Resumo em Inglês:

Abstract This article explores the application of ground penetrating radar (GPR) as a novel, cost-effective tool for rock mass classification in geotechnical engineering. Traditional rock mass classification systems, such as the rock quality index (RQD), the rock mass rating (RMR), the q-system (Q), and the geological strength index (GSI), primarily rely on geological mapping and drilling investigations, which, while effective, have limitations including high costs, invasiveness, and one-dimensional subsurface information. GPR offers a non-destructive alternative, providing high-resolution, two-dimensional subsurface imaging. This study demonstrates the efficacy of ground-penetrating radar (GPR) in identifying subsurface discontinuities, comparing its findings with UAV imagery. We also outline the potential for GPR-based insights to complement geomechanical classifications (RQD, RMR, Q, and GSI), highlighting how GPR can enhance the interpretation of rock mass characterization. Utilizing data from a GPR survey conducted on a jointed rock mass slope outcrop at the downstream side of the Castanhão Dam spillway in the state of Ceará, Brazil, the research highlights GPR's potential in accurately characterizing rock mass discontinuity conditions. Incorporating GPR as a complementary tool alongside traditional methodologies for jointed rock mass characterization, this research demonstrates the method's potential in refining and augmenting the identification of discontinuities. Such a synergistic approach could significantly enhance the accuracy of rock mass classification, potentially contributing to improved safety and efficiency in rock engineering practices.

Resumo em Inglês:

Abstract This article aims to evaluate the performance of a prototype variable load permeameter developed with hydrosanitary pieces in order to measure the permeability coefficient of pervious asphalt, which is a mixture composed of mineral aggregates and pure or modified asphalt binders, having an air void content close to 20%. This material must have permeability and porosity characteristics that influence the hydrological behavior of the surface. Faced with the need to quantify the degree of permeability of specimens used in studies of pervious asphalt and the absence of a regulatory standard for this test, a permeameter was created from hydrosanitary pieces. It was observed that the operation was easy, the system had an excellent degree of tightness and that the results were coherent and aligned with literature. To enable the development of the mentioned permeameter, a laboratory study was carried out on a mixture of pervious asphalt with a binder modified by polymers and an air void content of 18.3%, in which the influence of the addition of four different levels of cellulose fiber was evaluated (0%, 0.25%, 0.50% and 0.75%). It was observed at the end of the study that the material with the addition of 0.50% fiber presented the best results in terms of permeability. It should be noted that the developed permeameter proved to be an efficient, simple and precise testing tool, consisting of the creation of a set capable of laterally surrounding a traditional test specimen and allowing water to pass only in a vertical direction.

Resumo em Inglês:

Abstract The use of the Limit State Design method in the design of offshore structures is not common among engineers (Qing Yu et al., 2016), who mostly rely on the Working Stress Design (WSD) method for this type of structure. The fundamental difference between Load and Resistance Factor Design (LRFD) and the WSD method is, then, that the WSD employs one factor while the LRFD uses one factor with the resistance and one factor each for the different load effect types (Galambos, 1978). The objective of this article is to quantify the weight savings achieved by using the LRFD methodology instead of the WSD methodology, as well as to present the load and resistance factors for such structures. For the development of this study, six modules installed on the topside of an FPSO (Floating Production Storage and Offloading), located off the Brazilian coast, are evaluated. Both in-service and installation analyses are conducted for each of the six structures. The in-service analysis considered operational conditions with an annual return period, extreme conditions with a 100-year return period, and accidental conditions. The results show a weight reduction of up to 11.50% in the topside modules.

