Browsing by Author "Scalia, Joseph, committee member"
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Item Open Access Development and verification of a miniature cone penetration test(Colorado State University. Libraries, 2019) Kahramanoglu, Kubra, author; Bareither, Christopher A., advisor; Scalia, Joseph, committee member; Singleton, John, committee memberThe objectives of this research were to design and validate a miniature cone penetration test (MCPT) system for testing fine-grained soils. The system included a commercially-available miniature piezocone and a 300-mm-diameter, rigid-wall, calibration chamber. Three different materials were used in this study: (i) Ottawa sand, (ii) fine synthetic tailings (FST), and (iii) coal combustion product (CCP). Ottawa sand was used to evaluate repeatability of the MCPT apparatus and verify results via comparison to literature. The FST was a mixture of kaolin clay and silica flour, whereas CCP was primarily sand and silt and collected from a coal ash impoundment in North America. These two materials were tested to assess undrained and drained shear behavior and compare with previously measured shear strength. Replicate MCPTs conducted on Ottawa sand at three different relative densities indicated that the MCPT was repeatable. The assessment of tip resistance and sleeve friction in the Ottawa sand MCPTs were used to identify a functional depth of penetration whereby the friction sleeve was fully mobilized. Values of tip resistance and sleeve friction obtained from the MCPT at these depths of penetration were taken as representative of the specimen and subsequently validated via comparison to literature. Pore water pressure developed during cone penetration in the Ottawa sand and CCP were similar and indicative of drained conditions, whereas large, positive pore pressures in the FST were indicative of undrained conditions. The undrained shear strength estimated from MCPTs on FST (13 and 35 kPa) compared favorably and had a good agreement with undrained shear strength from triaxial tests. The effective stress friction angle for CCP based on MCPT (28.7° and 30.4°) yielded a conservative estimate relative to a previously determined effective friction angle via triaxial testing (36°).Item Open Access Forecasting groundwater contaminant plume development using statistical and machine learning methods(Colorado State University. Libraries, 2022) McConnnell, Elizabeth, author; Blotevogel, Jens, advisor; Karimi Askarani, Kayvan, committee member; Ham, Jay, committee member; Scalia, Joseph, committee memberA persistent challenge in predicting the fate and transport of groundwater contaminants is the inherent geologic heterogeneity of the subsurface. Contaminant movement has been primarily modeled by simplifying the geology and accepting assumptions to solve the advection- dispersion-reaction equation. With the large groundwater quality datasets that have been collected for decades at legacy contaminated sites, there is an emerging potential to use data- driven machine learning algorithms to model contaminant plume development and improve site management. However, spatial and temporal data density and quality requirements for accurate plume forecasting have yet to be determined. In this study, extensive historical datasets from groundwater monitoring well samples were initially used with the intent to increase our understanding of complex interrelations between groundwater quality parameters and to build a suitable model for estimating the time to site closure. After correlation analyses applied to the entire datasets did not reveal compelling correlation coefficients, likely due to poor data quality from integrated well samples, the initial task was reversed to determine how many data are needed for accurate groundwater plume forecasting. A reactive transport model for a focus area downgradient of a zero-valent iron permeable reactive barrier was developed to generate a detailed, synthetic carbon tetrachloride concentration dataset that was input to two forecasting models, Prophet and the damped Holt's method. By increasing the temporal sampling schedule from the industry norm of quarterly to monthly, the plume development forecasts improved such that times to site closure were accurately predicted. For wells with declining contaminant concentrations, the damped Holt's method achieved more accurate forecasts than Prophet. However, only Prophet allows for the inclusion of exogenous regressors such as temporal concentration changes in upgradient wells, enabling the predictions of future declining trends in wells with still increasing contaminant concentrations. The value of machine learning models for contaminant fate and transport prediction is increasingly