DEAMB - Departamento de Engenharia Ambiental
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/480
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Resultados da Pesquisa
Item Weathering resistance of Linz–Donawitz (LD) slag as ballast material using freeze-thaw and sulfate soundness.(2023) Alves, Hebert da Consolação; Gomes, Guilherme José CunhaAs nonrenewable natural aggregates with acceptable geotechnical properties become scarce, costly, and entail negative environmental impacts, the study of alternatives remains a first-order challenge for sustainable railway design. This paper focuses on the physical and chemical weathering effects of the industrial byproduct Linz–Donawitz (LD) slag as a ballast material. For this purpose, 75 freeze–thaw (F-T) and 40 sulfate soundness (SS) cycles were carried out on the byproduct. We present a series of laboratory experiments involving particle characteristics, durability and strength for different F-T and SS cycles. To benchmark the performance of LD slag, we also performed our experiments on two natural aggregates: gneiss and basalt. Our main findings reveal that: (i) the shape of LD slag ballast and its particle size distribution are unnafected by the F-T and SS cycles, (ii) the basalt exhibits higher magnitudes of fouling after SS cycles, (iii) losses in Los Angeles abrasion and shock resistance were much more pronounced in SS tests for all ballast materials, (iv) LD slag is more resistant and less susceptible to the degrading effects of freezing and thawing, (v) point load tests indicate that the loss of resistance of basalt is small compared to that of gneiss, (vi) the byproduct showed a decrease in strength of 87% after 40 SS cycles, suggesting that chemical weathering exerts a dominant control on the performance of LD slag. The findings are relevant to elucidate the physical and chemical weathering effects of LD slag and to promote its sustainable use.Item Blending Linz–Donawitz and Blast Furnace slags with the Kambara reactor byproduct to improve their reuse in roadworks.(2022) Schumacher, Aécio Guilherme; Gomes, Guilherme José Cunha; Schneider, Denise S. G.; Pires, Patrício José Moreira; Gomes, Ruan Gonçalves de SouzaThe use of industrial byproducts as replacement of natural aggregates has been extensively investigated to design eco-friendly roads. One of the most examined byproducts for this purpose is steel slag. However, existing studies do not explore the blending of different slags to enhance the engineering performance of base layers. The applicability of Linz–Donawitz (LD), Blast Furnace (BF) and Kambara Reactor (KR) steel byproducts is evaluated as a single base layer for rural (unsurfaced) roads in Brazil. A series of laboratory experiments were performed to assess the characteristics of eight soil-byproduct mixtures with 50% and 75% byproduct contents, including new blends of LD/KR and BF/KR slags. Additionally, the most suitable mixture was proposed considering different performance indicators. Results demonstrate the coarse-grained, nonplastic and non-expansive nature of the byproducts, with CBR values higher than 100%. The more byproduct added to soil, the larger is the strength and the lower the expansion. The mixture with 75% of the proposed LD/KR blend and 25% of a clayey soil was considered as optimum, based on a trade-off between engineering properties, environmental impacts, and material costs. Findings and discussions are relevant to reduce waste stockpiles of steel companies, helping engineers and policy makers reuse blended slag byproducts.Item A hybrid multi-step sensitivity-driven evolutionary polynomial regression enables robust model structure selection.(2022) Gomes, Ruan Gonçalves de Souza; Gomes, Guilherme José Cunha; Vrugt, Jasper A.Evolutionary Polynomial Regression (EPR) has found widespread application and use for model structure development in engineering and science. This hybrid evolutionary approach merges real world data and explanatory variables to generate well-structured models in the form of polynomial equations. The simple and transparent models produced by this technique enable us to explore, via sensitivity analysis, the robustness of the derived models. Yet, existing EPR frameworks do not make explicit use of sensitivity analysis in the selection of robust and high-fidelity model structures. In this paper, we develop a multi-step sensitivity-driven method which combines the strengths of differential evolution and model selection via Monte Carlo simulation to explore the input–output relationships of model structures. In the first step, our hybrid approach automatically determines the optimum number of terms of the polynomial equations. In a subsequent step, our algorithm explores the mean parametric response of each explanatory variable used in the mathematical formulation to select a final model structure. Finally, in our selection of the most robust mathematical structure, we take explicit consideration of the prediction uncertainty of the simulated output. We illustrate and evaluate our EPR method for different engineering problems involving modeling and prediction of the moisture content and creep index of soils. Altogether, our results demonstrate that the use of sensitivity analysis as an integral part of model structure search and selection will lead to robust models with high predictive ability.Item Ferronickel slag as free‐draining rockfll dike material : a novel waste solution for mining regions.