Статті КБВ

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Browsing Статті КБВ by Author "Alkhdour, Ahmad M."

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    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.
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    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, Nataliia
    ENG: 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.
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    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, Nataliia
    ENG: 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.
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    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.
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    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, Ihor
    ENG: 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.