Навчально-науковий центр "Мости та тунелі" (раніше Факультет "Мости і тунелі") ДІІТ
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Browsing Навчально-науковий центр "Мости та тунелі" (раніше Факультет "Мости і тунелі") ДІІТ by Author "Alkhdour, Ahmad M."
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Item Application of Centrifugal Modeling for the Study of Landscape Structure Stability(Tamilnadu, India, 2019) Ignatenko, D. Yu.; Tiutkin, Oleksii L.; Petrenko, Volodymyr D.; Alkhdour, Ahmad M.ENG: The calculation of stability by mathematical methods of complex shapes of slopes with a diverse geological structure is reduced to simple formulations and assumptions for finding curves of sliding surfaces and for forecasting possible forms of stability loss. The method of centrifugal modeling allows us to conduct in-depth studies of the experimental, reproduced, reduced scale of the slope and to reliably identify the nature of the existing deformations after rotation on a centrifuge, analyze them and draw conclusions about the stability of the studied slope. The centrifugal simulation can be divided into four stages, each of which is described in detail in this article with reference to photo materials and descriptions. The obtained results of the centrifugal modeling of the shifting slope of the Krasnopovstanska ravine and the analysis of the deformed state of the model before and after placement of soil cement piles in the body of the slope. Centrifugal modeling is not a new method for studying the stability of slopes. This method requires special complex hardware and hardware, therefore, it is used rather infrequently. Conducting this type of research is accompanied by a small amount of informative literature on the methodology of the simulation itself. This article is devoted to the question of conducting and successfully using the method of centrifugal modeling of landslide slopes with the observance of certain features. Application of the technique of centrifugal modeling allows solving problems of calculating the stability of natural slopes with complex geological structureItem The Basing of Stabilization Parameters of a Fortified Railway Bed(Дніпропетровський національний університет залізничного транспорту імені академіка В. Лазаряна, Дніпропетровськ, 2015) Petrenko, Volodymyr D.; Tiutkin, Oleksii L.; Kulazhenko, O. M.; Alkhdour, Ahmad M.ENG: Purpose. The article is devoted to stabilization parameters determination of reinforced railway bed. At the present time, the railway plays the leading role in transport system to ensure the needs of freight and passenger traffic. In modern conditions railway operation concentrates on ensuring the necessary level of track reliability, including the roadbed, this is one of the main elements of road structures. The purpose of this article is the determination of basic parameters of stress-strain state to stabilize the soil subgrade embankment by reinforced materials. Methodology. To achieve this goal the following tasks of researches were solved: the effect of reinforcing layer of geomaterial on deformation properties of soil subgrade in various design of strengthening was investigated, the distributions of stresses in the subgrade were determined, reinforced of geomaterials under state load. Experimental studies to explore the nature of the deformation model subgrade at various degrees of stress were carried out. Findings. The analysis of the results of performed experimental and theoretical studies permitted to do the following conclusions. In conducting researches determined the distribution of stresses in the subgrade reinforced geomaterials under static load. The complex of experimental studies allows exploring the nature of the deformation model subgrade at various degrees of stress. Originality. On the basis of the theoretical studies have been regarded the problem of determining the stress-strain state of subgrade reinforced geomaterials by measuring stresses in its application for step loads. Practical value. The practical value was presented by the results of evaluating the effect of reinforcing way for changing the stress-strain state of subgrade.Item The Centrifugal Modeling of Reinforcement on Approaches to Railway Bridges(Óbuda University, Budapest, Hungary, 2022) Alkhdour, Ahmad M.; Tiutkin, Oleksii L.; Marochka, Vitalii V.; Boboshko, Stepan H.ENG: The purpose of the research is to test models of sections with transient stiffness on approaches to railway bridges in the laboratory. The feasibility of the proposed methods of reinforcing the transient stiffness areas to ensure normal operation and avoid the formation of significant deformations had been tested. Centrifugal simulation of three types of reinforcement of transition section had been performed. The deformations of the models of the section with transient stiffness on approach to the railway bridge had been obtained. A comparative analysis of the results of centrifugal experiments had been performed. The effectiveness of each of the reinforcement options had been determined and the most rational method of reinforcement had been concluded.Item Controlling Stress State of a Hoisting Shaft frame in the Context of Specific Freezing Process(НТУ « Дніпровська політехніка», 2018) Tiutkin, Oleksii L.; Petrenko, Volodymyr D.; Miroshnyk, Vitalii; Petrosian, Nataliia K.; Alkhdour, Ahmad M.ENG: Purpose is to obtain regularities of a stress state of such multilayer system as neighbourhood rock mass – frozen soil – hoisting shaft frame in the process of numerical analysis to control a frame state with the selection of efficient parameters; thickness depending