Resumen de Effect of thermal cycles on rock massif stability

Claudia Juliana Villarraga Díaz

• The environmental conditions may play a relevant role in the stability of rock slopes. In fact, weathering can contribute to the reduction of strength of the material, while atmospheric actions may increase internal stresses in the rock massif. This Ph.D. thesis deals with the effect of atmospheric thermal cycles in rocks, from both experimental and numerical point of view.

  This research is focused on the real case of La Roque Gageac, a small town located in the south-west of France, which experiences rock fall risks. Installed instrumentation evidenced the main role played by thermal variations in rock falls occurrence.

  With the aim of isolating the effect of thermal cycles in the La Roque Gageac limestone, an experimental study is performed. Samples were obtained from blocks felt and intact cores drilled from the cliff face. These samples were submitted to thermal cycles between 10ºC and 50ºC, in order to mimic natural variations.

  The damage induced in the samples is evaluated through measurements of strains, elastic wave propagation velocities and uniaxial compressive strength. It is observed that samples experience an accumulation in strains and reduction in the elastic wave propagation velocity and material strength during the imposition of thermal cycles. The response depends moreover on the mineralogical composition of the rock, which varies from sample to sample, as the cliff presents a large heterogeneity. Based on the results obtained in the experimental program, principal characteristics of thermal damage have been evaluated, proposing a constitutive model capable to reproduce the macroscopic mechanical response of the rock under the applied thermal cycles.

  With this purpose, a constitutive model based on the concept of composite material defined by Vaunat & Gens (2003) is developed. This model considers the material as composed of two different components endowed with their own behavior and interacting each other. This constitutive model has been implemented in the finite elements code CODE_BRIGHT and validated with the experimental results. It allows a better understanding of the internal stresses developed in the material under thermal loading.