Doctor of Philosophy / In this thesis an examination is made of the vibro-replacement technique for the stabilisation of cohesive soils. Improvement is achieved by the formation of stiffer columns of granular material within the soil deposit using a large cylindrical vibrator referred to as a vibroflot. Granular piles (also termed stone columns) are used either singly or in small groups to supoort isolated footings or large numbers are installed in a regular array to support widespread loads. Each of these modes of application are investigated.

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Doctor of Philosophy / In this thesis an examination is made of the vibro-replacement technique for the stabilisation of cohesive soils. Improvement is achieved by the formation of stiffer columns of granular material within the soil deposit using a large cylindrical vibrator referred to as a vibroflot. Granular piles (also termed stone columns) are used either singly or in small groups to supoort isolated footings or large numbers are installed in a regular array to support widespread loads. Each of these modes of application are investigated.

Rayleigh scattering, that is the elastic and coherent scattering of photons from bound atomic electrons, has been investigated for use as an active probe for substance identification. An angular dispersive scattering system has been developed for materials identification utilising the 22 keV Kalpha X-ray line from a low power (25 Watt) silver anode X-ray tube. Differential scattering cross-sections have been measured for a wide range of low- to high-Z materials and compared with free atom theoretical predictions. Experimental results compare favourably with theory and evidence has been found to suggest that inter-atomic and inter-molecular interference effects have little or no effect upon the total scattering cross-section. The potential of Rayleigh scattering for detection of inclusions of low-Z media within extended objects of similar atomic constitution has been investigated with particular emphasis on the detection of potential contaminants in food products. The contrasts obtained with scatter techniques are substantially in excess of those achievable with conventional transmission measurements. By exploiting the ratio of the scattering in two regions of momentum space as the scatter parameter the contrast between inclusion and matrix may be increased to over five times that of transmission methods. This technique may be used in many situations where alternative photon interrogation methods such as X-ray transmission or X-ray fluorescence are unsuitable and a wide range of potential applications including quality control, sorting of plastics, security screening and oil/water discrimination have been considered.

Because of an interaction between the load history and the material's properties a reduction in the serviceability of safety of a structure may be seen as the result of a random process of damage accumulation with time. A damage model is proposed and verified to deal with this type of problem in general, and specifically with duration-of-load effects in timber structures. Through comparisons with and discussion of other damage accumulation models, the proposed model is found to be both suitable to represent experimental results and relatively easy to use. A reliability analysis for a single structural member with a service life of 30 years is studied for different snow loading conditions of three Canadian cities,using the damage model in combination with Rackwitz-Fissler's algorithm. A simplified analysis method is proposed and compared with a large-scale Monte-Carlo simulation. The results of the reliability analysis are found to be satisfactory. Finally, the implementation of the reliability analysis in a simple design guideline for load duration effects is discussed. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

BaBibliography: pages 88-92. / A variety of ceramic and ultrahard materials have been subjected to both solid particle and cavitation erosion. The materials tested include three grain sizes of alumina, stabilised zirconias, sialon, cubic boron nitride and polycrystalline diamond, and these have a range of microstructural, physical and mechanical properties. The damage modes are described for the two types of erosion and the results are critically discussed. It has been shown that different properties and microstructural features control the respective types of erosion. Hardness is the critical property which controls material loss during solid particle erosion. Cavitation erosion in contrast is less sensitive to hardness, but is extremely defect sensitive and preferentially attacks weak or damaged regions on the target. Grain size and shape, and th.e properties of the grain boundary or intergranular phase exert a strong influence on both types of erosion. It has in addition been concluded, that a propensity for a stress induced phase transformation, such as that exhibited by stabilised zirconia, will benefit the resistance of a ceramic to erosion. Ultrahard materials generally outperform the structural ceramics that were tested. While it was not possible to ascertain the effects of grain size conclusively, a large extent of intergrowth between the crystallites during manufacture appears to be beneficial to erosion resistance.