Electronic Theses and Dissertations (2010 - Present)
Permanent URI for this communityhttps://hdl.handle.net/10657/1
The University of Houston Libraries collect and make publicly available all electronic theses and dissertations (ETDs) produced in UH graduate and PhD programs through the UH institutional repository. ETDs become available after the student submits them to the UH Graduate School, the document is approved by all appropriate parties, and any embargo on the document expires.
Collection Scope
UH Libraries began publishing ETDs from several UH Colleges in 2010. As of Summer 2014, all UH Colleges that require a thesis or dissertation for graduation began submitting these documents in electronic format. Below is a list of UH Colleges that currently participate in the ETD program and their coverage dates in this repository.
UH College | Coverage Dates |
---|---|
C.T. Bauer College of Business | 2010-Present |
Cullen College of Engineering | 2012-Present |
Conrad N. Hilton College of Hotel and Restaurant Management | 2015-Present |
College of Education | 2010-Present |
College of Liberal Arts and Social Sciences | 2012-Present |
College of Natural Sciences and Mathematics | 2012-Present |
College of Optometry | 2010-Present |
College of Pharmacy | 2010-Present |
College of Technology | 2012-Present |
K. G. McGovern College of the Arts | 2016-Present |
G. D. Hines College of Architecture & Design | 2016-Present |
Graduate College of Social Work | 2012-Present |
Additional Information
- Online access for content outside these coverage dates may be available electronically through ProQuest.
Note: As of Fall 2017, all theses and dissertations produced at UH will be submitted to ProQuest. Additionally, some UH Colleges have contributed content to ProQuest at different periods of time in the past. - For print theses and dissertations found outside these coverage dates, please consult UH Libraries’ catalog.
- Additional information on submitting ETDs can be found at the UH Graduate School.
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Browsing Electronic Theses and Dissertations (2010 - Present) by Department "Civil and Environmental Engineering, Department of"
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Item A Scalable Variational Inequality-Based Formulation That Preserves Maximum Principles for Darcy Flow with Pressure-Dependent Viscosity(2017-08) Mapakshi, Nischalkarthik; Nakshatrala, Kalyana Babu; Willam, Kaspar J.; Vipulanandan, Cumaraswamy; Lim, Gino J.The overarching goal of this thesis is to present a robust and scalable finite element computational framework based on Variational inequalities (VI) which models nonlinear flow through heterogeneous and anisotropic porous media without violating discrete maximum principles (DMP) for pressure. VI is an optimization technique that places bounds on the numerical solutions of partial differential equations, and previous studies have shown that the VI approach can enforce DMP for linear and semi linear subsurface flow and transport problems. Herein, the same VI framework is extended to the nonlinear Modified Darcy flow (MDF) model which incorporates pressure dependent viscosity. Although it can be proven that the MDF model satisfies maximum principles, most finite element formulations, including the classical Galerkin formulation with Raviart-Thomas elements and the variational multi-scale formulation, will not adequately enforce the DMP if strong levels of anisotropy are present. Several representative reservoir problems with realistic parameters are presented, and both the algorithmic and parallel scalability of the proposed computational framework are studied.Item A Softened Membrane Model for UHPC (SMM-UHPC)(2023-12) Shahin, Noran; Kalliontzis, Dimitrios; Mo, Yi-Lung; Baxevanis, TheocharisUnderstanding the shear behavior of Ultra-High-Performance (UHPC) is crucial to prevent undesired responses that could be induced by diagonal shear cracks. Hence, the ability of analytical models to predict shear responses of UHPC members is of paramount importance. This issue is addressed in this thesis by utilizing the Softened Membrane Model (SMM). Since the SMM is a two-dimensional shear modeling framework developed for normal concrete, a parametric investigation was performed to assess its suitability for UHPC, namely SMM-UHPC. Through this assessment, a softening coefficient for the biaxial behavior of UHPC was derived and new constitutive laws were integrated into SMM. It was also found that the decomposition between biaxial and uniaxial strain fields, commonly used in SMM, may be of less significance for UHPC. Comparisons with shear panel tests were used to evaluate the accuracy of SMM-UHPC and quantify the significance of key model parameters. Combining analytical and experimental data, this thesis shows that statistical