Browsing by Author "Scalia, Joseph, IV, committee member"
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Item Open Access Assessing groundwater storage and groundwater level fluctuations in the area of Fort Collins, Colorado(Colorado State University. Libraries, 2018) Almahawis, Mohammed, author; Bailey, Ryan T., advisor; Scalia, Joseph, IV, committee member; Sanford, William E., committee memberAlthough groundwater is the main water supply for many municipalities worldwide, shallow groundwater can adversely affect urban areas via soil waterlogging and impacts on building foundations and general city infrastructure. A quantitative assessment of groundwater levels and temporal fluctuations is needed to determine the extent to which groundwater should be managed to prevent these adverse conditions. This thesis assesses past and current groundwater storage and groundwater levels in the city limits of Fort Collins, Colorado, a moderate-sized municipality situated in the Front Range of the Rocky Mountains in the western United States. Currently, Fort Collins uses only surface water for its water supply, with the underlying unconfined alluvial aquifer mostly unused and close to ground surface. The assessment includes developing quantitative groundwater maps (depth to water table, water table elevation, and saturated thickness), estimating groundwater recharge and change in storage during large rainfall events, and defining areas with risk of high groundwater level. Observed depth to water table data from various sources was collected for two-time frames (1959-1979 and 2000-2017). The Stanford Geostatistical Modeling Software (SGeMS) was used to interpolate soil and groundwater data, and a Geographic Information System (GIS) was used to develop maps, estimate the storage, and define areas with potential risk of high groundwater level. Also, the Natural Resources Conservation Service's (NRCS) curve number method was performed to quantify recharge from high-intensity rainfall events. NRCS curve number method is a widely used method to quantify the amount of runoff due to a rainfall event. Comparing results from the two-time frames, the depth to water table in the study area has increased slightly (0.32 m) with a 3.9 m current average depth to the water table. Storage has decreased from 126.8 million m3 to 122 million m3, largely due to pumping groundwater for irrigation in the northeast area of the city limits. Approximately 10% of parcels in the Fort Collins area are at risk of high groundwater level. Most parcels along the Cache La Poudre River have problems with high groundwater level. The amount of recharge to the shallow aquifer in the Fort Collins area due to 10 and 100-year return-period storms is approximately equal to 1.9 million m3 and 3.3 million m3, respectively. Also, the percentage of the parcels at risk of high groundwater table will increase to 11% and 12%, respectively. The resulting groundwater maps, and the response of water table to rainfall events, can assist city water managers with identifying areas of potential risk to shallow groundwater conditions. In addition, the methods applied in this thesis can be used for other urban areas containing a shallow alluvial aquifer.Item Open Access Hydrologic comparison of prescriptive and water balance covers(Colorado State University. Libraries, 2018) Stock, Caleb Swenson, author; Bareither, Christopher A., advisor; Scalia, Joseph, IV, committee member; Paschke, Mark W., committee memberThe objective of this study was to compare the water balance of prescriptive and water balance cover (WBC) designs for Larimer County Landfill (LCL) via hydrologic modeling. A prescriptive cover is designed to limit percolation into underlying waste via a low permeability layer, whereas a WBC is designed to limit percolation via storing infiltrated precipitation and subsequently releasing the water through evaporation and transpiration. Guidance on WBC designs in Colorado are based on geographical location of the site and particle-size distribution of the available cover soils. Soil characteristics and engineering properties were determined from exhumed samples for a completed closure phase of LCL (Phase 1) and two borrow areas (Borrow Area 3 and Borrow Area 4). Hydrologic modeling was completed using VADOSE/W to predict the percolation rate through the prescriptive and water balance covers. The wettest ten consecutive years on record with a sufficiently complete meteorological data set (1992-2002) were selected for the analysis. Vegetation parameters were assigned to represent the revegetated state observed in Phase 1 and the natural conditions observed in the borrow areas. Predicted percolation through a prescriptive cover was < 0.1 to 2.2 mm/yr, depending on assumed saturated hydraulic conductivity. Evaporation was the primary process for removing water from the prescriptive cover models. Predicted percolation through the WBC models ranged