(409f) Flowability Measurements and Rheological Investigations of Volcaniclastic Debris Flows from Campania Plain (southern Italy)

In perivolcanic areas such as the Campania Plain (southern Italy) is not so uncommon the remobilisation of the pyroclastic deposits emplaced on the slopes of the volcanoes and of the surrounding reliefs, giving rise to very hazardous phenomena known as volcaniclastic debris flows (Di Vito et al., 2019). They are very unpredictable phenomena that can happen during or soon after an eruption, but also tens or hundreds of years later, representing both a short and long-term hazard factors for people, buildings and natural environment (Zanchetta et al, 2004). The main triggering mechanism is represented by intense and/or prolonged rainfalls (Sulpizio et al., 2006 and references therein) that are becoming more frequent as a consequence of climate change.

The novelty of this project is combining engineering and geology to analyse samples of volcaniclastic debris flows related to the AD 472 Pollena eruption from Somma-Vesuvius volcano, in Campania region, to acquire fundamental knowledge that will help develop constitutive equations to use in existing numerical models. Since very few rheological analysis with real samples are available, the final aim is to develop a tool that can be applied to all the volcaniclastic debris flows and that can be used to manage the risks associated with these poorly known phenomena.

The experiments have been carried out with the FT4 powder rheometer (Freeman Technology), commonly used in the chemical and process industries, that has been modified for our purposes.

Shear cell and wall friction tests give information on the flowability of the materials through charactering and measuring relevant parameters such as the angle of internal friction and the wall friction angle. Compressibility tests show the change in density and volume as a function of the applied normal stress. The relationship between shear stress and shear rate is also quantified using a 3D printed attachment in a Couette flow configuration (Ait Ali Yahia et al., 2020).

Preliminary results show that the particles’ size influences the compressibility but not so much the shear stress; the wall friction angle depends on the roughness of the wall friction head and also on the grainsize distribution. Concerning the rheological analysis, the polydisperse samples and the finest grain sizes are difficult to analyse, and we are currently working on devising the correct measuring protocol and we are considering working with the suspensions. Future work will see the development of a systematic experiments’ campaign in Mexico, where different rheometers will be used and large-scale experiments will be performed, in order to link the rheology measurements in the laboratory to the dynamics observed in the large-scale experiments.

References:

Ait Ali Yahia L., Piepke T.M., Barrett R., Ozel A., Ocone R. (2020). Development of a virtual Couette rheometer for aerated granular material. AIChE J., e16945.

Di Vito M.A., Talamo P., de Vita S., Rucco I., Cesarano M. (2019). Dynamics and effects of the Vesuvius Pomici di Avellino Plinian eruption and related phenomena on the Bronze Age landscape of Campania region (Southern Italy). Quaternary International 499, 231-244.

Sulpizio R., Zanchetta G., Demi F., Di Vito M.A., Pareschi M.T., Santacroce R. (2006) - The Holocene syneruptive volcaniclastic debris flows in the Vesuvian area: Geological data as a guide for hazard assessment. Geol. Soc. Am. Spec. Pap., 402, 203-221.

Zanchetta G., Sulpizio R., Pareschi M.T., Leoni F.M., Santacroce R. (2004). Characteristics of May 5-6, 1998 volcaniclastic debris flows in the Sarno areas (Campania, southern Italy): relationships to structural damage and hazard zonation. Journal of Volcanology and Geothermal Research 133, 377-393.