Thermal expansion, diffusivity, and cracking of rock cores from Darlington, Ontario

Abstract

Measurements of the thermal diffusivity and expansion coefficient for rock cores of a limestone and granitic gneiss, recovered from a deep hole at Darlington Generating Station, Ontario were carried out. Results showed that the diffusivity decreases whereas the coefficient of expansion increases with temperature for both rock types. Thermal cracking occurs above a threshold temperature that is independent of the rate of heating as indicated by wave velocity measurements; this appears to be a result of thermal mismatch of the mineral constituents. These results are of direct relevance to the design of underground facilities in energy-related projects.