from 6.3 to 11.3 mm/yr depending on the borrow area soil and vegetation parameters. Transpiration was the primary process for removing water from the WBC models. Within all of the regulatory acceptable cover models' evapotranspiration removed 94 to 102% of the precipitation received during the ten years modeled. Results of this study indicate that either a prescriptive cover with a total thickness of 106.7 cm (3.5 ft) or a WBC with a thickness of 76.2 cm (2.5 ft) will meet regulations for final closure cover at LCL.Item Open Access Laboratory evaluation of a post-fire ground treatment to mitigate soil erosion and runoff(Colorado State University. Libraries, 2018) Moden, Kayla Nicole, author; Bareither, Christopher A., advisor; Scalia, Joseph, IV, committee member; Stevens-Rumann, Camille S., committee memberThe objective of this study was to assess the efficacy of using agricultural straw mulch as a post-fire ground treatment to mitigate soil erosion and runoff. A laboratory research program was carried out to measure soil erosion and runoff in a physical slope-model experiment (surface dimensions = 76 cm long x 30 cm wide). Intact block samples were collected that represented conditions in Colorado wildfire prone areas. The vegetation on select block samples was burned to simulate a high-intensity wildfire. Unburned block samples with varying amounts of vegetation and burned block samples with varying amounts of straw mulch (0, 0.06, 0.11, and 0.22 kg/m2) were tested in the slope-model experiment at a slope of 28o under a simulated rainfall of 48 mm/h for 40 min. Burned block samples were exposed to two rainfall simulations conducted three days apart to explore changes in soil hydraulic properties due to potential soil crust formation. Runoff, and eroded sediment were collected during simulated rainfall, and intact subsamples were collected from unburned and burned block samples after the rainfall simulations to evaluate the effects of high severity burning on physical characteristics and hydraulic and mechanical properties (i.e., dry density, total organic carbon, hydraulic conductivity, water repellency, and shear strength). Burning exponentially increased erosion compared to unburned conditions and all rates of straw mulch reduced soil erosion to levels consistent with unburned samples. Runoff and erosion increased with a decrease in natural surface vegetation on unburned samples and increased with a decrease in straw mulch applied to burned samples. Notable changes in geotechnical properties with high severity burning were not found in this study, which suggested that the observed increase in erosion on bare burned samples during rainfall simulations was attributed to destruction of surface cover with burning.Item Open Access Predicting water content and saturation in mine tailings with an electromagnetic soil moisture sensor(Colorado State University. Libraries, 2023) Martin, Garret M., author; Bareither, Christopher A., advisor; Scalia, Joseph, IV, committee member; Ham, Jay M., committee memberThe degree of saturation of mine tailings plays an important role in geotechnical and geochemical stability of a tailings facility, and as such, reliable measurements of in situ tailings saturation aid in evaluating the stability of a tailings facility. However, measuring in situ saturation in tailings facilities is a common challenge in the tailings industry. The objectives of this study were to (1) evaluate the ability of an electromagnetic soil moisture sensor to predict the volumetric water content and degree of saturation of mine tailings and (2) conduct proof-of-concept tests to assess the potential for electromagnetic sensors to be used as a tool in tailings engineering practice. To meet these objectives, laboratory-scale testing was conducted using an electromagnetic soil moisture sensor embedded in moist-tamped and slurry-deposited specimens of a single hardrock mine tailings prepared at varying volumetric water content, degree of saturation, and dry density. Certain specimens were subjected to changes in mass-volume properties and sensor performance was evaluated for timeliness and accuracy of response. The results of this study indicate an electromagnetic soil moisture sensor can be used to predict the volumetric water content and degree of saturation in hardrock mine tailings with a useful degree of accuracy depending on the application and precision required. During the proof of concept tests performed, error in predicted volumetric water content was less than about 1.5% to 3.8%, error in predicted saturation was predominantly less than 5%, and temporal response to changes in moisture was equivalent to a sensor insertion rate of approximately 27 mm/s. Based on the findings of this study, electromagnetic sensor technology offers a viable tool to predict the degree of saturation within tailings facilities and can be incorporated into innovative approaches to address the challenges