apparent, but changes in groundwater sampling will be required to take full advantage of data-driven contaminant plume forecasting. As the quantity and quality of data collection increases, aided by sensors and automated sampling, these tools will become an integral part of contaminated site management. Spatial high-resolution data, for instance from multi-level samplers, have previously transformed our understanding of contaminant fate and transport in the subsurface, and improved our ability to manage sites. The collection of temporal high-resolution data will similarly revolutionize our ability to forecast contaminant plume behavior.Item Open Access Hydrological assessment of field-scale GeoWaste and waste rock test piles(Colorado State University. Libraries, 2020) Hassanzadeh Gorakhki, Mohammad Reza, author; Bareither, Christopher, advisor; Shackelford, Charles, committee member; Scalia, Joseph, committee member; Heyliger, Paul, committee member; Butters, Greg, committee memberMine waste rock and mine tailings are generated in substantial quantities an d must be managed to protect human health and the environment. Challenges in mine waste management facilities include geotechnical stability, environmental contamination, water management, and post operation (long term) closure. Waste rock and tailings co-disposal is a management technique that can address many of the aforementioned challenges. GeoWaste is a mixture of fast-filtered tailings and waste rock blended to isolate waste rock particles within a tailings-dominated matrix. A field-scale experiment that included a waste rock pile and GeoWaste pile was conducted at a mine in Central America to evaluate if GeoWaste suppresses sulfide oxidation and production of metal-rich acid rock drainage relative to waste rock. The objectives of this study were to (i) evaluate hydrologic performance of the piles, (ii) conduct in situ infiltration tests on the piles, (iii) determine field-scale hydraulic parameters for GeoWaste and waste rock, and (iv) develop numerical models to predict water content and oxygen concentrations within the piles. Water content, temperature, electrical conductivity, and oxygen concentration within the piles were monitored for 26 months. Sealed double ring infiltrometer tests were conducted at the end of the pile experiment and test pile subsequently were excavated to assess the spatial distribution in geotechnical characteristics. Inverse modeling was completed in HYDRUS-2D based on infiltration data to determine hydraulic conductivity and moisture retention parameters for the test piles. Field- and laboratory-scale hydraulic parameters were used in HYDRUS-1D and HYDRUS-2D to develop seepage models to predict moisture movement during the 26-month pile experiment. Oxygen concentration was predicted for the GeoWaste pile in HYDRUS-1D via the solute transport module, Fick's 2nd law, the oxygen consumption rate, oxygen diffusion in gas and water phases, and Henry's constant.Item Open Access Mechanistic visco-elastic modeling of shear deformation and failure in internally-reinforced geosynthetic clay liners(Colorado State University. Libraries, 2022) Baukus, Aaron, author; Bareither, Christopher A., advisor; Scalia, Joseph, committee member; Yourdkhani, Mostafa, committee memberAnalysis and prediction of the shear behavior of a non-heat-treated needle punched geosynthetic clay liner (NHT NP GCL) have been conducted using a mechanistic model. A three-element Kelvin-chain model was employed to simulate the incremental loading of a rapid loading shear test. A performance analysis initially was conducted to evaluate variation in model parameters with respect to differences in physical properties of GCLs (i.e., peel strength) and experimental conditions (i.e., normal stress, temperature, creep shear stress). The optimized model parameters demonstrated sensitivity to the variation in internal and external factors and yielded empirical relationships that were carried forward to test model applicability for predicting time-to-failure for an internally-reinforced GCL. These data trends in combination with creep-test data were used to calibrate the creep deformation model. Time-to-failure predictions performed with the calibrated creep deformation model resulted in a percent error < 9%. A modified model-calibration procedure was developed to extend model applicability to stress conditions common in practice. The modified calibration procedure was used to predict NHT NP GCL creep deformation in a hypothetical landfill cover system. The time required for the projected deformation to surpass 3 mm exceeded one million years for all stress conditions evaluated, which suggested that the NHT NP GCL will not experience creep failure in the