Resumen El desarrollo de proyectos mineros en etapas de exploración y prefactibilidad conlleva desafíos relacionados a la heterogeneidad e incertidumbre geológica y de procesamiento debido a la variabilidad en sus atributos primarios y de respuesta. Por lo tanto, el objetivo de esta investigación radica en elaborar el modelo geometalúrgico del índice de trabajo de Bond. Para esto se desarrollaron modelos de regresión lineal en Jupyter Notebook considerando 790 muestras de resistencia a la compresión uniaxial de la roca (UCS), litologías, zonas minerales e índice de trabajo de Bond (BWi) en un depósito pórfido cuprífero. Los resultados indican relación directamente proporcional de tipo lineal entre el BWi y UCS, generando modelamientos con desempeños aceptables de R2 entre 0,76 a 0,90. Además, las litologías y zonas mineralizadas en el depósito estudiado son características relevantes relacionadas a la conminución. Finalmente, de acuerdo a la competencia de la roca, esta se clasifica como tipo media a dura, dura y muy dura en las zonas de óxidos, mixtos y sulfuros primarios respectivamente.

Abstract The development of mining projects in the exploration and pre-feasibility stages involves challenges related to geological and processing heterogeneity and uncertainty due to variability in their primary and response attributes. Therefore, the objective of this research is to develop the geometallurgical model of the Bond work index. For this purpose, linear regression models were developed in Jupyter Notebook considering 790 samples of uniaxial compressive strength of rock (UCS), lithologies, mineral zones and Bond work index (BWi) in a porphyry copper deposit. The results indicate a directly proportional linear relationship between BWi and UCS, generating modeling with acceptable R2 performances between 0,76 and 0,90. In addition, the lithologies and ore zones in the deposit studied are relevant characteristics related to comminution. Finally, according to rock competence, the rock is classified as medium to hard, hard and very hard in the oxide, mixed and primary sulfide zones, respectively.

Abstract As historical waste has accumulated in dams, the interest in studying the feasibility of reusing mining tailings has grown, offering both environmental and economic advantages. However, given the unique characteristics of each site, conducting site-specific assessments is crucial. Building on a detailed evaluation of the Cocoruto Dam in Nova Lima, Minas Gerais, this study presents a technical feasibility and financial viability analysis of three potential reprocessing scenarios. The primary objective was to assess the viability and potential benefits of reusing Au tailings. The proposed methods involve grinding, calcination and leaching, with designs adaptable for existing metallurgical plants. Considering the economic potential of Au in these inactive mine tailings (with an average grade of 0.95 mg/kg and a total resource of 3,350.55 tonnes), multiple factors were analyzed to determine the feasibility of Au production from this source. Analyzed variables included: cut-off grades and tonnage for each scenario; net present value (NPV) calculated with an 8% annual discount rate; a general slope angle of 20 degrees; three possible final pit configurations; different annual production rates (400,000 t, 800,000 t and 1,000,000 t), and various Au ounce values ($1300/oz, $1500/oz, and $1700/oz). From a financial perspective, for all ounce values and an annual production of 400 tonnes, all scenarios prove profitable. However, other risks and parameters should be further evaluated. dams grown advantages However site sitespecific specific crucial Lima Gerais grinding leaching plants 095 0 95 0.9 mgkg mg kg 335055 3 350 55 3,350.5 tonnes , tonnes) source included cutoff cut off scenario NPV (NPV 8 rate 2 degrees configurations 400,000 400000 000 (400,00 800000 800 800,00 1000000 1 1,000,00 t) $1300/oz, 1300oz oz 1300 ($1300/oz 1500oz 1500 $1500/oz $1700/oz. 1700oz $1700/oz . 1700 $1700/oz) perspective 40 profitable evaluated 09 9 0. 33505 35 5 3,350. 400,00 40000 00 (400,0 80000 80 800,0 100000 1,000,0 $1300/oz 130 150 170 4 3350 3,350 400,0 4000 (400, 8000 800, 10000 1,000, 13 15 17 335 3,35 400, (400 1000 1,000 33 3,3 (40 100 1,00 3, (4 10 1,0 ( 1,

Resumen Objetivo: el propósito de este estudio de viabilidad previa fue examinar percepciones y experiencias con respecto a la actividad Sit-to-stand entre los adultos mayores de Brasil que viven en sus hogares en comunidades urbanas. Método: el método de exploración se enfocó en la etnografía. Se utilizó muestreo intencional para reclutar 20 adultos mayores. Se emplearon cinco medios para generar datos, a saber: encuestas sociodemográficas, observaciones participantes, entrevistas informales, entrevistas formales semiestructuradas y notas de campo. Para el análisis de los datos se recurrió a análisis de contenido cualitativo. Resultados: la experiencia de los adultos mayores con problemas de movilidad en relación con la actividad Sit-to-stand dependió de sus expectativas en torno a la movilidad, las cuales implicaron muchos factores que actuaron en conjunto para influenciar sus creencias y actitudes con respecto a la actividad, al igual que preferencias, conductas y percepciones culturales. Aparentemente, a los participantes de este estudio la actividad les resultó amena; sin embargo, los inconvenientes más notorios para adoptar la actividad Sit-to-stand surgió en la forma de déficits en sus necesidades personales e intrapersonales. Conclusión: las recomendaciones resultantes de los hallazgos del estudio indican la necesidad de diseñar estrategias de implementación para la intervención Sit-to-stand a la medida de las necesidades de este grupo poblacional específico. Objetivo Sittostand Sit to stand urbanas Método etnografía 2 saber sociodemográficas informales campo cualitativo Resultados preferencias culturales Aparentemente amena embargo intrapersonales Conclusión específico