determination of the localization strain is key for predicting the shear behavior of UHPC.Item A Three-Dimensional Fully Nonlinear Model in Curvilinear Coordinates for Simulating Waves Interaction with a Bottom-Mounted or Partially-Submerged Fixed Cylindrical Structure(2016-05) Chen, Yu Hsiang; Wang, Keh-Han; Mo, Yi-Lung; Vipulanandan, Cumaraswamy; Mansour, Alaa M.; Qian, QinThis dissertation presents a three-dimensional fully nonlinear wave model developed to simulate solitary waves propagating in straight or curved channels and interactions bottom mounted or partially submerged structures. The three-dimensional Laplace equation and fully nonlinear boundary conditions are solved numerically by the finite difference method. In order to have the computational grids fit closely to the curved structural boundaries and the time varying free surface for numerical advantage, the transient three-dimensional curvilinear coordinate transformation technique is adopted to convert the original governing equation and boundary conditions in Cartesian coordinates into the curvilinear coordinate based formulations. The effects of grid size and time step on the accuracy and convergence of the present numerical model are examined and discussed by simulating a solitary wave freely propagating in a straight rectangular channel. Then, the feature of the curvilinear coordinate transformation is tested by modeling the case of a solitary wave propagating in a 180° curved channel. After comparing with the results obtained from the generalized Boussinesq (gB) two-equation model, this three-dimensional model can produce stable and accurate predictions on nonlinear waves propagation in a channel with irregular boundary. The present three-dimensional model is extended to solve the wave and structure interaction problems. One of the cases is a solitary wave impinging a bottom mounted and surface piercing vertical cylinder. The results obtained from the present three-dimensional model shows a reasonable agreement with the experimental measurements and those calculated from the gB model. The other case is a solitary wave interacting with a partially submerged and fixed floating cylinder. Laboratory tests for a solitary wave passing through a partially immersed and fixed floating cylinder were conducted to verify the present three-dimensional model performance. The numerical results of the present model match well with the experimental measurements. It is demonstrated through these comparisons that the present three-dimensional fully nonlinear wave model can provide reliable predictions on wave evolution and loading for a solitary wave interacting with selected cylindrical structures.Item Abrasion Prediction at Kayraktepe Sediment Bypass Tunnel in Turkey(2018-12) Yesil Ozden, Ayse; Wang, Keh-Han; Vipulanandan, Cumaraswamy; Qian, QinSediment accumulation in reservoirs is a challenging issue that concerns most of the reservoirs worldwide. Use of sediment bypass tunnels is one of the potential solutions to reduce sediments deposited in reservoirs. However, the sediment bypass tunnels could face major invert abrasion problems due to intense bedload sediment transportation. Three existing abrasion prediction models are introduced developed respectively by Ishibashi (1983), Sklar and Dietrich (2004), and Auel et al. (2015). Those models are applied to estimate the abrasion of the Kayraktepe sediment bypass tunnels in Turkey. The Ishibashi (1983) model results reveal some discrepancies when compared to laboratory data, which reflects that its grinding stress term gives much higher values than its particle impact term does. However, when examining the effect of particle impact term by neglecting the grinding stress, the model predicts consistent results. The model by Auel at al. (2015) demonstrates reasonable predictions in case of regulated abrasion coefficient values are used. The model of Sklar and Dietrich (2004) predicts the lowest abrasion value due to its development according to the subcritical flow conditions. In Kayraktepe dam, the flow condition in sediment bypass tunnels are supercritical flow, thus the Sklar and Dietrich (2004) model does not fit for abrasion estimation. Modifications are made to the Sklar and Dietrich (2004) model are the revised model shows great improvement on the abrasion prediction. It is concluded that the estimation of sediment transport rate using commonly adapted theoretical or empirical formulations tends to be predicted more than the real transport rate and results in the over-estimation of the abrasion rate. It is recommended to modify the formulations and equation coefficients with the inputs of the field data on laboratory measurements for bettering the abrasion prediction.Item Accelerated Alkali-Silica Reaction and Corrosion of Reinforcing Steel in Concrete: Application