Science and Transport Progress

Selection of Components and Methods of Modification of Soil Cement to Improve the Performance Properties of Subgrade

O. V. Hromova — Thu, 19 Dec 2024 00:00:00 +0200

Purpose. The main objective of the scientific article is a reasonable selection of soil-cement reinforcing structural elements and methods of modifying the soil-cement structure to strengthen the subgrade for railroad tracks. Methodology. For the construction of soil-cement reinforcing elements for a combined railway track using drilling and mixing technology, a number of tasks were solved, including: a reasonable selection of the components and modifiers of the soil-cement element; determination of the properties of the components; establishment of operational requirements for soil-cement and its composition; design of optimal compositions with specified performance characteristics, taking into account the properties of soils and operating modes. Findings. The influence of soil-cement components on the rheological properties of soil-cement mixtures and the physical and mechanical properties of soil-cement was studied. Based on the data processing by statistical analysis, the optimal content of the constituent components of soil-cement mixtures was selected to ensure the technological and operational performance of soil-cement for different types of soils and to strengthen the soil base during track construction. The influence of mineral granular, fibrous and chemical modifiers on the properties of soil cement was investigated. Originality. The possibility of using vertical reinforcing elements made of soil cement with the necessary technological and operational parameters obtained by drilling and mixing technology to strengthen the subgrade, taking into account the stress-strain state and morphology of the soil bases, has been determined. Based on the study, the author made an attempt to select the components and develop optimal soil cement compositions for strengthening the subgrade of a railroad for a combined track. The directions of modification of soil cement with mineral, fiber and chemical additives are also considered. Practical value. The study makes it possible to obtain soil-cement elements of optimal composition and properties for different types of soils and stress-strain states in order to vertically strengthen the soil bases for the railway track. To modify the structure of soil cement and minimize cement consumption, it is proposed to use fiber fibers as modifying reinforcement components. To increase the density, crack resistance, strength, and modulus of deformability and improve the plasticity of the mixture, it is recommended to use chemical modifiers up to 0.3 % and to save cement – particles of fine industrial waste in the form of ground slag or stone grinding screenings in the amount of 20...30 %.

Construction Industry in Ukraine: Transformations and Prospects in the Context of Martial Law and Postwar Reconstruction

H. P. Ivanova, V. Ye. Olishevska, S. M. Hapieiev, S. O. Olishevska — Fri, 20 Dec 2024 00:00:00 +0200

Purpose. Military actions have caused serious changes in the economic sphere in all regions of the country. The construction industry is also experiencing major transformations and challenges. The main purpose of the study is to analyze current trends in the construction market of Ukraine, its features and future in the context of martial law and post-war reconstruction. Methodology. The full-scale invasion led to the near collapse of the construction industry, most Ukrainian enterprises were forced to suspend or limit production, and some reoriented to the needs of the Armed Forces. Many companies in the South and East of the country were in the area of active hostilities or under temporary occupation, as were logistics elements and suppliers of raw materials and components. Damage to the engineering infrastructure also had a negative impact on the production of construction products. Most of the raw materials and construction materials have to be imported, but the volume of imports is also limited, as the port infrastructure is practically non-existent. During the martial law period, the government adopted a number of decrees to facilitate the import of certain goods, but many construction materials are still not on the list. Import substitution and logistics restructuring are also taking place after the abandonment of goods from unfriendly countries that previously dominated such segments as the glass wool, bitumen, and other markets. The experience of other countries in protecting construction facilities from destruction during military operations is considered. Findings. The article analyzes the state of the domestic market and the problems of imports of building materials; staffing of the construction industry; changes in the structure and volume of demand in the construction and real estate sectors; changes in urban planning legislation, as well as the state of transport infrastructure; preparation for post-war reconstruction. Originality. A comprehensive analysis of the state of the construction industry of Ukraine during the armed aggression is carried out. The importance of introducing new safety and civil protection standards in the construction of construction projects, facilitating the issuance of permits, and developing the Unified State Electronic System in the field of construction is considered. Practical value. The article highlights the areas of construction and transport infrastructure that can be developed even during martial law, and considers the main problems of the construction industry in Ukraine.

