This study is the second attempt to use the Basal Temperature of Snow (BTS) method to map permafrost in mountainous regions of northwestern Canada. It differs from the first study which took place in Wolf Creek in terms of (1) the methodology used to evaluate BTS, (2) the strategy used to avoid spatial autocorrelation in residuals, and (3) the climatic regions investigated. Two study areas, part of the Ruby Range (61° 12' N, 138° 19' W) and Haines Summit (59° 37' N, 136° 27' W) were selected for BTS sampling based on differing climatic conditions and previous knowledge of permafrost elevations from active rock glaciers. A total of 30 BTS measurements were made in the Ruby Range in the winter of 2006 and a total of 77 BTS values were obtained in the Haines Summit area during 2005 and 2006. From these results, modeled BTS surfaces were created using elevation and potential incoming solar radiation as independent variables in a multiple linear regression. At Haines Summit, potential incoming solar radiation was not significant in the model and thus was dropped. The surface of modeled BTS was then combined with a physical validation of permafrost presence completed during the late-summer of 2005 in a logistic regression. The modeled results produced permafrost probability maps for both study areas. Based on modeled results, permafrost underlies an estimated 282 km2 or 66% of the Ruby Range study area and 23--236 km 2 or 43--44% of the Haines Summit study area. An attempt was made to use the linear model derived in the Ruby Range at Haines Summit in order to examine the possibility of expanding predictions into new areas. Although the results produced similar total amounts of permafrost, the spatial distribution differed: permafrost probabilities were reduced at high elevations while lower elevation sites exhibited increased probabilities. The results of the model transfer illustrate the importance of the pit data in determining the total amount of permafrost, while knowledge of BTS ranges contributes to the spatial distribution of permafrost. With further study it is likely that generic models can be derived for areas of similar climate.

The research work of this thesis is motivated by a desire to render views of 3D environments in real-time on mobile devices. Considering the weak support for 3D hardware accelerations of mobile devices, it is hard to render geometry-based models at an interactive rate. The utilization of image-based rendering techniques in mobile devices is presented in this thesis. In order to have a systematical knowledge of image-based rendering, we briefly review different image-based rendering techniques. Although image-based rendering is advantageous to geometry-based rendering in certain circumstances, further tailoring is still required to immigrate it to mobile devices. This thesis presents a technique for running image-based rendering tasks on mobile devices. This technique comprises a lightweight rendering algorithm and a local cache management mechanism. Results have shown that the proposed algorithm requires less CPU cycles compared to other algorithms, and that the local buffer management mechanism is robust to communication errors.

<p> A transparent soil model of granular fused quartz is developed to study the mechanics of shallow foundations. Soil models, unreinforced and reinforced, prepared at relative densities 0.34 (loose) and 0.64 to 0.69 (medium dense) are tested using a rectangular footing (25 mm wide x 40 mm long) under strain-controlled loading. Digital Image Correlation is used to identify displacements of a seeded central plane parallel to footing width (<i>B</i>) and construct vector fields and contour plots. Fiber-reinforced soil model data analysis is inconclusive. For the unreinforced medium-dense soil, minimum and peak magnitude horizontal displacements occurred directly under the footing at the footing edges; whereas in the loose soil, peak magnitude horizontal displacement occurred directly under the footing. Vector and contour plots revealed that a medium dense soil gradually distributes smaller magnitude displacements over a broad area, in contradistinction to acute, highly localized displacements of larger magnitude in a loose soil.</p>

