Deformation and failure of the talus slope in the cold region significantly threaten engineered structures. Its driving mechanism of the deformation process is the most challenging issue. In this study, we try to explore these issues using tree ring characteristics. Fifty samples from 21 trees of Pinus densiflora growing on the talus slope in the Huanren area of Northeast China are tested to investigate the characteristics of tree rings and their relation to climate change. The deformation and its driving mechanism of this talus slope are then studied by combining the analysis of tree-ring width and mutation identification with the local meteorological data. The results present that the studied talus slope in Huanren has deformed to varying degrees at least 60 times since 1900. It is reasonable to speculate that the deformation mode of this slope is probably of a long-term and slow type. The local precipitation and seasonal temperature difference are the vital inducing factors of the mutation of tree-ring width and slope deformation. Repeated freezing and thawing are believed to be the driving factors of this talus slope in the cold region. A theoretical model is proposed to capture and predict the deformation of the talus slope. This work presents a new perspective and insight to reveal the deformation and its driving mechanism of similar talus slopes in the cold region. It is of great significance to practical engineering treatment and disaster prevention for this kind of cold region environment.

In deglaciating environments, rock mass weakening and potential formation of rock slope instabilities is driven by long-term and seasonal changes in thermal- and hydraulic- boundary conditions, combined with unloading due to ice melting. However, in-situ observations are rare. In this study, we present new monitoring data from three highly instrumented boreholes, and numerical simulations to investigate rock slope temperature evolution and micrometer-scale deformation during deglaciation. Our results show that the subsurface temperatures are adjusting to a new, warmer surface temperature following ice retreat. Heat conduction is identified as the dominant heat transfer process at sites with intact rock. Observed non-conductive processes are related to groundwater exchange with cold subglacial water, snowmelt infiltration, or creek water infiltration. Our strain data shows that annual surface temperature cycles cause thermoelastic deformation that dominate the strain signals in the shallow thermally active layer at our stable rock slope locations. At deeper sensors, reversible strain signals correlating with pore pressure fluctuations dominate. Irreversible deformation, which we relate with progressive rock mass damage, occurs as short-term (hours to weeks) strain events and as slower, continuous strain trends. The majority of the short-term irreversible strain events coincides with precipitation events or pore pressure changes. Longer-term trends in the strain time series and a minority of short-term strain events cannot directly be related to any of the investigated drivers. We propose that the observed increased damage accumulation close to the glacier margin can significantly contribute to the long-term formation of paraglacial rock slope instabilities during multiple glacial cycles.