The role of natural thermal cycles on a limestone cliff mechanical behaviour

Rock instabilities can represent major risks for local populations depending on their geographical location. Even if different mechanisms are known to trigger rockfalls such as precipitation, seismic activity and freezing, many rockfalls occur during periods when such trigger mechanisms are absent. Some recent studies have pointed out the role of thermal cycling in crack initiation or propagation. Here we use data from nearly five years of field monitoring of a French limestone cliff. Evolution of the aperture of joints were followed as well as displacements and temperature deep in the rock mass. We show that seasonal thermal variation affects the rock at depths of up to 6 m and subcritical cracking can probably appear even at this depth. •we use data from nearly 5 years of field monitoring of a perched cave in a limestone cliff•4 fissurometers were positioned to quantify the aperture of the joints, to evaluate the relative movement of the blocks•2 borehole extensometers with 3 measurements points each inform of the global behaviour of the rock mass•temperatures were measured in a cave (surface temperature) but also at 2 m and 6 m depth•seasonal thermal variation affects the rock up to 6 m deep; subcritical cracking can probably appear even at this depth