Vol 12, No 4 (2021)

DETERMINATION OF ADDITIONAL LOAD ON THE BRIDGE FOUNDATION PILE when the karst deformation development
Gotman N.Z., Evdokimov A.G.

Abstract

When karst deformations are formed at the base of bridge supports, additional loads are transferred to the piles, and the bearing capacity of the base decreases. The article proposes methods for determining additional loads on the piles and the bearing capacity of piles, depending on the type of karst deformations. A method for numerical variation calculations based on the analysis of the change of shear stresses on the lateral surface of the piles at different stages of loading with the growth of a cavity in karst soils. The correct design model and criteria for evaluation the stability of the arch over the cavity were selected. A series of numerical calculations were performed. Analytical solutions to determine the additional load on the pile depending on the distance from the bottom of the pile to the roof of karst soils and the predicted diameter of the cavity in karst soils were obtained.
Construction and Geotechnics. 2021;12(4):5-18
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CALCULATION OF THE «BASE - EMBANKMENT» SYSTEM STABILITY
Bogomolova O.A., Zhidelev A.V.

Abstract

The article describes a method of calculating the stability of fill slopes, including the construction of the most probable sliding surface and the determination of plastic deformations areas with elastic and elastoplastic (mixed task) distribution of stresses in the soil massif. The comparative stability calculations results of the "embankment - weak foundation" systems are presented, the data for which were taken from scientific articles published by other authors. According to these calculation results, the stress and displacement fields arising in the "embankment - weak base" system, the position and shape of the areas of plastic deformations constructed both on the basis of the Coulomb - Mohr strength condition and on the basis of solving a mixed problem of the theory of elasticity and the theory of plasticity of soils the article has comparison of numerical values of the stability coefficients and the safety coefficients of a weak. It is established that the replacement of the soil mass of the embankment with an equivalent load, as is often done in engineering calculations, significantly transforms the stress and displacement fields in the soil mass of the base, the position and shape of the areas of plastic deformation and, ultimately, entails obtaining unreliable results. The article shows the results of calculations performed using the FEA computer program developed by one of the authors and the Plaxis software package are in satisfactory agreement: the stress and displacement isofields practically coincide, plastic areas have similar dimensions, shape and position in the soil mass, which allows us to recommend the FEA computer program for practical use in calculating the stability of slopes and slopes, as well as the "embankment - weak foundation" system.
Construction and Geotechnics. 2021;12(4):19-36
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THE LOW TEMPERATURE INFLUENCE ON THE DEEP EXCAVATION SUPPORTING SYSTEM
Boyarintsev A.V., Zavodchikova M.B., Zuev I.N., Zhurko A.V., Kamaev I.S.

Abstract

The practical experience to dig an excavation shows that this process is extended in time and can last for several months engulfing different seasons. An additional accounting of processes occurring in excavation shoring and surrounding soil body during wintertime, when the air temperature drops below zero, is important in such circumstances. This paper describes the results of a field survey of shoring of a deep excavation, soil body and buildings of a surrounding development as the air temperature was changing during the 2020-2021 winter. The survey was performed by monitoring the horizontal and vertical positions of structures using inclinometers and tacheometers. The heaving properties of the clay soil positioned at the excavation digging level were determined in laboratory conditions. The soil frost depth was determined by a numerical simulation of temperature distributions in the "atmosphere-excavation-soil body" system. All this helped understand the nature of the processes observed. The observation results showed that, as the temperature was decreasing, the excavation shoring structures moved into the excavation to a distance of up to 8 mm, and the surrounding development buildings shrank by up to 5 mm. The laboratory study results showed in this context that soils bordering on the shoring structures and foundations of surrounding buildings were not heaving. Thereupon, the strains, which were registered in this actual situation, can not be explained by the frost-heaving phenomenon. The observed strain can be explained by shrinkage of the sprung structure material resulting from a decreasing mean daily air temperature. This effect was confirmed by test results and several surveys presented in the paper. Based on the study conclusions practical guidelines were formulated for excavation digging with consideration to seasonal air temperature fluctuations causing shrinkage and expansion of sprung structures in the shoring structures of excavation of any depth.
Construction and Geotechnics. 2021;12(4):37-53
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THE IMPACT OF THE FOUNDATION PIT WITH ADDITIONAL TRANSVERSE WALLS ON THE SURROUNDING BUILDING AND THE ASSESSMENT OF THE EFFECTIVENESS OF THE MEASURES UNDER CONSIDERATION
Ter-Martirosian A.Z., Cherkesov R.H., Isaev I.O., Grishin V.S.

