Three testing procedures were developed in this research to allow expeditious characterization of soil unsaturated flow properties using steady state centrifuge methods. The first testing procedure, referred to as the “instrumented” procedure, focuses on using in-flight measurement of the suction and volumetric water content of soil samples under centrifugation. The measurements are used to calculate the soil water retention curve and hydraulic conductivity function (K-function) of soil samples. A good agreement was found between results determined using the “instrumented” procedure and standard testing methods. Several possible sources of inaccuracy were determined with the “instrumented” procedure. The void ratio, the changes of which were not measured, was found to decrease during centrifugation and the lower boundary condition, which was not accounted for in the evaluation, was found to affect a large portion of the sample. In order to improve the accuracy of results, two additional testing procedures were developed that accounted for these issues and incorporated the void ratio of the soil as an additional variable. The first additional procedure was used to measure the soil water retention surface (SWRS) of soil samples while the second was used to measure the unsaturated hydraulic conductivity surface (K-surface) of soil samples. Both new procedures, referred to as the “hydrostatic” and “imposed flow” procedures, were used to characterize the unsaturated flow properties of a low plasticity clay (“RMA” soil). The unsaturated flow characteristics of the RMA soil were evaluated for a wide range of void ratio and three compaction moisture conditions. As a result, the effects of void ratio and compaction moisture content on the unsaturated flow characteristics could be determined for the RMA soil. The compaction water content was shown to have significant effects on both the retention behavior and the unsaturated hydraulic conductivity of the RMA soil. In general, increases in compaction water content resulted in a decrease of large pore sizes in the soil, resulting in higher water retention and lower unsaturated hydraulic conductivity. The void ratio was found to have comparatively lesser, but still significant, effects on both retention and conductivity characteristics. Specifically, decreases in void ratio were shown to reduce the unsaturated hydraulic conductivity. In addition, decreases in void ratio were shown to result in either increases or decreases on the soil water retention, depending on the level of suction in the soil. A good agreement was found between results obtained using standard methods and those from the hydrostatic and imposed flow procedures. Accordingly, steady state centrifuge methods were ultimately found to provide a both expeditious and accurate method for characterizing the unsaturated flow properties of soil. / text

In this study, I develop a Gaussian Closure method to simulate steady state unsaturated flow in randomly heterogeneous soils. I predict pressure heads and fluxes and evaluate uncertainties associated with these predictions, without resorting to Monte Carlo simulation, upscaling, or linearization of the governing flow equations and the constitutive relationship between unsaturated hydraulic conductivity and pressure head. Upon treating dimensionless pressure head as a multivariate Gaussian function in the manner of Amir and Neuman [2001], I obtain a closed system of coupled non-linear differential equations for the first and second moments of pressure head and flux for both spatially uncorrelated Y (log saturated hydraulic conductivity) and spatially correlated Y. Computational examples for unsaturated flow in a vertical plane, subject to deterministic forcing terms including a point source, show a good agreement between my Gaussian closure solution and a more general Monte Carlo solution. The computational examples include a uniform domain, eight subdomains, spatially uncorrelated non-uniform Y cases, spatially correlated Y cases, and conditional Y cases. Though the computational examples treat the random pore size parameter a as being uniform across the entire flow domain, I show theoretically that the Gaussian closure method could apply to spatially variable a statistics.

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.

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.

Thesis (Ph. D.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 147-165).

Thesis (Ph.D.)--University of Delaware, 2008. / Principal faculty advisor: Yan Jin, Dept. of Plant & Soil Sciences. Includes bibliographical references.

Thesis (Ph. D.)--University of Chicago, 1933. / Lithoprinted. "Private edition, distributed by the University of Chicago libraries, Chicago, Illinois." eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Chicago, 1932. / Lithoprinted. "Private edition, distributed by the University of Chicago libraries, Chicago, Illinois." Description based on print version record. Bibliographical foot-notes.

Nitroxides are intermediates in the accepted reaction mechanisms of the antioxidant activity of diarylamines and hindered alkyl amines. The parent amines are used as additives to preserve synthetic and natural hydrocarbon-based materials from oxidative degradation. New methodology which enables monitoring of hydrocarbon autoxidations at low rates of radical generation has revealed that diarylnitroxides and hindered nitroxides are far better inhibitors of unsaturated hydrocarbon autoxidation than their precursor amines, implying intervention of a previously overlooked mechanism. Experimental and computational investigations suggest that the nitroxides catalyze the cross-dismutation of alkylperoxyl and hydroperoxyl radicals to yield a hydroperoxide and O2, thereby halting the autoxidation chain reaction. The hydroperoxyl radicals – key players in hydrocarbon combustion, but essentially unknown in autoxidation – are proposed to derive from a tunneling-enhanced intramolecular (1,4)- hydrogen-atom transfer/elimination sequence from oxygenated radical addition intermediates. These insights suggest that nitroxides are preferred additives for the protection of unsaturated hydrocarbonbased materials from autoxidation since they exhibit catalytic activity under conditions where their precursor amines are less effective and/or inefficiently converted to nitroxides in situ. Polyunsaturated fatty acids (PUFAs) are highly autoxidizable lipids that are integral structural components of biological membranes as well as substrates for enzymes the produce inflammatory mediators implicated in a host of degenerative diseases. In particular, the interactions between these substrates and their respective native enzymes are hotly pursued since elucidation of the underlying mechanisms could lead to the discovery of better small molecule inhibitors for the ailments to which they contribute. In the past decade, an additional mode of cellular degeneration has been unveiled in the process of ferroptosis whose hallmark includes a sharp increase in the cellular pool of PUFA derived hydroperoxides. As a result, there is further incentive to uncover all mechanisms by which these inflammatory precursors are developed. Herein, progress toward the synthesis of fluorinated PUFAs is presented. These are proposed to be useful to probe the interactions of PUFAs with lipoxygenase enzymes, which metabolize polyunsaturated fatty acids to their hydroperoxide derivatives.

Yes / Tailing dams are commonly used to safely store tailings without damaging the environment. Sand tailings (also called Sediment tailings) usually have a high water content and hence undergo consolidation during their placement. As the sediment tailings are usually placed above the ground water level, the degree of saturation and permeability of the sediment tailing is associated with the unsaturated condition due to the presence of negative pore-water pressure or suction. Current practices normally focus on the analyses saturated conditions. However, this consolidation process requires the flow of water between saturated and unsaturated zones to be considered. The objective of this study is to investigate the stability and consolidation of sediment tailings for the construction of road pillars considering the water flow between saturated and unsaturated zones. The scope of this study includes the unsaturated laboratory testing of sediments and numerical analyses of the road pillar. The results show that the analyses based on saturated conditions overestimate the time required to achieve a 90% degree of consolidation. The incorporation of the unsaturated soil properties is able to optimize the design of slopes for road pillars into steeper slope angles.