Resumo em Inglês:

Abstract With the increase in greenhouse gas emissions from the construction sector, pursuing more sustainable solutions has become essential. The use of composite steel-concrete slabs can considerably reduce environmental impacts due to their rapid construction and the elimination of the need for shoring. This study aims to present the optimization problem formulation for composite steel-concrete slabs, considering continuity between slabs and the addition of positive and negative reinforcement. The design constraints adhered to the provisions of Brazilian standards for composite steel and concrete structures, while Particle Swarm Optimization and Grey Wolf Optimization algorithms were employed to solve the optimization problem. A comparative analysis was conducted with solutions provided by a formwork manufacturer to assess the effectiveness of the proposed solutions and the gains achieved through the application of the formulation. The optimization algorithms yielded similar optimal solutions in most analyses, with a slight advantage for Grey Wolf Optimization in cases where distinct solutions were obtained. The manufacturer's solutions exhibited a total CO2 emission up to 54% higher than the optimal solutions. The constraints governing the optimization problem were the formation of a plastic hinge due to a negative bending moment and failure due to longitudinal shear.

Resumo em Inglês:

Abstract Exposure to particulate matter in the indoor air in industries poses significant health risks to exposed workers. However, adequate toxicological assessments of these materials remain lacking in specific industries, including the ceramics industry. The in vitro toxicological impact of particulate matter dispersed in three different indoor environments in the ceramic industry was investigated in this study. Relationships between dust concentrations in the work environment, size distribution, and morphology of the airborne particles were considered for exposure characterization. Further, acute toxicity and cytotoxicity were determined using Daphnia magna and an MTT assay with liver cells, respectively, to measure cellular metabolic activity as an indicator of cell viability. The results confirmed that the working environments of the selected ceramic industries had dust concentrations in the respirable fraction with considerable amounts of free crystalline silica (maximum detected concentrations of 0.980 + 0.425 mg/m3) relative to the calculated tolerance limit of 1.171 mg/m3. This value was almost 20 times higher than that determined by the American Conference of Governmental Industrial Hygienists, while the Brazilian standard established the limit of up to 4 mg/m3 for dust in the respirable fraction based on the quartz content of the sample. The in vitro and in vivo tests demonstrated that all collected samples were toxic at the organism and cell levels, thereby, confirming the greater toxicity and cytotoxicity of dust from environments with higher free crystalline silica content, and reducing it to an actionable level to increase cell viability by 77%.ce and extending the applicability of X22 steel in high-temperature environments.

Resumo em Inglês:

Abstract X22 martensitic steel is widely used for its mechanical properties, but its high-temperature oxidation resistance is limited. This work investigates Halide Activated Pack Cementation (HAPC) as a surface treatment to improve this property. The process was performed using pure aluminum as the masteralloy, activated by NH4Cl, NaCl and KCl, with treatments at 650 °C and 800 °C for 16 h. Thermodynamic simulations supported the evaluation of aluminum deposition. At 650 °C, the salts failed to form suitable coatings. At 800 °C, aluminized layers of 75 µm (KCl) and 80 µm (NaCl) were obtained, with Fe-Al compositional gradients. Oxidation tests showed a significant improvement: mass gain was reduced from 13.55 mg/cm2 (uncoated) to 0.88 mg/cm2 for the KCl-activated coating and 0.90 mg/cm2 for the NaCl-activated coating. These results confirm the effectiveness of HAPC in enhancing oxidation resistance and extending the applicability of X22 steel in high-temperature environments.

Resumo em Inglês:

Abstract The longitudinal grade and rolling resistance of mining haul roads are critical factors that significantly influence transportation costs and productivity in open-pit mining. Inadequate geometric design and high rolling resistance can lead to increased energy consumption, higher rates of mechanical failure, and greater maintenance requirements, ultimately shortening the lifespan of trucks and tires and negatively affecting overall operational efficiency. The geometric layout of mining roads is influenced by factors such as the mining method, orebody geometry, and topography, and is often determined through empirical knowledge or arbitrary decision-making, rather than an adequate methodology. This article proposes a practical methodology to assess how the combination of different longitudinal grades and rolling resistances affect haul truck efficiency in terms of fuel consumption and productivity. The methodology is straightforward and suitable even for small mines. It consists of four stages: (1) data collection using unmanned aerial vehicles (UAVs); (2) processing of aerial imagery to create a digital elevation model; (3) assessing of road design under different rolling resistance scenarios; and (4) evaluating fuel consumption and truck productivity. A case study in a Brazilian iron ore mine was proposed, and the results indicate that optimizing longitudinal grades and managing rolling resistance can reduce truck cycle time by up to 15%, save up to 13% on fuel consumption, and improve per-truck productivity by up to 17%, thus enabling a smaller truck fleet without compromising overall output.

