Rock instabilities can represent major risks for local populations depending on their geographical location. Even if different factors such as precipitation, seismic activity and freezing, are known to trigger rockfalls it is more and more assumed that thermal cycling have a role in cracking initiation or propagation. Here we use data of the first six years of field monitoring of a 50-meter-high French dolomitic cliff, located above an important highway in the south of France (A75) to support this thinking. Evolution of the aperture of joints and temperature were followed on ten different locations around les Chandelles de l’Escalette. Results will be discussed in terms of mechanical response to temperature variations.
The effect of natural thermal cycles on the mechanical behaviour of rocks has been investigated for a decade. Collins & Stock (2016) is often considered as the first important work on this effect, but it is forgetting the work of Gunzburger et al. (2005) and Bakun-Mazor et al. (2013) for instance who worked on the mechanical formulation of thermal effects and, even earlier Hall (1999), Vargas et al. (2009) or Gasc-Barbier et al. (2015) who proposed geomorphological analysis.
Most of the above-mentioned sites were monitored on small, local areas. In les chandelles de l’Escalette, eleven crackmeters and temperature sensors were positioned along 50-meter-high dolomitic columns to understand the overall movement of the rock columns and the associated hazard.
Les chandelles de l’Escalette are located in the south of France (see insert in figure 1) just above an important highway. They correspond to the southern part of the Larzac plateau. Eleven pairs of sensors were placed: each red point in figure 1 corresponds to a crackmeter. Temperature of the crackmeters is always recorded, except for B8. Along each important fracture two pairs of sensors were positioned, one at the bottom (B sensors) and one near the top (H sensors). All crackmeters are horizontal, expect V8, which is vertical and located just near B8 (only one red point corresponding to B8 and V8 in figure 1).