encountered in different types of tailings facilities.Item Open Access Rift to drift transition in the southwest Australian deepwater Mentelle Basin(Colorado State University. Libraries, 2021) Guerzon, Emmanuel, author; Harry, Dennis, advisor; Stright, Lisa, committee member; Scalia, Joseph, IV, committee memberThe Mentelle Basin is a deepwater polyphase basin located off of the southwest margin of Australia that formed during Late Jurassic and Early Cretaceous breakup of Gondwana. It is underlain by highly extended continental crust and is bordered to the west by less extended crust forming the Naturaliste Plateau, and to the east by the Yalingup Shelf and Perth Basin beneath the continental shelf and coastal plain. The purpose of this study is to characterize the depositional, subsidence, and tectonic histories of the Mentelle Basin during the syn-rift to post-rift transition period. We use seismic reflection data and boreholes drilled by the Deep Sea Drilling Project and International Ocean Discovery Program (IODP) to map three horizons and intermittent volcanic features within this > 134 Ma to 126 Ma period. The youngest horizon mapped was the top of Lithostratigraphic Unit 5 (LSU5) at IODP Site U1513, which corresponds with the lower Aptian age (126 Ma) when rifting on this part of the margin ended and seafloor spreading began between Greater India and Australia west of the Naturaliste Plateau. Also mapped was a reflector encountered at the top of the basalt pile in IODP Hole U1513D at the western edge of the Mentelle Basin. The oldest horizon mapped is the Valanginian Unconformity that lies below this basalt pile and corresponds with breakup and the onset of seafloor spreading on the Perth Abyssal Plain further north. Isochore maps and two depth structure maps generated from these horizons illustrate the subsidence history and structural and magmatic evolution of the Mentelle Basin during breakup. Syn-rift magmatism in the Mentelle Basin was more widespread than previously thought. While earlier studies deemed the western half of the Mentelle Basin magmatic, the eastern extent of magmatism was unknown. Seismic correlation of the basalt reflector at Site U1513 indicates the Naturaliste Plateau basalts extended eastward to the eastern flank of the Mentelle Basin. Younger flows 2 – 20 km wide and occasional volcanic cones ranging from 0.5 – 2.5 km wide are imaged in the western half of the basin to the toe of the eastern slope. These younger volcanic features were emplaced between the late Valanginian through the start of the Aptian age. Basalt flows and some volcanic features in the basin are interpreted to have been exposed and weathered at or above sea level around the time of emplacement before subsequent burial by a marine transgression. The Mentelle Basin began to subside prior to the Naturaliste Plateau (> 134 Ma) as rifting occurred between India and Australia-Antarctica. Once final breakup occurred and seafloor spreading began west of the Naturaliste Plateau, both the Mentelle Basin and Naturaliste Plateau subsided to bathyal depths beginning around 126 Ma.Item Embargo Shear and consolidation behavior of slurry-deposited, desiccated tailings and compacted filtered tailings(Colorado State University. Libraries, 2024) Primus, Justin Michael, author; Bareither, Christopher A., advisor; Scalia, Joseph, IV, committee member; Stright, Lisa, committee memberThe objective of this study was to (i) evaluate and compare the undrained shear behavior and (ii) the consolidation behavior of slurry-deposited and desiccated tailings versus compacted filtered tailings. In general, the evaluation supports the hypothesis that desiccation and resaturation of a hard rock mine tailings yield higher peak undrained shear strengths relative to compacted filtered tailings when considering similar initial conditions (e.g., stress and density). The increase in undrained shear strength was attributed to the tailings fabric, which generated a stiffer response to loading and transitional behavior from contractive to dilative tendencies when sheared undrained. Consolidated undrained (CU) triaxial compression tests were conducted on 64-mm-diameter specimens that followed two different procedures. Slurry-deposited tailings were desiccated to a target void ratio and water content, resaturated, and tested in isotropic, consolidated, undrained axial compression. Filtered tailings specimens were prepared to similar initial void ratios as those measured on desiccated tailings specimens and tested in triaxial compression in the same manner. One-dimensional consolidation tests were also conducted on desiccated and filtered tailings specimens in a similar sequence. The desiccated and filtered tailings exhibited contractive, strain-hardening behavior in the triaxial tests and yielded effective stress friction angles of 29.1° for the desiccated tailings and 27.7° for the filtered tailings. Desiccated tailings