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The sublevel caving mining method is a mass production method with potentially very low operational costs. The success of this method is dependent on, among other factors, the cavability of the orebody and the overlying rock mass. However, caving of the surrounding rock mass also results in deformations in the cap rock as well as on the ground surface above the orebody being mined. From this follows that any existing infrastructure on the ground surface must be relocated as not to be affected by the mining-induced deformations.This thesis work was undertaken to bring about a better understanding of the rock mass behavior in the cap rock of non-daylighting orebodies, with particular application to the Printzsköld orebody as part of the LKAB Malmberget Mine. Rock testing, field observations and underground mapping was conducted to characterize the rock mass in the caving environment. A methodology for identifying the caving front based on seismic monitoring data was derived by studying the Fabian orebody (which has caved to surface), and using laser scanning data for validation. The methodology was then applied to the Printzsköld orebody to identify the caving front.Numerical modeling was performed for various scenarios of the rock mass as mining proceeded. Modeling included (i) stress analysis to understand stress changes and their effects on the rock mass behavior, (ii) discontinuum numerical modeling to quantify the influence of large-scale geological structures on the cave progression, and (iii) discontinuum cave modeling to simulate possible cave mechanisms in the cap rock more explicitly. Laser scanning together with seismic event data were used to calibrate the numerical models.The numerical simulation results showed that as mining progresses, the cap rock and hangingwall were exposed to stress changes that resulted in yielding. Two failure mechanisms were predominantly at play (i) shear failure (dominant in the cap rock) and (ii) tensile failure (dominant in the hangingwall). The presence of the large-scale structures affected thenearfield stresses through slip along the cave boundaries. The effect of the structures on the far field stresses were less significant.Discontinuum modeling to explicitly simulate failure and caving involved simulating the rock mass as a jointed medium using Voronoi tessellations in 2D, and bonded block modeling (BBM) in 3D. Both the 2D and the 3D modeling results showed fair agreement when comparing the inferred boundary of the seismogenic zone, with that identified from seismic monitoring data. Predictive numerical modeling was conducted for future planned mining to assess future cave development in the cap rock. The results from 3D modeling indicated that cave breakthrough for the Printzsköld orebody is expected when mining the 1023 m level, corresponding to approximately year 2022, as per current mining plans. The 2D model was non-conservative with cave breakthrough predicted to occur when mining the 1109 m level, corresponding to the year 2028.The estimated boundary between the seismogenic and yielded zones, as defined in the Duplancic and Brady conceptual model of caving, was coinciding with, or was close to, the cave boundary in the Printzsköld orebody. This may imply that in some areas the yielded zone was not present and that the Duplancic and Brady model may not be universally applicable. Additional work is required to verify this indication, as well as to fine-tune the modeling methodology.

Made available in DSpace on 2016-04-27T18:15:45Z (GMT). No. of bitstreams: 1 Carlos Eduardo Martins.pdf: 12919368 bytes, checksum: dc12ff2b7d2dc395f9a2d8deb33ad004 (MD5) Previous issue date: 2014-10-20 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This text deals with the importance of a karst spring. The Cachoeira do Córrego do Couto is one of the attractions of the Parque Estadual e Turístico do Alto Ribeira - PETAR, Iporanga - SP. The site is a resurgence of existing karst aquifer in a range between depressed carbonate rock saws higher impervious surfaces. The aquifer is composed of autologous and allogeneic systems water recharge, characterized for this reason as a mixed karst. As the object of study is a component of a landscape that remains dynamic relationships with society and also presents aspects of natural and human history, it is believed that the best approach for implementation of this work is the concept of geosystem. The concept is quite geosystem employed in studies of objects that have a natural origin, but are influenced by human activities. The results of the surveys carried out are a zoning map of the karst. In this map, the features are at the same time, resulting from and interact in the morphogenetic process responsible for landscape planning in the context of PETAR aims to provide recreation visitors for their aesthetic attributes / Este trabalho trata sobre a importância de uma fonte cárstica, a Cachoeira do Córrego do Couto que é um dos atrativos turísticos do Parque Estadual e Turístico do Alto Ribeira PETAR, Iporanga SP. O local é a ressurgência de um aquífero cárstico existente em uma faixa de rocha carbonática deprimida entre serras de superfícies impermeáveis mais elevadas. O aquífero mencionado é composto por sistemas de recarga alogênicos e autogênicos, caracterizando-se por este motivo como um carste misto. Como o objeto de estudo é um componente de uma paisagem que mantém relações históricas e bastante dinâmicas com a sociedade guardando aspectos da história natural e até mesmo humana regional, julgou-se que a melhor forma de abordagem para o desenvolvimento deste trabalho seria o conceito de Geossistema. O conceito de Geossistema é bastante empregado em estudos de objetos que tenham origem natural, mas que sejam influenciados pelas atividades humanas. O resultado dos levantamentos levados a efeito é um mapa de zoneamento do carste estudado no qual as feições são, ao mesmo tempo, resultantes do e interagem no processo morfogenético responsável pelo ordenamento da paisagem que no contexto do PETAR tem a finalidade de proporcionar a recreação dos visitantes por seus atributos estéticos

