Rheological studies of soils were carried out by S.S. Vyalov, M.N. Gol’dshtejn, N.N. Maslov, G.I. Ter-Stepanyan, S.R. Meschyan, A.L. Gol’din, Z.G. Ter-Martirosyan and many others. On the basis of existing rheological soil models, a new universal rheological equation was proposed in Ter-Martirosyan’s dissertation, which allows describing kinematic shear, creep and stress relaxation at the same parameters. Experimental studies of the soil were carried out in a simple shear device in a kinematic loading mode at a shear displacement rate u̇= 0.05 mm/min and at two values of compaction loads (σ1 < σ2). Based on the results of the experimental studies, the parameters of the elastoviscoplastic model were determined and graphs of the dependence of shear stresses on time were plotted, which clearly show the high convergence of the experimental and theoretical curves.

A large number of scientific works by both Russian and foreign authors are devoted to the interaction of a single pile with the surrounding and underlying soils. Based on experimental, numerical and theoretical studies, various methods, approaches and solutions have been obtained in scientific works, which make it possible to most correctly predict the settlement and bearing capacity of a single pile. Research in this area is relevant, since the determination of the settlement of the pile, as well as the study of the mechanism of distribution of the load transmitted to it, play an important role in the design of pile foundations. In this work, the boundary value problem of the interaction of a long and incompressible pile with the surrounding and underlying soils in an elastic-viscous formulation, taking into account soil strengthening, was solved, based on the Maxwell model, as well as on the basis of the rheological model of A.Z. Ter-Martirosyan. This study presents a detailed course of solving the boundary value problem, as well as the basic formulas for calculating the settlement and long-term bearing capacity of a single pile. The change in the curve of dependence σ R ( t ) at different values of soil viscosity is shown when solving the problem in an elastic-viscous formulation. An additional graph of σ R ( t ) dependence is presented showing the difference in the presented soil models. Based on the plotted graphs of the dependence of σ R ( t ) when solving the problem in an elastic-viscous formulation, it can be concluded that the time to reach the maximum value of the load under the foot of the pile is directly proportional to the value of the soil viscosity. When solving the problem on the basis of the rheological model A.Z. Ter-Martirosyan, the maximum value of the load under the foot of the pile is reached earlier than when solving the problem in an elastic-viscous formulation both with and without soil strengthening, which requires additional study.

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At present, numerical methods of calculations, which are implemented in a large number of software complexes, are widely used in geotechnical practice and the definition of input parameters of the ground is very important and necessary to reflect the real work of the foundation of geotechnical structures [1-4]. There are often cases when the results obtained during laboratory tests of soils are not accepted by software complexes, errors are given, recommendations are proposed for changing the parameters in the direction of increasing or decreasing. In connection with these problems, the question arose about the need to optimize soil parameters obtained as a result of laboratory tests to compare and correct these parameters, based on the degree of approximation of model tests with laboratory tests [5]. Optimization of soil parameters can be carried out in the subroutine Soil test, incorporated in the PLAXIS geotechnical software [6]. Using the Soil test, the triaxial and compression tests are simulated based on the input parameters of the soil and the initial test data. The purpose of this study was to describe the methodology for optimizing the parameters of the Hardening Soil model and the Soft Soil Creep model using the PLAXIS 3D software geotechnical complex, as well as a comparative analysis of the results of laboratory soil tests with modeling results in software complex.

The article presents the issue of correctly calculating the SSC of the foundation bases in the process of compensation grouting. It is shown that the numerical calculation should be performed in two versions: hydrostatic pressure and rear volume strain in a cluster of soil. Using the example of an object in Moscow, the use of the PLAXIS 3D design complex was shown to calculate additional precipitation of buildings during compensation grouting and the passage of a tunnel under it. A method is given for determining the required volume of suspension during compensation grouting using numerical methods for calculating the SSC.