Study of creep in frozen soils using various deformation models

The subject of the study is the long-term creep of frozen clay soils at negative temperatures. Unlike most previous works based on short-term tests, this study implements an approach based on long-term (8–20 days) laboratory study of the samples using the uniaxial compression method. The objects of the research are kaolin clay, alluvial sandy loam, and clay loam collected in the Marre-Sale area and Moscow. The goal is to quantitatively determine the parameters of the deformation behavior of frozen soils and to select the most appropriate model for their description. The stages of creep and the influence of structure on the rate of deformation are considered. The obtained data are compared with the results of approximating four deformation models – strengthening, power, Burgers, and Nishihara – for subsequent application in predicting the stability of engineering structures in permafrost conditions. The methodology includes long-term laboratory tests of frozen clay soils using the uniaxial compression method at a temperature of −5 °C with the use of the "IVK Mechanics-Thermophysics" complex. Six samples of kaolin clay and one sample each of sandy loam and clay loam were used. The results are approximated using four mathematical creep models. The scientific novelty of the work lies in the comprehensive experimental study of the creep of frozen soils of various compositions over an extended period and the quantitative comparison of the effectiveness of mathematical models for describing the rheological behavior of these soils. For the first time, under prolonged tests at a constant load, the experimental data were approximated using four models, which allowed for identifying their advantages and limitations. It was established that the strengthening models and the power model most accurately describe the deformation behavior of all soil types (R² " 0.99). The Burgers model shows satisfactory results but underestimates deformations in the later stages. The Nishihara model requires modification for an adequate description of the accelerated stage. The results obtained have practical implications for assessing the reliability of foundations in the permafrost zone and for improving the rheological models of frozen soils.