Static Liquefaction of Loose Granular Landslides
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Highly mobile landslides can have devastating impacts on infrastructure and human life. In order to mitigate the risks of these landslides, it is critical to understand how they are triggered and the mechanism behind their high mobility. The objective of this research is to investigate the initiation and propagation of liquefaction and the resultant flow mobility due to static triggering in loose granular slopes using two physical modelling techniques. The first experiment used geotechnical centrifuge techniques to determine the velocity of the liquefaction propagation in saturated granular slopes for loose and dense soils, by varying the thickness and void ratios of the materials. The results of these tests indicate that all model slopes which were loose of the critical state were highly liquefiable upon shearing, while all dense tests resisted liquefaction and instead were subject to erosion as they could withstand much higher seepage flow rates. Tests that experienced liquefaction reveal that the velocity of the liquefaction propagation is not dependent on the velocity of shearing of the initial failure (0.25-0.5 m/s), and that the speed of propagation of the liquefaction front can happen at an order of magnitude faster than that of the initial triggering event (4.2-4.3 m/s). A second series of experiments was performed to develop testing techniques and best practices for dam breach experiments using a large-scale flume. In this test series, both saturated fine sand and coarse grained material were examined. Results from testing the saturated coarse grained material show that landslide mobility increases with respect to dry flow when the material is saturated. As expected, the increase in mobility with the addition of water is due to the proportional decrease in basal shear resistance. In contrast, the same experiment with fine sand did not experience failure and most of the material remained in the release box. This surprising finding indicates the possible significant role of air entry and matric suction on the higher strength in the latter case and indicates an interesting avenue for future research to quantify this phenomena.
URI for this recordhttp://hdl.handle.net/1974/24978
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