The article presents the research of ecological safety of autoclaved ash-foam concrete using ash from sewage sludge incineration in the constructed and operated production building. It is shown that after more than eighteen years of operation, the building made of autoclaved ash-foam concrete obtained using ash from sewage sludge incineration plant turned out to be environmentally safe for humans. Purpose: ash from sewage sludge incineration has high average specific radioactivity (radium and thorium), which strongly limits its further use. Earlier it was found that the use of ash from sewage sludge incineration as a raw material in autoclaved ash-foam concrete in different proportions affects the content of natural radionuclides in the finished product. The paper considers the environmental safety of autoclaved ash-foam concrete after prolonged operation. Methods: the research was carried out at the operating facility using a verified dosimeter-radiometer ATOMEX MKC-AT6130. Results: it was found that in all samples of autoclaved ash-foam concrete produced with ash from sewage sludge incineration the generated radiation background was below the norm, on the border of threshold values. Practical significance: the results of the work are important for construction, as they expand the ideas about the peculiarities of autoclaved ash-foam concrete and the possibility of safe use of ash from sewage sludge incineration in construction.

Purpose: to consider the problem of the key-segment extrusion that occurs during the construction of subway tunnels in St. Petersburg using prefabricated high-precision reinforced concrete linings with increased water resistance with a diameter of 10.3 m. To analyze the possible processes leading to this phenomenon and methods of solving the problem in construction conditions. To determine the consequences of the currently used solutions to the problem. To develop an analytical methodology for determining the magnitude of the friction force acting on the radial joints planes of contacting segments based on classical structural mechanics methods (displacement method). To carry out mathematical modeling of the extrusion process by the finite element method and compare its results with those obtained analytically. To develop recommendations for the elimination of block extrusion, which can be both applied in construction conditions and taken into account when designing lining structures. To analyze the effectiveness of the proposed recommendations. Methods: full-scale data from constructed objects, analytical calculations and mathematical modeling by the finite element method were used. Results: an analytical method is proposed for determining the magnitude of the pushing force of the key-segment and the friction force in the radial segment joints. The results of mathematical modeling showed high convergence of the results obtained by the two methods. Recommendations have been developed to eliminate the phenomenon of extrusion, and their effectiveness has been evaluated. Practical importance: the results of the study can be used at the design stage of prefabricated reinforced concrete linings with increased water resistance for large-diameter tunnels, as well as in construction conditions at the time of installation of the key segment.

Purpose: to consider issues related to the standard definition of the strength characteristics of an air binder and a cement binder. To show a technological solution to the problem of regulating the strength of an air binder stone by stabilizing care during setting and hardening. Methods: during the research, GOST 23789- 2018 “Gypsum binders. Test methods”. Results: a distinctive feature of restoration plaster solutions is that structure formation and strength gain occur only in an air-dry environment. As a result, the availability of approved and applied standards for the manufacture and use of restoration plaster solutions does not fully guarantee the creation of a reliable and safe environment for the life of an architectural heritage monument. It has been established that the mechanical characteristics (compressive and bending strength limits), as well as elastic parameters should be the same or lower in historical and restoration solutions in order to avoid changes in stress distribution. Practical significance: developed taking into account the comprehensive care of hardening stone, gypsum-lime binders can have a wide range of applications. They can be used as mortars for the preservation of architectural heritage and in the reconstruction of modern buildings, self-supporting partitions, fire protection elements or drywall (in places where a higher mechanical load is expected).

