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.

Direct shear creep tests have scarcely been used for long-term creep behavior studies of landslides in the Three Gorges reservoir area. In this study, based on field investigations and monitoring of the Huangtupo Landslide, direct shear creep tests were performed on the sliding zone soil of Riverside Slump #1, and the creep characteristics of sliding zone soil after varying cycles of reservoir water level fluctuation were studied. Using the creep results, the Mohr-Coulomb parameters were obtained by numerical simulation, and the deformation pattern of the reservoir landslide was analyzed. The results show that the direct shear creep of sliding zone soil can mainly be divided into stages of attenuation creep and steady-state creep. Under the same shear stress, with the increase of loading-unloading cycles N, the soil's strain and shear strain rate in the sliding zone decreased accordingly, and the long-term strength gradually improved. As the shear stress increases, the shear strain rate increases and the creep of the soil in the sliding zone has an obvious time effect. Our numerical simulation results showed good agreement with both the landslide deformation monitoring data and direct shear testing data. The Burgers model is suitable for describing creep deformation of landslides under fluctuating reservoir water levels. Under high shear stress, the fitted curve showcased both attenuation and constant velocity characteristics. Numerical simulation and burger model can reflect the direct shear creep test characteristics well. These research findings can provide an important reference on the creep characteristics of landslides, potentially aiding geotechnical engineering applications.

Take the reservoir landslide as an example, in addition to hydrological conditions, creep properties of soils play an important role in explaining the mechanisms behind landslide movement. Although the change of this deformation over time is small, the long-term accumulation will also bring new hidden danger to the safety control of the slope. This paper takes the shallow coarse-grained soils of Qiaotoubei landslide as the research interest, improves the test method for the deficiency of not allowing the lateral deformation of the specimen in the traditional one-dimensional compression creep test, and conducts the compression creep test of coarse-grained soils by using the modified high-pressure consolidation instrument. Based on this test data, the creep property of coarse-grained soils is analyzed and a suitable creep constitutive model is selected, that is generalized Kelvin model. Then, relevant parameters are determined and FLAC3D software is used to simulate the creep deformation of the slope deposits and the stress and deformation of the lattice beams. Finally, the coupling mechanism between coarse-grained soils creep and lattice structure was analyzed based on the comparison of the calculated results with the deformation or damage in the field. Through this study, some targeted suggestions and directions for future research are proposed for the management of reservoir deposit landslides, hoping to contribute to the operational safety of the reservoir.

The large number of fissures developed in loess affect the creep mechanical properties of the soil body, easily triggering geologic disasters such as loess landslides. To gain a comprehensive understanding of the creep characteristics of fissured loess, we used the undisturbed loess from the landslide group in the Heifangtai area of Gansu Province, China, to conduct triaxial creep tests under various prefabricated fissure angles (without fissure, 30 degrees, 45 degrees, 60 degrees, and 90 degrees) and different matric suction conditions. The stress-strain-time characteristics of fissured loess are analyzed, and the long-term strength variation law of fissured loess is determined. The deterioration effect of loess fissures is revealed, and the creep deformation characteristics of fissured loess samples (FLS) are explored. The results show that: (1) The deviatoric stress, confining pressure, and matric suction significantly affect the creep deformation of fissured loess and the duration for the sample to attain steady-state creep. (2) The fissures have a pronounced deteriorating effect on the long-term strength of loess. As the fissure angle increases, the long-term strength of the loess sample initially decreases and subsequently increases, exhibiting a V shaped variation, while the cohesion demonstrates a comparable V shaped variation. (3) The deterioration coefficient of the fissure initially rises and subsequently declines with increasing confining pressure. (4) The creep deformation characteristics of FLS are categorized into axial deformation, bending deformation, and torsional deformation. Generally, the fissure angle affects the axial strain of the sample; however, an increase in confining pressure weakens the influence degree of the fissure on the deformation. The findings provide new insights into theoretical support for the study of loess mechanics and deformation characteristics in the Loess Plateau region of China. This is significant in elucidating the effect of fissures on the occurrence and development of loess landslide disasters.

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.