low-stress cover scenarios evaluated.Item Open Access Shear behavior of geosynthetic clay liners and textured geomembranes in mining applications(Colorado State University. Libraries, 2019) Ghazi Zadeh, Shahin, author; Bareither, Christopher A., advisor; Shackelford, Charles D., committee member; Scalia, Joseph, committee member; Bailey, Travis, committee memberThe objective of this study was to evaluate the shear behavior of a composite system consisting of geosynthetic clay liner (GCL) and textured geomembrane (GMX) in mining applications. In current practice, design of liner and cover systems for waste containment is based on results of displacement-controlled internal and interface shear tests, which commonly include GCL and GMX specimens hydrated in de-ionized or tap water and tested at room temperature (e.g., 20 °C). However, the use of GCL/GMX composite systems in liner and/or cover systems for mine waste containment (e.g., heap leach pads, tailings impoundments, waste rock piles) may be exposed to physical and environmental stresses that are not conventionally replicated in laboratory testing, such as high shear and normal stresses, elevated temperature, and/or non-standard solutions. Laboratory testing conducted under conventional experimental conditions may not represent appropriate stresses anticipated in field conditions. To address the aforementioned concerns and aid the design of liner and cover systems for mining applications, four main objectives were defined: (i) assess variability of internal reinforcement fibers and shear strength in GCLs; (ii) evaluate the effect of GCL and GMX characteristics on shear behavior of GCL/GMX composite systems; (iii) evaluate temperature effects on the shear behavior of GCL/GMX composite systems; and (iv) evaluation the effects of non-standard solutions on GCL internal and GCL/GMX interface shear strength. These objectives were addressed via laboratory experiments, which included approximately 400 direct shear tests, 150 peel strength tests, and 50 swell index tests. Comparable internal shear behavior was observed between 300 mm x 300 mm GCL specimens and 150 mm x 150 mm GCL specimens. Similar variability in peak internal shear strength was also observed in both size GCL specimens. Variation was also observed in GCL peel strength among specimens obtained from the same production roll. Variability in internal shear strength and peel strength were attributed to the spatial variability of reinforcement fiber characteristics within a given GCL roll. The failure mode of a GCL/GMX composite system in an interface direct shear test was a function of shearing normal stress and characteristics of the GCLs and GMXs. An increase in spike density of a GMX increased the critical strength of GCL/GMX composites at all normal stress. However, an increase in GCL peel strength most effectively increased critical strength of a GCL/GMX composite at high normal stresses when GCL internal failure occurred. Internal and interface direct shear testing at an elevated temperature to 80 °C resulted in reductions of both GCL internal and GCL/GMX interface shear strength. The reduction in GCL internal shear strength was due to a reduction in tensile strength of reinforcement fibers and reduction in the strength of the connection between reinforcement fibers and geotextile of the GCL. The reduction in GCL/GMX interface shear strength was attributed to a reduction in the interlocking strength between GMX spikes and fibers of the geotextile of the GCL, as well as a reduction in geotextile-GMX interface friction. Hydration of GCL and GMX specimens up to 10 months in synthetic acidic and alkaline mining process solutions did not produce noteworthy change in GCL internal shear strength, GCL-GMX interface shear strength, or GCL peel strength. However, stiffer shear behavior was observed in internal and interface shear tests on GCL and GMX specimens hydrated with the synthetic acidic mine process solution. Hydration with the synthetic acidic mine process solution reduced swell behavior of sodium bentonite, whereas no conclusions were made regarding the effect of hydration with alkaline mine process solution on bentonite swell behavior.Item Open Access Thermal monitoring of natural source zone depletion(Colorado State University. Libraries, 2019) Karimi Askarani, Kayvan, author; Sale, Thomas, advisor; Ham, Jay, committee member; Scalia, Joseph, committee member; Bailey, Ryan, committee memberNatural Source Zone Depletion (NSZD) has emerged as a viable remedial approach for mature releases of petroleum liquids in soils and groundwater. Herein, petroleum liquids in soils and groundwater are referred to as LNAPL. In recent years, gradient, dynamic chamber, and carbon trap methods