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An Analytical Method for Determining the Stress–Strain State of a Subgrade with Combined Reinforcement
(MDPI, Basel, Switzerland, 2024) Alkhdour, Ahmad M.; Tiutkin, Oleksii L.; Fischer, Szabolcs; Kurhan, Dmytro
ENG: This article presents the fundamentals of an analytical method for determining the stress–strain state of a railway subgrade reinforced with geosynthetic material. The reinforcement described is a combined system where the geosynthetic material forms an open shell containing a layer of compacted crushed stone. The overall stress–strain state is proposed to be viewed as a superposition of two states of the subgrade. The stresses and displacements in the first state refer to the unreinforced subgrade (matrix), while the stress–strain state of the reinforcement element is determined using analytical constructs from composite theory. The dependencies of the overall stress–strain state are applied in a numerical analysis, which confirms the positive effect of reduced subgrade deformations. A small-scale experimental model further validates the accuracy of the analytical approach.
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.
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.
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.
Regularities of the Strain State of the Embankment when Varying the Vertical Element Length of Strengthening
(IOP Publishing, 2024) Alkhdour, Ahmad M.; Tiutkin, Oleksii L.; Dubinchyk, Olha I.; Miroshnyk, Vitalii
ENG: The crisis that arose during the war in the transport system of Ukraine provided an opportunity to review the concept of integrating the Ukrainian railway into the European network. Corresponding changes, which require reconstruction of the railway, including track and embankment, have been analyzed. The railway embankment needs strengthening for its normal operation. The embankment reinforced with vertical elements, namely piles, has been studied. A finite-element model of the embankment, its soil base, and the rail-sleeper grid has been created. This model shows a vertical element of strengthening with lengths of 2.0, 4.0, and 6.0 m. The results of the numerical analysis are obtained, which makes it possible to analyze the values of horizontal and vertical displacements. The values of both components of the strain state are analyzed. The results of the analysis prove that strengthening with such elements has a maximally positive effect on both components of deformation. The regularities of changes in embankment displacements, when varying the vertical element length of strengthening, are linear. They prove that the presence of piles reduces the horizontal component by 1.1 ... 1.32 times, and the vertical one by 1.1 ... 1.24 times.
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.

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