In cold regions, the strength and deformation characteristics of frozen soil change over time, displaying different mechanical properties than those of conventional soils. This often results in issues such as ground settlement and deformation. To analyze the rheological characteristics of frozen soil in cold regions, this study conducted triaxial creep tests under various creep deviatoric stresses and established a corresponding Discrete Element Method (DEM) model to examine the micromechanical properties during the creep process of frozen clay. Additionally, the Burgers creep constitutive model was used to theoretically validate the creep deformation test curves. The research findings indicated that frozen clay primarily exhibited attenuated creep behavior. Under low confining pressure and relatively high creep deviatoric stress, non-attenuated creep was more likely to occur. The theoretical model demonstrated good fitting performance, indicating that the Burgers model could effectively describe and predict the creep deformation characteristics of frozen clay. Through discrete element numerical simulations, it was observed that with the increase in axial displacement, particle displacement mainly occurs at both ends of the specimen. Additionally, with the increase in creep deviatoric stress, the specimen exhibits different deformation characteristics, transitioning from volumetric contraction to expansion. At the same time, the vertical contact force chains gradually increase, the trend of particle sliding becomes more pronounced, and internal damage in the specimen progresses from the ends toward the middle.

Upon completing large-area layered filling, the foundation soil exhibits transverse isotropy and is predominantly. unsaturated, making post-construction settlement prediction challenging. Additionally, the creep model considering transverse isotropy and unsaturated characteristics has not been proposed. Therefore, the true triaxial apparatus for unsaturated soil was enhanced, and transversely isotropic unsaturated loess samples were prepared. The relationship between matrix suction and moisture content at various depths in transversely isotropic unsaturated loess was determined using soil-water characteristic curve tests. The creep characteristics of loess fill under varying moisture content, degree of compaction, deviatoric stress, and net confining pressure were examined using a consolidation drainage test system. According to the creep curve, the expressions for six parameters in the modified Burgers element model were determined, establishing a post-construction settlement prediction method for transversely isotropic unsaturated loess fill foundations. The results show that the transversely isotropic unsaturated loess exhibits distinet creep characteristics, primarily nonlinear attenuation creep. The degree of compaction, moisture content, deviatoric stress and net confining pressure significantly affect its creep characteristics. Creep stability strain is linearly related to the degree of compaction. Enhancing soil compaction can effectively reduce post-construction settlement of the fill foundation. A prediction algorithm based on the modified Burgers model, which reflects the influence of degree of compaction, moisture content, and stress level, and accurately describes the post-construction settlement behavior of transversely isotropic unsaturated loess fill foundations, is established. Actual engineering monitoring results demonstrate that the proposed settlement prediction algorithm is simple, practical, and effective. The research results can enrich and advance the creep model of unsaturated soil, and provide a scientific basis for solving the problem of deformation calculation of high fill foundation.

Cement reinforcement can effectively mitigate the frost heave and thaw settlement in soft clay during artificial ground freezing. Generally, soft clay has strong creep characteristics, which is also the main factor influencing the construction safety in coastal area. However, the mechanism of freeze-thaw action with cement reinforcement on the creep is really unclear. In this paper, the creep characteristics of cemented-soil after freeze-thaw have been investigated through triaxial creep test, and the micro-mechanism has been explored by Scanning Electron Microscopy (SEM) test and PFC numerical simulation. Three quantitative parameters of porosity, average particle size, and particle roundness have been extracted from SEM pictures. The results showed that creep deformation of cemented-soil is higher after freeze-thaw than before, with an increase as the freezing temperature drops. When combining freezing with cement reinforcement, there is an overall decrease in the creep behavior. It was observed from numerical simulation that the slip deformation of cemented-soil particles is generated from top to bottom and from outside in. Moreover, the porosity of cemented-soil increased from 24.5 to 28.5%, the particle roundness decreased from 2.11 to 1.75, while average particle size decreases from 16.67 to 13.88 mu m during creep process. These shifts are explained by particles sliding and disordering, with debris migrating to the interior of pores. The results provide a scientific reference for the development of underground space in the coastal area.