Abstract in English:

Abstract Brazilian standards regarding structural masonry does not consider the effect of bedding mortar properties on the strength and failure mode of masonry. Thus, the objective of this study was to evaluate the effect of bedding mortars with low strength and high entrained air content on the stress-strain curve and failure mode of masonry prisms under compression. The prisms were constructed from concrete or ceramic blocks (hollow core or solid) and mortars with low strength and high entrained air content. Three types of mortars were tested, one dry pre-mixed mortar and two ready-to-use, with open times of 36 and 72 h. All physical and mechanical properties of the materials were determined following Brazilian standards. Strain under compression was evaluated on two-block high prisms equipped with linear variable differential transformers (LVDT) placed on opposing faces. Results pointed out that both strength and strain of ceramic block prisms were affected by mortar strength. On the other hand, the concrete block prism strength was affected by mortar strength and porosity while strain was largely affected by mortar porosity. Failure modes differed between ceramic and concrete block prisms: ceramic prisms cracked from mortar joint crushing and resulted in structural failure, while concrete prisms lost block-mortar adhesiveness from joint crushing. Therefore the prism was no longer a single entity but was still able to withstand the axial compression stress test.

Abstract in English:

Abstract This article focuses on numerical thermos-structural behavior evaluation of composite steel and concrete beams under fire conditions. Several models of composite beams are analyzed, changing the following parameters: steel beam, span length, load level, slab thickness, concrete and steel strength. The numerical models, validated by experimental results of other authors, were developed using the finite element method on software ANSYS and the language APDL. It was observed that the structural load level is the main parameter that affects the structural behavior of composite steel and concrete beams under fire conditions.

Abstract in English:

Abstract This article describes the development and validation of a linear viscoelastic model 2S2P1D for silty sand mixed with 16% asphalt emulsion. Experimental data from creep tests were employed to propose and validate the model. The methodology involved soil collection and characterization, after which it was mixed with asphalt emulsion, and exposed to air for 24 hours, followed by the Superpave rotary compaction of the soil-emulsion mixture. Test samples were then exposed to air until a constant density loss was detected, followed by conducting complex modulus tests at thirty different temperature-frequency pairs. Based on these results and the smooth construction of the master curve of the mixture, it was confirmed that the material studied is thermorheologically simple, and the parameters of the linear 2S2P1D model were defined. After defining the constitutive model, a creep test was conducted on the material at a temperature of 0°C for 7200 seconds. The model exhibited satisfactory adjustments to the creep test results, even in the nonlinearity domain. The differences between the strains predicted by the model and those defined experimentally were considered within an acceptability limit for geotechnical materials, and the introduction of a modulus decrease coefficient of approximately 65% was sufficient to simulate the nonlinearity effect in the 2S2P1D model.

Abstract in English:

Abstract The structural optimization of trusses is a complex problem that can be affected by many different factors. In this research, the authors investigated the optimization of trusses performing a geometric nonlinear analysis under dynamic loading, using two different metaheuristic algorithms: the Genetic Algorithm (GA) and Particle Swarm Optimization (PSO). The objective function was to minimize the weight of the structure. A number of benchmark test problems for spatial trusses considering a geometric nonlinear analysis, and dynamic loading are analyzed to verify the performance of the optimization algorithms. The results showed that both algorithms were able to find efficient solutions to the optimization problem and suggest that the choice of the optimization algorithm can have a significant impact on the performance of the optimization process.

Abstract in English:

Abstract Drill and Blast is one of the most utilized excavation methods due to its cost and adaptation capability. One undesirable feature, however, is the contour shape quality of the blasted cavity. It is usually larger and rougher than planned. This characteristic is related to the crack generated by blasting that propagates until it finds a discontinuity. Some methods for overbreak and roughness control are used but they are far from perfect. One option is to replace explosives with the High-Power Abrasive Water Jet (HPAWJ) Technique for rock cutting the perimeter; a necessary step before execution of the Pre-Splitting Technique. These two techniques can create one free surface, with good roughness, capable of avoiding the crack propagation during the blast process. In this article, through a qualitative comparative research, an adaptive cycle is proposed, based on Drill and Blast, that uses HPAWJ for cutting the perimeter. In addition to the improvement on the tunnel wall roughness, this change can reduce the excavation-damage zone and the overbreak, which leads to a reduction of the amounts of shotcrete and muck, consequently reducing the need for transportation.

