Abstract in English:

AbstractThis article assesses the behavior of full-scale static load tests (SLTs) conducted with instrumentation for strain measurements, in order to provide insights into the pile load transfer curves along its length. A collection of instrumented SLTs from a specific region offers a valuable dataset for the geotechnical community, which can be leveraged for machine learning-based neural network studies and probabilistic-statistical analysis, ultimately enhancing the reliability of regional semi-empirical methods. This study presents an analysis of a database containing the results of 80 instrumented SLTs conducted on CFA (continuous flight auger) piles in the metropolitan area of Goiânia, Goiás, Brazil, spanning from 2016 to 2022. It establishes correlations between the pile’s maximum skin friction (qlmax) and soil resistance, as well as between the pile shaft and pile base resistances, and relative displacement at the pile-soil interface (δint). The geotechnical surveys accompanying each SLT are also included in the database under examination, aiding in the definition of a representative geotechnical profile of Goiânia’s soil. The qlmax values derived from the database exhibit significant dispersion compared to the semi-empirical methods commonly employed in Brazil. Additionally, these values span a broad range of δint, with considerably lower values for the superficial, porous, and structured layer of sandy clay compared to the deeper layers.

Abstract in English:

AbstractThe increasing concern over the scarcity of natural resources has driven the search for more sustainable structural designs. Among the various alternatives, steel-concrete composite cellular structures have emerged as a good solution for large spans, combining the strength properties of concrete and steel without significantly increasing the structure's mass. This article presents a formulation for the optimization of steel-concrete composite cellular beams aimed at minimizing carbon dioxide (CO2) emissions. In addition to the materials used, emissions from manufacturing processes, specifically cutting and welding of profiles, are also considered. The problem was addressed using Particle Swarm Optimization (PSO) and the Grey Wolf Optimizer (GWO), and numerical examples are provided to investigate the advantages of the proposed formulation compared to steel welded beams. Among the results, it was observed that similar solutions were obtained with both optimization methods. In addition, varying the span of the beams in a range of 5 to 17.5 m, it was possible to identify structural profiles and configurations that are more efficient regarding weight and environmental impact. The best results in almost all the spans are from the Litzka beam, except for the 17.5 m span, which was the Peiner beam that had the lowest CO2 emission.

Abstract in English:

AbstractThe cylindrical shell-medium (soil or rock) contact problem solution is typically achieved through numerical methods, where the modeling or approximation of the medium’s behavior is usually made considering it as an elastic deformable foundation that does not react to tensile forces (unilateral contact problem). The purpose of this study is to develop a computational tool, using the Fortran programming language, aimed at a nonlinear problem involving cylindrical shells or panels under contact constraints imposed by a deformable soil. The analyses considered encompass unilateral and bilateral contact constraints imposed by the medium. The chosen method for discretizing the partial differential equilibrium equation contact problem is the finite difference method (FDM). This study considers the structure-medium contact problem in situations where the medium is approximated by the Winkler type model (one-parameter) or Pasternak type model (two-parameters), and the bilateral and unilateral contact situations are assessed. The research compares the efficiency of solution methods and highlight the strengths and weaknesses of each numerical approach proposed. The focus on FDM is particularly relevant for simulating the elastic base models commonly used in research.

Abstract in English:

AbstractThe discrete element method (DEM) has proved to be a valuable tool in understanding the mechanisms of soil friction mobilization and compressibility, Many problems, such as particle breakage and erosion, can be better understood using DEM. The article uses DEM to simulate the results of triaxial tests performed on alluvial sand. Developing new routines and implementing them in a former DEM code made it possible to perform triaxial test simulations without using additional material to represent the rubber membrane, making triaxial test modeling by DEM less complex and more accurate. Predicted and experimental results presented good adherence, and classical works from literature corroborated the variation of the macroscopic friction angle with soil porosity in the modeling. The friction angle between particles was close to that obtained between two adjacent quartz particles (main sand component), 26°, highlighting the result's consistency. Furthermore, samples tended to expand under lower confinement stress and compress for higher confinements for the same porosity. The model evaluation proved that it renders results of the sand's mechanical behavior under varying internal friction angle, porosity, and particle size that are coherent with the vast experimental evidence in the geotechnical field. The obtained results illustrate the model's potential for use in geotechnical problems, mainly in the case of settlement predictions under shearing, where volumetric soil strains play an essential role.

Abstract in English:

AbstractThe year of construction is an essential factor in assessing the condition of bridges, as it directly influences the prediction of their deterioration and the analysis of their load-bearing capacity over time. In addition, this data is fundamental for algorithms that deal with missing information, such as that related to design standards. This study proposes and validates an algorithm to estimate the year of construction of Brazilian bridges based on three main characteristics: design vehicle, barrier type and width. The aim of the algorithm is to fill this information gap and provide managers with information to manage these infrastructures. An analysis of 5,000 bridges in the Bridge Management System revealed that 41.7% of them had no record of the year of construction. During validation, the algorithm showed robust performance, achieving a hit rate of 87.82 percent and a mean absolute error (MAE) of 5.20 years. After adjustments, the MAE was reduced to 4.45 years, with accuracy rates of 99.46% (±10 years) and 79.62% (±5 years). In practice, the algorithm successfully estimated the year of construction in 81.87% of cases, with the majority of bridges built in the 1970s (64.16%). These results provide a solid basis for more accurate deterioration predictions and more reliable load capacity assessments, contributing to more efficient and safer bridge management.

