Changes in rock dynamic elastic moduli after thermal cycling in a controlled environment

Temperature fluctuations can influence the internal stress field of a rock mass, especially in its surficial layer. Inherent properties (mineral composition, porosity, and fracturing) and external forcing (air temperature, humidity, and solar radiation) control the heat flux and temperature within the rock. Long-term thermal forcing, particularly when combined with wetting-drying cycles, can exacerbate rock deterioration and weathering, leading to progressive changes in mechanical properties, as shown by laboratory experiments.

In this study, granodiorite samples from the Požáry field laboratory (Central Czechia) were subjected to thermal cycling in a controlled environment of a climate chamber, with repeated and increasing cycles reaching 80°C, a temperature that was most probably never reached after the rock´s formation.  During the cycling, repeated UPV measurements were made (P and S waves) to observe the changes in their velocity and the inferred dynamic elastic moduli.

The results showed slow but progressive decrease in the P and S wave velocities, suggesting rock damage after only a few cycles. This indicates possible increased rock wear in case of an expected future temperature rise.