Amirhossein Rostami, Hamid Chakeri, Kurosh Shahriar
et al.
Abstract Urban tunnel construction often faces challenges due to weak ground conditions or shallow overburden, making effective stabilization of surrounding soil critical. Selecting an appropriate excavation method is essential for controlling ground subsidence and convergence, which are key considerations in tunnel design, especially in densely populated areas. Excavation-induced ground movements can propagate upward, potentially causing surface subsidence and structural damage. Therefore, a systematic decision-making framework is indispensable during the design phase. This study presents a comprehensive model for selecting the optimal excavation method for Phase 4 of Tehran Metro Line 3. The model evaluates a wide range of criteria, including technical, financial, managerial, social, and geo-mechanical factors. Seven candidate alternatives were considered: Open Shield (full face) method, Slurry method, NATM (New Austrian Tunneling Method), fore-poling, twin-tunnel excavation with TBM, EPB (Earth Pressure Balance) Shield method, and Open Trench method. The Analytical Hierarchy Process (AHP) was applied to derive criteria weights, and the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) was employed to rank alternatives. Both methods consistently identified Alternative E as the most suitable excavation method. The proposed framework provides a robust and systematic approach that can be applied to future metro tunneling projects, ensuring informed decision-making under complex technical and environmental constraints.
Natalya V. Mitrakova, Elena A. Khayrulina, Anna A. Perevoshchikova
et al.
Reclamation of coal waste dumps through the establishment of a stable soil and vegetation cover on their surface contributes to the restoration of ecological systems. Therefore, studying the properties of soils in technogenic landscapes is of current importance. The problem of biological reclamation was studied in the Kizel Coal Basin area. The effectiveness of reclamation was evaluated on several sulfide coal waste dumps. The reclamation methods, as well as the period of soil-vegetation cover formation, varied. Agrochemical properties of the dump soils were studied using unified methods. The NDVI (Normalized Difference Vegetation Index) was calculated based on Sentinel-2 and Landsat 7,8 images. To assess biological activity, phytotesting was used. The lithostrats ranged from slightly acidic to neutral (рН–Н2О = 6.1–6.8); the embryonic soil showed a slightly alkaline reaction (7.9). The embryonic soil, due to the presence of coal particles, had the highest organic matter content (12–7.7%). Depending on the "age" of the soil, the amount of organic matter in the lithostrats varied: for the 7-year-old lithostrat, it ranged from 2.4 to 8.9%, while for the 4-year-old lithostrat, it was less than 1%. The absorption capacity of the lithostrats was similar to that of the background soil. The dump soils were characterized by low levels of nutrients (NPK), with the 4-year-old lithostrat having the lowest N content. The dump soils demonstrated favorable conditions for plant growth, as evidenced by the height and biomass of cress and oats. The calculated NDVI for all dumps ranged from 0.4 to 0.6, indicating the presence of a stable vegetation cover. The implemented reclamation measures proved to be effective.
Raja Thandavamoorthy, Jagadeesh Kumar Alagarasan, Vinayagam Mohanavel
et al.
This study investigates the incorporation of boron carbide (B4C) filler particulates into a kenaf fiber-reinforced epoxy matrix to explore its potential in lightweight applications, focusing on antimicrobial effectiveness, mechanical integrity, thermal properties, and microstructural characteristics. The composite material was formulated by blending varying seven different concentrations of boron carbide (0–50 g) and kenaf fibers (KFs) with an epoxy resin, aiming to achieve a balance between mechanical strength and minimal weight. Antimicrobial test revealed that the composite material, consisting of kenaf fiber reinforced with B4C particulates, exhibited significant antibacterial activity against common pathogens. Mechanical testing indicated that the addition of boron carbide and kenaf fibers significantly improved the tensile strength and flexural rigidity of the composites. Specifically, enhancements in tensile strength and flexural modulus were quantitatively analyzed, showing notable increases compared to the base epoxy resin. Scanning Electron Microscopy (SEM) was employed to examine the fracture surfaces following mechanical testing, revealing improved interfacial bonding between the kenaf fibers and the epoxy matrix due to the presence of boron carbide. This microscopic analysis also highlighted areas where stress distribution was optimized, contributing to the composite's enhanced mechanical properties.
Ni–Al based coating is one of the common high temperature and corrosion resistant protective coatings. In the present paper, the effect of Si content on the formation of Al2O3 layer and the corrosion resistance of Ni–Al coating to chloride molten salt was studied. The research results show that the Ni–Al coatings with varying Si content mainly form NiAl2O4 and Al2O3 oxide layers after pre-oxidation, and form a three-layer structure after molten salt corrosion. The appropriate amount of Si added to the Ni–Al coating can promote the formation of the α-Al2O3 layer during pre-oxidation and thermal corrosion, improving the corrosion resistance of the coating to high temperature chloride molten salt, and hindering the diffusion of Cr elements. Particularly, the Ni–Al coating with Si content of 1.2 at.% has the thickest and densest Al2O3 protective layer, showing the best corrosion resistance. The simulation results shows that compared with the Ni–Al coating without Si, the Cl atoms in the Si-added Ni–Al coating need to overcome greater energy barriers to diffusion during the molten salt corrosion process, which also indicates that the addition of Si can improve the corrosion resistance of the coating.
