DEMIN - Artigos publicados em periódicos

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The importance of the economic exploitation plan in the decision making process in mining.
(2022) Almeida, Wendel Eduardo de; Curi, Adilson; Arroyo Ortiz, Carlos Enrique
In general, investors evaluate several investment alternatives including, obviously, the possibility of money investment in the banking system. The mineral resource industry is just one of the several options of investment available in the financial market. To select this option, especially for the mining investments, investors require ever more projects with proven financial security and developed by renowned companies. The financial return or potential of the project must be significant to justify the risks inherent to the mining activities. To facilitate the financial analyses of mine projects, in this study is proposed a methodology based on an economic analysis of the Brazilian gold Berimbau mine through an Economic Exploitation Plan - EEP- where a sensitivity analysis of the project cash flow was performed and variations in the ore price, investments (CAPEX - capital expenditure) and operating costs (OPEX - operating expense) were applied. An orthodox scenario with an ore price (gold) of USD 900.00/oz was considered. The results, specific aspects and socioeconomic benefits have confirmed the project’s feasibility.
Remediation alternatives for an abandoned gold mine contaminated with mercury in Brazil.
(2022) Miranda, José Fernando; Lima, Hernani Mota de; Curi, Adilson; Luz, José Aurélio Medeiros da; Destro, Elton
Heavy metal contamination of soils has generated two major problems, namely, loss of land value and health risk for people near contaminated sites. Studies on soil remediation are typically conducted on a pilot scale under very controlled conditions. This is a misleading approach, once the complexity of the actual biogeochemical soil conditions may causes inefficiency in full scale real-world application. In addition, environmental impacts of remediation practices themselves are often ignored, which may make them unfeasible. In 2002, an occurrence of mercury in an abandoned old gold mine was detected in a rural area of Descoberto, Brazil. In 2014, the State Public Prosecutor required from the responsible State Environment Agency, a remediation project to the area. This study compares alternatives for remediation of the contaminated area. Also a historical approach on mercury amalgamation in gold mining in the region, in order to estimate the amount of mercury remaining in the site. The geochemical characterization of the contaminated area was performed to describe the contamination process. The results were compared with the remediation proposal advocated by the Brazilian Ministry Public, and some alternatives for decontamination of the area were studied. The electrokinetic method has displayed the lowest overall unit cost, between US$ 120.00/t and US$ 260.00/t. The residual Hg concentration after four cycles of the electrokinetic technique was estimated at 1.28 mg (Hg)/kg (soil), slightly higher than the intervention value for agricultural soil, which is 1.20 mg (Hg)/kg (soil).
Mine waste sequencing on an iron ore project.
(2022) Curi, Adilson; Arroyo Ortiz, Carlos Enrique; Casimiro Huayhua, Jorhs Enrique
Los recursos minerales disponibles en nuestro planeta son finitos, aunque su potencial no sea conocido en su totalidad. El diseño de un proyecto minero, desde las actividades de exploración para conocer el depósito mineral, explotarlo y el cierre de una mina, puede influir la vida útil de la mina. El objetivo de este estudio es evaluar la forma de disposición selectiva de los residuos de una mina de hierro y su posible reutilización en el futuro, destacando su uso y posibles repercusiones en la extensión de su vida útil de una mina de hierro localizada en el Quadrilatero Ferrifero. Recursos y reservas han sido evaluados, así como las fases finales e intermediarias, la secuencia de minado y disposición de residuos. La metodología ha sido empleada en un depósito de hierro brasilero en operación. En donde se pretende demostrar la importancia de evaluar los materiales residuales a fin de prolongar la vida útil del yacimiento mineral.
Variáveis de impacto no sequenciamento de lavra.
