<p> Oceanic motion outside thin boundary layers is primarily a mixture of quasi-geostrophic flow and internal waves with either near-inertial frequencies or the frequency of the semidiurnal lunar tide. This dissertation seeks a deeper understanding of waves and flow through reduced models that isolate their nonlinear and coupled evolution from the Boussinesq equations. Three physical-space models are developed: an equation that describes quasi-geostrophic evolution in an arbitrary and prescribed field of hydrostatic internal waves; a three-component model that couples quasi-geostrophic flow to both near-inertial waves and the near-inertial second harmonic; and a model for the slow evolution of hydrostatic internal tides in quasi-geostrophic flow of near-arbitrary scale. This slow internal tide equation opens the path to a coupled model for the energetic interaction of quasi-geostrophic flow and oceanic internal tides. </p><p> Four results emerge. First, the wave-averaged quasi-geostrophic equation reveals that finite-amplitude waves give rise to a mean flow that advects quasi-geostrophic potential vorticity. Second is the definition of a new material invariant: Available Potential Vorticity, or APV. APV isolates the part of Ertel potential vorticity available for balanced-flow evolution in Eulerian frames and proves necessary in the separating waves and quasi-geostrophic flow. The third result, hashed out for near-inertial waves and quasi-geostrophic flow, is that wave-flow interaction leads to energy exchange even under conditions of weak nonlinearity. For storm-forced oceanic near-inertial waves the interaction often energizes waves at the expense of flow. We call this extraction of balanced quasi-geostrophic energy 'stimulated generation' since it requires externally-forced rather than spontaneously-generated waves. The fourth result is that quasi-geostrophic flow can encourage or 'catalyze' a nonlinear interaction between a near-inertial wave field and its second harmonic that transfers energy to the small near-inertial vertical scales of wave breaking and mixing. </p>

<p> Case histories in mining have long described pillars or faces of rock failing violently with an accompanying rapid ejection of debris and broken material into the working areas of the mine. These unstable failures have resulted in large losses of life and collapses of entire mine panels. Modern mining operations take significant steps to reduce the likelihood of unstable failure, however eliminating their occurrence is difficult in practice. Researchers over several decades have supplemented studies of unstable failures through the application of various numerical methods. The direction of the current research is to extend these methods and to develop improved numerical tools with which to study unstable failures in underground mining layouts. </p><p> An extensive study is first conducted on the expression of unstable failure in discrete element and finite difference methods. Simulated uniaxial compressive strength tests are run on brittle rock specimens. Stable or unstable loading conditions are applied onto the brittle specimens by a pair of elastic platens with ranging stiffnesses. Determinations of instability are established through stress and strain histories taken for the specimen and the system. </p><p> Additional numerical tools are then developed for the finite difference method to analyze unstable failure in larger mine models. Instability identifiers are established for assessing the locations and relative magnitudes of unstable failure through measures of rapid dynamic motion. An energy balance is developed which calculates the excess energy released as a result of unstable equilibria in rock systems. These tools are validated through uniaxial and triaxial compressive strength tests and are extended to models of coal pillars and a simplified mining layout. </p><p> The results of the finite difference simulations reveal that the instability identifiers and excess energy calculations provide a generalized methodology for assessing unstable failures within potentially complex mine models. These combined numerical tools may be applied in future studies to design primary and secondary supports in bump-prone conditions, evaluate retreat mining cut sequences, asses pillar de-stressing techniques, or perform backanalyses on unstable failures in select mining layouts.</p>

<p> Geothermal energy has the potential to become a substantially greater contributor to the U.S. energy market. An adequate investment in Enhanced Geothermal Systems (EGS) technology will be necessary in order to realize the potential of geothermal energy. This study presents an optimization of a waterbased Enhanced Geothermal System (EGS) modeled for AltaRock Energy&rsquo;s Newberry EGS Demonstration location. The optimization successfully integrates all three components of the geothermal system: (1) the present wellbore design, (2) the reservoir design, and (3) the surface plant design. </p><p> Since the Newberry EGS Demonstration will use an existing well (NWG 55-29), there is no optimization of the wellbore design, and the aim of the study for this component is to replicate the present wellbore conditions and design. An in-house wellbore model is used to accurately reflect the temperature and pressure changes that occur in the wellbore fluid and the surrounding casing, cement, and earth during injection and production. For the reservoir design, the existing conditions, such as temperature and pressure at depth and rock density, are incorporated into the model, and several design variables are investigated. The engineered reservoir is modeled using the reservoir simulator TOUGH2 while using the graphical interface PetraSim for visualization. Several fracture networks are investigated with the goal of determining which fracture network yields the greatest electrical output when optimized jointly with the surface plant. A topological optimization of the surface is completed to determine what type of power plant is best suited for this location, and a parametric optimization of the surface plant is completed to determine the optimal operating conditions. </p><p> The conditions present at the Newberry, Oregon EGS project site are the basis for this optimization. The subsurface conditions are favorable for the production of electricity from geothermal energy with rock temperatures exceeding 300&deg;C at a well depth of 3 km. This research was completed in collaboration with AltaRock Energy, which has provided our research group with data from the Newberry well. The purpose of this thesis is to determine the optimal conditions for operating an Enhanced Geothermal System for the production of electricity at Newberry. </p><p> It was determined that a fracture network consisting of five fractured zones carrying 15 kg/s of fluid is the best reservoir design out of those investigated in this study. Also, it was found that 100 m spacing between the fractured zones should be implemented as opposed to only 50 m of spacing. A double-flash steam power plant provides the best method of utilization of the geothermal fluid. For the maximum amount of electricity generation over the 30-year operating lifetime, the cyclone separator should operate at 205&deg;C and the flash vessel should operate at 125&deg;C.</p>

