Seasonal bedrock temperature oscillations and inversions as a function of depth and the implications for thermal fatigue

Abstract

ABSTRACT Research was undertaken to assess the influence of aspect and sub-surface depth on thermal fatigue in bedrock. Contact temperatures were recorded at depths of 0.3 m, 2.0 m and 6.0 m in boreholes drilled on three aspects of a tillite outcrop from mid-winter to mid-summer. Results showed that seasonal temperature oscillations of up to 20 ºC occurred in bedrock and that heat dissipation and build-up do not commence or cease at the same time throughout the rock mass, conceptually resulting in lateral and vertical thermal strain. Critically, thermal fatigue at depth may induce micro-cracking in bedrock, well before surface-related weathering processes or mechanisms commence.