A comparison of the calculation results of the foundation pit enclosure made of flexible retaining walls is presented. Calculations were performed by the method of numerical modeling using Plaxis PC software, which is based on the finite element method. This task was implemented in three-dimensional (3D) and flat (2D) formulations of the problem, which provides more opportunities for a comprehensive assessment of the stress-strain state (SSS) of the elements of the "soil massif - anti-landslide structures" system when using complex configurations retaining walls. Calculations were performed within three calculation sections for different stages of construction: 1st stage – the initial faze (formation of the soil massif in its natural state), 2nd stage – excavation of the first layer of the pit, 3rd stage – excavation of the second layer of the pit. Based on the results of the calculations, the SSS analysis of the elements of the "soil massif - anti-landslide structures" system was carried out and the reinforcement of the retaining walls was selected. An assessment of the slope stability was also performed at the stage of full excavation of the foundation pit. It is shown that the advantage of using a plane FEM to assess the stress-strain state in the anti-slide structures is a much smaller amount of time spent on calculations and ease of understanding, but the disadvantage of this method is the lack of the possibility of taking into account the spatial stiffness of structures. It has been demonstrated that the use of spatial FEM allows taking into account the spatial stiffness of structures, which in the future makes it possible to more effectively design the retaining walls structures, however, modeling using this method is quite labor-intensive and requires significant resources of computer equipment for making calculations. According to the results of the calculations, the displacements obtained in the calculation using 2D modeling are on 6-43% more than using 3D modeling, the bending moments are on 12-33% more.

Comparison of the results of assessment of the of slope stability to determine the feasibility of construction of retaining structures is presented in this paper The construction of a grain terminal on a landslide slope in the Odessa region was selected as the object of researching. The building area belongs to the Black Sea basin region and is located on the southwestern slope of the Ukrainian Crystal Shield. The uneven stepped surface of the crystalline basement consists of blocks. Despite the significant irregularities of the crystalline basement, they are reflected in the relief through the sedimentary cover. To ensure of the slope stability, it is planned to install a cascade of retaining structures. There are pile retaining walls. The calculations are based on the analysis of the stress-strain state of the slope and anti-landslide structures using two fundamentally different methods. These methods of calculation using modern software: - analytical method for assessing the slope stability (limit equilibrium method); - assessment of the slope stability by the method of numerical modeling of the stress-strain state of the elements of the system "soil mass - anti-landslide structures". Calculations were made for two calculated cross-sections and for different stages of construction. There are stages native state, during construction and exploitation. 1st stage is assessment of the slope stability in its natural state, before building beginning. 2nd stage is assessment of the slope stability during the construction of the 1st retaining wall and excavations of the first level of the pit; stage 3 - assessment of slope stability after construction of anti-landslide structures and excavations of the pit. Stage 4 - assessment of the slope stability at the stage of grain terminal exploitation, it is meaning the construction of foundation structures. According to the results of calculations, the slope stability safety factors were determined, the analysis of SSS elements of the system "soil mass - landslide structures" was carried out and the reinforcement of retaining walls was selected.

The effect of the pile and the soil environment modeling method on the distribution of forces in the pile foundation and its deformation was studied and analyzed. Based on the obtained results, the difference in the distribution of forces in piles and the difference in the settlement of the pile foundation was demonstrated.  A comparison is drawn between the models, in which elements of the scheme such as "base" and "foundation" were made using different methods. The zones where the peak forces are the largest and the smallest were marked. The structural scheme and geological conditions are based on the existing project, as well as engineering and geological investigations. The finite element model of the building consists of a base, underground, and above-ground structures. A linear-elastic model with the following soil parameters was used to simulate the work of the base: E – modulus of elasticity; V – Poisson's ratio; as well as the elastoplastic Mohr-Coulomb model, in which the soil is defined by the following parameters: E – modulus of elasticity; V– Poisson's ratio; c – cohesion; φ is the friction angle. The calculation was performed with the help of the LIRA-SAPR 2017 software complex. In order to improve the accuracy of the calculation of the results, the identification of the parameters of the base was carried out, where the results of in-situ test piles for static indentation were used as the initial data. The soil parameters, which were obtained in the result of identification, were applied to the model of the soil environment in the calculation scheme. As a result, it is possible to assess the influence of the identification parameters on the change in the stress-strained state (SSS) of the foundation structures as well as compare the forces values in piles and the deformation of the foundation before and after the identification. With the development of technologies and software complexes, the number and variability of calculation methods were increasing, as well as the variety of calculation models. Each calculation model is unique and created with a certain goal – to make the calculation results closer to the real work of foundation structures. It is necessary to make the most effective and rational modeling method to achieve the goals set, as well as to obtain a quick and accurate result.

An important issue in the calculations of retaining structures of pits and their interaction with the foundation and existing structures is taking into account the features of their installation technology. Quite often, during calculations, this factor is ignored or taken into account by introducing correction factors, which are somehow based on the statistical processing of observation data during the construction of similar objects. The development of numerical methods has enabled designers to use detailed finite-element models in calculations to more accurately predict the behavior of bases and structures, without spending excessive amounts of time. In this work, numerical modeling methods are used to reproduce the process of installation of the pit enclosure structures using the trench method "wall in soil" to determine its impact on existing buildings. For this, a numerical model of a 9-floor building with a soil massif was created. Modeling of the foundation pit and enclosure structures, which is installed next to the building, was done. At the same time, the use of a three-dimensional formulation of the problem made it possible to take into account the length of the wall panel and the technological sequence of the construction. The existing methods of trench excavation modeling were analyzed and one of them was implemented in the calculation scheme. The impact of various factors on the formation of additional deformations of the existing building was investigated, such as: L - distance from the foundation pit to the building; Нст - the depth of laying the sole "wall in the ground"; Lзхв - the length of the wall panel; ρг.р - is the density of the clay slurry. Within each task, the settlement of the foundation of the building is determined with different input parameters: L={1,2; 3; 5; 10m}, Нст={12; 18; 24m}, Lзхв={3; 4; 5m}, ρг.р={1.05; 1.10; 1.30t/m3}. The results are presented in the form of graphs. The results of the research show that the most determining factors affecting the «technological settlements» of the slab foundation of the building are the distance from the pit to the building and the depth of laying the sole of the "wall in the soil". With different combinations of these parameters, the values of calculated vertical deformations of the building can differ up to several times.