Abstract Objective: the purpose of this pre-feasibility study was to examine perceptions and experiences of a Sit-to-stand activity with urban Brazilian community-dwelling older people in their homes. Method: the exploration method was focused ethnography. Purposive sampling was used to recruit 20 older people. Five means of data generation were used, namely: socio-demographic surveys, participant observations, informal interviews, formal semi-structured interviews, and field notes. Data analysis was qualitative content analysis. Results: the experience of mobility-challenged older people with the Sit-to-stand activity was dependent on their mobility expectations involving many factors that worked together to influence their beliefs and attitudes towards the activity, preferences, behaviors, and cultural perceptions. The participants of this study seemed to find the activity enjoyable; however, the most noticeable shortcomings for their engagement in the Sit-to-stand activity emerged as gaps in their personal and intrapersonal needs. Conclusion: the recommendations generated from the study findings call for the design of implementation strategies for the Sit-to-stand intervention that are tailored to this particular population’s needs. Objective prefeasibility pre feasibility Sittostand Sit stand communitydwelling community dwelling homes Method ethnography 2 namely sociodemographic socio demographic surveys observations interviews semistructured semi structured notes Results mobilitychallenged challenged preferences behaviors enjoyable however needs Conclusion populations population s

Resumo Objetivo: o objetivo deste estudo de pré-viabilidade foi examinar percepções e experiências da atividade de Sit-to-stand com idosos brasileiros residentes em suas casas, no meio urbano. Método: o método exploratório foi etnografia focada. Foi utilizada a amostragem intencional para recrutar 20 idosos. Foram utilizados cinco meios de geração de dados: inquéritos sociodemográficos, observações participantes, entrevistas informais, entrevistas formais semiestruturadas e notas de campo. Os dados foram analisados mediante análise de conteúdo qualitativo. Resultados: a experiência dos idosos com problemas de mobilidade na realização da atividade Sit-to-stand dependia de suas expectativas de mobilidade envolvendo muitos fatores coordenados que, de forma conjunta, influenciaram suas crenças e atitudes em relação à atividade, suas preferências, seus comportamentos e percepções culturais. Os participantes deste estudo pareciam considerar a atividade aprazível; no entanto, as deficiências mais perceptíveis para o engajamento dos participantes na atividade Sit-to-stand surgiram de falhas em suas necessidades pessoais e intrapessoais. Conclusão: as recomendações geradas a partir dos achados do estudo convocam a concepção de estratégias de implementação da intervenção Sit-to-stand adaptadas às necessidades dessa população em particular. Objetivo préviabilidade pré viabilidade Sittostand Sit to stand casas urbano Método focada 2 sociodemográficos informais campo qualitativo Resultados que conjunta preferências culturais aprazível entanto intrapessoais Conclusão particular

RESUMO O trabalho apresenta uma análise técnica, ambiental e econômica da integração da tecnología solar fotovoltaica, com a rede interligada que atualmente fornece energia elétrica para o Instituto Tecnológico Metropolitano (ITM), campus Robledo, para o período 2015-2019, e considerando três cenários; 80.000, 100.000 e 120.000 kWh de demanda mensal coberta com esta fonte renovável. A instalação através de módulos solares policristalinos, evita a emissão de grandes quantidades de CO2. Para o sistema de 80.000 kWh / mês, obtém-se uma redução de 75,79 % nas emissões de gases de efeito estufa associadas ao consumo de energia elétrica do sistema interligado nacional. Com 100.000 kWh/mês, consegue-se uma redução de 95,41 % e com 120.000 kWh/mês, uma redução de 95,58 %. Em termos econômicos, é calculado o indicador financeiro TIR (taxa interna de retorno), para um horizonte de tempo de 5 anos e considerando a economia na compra de energia elétrica como receita. O melhor cenário seria o de 100.000 kWh/mês, pois apresenta a maior TIR, investimento inicial, menores custos de instalação e manutenção, enquanto o de 120.000 kWh/mês apresenta menor TIR e maiores custos operacionais. CLASSIFICAÇÃO JEL: I23, O13, Q42, Q56 CONTEÚDO: Introdução; 1. Por que energia solar fotovoltaica (PV)? 1.1 Tecnologias disponíveis para sistemas fotovoltaicos; 2. Considerações sobre o projeto de um sistema fotovoltaico sem armazenamento, para a geração de energia elétrica; 3. Condições para o projeto de um sistema fotovoltaico para geração de energia elétrica no ITM; 4. Consumo de energia elétrica no campus Robledo da ITM; 5. Projeto conceitual e Análise de pré-viabilidade técnica, econômica e ambiental; Conclusões; Referências.