Ingeniero Civil de Minas / El presente informe consiste en evaluar la explotación combinada de los recursos Toki y Quetena. El método comprende una explotación subterránea mediante Block Caving con el cual se pretende extraer los sulfuros y posteriormente aplicar lixiviación In Place sobre el material remanente compuesto principalmente por óxidos y mixtos. La lixiviación In Place, definida como la lixiviación sobre material fragmentado posterior a una intervención minera, considera a favor la misma infraestructura construida para la aplicación del Block Caving. El método consiste básicamente en la irrigación del mineral a partir de la solución lixiviante la cual es inyectada por pozos ascendentes de 100 m de altura ubicados en la intersección de zanjas y galerías presentes en el nivel de producción. Las soluciones captadas en la base del material fragmentado son enviadas a la Planta SX-EW donde el cobre es recuperado. Los yacimientos Toki y Quetena de tipo pórfidos cupríferos están ubicados entre 2 a 5 kilómetros al noroeste de Calama. Los cuerpos están cubiertos bajo una capa de gravas estériles, cuya potencia media es de 100 metros. La mineralización predominante en el caso de los sulfuros es calcopirita y bornita, mientras que para los recursos lixiviables son principalmente óxidos verdes (malaquita-crisocola, menores arcillas con cobre). El mineral se explota a partir de tres sectores: Quetena, Toki Norte y Toki Sur. En los dos primeros se realiza una explotación combinada, mientras que en el tercero solo es rentable la extracción de sulfuros mediante Block Caving. El total de reservas sulfuradas es de 126 MTon, con ley de cobre media de 0.6 %, mientras que en el caso de los óxidos se determinaron 20.3 MTon de reservas a una ley media 0.41%. Se estipuló a partir del plan de producción un ritmo medio de 40.000 TPD para la extracción de sulfuros y de 70,000 TMF/año para el proyecto global. La evaluación económica fue realizada a partir de un precio del cobre 2.8 US$/lb cuya fuente son las orientaciones comerciales asociadas al largo plazo. El proyecto es rentable en un escenario probable del precio del cobre, donde el VAN es de 180 MUS$ con una inversión requerida de 526 MUS$, que como punto a favor cuenta con el ahorro asociado a los gastos de construcción de las plantas concentradora y SX-EW por estar disponibles en el distrito.

Ingeniero Civil de Minas / La productividad en la industria minera está en la agenda del sector y es un desafío constante el cómo medir efectivamente las obras de construcción en los proyectos mineros subterráneos, donde las condiciones inherentes del método de explotación junto a la arquitectura mina, dificultan las labores. El trabajo a desarrollar tiene como objetivo principal generar una metodología para cuantificar la productividad y llevar a cabo un seguimiento de la preparación minera en proyectos subterráneos explotados por Block/Panel Caving. La metodología propuesta corresponde a la construcción de indicadores de productividad en base a la definición de eficiencia y eficacia. Cuantificando la eficiencia en base a la utilización de los recursos, por medio de la relación entre lo que se produce y los elementos productivos que participan en el proceso. Y la eficacia a través de la obtención de las metas planificadas, con un indicador del porcentaje de cumplimiento del avance físico con respecto al programa. Se definen diferentes métricas que ayudan a determinar la velocidad de construcción, cuantificando la magnitud y/o volumen de actividades que se realizan en los últimos años en la División El Teniente, específicamente para los sectores de Esmeralda, Reservas Norte y Diablo Regimiento. Para la estimación de la productividad se recopila información histórica del control y seguimiento del cumplimiento físico y financiero de las obras junto al número de trabajadores que están relacionados. Los resultados arrojan que la División el Teniente en el periodo del 2006 2015 ha aumentado su eficiencia medida con el indicador propuesto en un 90%, y presenta un cumplimiento promedio del 91%, ubicándose en una zona de alta productividad. Para cada uno de los sectores, los resultados dieron que todos han aumentado su eficiencia en el periodo de 2011 2015. Esmeralda en un 74%, Reservas Norte un 59% y Diablo Regimiento un 84%, mientras que la eficacia con el cumplimiento ha sido más variable para cada sector. Finalmente, la productividad calculada con esta metodología, tiene dos funciones, servir como parámetro de mejoramiento en procesos futuros y como registro histórico y línea base para comparaciones más adelante. / 26/01/2022