(2022) Costa, João Paulo Rodrigues da; Gomes, Guilherme José Cunha; Fernandes, Gilberto; Magarinos, Dario Mozzer; Fonseca, Alberto de Freitas Castro; Pires, Patrício José MoreiraMining sites are vulnerable to erosion and siltation of rivers. While the construction of rockfill dikes can mitigate siltation, existing rockfill dikes are typically constructed with natural aggregates, whose mining, beneficiation, and transportation entail additional adverse impacts. In this paper, ferronickel slag (FNS) was investigated as a free-draining rockfill dike material to be used in nearby mining sites. A series of laboratory tests, including physical, environmental, durability, chemical and mineralogical analyzes, was executed to evaluate the engineering characteristics of this byproduct and its potential use in dikes. Results demonstrate that FNS is non-uniform with relatively low Los Angeles abrasion. Leaching and dissolution tests have not shown harm to the environment since the average concentrations of chemical elements existing in FNS were below the standard requirements. Accelerated weathering cycling tests with ethylene glycol further highlighted that the byproduct does not suffer premature disaggregation in the presence of water, thereby revealing that the material can be employed adequately under saturated condition. Findings suggest that the use of FNS in rockfill dikes represents a technically and environmentally feasible solution, while reducing the use of natural aggregates, avoiding the formation of stockpiles, preventing siltation in downstream fluvial networks and other adverse impacts.Item Field-scale assessment of the unsaturated hydraulic properties of residual soils in southeastern Brazil.(2022) Gomes, Ruan Gonçalves de Souza; Gomes, Guilherme José Cunha; Vargas Júnior, Eurípedes do Amaral; Genuchten, Martinus Theodorus van; Pinto, João T. M. G.; Rosa, Felipe A.Field tests were carried out to estimate effective unsaturated soil hydraulic properties of layered residual soilsin Rio de Janeiro, southeastern Brazil. Data of this type are important for understanding the initiation of rainstorm-induced soil landslides, which often occur in the state of Rio de Janeiro as well as other areas having similar geologicsettings and climate conditions. Tests were carried out using a simplified field approach, referred to as the MonitoredInfiltration Test, which requires only a tensiometer to measure pressure heads below the wetting front, triggered by flowfrom a Mariotte bottle which maintains a constant pressure at the top edge of the soil profile. The data can then beanalyzed by numerical inversion using the HYDRUS-2D software package. The test is relatively fast since no steady-state flow conditions are needed, and versatile since the test can be carried out quickly on steep slopes with the help of amanual auger. Soil water retention and the unsaturated hydraulic conductivity functions were obtained for a range ofyoung, mature and saprolitic residual soils. The effective hydraulic properties of the distinct residual soil layers can bequite large, reflecting a need to provide a careful analysis of field-scale hydraulic heterogeneity in geotechnical analyses.Item A dual search‐based EPR with self‐adaptive ofspring creation and compromise programming model selection.(2021) Gomes, Guilherme José Cunha; Gomes, Ruan Gonçalves de Souza; Vargas Júnior, Eurípedes do AmaralEvolutionary polynomial regression (EPR) is extensively used in engineering for soil properties modeling. This grey-box technique uses evolutionary computing to produce simple, transparent and well-structured models in the form of polynomial equations that best explain the observed data. A key task is then to determine mathematical structures for modeling physical phenomena and to select the optimal EPR model. This requires an algorithm to search through the model structure space and successfully produce feasible solutions that honor a set of statistical metrics. The complexity of EPR models increases greatly, however, with the number of polynomial terms used to tune these models. In this paper, we propose an alternative EPR for modeling complex soil properties. We implement a dual search-based EPR with self-adaptive ofspring creation as model structure search strategy and couple a compromise programming tool to select a model that is preferred statistically relative to models with diferent polynomial terms. We illustrate our method using real-world data to improve predictions of optimal moisture content and creep index for soils. Our results demonstrate that the models derived using the proposed methodology can predict soil properties with adequate accuracy, physical meaning and lower number of parameters and input variables.Item Bayesian inference of rock strength anisotropy : uncertainty analysis of the Hoek–Brown failure criterion.