RESUMEN El trabajo muestra un análisis técnico, ambiental y económico de la integración de tecnología solar fotovoltaica con la red interconectada que le suministra energía eléctrica en la actualidad al Instituto Tecnológico Metropolitano campus Robledo (ITM), para el periodo 2015-2019. Se consideran tres escenarios: 80.000, 100.000 y 120.000 kWh de demanda mensual cubierta con esta fuente renovable. Para la instalación se itulizaron módulos solares policristalinos que evitan la emisión de CO2. Para el sistema de 80.000 kWh/mes se logra una reducción del 75,79 % de las emisiones de gases efecto invernadero asociadas al consumo de electricidad del Sistema Interconectado Nacional. Con 100.000 kWh/mes, se alcanza una reducción del 95,41 % y con 120.000 kWh/mes, una del 95,58 %. En términos económicos, se calcula el indicador financiero TIR (Tasa Interna de Retorno), para un horizonte de tiempo de cinco años y considerando los ahorros en la compra de energía eléctrica como ingresos. El mejor escenario sería el de 100.000 kWh/mes, ya que este presenta la TIR más alta, inversión inicial, costos de instalación y mantenimiento más bajos, mientras que el de los 120.000 kWh/mes presenta una TIR menor y costos operativos más altos. CLASIFICACIÓN JEL: I23, O13, Q42, Q56 CONTENIDO: Introducción; 1. ¿Por qué energía solar fotovoltaica (FV)?; 2. Consideraciones sobre el diseño de un sistema fotovoltaico sin almacenamiento, para la generación de energía eléctrica; 3. Condiciones para el diseño de un sistema fotovoltaico para la generación de energía eléctrica en el ITM; 4. Consumo de electricidad en el ITM campus Robledo; 5. Diseño conceptual y análisis de prefactibilidad técnico, económico y ambiental; Conclusiones; y Referencias

ABSTRACT The work shows a technical, environmental and economic analysis of the integration of photovoltaic solar technology, with the interconnected network that currently supplies electricity to the Metropolitan Technological Institute, Robledo campus, for the 2015-2019 period , and considering three scenarios; 80,000, 100,000 and 120,000 kWh of monthly demand covered with this renewable source. The installation, using polycrystalline solar modules, avoids the emission of large amounts of CO2. For the 80,000 kWh / month system, a 75,79 % reduction in greenhouse gasses emissions associated with electricity consumption from the national interconnected system is achieved. With 100,000 kWh / month, a reduction of 95,41 % is achieved and with 120,000 kWh / month, a reduction of 95,58 %. In economic terms, the financial indicator IRR (internal rate of return) is calculated for a time horizon of 5 years and considering the savings in the purchase of electricity as income. The best scenario would be 100,000 kWh / month, since this presents the highest IRR, initial investment, lower installation and maintenance costs, while that of 120,000 kWh / month presents a lower IRR and higher operating costs. JEL CLASSIFICATION: I23, O13, Q42, Q56 CONTENTS: Introduction; 1. Why photovoltaic solar energy (PV) ?; 1.1 Technologies available for PV systems; 2. Considerations on the design of a photovoltaic system without storage, for the generation of electrical energy; 3. Conditions for the design of a photovoltaic system for the generation of electrical energy at the ITM; 4. Electricity consumption in the ITM campus Robledo; 5. Conceptual design and technical, economic and environmental pre-feasibility analysis; Conclusions; References.

Resumen En la actualidad, aprovechar instalaciones en la industria para modificar, reanimar o reconvertir sus producciones, resulta importante para la disminución de costos inversionistas y el incremento de la disponibilidad de las plantas. En este sentido, la investigación tiene como objetivo realizar un estudio previo inversionista, en un complejo azucarero con plantas de derivados instaladas, para la producción conjunta de furfural, etanol y tableros a partir de bagazo, considerando la reconversión en la instalación industrial. Para ello, se parten de modificaciones y resultados obtenidos por Mesa [1], en la etapa de fraccionamiento del bagazo hacia la obtención de glucosa, xilosa y furfural, y el aprovechamiento de los residuos en la planta de tableros Morales-Zamora [2]. Se realizan estudios de prefactibilidad económica a las plantas por separado y con la propuesta de integración y reconversión. En el análisis integrado, se plantea un diseño factorial 24 considerando la influencia de las variables flujo de caña, flujo de etanol, fiabilidad y precios, para un escenario optimista de precios y capacidades. Los resultados económicos se favorecen para incrementos del flujo de etanol, con menor flujo de caña, considerando la fiabilidad con la reconversión y con incrementos del precio del azúcar. La reconversión hacia la obtención de azúcar, electricidad, furfural, tableros y etanol permitirá rescatar plantas y equipamientos instalados, lo cual incidiría a minimizar las inversiones, así como a un desarrollo prospectivo de adaptación de la industria azucarera hacia el concepto de biorrefinería.