Material instabilities play an important role in many engineering problems because they trigger zones of highly localized straining, which often act as a precursor to failure. Classical continuum mechanics approach has been proven insufficient to study material instability problems which involve highly localized straining. Instead, an enhanced approach is required to describe strongly nonlinear behavior and local weakness of the material. In this research, high-gradient constitutive models have been developed to study the instability problems of materials, in particular of granular materials. In a high-gradient model, strain gradient and higher-order stress are incorporated in the constitutive equation as additional variables. Therefore, the high-gradient model is useful in describing highly localized straining. A strain gradient model is developed using the microstructural approach in elastic range as the basis and starting point of the research. The developed strain gradient model is implemented in the finite element formulation based on a modified variational principle. Several numerical examples are presented and compared with the results of the classical continuum models. To study material instability, the strain gradient model is extended to inelastic range. The von-Mises, Drucker-Prager and Cam-Clay strain gradient plasticity models have been developed. A simple shear test and a biaxial test are analyzed using the developed strain gradient plasticity model. The results demonstrate that the strain gradient model effectively removes the spurious mesh sensitivity of finite element simulations. The finite element solutions also show that the shear bandwidth is not only a function of material internal length but also of the distribution of weak spots. Two soil instability problems are analyzed using the strain gradient plasticity model. The results show that the traditional limit equilibrium methods could possibly overestimate the ultimate bearing capacity of the foundation. It is necessary to use the more realistic soil models to evaluate the performance of the foundation. Finally, a micromechanical strain gradient plasticity model is derived from the mobilization behavior of micro-scale local planes. The model is calibrated based on the experimental data. The model is capable to simulate stress strain curves including: pre-peak strain hardening, post-peak strain softening, dilatancy, critical state. Instability of boundary value problems is analyzed and the results are compared with other strain gradient models.

In the petroleum industry, accurate estimates of hydrocarbon reserve and its producibility are without a doubt among the most important issues. Quantitative estimates require the knowledge of three basic parameters of the rock formation: the porosity &phis;, the water saturation S w and the permeability k. Electrical conductivity is one of the most commonly made measurements used to deduce these quantities. Some empirical relationships used to make such estimates are quite well established and understood, however, many still lack a sound scientific foundation. Systematic laboratory investigation and theoretical understanding of the underlying petrophysics are much needed. This dissertation consists of three projects aimed at understanding both the surface conductivity observed in shaly sandstone, and the related phenomena of molecular adsorption on heterogeneous surfaces. In the first project, we carried out nitrogen adsorption experiments on three shale samples whose fractal dimensions had been previously characterized by small angle scattering (SANS). We found that analyzing the adsorption isotherm data according to the available theoretical predictions always resulted in D values that are lower than those obtained by SANS. The second project, a numerical simulation of adsorption on fractal surfaces, was designed to understand the origin of discrepancies revealed in the first project. We found that the interplay between van der Waals adsorption and capillary condensation always leads to a crossover between the two theoretical limits. The simulated isotherms exhibit the same general features we observed in our experimental data. The third project was aimed at understanding the surface conduction in porous media. We isolated the surface conductivity by growing water layers on the surface with water adsorption isotherm technique. Some of our results indicate that AC impedance measurement could let us determine the surface conductivity and separate it from that of the bulk, thereby more accurate estimates of oil saturation can be achieved in using the empirical Archie's relation. Our studies shed more light on the various aspects of the surface ionic conduction, including Debye - Hückle length, CPA phenomenon, and effects of saturation, cation species, temperature, and substrate.

This dissertation presents W-Band measurements of the copolar correlation co-efficient and Doppler spectrum taken from the University of Wyoming King Air research airplane. These measurements demonstrate the utility of making W-Band polarimetric and Doppler spectrum measurements from an airborne platform in investigations of cloud microphysical properties. Comparison of copolar correlation coefficient measurements with aircraft in situ probe measurements verifies that polarimetric measurements indicate phase transitions, and hydrometeor alignment in ice clouds. Melting layers in clouds were measured by the W-Band system on board the King Air during 1992 and 1994. Both measurements established the use of the linear depolarization ratio, LDR, to locate the melting layer using an airborne W-Band system. The measurement during 1994 allowed direct comparison of the magnitude of the copolar correlation coefficient with the values of LDR. The relation between the measurements corresponds with a predicted relationship between the two parameters for observation of particles exhibiting isotropy in the plane of polarization. Measurements of needle crystals at horizontal and vertical incidence provided further evidence that the copolar correlation coefficient values agreed with the expected response from hydrometeors possessing a preferred alignment for the side looking case, and hydrometeors without a preferred alignment for the vertical incidence case. Observation of significant specific differential phase at vertical incidence, the first reported at W-Band, corresponded to a significant increase in differential reflectivity overhead, which was most likely produced by hydrometeor alignment driven by cloud electrification. Comparison of the drop size distributions estimated using the Doppler spectra with those measured by the wingtip probes on the King Air reveals that the radar system is better suited under some liquid cloud conditions to provide microphysical measurements of the cloud or precipitation than the probes. The radiometric calibration of the radar system determines the accuracy of the drop size distribution estimate. The results presented here indicate that the procedure used to absolutely calibrate the W-Band radar system successfully characterized the reflectivity measurements to the extent required to obtain close correspondence between the radar and probe measurements of the drop size distribution.