on Dry Casks(2016-08) Attar, Arezou; Gencturk, Bora E.; Willam, Kaspar J.; Vipulanandan, Cumaraswamy; Meen, James K.; Rodrigues, Debora F.The durability is one of the main reasons making concrete the most abundantly consumed material in the world after water. However, severe exposure conditions and improper or low quality mixture designs can cause physical and chemical changes in concrete which lead to deterioration and premature failure of the structure. This process is called aging. Two of the main aging mechanisms in reinforced concrete structures are corrosion and alkali-silica reaction (ASR). These two processes occur very slowly and to assess them in a short period of time, they need to be accelerated. Furthermore, these mechanisms are dependent on the geometry and boundary conditions of the structure. Therefore, research on these aging mechanisms is structure specific and depends on the scale of observation. This study proposes a method through addition of chemicals to the concrete mixture for accelerating aging that is applicable to both small- and large- specimens. The aging is accelerated through addition of sodium hydroxide to accelerate ASR and calcium chloride to the mixture to accelerate corrosion. The effect of the addition of these chemicals on both physical and mechanical properties of concrete was investigated through a series of destructive and non-destructive testing at the materials and structural levels. The results indicate that the addition of sodium hydroxide to the concrete mix, combined with the use of reactive aggregate and no fly ash, considerably accelerates ASR and crack propagation on the surface of the specimens. Similarly, the addition of calcium chloride effectively accelerates corrosion. To investigate the validity of the proposed approach at the structural level, a vertical concrete dry cask for storage of nuclear waste was chosen as the case study. In this case study, three 1/3-scale dry casks were subjected to accelerated ASR and corrosion with the addition of chemicals to the mixture and their effect was measured over eighteen months. Furthermore, the service life of the scaled down casks was estimated considering the real life conditions. This approach is expected to help researchers to better understand the long term behavior of reinforced concrete dry casks.Item Accelerating Computations for Oil and Gas Problems: Reduced Physical Modeling of Hydraulic Fracturing and High-Performance Computing for Fluid Flow in a Porous Medium(2020-08) Protasov, Innokentiy; Ballarini, Roberto; Dontsov, Egor; Sharma, Pradeep; Ehlig-Economides, Christine; Krakowiak, Konrad J.; Momen, MostafaThe mechanical modeling of hydraulic fractures is a mathematically complex problem involving the coupling between the equations that describe fracturing of and fluid flow through the porous rock, and fluid flow inside the fractures. Simulation of these physical processes can offer critical insights into practical design problems associated with hydraulic fracturing technology. However, exploration of the influence of the relatively large number of control variables defining the design space is limited by the available computational resources. Generally speaking, the computational time can become a bottleneck for practical usage of available hydraulic fracture simulators. Acknowledging this limitation, this thesis presents a series of combined analytical-computational models that enable efficient simulation of the propagation of multiple non-planar hydraulic fractures, within the context of hardware-conscious advanced numerical techniques. Hydraulic fracture simulations are often coupled with the fluid flow within the surrounding porous rock. This thesis realizes the need for computationally efficient porous media flow simulations that achieve a similar level of efficiency as the fast hydraulic fracturing models. Remarkable computational efficiency is achieved through the novel formulations of numerical techniques and the state-of-the-art computational methods: reduced-order modeling of the hydraulic fracturing, and the application of physical block solvers to the porous media flow.Item Active and Passive Sensor Fusion for Terrestrial Hyperspectral Image Shadow Detection and Restoration(2016-05) Hartzell, Preston J.; Glennie, Craig L.; Shrestha, Ramesh L.; Lee, Hyongki; Khan, Shuhab D.; Parrish, Christopher E.Acquisition of hyperspectral imagery (HSI) from cameras mounted on terrestrial platforms is a relatively recent development that enables spectral analysis of dominantly vertical structures such as geologic outcrops. Although solar shadowing is prevalent in terrestrial HSI due to the vertical scene geometry, automated shadow detection and restoration algorithms have not yet been applied to this technique. This dissertation investigates the fusion of terrestrial laser