Microstructure of frozen soils under the influence of static loads and temperature changes

The present study is devoted to the investigation of the microstructure and macrostructure of frozen soils under the influence of static loads and temperature changes. Particular attention is given to analyzing microstructural changes in various types of frozen soils—namely, alluvial sands, sandy loams, and marine loams—during prolonged mechanical testing under subzero temperature conditions. The aim of the work is to identify the features of ice inclusion formation, cryogenic textures, the distribution of ice-cement, and the deformation processes within the soil structure. The study is based on original data, enabling detailed analysis of the spatial distribution of mineral particles and ice inclusions at the microscopic level. The research focuses on identifying deformation patterns in frozen soils associated with changes in their microstructure, which has practical significance for engineering geocryology and for forecasting the stability of structures in permafrost regions.To analyze the microstructure, methods of polymer replicas and scanning electron microscopy (SEM) were used. Approximately 150 replicas were prepared before and after mechanical tests (uniaxial compression, shear, and frost bonding) on four types of frozen soils under varying temperature and moisture (ice content) conditions. The scientific novelty of this work lies in the comprehensive application of the polymer replica method and SEM for detailed analysis of microstructural changes in frozen soils in their natural frozen state after prolonged loading. Unlike previous studies, which mainly examined thawed samples or used less stable methods, this research employed replicas made directly from the fracture surfaces of frozen samples, which preserved ice inclusions and allowed for high-quality comparative analysis before and after testing. It was found that static loads lead to the formation of cellular structures, intersecting ice lenses, ring-shaped formations around ice-cement, and microcracks that significantly alter the microstructure. Macrostructural changes were also recorded in the form of compaction zones, loosened areas, and cracks, which correlate with the observed microstructural transformations. The influence of temperature, moisture (ice content), and salinity on the degree of microstructural change was demonstrated. A close relationship between the microstructure and the mechanical properties of frozen soils was experimentally confirmed. The data obtained allow for refinement of models describing the deformation behavior of frozen soils.