upon a specific frozen process specifically. Methods. Numerical analysis on the basis of a finite-element method has been implemented relying upon Pro Complex Structure CAD for Windows (SCAD) which made it possible to obtain stress state of a hoisting shaft frame and its interaction with ice-soil blocking as well as with neighbourhood rock mass soil. Findings. Hoisting shaft model has been developed. The model is based upon actual geometry and results of laboratory studies. Three blocking types (i.e. reinforced-concrete blocks, gray cast-iron tubbings, and modified gray castiron tubbings) and two soil types (i.e. sand and clayish soil at +8°С temperature) in terms of different freezing temperatures (i.e. (–2, –6 and –10°С) were analyzed numerically with the use of the SCAD. Results of the research have helped identify dependences concerning formation of a stress state of the multilayer neighbourhood rock mass – frozen soil – hoisting shaft frame system while varying properties of the listed types of a frame, neighbourhood rock mass, and ice-soil blocking. Regularities of the stressed state components deepening upon the frozen soil elasticity modulus, corresponding to its certain temperature, and elasticity modulus of a hoisting shaft frame have been obtained. The regularities connect changes in the stress of a hoisting shaft blocking in the context of specific freezing process. Originality. The obtained dependences of the stressed state of a hoisting shaft frame on the soil elasticity modulus and the material are composite spatial surfaces reflecting representatively the stressed state of such multilayer systems as neighbourhood rock mass – frozen soil – hoisting shaft frame. Practical implications. The regularities of the stressed state, determined for such multilayer systems as neighbourhood rock mass – frozen soil – hoisting shaft frame, make it possible to control stress components selecting rational geometry of a frame and its material or temperature cycle to freeze soils while applying the specific method.Item Nonuniform Stress State of a Hoisting Shaft Lining as a Result of Disturbance of the Ground Freezing Technology(EDP Sciences, 2019) Tiutkin, Oleksii L.; Miroshnyk, Vitalii; Radkevych, Anatolii V.; Alkhdour, Ahmad M.ENG: Abstract. The paper deal with the defining stress state of a hoisting shaft lining, lying in the sandy loam, when performing and disturbing the ground freezing technology. The relevance of the performed research lies in the fact that at nonuniform freezing or defrosting, nonuniform stress state is formed, which causes a significant over-stresses of the lining. To research the nonuniform stress state, a spatial finite element model of a hoisting shaft was developed, in which the case of nonuniform ground freezing was simulated. The calculation by the finite-element technique was carried out on the basis of the computational professional complex Structure CAD for Windows. In the course of the analysis, the values of stress state for linings made of reinforced-concrete blocks, B30 concrete, gray and modified castiron tubbings. A comparison of the components of stress state for sandy loam at a temperature of -2 °C (freezing), nonuniform freezing and at a temperature of + 8 °C (defrosting) was carried out. It was found that for the proposed geotechnical conditions in the form of soft, water-saturated sandy loam, it is recommended to use a lining made of gray and modified castiron tubbings.Item The Parametric Analysis of the Supported Circular Working Interacting with the Layered Massif(IOP Publishing Ltd, 2022) Alkhdour, Ahmad M.; Radkevych, Anatolii V.; Tiutkin, Oleksii L.; Bondarenko, NataliiaENG: The underground construction is based on effective and rapid building of running tunnels that connect stations. The most effective technique of building is shield-driven tunneling. It is based on the application of a tunneling shield, it means, a special aggregate that excavates the ground and builds support. Even with the fact that it holds a surrounding massif, in the weak and layered rocks it is possible the formation of subsidence trough, namely, significant deformations of the daylight area. The solution of this geomechanical problem is possible on the basis of the parametric analysis of the supported circular working interacting with a layered massif. The results of the parametric analysis allow to predict deformation in the "tunneling shield – support of tunnel – surrounding massif" system. For the parametric analysis, the authors use a numerical method of finite elements based on the complex Structure Computer-Aided Design. The calculations of six supported workings with a variation of the properties of a layered massif are carried out. The results of the stress-strain state allow introducing the matrix of parameters into the prediction calculations, enabling quickly and effectively analyze the possible change in the material of support and provide recommendations for the technology of shield-driven tunneling.Item Prediction of the Stress-Strain State of Circular Workings in a Layered Massif by Scaling(EDP Sciences, 2020) Alkhdour, Ahmad M.; Radkevych, Anatolii V.; Tiutkin, Oleksii L.; Bondarenko, NataliiaENG: The scientific and technical task for determining the stress-strain state of mine workings is complicated by the presence of a layered massif. This task assumes particular importance in the case of circular tunneling. During its operation, it is important to predict the change of the stress-strain state for the massif or to carry out the prompt determination in the change of stresses and displacements for the unsupported working. The