The effect of thermal fatigue in a limestone—a laboratory study

摘要

The environmental conditions can play an important role in the stability of rock massifs. In fact, in several cases the weather-induced mechanisms have been considered as the triggering factor of rock instabilities. Different researches have demonstrated that daily temperature fluctuations can generate internal stress; high enough to create and propagate cracks in the most superficial zone of rock cliffs. However, the aspects of thermal fatigue and thermo mechanical phenomena occurring near the surface of a rock mass (air-rock interface)—as a result of cyclical thermal variations associated to natural climatic conditions—are little documented. Our work presents a laboratory study, in order to estimate the effect of the temperature cycling in a limestone subjected to recurrent rockfalls. To observe the role of cyclic thermal variations, samples were submitted to 6 cycles between 10°C and 50°C each day. The effect of these cycles was evaluated with different methods such as: elastic wave propagation velocity or deformation. The experiment lasted five months, which corresponds to more than 900 thermal cycles. The experimental device and first results are presented here.