Abstract in English:

AbstractIn the industrial production of aluminum through the Bayer process, two main pollutants are generated, red mud and carbon dioxide (CO2). Conventional processes for treating polluting waste include the neutralization of red mud with hydrochloric acid (HCl) and the capture of CO2 with ethanolamine (CH2(NH2)CH2OH). However, the CO2 generated can be used to neutralize the red mud, allowing the simultaneous treatment of two harmful substances and reducing the amount of HCl required to neutralize the red mud. The solvent present in red mud is the residual alkaline liquor from the Bayer process, which absorbs CO2 in a secondary stage, but is not yet considered as a pollutant treatment process. From this perspective, the treatment of two polluting substances (red mud and CO2) can be carried out in aluminum production plants with lower energy consumption. In the present study, bench and pilot-scale tests were carried out to verify the efficiency of CO2 adsorption by red mud at a temperature of 25 °C. Among the results of bench tests, 84.05% CO2 absorption by red mud was obtained. And on a pilot scale, using a bubble column and continuous flow, an efficiency of 96.80% CO2 absorption was observed with red mud. The study also found that among the most significant variables in this type of treatment are the solid content and mechanical speed.

Abstract in English:

AbstractIn the present work, the Halide Activated Pack Cementation (HAPC) was adopted to form protective aluminide coatings due to its versatility and low cost. Codeposition of Al and Si on Mar-M246 was performed by HAPC using two different cements constituted of 75 wt.% Al2O3 and 25 wt.% of a mixture formed in different weight ratios of (Al: Si): PM I (50:50) and PM II (72.5:27.5). The coatings are composed in outer part of NiAl and Ni2Al3 phases with significant presence of Si on PM I. After 200 h of oxidation test at 1000 °C, the samples coated by PM I and PM II exhibited the best performance than uncoated one, with mass gains near 0.3 mg/cm2, which is half times the mass gained by uncoated alloy. All coated samples were characterized before and after the oxidation test by SEM, EDS and XRD techniques. The exposure of the coated to high temperature led to the formation of Al2O3 and a modification of the coating morphology by the dissolution of the Ni2Al3 phase.

Abstract in English:

AbstractThe main objective of this study is to determine the corrosive behavior of class 321 austenitic stainless steel by carrying out laboratory corrosion tests using the potentiodynamic polarization technique, using a standard solution of sodium chloride (NaCl) and an ammonium chloride solution (NH4Cl), both solutions at a concentration of 3.5% wt./v. Ammonium chloride salt is formed in the reaction sections of gasoline and diesel hydrotreating units by the reaction between ammonia and hydrochloric acid present in the cargo to be processed. It is a highly aggressive form of corrosion on various types of metallic materials, commonly used in the construction of equipment and pipelines in the oil and gas industry. Its damage can cause unscheduled downtime, loss of equipment containment, and loss of production, as well as potentially causing damage to people, installations, and the environment. The ASTM 321 steel showed higher corrosion resistance in ammonium chloride solutions than the ASTM 304 and 316L steels. During the general maintenance shutdown of a gasoline hydrotreating unit at a Brazilian oil refinery in 2024, the industrial application of this material will be demonstrated in a heat exchanger tube bundle for the effluent from the reaction section, made of 321 austenitic stainless steel.

Abstract in English:

AbstractThe concentration of the igneous phosphatic ores is determined through froth flotation. However, the fine particles present in the pulps cause a decline in selectivity and metallurgical recovery because they can cover thick particles and increase the consumption of reagents. Therefore, the objective of this study is to evaluate dispersion during the desliming and bench flotation of low content phosphatic ores. Sodium hexametaphosphate, sodium silicate, DP-304A, and lauryl ether sulfate were tested as dispersants in a Denver mechanical cell. Saponified soybean oil was used as the collector and cassava starch was gelatinized as a depressant. Desliming combined with flotation, dispersion combined with desliming and flotation, and dispersion combined with flotation were evaluated. The optimal conditions for desliming and flotation were the use of sodium silicate at a dosage of 3000 g/t. Sodium silicate served as both a depressant and a dispersant. Statistical analysis showed that desliming with flotation increased the content and recovery of apatite. Dispersion resulted in decreased metallurgical loss during desliming and increased apatite recovery during flotation.

Abstract in English:

AbstractThe opening and development of mines without previous planning can generate costly environmental liabilities that are difficult to recover. The Osamu Utsumi Mine was responsible for extracting uranium until 1995 in open pit mining operations. The sulfide rocks with residual ore are exposed and their interaction with groundwater and rainwater can generate acid drainage. This study aims to identify possible sources of acid drainage in the SE front of the pit using the geophysical methods, such as electrical resistivity and induced polarization. The analysis of the two-dimensional sections generated with the geophysical results allowed the recognition of low resistivity zones (<118 Ω.m) and high chargeability areas (>20 mV/V), interpreted as the presence of water and sulphide concentration, respectively. This combination of factors contributes to the generation of acid drainage. By determining the possible acid drainage generation points, the mine decommissioning process can become faster and more effective.

Abstract in English:

AbstractSome open-pit mining operations rely heavily on stockyards as temporary storage areas. In addition to its conventional purpose, it is regarded as an excellent way for blending deposited material, which reduces fluctuation in the grade of material provided to the processing plant. However, traceability of the grade of material in the stockyard poses considerable issues due to the necessity for more specific information about the stored material. This study aims to create a block model for the stockyard using programming based on an integrated database, incorporating critical information from fleet management systems, geology, and topography. The model is generated in a widely compatible format that can be imported into any planning software for further analysis. Geostatistical estimation was excluded from this investigation due to the uneven distribution of mineral grades and the low precision of truck GPS. Subsequently, short-term planning for stockyard reclaiming is carried out using block modeling, primarily satisfying the beneficiation plant's production demands. Results showed 100% adherence to permissible limits of plant feed grade compared to 33% in the absence of incorporating variables. Properly integrating these components aims to improve operational efficiency and the quality of material input to the processing plant, aiding mining engineers in managing the stockyard and developing more robust short-term plans.