Abstract Nowadays, take advantage of facilities in the industry to modify, reanimation or revamping their productions is necessary for the reduction of investment costs and the increase of the availability of the plants. In this sense, the investigation aims to carry out a prior investor study in a sugar complex with installed derivatives plants, for the joint production of furfural, ethanol, and boards from bagasse, considering the revamp of the industrial facility. For this, it starts from modifications and results obtained by Mesa [1], in the bagasse fractionation stage towards getting glucose, xylose, and furfural and the use of residues in the board plant for Morales-Zamora [2]. Economic pre-feasibility studies are carried out for the plants separately along with the integration and revamp proposal. In the integrated analysis, a factorial design is proposed 24 considering the influence of the variables: sugarcane flow, ethanol flow, reliability and prices, for an optimistic scenario of prices and capacities. The economic results are favored for increases in the flow of ethanol, with a lower flow of cane, considering the reliability with the reconversion and with increases in the price of sugar. The reconversion towards obtaining sugar, electricity, furfural, boards and ethanol will be able to rescue installed plants and equipment, which would have an impact on minimizing investments, as well as a prospective development of adaptation of the sugar industry towards the concept of biorefinery.

Resumo Atualmente, aproveitem as facilidades da indústria para modificar, reanimação ou reconversão suas produções, é importante para a redução dos custos de investimento e o aumento da disponibilidade das plantas. Nesse sentido, a investigação visa a realização de um estudo prévio com investidor, em um complexo sucroalcooleiro com usinas de derivados instaladas, para a produção conjunta de furfural, etanol e placas a partir do bagaço, considerando a reconversão no parque industrial. Para tanto, partimos das modificações e resultados obtidos por Mesa [1], na etapa de fracionamento do bagaço para a obtenção de glicose, xilose e furfural, e a utilização de resíduos na planta de papelão Morales-Zamora [2]. Os estudos de pré-viabilidade econômica são realizados para as usinas separadamente e com a proposta de integração e reconversão. Na análise integrada, é proposto um planejamento fatorial 24 considerando a influência das variáveis fluxo da cana, fluxo do etanol, confiabilidade e preços, para um cenário otimista de preços e capacidades. Os resultados econômicos são favorecidos por aumentos no escoamento de etanol, com menor escoamento de cana, considerando a confiabilidade com a reconversão e com aumentos no preço do açúcar. A reconversão para a obtenção de açúcar, eletricidade, furfural, placas e etanol possibilitará o resgate de usinas e equipamentos instalados, o que impactaria a minimização de investimentos, bem como um desenvolvimento prospectivo de adaptação da indústria açucareira ao conceito de biorrefinaria.

Resumen Contexto: Este estudio analiza el efecto de la suciedad en la eficiencia energética de dos configuraciones de sistemas de generación fotovoltaica: una fija y una móvil (con seguimiento solar). Método: Se implementó un sistema especial de soporte y medición de la potencia de salida adaptado para cada configuración. Se recopilaron datos durante dos meses en Bogotá. El análisis utiliza la potencia promedio de dos módulos fotovoltaicos policristalinos de 50Wque forman parte de cada configuración. Se asignó un módulo de prueba para la aplicación de un protocolo de limpieza, y el otro fue asignado como módulo control. A partir de este resultado se analizó la prefactibilidad para la autosuficiencia energética de un hogar promedio de ingreso medio. Resultados: La aplicación de un protocolo de limpieza regular aumenta la productividad energética de cada sistema fotovoltaico entre un 3,87% y un 7,23 %, de acuerdo con su configuración. A nivel económico, este incremento representa la amortización del sistema fotovoltaico para autosuficiencia energética un año antes, sin importar la configuración empleada. Conclusiones: Se encontró un impacto positivo en la eficiencia energética bajo un protocolo de limpieza regular en Bogotá. Este beneficio permite aumentar la rentabilidad obtenida de la inversión en un sistema para autoabastecimiento energético de una familia promedio. Agradecimientos: Este trabajo fue financiado por la Universidad Antonio Nariño a través del proyecto No. 2018230. Los autores agradecen el soporte dado por la Universidad EAN en este trabajo.