Resumo em Inglês:

Abstract This study aimed to characterize kaolin residues originating from the pegmatitic region of northeastern Brazil, an area that annually produces and disposes of thousands of tons of kaolin residue into the environment without any control. The research focused on the industrial potential of these residues through chemical composition analysis by X-ray fluorescence (XRF), mineralogical characterization by X-ray diffraction (XRD), and morphological characterization by scanning electron microscopy (SEM) across different granulometric fractions. The results, supported by the literature, revealed that both siri and sarrabulho residues exhibited chemical, mineralogical, and textural compositions dominated by silica (SiO2) and aluminum oxide (Al2O3), which varied according to particle size. The fine fractions (< 74 µm) showed higher Al2O3 contents (42%), corresponding to kaolinite and muscovite minerals, which confer favorable properties to produce ceramic coatings, cement, and paints. Conversely, the coarse fractions (> 150 µm) contained 83% SiO2, attributed to quartz mineral, contributes to improved mechanical strength and thermal stability in aggregates for the construction industry. Additionally, 8.10% potassium oxide (K2O) and 3.22% phosphorus pentoxide (P2O5) were identified, suggesting potential agricultural applications as soil conditioners. Based on the results, it is concluded that the Siri and Sarrabulho residues, according to literature, exhibit physicochemical and mineralogical characteristics that support their reuse in various industrial sectors, particularly in ceramics, civil construction, and agriculture. The valorization of these residues represents a strategic approach to mitigating environmental impacts and promotes the integration of these materials into production chains aligned with the principles of economic, environmental, and social sustainability.

Resumo em Inglês:

Abstract In a steel mill, reduction occurs through the interaction of reductant gases with iron ore. Gas access to oxides is crucial, making bed permeability important for the reduction process. The size distribution and shape of feed material and voids between particles are vital to ensure such a permeability. As ore reserves deplete, finer comminution and concentration processes are demanded, increasing the need for agglomeration. Pelletization, producing spherical agglomerates, ensures bed permeability. Roller screens guarantee pellet size distribution, but have limitations and require costly maintenance. This article explores sensor-based sorting equipment as an alternative to roller screens for green pellet screening. Although the target application is green pellets, the laboratory-scale tests were conducted using sintered pellets to simulate the process under controlled and practical lab conditions..

Resumo em Inglês:

Abstract The combination of acidizing and hydraulic fracturing, or proppant-acid fracturing, seems to be a very logical approach to achieve the maximum stimulated volume in tight gas reservoirs, since the acid solution can stimulate the deep microfracture network far beyond the main propped fracture. However, this hybrid stimulation method sparks concerns that acidizing can increase proppant embedment and decrease the propped fracture conductivity. To understand how acidizing may be responsible for reducing conductivity, this article initially delves into the analysis of microscopic images of carbonate and siltstone specimens associated with a low permeability or tight gas reservoir in the São Francisco basin, in Minas Gerais, a kind of reservoir which is becoming considerably more important in recent years due to energy transition initiatives. The microscopic analysis revealed that thin, well-defined layers emerged on the acidized surface of some of the studied specimens. Then additional nanoindentation and proppant embedment tests showed that these new layers are weaker compared to the original rock matrix and are ultimately responsible for fracture conductivity decline. The findings in this study serve as an important piece of information for reservoir stimulation professionals that may consider the combination of acid stimulation and hydraulic fracturing in tight gas formations.