A thesis submitted in partial fulfillment of the requirements for the Degree of master of Engineering of the Asian Institute of Technology, Bangkok, Thailand.

Thesis (M.Eng.) - Asian Institute of Technology, 1971

The bubbling pressure of a porous medium is defined as the capillary pressure at which the non-wetting fluid is first continuous through the medium. It is very important soil parameter in characterizing a partially saturated flow. The purpose of this thesis is to study the effects of pertinent soil parameters and fluid properties on the bubbling pressure. A capillary tube model analogy was employed to develop an equation representing the bubbling pressure as a function of soil parameters and properties of fluid. The soil parameters being con sidered were porosity, characteristic diameter of soil particle, and a coefficient which is a function of the pore size distribution index. The fluid properties were surface tension and specific weight. Experiments ~'7cre conducted to verify the theoretical equation and determine tile coefficient. The media \·rnre selected to hav-e wide ranges of texture, porosity, grain size distrioution and pore size distribution. The wetting fluid used was distilled water and non wetting fluid was air,