# Viscosity of Clayey Soils: Experimental Studies
## 1 Introduction
The authors of this paper have validated this model based on the results of laboratory tests on frozen sand. Tests were carried out on sand samples with different particle size distribution and density in dry conditions and at different levels of shear stress and temperature. A model reflecting the nonlinear rheological characteristics of swelling soils was proposed in [23]. The results of the performed studies showed that the proposed model well describes the viscoelastic-plastic creep deformation of the swelling soil, and the results of the analysis of this model were close to the results obtained from the performed laboratory tests of the soil in triaxial compression devices. A viscoplastic model that is capable of describing creep and plastic deformation of rock during loading-unloading cycles was proposed by [PERSON] et al. [24]. The authors of this paper performed a validation of this model based on the results obtained from triaxial tests. A seven-component rheological model to describe the behavior of weak soil with organic matter content under different loading conditions was proposed in [25]. The model used parallel three-element components to describe the viscosity, plasticity, and elastic deformation of the soil over time. The results of scientific studies of rheological properties of sandy soils are presented in the work of [PERSON] et al. [26]. The authors performed experimental studies to determine the viscosity of sandy soil by performing triaxial tests in kinematic and dynamic loading modes. The paper also considers the problem of evaluating the effect of dynamic loads on the viscosity of sandy soils. A three-dimensional elastic viscoplastic state model that is capable of describing the behavior of soils with isotachy viscosity in time was proposed in [27]. The authors of the paper gave a rather detailed description of their model and its basic equations, as well as performed the implementation of this model in a software package using the finite element method. The model was then used to simulate the results of laboratory tests, paying particular attention to the advantages and disadvantages of the model in reproducing the behavior of soft clays over time. Studies of clay soils containing the clay mineral montmorillonite, which has pronounced creep and swelling properties, were presented by [PERSON] and [PERSON] [28]. Based on the data of experimental studies of clayey soil samples consisting of a mixture of bentonite and silica sand, the authors proposed a one-dimensional elastic viscoplastic model that takes into account both creep and swelling of clayey soil. Based on the above, we can conclude that in order to describe the rheological properties of clayey soils, various methods are now widely used, which are based on the use of mechanical models, the theory of plastic flow and hereditary creep, etc. Based on these, various equations of state are derived, containing several parameters (depending on the model under consideration, the number of determined parameters will change), which can be determined during experimental studies of soil using various instruments. One such device is the simple shear device. The deformation conditions of the soil specimen in simple shear tests are very similar to the deformation conditions occurring at the base of a number of structures (e.g., soil adjacent to the side of a pile, slope deformations of soil massifs, etc.). The study of rheological properties of soils in conditions of simple shear is currently quite relevant because it allows the consideration of the processes occurring in time in the soil mass, which is an important component in the design of various buildings and structures. The test in a simple shear device can be characterized as follows: a process in which sliding (displacement) occurs along planes parallel to the plane of a stationary stamp (upper or lower, depending on the design of the device) at a value close to their distance from this plane.