Thesis (Ph. D.)--University of Wisconsin, 1964. / Typescript. Vita. Includes bibliographical references.

published_or_final_version / Botany / Doctoral / Doctor of Philosophy

Geotextiles are often incorporated in engineered structures—including landfill liners and covers, earthen dams, retaining walls, and roads—to perform the separation, filtration, and/or drainage functions. Under unsaturated conditions typical of such structures, a capillary break may form at the interface between soil and geotextile. If the break is unplanned, the resulting build-up of moisture may be detrimental to the structure. Conversely, properly designed geotextile capillary barriers have the potential for many positive applications. Design information, including a complete framework for analysis and an accepted laboratory characterization approach, is lacking. The primary objectives of this study were to investigate geotextile capillary barrier performance with a simple laboratory model and propose a framework for complete analysis of a geotextile capillary barrier life cycle. Soil columns were designed to allow the formation and breakthrough of a geotextile capillary barrier to be observed. Materials used in the columns were obtained from a capillary barrier system currently under construction at the Rocky Mountain Arsenal in Denver, CO. Hydraulic characterization of the soil and geotextile were performed in the lab. Eleven column tests were completed for this study—soil compaction and applied flow rate were varied to investigate their effect on capillary barrier response. Analysis was approached within a proposed framework covering each stage of a capillary barrier life cycle. While there was considerable scatter in the test results, important insight was gained. The geotextile capillary barrier performed consistently. Conditions near the interface at breakthrough were similar between tests, regardless of soil compaction or applied flow rate, and were predicted adequately with the laboratory characterization. Storage capacity of the capillary barrier decreased with increasing relative compaction. A framework for analysis, from which the entire capillary barrier response may be modeled, was developed. Application of this model allowed for identification of weaknesses and recommendations for future work. / text

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Unsaturated swelling clays are used in engineered barriers for waste disposal facilities due to their self-sealing ability and low hydraulic conductivity. The characterization of unsaturated clay behaviour is required for design of these barriers. In recent years, several small-scale laboratory and full-scale field tests have been conducted to characterize the mechanical and hydraulic behaviour of the unsaturated swelling clay. This focus of the present study is towards the development of constitutive models to simulate hydraulic and mechanical behaviour of precompacted unsaturated swelling clay, called the bentonite-sand buffer (BSB) material. Development, calibration, implementation, and application of the proposed constitutive models form the scope of the study. The results of laboratory triaxial tests with controlled suction and suction measurements are used to calibrate the constitutive models presented. An algorithm, called the PEM (Parameter Evaluation Method), which is useful to estimate constitutive model parameters and evaluate the performance of constitutive models is proposed. This algorithm has been used to estimate the parameters of two elasto-plastic constitutive models (i.e., the BBM (Alonso et al. 1990) and the BGM (Blatz and Graham 2003)) based on the laboratory tests results on the BSB material. New 3-dimensional porosity-dependent permeability model (kwn) and water retention surface (WRS) are developed in this study. The mathematical formulations of these models using parameters calibrated with laboratory tests conducted on the BSB material are provided. Implementation algorithms of the BBM, the BGM, the kwn, and the WRS in 2-phase flow hydraulic-mechanical (H-M) analysis using a 2D-finite difference method are also provided . Three combinations of hydraulic and mechanical constitutive models (linear elastic model, BGM, vanGenuchten (1980) and kwn models) are used to simulate small-scale infiltration processes in the BSB material. Two types of tests, constant volume (CV) and constant mean stress (CMS) tests are simulated using 2D-finite difference H-M analysis. The full-scale isothermal test (ITT) of AECL is modelled using 3 combinations of H-M constitutive models. The ITT experiment comprises of buffer, rock, and concrete materials. The selected combinations of H-M constitutive models are used in three types of analyses: buffer-only (BO); buffer-rock with 20x30m domain (BR); and time-dependent boundary conditions (BCt). The results of the study show that the applications of the elasto-plastic mechanical constitutive models and porosity-dependent permeability (kwn) model are improvements over existing constitutive models to model this class of problem. The rock properties and applied boundary conditions are significant in modelling the ITT experiment. The application of the time-dependent boundary condition can reduce the uncertainty of the rock properties and boundary conditions within the rock, so that it improves the model ability to simulate the hydraulic-mechanical behaviour of unsaturated swelling clay. / October 2007

Oligomers of hard and soft segments of unsaturated polyesters were synthesized in two steps. For the hard segment, isophthalic acid was reacted with 1,2-propanediol first, then maleic anhydride was added for further esterification. For the soft segment, diethylene glycol was used to replace 1,2-propanediol. In the previous study, the excess amount of glycol was 20% in weight. In this study, glycol was 10 and 5 wt% in excess, respectively. Decreasing the excess amount of glycol from 20 to 5 wt%, the number average molecular weight of both hard and soft segments increased about 30-40% from 1000 g/mol, and the degree of isomerization of maleic acid changed from 40.5 to 57.3% for the oligomers of the soft segment. The hard and soft segments synthesized in this study were blended in weight ratios from 0 to 100 % in an interval of 20 %, and then cured with styrene for further mechanical testing. The micro-tensile strength of cured soft and hard segments increased 1.3 and 8 times, respectively, in this study compared with that of specimens prepared under the condition of 20 wt% in excess of glycol. Therefore, the criteria of inhibitors can also be achieved by varying the excess amount of glycols. To evaluate the nitroglycerine migration and the erosion rate, only two (60% hard segment and 40% soft segment) of the formulas which passed the criteria of mechanical properties were investigated by replacing lithophone with magnesium hydroxide. In the case of 10 wt% in excess of glycol, the migration of nitroglycerine at infinite time (M

The shear strength behavior of unsaturated soils is a complex phenomenon. The major factors that lead to the complex behavior are grain size, natural alteration in status of moisture and associated capillary potential. The need for research is felt to understand the various aspects associated with development of shear strength of unsaturated soils. The research is conducted to obtain the most economical and reliable design solutions. The magnitude of positive pore water pressure developed in saturated soil reduces the shear strength to a great extent. The tensile pore water pressure in the capillary meniscus developed around the soil grain contacts, on the contrary, enhances the factor of safety in the case of unsaturated soil mass. In this research, the shear strength of unsaturated soil is studied for a range of saturation based on the parametric study. The principle of effective stress has proven to be the basis for understanding the shear strength of saturated soil mass and it has provided an explanation for the geotechnical engineering problems. The thesis presents a study on the shear strength of the soil specimen using the direct shear apparatus. The previous research was mainly directed towards evaluation of shear strength under controlled soil suction, by modifying the apparatus. A simple technique is put forward in this research by making use of the conventional direct shear apparatus for testing the unsaturated soil. The suction stress was induced in the soil specimen and the shear strength was evaluated. The soil water characteristic curve has been used in the research to determine the tensile pore water pressure. Hypothesis based on parametric study has been put forward to present a technique to determine the unsaturated soil shear strength parameter in the thesis.

Thesis (Ph. D.)--Faculty of Agriculture, University of Sydney, 1998. / Bibliography: leaves 184-218. Also available in print form.

Thesis--Ph. D., University of Hong Kong. / Typewritten.