Lakes sediments from the Lofoten Islands, Norway, can be used to generate well resolved records of past climate and environmental change. This dissertation presents three lacustrine paleoenvironmental reconstructions that show evidence for Holocene climate changes associated with North Atlantic climate dynamics and relative sea-level variations driven by glacio-isostatic adjustment. This study also uses distal tephra deposits (cryptotephra) from Icelandic volcanic eruptions to improve the chronologies of these reconstructions and explores new approaches to crypto-tephrochronology. Past and present conditions at Vikjordvatnet, Fiskebølvatnet, and Heimerdalsvatnet were studied during four field seasons conducted from 2007–2010. Initially, each lake was characterized by measuring water column chemistry, logging annual temperature fluctuations, and conducting bathymetric and seismic surveys. Sediment cores were then collected and analyzed using multiple techniques, including: sediment density, magnetic susceptibility, loss-on-ignition, total carbon and nitrogen, δ13C and δ 15N of organic matter, and elemental compositions acquired by scanning X-ray fluorescence. Chronologies were established using radiocarbon dating and tephrochronology. A 13.8 cal ka BP record from Vikjordvatnet provides evidence for glacial activity during the Younger Dryas cold interval and exhibits trends in Ti, Fe, and organic content during the Holocene that correlate with regional millennial-scale climate trends and provide evidence for more rapid events. A 9.7 cal ka BP record from Fiskebølvatnet shows a strong signal of sediment inwashing likely driven by local geomorphic conditions, although there is evidence that increased inwashing at the onset of the Neoglacial could have been associated with increased precipitation. Heimerdalsvatnet provides a record of relative sea-level change. A 7.8 cal ka BP sedimentary record reflects changes in salinity and water column conditions as the lake was isolated and defines sea-level regression following the Tapes transgression. Cryptotephra horizons were identified in sediments of Heimerdalsvatnet, Vikjordvatnet, and Sverigedalsvatn. They were also found in a Viking-age boathouse excavated along the shore of Inner Borgpollen. These include the GA4-85, BIP-24a, SILK-N2, Askja, 860 Layer B, Hekla 1158, Hekla 1104, Vedde Ash, and Saksunarvatn tephra. This research project also explored the use of scanning XRF to locate cryptotephra in lacustrine sediments and presents experimental results of XRF scans of tephra-spiked synthetic sediment cores.

Two lakes were studied in detail for rock magnetic properties: Lake El'gygytgyn, a crater lake formed 3.6Ma in the Far Eastern Russian Arctic, and Heimerdalsvatnet, a Holocene coastal lake located in the Lofotens off the coast of northern Norway. These two lakes have vastly different environmental histories, the former a terrestrial lake formed from a meteor impact and never covered by continental ice sheets whereas the latter went from a coastal marine setting to a completely lacustrine environment due to isostatic rebound and sea level fluctuations. Their differences are considerable, however they provide the opportunity to compare Arctic lake systems to discern similarities and differences in their magnetic properties for application to future climatic investigations. Paleomagnetic measurements and down-core magnetic susceptibility were performed at the GFZ German Research Centre for Geosciences in Potsdam for Lake El'gygytgyn and at the Laboratoire de paleomagnétisme sédimentaire at ISMER for Heimerdalsvatnet. Rock magnetic properties were measured at the University of Massachusetts Amherst, Institute of Rock Magnetism, and/or Trinity College. These measurements included: magnetic susceptibility, hysteresis parameters, Curie temperatures, and low-temperature magnetic behavior. Imaging of magnetite grains was also performed. Magnetic susceptibility measurements in Lake El'gygytgyn suggested a correlation between glacials (interglacials) and low (high) susceptibility. The large range in susceptibility indicated there could be magnetite dissolution. The first study supported this hypothesis with evidence at low temperatures (10-35K) of minerals such as siderite, rhodochrosite, and/or vivianite which could form from iron released during dissolution. Marine Isotope Stage 31 was investigated for rock magnetic properties that could continue to support or oppose findings from the first study. It was determined the presence of siderite only occurred in interglacial periods whereas its absence (and probably presence of vivianite) related to glacial periods, indicating more reduced environments during glacials versus interglacials. Heimerdalsvatnet paleomagnetic data from the marine environment (lower part of the core) revealed scattered directions whereas data from the upper part of the core (lacustrine environment) showed better consistency. Rock magnetic measurements showed some variation downcore, however the measurements are not dependable since the amount of paramagnetic material was overwhelming compared to any ferromagnetic mineral present.