(2021) Gomes, Guilherme José Cunha; Gaona, John Harry Forero; Vargas Júnior, Eurípedes do Amaral; Vrugt, Jasper A.Strength properties of most sedimentary and metamorphic rocks are known to vary with direction. Knowledge of this so-called rock anisotropy is of utmost importance for reliability analysis and engineering design. The purpose of this paper is twofold. First, we propose a formulation of the Hoek–Brown (HB) failure criterion, which calculates strength anisotropy using a non-uniform scaling of the stress tensor. We use two scaling factors, CN and CS , to link the orientation of the anisotropy planes with the loading direction. As we assume isotropic parameters for intact rock, our HB model formulation is relatively easy to use and has the additional advantage that it does not demand any modifications to the HB failure criterion. Second, we embed our HB model formulation in a Bayesian framework and illustrate its power and usefulness using experimental data of anisotropic rock samples published in the literature. Results demonstrate that our HB model formulation predicts accurately measured peak strengths of rocks with different degrees of anisotropy, confining stresses and anisotropy orientations. The uncertainty in peak strength of anisotropic rocks can be quite large, reiterating the need for an explicit treatment of strength anisotropy uncertainty in rock mechanics studies. The Bayesian methodology is general-purpose, and, as such, can help better inform geotechnical engineers, contractors and other professionals about rock conditions and design reliability and assist decision makers in determining the overall risks of engineering structures.Item A cross-anisotropic elastoplastic model applied to sedimentary rocks.(2020) Gaona, John Harry Forero; Gomes, Guilherme José Cunha; Vargas Júnior, Eurípedes do Amaral; Falcão, Flávia de Oliveira Lima; Velloso, Raquel QuadrosStrength and deformability properties of sedimentary rocks are difficult to characterize as these geomaterials show anisotropic mechanical behavior, which cannot be adequately evaluated by an isotropic constitutive model. This essay proposes a cross-anisotropic elastoplastic model to evaluate stress–strain relationships of sedimentary rocks. The approach couples the twelve-parameter Lade–Kim isotropic model with a non-uniform scaling of the stress tensor and includes two scaling parameters that link the orientation of the bedding planes with the loading direction. The anisotropic model parameters can be conveniently determined using Bayesian analysis. We illustrate our method using triaxial tests on a variety of confining stresses and bedding plane orientations for a travertine and a Tournemire shale. Our results demonstrate that the predicted maximum deviatoric stresses and the simulated stress–strain curves are shown to be in good agreement with the measured data.Item Toward improved performance of unpaved roads : laboratory tests and field investigation of a soil-byproduct base layer.(2020) Magalhães, Adair José de; Gomes, Guilherme José Cunha; Pires, Patrício José MoreiraIn this study, the performance of two steel slag byproducts is investigated to produce mixtures for base layers of unpaved roads. The basic physical properties including Atterberg limits, grain size distribution, California bear- ing ratio and expansion tests of eight different mixtures of soil-byproduct are investigated in laboratory to understand the engineering properties of the mixtures. The byproducts are mixed in different proportions from 50% to 80% by weight with a local (clayey) subgrade soil. Subsequently, two selected mixtures are used to build an experimental road section along an unsurfaced road. Results demonstrate that the gradation and strength of the samples satisfy the requirements for base layers. Furthermore, the mix- tures are shown to be of low-plasticity at higher byproduct content and non-expansive. Field investigations show that 12 roller passes at the stan- dard Proctor and 14 at the intermediate Proctor are enough to reach 100% of the degree of compaction.Item A sustainability-oriented framework for the application of industrial byproducts to the base layers of low-volume roads.(2021) Gomes, Guilherme José Cunha; Magalhães, Adair José de; Rocha, Fabiano Lucindo Lima da; Fonseca, Alberto de Freitas CastroRoadway engineering works typically rely on the utilization of natural aggregates as building materials. However, growing pressures for sustainable roads are highlighting the importance of replacing virgin materials with industrial byproducts. Constructors worldwide are trying to select optimum soilbyproduct mixtures that have a fair trade-off between engineering properties, environmental impacts and material costs. This requires a multi-objective analysis to explore feasible mixtures that honor a set of preferences to mathematically identify the best compromised soil-byproduct mixture. In this paper, a sustainability-oriented framework is proposed for selecting optimum soil-byproduct proportions for unbound base layers of unpaved roads. A compromise programming tool is implemented to select a mixture that is statistically preferred over mixtures with different byproduct contents. The method is illustrated using technical, economic and environmental indicators that are easily measurable. Investigations are performed for different decision-making perspectives including the constructor’s, contractor’s and the environment’s viewpoints. Two byproducts from the steel industry are mixed in different proportions from 50% to 80% by weight with a clayey soil. The optimum mixture was obtained at a proportion of 70% byproduct and 30% clay. Monte Carlo simulations and sensitivity analysis of transport scenarios further supported this conclusion. Results demonstrate that mixture selection based only on strength properties provides inadequate optimum from a sustainable standpoint. The proposed framework can help road constructors incorporate environmentally-friendly materials in a cost-effective way, while maintaining the technical quality of base layers.