Thermal Deformation of Granite under Different Temperature and Pressure Pathways

Abstract

The thermal cracking of rocks is the phenomenon of expansion and deformation of mineral particles inside the rocks. The thermal deformation of the same granite sample under different heating pathways was meticulously analyzed, and the effect of the variation of external stress on the thermal expansion was carefully studied. The thermal deformation threshold temperature was low under triaxial stress, and a larger expansion was produced under uniaxial stress. The thermal deformation of the rock mass was found to be irreversible. Upon heating to the same temperature, the expansion was found to decrease with the increase in the number of thermal cycles. Besides, for each thermal cycle, the amount of deformation caused by cooling was always greater than the amount of deformation caused by temperature rise; this difference in deformation was especially obvious under a change from triaxial stress to uniaxial stress. In the process of elevated temperature which has the same heating rate, the thermal expansion coefficient was greater under uniaxial stress than it was under triaxial stress; under same external stress, the thermal expansion coefficient with a high heating rate was generally greater than the thermal expansion coefficient with a low heating rate.

Thermal Expansion of Triaxially Stressed Mudstone at Elevated Temperatures up to 400°C

“…ermal deformation of granite occurs in three stages: slight deformation at low temperatures (RT to 120°C) with a relatively low thermal expansion coefficient; a rapid deformation period at medium-high temperatures (120-450°C), during which the thermal expansion coefficient increases nonlinearly with increasing temperature; and slight deformation at high temperatures (450-600°C), during which time the thermal expansion coefficient decreases dramatically with increasing temperature. e thermal expansion coefficient is approximately 20 times less than the coefficient without confinement [34,35]. e coefficient of thermal expansion of water-saturated igneous rocks and limestone were also observed to increase with increasing temperature at all pressures [36,37].…”

Elastic modulus evolution of triaxially stressed mudstone at high temperature up to 400°C

“…Whereas our previous studies had indicated that igneous rock such as granite experienced nonmonotonal variation of elastic modulus, permeability, and thermal expansion when they were subjected to high temperatures up to 600°C and high triaxial stresses. [36][37][38][39][40] Hence, the mechanical behavior of mudstone is more complicated at high temperatures while under triaxial stress than after high-temperature treatment alone.…”