Thesis--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 180-186).

Thesis (M.S.)--University of Delaware, 2005. / Principal faculty advisor: Nobuhisa Kobayashi, Dept. of Civil & Environmental Engineering. Includes bibliographical references.

Thesis (M.S.)--Humboldt State University, 2006. / Includes bibliographical references (leaves 85-90). Also available via Humboldt Digital Scholar.

Thesis (Ph. D.)--University of Washington, 1987. / Vita. Bibliography: leaves [101]-104.

Thesis (MScIng)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

Thesis (Ph. D.)--College of William and Mary. / Supplemental material for Appendices A-C on CD-ROM.. Includes bibliographical references.

Thesis (Ph. D.)--University of Washington, 1986. / Vita. Bibliography: leaves [157]-174.

Thesis (M. Sc.)--College of William and Mary. / Typescript (photocopy). Vita. Includes bibliographical references (leaves 77-81).

Literature survey made in this research indicated that the roughness has a significant effect on the design of a self-cleansing sewer. A conceptual model was therefore developed taking into account the effect of roughness in the sediment transport in sewers. This model was later tested against experimental data obtained from a test rig. The rig had a pipe which was specially fabricated in two halves so that it could be divided to coat the interior with uniform sand grains to provide roughness. The experimental data shows a good correlation with the model developed. Two relationships i.e. for smooth and rough pipes, were derived from the results. The effects of volumetric sediment concentration, pipe diameter, sediment size and effective roughness on these relationships were in turn examined. Head loss formulae acquired by past researchers were slightly modified to suit the range covered by the experimental data. The relationships developed in this research were subsequently applied to sewer design. These were later compared to the criterion of 0.76 m/s proposed by the British Standards. In the case of smooth pipes, it shows conclusively that the criterion of 0.76 m/s produces excessive slopes for pipe diameter up to 1.0 metre. However, for rough pipes the criterion gives insufficient slopes to maintain a self-cleansing sewer. This is valid up to a pipe diameter of 0.3 metre. Beyond this diameter the criterion gives high slopes. Comparisons were also made with studies in the wider field of sediment transport on fixed bed. These have set in context the proposed formulae for smooth and rough pipes in the design of storm sewers.

Almost all sediment transport equations incorporate the Shields parameter, which is a ratio of the total boundary shear stress as a driving force and the particle weight as a resisting force. Shields (1936) equated particle resistance to entrainment with particle weight, which is proportional to particle diameter, or bed texture. The present work analyses the particle resistance term in the Shields parameter. As the bed material adjusts to a given flow condition, bed stability increases. The arrangement of particles into more stable configurations is here termed geometric structure, and includes the formation of pebble clusters, and imbrication. After an initial surface coarsening, here termed textural structure, particle resistance to movement is a function primarily of geometric structure. The Shields number for entrainment is thus a measure of particle resistance due to both types of bed structure rather than the conventional notion of particle resistance due to particle weight. The response of a mobile bed surface composed of < 8 mm diameter gravels to flowing water was explored in a 6 meter by 0.5 meter flume using four different slopes and various water depths. Corrected bed shear stresses varied between 0.05 and 2.79 Pa. Step increases in discharge with a constant slope caused the bed surface to develop a structure which was more stable at the end of a run than at the beginning. Under these conditions, the Shields number for incipient motion was found to vary between 0.001 and 0.066. This variability can be explained by the degree of geometric structure present. Previous studies, including Shields' work (1936), have implicitly included the effects of geometric structure on incipient motion. Surface coarsening develops with very low flows, but subsequent coarsening in higher flows is minor, with less than 5% increase in median diameter following a 50% increase in bed shear stress. Calculations of Manning's n based on depth, slope, and velocity measurements show an increase in flow resistance as structure develops. The development of a coarse surface layer appears to be limited by flow characteristics near the bed which are in turn modified by the development of structure. Measurements of the area occupied by the largest stones show that they do not cover more than 14% of the surface during maximum coarsening. Froude scaling of the flume data indicates that the time necessary for development of maximum strength is on the order of a month for natural rivers under steady flow conditions. This suggests that gravel river beds are rarely in equilibrium with natural flow conditions. / Arts, Faculty of / Geography, Department of / Graduate