samples showed a stiffer initial peak deviatoric stress and slower decreasing rate of change in stress relative to the filtered tailings. There was no indication of a difference in stiffness or brittleness between tailings preparation methods. The higher shear strength of the desiccated tailings was attributed to (i) more pronounced inter-particle reinforcing effects and (ii) densification from stress-history of desiccation. One-dimensional consolidation tests yielded a trend of increasing preconsolidation pressure with decreasing initial void ratio for both the desiccated and filtered tailings. There were slightly higher average compression and recompression indexes computed for the desiccated tailings relative to the filtered tailings, providing an indication of the different in the fabric behaviors.Item Open Access Undrained shear behavior of mixed mine waste rock and tailings(Colorado State University. Libraries, 2017) Hamade, Matteus M. P., author; Bareither, Christopher A., advisor; Scalia, Joseph, IV, committee member; Magloughlin, Jerry F., committee memberThe objective of this study was to evaluate the effect of variability in mixture ratio (R) and tailings composition on shear behavior and shear strength of mixed mine waste rock and tailings (WR&T). Crushed gravel was used as a synthetic waste rock (SWR), and mixtures of sand, silt, and clay were used to create two synthetic mine tailings: average synthetic tailings (AST) and fine synthetic tailings (FST). Mixtures of WR&T were prepared with varying R to represent coarse-dominated structures to fine-dominated structures, as well as R = Ropt, which represents an optimal mixture ratio where tailings "just fill" void space of the waste rock. Pure SWR, pure tailings, and WR&T mixtures containing AST and FST were tested in consolidated-undrained triaxial compression at target effective confining stresses (σʹc) of 10, 50, and 100 kPa. The SWR and WR&T triaxial specimens were 150 mm in diameter by 300 mm tall, whereas the AST and FST specimens were 38 mm in diameter by 76 mm tall. Dilative, strain-hardening behavior was observed for all triaxial tests on pure SWR, whereas contractive, strain-softening behavior was observed for all triaxial tests on pure FST. Triaxial tests on pure AST exhibited both dilative, strain-hardening behavior and contractive, strain-softening behavior; contractive behavior was observed for AST specimens that contained larger initial void ratios (e) after consolidation. Waste rock and tailings mixtures that had coarse- dominated structures exhibited comparable undrained shear behavior to pure SWR. Fine- dominated WR&T mixtures exhibited undrained shear behavior that was more similar to the pure tailings; however, the addition of waste rock to tailings was observed to mitigate some contractive behavior as the addition of waste rock to tailings increased the tendency of the WR&T mixtures to exhibit dilative response. Mixtures prepared to target Ropt exhibited dilative, strain-hardening behavior. An analysis of flow behavior indicated that the addition of waste rock to tailings to create WR&T mixtures improved flow behavior of pure tailings to a limited- or no- flow behavior that improves resistance against static liquefaction. Shear strength parameters for all materials were calculated based on stress paths in p'-q space reaching the failure line (Kf Line). Pure materials yielded effective tangent friction angle (φ't) of 38° for AST, 39° for FST, and 41° for SWR. The AST mixture with R ≈ Ropt yielded φ't = 48°, which was the largest φ't of all mixtures. Fine-dominated structures of AST (i.e., R < Ropt) yielded φ't = 44°. This increase in φ't relative to the pure AST was attributed to the additional frictional resistance between the silty-sand AST and the SWR. The FST WR&T mixtures were only fine-dominated structures as all specimens yielded R < Ropt. The effective stress friction angle increased from 32° for FST mixtures prepared at R = 1.7 to 38° for R = 2.5. The lower φ't for the FST mixtures relative to the pure FST was attributed to looser tailings (i.e., higher void ratio) compared to the pure tailings specimens. A steady-state analysis was performed with the assistance of mixture theory to determine if a single steady state line (SSL) could be relevant for WR&T mixtures that was independent of mixture ratio. Results showed that the use of equivalent void ratios for the steady-state analysis of mixtures provide a reasonable prediction of undrained shear behavior of mixtures. The analysis on AST mixtures demonstrates the effectiveness of equivalent void ratios both for fine- and coarse-dominated structures. The FST mixtures also supports the effectiveness of fine-dominated equivalent void ratios for assessing undrained shear behavior of mixtures. The steady state analysis supports the use of a single SSL for mixtures based on pure tailings and the use of equivalent void ratios that are both independent of R.