Mechanical characteristics and microcosmic mechanisms of granite under temperature loads

• Published in: Journal of China University of Mining and Technology Vol. 18; no. 3; pp. 413 - 417
• Main Authors: XU, Xiao-li, GAO, Feng, SHEN, Xiao-ming, XIE, He-ping
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.09.2008
• Subjects: granite; mechanical characteristics; microcosmic mechanism; temperature effect; mechanical characteristics; granite; microcosmic mechanism; temperature effect
• ISSN: 1006-1266
• DOI: 10.1016/S1006-1266(08)60086-3

The relationships between mechanical characteristics of rock and microcosmic mechanism at high temperatures were investigated by MTS815, as well as the stress-strain behavior of granite under the action of temperatures ranging from room temperature to 1200 °C. Based on a micropore structure analyzer and SEM, the changes in rock porosity and micro structural morphology of sample fractures and brittle-plastic characteristics under high temperatures were analyzed. The results are as follows: 1) Mechanical characteristics do not show obvious variations before 800 °C; strength decreases suddenly after 800 °C and bearing capacity is almost lost at 1200 °C. 2) Rock porosity increases with rising temperatures; the threshold temperature is about 800 °C; at this temperature its effect is basically uniform with strength decreasing rapidly. 3) The failure type of granite is a brittle tensile fracture at temperatures below 800 °C which transforms into plasticity at temperatures higher than 800 °C and crystal formation takes place at this time. Chemical reactions take place at 1200 °C. Failure of granite under high temperature is a common result of thermal stress as indicated by an increase in the thermal expansion coefficient, transformation to crystal formation of minerals and structural chemical reactions.