scanning (TLS) spatial information with terrestrial HSI for geometric shadow detection on a vertical outcrop and examines the contribution of radiometrically calibrated TLS intensity, which is resistant to the influence of solar shadowing, to HSI shadow restoration. The proposed method for shadow detection in the terrestrial HSI leverages an accurately georeferenced, high density point cloud acquired with a TLS sensor to geometrically solve for the presence of shadows in the fused HSI. In contrast to traditional methods applied to airborne imagery, the analysis requires a fully 3D mesh representation of the outcrop rather than a 2.5D surface model. The inclusion of radiometrically calibrated TLS intensity in several existing image shadow restoration techniques is examined, and a direct combination of the active TLS and passive HSI radiometric products proposed and evaluated. Qualitative assessment of the shadow detection results indicates pixel level accuracy, which is indirectly validated by shadow restoration improvements when sub-pixel shadow detection is used in lieu of single pixel detection. The inclusion of TLS intensity in existing shadow restoration algorithms was found to have a marginal positive influence on restoring shadow spectrum shape, while the proposed combination of TLS intensity with passive HSI spectra boosts restored shadow spectrum magnitude precision by up to 40%, and band correlation with respect to a truth image by up to 45% compared to existing methods. The findings demonstrate that sub-pixel shadow detection in terrestrial HSI can be achieved with geometric methods using standard TLS and HSI field collection practices, and the inclusion of TLS intensity can improve restored HSI spectral characteristics. Simulations incorporating multiple laser wavelengths suggest more robust and computationally efficient methods of combining active and passive spectral data for restoring shadow pixel spectra are possible.Item Adjustable Frequency Bandgap for Seismic Vibration Isolation of MRE-Based Metamaterial Foundations(2023-08) Shrestha, Priyanka; Mo, Yi-Lung; Shan, Xiaonan; Wang, JiajiAn earthquake is a non-preventable natural disaster that shakes the ground and vibrates the structure's foundation, eventually damaging the superstructure. These seismic waves are more frequent in some areas because of their geological variations. The seismic vibration caused by earthquakes can damage the structure, leaving it unrectifiable and unusable. Different types of seismic isolation are used underneath the structure to prevent the structure from seismic damage. Conventional seismic isolators will elongate the period of the superstructural system, and hence reduce the vibration response of the superstructure and prevent the structures from seismic damage and collapse. Although the conventional seismic isolation system has been used for several decades, it cannot prevent earthquake vibrations in the vertical direction. Recently researchers developed metamaterial-based seismic isolators, which can isolate seismic waves in both the horizontal and vertical directions. When the frequency of seismic waves falls into the frequency band gap of the designed metamaterial foundation, the seismic waves will be reflected and will not be able to transfer the vibrations to the superstructure. Since earthquakes have a wide range of frequencies, adaptable and tunable frequency band gap of metamaterials is desirable. Magnetorheological Elastomer (MRE)-based metamaterial foundation can change Young’s modulus and stiffness by applying magnetic field intensity. Tunable material properties can shift the frequency band gap of the MRE-based metamaterial foundation. This research focuses on developing MRE samples and applying MRE-based metamaterial foundations to seismic isolation systems. A uniaxial compression test was conducted to determine Young’s modulus of three types of MRE samples under the application of magnetic field. After the MRE materials were developed, a series of numerical simulations were performed in ABAQUS using a two-story framed structure with MRE-based metamaterial foundation. Three earthquake excitations, Bishop, Oroville, and Imperial Valley were used as the seismograms. The experimental result shows that the magnetic field affects Young’s modulus of the MRE. Similarly, the results of the numerical simulations show that the magnetic field affects the frequency band gap of the MRE-based metamaterial foundation. The frequency response function (FRF) results of conventional RC foundation and MRE-based foundation are compared, which shows the effectiveness of MRE-based foundation in vibration control by reducing the seismic vibration of a structure by 68.5%.Item Advanced SAR Interferometry Methods for Ground Displacement Estimation from Spaceborne and Airborne