Static liquefaction mechanisms in loose sand fill slopes

To investigate potential triggering and failure mechanisms of loose fill slopes, two centrifuge model tests were conducted on loose sand with a contractive tendency and high liquefaction potential. The behaviour of loose sand fill slopes subjected to rising groundwater or rainfall was simulated using a geotechnical centrifuge. Moreover, a three-dimensional back-analysis and parametric study were conducted to investigate the role of soil nails in preventing the triggering of static liquefaction in loose fill slopes. Contrary to the rainfall test where only excessive settlements are observed, a rapid, and brittle fluidised flowslide in the slope can be identified when subjected to rising groundwater. The fluidised flowslide is triggered by a localised drained surface failure in the form of a gully at the crest of the slope. The initial failure at the crest induces the generation of significant excess pore pressures within the slope, causing a significant reduction in effective stress and loss of shear strength due to static liquefaction. For an identical slope, numerical simulations indicate that a fluidised flowslide can be prevented by soil nailing. Soil nailing can prevent the peak shear strength of the soil from being mobilised and limits the excessive strains required to trigger static liquefaction.

Automated summary

The triggering and failure mechanisms of loose fill slopes, as well as the role of soil nails in preventing static liquefaction, were investigated using centrifuge model tests and numerical simulations. Rising groundwater can induce a rapid fluidised flowslide in the slope, which can be prevented by soil nailing.