Thesis (Ph. D.)--Texas A & M University, 1997. / Includes bibliographical references (leaves 241-250).

Thesis (Ph. D.)--Washington State University, December 2006. / Includes bibliographical references (p. 76-84).

Thesis (Ph. D.)--Rhodes University, 2001. / Title from PDF t.p. (viewed on May 6, 2006). Includes bibliographical references (p. [289]-308).

No description available.

This thesis contains an experimental investigation of the yielding behaviour of sand loaded in triaxial compression, extension and a combination of both (stress reversal). The testing programme was conducted on 102 x 205 mm medium dense samples of fine Leighton Buzzard sand. A considerable part of the work was directed towards improving the testing technique in order to obtain good quality data. For this purpose, an automated stress path system was constructed and programmed utilizing a microcomputer to take full control of the applied stresses so that any desired stress path could be closely followed in the conventional triaxial cell. Furthermore, new displacement measuring devices were developed and used throughout the testing programme for monitoring both axial and radial deformation locally on the middle third of the triaxial specimen. The results indicate that generally the behaviour of sand is highly anisotropic and that during non-reversal stress paths, the yield condition can be described by a set of curved yield loci in the p' - q stress space. Such yield loci have more curvature in extension than in compression. Stress reversal is found to cause a significant softening of the stress-strain behaviour. However, depending on the level of deviatoric prestress on the opposite side, the sand may become even softer than in the virgin stress-strain condition. The typical errors likely to occur during conventional deformation measurement are discussed, and it is concluded that the use of local measurement should replace both external axial and volumetric monitoring techniques.

Although Cambodia banned sand exports in 2017, under-regulated sand extraction in rivers across the country continues, driven by demand from rapid urbanization and land reclamation around Phnom Penh. In the last decade, the sand extraction industry has come under intense scrutiny for its role in riverbank erosion and degradation of aquatic ecosystems, with some activists and scholars highlighting how this damages livelihoods and displaces rural Cambodians. At the same time, the sand boom in Cambodia has created a demand for labour, offering opportunities to rural Cambodians who have few other livelihood options in their home provinces. However, the vast majority of wealth from sand extraction does not accrue to sand labourers. Using qualitative data gathered from various sand extraction and transportation sites along the Mekong River in and around Phnom Penh, this thesis reveals new insights into the sand extraction industry. This thesis draws upon sustainable livelihoods approaches to reveal the difficult trade-offs that rural Cambodians must make when leaving their homes to enter the sand extraction industry. The thesis then uses the concept of precarity to show that sand labour in Cambodia is characterized by precarious employment conditions, including work in remote and isolated locations, separation of families when men leave for sand related labour, a lack of formal work contracts or rights, an inability to diversify income sources, and unpredictable cycles of intermittent work. The thesis then follows the approach used in political ecology literature, examining the power relations that help explain why sand labourers have little choice but to pursue precarious livelihoods, while business and government elites amass great wealth from resource extraction in Cambodia. In doing so, this thesis helps to broaden the understanding of the implications of a little understood yet hugely important resource extraction industry.

<p> Sediment samples were taken from the exposed facies of two quarries north of Burford Ontario. The samples were then dry sieved and the results were plotted as frequency histograms to show the type and quantity of sediment present. Moreover, measurements of soil tongues, sand lenses and strata depths were recorded to provide a comprehensive understanding of the depositional history and processes.</p> <p> The above research was then combined with the present day comprehension of the depositional history of southern Ontario. The conclusions reached in this paper are useful, as they contribute and improve the understanding of the depositional history of southern Ontario.</p> / Thesis / Candidate in Philosophy

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

This thesis seeks to examine the effective convective heat exchange of sand as a heat exchange medium. The goal of this exploratory research is to quantify the heat transfer coefficient of sand in a proposed Thermal Energy Storage (TES) system which intends to complement solar thermal power generation. Standard concentrator solar thermal power plants typically employ a heat transfer fluid (HTF) that is heated in the collector field then routed to the power generators or TES unit. A fairly clear option for a TES system would be to utilize the existing HTF as the working storage medium. However, the use of conventional HTF systems may be too expensive. These fluids are quite costly as the quantity needed for storage is high and for some fluids their associated high vapor pressures require expensive highly reinforced containment vessels. The proposed storage system seeks to use sand as the storage medium; greatly reducing the expenses involved for both medium and storage costs. Most prior TES designs using sand or other solids employed them in a fixed bed for thermal exchange. The proposed TES system will instead move the sand to drive a counter flow thermal exchange. This counter flow design allows for a much closer temperature of approach when compared to a fixed bed. As cost and performance are the primary goals to tackle of the proposed system, the evaluation of the sandâ s thermal exchange effectiveness in a flowing state is necessary. Experiments will be conducted to measure the effective heat transfer coefficient between the sand and representative solid surfaces used as the heat transfer conduits. Additional experiments that will be looked at are wear caused by the sand as a consideration for long term design viability as well as angle of repose of the sand and its effect on scoop design for improved materials handling. Key investigational aspects of these experiments involve the sand grain size as well as shape of the heat exchanger surfaces. The thesis will evaluate the resulting convective heat transfer coefficient of the sand as related to these features. The data will then be compared and verified with available literature of previously studied characteristic thermal properties of sand. The measured and confirmed data will then be used to further aid in a design model for the proposed TES system.

Thesis (PhD. (Botany)) - Rhodes University, 2008