Deciphering the sensitivity of rock faces to climatic changes and freeze-thaw cycles in permafrost-free regions

The proposed research project aims to decipher the sensitivity of rock faces to climatic changes and freeze-thaw cycles in permafrost-free regions. Climate change is an increasing problem nowadays, as air temperatures are rising and heavy rainfall events are increasing, which can lead to rockfalls not only in high mountain regions but also in permafrost-free areas. Rockfalls are caused by preparatory processes (weathering and crack propagation) that gradually degrade the rock, and triggering processes (freeze-thaw activity, precipitation events, earthquakes, snow avalanches, animals, or anthropogenic activities) that eventually release a rock block. Several physical mechanisms may be involved that can manifest as rockfalls triggered by a slide or fall. For example, when daytime temperatures are high, water in the joints undergoes periodic freeze-thaw cycles. The periodic freeze-thaw cycles cause continuous expansion of the joint cracks, leading to failure of the rock mass. Because rockfalls occur suddenly and usually without visible warning signs, they are extremely difficult to predict and pose a great potential hazard to people and infrastructure. This research project focuses on investigating freeze-thaw cycles and rainfall as long-term preparatory factors for rockfalls in permafrost-free regions. In permafrost-free regions, theoretical and experimental understanding of increased rockfall activity as a consequence of climate change is poorly studied. Therefore, to determine the sensitivity of rock faces to climatic changes and freeze-thaw cycles in permafrost-free area, the following key parameters are considered: engineering geological conditions at the source of rock faces, geotechnical monitoring, and climate change scenarios. These parameters will be analyzed and modeled in two selected pilot areas where rockfall events occur daily and cause large economic and material losses. To achieve this objective, we will use a multi-method approach consisting of experimental in-situ measurements, observations and monitoring that will allow us to determine the initial state of rock instability, the associated rockfall volume and frequency, and the near-surface rock temperature. This will be accompanied by numerical modelling and simulations using the finite element method to estimate the accumulation of damage and the evolution of stress and temperature fields due to changes of ambient temperature and freeze-thaw cycles in the rock face. Based on the study of two different rock types and their predisposing factors, which often determine the susceptibility to fracture formation, the project results will provide a fundamental basis for the development of a methodology for rockfall risk management and the definition of mitigation measures and early warning actions. The results of the proposed project will also fill the gap in scientific research on the identification of climate change impacts in permafrost-free regions, which are rarely the subject of scientific studies. At the same time, the proposed multi-method approach will be transferable to the other rockfall prone areas.