(2022) Campos, Bárbara Isabela da Silva; Souza, Felipe Ribeiro; Lima, Hernani Mota de
O planejamento de mina é desenvolvido considerando variáveis econômicas, teores, litologia, posição espacial. Estas variáveis são utilizadas para determinar o limite final de cava e sequenciamento das operações. Normalmente são amostradas exaustivamente somente as variáveis relacionadas ao teor. As demais variáveis são configuradas com valores médios. As técnicas de estatística multivariada permitem determinar as variáveis de maior impacto. Utilizando um modelo geológico de cobre e ouro será determinado a cava final e sequenciamento de lavra utilizando o algoritmo de Lerchs-Grossmann. O modelo de blocos resultante será avaliado quanto as variáveis fora do padrão da população. Foram padronizados e transformados em variáveis contínuas adequadamente os elementos da população. Será utilizado a técnica de análise de componentes principais para determinar as variáveis mais importantes do sequenciamento de lavra e cava final. O objetivo deste trabalho é determinar as variáveis mais influentes na determinação de cava final e sequenciamento de lavra. As ferramentas de planejamento de mina apenas apresentam o resultado final do planejamento. Não apontam as variáveis mais sensíveis. É importante determinar as variáveis em que uma pequena variação no valor é capaz de transformar um bloco minerado em estéril. O trabalho confirmou a importância das variáveis econômica relacionadas a função benefício, entretanto quantificou que o posicionamento espacial do bloco possui importância semelhante a algumas variáveis econômicas.
Otimização da unidade mínima de lavra para o planejamento de curto prazo.
(2023) Oliveira, Mariana Paula Rossini de; Souza, Felipe Ribeiro; Silva, José Margarida da
Na mineração a céu aberto, no horizonte de curto prazo, é realizado a subdivisão dos planos de lavra em trimestral, mensal, semanal e diário da operação. Em um horizonte mensal, um planejador de curto prazo define as poligonais, que compreende os sucessivos avanços de lavra, satisfazendo parâmetros de qualidade e tonelagem de minério fixadas previamente pela usina. As poligonais, tradicionalmente, são projetadas sem uma devida abordagem sistemática. Logo, as interações realizadas para obter as especificações exigidas pela usina é limitada. Portanto, há uma demanda por estudos envolvendo técnicas de otimização de unidades mínimas de lavra, auxiliando o delineamento do minério, de modo a minimizar a variabilidade em teor e maximizar a recuperação da usina, além de fornecer base quanto a tomada de decisão diária pelo planejador de curto prazo. Esse artigo propõe a adaptação de dois algoritmos de otimização – Cone Flutuante e Stope Flutuante, tradicionalmente utilizados para a definição de cavas e realces subterrâneos. Foi atribuído um valor de dimensão igual a zero para os pilares de sustentação, aproximando o método de câmaras e pilares a um método de bancadas, para configurar um comportamento próximo a lavra em céu aberto. O estudo comprovou que ambas as metodologias apresentaram resultados satisfatórios. Apesar da necessidade de ajustes manuais, descartando blocos compartilhados, o Cone Flutuante mostrou ser um sistema mais seletivo, principalmente para teores de corte mais elevado.
Separação magnética de ustulado de minério de ferro hematítico.
(2022) Neuppmann, Pedro Henrique; Luz, José Aurélio Medeiros da
A ustulação objetivou o aumento da eficiência da separação magnética de um minério de ferro hematitico. O percentual de coque, o tempo de ustulação e a temperatura foram analisados em vários níveis baseados na literatura prévia. A caracterização da amostra foi feita para avaliar a densidade da amostra e o tamanho tanto da partícula de minério como de coque. A análise termogravimétrica indicou transformação de hematita para magnetita por picos característicos de perda de massa. A transformação hematita-magnetita fornece forte contraste na suscetibilidade magnética entre minerais portadores de ferro e ganga, esta composta basicamente por quartzo. Os resultados demonstraram o incremento no magnetismo e fotografias comprovaram o caráter magnético da amostra ustulada. A melhor condição obtida foi com 35 minutos, 10 % de coque (em massa) e 1,023 K (750 oC). A eficiência foi aumentada em 5.3 % sob campo de 0.93 T e 240.3 % sob campo de 0.06 T, aumentando a seletividade da separação magnética até sob baixo gradiente magnético. Esta rota poderia ser aplicada com sucesso aos rejeitos de minério de ferro em campo de baixo gradiente, naturalmente após análise econômica cuidadosa, na qual a quantificação de passivos ambientais (principalmente resultante de sua não implementação) é incluída.
Experimento sencillo para el modelamiento de la interfase de reacción en la descomposición de sólidos.
