Graduation date: 1999

This dissertation details the development of a block model for the movement of submarine slides with emphasis on possible hydroplaning. Unlike previous models, the block model simulated the mechanism of hydroplaning by monitoring the contact condition between the bottom surface of the slide mass and the underlying ground. The effect of hydroplaning on the movement of the slide mass is considered by changing the forces applied on the slide mass by the underlying ground according to the contact condition. The hydrodynamic stresses applied on the slide mass by the surrounding fluid are determined based on the numerical simulations of the flow around a sliding mass. The sliding process of the block is disretisized in a step-by-step manner using a Newmark scheme. A computer program is also written to implement the block model. The block model is validated by comparisons between the numerical results and data reported by Mohrig, et al (1999) for laboratory experiments on subaqueous slides. An illustrative study is also conducted using the block model for the movement of the sediment slabs during the Storegga Slide. The block model has successfully predicted the occurrence of hydroplaning and run-out distances of subaqueous slides. Numerical results with the block model supports the mechanism of hydroplaning for subaqueous slides with greater run-out distances than comparable subaerial slides.

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Many free surface flow problems encountered in hydraulic engineering can be accurately analyzed by utilizing the depth-averaged equations of motion. A consequence of adopting this depth-averaged modeling approach is that closure approximations must be implemented to represent the so-called effective stresses. These effective stresses consist of the depth-averaged viscous stresses, which are usually small and therefore neglected, the depth-averaged turbulent Reynold's stresses, and additional stresses resulting from depth-averaging of the nonlinear 'convective acceleration terms (often called momentum dispersion terms). Attention is focused on examining closure for both the depth-averaged Reynold's stresses and the momentum dispersion terms. In the present study, the penalty function finite element technique is utilized to solve the governing hydrodynamic and turbulence model equations for a variety of flow domains. Alternative momentum dispersion and turbulence closure models are proposed and evaluated by comparing model predictions with experimental data for strongly curved open channel flow. The results of these simulations indicate that the depth-averaged (k-ε) turbulence model yields excellent agreement with experimental observations. In addition, it appears that neither the streamline curvature modification of the depth-averaged (k-ε) model, nor the momentum dispersion models based on the assumption of helicoidal flow in a curved channel, yield significant improvement in model predictions. Overall model predictions are found to be as good as those of a more complex and restricted three dimensional model. / Ph. D.