Abstract Context: This study analyzes the soiling effect on the energy efficiency of two photovoltaic generation system configurations: one fixed and one mobile (with solar tracking). Method: A support system and output power measurement adapted for each configuration was implemented. Data was collected during two months in Bogotá. This analysis considered the average power obtained in two 50 W polycrystalline photovoltaic modules integrating each configuration. A test module was assigned for applying a cleaning protocol in each configuration, and the remaining module was assigned as a control module. This result was used in a pre-feasibility analysis for energy self-sufficiency of an average, middle-income household. Results: A regular cleaning protocol increases the energy productivity of each analyzed photovoltaic system in 3,87% and 7,23 %, according to its configuration. Additionally, at the economic level, this increase in productivity represents the year-prior amortization of a photovoltaic system for energy selfsufficiency, regardless of the type of configuration used. Conclusions: A positive impact on the energy efficiency of the two photovoltaic configurations analyzed was found under a regular cleaning protocol in Bogotá. This benefit increases the profitability that could be obtained from investing a system for the energy self-sufficiency of an average family. Acknowledgements: This work has been funded by Universidad Antonio Nariño through project No. 2018230. The authors would like to thank Universidad EAN for supporting this study.

Resumen: Este documento expone una investigación que tiene como objetivo aportar a la mitigación del cambio climático, además de buscar autonomía energética basándose en Energías Renovables. Por tal motivo esta investigación evalúa la prefactibilidad de un sistema de almacenamiento de energía renovable basado en bombeo de agua en la isla San Cristóbal - Galápagos, donde se tiene una fuente de energía almacenada debido a la diferencia de nivel disponible en la laguna El Junco. Se realizan los cálculos en base a la curva de demanda de la isla durante el año 2018, contando con que se desea cubrir el pico de dicha demanda de energía de la noche que se encuentra entre las 16h00 y las 22h00. Se calculan los tanques de almacenamiento de acuerdo al volumen requerido además de las características que deben tener los generadores de energía. Para el retorno del agua usada en la generación se calcula un sistema de bombeo en base a la energía obtenida por medio del recurso eólico de San Cristóbal, mismo que corresponde a 3 aerogeneradores de los cuales se analiza su curva de potencia, y junto con la velocidad promedio del viento por hora durante el año 2018, se obtiene la energía entregada por los aerogeneradores para realizar el bombeo requerido, además de las características de las bombas. Los resultados muestran que la propuesta es viable en vista de que se cubre la demanda del pico de la noche, considerando que la energía usada es netamente renovable.

Abstract: This document presents an investigation that aims to contribute to the mitigation of climate change, in addition to seeking energy autonomy based on Renewable Energy. For that reason, this research evaluates the prefeasibility of a renewable energy storage system based on water pumping on San Cristóbal - Galápagos Island, where there is a potential energy source located in El Junco lagoon. For this, the calculations were made based on the island's demand curve during 2018, taking into account that it is desired to cover the peak of such energy demand -at night that is between 16:00h and 22:00h-. Storage tanks are calculated according to the required volume, in addition to the characteristics that the generators may have to cover that peak demand. For the return of the water used in the generation, a pumping system is calculated based on the energy obtained through the wind resource of San Cristóbal, which corresponds to 3 wind turbines -of which its power curve is analyzed together with the average speed of the wind per hour during 2018-. The energy delivered by the wind turbines to carry out the required pumping is obtained, in addition to the required characteristics of the pumps. The results demonstrate that the proposal is viable given that the demand for the night peak is covered, considering that the energy used is purely renewable.

ABSTRACT The Paraguayan agricultural producer is in constant risk, due to price variations and climatic threats. In this context, biodigesters could help to generate additional profits with the use of biogas and digestate produced from sources found in the agricultural environment. For this purpose, a technical and economic pre-feasibility study is carried out, which was achieved from the experiences obtained in the “Concordia-SC Project” - Brazil and the KTBL of Germany. In this way, 3 scenarios of complementation of pig manure with corn and wheat were proposed for anaerobic digestion in industrial biodigesters in large-scale agricultural projects. The results showed that in scenario 1 (pig manure) 25.8% IRR was obtained; scenario 2 (pig manure and corn silage) IRR 31.7%; and scenario 3 (pig manure and wheat grains) IRR 27.2%. At the same time, in scenario 2, an opportunity cost of US $ 33,197 was obtained and in scenario 3, US $ 5,455, respectively, in favor of the use of biodigesters. Finally, the possible savings in fertilization from the digestate resulted in US $ 114,093, 148,502 and 132,565 in N, P2O5 and K2O respectively. The results show that the inclusion of biodigesters in the productive chain of the soy, wheat and corn complex can support the obtaining of greater profitability for the producer, while reducing the risk to which it is exposed.