have been developed to quantify NSZD rates based on measuring the consumption of O2 or the generation of CO2 associated with biodegradation of LNAPL. A promising alternative approach to resolving LNAPL NSZD rates is real-time monitoring of subsurface temperatures. Transformation of temperature data to NSZD rates involves use of background-corrected temperature data, energy balances to resolve NSZD energy, and an estimate of heat produced through NSZD. All current computational methods for quantifying NSZD rates using temperature data have the drawbacks of: 1) incomplete energy balances 2) ignoring the effect of water table fluctuation, and 3) using linear extrapolations of temperature profiles to calculate thermal gradients. A regression algorithm is advanced to overcome the primary drawbacks of current computational methods that convert subsurface temperature data to NSZD rates using background correction. The regression algorithm is demonstrated using 42 million temperature measurements from a fuel terminal. An 8% difference between NSZD rates from the CO2 Trap method and the regression algorithm supported the validity of regression algorithm for estimation of NSZD rates using subsurface temperatures. In addition, seasonal behavior of NSZD rates is captured and correlated water content in shallow soils and depth to the water table. It is concluded that as the water table rises, the apparent NSZD rates increase, while larger water content in shallow soil causes a reduction in the apparent NSZD rates. Imperfection with background-correction approaches can be attributed to many factors, including differing infiltration of precipitation, vegetative cover, soil properties, and net solar radiation, at background versus impacted locations. Differences between the background location and the impacted area cause anomalous background-corrected temperatures leading to over/under estimation of NSZD rates. A new computational model is developed to eliminate the need for background correction of temperature data in calculating NSZD rates. Since the new model uses only the temperature data collected from the temperature sensors attached to a single solid stick, the model is referred to as the "single stick" method. The validity of the single stick model is evaluated using a numerical model and field temperature data. Agreement between the results from a numerical model with imposed heat fluxes, and estimated heat fluxes using temperature data derived from the numerical model, supports the validity of single stick model. In addition, a close match between single stick simulated temperatures using estimated heat fluxes and actual measure temperatures supports the validity of the single stick model. Furthermore, comparison of NSZD rates from the single stick model with the rates from background correction methods at background locations shows that the single stick model is the only algorithm that consistently provides near zero NSZD rates in clean areas. Lastly, per thermodynamic calculations and preliminary lab studies, it is observed that negative NSZD rates may be due to endothermic methanogenic process. Thermal conductivity is one of the key input parameters for all computational methods converting temperature data to NSZD rates. An integrated Internet of Things (IoT) instrument and computational model is developed to measure real-time in-situ thermal conductivity of soils. Favorable agreement between measure ex-situ and in-situ thermal conductivities values supports the validity of the demonstrated in-situ techniques for estimating thermal conductivities. Favorable attributes of the new in-situ methods include lower cost, automated data acquisition and an ability to acquire in-situ estimates of thermal conductivities through time. Overall, this work demonstrated that monitoring subsurface temperature is a viable technique to resolve NSZD rates for LNAPLs. A promising next step for evaluating the validity of thermal NSZD rates is to periodically collect and analyze cryogenic cores from field sites to independently validate NSZD rates. Also, further work is needed to better resolve NSZD thermodynamics.Item Embargo Tools for characterizing and monitoring natural source zone depletion(Colorado State University. Libraries, 2024) Irianni Renno, Maria, author; De Long, Susan K., advisor; Sale, Thomas C., advisor; Key, Trent A., committee member; Scalia, Joseph, committee member; Stromberger, Mary, committee memberAlthough natural source zone depletion (NSZD) has gained acceptance by practitioners as a remediation technology for mid- to late-stage sites containing light non-aqueous phase liquids (LNAPL), challenges remain for broader regulatory adoption of NSZD as the sole remedy. Adoption of NSZD as a remedy