Abstract
Climatic actions are one of the factors controlling the evolution of slopes, this paper is devoted to a specific effect, relatively little studied, related to the effect of climate-driven temperature changes on rock massif deformation. The particularity of the study is to focus on permeable rocks and Temperatures varying in a range which discards freeze/thaw effects. Research has been carried out in relation with the analysis of the real case of a limestone cliff located in the Périgord region, the massif was highly instrumented, results show a slow cyclic accumulation of deformations with time, essentially synchronic with thermal cycles. An advanced constitutive model, specifically developed to capture rock degradation due to the differential expansion of the main minerals composing the rock, has been developed. It has been calibrated on experimental results obtained in the laboratory on block samples tested in a climatic chamber for a long series (several months) of daily thermal cycles. Deformation and shear wave velocity were monitored during the test. Model shows a good agreement with laboratory measurements.
Highlights
Under cyclic changes in temperature, rock massifs experience expansion/contraction cycles that cause continuous stress redistribution in the zone of propagation and retrieval of the heat front
Because the amplitudes of temperature changes under climatic actions are moderate and it is generally considered that their maximum and minimum values were already reached during rock slope history, stress changes are in most cases expected to produce recoverable deformations
In order to reduce the number of parameters to estimate, it has been considered that mineral phase 1 and 2 are provided with the same thermal expansion coefficient
Summary
Under cyclic changes in temperature, rock massifs experience expansion/contraction cycles that cause continuous stress redistribution in the zone of propagation and retrieval of the heat front. Mineralogical analyses indicated that samples obtained from the felt block were mainly composed by calcite, while samples drilled from the cliff presented a composition of almost 50/50 of calcite and quartz This suggests that damage could be enhanced by the presence of two mineral phases in same amount within the rock, as the result of the development of internal stresses due to differential thermal expansion of calcite and quartz grains. Another illustration of the same effect is presented, which shows the evolution of the bulk modulus K with the number of thermal cycles (for comparison purposes, K is normalized by its initial value K0). Different volumetric strains can be defined: Internal volumetric strain d vint (change in pore volume by unit volume of material) Volumetric strain of mineral phase 1
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