Platforms(2016-05) Cao, Ning; Lee, Hyongki; Shrestha, Ramesh L.; Glennie, Craig L.; Lu, Zhong; Jung, Hahn ChulInterferometric synthetic aperture radar (InSAR) is a powerful technique to monitor ground deformation phenomena, such as landslides, ground subsidence, seismological activities, and volcano dynamics. In this dissertation, two major problems of the current advanced InSAR techniques are described and corresponding approaches are proposed to solve them. Among various multitemporal InSAR techniques, persistent (or permanent) scatterer InSAR (PSInSAR) has been widely used in a variety of cases due to its high accuracy and resistance to temporal and spatial decorrelations. One major drawback of the PSInSAR technique is the low spatial density of PSs, especially over non-urban areas without man-made structures. A Phase-Decomposition-based PSInSAR (PD-PSInSAR) method is developed in this dissertation to improve the coherence and spatial density of measurement points by processing the distributed scatterer (DS) dominated by two or more scattering mechanisms. PD-PSInSAR performs eigendecomposition on the coherence matrix in order to estimate the phases corresponding to the different scattering mechanisms, and then implements these estimated phases in conventional PSInSAR process. An important procedure in DS interferometry is the phase triangulation (PT). In this study, the mathematical framework for PT algorithms is proposed. This dissertation introduces two modified PT algorithms and analyzes the mathematical relations between five different PT methods. The analysis shows that these five PT methods share very similar mathematical forms with different weight values. The proposed mathematical framework supports improved understanding and advanced estimation methods for the use of PT algorithms in DS interferometry. Another major drawback of traditional InSAR is that only the deformation along the line-of-sight (LOS) direction can be detected. In order to estimate the deformation in the along-track direction, a time-domain along-track SAR interferometry (TAI) technique is proposed. Compared with existing multiple-aperture SAR interferometry (MAI) methods, the proposed technique utilizes the full aperture to generate single-look complex images, and results in higher SNR and along-track resolution. In the last part of the dissertation, a case study of Slumgullion landslide is performed to demonstrate the potentials and challenges of airborne InSAR as well as the possible solutions to improve the precision of the derived deformation measurements.Item Amplitude and Phase InSAR Analysis of Large Landslide Datasets(2023-05-11) Voelker, Brandon; Milillo, Pietro; Glennie, Craig L.; Lee, HyongkiLandslides are common natural phenomena that can have catastrophic consequences, with significant economic, environmental, and social impacts worldwide. These events can occur in a matter of seconds or evolve over geologic timescales. As such, there is a growing need for reliable and effective techniques to monitor and assess landslides over different time intervals. One promising approach is the use of Synthetic Aperture Radar (SAR), which can penetrate through clouds and can operate day or night, making it an ideal tool for landslide detection and monitoring. In this thesis, we explore the use of SAR-based methodologies to observe landslides over various timescales, ranging from fast-moving (meters/second) to slow-moving (cm/year). To assess the effectiveness of SAR-based methodologies, we conducted several case studies using amplitude and phase-based SAR techniques. For instance, in the aftermath of a storm event in Hiroshima, Japan, and an earthquake followed by a storm in Haiti, we employed SAR intensity-based failure detection methods to locate landslides. Furthermore, we leveraged the processing power and catalog of satellite radar images from Google Earth Engine to develop an algorithm that detects landslides over multi-year periods, which we validated using optical imagery and the Normalized Difference Vegetation Index (NDVI). In addition to these case studies, we investigated the movement of slow-moving landslides in Western Oregon, a region prone to recurring landslide movements and long-term accelerating trends due to coastal erosion. We used ESA Sentinel-1 C-band (5.6 cm wavelength) multi-temporal interferometric SAR data and PRISM climate data from 2017–2021 to analyze the displacements of a large landslide inventory over time. We also explored the relationship between precipitation, landslide morphology, and deformation rates. Finally, we used NASA AirMOSS InSAR data acquired at P-band (70 cm wavelength) over several landslides and compared it to the shorter-wavelength Sentinel-1 C-band multi-temporal SAR data to assess the advantages and drawbacks of longer wavelengths sensors. Our findings highlight the