requires verifying that it is occurring. NSZD can be an efficient and cost-effective solution for LNAPL zones, but acceptance of this bioremediation technology relies on a multiple-lines-of-evidence approach that requires a solid understanding of baseline conditions and effective monitoring. Emerging use of in situ oxidation-reduction potential (ORP) sensors shows promise to resolve spatial and temporal redox dynamics during NSZD processes. Further, next generation sequencing (NGS) of present and active microbial communities can provide insights regarding subsurface biogeochemistry, associated elemental cycling utilized in electron transport (e.g., N, Mn, Fe, S), and the potential for biodegradation. Microbially-mediated hydrocarbon degradation is well documented. However, how these microbial processes occur in complex subsurface petroleum impacted systems remains unclear, and this knowledge is needed to guide technologies to enhance biodegradation effectively. Analysis of RNA derived from soils impacted by petroleum liquids allows for analysis of active microbial communities, and a deeper understanding of the dynamic biochemistry occurring during site remediation. However, RNA analysis in soils impacted with petroleum liquids is challenging due to: 1) RNA being inherently unstable, and 2) petroleum impacted soils containing problematic levels of polymerase chain reaction (PCR) inhibitors (e.g., aqueous phase metals and humic acids) that must be removed to yield high-purity RNA for downstream analysis. Herein, a new RNA purification method that allows for extracting RNA from petroleum impacted soils was developed and successfully implemented to discriminate between active (RNA) and present (DNA) microbes in soils containing LNAPL. A key modification involved reformulation of the sample pretreatment solution by replacing water as the diluent with a commercially available RNA preservation solution consisting of LifeGuard™ (Qiagen) Methods were developed and demonstrated using cryogenically preserved soils from three former petroleum refineries. Results showed the new soil washing approach had no adverse effects on RNA recovery but did improve RNA quality by removing PCR inhibitors, which in turn allows for characterization of active microbial communities present in petroleum impacted soils. To optimally employ NSZD and enhanced NSZD (ENSZD) at sites impacted by LNAPL, monitoring strategies are required. Emerging use of subsurface Soil redox sensors shows promise for tracking redox evolution, which reflects ongoing biogeochemical processes. However, further understanding of how soil redox dynamics relate to subsurface microbial activity and LNAPL biodegradation pathways is needed. In this work, soil redox sensors and DNA and RNA sequencing-based microbiome analysis were combined to elucidate NSZD and ENSZD (biostimulation via periodic sulfate addition and air sparging) processes in columns containing LNAPL impacted soils from a former petroleum refinery. Herein, microbial activity was directly correlated to continuous soil-ORP readings. Results show expected relationships between continuous soil redox and active microbial communities. Continuous data revealed spatial and temporal detail that informed interpretation of the hydrocarbon biodegradation data. Redox increases were transient for sulfate addition, and DNA and RNA sequencing revealed how hydrocarbon concentration and composition impacted microbiome structure and naphthalene biodegradation. When alkanes were present, naphthalene degradation was not observed, likely because naphthalene degraders were outcompeted. Further, the results of the sulfate addition experiment indicated a direct correlation of Desulfovibrio spp. with naphthalene biodegradation and showed that Smithella spp. were enriched in sulfate enhanced soils containing alkanes. Periodic air sparging did not result in fully aerobic conditions suggesting observed increased rates of biodegradation could be explained by stimulating alternative anaerobic metabolisms that were more energetically favorable compared to baseline/control conditions (e.g., iron reduction due to air oxidizing reduced iron). Methods developed and emerging continuous monitoring tools that were tested in lab soil columns were also applied to a mid- and late-stage LNAPL site. Herein, a case study is presented that advances integration of multiple nascent technologies for characterizing mid- and late-stage LNAPL sites including: 1) cryogenic coring, 2) multiple level internet of things (IoT) soil redox and temperature sensors in soil, and 3) application of RNA- and DNA-based molecular biological tools (MBTs) for site characterization. The integration of the data sets produced by these tools allowed for progress