A full-scale prototype integral bridge abutment was constructed at the University of Massachusetts Amherst as part of a project conducted for the Massachusetts Highway Department. Ten tests were then conducted during which the abutment was passively displaced into the backfill. The purpose of these tests was to determine the effect of foundation type, wingwall geometry, reloading, and backfill soil type on the lateral pressures generated following placement of the backfill and during the abutment movement. Individual tests were performed by placing and compacting the fill in lifts and then incrementally displacing the abutment into the fill. During this displacement, earth pressures at the abutment centerline, ‘quarterline,’ and wingwall centerline as well as the applied load and deflection of the abutment and wingwalls were measured. After a series of tests were performed with the abutment on a spread footing, the abutment was removed and piles were driven through precast holes in the footing. Two piles were instrumented with strain gages and inclinometers. The abutment was then replaced and the same types of tests were again performed. Results from testing indicated that during no test was the distribution or magnitude of lateral earth pressures similar to that predicted by classical theory. The use of an uncompacted sand zone directly behind the abutment face was found to reduce lateral earth pressures significantly. This zone was, however, found to compact after one cycle of reloading. Both wingwall geometry and foundation type were found to affect the lateral earth pressure magnitude and distribution. Equations were developed which predict the lateral earth pressure coefficient for any abutment deflection or point along the abutment height. Current design charts were also modified to account for the behavior observed during these tests.

A constitutive relationship is developed for granular materials from a micro-mechanical point of approach accounting for heterogeneity of deformation field, inter-particle sliding and packing structure change. The granular system is idealized to be composed of circular particles with same stiffness properties and inter-particle friction angle. The granular assembly supports the imposed load through resistance at inter-particle contacts. The deformation at inter-particle contact is represented by springs which connect particles at the inter-particle contact. With this simplified picture of the granular, the continuum variables such as stress and strain are defined for a particle (local or micro level) and for a collection of particles (overall or macro level). A definition of strain tensor which accounts for the particle rotation is introduced. A local stress-strain law is defined to describe the mechanical behavior of a particle interacting with its neighbors. The local stress-strain law is established by considering the following relationships: between the stress and contact force; and between the strain and relative displacement of the particles. The local stress-strain law is cast in terms of nominal stress increments in order to account for packing configuration change due to finite strains. Geometric non-linearity due to loss of existing contacts is included. A concept of over-shooting force is described which accounts for the effect of material nonlinearity due to inter-particle sliding and separation. The overall stress-strain law is defined for a representative volume of granular media. The representative volume of the granular material is taken to consist of a large number of particles such that it is considered to be equivalent to a point in a continuum media. The overall stress and strains are determined as volume averages of corresponding local quantities. A 'concentration' tensor is defined to relate the overall strain to the local strain. Using the 'concentration' tensor, and the definition of overall stress and strain as volume averages, the overall stiffness tensor is established. The overall stress-strain behavior is determined through a numerical effort. The stress-strain relationship developed in this study can reduce the discrete granular system to an equivalent continuum system which is mathematically and computationally more tractable. Example results are presented to show that the model captures all-the salient features features of mechanical behavior of granular materials such as: nonlinearity, elasto-plasticity, stress/strain path dependency, dilatancy-contractancy, failure and strain softening under post-peak loading.

Over the last four years Potgietersrust Platinums (PPRust) has successfully implemented new geotechnical strategy and tactics to reduce risk, improving safety but also maximising profitability. A large database of core logging, face mapping and rock testing has been assembled and used in the slope design process. The data has also been used for optimising blast designs on a daily basis through the use of a geotechnical block model. This greatly improves blast fragmentation and therefore loading and milling efficiencies. Slope management includes a limit blasting programme, daily visual inspections, and state-of-the-art slope monitoring equipment, namely GroundProbe radar, Riegl lasers and GeoMoS automated prism monitoring. Slope optimisation incorporates all the field data, operational controls, cost of failure, full economic analysis of various slope angles and fault tree analysis. Savings on waste stripping of hundreds of millions of Rands were gained from the optimisation as slope angles could be increased due to improved geotechnical knowledge and management. PPRust’s geotechnical work is considered the benchmark for Anglo American open pit operations.

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