Vol 14, No 4 (2023)

Calculation of the temperature condition of a thermostabilizable base with a single pile
Zhaysambaev E.A., Maltseva T.V., Kraev A.N.

Abstract

The article deals with one of the main problems of construction in the area of permafrost soils - the presence of sites represented by thawed permafrost soils [1-3], formed due to natural conditions (waterlogged site, site relief features, swamping, etc.) and man-made impacts (warming effect of buildings and structures, systematic discharges and leaks from engineering networks, runoff and stagnation of surface rainwater, etc.). To ensure the bearing capacity of a single pile and the specified temperature regime of the foundation soils in the given engineering-geocryological conditions, it is possible to use the cooling devices of seasonal action. The main issue when using the cooling devices of seasonal action is to determine the main parameters affecting the bearing capacity of a single pile and the deformability of the foundation. To determine the parameters affecting the bearing capacity of a single pile and the deformability of the foundation, a set of numerical temperature calculations of thermostabilized soil mass represented by thawed permafrost soils with a single pile under different initial boundary conditions was performed in the certified Frost 3D software package. Temperature calculations were performed for the thawed soil mass, in which a single reinforced concrete pile with a single vertical vapor-liquid thermal stabilizer structure is submerged. The geometrical dimensions of the calculated area are 30 × 30 × 30 m. Based on the results of numerical experiments, the main physical, thermal and geometric parameters of the formed frozen core have been determined, which will be incorporated into the methodology for predicting the bearing capacity of a single pile in a thermally stabilized viscoelastic foundation represented by thawed permafrost soils. On the basis of the calculations performed, a design diagram of a single pile in a thermostabilized foundation was built and graphical dependences of changes in the diameter, height and geometric position of the frozen core depending on the initial boundary conditions were plotted.
Construction and Geotechnics. 2023;14(4):5-18
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Modeling of physical and chemical processes in the synthesis of foam glass of various modifications: phase analysis and prediction of properties
Fedosov S.V., Bakanov M.O., Grushko I.S., Bychinskii V.A.

Abstract

To achieve effective thermal insulation of enclosing structures, it is necessary to increase the resistance to heat transfer through the use of advanced thermal insulation materials. A promising heat-insulating material is foam glass, which has a low thermal conductivity, high mechanical strength, frost resistance and low density. The physical properties of foam glass are determined by the structure of its macro- and microstructure, which depend on the temperature regime of synthesis and composition components. In the work, the choice of the optimal compositions of foam glass for correct comparison was carried out, a physicochemical model was developed, the qualitative and quantitative phase composition of foam glass samples was determined using the method of X-ray phase analysis to verify the results obtained. Based on the performed calculations of the composition of phases and components that are formed during the synthesis of various modifications of foam glass, the possible phases were determined using physicochemical models and methods for minimizing thermodynamic potentials. These methods make it possible to determine the equilibrium composition of a heterogeneous system and the thermodynamic parameters of processes. The reliability of the model is confirmed by the results of X-ray phase analysis, which showed the presence of phases obtained by calculation. The scientific novelty of the study lies in determining the features of the formation of crystalline phases during the synthesis of foam glass, taking into account the temperature-time conditions and composition. The study showed that the formation of the mineral composition of foam glass in the considered modifications is significantly affected by Na2B4O7∙10H2O and natural chalk. Additionally, microimpurities affect the formation of new aluminosilicate phases and the redistribution of the main chemical elements between the mineral components of foam glass. This also leads to changes in the density and composition of amorphous phases. An efficient model has been developed using the Gibbs isobaric-isothermal potential minimization method, numerical values of the number of probable phases and components formed during the synthesis of foam glass material have been obtained.
Construction and Geotechnics. 2023;14(4):19-33
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Adequacy of a road design model to a real object in the context of digital transformation
Bobrova T.V.

Abstract

The relevance of combining BIM information modeling technology and digital twin technology into the SIM-AD information modeling system for managing the construction and operation of roads throughout the life cycle is substantiated. The key provision of this new digital technology is to provide bidirectional communication between a real physical object and a virtual object - its digital model. Throughout the life cycle of a highway, a large amount of information is developed and stored, however, due to its disunity and insufficient level of intellectual support, asset management decisions are not always adequate and timely. One of the hard-to-solve problems of automating the design of transport facilities is the complexity of a formalized description of the processes of interaction between elements of a road structure and changing natural and climatic factors at a linear facility. The developed scheme for including the method of spatial zoning of the road route based on complex engineering surveys in SIM-AD allows you to create a digital twin model with the decomposition of the object into design and technological modules, which more reliably take into account the influence of natural polystructures on the elements of the road structure. Digital twin instance models are designed to record the current state of the operated object and environmental parameters based on sensors installed in the same type of linear and lumped design and technological modules. Systematic diagnostics and accumulation of statistical information on the mutual influence of building elements and environmental factors will serve as the basis for planning effective measures at the stages of maintenance, repair and reconstruction of roads.
Construction and Geotechnics. 2023;14(4):34-45
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Heat treatment of ground surface using an electric arc plasma generator
Sirotyuk V.V.