of NSZD to be evaluated in parallel under LNAPL site-relevant biogeochemical conditions. Collectively, the research presented in this dissertation support combining cryogenic coring sampling, continuous redox and temperature sensing and microbiome analysis to provide insights beyond those possible with each monitoring tool alone. The synergy achieved between microbiome characterization and soil continuous sensing illustrates how the integration of new characterization tools can provide insight into complex biogeochemical systems. Further understanding of these technologies will lead to improved predictions on remediation outcomes. The modern tools tested for middle- and late-stage LNAPL sites offer opportunities to more effectively and efficiently manage legacy LNAPL sites.Item Open Access Undrained shear behavior and critical state analysis of mixed mine waste rock and tailings(Colorado State University. Libraries, 2019) Borja Castillo, Raquel N., author; Bareither, Christopher A., advisor; Scalia, Joseph, committee member; Gallen, Sean, committee memberThe objectives of this study were to (i) evaluate the undrained shear behavior of mine tailings and a tailings-dominated mixture of filtered tailings and waste rock (i.e. GeoWaste), (ii) identify the critical state of each material, and (iii) assess the impact of waste rock inclusions on the critical state of tailings. Mine tailings and waste rock were collected from an active mine where GeoWaste is being considered as a potential solution for mine waste management. GeoWaste was prepared at a mixture of 1.2 parts waste rock to 1 part tailings, by dry mass, which was a relevant mixture ratio for field implementation. Consolidated undrained (CU) triaxial compression tests were conducted on pure tailings and GeoWaste. Large-scale triaxial compression tests were conducted on 150-mm-diameter GeoWaste specimens, and 38-mm-diameter triaxial tests were conducted on tailings prepared to three initial conditions: filtered tailings that represented field conditions, dense filtered tailings, and paste tailings. Triaxial compression tests were conducted at effective confining pressures (σc') ranging between 20 and 500 kPa. Filtered tailings prepared to represent field conditions yielded contractive, strain-hardening behavior. Dense filtered tailings exhibited strain-hardening behavior, net positive pore pressure, and a transition from contractive to dilative tendencies. Paste tailings exhibited modest strain-hardening behavior. GeoWaste exhibited strain-hardening, contractive behavior, and a modest transition from contractive to dilative behavior was observed at σ'c = 500 kPa. The undrained shear behavior of GeoWaste was comparable to filtered tailings at σ'c = 50 kPa and 100 kPa. However, undrained shear behavior of GeoWaste at σʹc = 500 kPa changed related to tailings, which was characterized by a larger deviator stress and lower excess pore pressure. This GeoWaste behavior indicated improved shear resistance compared to filtered tailings, which was attributed to (i) inter-particle reinforcing effects between the waste rock particles within a tailings-dominated structure and (ii) densification of the GeoWaste structure. Shear strength parameters were calculated from the slope of a composite Kf Line for each material. Filtered tailings prepared to represent field conditions, and dense filtered tailings yielded effective tangent friction angle (φ't) = 33°, and paste tailings yielded φ't = 32°. Similarity in φ't between the three tailings prepared with different initial specimen characteristics was attributed to similar void ratios at the end of consolidation under a given σʹc. GeoWaste yielded φ't = 32°. Although composite φ't were similar between tailings and GeoWaste, the secant friction angles of GeoWaste increased with increasing σʹc, whereas the opposite trend was observed for tailings. The addition of waste rock particles to tailings in a fine-dominated structure to increase the shear resistance relative to tailings as effective consolidation stress increased. An assessment was conducted between the critical state lines for tailings and GeoWaste to determine if the critical state line for tailings can represent critical state conditions in GeoWaste. An equivalent tailings void ratio (e*t) that can represent the tailings fraction within GeoWaste correlated with the critical state line for tailings. In this study, the e*t for GeoWaste was determined via optimizing a fitting parameter in the e*t equation to correlated with the critical state line for tailings. Although this evaluation suggests that the critical state line for the tailings can be used to represent critical state conditions in GeoWaste, additional work is needed to determine e*t a priori.