The impacts of silts and clays on mobility of a scaled debris flow physical model
The impacts of silts and clays on mobility of a scaled debris flow physical model
Debris flows are high speed landslides that contain a mix of water and granular material in a range of particle sizes. For flow to travel downslope under gravity, it must shear to dissipate energy. While coarser particles interact frictionally and through collisions, smaller diameter particles, the fines, remain in constant suspension due to the agitated environment. During shearing the pore space expands and shrinks, as flow layers dilate and contract. This means the fluid in the pores must move in and out of voids as a response. If the motion of the fluid contained in the pore space is restricted, this leads to a build-up of pore pressure and reduced interparticle friction. Therefore, flow mobility increases. As the fluid contains fine particles, the reaction to shearing is also governed by the type of fines present. While both silts and clays are included in the fines category due to their small diameters, their impact on fluid properties is very different. Clay suspensions are viscous and shear-thinning, whereas silt suspensions are Newtonian. Currently it is unclear how this difference will affect the efficiency of fluid moving within the pore space network and therefore overall flow mobility. In response to this, a small-scale instrumented flume is used to investigate the influence of either kaolinite clay or silica silt in uniform gravel debris flows.
Hannah Nichols; A. Leonardi; Elisabeth Bowman
11th International Conference on Physical Modelling in Geotechnics (ICPMG2026)
Session 2: Scaling laws and fundamentals
https://doi.org/10.53243/ICPMG2026-246