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Effects of heat on the mechanical properties of selected rock types: A laboratory study
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Mining and Geotechnical Engineering.
Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
2011 (English)In: Harmonising Rock Engineering and the Environment: proceedings of the 12th ISRM International Congress on Rock Mechanics, Beijing, October 18 - 21, 2011 / [ed] Qihu Qian; Yingxin Zhou, Leiden: CRC Press/Balkema , 2011, 815-820 p.Conference paper (Refereed)
Abstract [en]

A laboratory study was conducted to study the effect of heat on the mechanical properties of diabase, granite and quartzitic schist at temperatures of 400◦C, 750◦C and 1100◦C. Unheated samples were also studied. The reasoning behind this study was to understand the effect of elevated temperatures on the rock mass, such as in the event of a fire in a rock tunnel. Samples from the aforementioned rock types were heat treated at temperatures shown above, cooled slowly to room temperature and then subjected to uniaxial compression and Brazilian tests. Thin sections were extracted from the heat treated samples for microscopic analyses, which assisted in explaining the reasons for the mechanical behaviour observed from the mechanical test results. The uniaxial compression test showed that the strength of the rock specimens increased by 6% for granite to 29% for diabase at 400◦C when compared to the UCS values of the unheated specimens. From 750◦C to 1100◦C the decay in the strength was very rapid. From the microscopic analyses it was concluded that the increase in the strength of the rock specimens at 400◦C is attributed to the initial reaction of the rock forming minerals, hence the rock specimens were less brittle but more plastic. The rapid drop in the strength from 750◦C to 1100◦C is attributed to the mineralogical changes, micro-cracking and dehydration due to the loss of crystal bound water. At 1100◦C the rocks were highly friable and crumbled very easily when tested mechanically. The effect of mineralogical changes was obvious in diabase where the physical appearance of the samples mimicked that of natural iron, which is believed to be due to the alteration of pyroxene. The result was an increase in strength by 29% at 400◦C compared to the unheated specimens. Even at 750◦C the strength was slightly higher than unheated specimens. In summary; the mechanical behaviour of the rock specimens depended on the temperature level and the mineralogical and physical changes that occur at that temperature.

Place, publisher, year, edition, pages
Leiden: CRC Press/Balkema , 2011. 815-820 p.
Research subject
Mining and Rock Engineering
URN: urn:nbn:se:ltu:diva-30988Local ID: 5031b0d3-d8ff-46f7-81bc-36f1f72c9865ISBN: 978-0-415-80444-8OAI: diva2:1004217
ISRM International Congress on Rock Mechanics : 18/10/2011 - 21/10/2011
Godkänd; 2011; 20111220 (ysko)Available from: 2016-09-30 Created: 2016-09-30Bibliographically approved

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