The article discusses the method of constructing a horizontal protective screen made of large-diameter steel pipes used for the construction of tunnel-type structures using a closed method. The factors influencing the choice of this method are analyzed - features of the construction site, economic and time indicators. As an example, a project for constructing a protective screen made of large-diameter pipes for the construction of a two-section transport tunnel under railway tracks is considered. Diagrams are provided that provide basic information about the construction project, its main parameters are considered: geometric shape and dimensions, location of structural elements with an indication of their sizes. The sequence of construction work is presented, consisting of six main stages, starting with the construction of auxiliary working pits and ending with the construction of the internal structures of the tunnel. Such construction of tunnels in dense urban areas requires taking into account and minimizing their impact on existing structures and transport routes in the construction area. The article presents the results of numerical calculations of stabilized movements of the soil mass, confirming the effectiveness of this method.

Keywords: horizontal protective screens, tunnel-type structures, large-diameter pipes, soil deformations

The article presents the results of a comparative analysis of practical calculations of driven and bored piles, which have similar geometric parameters and common geological conditions of construction sites. Taking into account the peculiarities of the use of these piles and the available experimental data, the paper analyzes the calculated values of their bearing capacity and gives an engineering assessment of the results of the calculation. The quantitative difference between the determined parameters of the bearing capacity of piles - friction along the lateral surface and frontal resistance, is clearly shown in the constructed diagrams. So, when using the standard values of the coefficients to determine the bearing capacity of piles, we have a significant excess of this parameter for driven piles. The need to use more gentle methods of driving piles to the design depth leads to the possibility of using the technology of arranging bored piles, which have a lower bearing capacity with the same parameters as driven piles. This feature should be taken into account in engineering calculations when selecting the optimal dimensions of bored piles.

Keywords: driven piles, bored piles, geological conditions, engineering calculations, bearing capacity

he article provides a comparative analysis of the experimental data obtained as a result of field tests (excavation), with the data of numerical calculations. Mathematical modeling of the experiment was carried out using the Plaxis software package, according to the model of plastically hardening soil. The main task was to compare the obtained data on the decompaction of the soils of the foundation pit with the calculated deformations and analyze the results. The problem was solved in accordance with the experimental data in two settings: in the first case, the variant with inclined slopes of the pit sides was considered; in the second, the problem with vertical slopes was solved. As a result of the calculation, data on the deformations of the soil massif were obtained and analyzed according to the two selected schemes. The best possible convergence of the calculation results with the experimental data was obtained for a pit with inclined slopes, which corresponded to the experimental formulation of the problem. For the case with vertical slopes, the results of deformations of the decompaction of the bottom of the pit turned out to be two times less, which corresponds to the conclusion that the quantitative results of deformation of both the foundation of the pit and its upper side part directly depend on the angle of the slope.

Keywords: experimental pit, experimental data, numerical calculation, deformations of decompression, pit slopes, calculation results

The article presents experimental data on changes in the stress-strain state of the soil of the base of the experimental pit. The research was carried out in the Moscow region, an extended pit had a depth of 4 meters. The excavation of pit was carried out mainly in clay loams which had various consistencies. During the experiment, the required number of benchmarks, surface grades and pressure sensors was established. The main issues of the in-situ research were to obtain data on the change in the natural stress state as a result of excavation of the foundation pit over time, on the patterns of soil deformation along the depth of the foundation pit and of the sides and, accordingly, on the development of an active zone of redistribution of initial stresses. The results of deformations of the day surface of the foundation pit were obtained and analyzed, the character of the change in deformations along the depth of the foundation pit was studied. As the research had been continued for 2.5 months, the necessary conclusions about the features of the development of the deformation of the foundation pit over time were made.

Keywords: foundation pit, experimental research, patterns of deformation, stress state, active zone

The article provides a solution to the problem of the stress-strain state of the base in the field of karst dip. The problem is considered in the linear formulation for a layer of bounded thickness weakened by a cylindrical notch. The solution is obtained in polynomials based on the use of the Solyanik – Crass stress functions satisfying a quasi-harmonic type differential equation. The main task was solved on the basis of using the principle of superposition. The verification of the obtained solution was carried out on the basis of a comparison of the components of the stress and displacement tensor with the results of numerical solutions. Graphs constructed using the Mathcad mathematical complex and the Plaxis software complex were considered. Their analysis showed good convergence of the results.

Keywords: Karst, cylindrical cavity, stresses, displacements, isopolis, linear formulation, mixed problem