RESUMEN El productor agropecuario paraguayo se ve en constante riesgo debido a las variaciones de precios y amenazas climáticas. En ese sentido, los biodigestores podrían apoyar para generar ganancias adicionales con la utilización del biogás y el digestato producido a partir de fuentes encontradas en el medio agropecuario. Para dicho fin, se realiza un estudio de pre-factibilidad técnica y económica que se logró a partir de las experiencias obtenidas en el “Proyecto Concordia-SC” - Brasil y la KTBL de Alemania. De esa manera se plantearon 3 escenarios de complementación del estiércol de cerdo con el maíz y el trigo para la digestión anaeróbica en biodigestores industriales en proyectos agropecuarios de gran escala. Los resultados arrojaron que en el escenario 1 (estiércol de cerdo) se obtuvo TIR 25,8%; el escenario 2 (estiércol de cerdo y ensilaje de maíz) TIR 31,7% y el escenario 3 (estiércol de cerdo y granos de trigo) TIR 27,2%. Al mismo tiempo en el escenario 2 se obtuvo un costo de oportunidad de US$ 33.197 y en el escenario 3 US$ 5.455 respectivamente a favor de la utilización de biodigestores. Por último, el posible ahorro en fertilización a partir del digestato dio como resultado US$ 114.093, 148.502 y 132.565 en N, P2O5 y K2O respectivamente. Los resultados hablan de que la inclusión de biodigestores en la cadena productiva del complejo soja, trigo y maíz puede apoyar a la obtención de mayor rentabilidad para el productor, al tiempo de disminuir el riesgo al que se expone.

Thorncliffe Chrome Mine, one of Glencore's Eastern Chrome operations, is currently mining the Middle Group No.1(MG1) chromitite layer and is conducting a pre-feasibility study for an expansion project to mine the Middle Group chromitite No.2 (MG2) layer. This paper focuses on identifying viable areas within the MG2 layer that adhere to the mining, geological, and rock engineering parameters for a safe multiple-reef operation; and establishing efficient ways of accessing and extracting the MG2 chromitite layer. The findings from the multi-reef project at Samancor's Tweefontein Mine (Gouvea, 2013) and Maritz (2015) emphasized that the best layout for a safe and stable multi-reef operation is one where pillars are superimposed. The guidelines by Salamon and Oravecz (1976) were key in the selection criteria for pillar stability. A stage gate analysis was used to identify mineable areas using the success selection criteria for mineability obtained from geotechnical and geostatistical analysis of the assay data and isopach plan. During this study, it was found that the most cost-efficient way of accessing the MG2 chromitite layer is from the MG1 mining horizon through a connecting ramp instead of sinking a shaft. Moreover, using the MG1 infrastructure during the development of the MG2 mining horizon will reduce the project development cost. A bord-and-pillar layout with superimposed pillars will assist in reducing the stress concentrations and interactions between the two mining horizons. With all the considerations being satisfied, it can be concluded that the MG2 layer is viable to mine in a safe manner along with the MG1 layer in a multi-reef environment.

Abstract: The objective of this research was to evaluate the best alternative for a second access connection to improve traffic flow conditions between the city of Manizales and the municipality of Villamaría. The methodology used territorial accessibility of global nature as an impact evaluation element. This was performed by quantifying the savings generated in average travel times when compared to that of the existing connection (basis). The proposed intervention on the present study generates a positive impact for both municipalities by generating time savings of up to 22% in travel time. It can be argued that using territorial accessibility allows efficient evaluation of the best intervention option for transport investment projects in a pre-feasibility stage.

Resumen: El objetivo de la presente investigación consiste en evaluar la mejor alternativa para la segunda conexión de acceso entre la ciudad de Manizales y el municipio de Villamaría, bajo la necesidad de mejorar las condiciones del flujo vehicular, incrementado por la condición de conurbación existente. La metodología de estudio emplea la accesibilidad territorial, de carácter global, como elemento de evaluación de impacto, a través del cálculo y cuantificación del ahorro generado en los tiempos promedio de viaje, tomando como base el análisis de la conexión actual. Como principal resultado se obtiene que las intervenciones propuestas, generan un impacto positivo entre ambas municipalidades, generando ahorros de tiempo del 22% en el tiempo de viaje. Como conclusión principal, se puede argumentar que el uso de la accesibilidad territorial permite evaluar de forma eficaz, la mejor opción de intervención en una etapa de pre factibilidad en proyectos de inversión en transporte.

Abstract Compost is a bio-fertilizer that contains nutrients, organic matter, water and microorganisms that benefit the integrity of agroecosystems. Compost quality is highly dependent on the characteristics of the materials employed in production. One of the main challenges in compost technology is quality optimization. MM are microbial cultures containing dense populations of native soil microorganisms including bacteria, fungi and actinomycetes. LDBIO are the precipitated solids found in anaerobic reactors. This is a low cost, non-experimental, economic, low resolution pre-feasibility study that uses robust laboratory analytical methods to identify whether these compounds can be used as compost optimization agents, and identify the combination of these materials that produce the highest quality compost. According the results obtained, there is empirical evidence that MM and LDBIO have potential as compost optimization agents. The compost with the best quality characteristics (macronutrient concentration, organic matter, carbon and water content, microbial biomass) is the one that contains both MM and LDBIO. The incorporation of these materials in the compost does not affect other compost quality parameters such as pH, EC and C/N ratio. It does not affect the maturity, stability and innocuity of compost. Therefore, at this level of resolution, it is concluded that it is feasible to continue researching these materials as compost optimization agents. It is recommended to implement plant growth-response tests in order to identify the potential of the optimized compost to enhance plant development.

