Mines Repository (Colorado School of Mines)
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Quartz on chrysosolla
No full textPhotographed by Ron Wolf.Quartz on botryoidal masses of light blue chrysocolla
Evaluation and optimization of the performance of radial cutting tools on borer miners in evaporitic rocks
No full textIncludes bibliographical references.2024 Spring.Mechanical excavation is the dominant mode of operation in underground mining and tunneling in low- to medium-strength rock types. Drag-type cutting tools used on related machines vary from radial tools for very soft and non-abrasive rocks to point attack or conical tools, also known as pick cutters, in medium-strength and more abrasive rocks. Tool wear and maintenance are important parts of the operation, as they may impact production rates due to excessive wear and inefficient cutting processes, as well as negatively impact machine utilization, resulting in reduced production per shift or per day.
This study investigates the performance of radial rock cutting tools used on borer miners, focusing on the cutterhead profiles typical to gage regions of borer miner rotors, as well as the rate of wear and resulting cutting forces. Analysis of field data was used to assess the impact of tool wear on machine performance and to establish testing criteria for full-scale linear cutting machine (LCM) tests to simulate the cutting conditions experienced on the rotors. Beyond a standard LCM test, this study introduced a tilted-bit LCM test procedure to simulate the gage area of the cutterhead, where bits are installed at high tilt angles, as a means to develop a realistic understanding of cutter-rock interaction in the gage region. A 3D scanner is utilized to create point cloud data of the rock surface to evaluate the surface characteristics of the rock and enable assessment of the ridge buildup area between the cuts. Through a combination of analyses and computer modeling techniques, a comprehensive methodology is established to facilitate a detailed quantification of operational parameters influencing cutter-rock interaction, affecting performance and cutting tool lifespan.
The study reveals that the standard LCM testing method oversimplifies the complex dynamics at variable axial spacing at higher tilt angles. The side force component is significant at higher tilt angles and is expected to contribute to frequent tip failures and even exceed radial bit design limits. Findings show cutting forces vary substantially when alternating sequences due to changes in rock exposure and relief timing.
Integrating 3D scanning in rock cutting helps surface characterization with improved precision and quantifies supplemental factors like overbreak volumes, ridge heights, and breakout angles, complementing traditional measurement and analysis of cutting forces and product grain size distribution assessments. Integrating these additional metrics with standardized specific energy and particle size distribution evaluations, as well as simulated wear levels of cutting tools, provides better insights into cutter-rock interaction. These capabilities provide the means to develop proper strategies for optimizing operation and cutterhead design.
A validated corner-cutting evaluation methodology has been introduced to facilitate accounting for operational factors in addition to typical cutting geometry. To incorporate operational parameters, input variables are carefully chosen to accurately reflect the cutting scenario, representing the rock encountered by the bit either directly or indirectly. These geometric factors dynamically adjust in response to variations in the rate of machine advance. Various modeling techniques were considered, each utilizing a different set of input parameters. The selection of the models presented in this study was determined by their ability to accurately capture the variability across all three orthogonal components of the cutting force.
The machine performance prediction model introduced at the EMI of CSM is based on the cumulative cutting force consumption by the individual cutting tool on the cutterhead with respect to its position and orientation. The model allows for estimation of the cutting forces for a given bit based on the measured values through full-scale LCM tests. This allows the model to incorporate full-scale testing results into the performance estimation and predict the machine's instantaneous performance, considering the specific wear level of the cutting tools on the cutterhead. A key update to the EMI-CSM modeling concept allows performance prediction with progressive wear and its corresponding effects on machine performance parameters. This can be seen as a step forward in cutterhead wear modeling, particularly when assessing machine performance in constant geological conditions. This improvement ultimately refines the modeling process, where, through simulation of the cutting process, one can develop optimal operational parameters and bit/cutter management strategies and address related scheduling issues
Sustained release of biologics by poly(lactic-co-glycolic acid) particles and porous contact lenses
No full textIncludes bibliographical references.2024 Summer.A few decades back, a new class of drugs called biologics started gaining prominence. Biologics are a broad class of drugs which include protein, peptide, and nucleic acid-based therapies. Differences in sizes and stability compared to the small molecule drugs result in different challenges in development of biologics for treating diseases. Biologics are typically not delivered orally like small molecule drugs as they lose efficacy due to enzymes in the gut and have difficulty in passing through the epithelium to reach systemic circulation. Intravenous or subcutaneous injections and transdermal delivery are commonly used. Some challenges of biologic delivery could be addressed by incorporating biologics into biomaterials to improve stability and to sustain release to match the desired pharmacokinetics. This thesis focuses on designing biologic delivery approaches to achieve the desired pharmacokinetics for two applications – delivery of vaccine and delivery of ophthalmic drugs.