The current environmental status of the majority of Bermuda’s one hundred sixty-six known caves was investigated. This survey replicated a historical cave study performed in 1983, wherein each was analyzed for positive and negative features. Statistical analysis of the data showed a significant difference between the historical and current survey ratings, with an overall decrease in environmental status. A water quality study was performed on twenty different caves with sea level pools in various locations around the island. Nitrate, nitrite, ammonia, and phosphate levels were measured from varying depths in these caves. Fifteen of these caves were also tested for the presence of fecal bacterial contamination. High nitrate levels were discovered in some of the caves, particularly in surface samples. Additionally, bacterial contamination was detected in some caves. No obvious relationship between cave size or location and contamination existed for any of the pollutants sampled. Three separate caves from this group were dived and analyzed using a Hydrolab Sonde 3 Multiprobe Logger to acquire in situ water column data including depth, temperature, pH, salinity, and dissolved oxygen. Each cave studied had its own unique trends in hydrology at varying depths in the water column. A later water sampling study with a randomized experimental design was created and caves were divided into four classes based on size and location. Surface and subsurface samples were gathered from twelve randomly selected caves, three from each class. Each sample was analyzed for nitrate, nitrite, and ammonia concentrations. The results were analyzed using multiple analysis of variance statistics. A significant difference between the nitrate concentrations in the surface and subsurface water samples was discovered. None of the other comparisons were statistically significant. To represent the data visually, a Bermuda Cave and Karst Information System (BeCKIS) was created using the environmental survey data and water quality information. Some of the maps generated highlighted regions where negative environmental impacts on caves were concentrated geographically, thus demonstrating how this geographic information system could be used as a conservation tool.

The current environmental status of the majority of Bermuda’s one hundred sixty-six known caves was investigated. This survey replicated a historical cave study performed in 1983, wherein each was analyzed for positive and negative features. Statistical analysis of the data showed a significant difference between the historical and current survey ratings, with an overall decrease in environmental status. A water quality study was performed on twenty different caves with sea level pools in various locations around the island. Nitrate, nitrite, ammonia, and phosphate levels were measured from varying depths in these caves. Fifteen of these caves were also tested for the presence of fecal bacterial contamination. High nitrate levels were discovered in some of the caves, particularly in surface samples. Additionally, bacterial contamination was detected in some caves. No obvious relationship between cave size or location and contamination existed for any of the pollutants sampled. Three separate caves from this group were dived and analyzed using a Hydrolab Sonde 3 Multiprobe Logger to acquire in situ water column data including depth, temperature, pH, salinity, and dissolved oxygen. Each cave studied had its own unique trends in hydrology at varying depths in the water column. A later water sampling study with a randomized experimental design was created and caves were divided into four classes based on size and location. Surface and subsurface samples were gathered from twelve randomly selected caves, three from each class. Each sample was analyzed for nitrate, nitrite, and ammonia concentrations. The results were analyzed using multiple analysis of variance statistics. A significant difference between the nitrate concentrations in the surface and subsurface water samples was discovered. None of the other comparisons were statistically significant. To represent the data visually, a Bermuda Cave and Karst Information System (BeCKIS) was created using the environmental survey data and water quality information. Some of the maps generated highlighted regions where negative environmental impacts on caves were concentrated geographically, thus demonstrating how this geographic information system could be used as a conservation tool.

