Resumo em Inglês:

Abstract Conventional wind turbine foundation design typically relies on simplified rigid assumptions that disregard soil deformability, potentially leading to conservative or inaccurate predictions. This article investigates the influence of Soil-Structure Interaction (SSI) on the behavior of shallow footing foundations supporting wind towers, using a finite element approach implemented in Strap 2013. Footing base stresses, settlements, and passive anchor forces were evaluated under multiple load combinations and compared across three methodologies: theoretical, rigid, and FEM-based. The incorporation of SSI through Winkler Spring modeling produced significantly lower stress and deformation estimates than semi-empirical methods, while field tests validated the initial design parameters. The findings highlight the practical value of SSI analysis in producing safer and more economical foundation designs for wind energy projects.

Resumo em Inglês:

Abstract Concrete sleepers face challenges in switches and crossings due to their great weight, motivating the development of lightweight alternatives. This study investigates the performance of lightweight concrete railway sleepers reinforced with steel fibers and bars. Lightweight concrete was produced using pumice aggregate, sand, cement, silica fume, and an air-entraining agent to reduce density while maintaining structural strength. Epoxy treatment was applied to enhance compressive strength. Three full-scale post-tensioned B70 sleepers were manufactured using 9.4 mm diameter steel wire reinforcement and tested under static positive bending at the rail seat and negative bending at the center. The results showed cracking at approximately 145 kN and ultimate loads up to 340 kN under positive bending, while negative bending exhibited cracking at 45 kN. The modulus of rupture exceeded 8 MPa, and the modulus of elasticity was approximately 21,000 MPa. The achieved density of approximately 1800 kg/m3 reduced the sleeper weight from 257 kg to 180 kg. The structural performance under static loading conditions was within the ranges commonly reported for prestressed concrete sleepers in published literature and AREMA reference criteria. Finite element analysis using ANSYS 2020 showed good agreement with the experimental results in terms of the cracking load, failure behavior, and ultimate capacity. Although the results demonstrate promising structural performance, they are based on a limited number of full-scale sleepers, and therefore, should be regarded as a preliminary feasibility assessment rather than a comprehensive validation of the proposed sleeper. Future studies should include a larger experimental program, fatigue testing, dynamic performance evaluation, and long-term field validation under actual railway operating conditions.

Resumo em Inglês:

Abstract Laterite blocks offer a low-carbon alternative to conventional masonry units, but their wider application is constrained by low mechanical strength and brittle behavior. Pozzolanic stabilization using kaolin and metakaolin, combined with natural fiber reinforcement, presents a promising approach to enhancing strength performance; however, the combined influence of binder type, binder content, and fiber aspect ratio on laterite block strength remains insufficiently understood. This study investigated the compressive and tensile strength behavior of laterite blocks stabilized with kaolin and metakaolin at binder contents ranging from 0% to 15%, with and without sisal fiber reinforcement at varying fiber contents and aspect ratios. Compressive and tensile strength tests were conducted on replicated specimens. Statistical analysis comprised descriptive statistics, HC3 robust two-way ANOVA, Welch ANOVA, Games-Howell post hoc tests, and effect size estimation using partial eta-squared. The binder type and content had statistically significant effects on both compressive and tensile strength, with strong interaction effects observed. Metakaolin-stabilized blocks consistently outperformed kaolin-stabilized blocks, achieving higher strength values across all binder contents. Optimal compressive strength occurred at approximately 9% binder for kaolin and 12% binder for metakaolin. Sisal fiber reinforcement significantly enhanced strength up to an optimum fiber content, beyond which strength declined. Optimal fiber contents were identified as approximately 0.75% for kaolin-stabilized blocks and 0.38% for metakaolin-stabilized blocks. Tensile strength exhibited greater sensitivity to fiber reinforcement than compressive strength. The results demonstrate a strong synergistic effect between metakaolin stabilization and sisal fiber reinforcement when the fiber content and aspect ratio are optimized. Carefully designed metakaolin-sisal systems substantially improve the mechanical viability of laterite blocks, supporting their use as sustainable, low-carbon masonry materials.