As new diseases and new variants of existing diseases arise, there is a need for development of new vaccines as well as improving existing vaccines by modifying formulations and improving delivery to achieve desirable pharmacokinetics with less frequent dosing. This thesis addresses both issues by developing particles for sustained release of influenza virus in combination with natural-killer T cell (NKT) agonist. Biodegradable poly (lactic-co-glycolic acid) (PLGA) particles were prepared by double emulsion method to load both NKT agonist α-galactosylceramide (α-GalCer) and the deactivated influenza virus. Particles were developed with >80% encapsulation efficiency and >2 months of release duration.
Ophthalmic drugs are frequently delivered via eye drops despite many deficiencies including rapid clearance from tears which limits bioavailability particularly for large molecular weight biologics. Biologics such as anti-VEGF are delivered via intravitreal injection, i.e., injection directly into the eye. As an alternative, contact lenses were designed to sustain release of biologics to achieve higher permeation in the eye and eliminate invasive injections. Lenses were made with a clear center and porous annulus to load proteins. Lenses were manufactured by a novel approach involving stepwise polymerization in a rotating tube to form a rod. The rod was cut into discs, dried, and lathe-cut into lenses. The approach was successful in manufacturing contact lenses with properties consistent with commercial lenses with the additional feature of loading biologics in the porous annulus, providing sustained release for a few hours
Elbaite
No full textPhotographed by Ron Wolf.Resinous green-orange elbaite, Ohio City district, Gunnison County, Colorado
Synthesis and applications of organophosphonic acid compounds as extractants for rare earth element separation and beyond
No full textIncludes bibliographical references.2024 Spring.The realization of a shift from traditional energy sources towards more environmentally friendly alternatives has led to an ever-growing need for essential raw materials such as rare earth elements (REEs). Nuclear energy, catalysis, phosphors, superconductors, permanent magnets, and optical materials rely heavily on REEs. Consequently, a crucial area of technology is the extraction and isolation of REEs from complex mixtures. Chemical homogeneity causes various REEs to accumulate in source minerals, making it more challenging for their separation and obtaining commercially feasible pure elements requires multistage extractions and repeated separation techniques. Solvent extraction is a commercially employed technique for separating rare earth metals. Extractants are crucial to the separation process because they can form complexes with the water-soluble REE cations and switch their solubility into the organic phase. Many extractants have been developed, including carboxylic and phosphorous acids, β-diketones, phosphorous esters, phosphine oxides, and various amines. Commercial extractants, however, have low selectivity, which renders processing time-, energy-, and solvent-intensive. Recently, promising REE separation results have been reported on organophosphorus extractants, including asymmetric dialkylphosphinic acids, monoalkylphosphinic acids, and styryl phosphonate monoesters.
In this work, two generations of aryl vinyl phosphonic acid esters were designed and synthesized. The synthesis optimization resulted in a two-step reaction allowing various high-purity aromatic vinyl phosphonic acid monoesters. Utilization of the Heck coupling reaction enabled functionalization of vinyl phosphonic acid with different aromatic and photoswitchable moieties. The employment of Steglich esterification led to the formation of two generations of organic soluble non-symmetric mono-esters. The 1st generation of extractants was complexed with Eu3+ and studied compared to traditional extractants, resulting in an unexpected finding: the order of increasing extraction strength matched the order of decreasing calculated dipole moment of the synthesized ligands rather than pKa. The 2nd generation of extractants included phosphonic acid esters containing photoswitchable moieties that are currently being studied for their extraction properties.
In another application, the employment of a versatile Heck coupling approach resulted in synthesizing 14 diverse anionic monomers capable of modular “cyanostar”-stabilized anion dimerization. The optimized synthetic approach to vinyl phosphonic acids and corresponding vinyl phosphonates allowed access to solubility-tuned ditopic monomers for preparing supramolecular polymers.
