Suction and compressibility characteristics of an unsaturated till

Most geotechnical projects involving compacted soils are typically in a state of unsaturated condition. However, compressibility characteristics of such soils are typically estimated extending the principles that are commonly used for saturated soils. The compressibility and settlement characteristics of compacted soils are influenced by several parameters such as the applied loading, water content, compaction energy and soil structure. All the above parameters are in turn influenced by matric suction, which is one of the stress state variables for interpreting the engineering behavior of unsaturated soils. The focus of the research presented in this thesis is to understand the role of matric suction on the compressibility characteristics of a typical glacial till from Indian Head till, Saskatchewan. As a part of this thesis, the current techniques available in the literature for estimating matric suction were reviewed and implemented with varying degrees of success. New and improved techniques are presented for determining the matric suction using both axis-translation and the contact filter paper techniques. Based on the experimental studies undertaken in this research program, an equation is presented for Indian Head till that relates compaction water content to matric suction.