Quick Computing CFD Model to Predict Chemical Pollution in Room

M. M. Biliaiev, V. V. Biliaieva, O. V. Berlov, V. A. Kozachyna, P. B. Mashykhina — Sun, 22 Dec 2024 00:00:00 +0200

Purpose. The problem of accidental contamination of workspaces attracts special attention, since in the event of such extreme situations, intense chemical contamination of the air in work areas occurs. This poses a threat of toxic exposure to workers. When assessing the consequences of such situations, it is necessary to take into account the time factor, in particular, to quickly determine the creation of concentrations of chemically hazardous substances. In this regard, an urgent task is to develop effective mathematical models for rapid assessment of the consequences of extreme situations in the working areas of chemically hazardous facilities. The paper considers a CFD model for analyzing the process of chemical air pollution in a workspace during an accidental release of a chemically hazardous substance. The solution of the problem is based on the numerical integration of the fundamental equations of continuum mechanics. Methodology. To calculate the air velocity field in the working room during the operation of supply and exhaust ventilation, a mathematical model of the motion of an inviscid fluid was used. The equation of convective diffusion motion was used to calculate the concentration of a chemically hazardous substance in the workspace. The integration of the modeling equations was carried out using finite difference schemes. Findings. A dynamic model has been created to calculate the spread of a chemically hazardous substance in a workspace. On the basis of the built CFD model, a computer program was created to conduct a computational experiment. Originality. A CFD model has been created to predict the level of air pollution in a workspace in the event of toxic gas emissions. The model is based on the fundamental equations of aerodynamic mechanics and mass transfer. The model makes it possible to determine the effect of the ventilation mode, the intensity of emission of a chemically hazardous substance, the location of equipment in the workspace, and the dynamics of the formation of concentration fields. Practical value. The developed CFD model can be used to quickly analyze the consequences of accidental emissions of a chemically hazardous substance in a workplace and assess the risk of toxic exposure of workers.

Mathematical Modeling of Temperature Fields in Cultivation Structures

V. V. Biliaieva, S. A. Shcherbyna — Sun, 15 Dec 2024 00:00:00 +0200

Purpose. The main purpose of the article is to develop a method for calculating thermal fields in greenhouse soil in the case of its artificial heating. Since the temperature regime in greenhouse soil has a significant impact on plant yields, it is very important, on the one hand, to ensure the required temperature in the soil, and on the other hand, to determine the energy-saving heating regime. Methodology. The method is based on the numerical integration of the heat transfer equation. A two-dimensional heat transfer equation was used to analyze and predict the unsteady process of soil heating in a greenhouse under artificial heating, and two finite-difference schemes were used to solve it. On the basis of the constructed numerical models, a computer program was developed to conduct a computational experiment. Findings. Effective computer models have been created to predict the unsteady formation of thermal zones in the greenhouse soil during its artificial heating. The results of numerical modeling are presented. Originality. Prognostic numerical models have been developed to analyze the dynamics of thermal fields formation in greenhouse soil during its artificial heating. On the basis of the developed numerical models, a set of application programs was created to conduct a computational experiment to determine the unsteady temperature field in greenhouse soil. The constructed numerical models belong to the class of «operational models», i.e., they are designed for the operational analysis of thermal fields in the soil. For the practical use of the developed numerical models, standard input information is required. Practical value. The constructed numerical models are a tool for analyzing the dynamics of soil heating and can be used in the development of energy-saving heating technology. These models can be used to determine the time of optimal soil heating in different zones (root system, soil surface) and to determine the rational location of heating elements, the time when the heating elements should be turned off, and the time when they should be turned on again. These models allow us to develop an energy-saving technology for heating the soil in a greenhouse.