Abstract

The article presents a generalization of the results of experimental and theoretical studies on the intensive thermal effect on the surface of foundations from cohesive soils (as opposed to deep heat treatment) using an electric arc generator of low-temperature plasma (plasmatron). A plasmatron with massive consumable electrodes made of borosilicated graphite and a wide "blurred" plasma torch was used for heat treatment. Physical and mathematical modeling of the thermal effect on the surface of clay soil by a moving high-temperature source has been performed. For the first time, a special installation was manufactured and experimental studies were carried out on the heat treatment of ground surfaces on the site with an electric arc plasma torch. It is established that the effective heat flux density reaches 2.5-.3.5 kW/cm2. The main part of the thermal energy for the used plasmatron enters the material due to radiant heat transfer. An analytical mathematical model of the temperature field of a three-dimensional semi-bounded body in the technological process under consideration is given by an essentially nonlinear boundary value problem for a nonlinear heat equation with nonlinear boundary conditions of the second kind. When solving thermophysical problems, the ground semi-bounded space was considered as a quasi-homogeneous medium having a constant initial temperature and initial thermophysical parameters that change in the process of temperature increase. The effective values of the thermophysical characteristics were determined on the basis of experimental data. Calculations and experiments have shown that the temperature boundary leading to significant changes in the structural properties of soils drops to a depth of 4-6 cm from the surface, despite the boiling of the ground melt with a temperature of 2500 ...2800 K on the ground surface. Therefore, a new technological principle of heat treatment is proposed, which consists in building up the ground melt in layers of 4-5 cm up from the initial surface. The impossibility of obtaining a positive effect even with the use of a powerful high-temperature source of exposure in the case of traditional surface heat treatment technology has been confirmed. The new plasma technology of surface heat treatment of ground surfaces to the stage of silicate melt allows to obtain a common layer of the required thickness. At the same time, the efficiency of surface heat treatment is significantly increased. The new technology of layer-by-layer surface deposition reduces cracking in the layer when the melt cools, but does not eliminate this negative process.
Construction and Geotechnics. 2023;14(4):46-61
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Analysis of the stability of the Kuban river landslide slope involving the materials of landslide hazard monitoring
Bandurin М.А., Volosukhin V.A., Prikhodko I.A., Rudenko А.А.

Abstract

The article discusses the improvement of methods for calculating the landslide threat in the monitoring of landslide hazard areas on the Kuban River and the study of the possibility of their negative impact on the operated hydraulic structures. The growth of economic activity, intensive use of water resources in the Kuban River basin leads to a decrease in the bearing capacity of slopes and an increase in landslide phenomena. These processes are also observed in the basins of other anthropogenically developed rivers of the Russian Federation. Shore protection structures and their construction are justified on the basis of the limit state method in accordance with the requirements of SR 58.13330.2011. The stability of such structures should be determined by reference to the stability conditions of the entire slope taking into account all acting loads and impacts. To solve this problem it is very effective to use a complex of structures regulating the flow of the river, flow guides (dams made of selected rockfill), slope-strengthening ones, etc. Measures justifying economic activity on a landslide slope are very effective. The right slope of the Kuban River in the suburbs of Armavir, Krasnodar Krai is characterized by the fact that significant (more than 3 m) fluctuations in inter-level and flood flow of rare frequency are observed on this section of the river. Realizing anti-landslide and bank strengthening measures it is necessary to provide for both a reduction in general and local erosion of the left bank and the drainage of groundwater and surface from the anthropogenically developed area adjacent to the right slope of the river Kuban. The purpose of this research is to substantiate the stability of the right slope of the Kuban River in the vicinity of the city of Armavir, Krasnodar Krai, where initial collapses are already taking place in connection with the construction of residential buildings in the immediate vicinity of the bank and the development of general and local erosion of the right bank of the river. The calculation is carried out according to several methods for the basic and special load combinations. These calculations are necessary to substantiate landslide and bank protection measures on the right bank of the Kuban River.
Construction and Geotechnics. 2023;14(4):62-74
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Change in strength parameters of dusty-clayey soils depending on the time of dynamic load impact and soil type
Zavodchikova M.B., Cheremkhina A.D.

Abstract

The method of high frequency vibratory driving and extraction of sheet piles is frequently utilized in the conditions of structurally unstable soils in St. Petersburg. However, with this method of installation (extraction) of sheet piles in the surrounding soil mass it arises oscillations that are transmitted to nearby buildings and housing, capable of causing dangerous phenomena in their undergroud and aboveground structures, mainly related to differential settlement of foundations. The prediction of additional settlement of buidings in the surrounding area from vibro-driving/extraction of sheet piles is a complex, multi-factor task, and the level of the structural displacement of building, which is the main controlled parameter for the influence of dynamic loading on the foundation soil, according to the current regulatory documents Territorial Building Codes50-302-2004, Departmental Building Codes490-87, Russian State Standard 52892-2007 is merely an indirect criterion for assessment. To obtain a more accurate assessment of the development of additional settlements in buildings during high-frequency vibratory pile driving and sheet pile extraction, it is necessary to take into account not only the duration and frequency of the impact, but also the properties and type of soil itself. The purpose of this reseach was to study changes in the strength parameters of silty-clay soils depending on the time of dynamic loads impact, the type and consistency of the soil itself, as well as changes in parameters depending on the “rest” time of the soil base after exposure to vibration. The article presents the results and shows the tendency to reduce the parameters of soil strength after the application of dynamic load and the dependence of their change on the time of impact, on the type and consistency of the soil. It has been determined the dependence of changes in the strength parameters of the soil conditionally upon the "rest" time of the soil mass as a result of thixotropic re-storation, which will determine the economic attractiveness for the accident-free technology of this method.
Construction and Geotechnics. 2023;14(4):75-85
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