Abstract in English:

Abstract In fires, situations in which high temperatures are evident, it is noticed that the materials have their physical and resistance properties deteriorated. In the structural systems considered under these fire conditions, there is a considerable loss of load capacity and strength. Therefore, the temperature progression evaluation in the structural elements’ cross-sections is essential for understanding their behavior under high temperature. Thermal analysis allows determining the complete temperature field in the element cross-section from boundary conditions provided by some adopted fire model, taking into account the variation in the material thermal properties with the temperature increase. Timber, being a combustible material, requires knowledge and adequate modeling of its behavior and performance when kept in a fire situation. This anisotropic material, with fibers containing irregular flammable knots, has been widely used in civil construction. Thus, this research aims to carry out numerical thermal analysis through the Computational System for Advanced Structural Analysis/Fire Analysis (CS-ASA/FA), with the preand post-processing graphical tools provided by the GiD platform, of timber structural elements’ cross-sections used in civil construction. The results obtained are compared with those of literature, demonstrating the ability of this CS-ASA/FA module and GiD coupling to provide the necessary information for the evaluation of timber cross-sections in a fire situation.

Abstract in English:

Abstract This article presents an application for failure probability in long-pipeline gas systems through the development of trend curves over time for the attributes of corrosion wear, which are related to the length, width, and depth of the defect. In addition, Risk-Based Inspection (RBI) is applied in the most favorable numerical failure values according to the location of the defect, with the aim of analyzing the structural reliability and the expected useful life of the gas pipeline. To do this, it was necessary to use the data provided by pig readings in 2008, 2012 and 2018 by an instrumented pig, type Magnetic Flux Leakage (MFL), inspecting a gas pipeline with the finality to measure wall thickness. The 56 km long and 18 in diameter pipeline is partly onshore and partly offshore. Also, the pipeline anomalies are standardized according to the standards established in POF (2016). It is important to emphasize that the methodology described in this article can be used in the industry where the prevention of leakage incidents, the predictability of maintenance, and the elaboration of the respective inspection plans are required, since it has been theoretically possible to calculate the probability of failure in time beyond the respective impact on risk for the operational variables presented.

Abstract in English:

Abstract The extraction of gold from refractory gold mineral deposits is becoming increasingly necessary. The presence of gold encapsulated within the crystalline matrix of iron sulfide minerals, such as pyrite, pyrrhotite, and arsenopyrite significantly reduces the efficiency of cyanidation. Therefore, the use of oxidative pretreatments, such as calcination, pressure oxidation, or bacterial leaching, enables a high gold recovery from refractory deposits. Calcination has been widely employed. However, it has a high energy cost and environmental issues due to the release of toxic gases containing arsenic. In the treatment of refractory gold ores containing arsenic, pressure oxidation (POX) represents an attractive approach for arsenic immobilization, since the conditions are suitable for both sulfide oxidation and the formation of stable arsenates. In the present study, tests of alkaline and acidic pressure oxidation followed by sodium cyanide leaching were conducted on a composite sample of the Faina Project, owned by Jaguar Mining Inc., located in de northwest portion of the Iron Quadrangle, Minas Gerais, Brazil. The mineralization is hosted by metabasalts and komatiitics metabasalts of an archean metavulcano sedimentary sequence, in the Greenstonebelt Pitangui. The tests demonstrated that it is possible to achieve a 98.40% gold recovery using a concentrate initially containing 12% sulfur, which underwent acidic oxidation with a 0.28 M H2SO4 solution at a temperature of 220°C, oxygen pressure of 500 kPa, and a residence time of three hours. This result was 19.19% higher than that obtained in an alkaline medium using a 3.0 M NaOH solution.

Abstract in English:

Abstract To produce metallic copper with high quality, it is important to have all impurities present in the electrorefining cell under control. Antimony is present in the copper refining electrolyte as an impurity coming from pyrorefinated anodes. The antimony capture from the electrolyte is usually carried out by an ion exchange (IX) process. After that, an elution stage of Sb by means of a hydrochloric acid solution is accomplished, being the antimony eluate liquor sent for precipitation with gypsum and then landfilled. This article proposes an alternative to this classical antimony co-precipitation process, using a membrane electrolysis (ME) cell with a cation exchange membrane. This alternative route allows the recovery of metallic antimony at the ME cathode. ME experiments on lab scale were conducted to recover antimony as the cathode and using as an electrolyte, a real industrial hydrochloric eluate from the IX process. The ME tests were carried out with cathodes of stainless steel or cooper, at 200 and 300 A/m2, room temperature, without organic additives, and with different cell designs. The best results obtained were a stainless steel 316L cathode, faradaic efficiency of 92.46 % at current density of 200 A m-2, voltage 3 V and cathodic composition of Sb 75%. These results were obtained in a cell with the catholyte compartment closed at the top, showing the importance of the fluid-dynamic effect of the cell design on the Sb recovery.

