behavior of Khon Kaen soils. Three tests were carried out with constant suction values of 0, 50, 100 kPa and three with varying suction values while testing. The three different changing values are 200 --+ 100 --+ 0, 200 --+ 50 --+ 0, 200 --+ 50 --+ 200 kPa. All the tests were performed for both loose and dense specimens with the same confining pressure of 100 kPa. The test results presented here, give a feeling of effect of suction on shear strength, volumetric behavior and drainage characteristics in both states of soil. As the experiments conducted with the actual field conditions, the results obtained may be a good match with the real situation. In addition, they can be clearly explained by Kohgo's elastoplatic model. Loose specimens show strain hardening behavior where as dense specimens show strain softening behavior. Increase in suction increases the strength of the soil regardless of its state. In loose state of soil, change in volume decreases with the increase in suction. But in dense state, the higher the suction the larger the shear strength hence dilatancy is more. Amount of drainage increases with the suction. But in lower suction values drainage is very much less and perhaps water goes into the soil.