Temperature-Induced Explosive Behaviour and Thermo-Chemical Damage on Pyrite-Bearing Limestones: Causes and Mechanisms

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Títol: Temperature-Induced Explosive Behaviour and Thermo-Chemical Damage on Pyrite-Bearing Limestones: Causes and Mechanisms
Autors: Martínez-Ibáñez, Víctor | Benavente, David | Hidalgo Signes, Carlos | Tomás, Roberto | Garrido, M. Elvira
Grups d'investigació o GITE: Petrología Aplicada | Ingeniería del Terreno y sus Estructuras (InTerEs)
Centre, Departament o Servei: Universidad de Alicante. Departamento de Ciencias de la Tierra y del Medio Ambiente | Universidad de Alicante. Departamento de Ingeniería Civil
Paraules clau: Limestone | Pyrite oxidation | Thermal treatment | Explosive behaviour | Thermo-chemical damage
Àrees de coneixement: Petrología y Geoquímica | Ingeniería del Terreno
Data de publicació: 28-d’octubre-2020
Editor: Springer Nature
Citació bibliogràfica: Rock Mechanics and Rock Engineering. 2021, 54: 219-234. https://doi.org/10.1007/s00603-020-02278-x
Resum: In this investigation, two different varieties of ‘Prada’ limestones were studied: a dark grey texture, bearing quartz, clay minerals, organic matter and pyrites, and a light grey texture with little or no presence of such components. We have observed two effects of different intensity when heating the dark texture from 400 °C: (1) the explosion of certain samples and (2) greater thermal damage than in the light grey texture. Chemical and mineralogical composition, texture, microstructure, and physical properties (i.e. colour, open porosity, P and S-wave velocity) have been evaluated at temperatures of 105, 300, 400, and 500 °C in order to identify differences between textures. The violence of the explosive events was clear and cannot be confounded with ordinary splitting and cracking on thermally treated rocks: exploded samples underwent a total loss of integrity, displacing and overturning the surrounding samples, and embedding fragments in the walls of the furnace, whose impacts were clearly heard in the laboratory. Thermogravimetric results allowed the identification of a process of oxidation of pyrites releasing SO2 from 400 °C. This process jointly with the presence of microfissures in the dark texture, would cause a dramatic increase in pore pressure, leading to a rapid growth and coalescence of microcracks that leads to a process of catastrophic decay in rock integrity. In addition to the explosive events, average ultrasound velocities and open porosity showed a greater variation in the dark grey texture from 400 °C. That result also points towards a significant contribution of oxidation of pyrites on the thermo-chemical damage of the rock, among other factors such as the pre-existence of microfissures and the thermal expansion coefficient mismatch between minerals. Implications in underground infrastructure and mining engineering works are critical, as the explosive potential of pyrite-bearing limestones bears risk for mass fracturing and dramatic strength decay from 400 °C. Moreover, SO2 released has harmful effects on health of people and the potential to form acid compounds that corrode materials, shortening their durability and increasing maintenance costs.
Patrocinadors: This work was supported by the Spanish Government [Grant number RTI2018-099052-B-I00] and by the Department of Geological and Geotechnical Engineering, Universitat Politècnica de València.
URI: http://hdl.handle.net/10045/109965
ISSN: 0723-2632 (Print) | 1434-453X (Online)
DOI: 10.1007/s00603-020-02278-x
Idioma: eng
Tipus: info:eu-repo/semantics/article
Drets: © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Revisió científica: si
Versió de l'editor: https://doi.org/10.1007/s00603-020-02278-x
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