(2023) Silveira, Marcus Alexandre de Carvalho Winitskoski da; Luz, José Aurélio Medeiros da; Guerrero Vargas, Jorge Carlos
En concordancia con el concepto de interdisciplinaridad, el presente trabajo propone un experimento sencillo para la enseñanza de reacciones de descomposición de sólidos, mediante la simulación de la evolución geométrica de paralelepípedos de naftaleno sometidos a sublimación. El modelamiento geométrico de las proyecciones de las caras del objeto de ensayo mediante las curvas de Lamé (también denominadas superelipses) permite calcular el volumen del superelipsoide correspondiente, proporcionando una cuantificación adecuada en la variación de la masa muestral del naftaleno. El procedimiento experimental planteado evidencio ser una herramienta fácil y esclarecedora para realizar clases prácticas en laboratorios mínimamente equipados, con el objetivo de aprender tanto reacciones de descomposición de sólidos, como también de técnicas de modelamiento matemático de interfases en reacciones heterogéneas, aplicando curvas de Lamé.
Predição de vibrações induzidas por desmontes de rochas por explosivos usando redes neurais artificiais.
(2022) Zorzal, Caroline Belisário; Santos, Francisco Lledo dos; Silva, José Margarida da; Souza, Rafael de Freitas
Na indústria mineral, o parâmetro mais utilizado para a quantificação e avaliação do potencial de danos das vibrações sísmicas geradas por desmonte de rochas é a velocidade de vibração de pico de partícula (VPP). Várias iniciativas foram tomadas, ao longo do tempo, com o intuito de estimar os níveis de VPP. Os rápidos avanços na tecnologia computacional fizeram com que sistemas inteligentes se tornassem ferramentas promissoras na estimativa dos resultados de desmonte de rochas. Nesse contexto, este estudo tem como objetivo avaliar as vibrações induzidas por desmontes de rochas por explosivos em uma mina do Quadrilátero Ferrífero por meio de redes neurais artificiais. O banco de dados foi dividido em amostras de treinamento (70%) e teste (30%) das redes. Considerando a importância da seleção de variáveis de entrada adequadas para o treinamento das redes, diferentes grupos de variáveis input foram analisados. A arquitetura que demonstrou melhor desempenho considerou a distância entre o ponto de monitoramento e detonação e a carga máxima por espera como variáveis input. A fim de comparar o desempenho da rede neural com o desempenho de modelos empíricos e de regressão múltipla, os mesmos dados foram utilizados. Por fim, o modelo de redes neurais se mostrou superior às equações empíricas e à regressão múltipla em termos do coeficiente de determinação (R²) e da raiz do erro quadrático médio (RMSE) para os dados medidos e preditos. Além disso, demonstrou-se a importância da seleção das variáveis de entrada adequadas para a estimação de VPP por meio de redes neurais.
Effect of dynamic stress produced by rock blasting on the optimal dimensioning of room and pillars in horizontal layers.
(2022) Cano Nunez, Alcides Eloy; Arroyo Ortiz, Carlos Enrique; Silva, José Margarida da
An optimal dimensioning of the room and pillars of the square or rectangular section is nding adequate transversal section support for the pillar; in that sense, all forces acting on the pillar must be evaluated. e pillar has its ends subjected to normal (σ) and shear stresses (τ). In addition, the pillar can also be subjected to dynamic stresses from the seismic waves generated by rock blasting. us, when calculating the dimensions of a mine pillar, the stresses imposed by seismic waves must be considered. e combination of lithostatic and dynamic stresses generated by blasting can a ect the pillar, generating regions, or areas that will exhibit the formation of cracks, microcracks, chipping, and other detrimental processes for its stability. In that regard, it is appropriate to assess the dynamic e ects of the energy delivered in each wave pulse so that these dynamic quantities can be included in the dimensioning of the pillars. is paper presents the physical and mathematical formulation describing the dimensioning issues of room and pillars and its solution using numerical modeling. e numerical modeling is performed using nonlinear mathematical programming and simulation with FLAC 3D (Fast Lagrangian Analysis of Continua in 3D). In this study, it was proven that the stress generated by the seismic wave represents a dynamic stress of nearly 5.5 MPa. 'Dimensioned pillars considering wave stresses allows it to recover an average 1.6% less when it is compared with pillars only under overlying rock mass'.
Concentration of oxidized Brazilian zinc ore by flotation : comparative study between anionic and cationic routes.
