The tensile strength of volcanic rocks
- 1University of Strasbourg, Strasbourg Institute of Earth & Environment, Strasbourg, France (heap@unistra.fr)
- 2Institut Universitaire de France (IUF), Paris, France
- 3Department of Earth Science, Natural Resources and Sustainable Development (NRHU), Uppsala University, Villavägen 16, SE-752 36 Uppsala, Sweden
- 4Department of Civil, Geo and Environmental Engineering, Technical University of Munich, Arcisstrasse 21, 80333 Munich, Germany
- 5NGI – Norwegian Geotechnical Institute, Oslo 0806, Norway
- 6School of Earth Sciences, University College Dublin, Dublin, Ireland
- 7Center for Rock Instability and Seismicity Research, Northeastern University, Shenyang 110819, China
- 8Université de Paris, Institut de Physique du Globe de Paris, CNRS UMR 7154, F-75005 Paris, France
- 9Observatoire Volcanologique et Sismologique de Guadeloupe, Institut de Physique du Globe de Paris, F-97113 Gourbeyre, France
- 10State Key Laboratory of Coastal & Offshore Engineering, Dalian University of Technology, Dalian 116024, China
- 11State Key Laboratory of Geological Processes and Mineral Resources, China University of Geosciences (Wuhan), Wuhan 430074, China
- 12Earth Science, Durham University, Science Labs, Durham, DL1 3LE, United Kingdom
The tensile strength of volcanic rock exerts control over several key volcanic processes, including fragmentation, magma chamber rupture, and dyke propagation. However, and despite this importance, values of tensile strength for volcanic rocks are relatively rare. It is also unclear how their tensile strength is modified by rock physical properties such as porosity, pore size, and pore shape and ongoing processes such as hydrothermal alteration. We present here the results of systematic laboratory and numerical experiments designed to better understand the influence of porosity, microstructural parameters (pore size, shape, and orientation), and hydrothermal alteration on the tensile strength of volcanic rocks. Our data show that tensile strength is reduced by up to an order of magnitude as porosity is increased from 0.01 to above 0.3, highlighting that porosity exerts a first-order control on the tensile strength of volcanic rocks. Our data also show that pore diameter, pore aspect ratio, and pore orientation can also influence tensile strength. Finally, our data show that hydrothermal alteration can decrease tensile strength if associated with mineral dissolution and weak secondary minerals, or increase tensile strength if associated with pore- and crack-filling mineral precipitation. We present a series of theoretical and semi-empirical constitutive models that can be used to estimate the tensile strength of volcanic rocks as a function of porosity or alteration intensity. To outline the implications of our data, we show how tensile strength estimations can influence predictions of magma overpressures and assessments of the volume and radius of a magma chamber, and we explore the influence of alteration using discrete element method modelling in which we model the amount and distribution of damage within variably-altered host-rock surrounding a pressurised dyke. It is our hope that the experiments, models, and understanding provided by our study prove useful for modellers that require the tensile strength of volcanic rocks for their models.
How to cite: Heap, M., Aguilar Velasco, A., Baud, P., Carbillet, L., Deegan, F., Gilg, H. A., Griffiths, L., Harnett, C., Heng, Z., Holohan, E., Komorowski, J.-C., Moretti, R., Reuschlé, T., Rosas-Carbajal, M., Tang, C., Troll, V., Vairé, E., Vistour, M., Wadsworth, F., and Xu, T.: The tensile strength of volcanic rocks, EGU General Assembly 2022, Vienna, Austria, 23–27 May 2022, EGU22-992, https://doi.org/10.5194/egusphere-egu22-992, 2022.