On the Issue of the Radon Activity of Tectonic Faults on the Qatar Peninsula

V. Y. Ulyanov, V. V. Bilyk — Thu, 19 Dec 2024 00:00:00 +0200

Purpose. The paper aims at providing the modern evaluation of radon activity in identified tectonic faults of the earth's crust based on archival data of radon measurements in groundwater which previously have been performed in the northern and eastern parts of the Qatar Peninsula. Methodology. The paper presents an additional extended justification for the application of an innovative technique for these conditions to identify the activity rate of tectonic faults in the rock foundation under the geological conditions of the Qatar Peninsula based on third-party measurements of radon in groundwater and using own universal Evaluation scale. Findings. A modern analysis of previously obtained results of radon measurements in groundwater of the Qatar Peninsula allowed us to suggest the orientation of tectonic fault directions in its northern and eastern parts and to additionally reveal the rate of their radon activity within the peninsula with a preliminary magnitude evaluation of displacement along the faults. A similar assumption was also proposed in the western part of the UAE adjacent to the peninsula, where the Barakah Nuclear Power Plant (BNPP) is located. This assumption is based on a certain similarity in the geological and tectonic conditions of the region. Originality. For the first time, the authors proposed the location of tectonic faults within the northern and eastern parts of the Qatar Peninsula according to radonometry performed for other purposes. We estimated their radon activity and the magnitude of movement along the faults. This implies increased safety during the construction and operation of various facilities, including a high degree of responsibility, particularly pipeline systems and transport communications that are important for the country's economy. Practical value. This technique can also be used in seismic monitoring for construction sites and in adjacent territories of other countries where similar explorations have not been conducted before.

Modernization of Existing Level Crossings in the Areas of Construction of the European Standard Railway Track in Ukraine

M. B. Kurhan, A. M. Kurhan, O. F. Luzhytskyi, R. V. Ivanov, N. P. Khmelevska — Fri, 20 Dec 2024 00:00:00 +0200

Purpose. The article aims to analyze modern technological solutions to improve the level of safety at railway crossings, prevent emergencies and ensure uninterrupted traffic. Methodology. The study is based on the use of mathematical modeling and numerical methods to analyze the impact of modernization and new projects on the level of safety at railway crossings. Using computer modeling, mathematical models were built that reflect different scenarios of crossings. Based on the data obtained, the effectiveness of the proposed measures was assessed and recommendations for further optimization of the security system were developed. To evaluate the effectiveness of the proposed measures, a system of indicators has been developed to quantify the level of safety of railway crossings before and after modernization. These indicators take into account the daily intensity of train traffic through the crossing, the daily intensity of traffic on the road, the equipment of the crossing, the radius of the curve in the plan and the longitudinal slope of the road on the approaches to the crossing. Findings. An improvement of the method of the final accident rate, which is one of the most common tools for assessing traffic safety at railroad crossings, is proposed. The application of this method made it possible to quantify the level of risk of accidents and analyze the effectiveness of measures aimed at improving safety. The method is relatively easy to use and does not require complex mathematical calculations, and allows taking into account a wide range of factors affecting traffic safety at a level crossing, such as traffic volume, design features of the level crossing, availability of signaling, etc. The final coefficient was used to compare the safety level of different crossings and track the dynamics of changes in their equipment over time. This made it possible to identify crossings that require priority modernization, as well as to predict changes in the initial and calculated data and plan measures to introduce innovative technologies that improve traffic safety at crossings. Originality. An integrated model for assessing the safety of railroad crossings has been developed that takes into account not only traditional indicators (frequency of accidents, traffic intensity) but also new factors such as equipment reliability, human factor, and the impact of external conditions. The proposed model makes it possible to determine a more accurate risk forecast and choose optimal solutions for the modernization of level crossings, taking into account specific operating conditions. Practical value. The formulated recommendations can be used to develop effective programs for the modernization of railway crossings in Ukraine. The implementation of the proposed technologies will increase the level of traffic safety by 20% and reduce the average waiting time at a crossing by 15%. In addition, it will help to increase railroad capacity and reduce infrastructure maintenance costs.