Objective: perform a comparative analysis of the features of existing theories for calculating cold-formed steel thin-walled profiles, consider the need to develop a calculation methodology and justify the criteria for the applicability of cold-formed steel thin-walled profiles in the main structures of bridge structures, justify the feasibility of using structures from thin-walled cold-formed profiles in relation to bridge construction in order to reduce metal consumption and increase economic efficiency. Methods: a comparison of existing theories for calculating cold-formed steel thin-walled profiles at the moment, a review of the existing practice of application and technical and economic indicators of thin-walled profiles in the field of industria and civil construction. Results: a comparative analysis of the features, advantages and disadvantages of individual theories for calculating cold-formed steel thin-walled profiles has been carried out, criteria for choosing a calculation theory depending on the nature of their work have been established. Some technical and economic indicators of similar structures made of cold-formed steel thin-walled profiles in the structures of buildings for industrial, civil, agricultural and other purposes are presented. The analysis showed that these structures have lower metal consumption compared to conventional steel structures. Practical importance: the need to develop a methodology for calculating structures made of cold-formed steel thin-walled profiles in relation to bridge construction is identified. This technique has practical significance for the implementation of thin-walled profiles in the main structures of bridges. A number of factors are given that may be decisive in favor of choosing cold-formed steel thin-walled profiles as part of the load-bearing structures of the main beams of bridges with an appropriate feasibility study in certain conditions, taking into account their features, advantages and disadvantages.

Purpose: increasing the efficiency of the transport network based on the developed balanced system of indicators for the interaction of railway lines of various categories. Methods: methods of control theory, system analysis, synthesis and mathematical modeling, theory of transport processes and systems, and transport planning methods are used. Results: a set of indicators that influence the interaction of railway lines of various categories is substantiated, based on a balanced system of indicators, which makes it possible to develop corrective measures to optimize the transportation process. Practical significance the implementation of the proposed solutions allows us to develop and specify a program to increase the efficiency of operation of low-intensity public railway lines and adjust scheduled transportation on these lines.

Purpose: to assess the impact of noise levels in St. Petersburg metro cars. Identify what types of cars used on various metro lines. Determine what types of rolling stock cars used in the metro. Determine how much the service life of the cars affects the noise level in the car. Conduct measurements of noise levels inside the carriages of rolling stock of various types on various metro lines. Correlate the obtained values with the established requirements of SP 2.5.3650–20 “Sanitary rules for the operation of subways” with the values of maximum permissible noise levels in cars. Conduct an analysis of the level of noise impact on humans in the metro and identify possible measures to reduce the noise level in the metro. Methods: measurements of noise levels at various stations and trains were carried out by a special instrumental method, using a digital integrating meter and an Octave 110A sound spectrum analyzer of 1st accuracy class according to GOST R 53188.1. Results: measurements of noise levels carried out in various types of cars on various branches of the St. Petersburg metro. An analysis of the results of field measurements of noise levels for equivalent and maximum levels in the metro shows that permissible noise levels are exceeded in the “Baltiets” car on the red metro line, in car 81-717/714 on the blue metro line; in car 81-717/714 on the purple metro line; in car 81-556.2/557.2/558.2 “Neva” on the green metro line. Practical significance: identification of the obtained data show necessary measures to reduce noise in the metro. Installation of sound-absorbing materials at stations and on trains. Replacing old trains with newer ones.

Purpose: assessing the effectiveness of peat groundwater purification using a combination of two methods of ultrafiltration and membrane purification. Identify specific characteristics of the composition of peat or groundwater, determine possible possible methods of treating these waters to ensure compliance with the requirements of SanPiN 2.1.3684–21 “Sanitary and epidemiological requirements for the maintenance of territories of urban and rural settlements, for water bodies, drinking water and drinking water supply to the population, atmospheric air, soil, residential premises, operation of industrial and public premises, organization and implementation of sanitary and anti-epidemic (preventive) measures” to the quality of drinking water. Determine the list of composition indicators that require cleaning. Conduct an assessment of wastewater treatment methods used to treat peat groundwater. Togo, Conduct research on the composition of purified groundwater before and after treatment, determine the effectiveness of the treatment methods used according to various indicators. Determination of the concentrations of groundwater composition components was carried out using approved methods in accordance with GOST R 57164-2010 clause 5; GOST R 57164-2010 clause 6; PND F 14.1:2:4.207-04; PND F 14.1.2:3:4.121-97; PND F 14.1:2:4.114-97; GOST 31594-2012 Method A; PND F 14.1:2:4.50-96; PND F 14.1.2:3:4.111-97; PND F 14.1.2:3:4.111- 97; PND F 14.1.2:3.154-99; PND F 14.1.2:3:4.123-97; GOST 31859-2012; PND F 14.1.2:3:4.4-95; GOST 31940-2012 clause 6; PND F 14.1.2:4.178-02; PND F 14.1.2:4.214-06. An analysis of the results of laboratory studies of the composition of peat groundwater before and after treatment was carried out, and the effectiveness of ultrafiltration and membrane water purification methods was determined. The results of studies of the effectiveness of purification of peat groundwater using ultrafiltration and membrane purification methods show that purified groundwater meets the sanitary and epidemiological requirements for the quality of drinking and domestic water supply established by SanPiN 2.1.3684-21. Practical significance: the results obtained from studies of the effectiveness of peat groundwater treatment using ultrafiltration and membrane treatment methods indicate the possibility of using these methods, because they ensure that water quality meets the requirements of SanPiN 2.1.3684-21.

