Abstract ID: 3.12965 | Accepted as Talk | Requested as: Talk | TBA | TBA

Widespread permafrost degradation and glacier retreat have led to increased rock instability in many mountain regions in recent decades. However, in-situ geotechnical monitoring of bedrock deformation and stress variation remains scarce, largely due to the challenges of conducting measurements in steep, perennially frozen rock faces.
In this study, we analyze seasonal and multiannual variations in the stress regime of a warming permafrost rock slope using a unique five-year dataset (2016–2020) of loads recorded at the heads of three grouted steel anchors (25 m total length) at the Kitzsteinhorn, Central Alps, Austria. Installed in a recently deglaciated rock face below a high-alpine cable car station, these anchors function as extensometers, capturing stress fluctuations in the surrounding rock mass. The recorded load variations serve as proxies for deformation along the 18-meter free anchor length, providing insights into subsurface stress dynamics, where the effects of climate warming are often more pronounced due to reduced atmospheric influences.
During the observation period, anchor loads ranged from 350–600 kN, with strong seasonal variations of 40–125 kN (higher loads in winter, lower in summer), corresponding to strain values of 1.3–4.1 mm. Seasonal load increases correlated with negative thermal gradients in the subsurface, which drive cryosuction and ice segregation. This suggests that autumn and winter load increases result from the seasonal formation of segregated ice in the active layer, while summer load decreases are associated with the melting of ground ice. Small variations in the maximum thickness of the permafrost active layer—measured in a nearby 20 m borehole—appear to critically influence the observed load fluctuations, indicating that ice melt at the base of the active layer is a key driver of stress variation.
Additionally, anchor loads decreased by up to 24% during warm summers and only partially recovered in subsequent winters, leading to a gradual long-term load decline over the five-year period. These findings highlight the intricate link between ground temperature variations, subsurface stress redistribution, and the progressive weakening of permafrost-affected rock slopes under a warming climate.