Temperature and strain rate dependence of frozen fine-grained rock infilling: Implications for permafrost slope stability

There has been a notable increase in rock slope instability and failure in permafrost regions, a trend that has coincided with, and is expected to intensify under, ongoing climate change. One of the key mechanisms driving this instability is the mechanical weakening of warming permafrost, including the degradation of frozen joint infilling materials. Despite its importance, the failure behavior of frozen joint infillings has been studied in only a limited number of experimental investigations, particularly with respect to temperature and strain rate dependence in fine-grained frozen soils. This study addresses that gap by examining the mechanical behavior of a fine-grained silica soil (Sil-Co-Sil 106) subjected to varying temperatures and strain rates to better understand the implications of permafrost degradation on slope stability. A series of uniaxial compression tests were performed at three temperatures (−20 °C, −10 °C, and − 1 °C) and three strain rates (2 %/min, 20 %/min, and 280 %/min).

Key results show that lower temperatures and higher strain rates significantly increase the uniaxial compressive strength (UCS) and lead to more abrupt post-peak stress loss. The elastic modulus also increases with decreasing temperature and higher strain rates. In contrast, the Poisson's ratio rises with slower strain rates and warmer temperatures, indicating increased susceptibility to volumetric strain. Additionally, specimens tend to yield at lower stress levels under high strain rates and elevated temperatures, pointing to reduced resistance to deformation. Crack propagation analysis revealed that higher strain rates produce larger crack angles, suggesting enhanced intergranular friction, while lower temperatures are associated with smaller crack angles, indicative of more brittle behavior. Together, these findings underscore the importance of accounting for both rheological (rate-dependent) and thermal effects in the geotechnical design of infrastructure in cold regions. As permafrost degradation accelerates, understanding the mechanical response of frozen joint infilling becomes crucial for developing resilient engineering solutions and adapting infrastructure in vulnerable, high-risk permafrost environments.