Issue 52

C. Caselle et alii, Frattura ed Integrità Strutturale, 52 (2020) 247-255; DOI: 10.3221/IGF-ESIS.52.19 247 Crack coalescence and strain accommodation in gypsum rock Chiara Caselle University of Torino, Department of Earth Science, Italy chiara.caselle@unito.it , http://orcid.org/0000-0002-3081-1555 Sabrina Bonetto University of Torino, Department of Earth Science, Italy sabrina.bonetto@unito.it, http://orcid.org/0000-0002-6579-1419 Daniele Costanzo Polytechnic of Torino, Department of Structural, Geotechnical and Building Engineering, Italy daniele.costanzo@polito.it , http://orcid.org/0000-0002-1957-275X A BSTRACT . The micro-mechanisms involved in the deformation of gypsum rock have for long time interested the scientific world and are still not completely understood. The present work proposes an experimental investigation of strain accommodation in gypsum rock, reporting data referred to uniaxial and triaxial stress conditions. The rock deformation was investigated with a multiscale approach, with the comparison of results from DIC and microstructural analyses, aiming to propose an interpretation of crack coalescence and strain accommodation in natural gypsum rock (i.e. branching selenite facies), focusing on the influence of textural and compositional layering on the mechanical response. The failure was observed to coalesce following an unstable step-wise process. With the increase of confining pressure, the material develops a structure of plastic accommodation of strain, favoured by the peculiar crystallographic structure of gypsum, with water molecules layered in the salt structure. K EYWORDS . Gypsum; DIC analysis; Microstructure; Brittle-ductile transition. Citation: Caselle, C., Bonetto, S., Costanzo, D., Crack coalescence and strain accommodation in gypsum rock, Frattura ed Integrità Strutturale, 52 (2020) 247-255. Received: 31.10.2019 Accepted: 08.02.2020 Published: 01.04.2020 Copyright: © 2019 This is an open access article under the terms of the CC-BY 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. I NTRODUCTION ypsum is a soft rock that is involved in a wide range of industrial applications (e.g. it is a main component of stucco, wallboards, cements, paints and soil conditioner/fertilizer; it is used in food industry as a flocculant and in several clinical applications as regenerative material for bone defects, dental plaster, or as a delivery vehicle for pharmaceutical agents [1]). Quarry sites, both open pit and underground, are therefore largely exploited all over the world. G