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Measurement protocol proposal for the rheological characterization of volcanic sediment suspensions

Carla Tranquilino 1, Fabio Dioguardi1, Pierfrancesco Dellino1, Luigi Gentile2, Lizeth Caballero3, Damiano Sarocchi4, Maria Lacalamita1.

  • Affiliations: 1 Dept. of Earth and Geoenvironmental Sciences, University of Bari Aldo Moro, Italy; 2 Dept. of Chemistry, University of Bari Aldo Moro, Italy; 3 National School of Earth Sciences, National Autonomous University of Mexico, Mexico; 4 Institute of Geology, University Autonomous of San Luis Potosí, San Luis Potosí, Mexico. 

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 160

  • Programme No: 3.5.19

  • Theme 3 > Session 5

Abstract

The study of the rheological behavior of water-sediments suspensions is fundamental for understanding the fluid-dynamic behavior of geophysical gravity flows. Lahars represent the volcanic case of such flows; they occur along the slopes of volcanoes and consist of large blocks of sediment supported within a matrix of fine sediment suspended in water. Most of the stresses are distributed within the fine matrix, i.e., the water-fine sediments suspension, due to its abundance in the flow and its capacity to support the large blocks. These stresses are mainly generated by the deformation naturally imposed by the slope of the volcano, while the matrix material presents a resistance to this deformation, which can be described by rheological models. In this study, we focused on the rheological characterization of the matrix using a small-scale concentric cylinder rheometer.Specifically, this work proposes an appropriate measurement protocol for the rheological characterization of fine sediment homogeneous suspensions that achieved the necessary physical conditions to establish a laminar and steady flow and without slippage phenomena. The proposed protocol consisted of a staircase function testing a shear-rate range between to  with a homogenization step between each measurement step.Different measurement times were tested according to the maximum sediment settling time in a virtual column of homogeneous particle suspension. The settling time was calculated by estimating the settling velocity of the particles within the suspension.First results obtained from the use of this protocol show that the apparent viscosity depends on the shear rate, with an inverse exponential relationship with increasing shear rate.