The solvent extraction of yttrium and neodymium from copper pregnant leach solutions (PLS) using Primene JM-T, a primary aliphatic amine, has been studied. Effect of contact time, pH, sulfate concentration, and extractant concentration were investigated using synthetic and actual PLS systems. Standard experimental conditions were 5 minute contact time, pH ~2.5, 10% v/v Primene JM-T concentration, and 1:1 O:A phase ratio. Distribution isotherms were constructed for the pure systems and for actual copper leach solutions. Synthetic solutions contained 100 ppm Y and ~75 ppm Nd. Copper PLS contained 2.1 ppm Nd and 14.9 ppm Y. Results showed that complete extraction of both yttrium and neodymium occurred within five minutes and at pH values greater than 1. It was also found that sulfate concentration does not inhibit extraction at any concentration. Additionally, the distribution isotherms created show that extraction for these metals can operationally take place in one stage from both synthetic solutions and copper leach solutions.

The assessment of fragmentation is an important aspect of the design and planning of any excavation. The distribution of fragment sizes in situ helps assess the requirement of explosive energy to excavate the rock material. In addition, the information can also be used to evaluate the ground water flow, leaching characteristics and the requirement of additional rock handling equipment in construction projects. In the block cave mining method, the assessment of in situ and secondary fragmentation is an integral part of the design of the excavations at the extraction level and the selection of material handling systems for transporting the ore to the processing stations. Secondary blasting requirements can also be estimated based on the fragment size distributions developed for the block cave. Methods of estimating fragment size distributions in block cave mines have been based on joint set parameters estimated from structural mapping in available excavations or outcrops. While this is acceptable in the absence of any other means of assessing the fragmentation, the results can often be misleading since the structural mapping is often carried out in limited areas and the results applied uniformly to the entire deposit. This new study proposes to use the core piece lengths information gathered from the boreholes to develop in situ and primary fragmentation estimates for block cave operations. Under this proposed study, drill core piece lengths from an exploration program in Indonesia will be used along with structural mapping data to develop estimates for in situ and primary fragment size distributions. Methods for estimating secondary fragmentation from primary fragmentation will be evaluated and the estimates of secondary fragmentation from the different methods will be compared with the actual fragmentation characteristics observed at the drawpoints. The primary assumption in the development of primary fragment size distributions from drill core data is that each drill hole piece represents one in situ rock block. The relationships between the joint spacings and lengths of the different joint sets, evaluated from the joint set characteristics gathered from available excavations, outcrops or oriented core drilling programs, can be utilized for estimating the shape of the rock blocks.

The loading cycle in an Open Pit mine is a critical stage in the production process that needs to be controlled in detail for performance optimization. A comprehensive Alert System designed to notify supervisors of cycle times that are below the required performance standards is proposed. The system gives an alert message when one or several trucks are idle or the time of completing production tasks are over a predefined value. This alert is identified by the system and compared with pre-established Key Performance Indicators (KPIs) in order to determine corrective actions. The goal is to determine the strategies that help the production supervisor to optimize the haulage cycle model. A discrete-event simulator has been built in order to analyze different scenarios for route design and queue analysis. A methodology that utilizes different algorithms has been developed in order to identify the least productive times of the fleet. These results are displayed every time the simulation has finished. This research focuses on the optimization of haulage. However, the system is intended for implementation in subsequent stages of the production process, and the resulting improvement could impact mine planning and management as well. Topographic and drilling exploration data from a mine located hypothetically in the state of Arizona, were used to build a block model and to design an open pit; an Arena-based simulation was used to generate operating cycles that represent actual operations (As-Is model). Once the Alert System is implemented, adjustments were applied, and a new simulation was performed taking into consideration these adjustments (To-Be model), including comparative analysis and statistical results.