Abstract in English:

Abstract One of the key objectives in short-term mine planning is to establish a sequence of contiguous blocks organized into diglines, each characterized by consistent low-grade variability and minimal fluctuations, ensuring a stable output. This practice guarantees a steady and reliable supply of ore to the processing plant across various operational phases, each phase outlined for clarity. The creation of this digline requires the generation of multiple random models and involves choosing a model whose grade histogram aligns closely with the predefined criteria. In stochastic mine planning, geological uncertainty and transfer functions are employed to propagate the risk into the mining schedule focusing on grade control. This is accomplished by opting for blocks that present the lowest risk associated with grade uncertainty, a process enhanced by prioritizing blocks situated in geopositions with a proven high probability of occurrence. This study unveils detailed simulation models, clearly outlined digline selection methodologies, and a thorough optimization process, each aspect exemplified within the practical context of a phosphate mine. Our findings confirm the viability of this approach in real industry practice.

Abstract in English:

Abstract The Fundamental Sampling Error (FSE) is the main error defined by Pierre Gy’s Theory of Sampling (Gy, 1967; 1979; 1992) and is related to the constitution or intrinsic heterogeneity (IH) of the ore. Even if a sampling procedure is considered ideal, this error can never be eliminated. To calculate the FSE for a certain sample taken from a certain fragmented lot, crushed to a certain size, the intrinsic heterogeneity of the lot (IHL) must be estimated, which can be done theoretically applying the Gy’s factors, or experimentally performing heterogeneity tests. FSE calculation allows the optimization of sampling protocols, the calculation of minimum sample masses, as well as the estimation of the precision of a sampling procedure or equipment. FSE represents the zero-dimensional heterogeneity of a lot and it is of upmost importance to calculate it. However, there is another type of heterogeneity related to one-dimensional lots, i.e., the material flow on conveyor belts or in pipelines. This one-dimensional heterogeneity can be characterized with variography, by estimating the Heterogeneity Fluctuation Error (HFE). Obtaining reliable information on ore grades at the plant feed is a great challenge for mining operations. When the precision of the plant feed grade is low, incorrect decisions can be made and may decrease the process yield. In order to estimate both FSE and HFE for a Brazilian niobium ore, a sampling campaign was carried out at the plant feed. Results indicated that the 5-minute sampling interval was appropriate, resulting in a low relative standard deviation of HFE, i.e., 2.26% for Nb2O5, considering a 95% confidence interval. This article shows how to estimate the zeroand one-dimensional heterogeneities of ores and how important it is to define the precision associated with the grade estimates for process control, metallurgical accounting and reconciliation purposes.

Abstract in English:

Abstract This article proposes an industry-specific set of modifying factors for managing mineral resources and reserves for construction aggregates. To gain insights into the regional characteristics of the aggregate market and the requirement of situating mining operations close to urban centers, an application example was developed. It considers the two largest urban concentrations in Brazil to present findings on how the supply and demand of sand and crushed stone occurs in these regions and their relationship with the management of mineral resources and reserves. Furthermore, a conceptual simulation was conducted to showcase how limitations on mining areas can influence the conversion of mineral resources into aggregate mineral reserves. This simulation took into account different scenarios of environmental and social restrictions, which were identified as the primary bottlenecks in the quarries. The findings of the research highlighted the increasing significance of governmental and ESG-related modifying factors in aligning aggregates extraction activities co-existing with other land use in the vicinity. Finally, this article proposes a new indicator for classifying mineral reserves in this sector.

Abstract in English:

Abstract The purpose of this article is to show the evolution of international reporting standards for the public reporting of exploration results, mineral resources, and reserves, from the first initiatives to the current days. Particularities, similarities, and components, which ensure that the information provided complies to various worldwide instruments, are discussed. We also examined the recent changes in the national/regional Codes and guides, including the CRIRSCO Template published in late 2019. The systematization promotes understanding of company risks from the capital market and other financing mechanisms, making it possible to compare projects and do benchmarking analysis, allowing mining companies to comply in a more efficient, transparent, and less costly way to the jurisdictions under which they operate. Finally, presented is a chronology and evolution of the standardization and the localization of similar topics within the Codes of the CRIRSCO Family. The international reporting standards are a relevant and consistent instrument with reliable statements, clear language, and are recognized from one jurisdiction to another by financial institutions, which helps to improve and increase confidence in the mining industry. The objective of the CRIRSCO members is to provide and promote the understanding of the practices for mining investment decisions, being successful around the world.