Optimization of Curve Correction in the Plan Using Computer Modeling to Improve Train Safety

N. P. Khmelevska, M. B. Kurhan, D. M. Kurhan — Tue, 17 Dec 2024 00:00:00 +0200

Purpose. The authors intend to develop and implement innovative approaches to optimizing curve correction in the plan of railway tracks using computer modeling. This process aims to: improve traffic safety; improve the smoothness of the ride, which increases passenger comfort; eliminate speed limits on curved sections, which reduces travel time and increases railroad capacity; reduce track maintenance and rolling stock repair costs. The use of special software to simulate various scenarios of train traffic along the adjusted curves will allow us to assess the impact of the train flow structure on the speed, rolling stock dynamics, and track condition. Methodology. The study is based on the theory of mathematical modeling and numerical calculation methods. To find the best option for the reconstruction of railway sections, the line is considered as a complex system consisting of various infrastructure facilities. Due to their unsatisfactory technical condition, these facilities may limit the speed of traffic on certain sections. The solution to this problem is complicated due to the interdependence of such objects: the reduction of travel time on a particular section is not linear, and obtaining accurate results requires traction calculations taking into account various options for eliminating speed limits. Findings. A calculation algorithm for optimizing long sections of the railway plan is proposed. The algorithm allows to take into account the desired direction of shifts in the curves, which greatly facilitates the optimization process. An example of calculations based on the proposed algorithm is given, which demonstrates the effectiveness of the approach. Originality. The scientific and applied problem of optimizing the process of adjusting railway curves in the plan has been solved. This helps to improve the safety and speed of trains through the introduction of the latest computer modeling methods. Practical value. The implementation of the proposed technology for optimizing the railway plan will significantly increase the speed and safety of train traffic, as well as increase the throughput capacity of railway lines. This will be an important step for the integration of Ukrainian railways into the European transportation system.

A Spatial Mathematical Model of the Dynamic Behavior of Modern Rolling Stock in High-Speed Traffic

A. Ya. Kuzyshyn, V. V. Kovalchuk, Yu. H. Sobolevska — Tue, 17 Dec 2024 00:00:00 +0200

Purpose. The paper aims to develop a spatial mathematical model of the high-speed electric train EKr-1 “Tarpan” taking into account the design features of its first and second stages of spring suspension. Methodology. The design scheme of the electric train is taken as a set of 7 solids connected by ligaments of different rheology. Each of the bodies performs spatial oscillations. In this case, the wheel set is considered as a system with two degrees of freedom (lateral displacement and wagging). The angular and linear displacements of the bodies are considered as generalized coordinates. The resulting mechanical system has 26 degrees of freedom. The differential equations of motion are written using the d'Alembert principle. The kinematic perturbation of oscillations due to movement along unevennesses of the track in both vertical and horizontal directions is considered. The presence of elastic and dissipative viscosities is taken into account in the first and second stages of the spring suspension. The hypothesis of geometric linearity of deformations is accepted. The reactions acting in the longitudinal (in the wheel plane) and transverse directions are taken into account at the point of contact between the wheel and the rail. The longitudinal and transverse reactions are quantitatively described by the nonlinear creep hypothesis. The modeling of hydraulic vibration dampers takes into account their inclined location, which makes it possible to dampen vibrations in the vertical and horizontal directions. Findings. The spatial design scheme of the studied object was chosen. The geometric dependences between the deformations of the ligaments and the generalized coordinates of the design scheme are obtained. The physical dependencies between the reactions of the ties and their deformations are described, taking into account the pneumatic spring suspension system. The differential equations of oscillations for each element of the design scheme are derived. Originality. For the first time, a spatial mathematical model of the dynamic behavior of high-speed railroad rolling stock was constructed, taking into account the peculiarities of the pneumatic spring suspension system, the location of the bindings, and the interaction of the wheelset with the rail track in the vertical and horizontal directions, both in straight and curved sections of the railroad track. Practical value. The development of such a model will make it possible to numerically study its dynamic and safety performance in high-speed traffic conditions at the design stage of high-speed railroad rolling stock and to establish the optimal parameters of the first and second stages of spring suspension, while setting various kinds of kinematic disturbances from the rail track.