(2022) Ferreira, Pedro Henrique Tófani; Lima, Rosa Malena Fernandes
In this work, a mineralogical characterization by X-ray diffractometry and thermogravimetric analysis of a new Brazilian zinc ore sample was performed. The mineralogical semi-quantification, conducted by normative calculation of the identified minerals, using their theoretical chemical formulas and the contents determined in the chemical analyses was as follows: smithsonite (20.3%), goethite (49.6%), kaolinite (12%), quartz (6.2%), cerussite (3.0%), chlorite (4.0%), dolomite (0.5%) and others (4.4%). Subsequently, bench flotation tests were executed, using sodium oleate (anionic route) and amine (cationic route) as smithsonite collectors. Sodium silicate was used as a depressant of the gangue minerals in both routes tested. These studies showed that the anionic route (30.1% Zn in concentrate and 83% Zn recovery) performed better than the cationic route (17.5% Zn in concentrate and 46.3% Zn recovery). Considering the mineralogical composition of the concentrates obtained in the best flotation results, associated with physicochemical studies published in the literature with the identified minerals, it was evidenced that the difference in performance between the tested routes is due to the influence of ions from the dissolution of carbonates present in the ore on the surface properties of the main gangue minerals (goethite and silicates), especially for the cationic route.
Relationship between particle size distribution and the PFD80 transportable moisture limit of iron ore fines.
(2022) Ferreira, Rodrigo Fina; Lima, Rosa Malena Fernandes
Since 2011, mineral cargoes shippers shall comply with a regulatory framework established by the United Nation’s International Maritime Organization (IMO): the International Maritime Solid Bulk Cargoes (IMSBC) Code. Some wet mineral cargoes, including some types of iron ore fines, may liquefy during ocean transport, i.e., the cargo can shift and lead the vessel to sink. According to the IMSBC Code, for safe shipping, the moisture content of these cargoes shall be lower than a regulatory limit: the Transportable Moisture Limit (TML). Iron ore fines TML can be obtained through the Modified Proctor/Fagerberg Test for Iron Ore Fines (PFD80), a dynamic compaction test which consists in compacting ore samples at different moisture contents, the TML being the moisture content at which the material reaches 80% saturation. TML has become a relevant parameter for the mining industry, firstly due to the crew and ship safety aspect, and because failure to comply with the TML can legally interrupt an ore shipment or even an entire mining/shipping operation. Therefore, knowledge related to the TML and the understanding of how it varies with ore characteristics are essential. Despite that, research works on this topic are still scarce. In this study, the relationship between particle size distribution and the TML of iron ore fines was experimentally investigated. The results have shown that the TML is highly related to the particle size distribution of the tested material, and that the TML variations can be explained by structural packing effects caused by particle interactions during compaction for different types of size distribution. It was also found that the coefficient of uniformity can be used for numerically representing the particle size distribution in order to establish relationships with the TML. Another relevant conclusion is that the TML of a mixture of different iron ore fines may not be the result of the weighted average of the individual components’ TML. This knowledge is of utmost importance for the industry, as blends of different ore products are common practice, and this finding is relevant for other cargoes that are susceptible to liquefaction.
Three‑dimensional stability analyses and sensitivity studies of the input parameters in a global failure of an open pit slope : a case study.
(2023) Oliveira, Davidson Paulo Azevedo; Lana, Milene Sabino
This work aims to study the parameters afecting a global slope failure in an open pit mine. The event was a complex failure, formed by an upper layer of a weathered rock, which behaved like a soil mass, above two faults, which intersect to form a wedge. This upper soil layer has pressured the wedge leading to its failure. It occurred in the northern sector of the pit in 2013, causing the interruption of mining activity for about 1 year. The geomechanical parameters were defned from an extensive feld survey database; lab tests and Schmidt hammer tests were performed in the region of the failure. The HoekBrown criterion was adopted for the rock mass; Barton-Bandis for the discontinuities and Mohr-Coulomb for the weathered rocks. Three-dimensional limit equilibrium methods were applied using the average strength parameters. The factor of safety (F.S.) was 1.33, a situation which indicated relative stability. Thus, sensitivity analyses were performed to defne the parameters that conditioned the failure, by progressively reducing the discontinuity shear strength via percentage factors, until F.S reached 1.0. Failure surface geometry obtained in the analysis was close to the failure observed at the feld. The susceptibility condition of the wedge failure was evaluated through kinematic analyses in two scenarios; F.S = 1.33 and F.S. = 1. The results indicated a signifcant increase in the probability of kinematic feasibility when F.S. was 1. The reduction of the slope dip should ensure a stable condition. Moreover, the water level should be kept far from the slope face.