The residual soil on a slope can slowly move downward under the influence of gravity, forming a creep landslide. These types of landslides are known for their extensive coverage, significant magnitude, and prolonged duration of hazard. A systematic study of the creep properties of creep landslide geotechnical bodies is essential for the analysis of the deformation process and long-term safety evaluation of landslides. This paper focuses on studying a creep landslide involving residual soil in western Henan Province. The creep characteristics of residual soil with different stone content are investigated through direct shear creep experiments. The findings reveal that stone content has a profound impact on the creep behavior of residual soil. As the stone content of the soil increased, the structure of the test soil changed significantly, resulting in a gradual decrease in its shear creep. The Burgers model can effectively fit the deceleration creep and steady-state creep stages of the residual soil. With the increase in stone content, the four parameters of the Burgers model show a significant increase, with the instantaneous elasticity coefficient G1 and the viscosity coefficient eta 1 experiencing more noticeable changes. The average long-term strength of specimens with different stone content is only 54% of their instantaneous strength. Additionally, as the stone content increases, the ratio of long-term strength to instantaneous strength also increases. Notably, the long-term strength of specimens with 10-30% stone content is significantly lower than that of specimens with 50-70% stone content.

Direct simple shear test is an effective method to measure strength and deformation properties of soil. However, existing direct simple shear apparatus have some shortcomings. The paper has developed a novel dual stress/strain-controlled direct simple shear apparatus. The novel apparatus has the following advantages: A rectangular specimen is used that effectively avoid common issues associated with conventional cylindrical specimens, such as specimen tilting. The utilization of deformation control rods ensures a uniform shear deformation of the specimen. Vertically integrated force transmission structure is improved that avoids issues arising from changes in pivot points due to lever tilting. Incorporating this novel direct simple shear apparatus, shear strength and shear creep tests of clay were performed. Shear strength parameters and shear creep behaviors are analyzed. The results of these experiments show that the novel apparatus can measure accurately the shear rheological properties of soil. This study provides strong guidance for studying the mechanical properties of soil in engineering practice.

In order to understand the influence of sand content on the secondary consolidation behavior of sand-fine mixtures, a series of one-dimensional creep tests were conducted. These tests used mixtures with sand contents of 0%, 16.67%, 28.57%, 50%, and 60% and were run for 3,000 min. As the sand content increases, the structure of the mixtures transitions from being fine-supported to sand-supported. This results in changes in the time at the end of primary consolidation (TEOP), the proportion of secondary consolidation deformation in the total deformation (PCT), and the coefficient of secondary consolidation. These parameters decrease before the sand content reaches 28.57% and increases after this point. The sand-fine mixtures with a sand content of 28.57% exhibit the minimum TEOP, PCT, and coefficient of secondary consolidation. When the sand content is less than 28.57%, bound water (especially weakly bound water) significantly impacts the secondary consolidation behavior of the sand-fine mixtures. However, when the sand content exceeds 28.57%, the secondary consolidation deformation of the mixtures is primarily governed by particle crushing in the sand grains.

Creep is one of the typical mechanical properties of clay, and studying the creep mechanical properties of clay is of great significance to construction projects in clay sites. This study conducted creep tests on Chengdu clay and found that the soil mass underwent elastic deformation, decay creep deformation, steady-state creep deformation, and accelerated creep deformation. The isochronous stress ratio-logarithmic strain curves and their mathematical models were proposed to thoroughly analyze clay creep mechanical properties. Creep automatic feature points, such as linear elastic extreme point, initial yield point, long-term strength point, and plastic point, were identified on the curve. Considering the hardening and damage effects during creep loading, linear elastic and viscoelastic elements considering the time-dependent damage, a viscoplastic element considering the load hardening effect, and viscoplastic and plastic elements considering the load damage effect were established based on the element model and the Riemann-Liouville fractional derivative. Based on the mechanical properties of the whole clay creep process, the creep mechanical feature points, and the established element model, a clay creep model was proposed considering the hardening and damage effects. The rationality and regularity of the creep model were verified using the creep test data. This research accurately revealed the creep mechanical properties of clay and facilitated soil deformation prediction, thus providing technical guidance and references for construction projects in clay sites.