Other than static liquefaction, slow-moving slips driven by transient pore water pressure leading to high speed landslide are the other possible cause of failure of loose fill slopes.
For loose fill lying on low permeability soil layers, there is potential storage of infiltrating water when the slope of underlying low-permeability soil layer is mild. As such, there is a localized zone of high transient pore water pressure induced within the fill material. Flowslides normally start with a local slip caused by transient pore water pressure by soil layering or flow restriction. Then, the nature of slow-moving soil debris and the geometry of slip result in a fast landslide.
This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.