A geotextile is a planar permeable polymeric textile material used in contact with soil, rock or any other material. During the past 15 years, the use of geotextiles in environmental, geotechnical, and transportation engineering and related construction activities has been phenomenal. It is estimated that the North American geotextile industry has grown to exceed 1.6 billion dollars annually at an annual growth rate of 20 percent. The primary design characteristics of geotextiles are soil separation, soil reinforcement, filtration, and drainage. Many design applications have geotextiles placed above the groundwater table where soil and geotextile pores are filled with water and air. Thus, unsaturated fluid flow theory flow will dominate. Present design methods assume geotextile pores are only filled with water and saturated flow theory is valid. If geotextiles are to be installed in unsaturated soil, an understanding of fluid flow through unsaturated geotextile is essential. Presently, unsaturated data for geotextiles are not available in the literature. The proposed projects will provide theoretical and practical insights into how fluids flow through geotextiles; methods to measure geotextiles unsaturated parameters; and, unsaturated characteristic data sets for geotextiles. These data are required to perform design analysis. The research will consist of a laboratory program with two main themes. The first is to develop methods to measure unsaturated geotextile parameters and the second is to determine the impact geotextiles have on fluid flow in unsaturated soil. These themes will be addressed in three research projects: 1) measurement of characteristic curves of geotextiles, 2) measurement of hydraulic conductivity of unsaturated geotextiles, and 3) centrifuge soil column experiments.  It is anticipated that this research will advance the theory of fluid flow through geotextiles and present findings that will aid a practitioner in designing better soil structures.

The research team for this project consists of Dr. Knight, a faculty member in the Department of Civil Engineering at the University of Waterloo and MASc. candidates. Graduate students and the purchase of specialized testing equipment are funded in part by NSERC and a research award received from the University of Waterloo.