The sphere drag rheometer: A new instrument for analysing mud and debris flow materials

The present study focused on novel rheometrical tool for the determination of the rheological behavior of large particle mixtures with particular interest in the application to granular materials involving in fast landslides as mud and debris flows. The main goal is the development of the Sphere Drag Rheometer (SDR), a home-made large-scale rheometer that allow to estimate the rheological properties of these mixtures considering particles up to 50 mm grain size. The SDR is composed of a sphere rigidly joined to a support that moves at constant velocity into the mixture. Compared to standard rheometer, the SDR uses much higher volume of mixtures of wider grain size distribution next to that in situ. Several pyroclastic soils collected from the source area of debris flows occurred in Campania region (Southern Italy) were analyzed. The paper reports the experimental results on fine particles mixtures, large particle mixtures, and their comparison. The experimental results on fine mixture are compared with those obtained by conventional rheometrical tools reported in previous papers.