Quality index of dimension stones for application in building industry using technological characterization lab tests.
(2022) Zagôto, Juliano Tessinari; Lana, Milene Sabino; Pereira, Tiago Martins
Dimension stones have been used in many different environments, like airports, shopping malls, commercial buildings and houses, due to their beauty and quality. However, the choice of the ideal material for application in a given environment is a challenging decision. Esthetic patterns determine the choice in most of the cases, instead of the physical and mechanical properties, which can cause damages and even accidents. Thus, this research aims to propose a quality index using technological characterization lab tests established by international and national regulations. This index can be used to help practitioners in the choice of the proper dimension stone for a given environment, minimizing pathologies. An extensive database encompassing many lab tests for technological characterization of dimension stones was used in this research.
Blast-induced ground vibrations : a dynamic analysis by FEM.
(2022) Zorzal, Caroline Belisário; Nogueira, Christianne de Lyra; Lima, Hernani Mota de
The peak particle velocities (PPV) are fundamental for understanding and managing the levels of blast-induced ground vibrations and their effects on adjacent structures. Given that numerical analysis of seismic vibrations has been demonstrated to be a method that can significantly contribute to predicting PPV, this study adopts a numerical approach using the finite element method (FEM) to assess blasting-induced ground vibration in rock masses. A dynamic module of the stress-strain analysis based on the FEM displacement formulation is developed in ANLOG software to estimate the variations of displacement, velocity, strain, and stress induced by blasting. The dynamic modulus implemented is verified using two verification examples. After, ANLOG is used in an application example to estimate seismic vibrations induced by blasting and to define the attenuation law for a limestone quarry near an urbanized area in Spain. The effect of Rayleigh damping coefficients (α and β) on the PPV levels estimated by ANLOG was investigated, and the most appropriate numerical attenuation law is then obtained. The numerical analysis presents satisfactory results for elastic-wave propagation induced by blasting and the peak particle velocity values obtained shows good agreement with field and the numerical results available in the specialized literature. The results indicate that ANLOG can perform personalized analysis of rock mass under blast-induced dynamic stress taking into consideration the geological and geomechanical characteristics particular to each medium as well as the blast parameters.
Aplicação da solução do problema de agrupamentos com restrições para determinação da condição de estabilidade de taludes de minas.
(2023) Oliveira, Rudinei Martins de; Santos, Tatiana Barreto dos; Silva Júnior, Ladir Antonio da
Este artigo apresenta uma aplicação do método Biased Random Key Genetic Algorithm (BRKGA) ao problema de agrupamentos com restrição. A solução deste problema retorna a separação de um conjunto de dados em agrupamentos, tal que os membros de cada agrupamento sejam similares entre si, respeitando as restrições dos dados. Os dados utilizados são de 88 taludes de minas localizados em diversos países do mundo. Através da solução do problema de agrupamentos com restrições, busca-se determinar a condição de estabilidade de taludes de minas por meio das suas características geomecânicas. Neste contexto, espera-se que o método possa ser utilizado e aplicado em empreendimentos mineiros de pequeno a grande porte.
Machine learning applied to the prediction of rockfall slope probability.
(2022) Silveira, Larissa Regina Costa; Lana, Milene Sabino; Santos, Tatiana Barreto dos
The objective of this work is to propose a predictive model of rockfall slope probability in rock slopes using the KNearest Neighbors (KNN) method. A dataset composed by 220 rock slopes was used, whose variables are related to the presence of water, characteristics of the rock mass, degree of overhang, among others. For each slope of the dataset, rockfall probability (high, medium, or low) is known and determined by cluster analysis. The number of the nearest neighbors (k) ranged from 1 to 20. The obtained average accuracy of the tested predictive models was equal to 78.4%. The models produced satisfactory results in the prediction of the rockfall probability, since the area under the ROC curve was equal to 0.80. The best model was selected based on the k value with the highest accuracy and the highest area under the ROC curve. The selected model had a k value equal to 7.
A new methodology for rockfall hazard assessment in rocky slopes.