Autor no autoriza el acceso a texto completo de su documento hasta el 5/5/2021. / Ingeniero Civil de Minas / En minas explotadas por el método de panel caving convencional, la ocurrencia de eventos tales como colapsos o estallidos de roca ha sido frecuente a lo largo de la historia. Ambas situaciones conducen a pérdidas productivas y a un aumento de los costos, puesto que se debe desarrollar un proyecto de contingencia para recuperar las reservas afectadas. Los eventos sísmicos son propios del proceso de caving. Sin embargo, en algunos casos existe una anomalía donde la cantidad de sismos supera los valores normales. Esta anomalía ocurre como consecuencia de la inestabilidad geomecánica insostenible del sector afectado. El caso de estudio en este trabajo, comprende la recuperación del frente de hundimiento del sector Centro-Fw de la mina Reservas Norte, División El Teniente, luego de un evento geomecánico ocurrido en el mes de marzo del año 2014. Cabe destacar que en este caso se pudo evitar que los daños aumentaran y causaran el colapso de las galerías de la mina. El principal objetivo de este estudio es documentar la recuperación de un sector, que se vio afectado por daños geomecánicos severos en las galerías del nivel de hundimiento, y cuyo resultado principal fue permitir la continuidad de la variante de explotación y evitar que se genere un colapso. Para abordar este trabajo se debió caracterizar detalladamente el caso de estudio, para identificar las actividades claves en este. Así, se realizó un ordenamiento y análisis de los hechos, que permitió documentar de manera clara los aspectos relevantes para la recuperación del sector estudiado. Gracias a las actividades realizadas fue posible reiniciar el frente de hundimiento y, más importante aún, se pudo continuar con el sistema de explotación, sin necesidad de implementar una variante en este. El diseño de la solución y la planificación de la extracción, resultaron posibles gracias al sistema de extracción del sector (variante convencional). Esto genera una ventaja para la variante convencional de panel caving, la cual se puede considerar para la elección del método de explotación en proyectos futuros. Así, dadas las actividades claves identificadas en el caso de estudio y considerando el éxito en el trabajo realizado, se listan las actividades claves para afrontar daños geomecánicos severos ubicados por delante del frente de hundimiento. Estas actividades claves generan una importante fuente de información, en caso de la ocurrencia de eventos similares en un futuro. Dentro de las actividades claves identificadas en el caso de estudio, se realiza una recomendación con respecto al diseño de la solución, específicamente en el diagrama de perforaciones. Esta modificación implica reducir el largo de las perforaciones realizadas desde el nivel de producción, permitiendo disminuir costos y tiempo de desarrollo.

Sublevel caving operations at great depths are subjected both to large stress concentrations that are redistributed as the mining front progresses and to mining-induced seismicity. This is the case for Kiirunavaara mine, Sweden’s largest underground mine. Since the mine was declared seismically active in 2007 / 2008, large rockfalls controlled by structures have happened in many parts of the mine, despite the use of rock support systems designed for bearing dynamic loads. A novel layout for sublevel caving operations, internally named “fork layout” is being tested at a satellite mine. This layout was conceived to place the ore-parallel longitudinal footwall drifts further away from the contact between the orebody and footwall drifts. That way, the differential stresses that generate stress-related damages are expected to be reduced. However, the effect of implementing the fork layout on the hazard potential for structurally controlled rockfalls has not been studied in detail yet. Large rockfalls that occurred in different parts of the mine were analysed with respect to their structures, location of the damage event and type of excavation. The majority of these occurred at footwall drift intersections. Information from damage mapping and seismic events that triggered these rockfalls was used to generate a conceptual model that illustrates the relative spatial relation between the seismic source and damage location. In addition, the seismic source parameters of the events that triggered these rockfalls were processed using scaling laws to obtain ground motion parameters such as peak particle velocity and acceleration at the damage site. The effect of implementing the fork layout on rockfall hazard was tested in the intersections between footwall drifts and crosscuts (FD-CC), and intersections between access and footwall drifts (AD-FD) in two production blocks, using the traditional layout for sublevel caving mining as a point of comparison. Two different fork layouts were tested, FD-CC at 80° (or AD-FD at 100°) and FD-CC at 70° (or AD-FD at 110°). Structural data available from face mapping and oriented core logging was used to define predominant joint sets at the investigated blocks. Using the structural input, wedge volumes at the intersections were modelled deterministically and probabilistically in Unwedge. The variations in wedge volumes formed at the intersections between layouts were used as a proxy for rockfall potential, meaning that if a layout reduced the wedge size, the smaller the rockfall hazard if triggered by a seismic event, and vice versa. It was concluded that most rockfalls at the FD-CC intersections are controlled by structures from three major joint sets. It was observed that rockfalls at FD-CC intersections occurred more often at certain footwall drift orientations. Many seismic events that triggered these rockfalls are located close to the ore passes and generated ground accelerations between 0.5 to 10 times the gravity acceleration. Implementing fork layouts with FD-CC at 80° intersection angle generates larger wedges than the traditional layout and thus, scenarios with a higher rockfall hazard. On the other hand, using fork layouts with FD-CC at 70° intersection angle reduces wedge size at the southern FD-CC intersections; hence, the rockfall hazard is reduced in these intersections. In the northern FD-CC intersections, the wedge volumes are increased and thus, a higher rockfall potential is generated in these intersections. AD-FD at 110° intersection angle generates also a smaller rockfall hazard than the traditional layout in both production blocks.

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