Compaction and water retention characteristics of Champlain sea clay

Several engineering structures for geotechnical engineering applications are constructed using compacted fine-grained soils (i.e., dams, road embankments, pavements, canals, and waste containment structures such as soil covers and liners). The compacted fine-grained soils are typically in a state of unsaturated condition and plastic in nature. There is a growing interest in recent years to apply the mechanics of unsaturated soils in the design of geotechnical structures constructed with compacted fine-grained soils. The soil-water retention curve (SWRC) is being used as a key tool in extending the mechanics of unsaturated soils into engineering practice. Conventionally, SWRC is determined in the laboratory without taking account the volume changes with respect to soil suction. The water retention characteristics of plastic soils depend on the pore-size distribution, compressibility characteristics and the volume change behavior. For this reason, the conventional procedures that are used in the measurement of the SWRC may not provide reliable information. Therefore, the engineering behavior of compacted fine-grained soils cannot be reliably estimated or predicted if the volume change behavior with respect to suction is not considered while measuring the water retention curves for compacted fine-grained soils. In this thesis, a comprehensive experimental program is undertaken to determine the water retention characteristics of a local plastic soil, Champlain sea clay. This soil is commonly used in the construction of several structures in Ottawa and Quebec region. The SWRCs of Champlain sea clay were measured on specimens that were statically or dynamically compacted at different water contents and densities using different compaction energies. The suction measurements of the individually compacted specimens were determined using axis-translation technique and thermocouple psychrometers. The volume changes of the specimens were measured at each value of suction while determining the SWRC. In light of the experimental results, the parameters that influence the SWRC behavior such as compaction type (i.e., static or dynamic) and effort, initial compaction water content and void ratio on the water retention behavior of compacted fine-grained soils were investigated. In addition, a database of 16 compacted plastic soils with measured SWRCs and their conventional properties from the published literature was summarized. Relationships between the parameters of the SWRC, namely, the rate of desorption and the conventional soil properties were studied using the results of the present experimental program and the information from the database. This study shows that liquid limit coupled with clay fraction can be a useful tool to correlate with the rate of desorption for compacted soils. Based on this information, a new technique is proposed for the estimation of the entire SWRC of compacted fine-grained soils following the drying path. The required information for using this technique includes one point measurement of suction versus water content in the suction range of 0-500 kPa, along with data on the liquid limit and the clay fraction. The proposed technique provides good comparison between the measured and estimated SWRCs for the data studied in this research program. This technique can be used in the preliminary design stages of a project when detailed information about the soil is no available. In addition a state-of-art literature review on the devices presently available for the measurement of soil suction is summarized