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During the design and operation practice, it is necessary to assess the possibility of deformation of structures located on foundations which are able to precipitate and subside. Only with reliable and accurate determination of the stress-strain state of structures of structures together with soil masses during modeling, it is possible to apply the finite element method in practice. The calculations using the PLAXIS and LIRA programs made it easier to analyze the stress-strain state of the soil mass and the stability of retaining walls: I option is corner retaining wall; II option is retaining wall with a structural surface. With the same soil base (layer geometry and physicomechanical properties), loads and boundary load conditions, it is obvious that for the II option the entire mass of soil is included in the work and the stresses are uniformly distributed over the front and foundation plates (over common stresses), uniform structural deformations are observed and soil base, which, in turn, ensures the stability of the retaining wall (according to the general picture of movements) The validity of the theoretical forecast of the behavior of engineering structures interacting with an unevenly deformed base cannot be obtained on the basis of the regulatory framework. This gap can be filled in when modeling the "base – engineering structure" system using modern calculation programs using the finite element method. 1 The problem and its relationship with scientific and practical tasks Retaining walls are now widely used not only in civil and industrial construction, but also in urban planning for complex landscapes. There are situations of construction of objects in cramped conditions, in adverse territories with active acting deformation influences, which makes the use of existing types of retaining wall structures more complicated. An important factor in solving the emerging problems is the high level of expertise on engineering and geological conditions in large industrial cities, especially in regional centers. Modern research is mainly focused on clarifying the geotechnical nature [1]. As earlier experience shows, the development of hazardous processes in urban areas continues. First of all, these are the processes of flooding in the territories, the development of landslide deformations, subsidence of the surface above mine workings, subsidence of loess soils, etc. These processes are associated with a decrease in serviceability or deformation and the destruction of buildings and structures. According to expert estimates, 90% of the territory of Ukraine is characterized by complex engineering and geological conditions, worsening due to the influence of natural and technogenic factors. As for the Kryvyi Rih city, the technogenic load on the geological environment is several orders of magnitude higher than for other adjacent cities. It should be especially noted that iron ore has been mined for about 200 years, up to 47% of the built-up territory is located in the developed space. In modern practice, the construction of facilities in cramped conditions, in areas subject to adverse physical and geological processes, complicates the use of existing types of retaining wall structures. Extremely unfavorable combinations of underworking with subsidence of soils, with flooding, etc. are encountered, therefore, in order to protect the settlements, industrial facilities, utilities and transport communications with a certain level of safety, it is necessary to use engineering structures of a special type that would perceive the influence of variables of engineering -geological, natural and technogenic factors. Building on a deformable foundation is very widespread. In recent years, as the territories that are most favourable for development have been exhausted, construction in territories with difficult conditions, which are characterized by significant uneven deformability of the base, has become increasingly widespread [2, 3]. Engineering methods of calculation, which are traditionally used in design, cannot answer all questions of operational practice. Widespread in many countries are programs based on the finite element method (FEM) [4]. These programs have a fairly wide scope and according to them it is possible to determine the stressstrain state, including structures, in the "base – engineering structure" system. 2 Analysis of research and publications Complicated engineering and geological conditions this is a geological environment that includes specific soils, hazardous natural or technogenic processes, geomorphological conditions, geological and hydrogeological factors of interaction with buildings and structures, belong to the II and III category of complexity of engineering and geological conditions [5, 6]. Many scientists have devoted their work to determining the lateral pressure of soil on retaining walls, taking into account their joint work with the soil mass. So, V. Raiuk [7, 8] investigated the nature and magnitude of the lateral pressure on the vertical face of the retaining wall, taking into account its deformation and displacement, using the model of linearly deformable half-space, but he did not consider the joint work of the vertical wall and the foundation as a single system that interacts with soil. K. Chernyshova [9] investigated the effect of the flexibility of a vertical wall on the lateral pressure of the soil. Y. Luchkovskyi [10], using the superposition method, provides a solution for determining the lateral pressure of soil on retaining walls from narrow loads and concentrated force. He draws attention to the attenuation with a deepening of lateral soil pressure from the load. However, these authors, when determining the lateral pressure, did not take into account the joint work of the vertical wall and the foundation as a single system that interacts with the base. Y. Symvulydy [11] calculates a flexible retaining wall taking into account the interaction of all its elements with the base, but introduces a linearly deformable half-plane as a model of the natural base, which is not entirely correct. In addition, this method does not allow taking into account the influence of the loading on the stress-strain state of the system. A significant amount of research has been devoted to the static calculation of retaining walls [12, 13]. The number of works on the dynamics of these structures, especially taking into account the elastic properties of their materials, is much smaller [14, 15]. Usually, dynamic calculations are performed if pulsed, vibrational or moving loads act on the structure [16]. 3 Formulation of the problem When constructing retaining walls in complex engineering and geological conditions, it is necessary to achieve: – increasing the stability and strength of retaining walls; – reducing the cost of used building materials; – decreasing in the volume of earthwork; reduction of strain unevenness; – reduction of construction time; – improving the conditions of filling and compaction of the filling; – increasing operational reliability, quality of work and increase the service life of retaining walls. Thus, to assess the stress-strain state of retaining walls, it is necessary to take into account the joint work of the entire wall with soil and the use of more reasonable soil models in the region of its vertical and horizontal elements. The aim of the research is to study the stress-strain state of the base and retaining wall with a structural surface (PSSP) taking into account their contact interaction to increase the stable operation of the "base – engineering structure" system. 4 Statement of material and results The most common engineering structures in urban design today are retaining walls that are used for fencing: – slopes of embankments and excavations within the area and access railways and roads in case of inability of carrying out slopes with the necessary inclination; – pits during the construction process when it is impossible to perform slopes with the necessary inclination; – special structures – ramps, bulk materials warehouses, bunker overpasses and ore yards of metallurgical plants; – individual overpriced or underpriced sections of technology located within and outside buildings according to technology conditions. Since ancient times, massive retaining walls of stone blocks and slabs have been used to support slopes, excavations, embankments and natural slopes. Technical progress and the laws of economic efficiency draw attention to the design features of the retaining wall and the characteristics of the interaction of the foundation with it. Important issues are optimizing the design of retaining walls, taking into account the following characteristics: – the maximum inclusion in the work of soil filling; – decreasing the values of the active soil pressure; – increasing resistance of the displacement along the sole of the retaining wall; – minimization of material consumption. An important factor in solving the tasks is a high level of knowledge of engineering and geological conditions in large industrial cities and regional centers. Modern research is aimed at clarifying mainly geotechnical nature. The experience of recent years shows that the development of hazardous processes in urban areas continues. First of all, these are the processes of flooding of territories, the development of shear deformations, subsidence of the surface above mine workings, subsidence of loess soils, etc. These processes are associated with a decrease in serviceability or deformation, destruction of buildings and structures [2]. It is not always possible to use well-known technical solutions in the undermined territories and subsiding soils with complex deformations of the base, since they are not suitable for these working conditions. The existing structures of retaining walls are not designed for additional efforts from horizontal displacement or vertical movement of the s

The use of new structural solutions of retaining walls to ensure the stable operation of the “base – engineering structure” system