This research aims to investigate the initiation mechanisms of flow landslide through the implementation of emerging new sensor technology in a series of instrumented laboratory flume tests. 3-axis MEMS accelerometers are installed in the soil specimens to capture internal soil movement and rotation, while miniature pore water pressure transducers characterize the water pressure at the bottom and sides, prior and during the first few seconds of failure process. Acute sensitivity of these sensors, complemented with the minimum sampling frequency of 10000 Hz and noise filters accounting for unwanted disturbances in both low and high frequency bands, demonstrate the internal characteristics inside the soil, even of the slightest activity, both prior and during fluidization....[ Read more ]

This research aims to investigate the initiation mechanisms of flow landslide through the implementation of emerging new sensor technology in a series of instrumented laboratory flume tests. 3-axis MEMS accelerometers are installed in the soil specimens to capture internal soil movement and rotation, while miniature pore water pressure transducers characterize the water pressure at the bottom and sides, prior and during the first few seconds of failure process. Acute sensitivity of these sensors, complemented with the minimum sampling frequency of 10000 Hz and noise filters accounting for unwanted disturbances in both low and high frequency bands, demonstrate the internal characteristics inside the soil, even of the slightest activity, both prior and during fluidization.

The laboratory flume setup is carefully designed to avoid all possible boundary effects. The draining nature of the porous stone bed sought to replicate the interparticle friction angle of bed and soil, and also to allow water pressure buildup but not a layer of eroding water front right above the bed. Controllable groundwater pipes with porous stone fitting make possible a replication of rainfall pattern from field to be applied to the soil sample to investigate the hydrogeological effect on the initiaton of flow landslides.

The differences contributing to the initiation and subsequent failure mode of flow landslides are attributed in terms of fines content and water supply mode of loose soil in this research. Behavior of undrained and drained shearing zone as a result of the presence of fines in loose soil were entirely different. Fines were able to inhibit instantaneous draining behavior of loose soil, thus sustaining the excess porewater pressure induced during contractive shearing as a result of a sudden rise of groundwater inflow, leading to catastrophic failure. Loose soil without fines was unable to induce such an undrained layer of fluidized contractive shear zone due to its high permeability and fast draining property. Contractive fluidized flow landslides were found to be highly correlated to a peak input of water supply, be it from infiltration or hydrogeological condition. Fluidized shearing zone underneath a draining loose soil slope toe was insufficient to develop a full-scale landslide. Only momentum coming from fluidized shearing zone way up in the rear of soil mass is enough to convert the existing high potential energy into a pushing force that subsequently brings out the rest of the soil. An absence of fines rendered the soil highly permeable, and the fast draining caused negative excess porewater pressure which retarded the soil from going into full-scaled fluidization. Retrogressive and cascading patterns in episoidal events were observed instead.