Covering approximately (57%) of the country's surface area the main basin of the geology of the Karoo Supergroup in South Africa has an important influence on the materials used in the construction of transport infrastructure in South Africa. The Karoo Dolerite Suite often serves as the only competent material in this otherwise sedimentary basin but on numerous occasions rapid premature failures of pavements constructed with Karoo Dolerite base courses have been attributed to the poor durability of these materials. The research presented here attempts to determine if the cause of such rapid failures can be attributed to dolerite durability deficiencies and if so if the durability of the material can be predicted using the current specifications to which these materials are required to conform with. The methodology followed was to perform comprehensive material investigations on selected pavement sections where Karoo Dolerite had been used as a base course aggregate. Eight suitable sites, ranging in age from two months to 10 years, were selected and comparative testing performed on samples of material obtained from the source quarries and pavement layers at each. Three of these sites experienced rapid failure that was suspected to be due to base course aggregate degradation. The tests performed included those specified by South African standards and a selection of new tests derived from published literature on alternative tests and proposed basic igneous rock degradation models. Well established tests were completed with relative ease while newer tests and newly proposed tests required additional development. The materials from at least two poor performance sites was shown to have undergone various degrees of degradation after quarrying which manifested itself primarily as a loss in resistance to attrition and abrasion forces. The variability in the inherent resistance of the material to these forces was also noted to have contributed to the poor performance of at least two sites. It is therefore proven that degradation of Karoo Dolerites after quarrying can occur and contribute to the poor performance of pavements but also that the variability in a source quarry can result in poor performance without material degradation. The prediction of material durability is possible but requires numerous tests to be performed on representative samples, particularly to identify variations in material properties. Petrographic properties that result in variable material properties and a susceptibility to further alteration included high degrees of deuteric and metasomatic alteration of primary minerals, especially the fine matrix minerals. It has been shown that the accurate quantification of such alteration is not feasible using easily available analysis techniques and therefore that no specifications can be based thereon. The current material specifications have been shown to not accurately predict the durability of Karoo Dolerite, primarily due to the inability to activate the mechanism by which material physical degradation occurs, namely the expansion of clay minerals within the aggregate. The only exception was the water absorption test performed on core samples, which was able to identify poor materials. Tests that were able to predict the durability included the modified versions of previously specified tests (e.g. ethylene glycol soaked aggregate impact value and ethylene glycol soaked modified durability mill index) and newly proposed testing methods (e.g. modified ethylene glycol durability index and shear wave velocity). Preliminary specifications for these have been proposed. The initial development of an aggregate expansion test has also shown a strong ability to predict Karoo Dolerite durability and is proposed for further development. Ultimately the use of poor durability Karoo Dolerite results in two changes in the material properties. The first effect is the production of more fines during construction, which can result in an unsuitable amount of fines (as identified by a low coarse sand ratio). The second effect is an increase in plasticity index and linear shrinkage of the material<0.425mm to levels considered marginal based on the current specifications. The shear strength of a Karoo Dolerite base course layer has been shown to be sensitive to such changes in plasticity index and linear shrinkage and the reduction of the current specification limit to ensure materials are non-plastic and/or non-expansive may therefore be justified.

Slip on the geometrically complex Rhyolite Ridge Fault System and associated local stresses in the Desert Peak Geothermal Field in Nevada, were modeled with the boundary element method (BEM) implemented in Poly3D. The impact of uncertainty in the fault geometry at depth, the tectonic stresses driving slip, and the potential ranges of frictional strength resisting slip on the likely predictions of fracture slip and formation in the surrounding volume due to these local stresses were systematically explored and quantified. The effect of parameter uncertainty was evaluated by determining the frequency distribution of model predicted values. Alternatively, Bayesian statistics were used to determine the best fitting values for parameters within a probability distribution derived from the difference of the model prediction from the observed data. This approach honors the relative contribution of uncertainties from all existing data that constrains the fault parameters. Lastly, conceptual models for different fault geometries and their evolution were heuristically explored and the predictions of local stress states were compared to available measurements of the local stresses, fault and fracture patterns at the surface and in boreholes, and the spatial extent of the geothermal field. The complex fault geometry leads to a high degree of variability in the locations experiencing stress states that promote fracture, but such locations generally correlate with the main injection and production wells at Desert Peak. In addition, the strongest and most common stress concentrations occur within relays between unconnected fault segments, and at bends and intersections in faults that connect overlapping fault segments associated with relays. The modeling approach in this study tests the conceptual model of the fault geometry at Desert Peak while honoring mechanical constants and available constraints on driving stresses and provides a framework that aids in geothermal exploration by predicting the spatial variations in stresses likely to cause and reactivate fractures necessary to sustain hydrothermal fluid flow. This approach also quantifies the relative sensitivity of such predictions to fault geometry, remote stress, and friction, and determines the best fitting model with its associated probability. / Geology