Influences of Rheometer Size and the Grain Size on Rheological Parameters of Debris Flow

Debris flows are non-Newtonian fluids. Theirs rheological parameters depends on the volume concentration, grain size composition, fines content and fines plasticity. To get realistic data for modelling of debris flows, the rheological parameters had to be measured at different volume concentrations, taking into account the whole grain size distribution. Rheometers for fluids are limited with the gap size and usually only fine grained suspensions could be investigated. The results measured in such device on coarse grained soils may not be representative. The paper presents the study in which two shear rate controlled coaxial cylinder rheometers were used to investigate the influence of maximum grain size to the rheological parameters of the Stoze debris flow: the larger ConTec Viscometer 5, in which the maximum grain size is 22.4 mm and the smaller Brookfield DV3T HB rheometer. Rheological parameters obtained by using both devices were compared based on water content, volume concentration and maximum grain size.