Resumen El compost es un abono orgánico que puede aportar nutrientes, materia orgánica, humedad y microorganismos benéficos al agroecosistema. La calidad del compost depende en gran medida de las características de los materiales que se empleen en el proceso de elaboración, por lo que uno de los retos existentes en la tecnología del compostaje es la optimización de la calidad del material terminado. Los MM son inóculos microbianos con altas poblaciones principalmente de hongos, bacterias y actinomicetos que se encuentran naturalmente en el suelo, mientras que los LDBIO son los sólidos precipitados resultantes del proceso de digestión anaeróbica. El empleo de MM y LDBIO como agentes optimizadores de la calidad del compost no ha sido estudiado. El presente trabajo tiene como objetivo investigar, en forma no experimental, económica, y a un nivel de resolución macro utilizando pruebas de laboratorio robustas, si el MM y LDBIO poseen características favorables como agentes efectivos para la optimización del compost, e identificar la combinación de estos materiales que permita producir compost de mayor calidad. De acuerdo con los datos obtenidos, se logra evidenciar a ese nivel de resolución, que efectivamente los MM y LDBIO presentan características apropiadas como agentes optimizadores del compost. El compost que presenta las mejores características de calidad en cuanto a la concentración de macronutrientes, contenido de materia orgánica, carbono, retención de humedad y concentración de biomasa microbiana, es el que contiene MM y LDBIO en forma integrada. La incorporación de estos compuestos no afecta otros parámetros de calidad de este abono, incluyendo el pH, la CE y la relación C/N. Tampoco afecta la capacidad de maduración, la estabilidad y la inocuidad del compost final, por lo que se concluye que es factible continuar invirtiendo en la investigación de estos compuestos como agentes optimizadores del compost. Se recomienda realizar ensayos de respuesta de crecimiento con el abono optimizado para identificar el potencial de aporte al desarrollo de los cultivos.

The School of Mining Engineering (Wits Mining) at the University of the Witwatersrand (Wits) has a final-year course called 'Mine Design'. The objective of this course is to ensure that students utilize the knowledge gained not only during the four years of coursework, but also during their vacation work, to conduct a mine planning and design exercise at the pre-feasibility study level. The overall objective of the course is to enable the students to follow a rigorous method of ascertaining the technical and economic viability of a project. Any conclusion arrived at, either positive or negative, is acceptable provided that logical and quantifiable reasons are given. The students have to use mine planning software in order to complete the study. The setting up of a practical layout for a proposed mining operation, with the associated expenditure, will permit the students to make a substantiated recommendation regarding the viability of mining the deposit. In order to include ventilation aspects, only underground design projects are made available. Mine planning and design is done in groups, and each group prepares a coherent and professionally consolidated report and presentation that are presented to staff members, external examiners, and their peers. To assist the students to complete the project, the fully-equipped Mine Design Laboratory is made available. This paper looks into the steps that are involved for a successful completion of the Mine Design course.

Abstract The original design of the planned Izmir Bay Immersed Tube Tunnel, considered it to be a continuous subsea tunnel for the whole length of about 7.6 km. But this was later changed into having 2 shorter tubes of 2.7 km long each connected thru’ a 2.2 km long artificial island created in the middle of the bay from the excess dredged material, a concept which also reduces costs and increases efficiency. This island will serve as a venue for the 2025 Expo Exhibition, which Izmir city will apply to organize in the future. Reason for the research study was to provide a preliminary design, using a dynamic analysis, during the current pre-feasibility stage, of the immersed tunnel to show whether it can be built across the Izmir Bay. This paper takes into account the new alignment and presents the results of a 2-D dynamic analysis conducted of the prefabricated 100m long tunnel elements, sitting within a backfilled dredged ditch, dug after the recommended ground improvement was carried out. Analyses considered staged construction and the results showed that: Tunnel units and its surrounding soils inside the dredged ditch act together to provide a better earthquake response with a damping effect of the earthquake force; Tunnel units do not float to the sea surface, but continued to stay inside the dredged ditch and applied positive stresses to the foundations during the design earthquakes. As there was no floating, there was no need for anchoring the tunnel to ditch bottom; Tunnel units and immersion joints (made of specified strong elastomer material) continued to stay in compression longitudinally and provided a superb water-tightness level; There were no risky (un-tolerable) ground deformations during, after striking of the design earthquakes. Total vertical and differential displacements of the tunnel units and in the surrounding soils were all at acceptable levels; Concrete surface crack widths occurring in the tunnel units, during striking of the design earthquakes were also found to be allowable. Study results show that the tunnel elements can withstand Mw=7 short duration (<10 sec) or Mw=6 long duration (>10 sec) earthquakes without major damages to their structure.

