As a simple model of submarine landslides, laboratory experiments were performed to determine the effects of Darcy number on the collapse of granular columns in water with loose packing. The Darcy number describes the tendency for pore fluid pressure developed by the contraction process to reduce the friction for loosely packed columns. The experimental results reveal that the collapse depends on the Darcy number, Da, the bed slope, and the initial aspect ratio of the column. Predictive models are provided for the spreading duration, spreading velocity, runout distance, and finial height of the deposit. Comparison of the present results with those of the previous studies reveals that the effects of Da on collapse vary with the packing conditions. Specifically, a positive runout-Da relationship exists in cases of loose packing, while a negative relationship is revealed for dense packing. A simple dynamic analysis is performed to explore observation, which is a consequence of different pore pressures occurring inside columns owing to different packing.
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