Abstract

Currently, the implementation of the largest infrastructure projects of the capital continues. The development and modernization of urban transport is accompanied by a large number of deep open workings, often located in established areas of Moscow with developed buildings. Standard design solutions are not always able to provide the necessary safety of nearby buildings, so in some cases additional measures are needed. In this paper, the construction of a pit of an assembly-panel chamber with the use of protective measures in the form of additional transverse walls is considered. To evaluate the effectiveness, compare the results and consider the features of this solution, a series of calculations were carried out in spatial and flat formulation. Within the framework of a two-dimensional task, a methodology for accounting for these measures was proposed, showing close efficiency values in relation to the 3D model. The effects of concrete creep were also considered by using the initial modulus of elasticity Eb and the modulus of deformation Eb,τ. According to the results of calculations of the spatial scheme, the introduction of additional walls reduced the horizontal movements of the fence by 29 %, additional precipitation of foundations by 55 %, creep accounting, in turn, increased the horizontal movements of the SVG by 37 %, but reduced the value of the bending moment by 30 %. However, the actual values of additional deformations of the foundations still turned out to be less than predicted. Thus, it is worth noting that this type of measures is an effective way of passive protection of the surrounding development, implemented at the stage of design decisions, the full effect of which is clearly reflected in the results of the calculation of spatial models and in-situ monitoring data.
Construction and Geotechnics. 2021;12(4):54-67
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DIRECTIONS OF TRANSFORMATION OF ENERGY SUPPLY SYSTEMS TAKING INTO ACCOUNT THE PROSPECTIVE DEVELOPMENT OF TERRITORIES
Beloglazova T.N., Romanova T.N.

Abstract

Modern cities have a multi-level structure of technological systems that functionally and organizationally meet the needs of consumers. The development of urban areas requires an integrated approach. Heat and gas supply systems are the main element of energy systems. In accordance with the economic, social and technological conditions, heat and gas supply systems undergo organizational and structural transformations. The purpose of the study is to develop promising schemes of heat and gas supply systems for territories based on mutual influence. Methods. Based on the analysis of the functional and planning zoning of urban areas, the calculation method provides options for the development of heat and gas supply schemes. The implementation of modern standards of heat supply is possible due to multivariate approaches. The reliability of the research results is ensured by the use of proven calculation methods. Residential neighborhoods with a load on heat supply and household consumption are considered as the main consumers. Small industrial and municipal facilities are taken into account when planning the use of energy resources in the considered territory. Industrial consumption, as a rule, has an independent system of heat and gas supply. The method for determining loads is based on specific normative indicators. When developing the gas distribution scheme for urban areas, the possibility of spreading the load on the heat supply is taken into account. Results. On the one hand, the developed variants of heat and gas supply schemes were considered as alternative ones. Both the scheme of the main heat supply networks and the gas distribution scheme will be able to perform functional tasks to provide subscribers with resources for the considered design area independently. On the other hand, at different stages of system development, alternative options can complement each other, according to the periods of phased development, taking into account the criteria of reliability and cost-effectiveness. Conclusions. The variants of heat and gas supply systems allowed us to identify the main linear parameters for different building densities. The general material criterion for heat and gas supply systems is the material characteristic. The development of heat and gas supply schemes, taking into account the mutual influence, ensures a stable and economical development of the territory.
Construction and Geotechnics. 2021;12(4):68-82
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Research on the use of silica aerogels
Siyanov A.I., Abdulmanov D.I.