Resumo em Inglês:

Abstract In Brazil, poor road conditions and the significant reliance on road transport demand high performance from suspension systems, particularly in terms of economic efficiency and safety. Preventing failures in these components is crucial. However, product performance in practice does not always meet expectations, sometimes necessitating modifications during use. This article presents a case study involving failure analysis of a suspension component evaluated through accelerated vehicle testing. The component, made of high-strength low-alloy steel, was fabricated using gas metal arc welding. During durability testing, a liquid penetrant test revealed a crack near the weld toe. The component was immediately disassembled for a detailed failure investigation. Major imperfections were analyzed in accordance with ISO 5817. Hardness testing was conducted on the base metal and heat-affected zone. Mechanical properties, including yield strength, tensile strength, and elongation, were also verified. The study concluded that the failure was not attributable to the manufacturing process but rather to the high stress levels the component experienced. A potential solution was to update the component design. Reinforcement addition and finite element analysis calculations showed that the component would have an extended service life suitable for the application. Through these tests, the failure was identified and resolved efficiently, without requiring costly and time-consuming analyses.

Resumo em Inglês:

Abstract Recent tailings dam failures have prompted the adoption of dry stacking, where filtered tailings are compacted into stable piles. Although filtration reduces water content, residual pore water under high stress can still trigger liquefaction, raising stability concerns. This study compiles parameters of critical state soil mechanics from existing literature on filtered iron ore tailings from the Iron Quadrangle region, Minas Gerais, Brazil. The analysis reveals that the critical state parameters Mtc, λ, and Γ exhibit nearly normal distributions, influenced by mineralogy and grain shape. However, fines content, ranging from 33.3% to 98.0%, may cause slight deviations. Specific gravity and fine content distributions are bimodal, possibly reflecting processing efficiency. Correlation analysis shows a moderate positive relationship between λ and Γ (Pearson’s R = 0.720) and a minimal effect of fines content on density (Pearson’s R = 0.091). Representative values of Mtc = 1.41, λ = 0.037, and Γ = 0.933 were obtained, with Mtc and Γ showing low coefficients of variation, while λ showed a high one.

Resumo em Inglês:

Abstract This article presents a study aimed at improving the haulage unit operation in a mining company located in the Alto Paranaíba region, in the state of Minas Gerais. The objective was to evaluate the effects of increasing the truck speed limit from 40 km/h to 45 km/h, combined with mine infrastructure improvements, such as: access road classification, traffic signage, geometric road design and drainage, running surface enhancements, as well as operator training and standardization through a Work Instruction (WI). The methodology compared KPIs across two equivalent periods, from May to September of 2023 and 2024, with a data integrity index of 89.9%, using the Fastmine dispatch system. The results show an 18% increase in productivity, from 211.72 to 249.87 t/h, 13.41% reduction in cycle time, 50% decrease in incidents, and an estimated reduction of 12 tons of CO2 emissions, in addition to 3% decrease in specific diesel consumption per tonne.

Resumo em Inglês:

Abstract Microwave pretreatment has been proposed as an alternative strategy to enhance mineral accessibility in low-grade polymetallic sulfide ores while reducing the energy demand associated with comminution. This study investigates the effects of microwave heating on area-based mineral liberation, textural reorganization, and bioleaching performance of a Zn-Pb ore from Mato Grosso State, Brazil. Samples were treated at 1400 W for 5 min and characterized by X-ray diffraction (XRD), ICP OES, scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), specific surface area analysis (gas adsorption), and automated mineralogy (MLA). Bioleaching experiments were conducted using Acidithiobacillus ferrooxidans under controlled conditions. Microwave treatment induced significant microcracking and increased area-based mineral liberation in the coarser fractions (>0.5 mm), without measurable reduction in sulfide grain size, indicating predominantly intergranular fracturing. MLA results showed that microwave irradiation not only increased mineral surface exposure but also selectively modified mineral associations, particularly by reducing sphalerite-galena contacts and increasing associations with pyrrhotite and chalcopyrite in the coarsest fraction. These changes resulted in enhanced zinc extraction during bioleaching in only this size range. In contrast, no improvement was observed in the finer fractions (<0.5 mm), where sphalerite was already largely liberated. The results demonstrate that the effectiveness of microwave pretreatment is strongly particle size-dependent and controlled by both area-based mineral liberation and the reorganization of mineral interfaces, rather than solely by the generation of additional surface area.