Rheological behaviour of dilute soil-water mixtures: role of interactions from colloidal and non-colloidal particles

The rheological behaviour of dilute soil-water mixtures, such as hyperconcentrated mixtures and interstitial fluids in debris flows, can significantly affect the flow dynamics of flow-type landslides. These mixtures often contain clay, silt, and sandy particles. Despite great efforts, the effects of soil type and texture on the rheological behaviour of these mixtures are still not well understood. To tackle this issue, an experimental investigation is carried out using a narrow-gap rotational viscometer to evaluate the interactions from colloidal (clay) and non-colloidal (silt and sand) particles and possibility of flow regime change. The flow curves of dilute mixtures are determined with and without a dispersion agent. A functional curve between spindle speed and Reynolds Number or Froud Number is proposed to distinguish different flow regimes in the narrow-gap rotational viscometer. Results demonstrate the applicability of the Bingham model for describing the bulk rheological behaviour of dilute mixtures. The mixture viscosity governs the contribution of the hydrodynamic effects from all particles, while the yield stress governs the contribution of the colloidal effects from colloidal particles. Results also reveal that for dilute mixtures containing particles up to medium sand size, the main cause of the flow regime change is the flow boundary conditions.

Automated summary

The rheological behavior of dilute soil-water mixtures, containing clay, silt, and sandy particles, is still not well understood. To investigate this, experiments were conducted using a narrow-gap rotational viscometer to evaluate the interactions between colloidal and non-colloidal particles and the possibility of flow regime change. Results showed that the Bingham model could describe the bulk rheological behavior of dilute mixtures and that the viscosity and yield stress played important roles. It was also found that the flow regime change in dilute mixtures was mainly influenced by flow boundary conditions.