(2022) Silveira, Larissa Regina Costa; Lana, Milene Sabino; Alameda Hernández, Pedro Manuel; Santos, Tatiana Barreto dos
This article presents an approach to rockfall hazard assessment for rocky slopes based on a previously published rockfall hazard methodology. The original method is appropriate to high alpine rocky slopes exposed to large scale deformations. It evaluates the parameters related to the geomechanical characterization of rock mass, indications of activity, external influences and event intensity. The original methodology was modified to consider different contexts, including geological, climatic and social environments. Parameters related to external influences were modified; the geometry and characteristics of the slope and the catchment area were introduced. The original methodology and the new proposal were applied to two urban slopes and one railway slope in order to test and compare the methods. The original proposal could not represent the rockfall conditions of these slopes. The new proposal was validated using two mine slopes, whose conditions of stability are known. The results of the analyses with the urban slope and the railway slope were coherent with the situation observed at the field. The validation in the mine slopes showed that this approach is applicable in several situations, being able to determine how hazardous a slope is in relation to rockfall events.
Development of a low-cost device for monitoring ventilation parameters (temperature, humidity and pressure) in underground environments to increase operational safety using IoT.
(2022) Santos, Rita de Cássia Pedrosa; Silva, José Margarida da; Albergaria Junior, Walter; Pinto, Cláudio Lúcio Lopes; Oliveira, Michel Melo; Mazzinghy, Douglas Batista
The important role of ventilation in underground mines is to ensure safety and adequate environmental conditions in all accessible areas of a mine. This research aims to develop lowcost solutions for monitoring ventilation parameters in underground mines using the Internet of Things (IoT). A comparison between standard measuring equipment and a new low-cost wearable monitoring device prototype was performed, and the variables measured in an underground mine were pressure, temperature, and relative humidity. The results in all surveys indicate that the wearable monitoring device prototype can properly be used for continuous monitoring of the underground environment. The standard measurement devices for underground mines should continuously be used by mining companies as requested by local legislation. The low-cost wearable monitoring device developed should be viewed as a redundant measurement device for operators’ safety. The constant innovations in technology can support mining operators in anticipating problems, improving productivity, ensuring safety, and meeting standards at low investments.
Failure risk of Brazilian tailings dams : a data mining approach.
(2021) Santos, Tatiana Barreto dos; Oliveira, Rudinei Martins de
This paper proposes the use of a hybrid method that combines Biased Random Key Genetic Algorithm (BRKGA) with a local search heuristic to separate Brazilian tailing dam data into groups. The goal was identifying dams similar to Fundão and B1 failed dams. The groups were created by solving the clustering problem by BRKGA. The clustering problem consists in separating a set of objects into groups such that members of each group are similar to each other. The data was composed by 427 dams, with the actual 425 dams of Brazilian Register of Tailing Dams and the two Brazilian failed dams from the last years. Computational experiments considering real data available are presented to demonstrate the effi cacy of the proposed method producing feasible solutions. Thus, it is expected that the good results can be applied in the identifi cation of tailings dams with risk potentials, assisting in the identifi cation of these dams.
Avaliação das barragens de rejeito brasileiras por meio da análise de agrupamentos k médias.
(2020) Paulo, Eliezer Antonio Amaral de; Pereira, Carla Maria Silva Felisberto; Santos, Tatiana Barreto dos; Oliveira, Rudinei Martins de
Com a evolução tecnológica, tornou-se possível a lavra de minérios cada vez mais pobres em teor. Dessa forma, a produção de rejeitos oriundos do tratamento de minérios aumentou, levando à necessidade de ampliação das barragens em número e capacidade para armazenamento desses resíduos. Como consequência, rupturas barragens de grandes dimensões passaram a acontecer com uma frequência alarmante, como por exemplo os episódios de Brumadinho/MG em 2019 e Mariana/MG em 2015. Este artigo tem por objetivo a aplicação da técnica de estatística multivariada de agrupamento k médias para identificar as barragens de rejeito cadastradas no Cadastro Brasileiro de Barragens da Agência Nacional de Mineração que sejam semelhantes àquelas que romperam no país nos últimos anos. A técnica foi aplicada com sucesso e foram identificados seis grupos de barragens. Os grupos 1 e 2 acondicionaram as três últimas barragens de rejeito de mineração que se romperam. Foi possível notar que muitas das barragens que se encontram em estado de emergência tem características semelhantes às que se romperam. Essa informação não significa que essas barragens se encontram em situação instável, mas as mesmas devem ser avaliadas cuidadosamente.

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