Slope stability and avalanching of sediments, the effects of biological activity
An experimental analysis has been conducted on the stability of sediment slopes. This has included a study of the geotechnical properties of sediments and the effects of supporting medium and biological activity on avalanching. The thesis is divided into six sections with three appendices. Section 1: Section one describes the geotechnical properties of Ardmore Bay sediments including particle size distribution, and the phase properties of void ratio, porosity, specific gravity, dry density and bulk density. Section 2: Experiments were conducted on the effects of orientation and shape of the container, volume of sediment, and particle size, on angles of avalanche and repose. Section 3 and 4: Experiments were conducted on the effects of air, water, 50% glycerol. 100% glycerol and alginic acid (low viscosity) on angles of avalanche and angles of repose at successive intervals of time (termed setting time). Section 5: The objectives of the biological experiment were to quantify the effects of biological activity on avalanching. Section 6: The objectives of the Mytilus edulis experiment were to quantify the production of byssus threads in relation to sediment stability. The results of the experiments reported in sections one to six are discussed in relation to mechanisms controlling slope stability in terrestrial and aquatic environments. They are also considered with reference to environmentally friendly methods of stabilising slopes now under active investigation by civil engineers. Topics covered include geotechnical properties, sediment phase relations, fluid viscosity, factors of safety, duration of avalanche and biological activity. I have also discussed slope failure mechanisms, and parallel between engineering and biological stabilisation of slopes. The appendices include geotechnical details of the sediment properties and phase relationships of sediments, sediment permeability, and sediment shear strength. I have also included details of factors of safety and stability analysis of slopes, treated from a civil engineering point of view.