6061-T6 aluminum alloy plate (3 × 150 × 300 mm3) was welded by tungsten inert gas (TIG) welding. The welding process methods are single-pass welding process and full welding process respectively. The effects of different welding processes on the performance of TIG welding 6061-T6 aluminum alloy were compared and studied. The effects of microstructure and precipitation on the microhardness and tensile strength were analyzed by optical microscope, scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS) characterization, electron backscattering diffraction (EBSD) characterization, microhardness and tensile test. The microstructure of the weld zone is mainly composed of aluminum solid solution (α-Al) dendritic structure and Al–Si eutectic structure. Through EBSD characterization analysis, the average grain size of the weld zone of the full welding process and the single-pass welding process is about 45 μm and 55 μm, and the grain size of the heat-affected zone and the weld zone of the two welded joints does not change significantly. The hardness curves of the two welded joints have the same distribution trend, which is roughly 'W' type distribution. In the tensile test, the tensile strength of the single pass welding process is lower than that of the full welding process, and the fracture of the tensile parts is dimple structure, which is ductile fracture. Through analysis and comparative study, the full welding process is better than the single-pass welding process when welding 6061-T6 aluminum alloy sheet.
AbstractTailings transport system design is generally based on identifying the minimum and maximum process boundary conditions for pump selection and pipeline sizing. The approach is robust and well-proven. However, the approach has the potential to skew selections to operating scenarios that have a very low likelihood of occurring, such as the combination of high solids throughput and low tailings solids concentration. The approach can result in a tailings transport system design that is overly conservative. A probabilistic method-based approach captures the independent variability of design inputs and the combined likelihood of outcomes. This approach identifies the process conditions that have the highest likelihood of occurrence and are most applicable to equipment and pipeline selections. An outline of a probabilistic-based approach to tailings transport system design and the resulting selections is provided in this article. The probabilistic-based system design is compared to the outcomes from the traditional approach. The benefits and challenges to this approach are discussed and recommendations for utilizing this approach for tailings transport system design are provided.
In this study, the phase composition, morphology, and element distribution of Mg impurities in a low-grade titanium slag and in its chlorinated residue after carbochlorination were identified using XRD, SEM-EDS, and MLA. Most Mg impurities existed as anosovite, rutile, titanaugite, and Ti silicate phases before the carbochlorination process. The thermodynamic analysis revealed that the chlorination tendencies of Mg, Ti, Ca, Fe, and Mn oxides in the original titanium slag was much higher than those of Si and Al oxides in the temperature range of 700–850 °C. In addition, the binary phase diagram analysis indicates that the magnesium chloride (MgCl2) byproduct formed Na2MgCl4 eutectic salts in the NaCl-based salt bath. The carbochlorination experiments of the Mg-bearing titanium slag show that the chlorination ratio of magnesium oxide was above 93% under the suitable industrial conditions used for the extraction of titanium from Mg-bearing titanium slag. In addition, the formation of Na2MgCl4 eutectic salts after carbochlorination was confirmed, indicating that the negative effect of MgCl2 on the chlorination process was effectively eliminated. The Mg impurities in the chlorinated residue existed as titanaugite, quartz, chlorite, and rutile phases. Furthermore, we found that the carbochlorination of Mg-bearing titanium slag in chloride media effectively improved the comprehensive utilization efficiency of the Mg-bearing titanium slag. We believe that the proposed carbochlorination mechanism of the Mg-bearing titanium slag will provide thorough understanding and useful guidance on the practical industrial application of Mg-bearing titanium slag.
For underground mines, two major designs that need to be optimised are the stope boundary and the access layout. The optimisation of these two components cannot be done independently as ore extracted from stopes is transported to the surface via the access network. Different stope locations result in different associated access development costs. This paper describes a proposed integrated optimisation model to optimise stope and access layouts simultaneously. The interactions and interdependency between stopes and access are ensured by a dynamic access development cost analysis based on recursive computations. Mixed integer non-linear programming is used to maximise the overall economic value subject to the constraints of generating optimal stopes and access layout, which is solved by a Genetic Algorithm modified for computational efficiency. A stratiform gold deposit is used as a case study to demonstrate that the new approach can provide a more profitable solution compared with traditional approaches.