The analysis of the closeness of interdisciplinary connections, built with the help of exam grades received by students in previous and subsequent disciplines, according to the sequence of their study according to the curriculum. The influence of the knowledge of mathematical disciplines on the knowledge of general engineering disciplines and the dependence of knowledge between the disciplines of a special block, achieved both in full-time and distance learning, is considered. The closeness of interdisciplinary ties was established on the basis of the results of the bachelor’s examinations in the field of Computer Science and Computer Engineering, conducted both before the outbreak and during the development of the pandemic.

Purpose: the fight for ecology in the transport sector is ensured by improving the design of vehicles and engines, the working processes of internal combustion engines, as well as the use of alternative fuels. To determine the rational use of biofuels in vehicles, it is necessary to assess the environmental effect that will be achieved when using them. Methods: the existing methods of estimating exhaust gas emissions from motor vehicles are considered. Based on them, improvements have been made, which include the introduction of additional coefficients that take into account changes in the environmental load depending on the percentage of biofuels mixed with traditional hydrocarbon fuels. Results: the calculation of the environmental effect from the use of biofuels was carried out using the example of adding biodiesel to petroleum diesel fuel, for which, based on statistical data from the US Environmental Protection Agency and data, WE established dependences of changes in annual emissions of harmful substances and carbon dioxide for a heavy-duty cargo vehicle. In addition to the calculation, the article presents graphs of emissions of harmful substances, taking into account their relative aggressiveness and the amount of carbon dioxide released during the combustion of biodiesel mixtures. Practical significance: The proposed method for calculating the environmental effect makes it possible to estimate the volume of emissions of harmful substances and carbon dioxide depending on the concentration of biofuels mixed with traditional fuels. Such an approach can provide an overall picture of the effect of using biodiesel, and at the same time, the coefficients used need to be clarified.

Purpose: consideration of the issue of the use of hydraulic vibration dampers in spring suspension of various types of railway rolling stock. The article provides an overview of the layout of hydraulic vibration dampers in the spring suspension of rolling stock, their advantages and disadvantages are given Methods: review and analysis of spring suspension designs of various types of traction and non-traction rolling stock in operation, as well as patented designs. Analysis of the arrangement schemes of hydraulic vibration dampers in the spring suspension of rolling stock. Results: the main reason for the use of hydraulic dampers in spring suspension is the inability of cylindrical springs to minimize the influence of oscillatory movements of rolling stock that occur during its movement. The necessity of using hydraulic vibration dampers in structures of various types of rolling stock is substantiated. The arrangement schemes of hydraulic vibration dampers are considered. Examples of the use of hydraulic dampers in spring suspension of various types of rolling stock are given. Practical significance: the necessity of using hydraulic vibration dampers is shown not only in the structures of the undercarriage of passenger cars and locomotives, but also in the spring suspension of freight cars. The use of hydraulic vibration dampers makes it possible to minimize the negative impact of oscillatory movements on both the structure of the rolling stock and the health of passengers and locomotive crews, as well as to increase the comfort of their stay. The use of hydraulic dampers in the spring suspension of freight rolling stock can increase the speed of its movement by improving the running qualities of freight cars and the degree of safety of transported goods.