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Browsing Статті КМТ 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 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 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 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.