In this study, the soft magnetic properties of Fe<sub>78</sub>Si<sub>9</sub>B<sub>13</sub> amorphous magnetic powder cores (AMPCs) were enhanced by coordinately adjusting the technological parameters, including the particle size distribution, molding pressure, and coating agent content, in the industrial condition. The results show that the optimized comprehensive soft magnetic properties of the Fe<sub>78</sub>Si<sub>9</sub>B<sub>13</sub> AMPCs could be obtained under the following process conditions: (1) the distribution of particle size is 20 wt.% for 140–170 mesh, 70 wt.% for 170–270 mesh, and 10 wt.% for 270–400 mesh; (2) the molding pressure is in the range of 2.35–2.45 GPa; and (3) the additive amount of sodium silicate is 1.5 wt.%. After the collaborative optimization, the AMPCs’ compact density, <i>ρ</i>, the effective permeability, <i>μ<sub>e</sub></i>, and the residual effective permeability at the applied magnetizing field of 7.96 kA/m, <i>μ<sub>e</sub></i>@7.96 kA/m, increased from 5.61 g/cm<sup>3</sup> to 5.86 g/cm<sup>3</sup>, from 58.13 to 77.01, and from 40.36 to 49.57, respectively. The attenuation ratio of the effective permeability, when in the frequency band of 20–100 kHz, was less than 0.85%. The core loss at the 50 kHz for the maximum magnetic flux density of 0.1 T reduced from 380.85 mW/cm<sup>3</sup> to 335.23 mW/cm<sup>3</sup>. This work will encourage the further application of Fe-based AMPCs in the fields of electronics and telecommunication.
Prakash Kumar Sahu, Nikhil P Vasudevan, Bipul Das
et al.
Research work presented in this study has the primary target of exploring joint attributes of AZ31 magnesium alloys using friction stir welding process with a modified tool referred as bobbin tool. Effects of inert and open atmosphere on mechanical properties are evaluated over a wide range of welding speed and tool rotation speed. Comparison of the research findings from the inert atmosphere bobbin tool were made with the traditional process of friction stir welding. The results depicted improved joint properties for inert atmosphere welding. Low and intermediate range of tool rotational speed is found to be favorable for bobbin tool friction stir welding without and with an inert medium, respectively. Controlled atmosphere due to inert medium leads to less oxidation of the AZ31 Mg alloy leading to superior joint properties. Microstructural investigations are also made with the aim of evaluating the impact of bobbin tool and inert medium on joint properties. In each aspect for joining of AZ31 Mg alloy, bobbin tool with inert medium is found to be an effective solution for joining with improved mechanical properties compared to without inert bobbin tool as well as conventional tool friction stir welding. Keywords: Mg FSW, Bobbin tool, Process parameters, Mechanical properties, Fractography, Microstructural characterization
Se presentó un sistema informático educativo sobre efemérides de la Física que han tenido estrecha relación con la Física. Para ello se utilizó el lenguaje de programación Borland Delphi Versión 6.0. Un total de 355 hechos pueden ser localizados, por años, meses, días, personalidad, materia, así como por etapa en que ocurrió, permitiendo realizar combinaciones entre estos elementos. De este modo se contribuye a la motivación para el estudio de la Física y así lograr un mejor aprendizaje por parte de los estudiantes durante la clase.
Clodualdo Aranas, Samuel Rodrigues, Ameth Fall
et al.
The double differentiation method overestimates the critical stress associated with the initiation of dynamic transformation (DT) because significant amounts of the dynamic phase must be present in order for its effect on the work hardening rate to be detectable. In this work, an alternative method (referred to here as the free energy method) is presented based on the thermodynamic condition that the driving force is equal to the total energy obstacle during the exact moment of transformation. The driving force is defined as the difference between the DT critical stress (measured in the single-phase austenite region) and the yield stress of the fresh ferrite that takes its place. On the other hand, the energy obstacle consists of the free energy difference between austenite and ferrite, and the work of shear accommodation and dilatation associated with the phase transformation. Here, the DT critical stresses in a C-Mn steel were calculated using the free energy method at temperatures ranging from 870 °C to 1070 °C. The results show that the calculated critical stress using the present approach appears to be more accurate than the values measured by the double differentiation method.
LHD’s are expensive vehicles; therefore, it is important to accurately define the financial consequences associated with the investment of purchasing the mining equipment. This study concentrates on long-term incremental and sensitivity analysis to determine whether it is feasible to incorporate current battery technology into these machines. When revenue was taken into account, decreasing the amount of haulage in battery operated equipment by 5% or 200 kg per h amounts to a $4.0 × 104 loss of profit per year. On average it was found that using battery operated equipment generated $9.5 × 104 more in income annually, reducing the payback period from seven to two years to pay back the additional $1.0 × 105 investment of buying battery powered equipment over cheaper diesel equipment. Due to the estimated 5% increase in capital, it was observed that electric vehicles must possess a lifetime that is a minimum of one year longer than that of diesel equipment. Keywords: Sensitivity analysis, Underground mining vehicles, Battery power, Battery mining equipment, Economic evaluation
Orlando Belette-Fuentes, Rafael Zamora-Matamoros, Daimel Caballero-Echevarría
A mathematical model’s system for optimizing the efficiency for sampling exploration and exploitation networks in lateritic nickel and cobalt deposits, located in the north-eastern province of Holguin, was developed in the “Centro de Investigaciones del Níquel”. This system includes a new reservoir model based on multivariate substantial classification using the Markov model for discrete stochastic processes. As a result of the application of these models a linear optimization problem was obtained comprising an objective function, several constraints as inequalities and an additional restriction in the form of equality linked to the number of wells to be selected. The
generated problem has polynomial computational complexity and because no accurate methods exist to solve it, an automated tool that brings up feasible solutions was developed based on genetic algorithms.