Finally, the broad scope of applicability of aryl vinyl phosphonic acids was evident from the evaluation of carbazole-based PA derivatives as self-assembled monolayer (SAM)-based hole transport/extraction layers (HTM) in perovskite solar cells. The introduction of stronger bonding molecules at the buried interface reduced the amorphous phase around perovskite/HTM/ITO interfaces and increased the stability of fabricated devices. The champion minimodule with the hybrid HTM retained operational efficiency of 17.5% after 10 weeks of outdoor testing, the first to achieve this property to our knowledge, as independently measured by the Perovskite PV Accelerator for Commercializing Technologies center
Characterizing hydrogeochemical profiles and metal(loid) transport processes from mining in Arequipa, Peru
No full textIncludes bibliographical references.2024 Summer.Acid Mine Drainage forms one of the world’s greatest environmental concerns related to metal mining activities. Effluent waters from small scale as well as large scale mining can mobilize metal(loid)s and high acidity which contaminate surrounding surface water supplies. As such, identifying the processes that control metal(loid) contaminant transport from mining related activities, mine waste, and tailings is an important step to mitigation or remediation strategies in the metals mining industry. Previous studies on Acid Mine Drainage prediction and metal(loid) transport have focused on characterizing mine wastes and tailings through through static leach tests, kinetic leach tests, leachate compositional analysis, mineralogical characterization, and geochemical modeling. Furthermore, static and kinetic leach tests are standard practices for Acid Mine Drainage prediction in the mining industry. However, this work focuses on documenting quantitative automated mineralogy as a powerful tool for Acid Mine Drainage prediction as mineral modal abundance and mineral textural properties can be captured in this analytical technique and can be used in thermodynamic models to predict the behavior of metal(loids) in waste rock and tailings. This work also focuses on documenting the contaminant-transport hydrogeochemical profiles that are controlled by tailings mineralogical properties and the mineral deposit type that is being mined. The state of Arequipa in southern Peru features a wide variety of magmatic-hydrothermal mineral deposit types which are mined by both large-scale operators and small-scale and artisanal mining (ASM). The district has diverse mineral deposit styles and diverse mining waste compositions and therefore is a suitable site for characterization of variable mining-related hydrogeochemical profiles and contaminant-transport mechanisms. Presentation of results by mineral deposit type is particularly useful for intrusion-related gold deposits which are commonly operated by ASM workers, allowing implementation of results as screening tools in formalization of this important livelihood.
In this dissertation I present studies which show that automated mineralogy can provide quantitative information on controlling mineralogical characteristics to predict AMD generation without the time and costs associated with static leach tests and leachate chemical composition analyses. Futhermore, in this dissertation I present workflows that leverage existing water quality monitoring, geological, seasonal, and mineralogical information, followed by applying statistical calculations and geochemical modeling to identify contaminant-sources and transport mechanisms to surface waters. This body of work shows the value of quantitative automated mineralogy data and how this data set can be used as an initial, quick, cost-effective tool to predict the water-contamination threats of mining mineral deposits. Additionally, I show the value of newly-developed workflows, integrating published water quality monitoring data in conjunction with quantitative mineralogical data, statistical considerations, and thermodynamic models to establish watershed-specific geochemical processes and seasonal controls on metal(loid) mobility from mining. The workflow is applied to case studies on specific watersheds in the state of Arequipa in southern Peru with contrasting water quality characteristics to identify contaminant sources and rock types that are directly responsible for acid generation or acid neutralization in mining active regions
Coal bursts in longwall mines: DAS-based monitoring strategies and numerical modeling insights
No full textIncludes bibliographical references.2024 Fall.In many nations, coal mining plays an important role in energy and steel production and provides economic opportunities for workers. However, coal miners face substantial hazards that result in injuries and fatalities each year. One such hazard is coal bursting: violent, dynamic failures that are difficult to manage and poorly understood.
This work aims to advance the management of coal burst risks in longwall mines by improving monitoring practices and the understanding of coal burst mechanics through applied geophysics and numerical modeling. The first part demonstrates several novel strategies based on distributed acoustic sensing (DAS) — a technology that uses laser pulses to measure dynamic strain in fiber optic cables — for monitoring seismicity in underground longwall coal mines. DAS cables deployed along the mine floor and in boreholes constitute a general monitoring strategy to overcome many challenges inherent in traditional (non-DAS) monitoring. Other DAS deployment approaches, such as seismoacoustic arrays near the mining face, show promise for addressing specific ground control challenges. A new open-source framework is also presented that facilitates DAS research by simplifying data processing and management.
The second part of this work focuses on understanding coal burst mechanics, particularly for coal bursts occurring near the longwall mining face. Quasi-dynamic numerical modeling is used to quantify the effects of several parameters on coal burst severity. The length of the cantilever and the strength of the coal-rock interface play the most critical roles. Similar models are used to examine the contributions of various components to the coal burst seismic wavefield. In most cases, excavation deformation dominates other source component contributions. In practice, this means far-field seismic recordings are of limited value for directly studying coal burst damage but may be useful for determining cantilever length and burst depth. Moreover, moment tensors should be used cautiously when interpreting failure mechanisms since distinct sources can produce similar moment tensors. The modeling results and geophysical data suggest that the coal bursts studied in this work initiate near the mining face and are caused by cantilever loading, elastic energy stored in the coal, and a strong coal-rock interface
Celestine
No full textPhotographed by Ron Wolf.Blocky glassy blue grey crystals of celestine, Luz mine, La Paz, San Luis Potosí, Mexico