solution of this geomechanical task allows performing geometrical matching of the working, ensuring its strength and stability in the layered massif. A numerical finite element method based on StructureCAD (SCAD) software package was used to solve it. Four geomechanical systems were calculated: "unsupported working – layered massif". Owing to the obtained results, graphs of stresses and displacements were constructed, which allow to determine these parameters for workings with different geometric parameters and χ-parameter characterizing the ratio of the elasticity modulus of the matrix and the layer. Obtained regularities of change of stresses and displacements for the unsupported working when zooming made it possible to introduce scaling-parameters, which are a dimensionless ratio of the radii for a real system and a system with a unit diameter.Item Rational Design Solutions for Deep Excavations Using Soil Nail Wall Systems(Dnipro University of Technology, Dnipro, Ukraine, 2023) Alkhdour, Ahmad M.; Yasin, Amjad A.; Tiutkin, Oleksii L.ENG: Purpose. The study aims to optimize the design and reduce soil nail length in deep excavations with a soil nail system in fast-draining soils. Additionally, it investigates the parameters influencing slope stability in fast-draining soils. Methods. Integrating field and lab data with soil nail properties and advanced modeling, this study investigates how fixed nail length, inclination and spacing affect the stability of a 20 m-deep excavation in fast-draining soil. Findings. The study findings reveal that optimal parameters, such as nail spacing and inclination angle, have been identified for reinforcing deep excavation walls, ensuring stability with minimal nail length. Notably, the stability of excavation walls can be achieved without the need to increase the length of the soil nails. The recommended parameters are characteristic of an 8-meter-long soil nail system, a 30-degree inclination angle, and a spacing of 1.5×1.5 meters. Originality. This study presents a novel perspective on the structural characteristics of soil nails by determining emphasizing nail spacing, inclination angle, and fixed nail length. It offers a comprehensive framework for designing soil nail walls in fast-draining soils during deep excavations, contributing to advancements in open-cut excavation practices. Practical implications. The study offers practical implications for designers involved in deep slope earthworks, enabling the development of efficient and rational design solutions that ensure excavation stability and prevent displacement during excavation while reducing costs and project duration.Item Regularities of Stress State of Unsupported Working Occurring in a Layered Massif(EDP Sciences, 2019) Tiutkin, Oleksii L.; Petrosian, Nataliia K.; Radkevych, Anatolii V.; Alkhdour, Ahmad M.ENG: Abstract. The paper defines the regularities of stress state of unsupported working occurring in a layered massif. The relevance of the performed research is substantiated by the importance of determining the stresses of the contour of unsupported working when the elastic modulus of the matrix and the layer is varied. Since the application of analytic methods for this case is complex, we used a numerical finite element method, implemented in the SCAD. We developed a finite-element model of the above working, where the elastic moduli of the matrix and the layer varied greatly, while its position was unchanged (the layer laying in the middle of the working). The results of the numerical analysis allowed us to build the regularities of three stress components. In order to normalize cases of elastic modulus variation, a dimensionless χ-parameter is introduced which characterizes the relation between the elastic modulus of the matrix and the layer. The obtained regularities of the stress state of the χ-parameter have a functional character and allow to determine the stresses on the contour of the unsupported working, depending on the relation between the elastic moduli of the matrix and the layer for all possible spectrum of these parameters.Item Substantiating the Parameters for a Non-Circular Structure of the Mine Shaft under Construction in a Heterogeneous Rock Massif(IOP Publishing Ltd, 2022) Alkhdour, Ahmad M.; Tiutkin, Oleksii L.; Bannikov, Dmytro O.; Heletiuk, IhorENG: Mine shafts are those workings without which the normal operation of coal enterprises and underground construction facilities is impossible. The new experience in the construction of mine shafts for the Dnipro Metro is based on the rejection of prefabricated structures. In addition, the ellipse structure of the mine shaft 15 bis of the Dnipro Metro is uncharacteristic for construction in Soviet and post-Soviet Ukraine. That is why technological advancements in the design of vertical workings for the non-circular structure require scientific justification. The complexity of operating such underground facilities under the engineering and geological conditions in the city of Dnipro is the interaction with a heterogeneous massif. Therefore, the design of the mine shaft frame involves its division into parts (the so-called pile system and shotcrete system). The finite-element models of both systems have been developed. A search for the force factors in a non-circular structure of the shaft has been carried out; the parameters for both systems have been substantiated. The results of the analysis have made it possible to scientifically substantiate the structural solutions. They enable the prediction of high strength indicators of the mine shaft under construction in a heterogeneous rock massif.