Abstract

Silica aerogels are alternative thermal insulation materials for external wall structures. They have a minimum density and water resistance, which in a period of global warming and in a hot climate allows you to get the necessary protective shell of the building. High technologies contribute to a significant improvement in the quality of insulation through the use of aerogel structures. A promising direction in the field of research is to improve the technical characteristics of the insulation used and reduce the costs of its manufacturing process. The aim of the work was to conduct an experiment on a room model and evaluate the possibilities of using silica aerogels as a light thermal insulation material. Within the framework of the study, the tasks were solved using numerical computer modeling. The stages of obtaining aerogels with the specified parameters are reduced into a clear technological sequence, which allows us to justify their physical and thermal properties. Based on the experience of conducting research, the indicators of the use of aerogels in construction are analyzed. An experiment was conducted on a model of a room with aerogel insulation and the radiation from mutually located surfaces was determined. According to the results of the work, a predictable and regular decrease in temperature was obtained over time. Aerogel sheets turned out to be rational materials for walls and other elements of buildings, because along with low density, they have a high thermal insulation ability. The practical benefit of the study lies in the fact that the obtained dependencies allow us to recommend the use of aerogel insulation not only for load-bearing and enclosing structures, but also for individual elements of buildings and can be used to develop methods to increase thermal protection.
Construction and Geotechnics. 2021;12(4):83-93
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THE EFFECT OF SLAG FROM THE PRODUCTION OF METALLIC CHROMIUM ON THE TECHNICAL CHARACTERISTICS OF ACID-RESISTANT TILES
Abdrakhimov V.Z., Abdrakhimova E.S.

Abstract

Object of research: acid-resistant tiles obtained on the basis of unenriched kaolin and waste of non-ferrous metallurgy - slag from the production of metallic chromium, non-ferrous metallurgy wastes occupy the second place after chemical production waste in terms of the amount of especially harmful various pollutants. Various environmental pollutants, such as dust and slag, containing very harmful substances (especially hexavalent chromium, antimony, arsenic, lead and mercury) have a very negative impact on the health of people living within a radius of 50 km from metallurgical plants. The use of large-tonnage waste of non-ferrous metallurgy - aluminum-containing slag from the production of metallic chromium in an amount of 40 % allows to obtain acid-resistant tiles with high physical, mechanical and chemical parameters at a firing temperature of 1300 °C and reduce environmental stress in the area of non-ferrous metallurgy production. Studies have shown that it is impossible to obtain acid-resistant tiles from non-enriched kaolin clay containing less than 18 % A12O3 even at a firing temperature of 1300 °C. The introduction of an optimal amount of chamotte (40 %) into the ceramic mass allows to obtain acid-resistant tiles that meet the requirements of GOST for physical and mechanical parameters at a firing temperature of 1300 °C. The use of aluminum-containing slag from the production of metallic chromium in ceramic compositions in an amount of 40 % (as well as chamotte) allows to obtain products with high physical, mechanical and chemical parameters at a firing temperature of 1250 °C. The introduction of alumina-containing aluminum-containing slag from the production of metallic chromium into the compositions of ceramic masses contributes to the formation of corundum. Corundum is characterized by high chemical resistance to acidic and alkaline reagents. At this temperature, even HF practically does not affect it.
Construction and Geotechnics. 2021;12(4):94-102
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Influence of protective and decorative coatings based on sol-silicate paints on the moisture regime of external walls of buildings
Loganina V.I., Frolov M.V., Mazhitov E.B.

Abstract

The object of research is the humidity regime in external enclosing structures coated with paints with different vapor permeability: ash-silicate, silicate, acrylic and silicone. The purpose of the research is to evaluate the effect of a paint-and-varnish coating based on the developed sol-silicate paint on the change in the moisture regime of the wall, depending on the type of construction. Comparison of the effectiveness of the use of various paints and varnishes is carried out. The properties of the developed sol-silicate paint for finishing the walls of buildings are described. The results of calculating the influence of paints and varnishes on the humidity regime in the walls are carried out. To assess the humidity regime, a technique was used based on the determination of the outside air temperature, with a decrease to which condensation begins to fall out in the walls. This technique makes it possible to compare with high accuracy the humidity conditions in various enclosing structures. Comparison of the humidity regime in the walls of various designs is presented: aerated concrete (from blocks of grades D400, D600), brick, expanded clay concrete. In brick and expanded clay enclosing structures, the influence of the type of insulation (mineral wool mats, expanded polystyrene) on the humidity regime in the walls was also assessed. In the course of research, the thickness of the paint layer varied from 0.2 to 0.6 mm. According to the results of the research carried out in the article, it is shown that when using sol-silicate paint in enclosing structures, the temperature of the onset of condensation and the likelihood of condensation are reduced in comparison with acrylic, silicate and silicone paints. Recommendations are given on the choice of the type of facade paint, taking into account the humidity regime inside the fences of various designs.
Construction and Geotechnics. 2021;12(4):103-114
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