Resumen El diseño original del Túnel de Tubo Inmerso en la Bahía de Esmirna, considerado como un túnel submarino continuo para toda la longitud de aproximadamente 7.6 km. Pero más tarde se cambió a 2 tubos más cortos de 2,7 km de longitud conectados cada uno a través de una isla artificial de 2,2 km de longitud creada en el medio de la bahía por el exceso de material dragado, un concepto que también reduce los costos y aumenta la eficiencia. Esta isla servirá como sede para la Exposición Expo 2025, que la ciudad de Izmir aplicará para organizar en el futuro. La razón del estudio de investigación fue proporcionar un diseño preliminar, utilizando un análisis dinámico, durante la etapa actual de prefactibilidad, del túnel sumergido para mostrar si se puede construir a través de la bahía de Izmir. Este documento toma en cuenta la nueva alineación y presenta los resultados de un análisis dinámico bidimensional realizado de los elementos de túnel prefabricados de 100 m de largo, asentados dentro de una zanja de dragado rellenada, excavada después de que se llevara a cabo la mejora de suelo recomendada. Los análisis consideraron la construcción por etapas y los resultados mostraron que: Las unidades de túnel y sus suelos circundantes dentro de la zanja de dragado actúan en conjunto para proporcionar una mejor respuesta a los terremotos con un efecto amortiguador de la fuerza sísmica; Las unidades de túnel no flotan en la superficie del mar, sino que permanecieron dentro de la zanja de dragado y aplicaron esfuerzos positivos a las cimentaciones durante los terremotos de diseño. Como no había flotación, no había necesidad de anclar el túnel para dejar el fondo; Las unidades de túnel y las juntas de inmersión (hechas de un material de elastómero fuerte especificado) continuaron comprimiéndose longitudinalmente y proporcionaron un excelente nivel de impermeabilidad; No hubo deformaciones de terreno arriesgadas (no tolerables) durante, después de golpear los terremotos de diseño. Los desplazamientos verticales y diferenciales totales de las unidades del túnel y en los suelos circundantes se encontraban en niveles aceptables; Anchuras de grietas superficiales de concreto que ocurren en las unidades del túnel, durante el golpeteo de los terremotos de diseño también se encontraron permitidas. Los resultados del estudio muestran que los elementos del túnel pueden soportar Mw = 7 terremotos de corta duración (<10 segundos) o Mw = 6 de larga duración (> 10 segundos) sin daños importantes en su estructura.

Phosphate is one of the substances which wastewater treatment works (WWTW) have to lower in order to meet the South African regulatory discharge standard of 1 mg/L. Wastewater is increasingly viewed as a 'water-carried waste', presenting opportunities for resource recovery. South Africa has commenced its transition to a low-carbon and resource-efficient economy, all whilst it struggles to provide universal access to basic needs and is faced with massive infrastructure maintenance as well as upgrading backlogs in the sanitation sector in particular. Although phosphate recovery methods exist, there is little evidence to indicate that these techniques would be economically viable or socially accepted in South Africa. This paper explores the potential for centralized recovery of nutrients, through the conceptual design and techno-economic pre-feasibility assessment of two phosphate recovery options, at the largest WWTW in the Western Cape, South Africa. This assessment revealed that the digestate stream at the 200 ML/d Cape Flats WWTW (CFWWTW) has the potential to produce ~470 kg/d of struvite fertilizer, whilst recovering 4-8% of the plant's costs in 20 years. When contrasted with the more familiar, yet less sustainable, chemical precipitation process, low-grade and high-grade struvite production establishment costs are 10 and 25 times higher, respectively. Still, to reduce effluent phosphate loading to within regulated standards, the low-grade struvite production option at an estimated net present cost of R25.4 million over a 20-year lifetime is more affordable than chemical precipitation at a net present cost of R51.2 million. Low-grade struvite production is thus concluded to be technically feasible and the economically most affordable option from a lifecycle-costs perspective. Although it is a simple process, it is not cheap. Municipalities will need to consider the lower operating costs, as well as the environmental benefit of producing a useful phosphate fertilizer, over the immediate capital investment, if they decide to install such an operation.

Platinum is a highly valuable resource, its safe and economic extraction is paramount. The success of platinum mining by the bord and pillar method depends heavily on a comprehensive and dependable pillar design method. Pillars need to be large enough to safely support the load and small enough to avoid loss of resources. A critical evaluation of current pillar design systems used in narrow-reef platinum mining was undertaken using practical experience from a large feasibility-stage platinum exploration project, supplemented by observations from several platinum mines in Zimbabwe. An extensive literature survey was undertaken in order to determine the current status of design systems. Through this approach, the shortcomings of current pillar design systems are highlighted. Areas are proposed for further research to obtain a better understanding on how additional factors influence pillar system stability. The exploration work highlighted how rock mass classification methods can be utilized in determining the overall strength of pillars. Current pillar design systems for narrow-reef platinum mining consider width-to-height-ratio (usually with different exponents for width and height) and the strength of the pillar material. However, there are many more important factors that are not considered and which have a bearing on pillar system stability. An in-depth study of these parameters with a view to establish effective narrow- reef platinum mining pillar design systems needs to be undertaken.