potential of SAR-based methodologies to detect and monitor landslides over various time scales. This study offers valuable insights into the development of reliable and effective tools for landslide management, with practical applications for disaster response, urban planning, and risk assessment.Item An Automated and Remotely Operated Siphon System for Flood Control(2018-05) Yolcu, Ahmet Emirhan; Leon, Arturo S.; Wang, Keh-Han; Louie, Stacey M.The proposed siphon system aims to release water from a wetland before a heavy rainfall that is forecasted to produce flooding. The storage made available by the early release would provide water storage for the heavy rainfall; thus, mitigating flooding. The proposed siphon system can be operated remotely by an operator or automatically using a decision support system (DSS). In an actual implementation, flood managers would operate hundreds or thousands of siphons simultaneously. The proposed system does not require energy except for keeping the siphon pipes full of water and for sensor control/communication. For this small amount of energy, a solar-powered bilge pump is used. Overall, the proposed siphon system may help to mitigate flooding by allowing water release from wetlands and shallow ponds.Item An Evaluation of Image Correlation Techniques for Measuring Sand Dune Migration Rates from Remote Sensing Data(2019-05) Hall, Leah E.; Glennie, Craig L.; Telling, Jennifer; Hartzell, Preston J.; Siebach, Kirsten L.The surface migration rates of sand dunes both on Earth and on other planets provide important information about local and regional wind patterns. However, in situ data is often unavailable and remote sensing data must be applied to understand these environments. This study tested two software techniques, COSI-Corr and PIVLab, and evaluated their performance using high resolution imagery and airborne lidar covering White Sands, NM, Victoria Valley, Antarctica, and Jockey’s Ridge, NC. Mean migration rates were computed from the vector field data for overlapping vectors and residual vector values from manual measurements. Results, from each software package, were compared to published migration rates and manual measurements. COSI-Corr produced more thorough vector coverage but underperformed when applied to large spatial displacements with greater variability. PIVLab had less complete vector coverage but allowed for the isolation of vectors over the dune features resulting in accurate measurements.Item AN EXPERIMENTAL STUDY ON REPAIR OF STEEL BRIDGE PILES USING GFRP CONCRETE-FILLED JACKET(2014-12) Kaya, Ali; Gencturk, Bora E.; Dawood, Mina; Kamrani, Ali K.Many bridges and structures in the United States that are supported on steel piles exhibit inadequate strength due to increasing load demand and aging due to corrosion The combination of increased load demand and reduction of capacity due to corrosion-induced section loss can lead to unexpected buckling of the piles. Several techniques are available to repair these structures to meet the increasing demand and enhance their safety. This thesis investigates the effectiveness of a glass fiber reinforced polymer (GFRP)-based system for rapid repair of buckled steel piles. The system consists of a GFRP tube, which is formed on-site and subsequently filled with an expansive concrete. Thirteen-buckled steel H-piles with varying degrees of section loss to simulate corrosion were repaired and tested to failure under axial loading. The research results show that the repair system can restore the capacity of the piles comparable to the undamaged conditions.Item ANALYTICAL MODELING AND VERIFICATION WITH NUMERICAL METHODS AND EXPERIMENTS OF THREE PHASE REACTIVE MATERIALS, DRILLING, CEMENTING AND PERFORMANCE OF SMART CEMENTED MODEL OIL WELLS(2016-12-15) Basirat, Bahareh; Vipulanandan, Cumaraswamy; Nakshatrala, Kalyana Babu; Rixey, William G.; Samuel, Robello; Lim, Gino J.In this study new analytical models were developed based on using a nonlinear rheological model to predict the drilling and cementing of the oil well. Also, the long term performance of a model field well that was cemented using the smart cement was predicted using a nonlinear piezoresistive model and numerical model. The new reactive three phase material model was developed to characterize the three phase material with reactive constituents and to introduce the six independent reactive material parameters that depend on the curing time, temperature and pressure which contribute to the phase transition. This model can be used for any material with three phases such as cement, drilling mud, filter cake, oil rich rocks and medicines. In order to verify the model, cement slurry with water-cement ratio of 0.4 was tested for over 800 days. The changes in the weight, volume and the moisture content with the curing time was monitored to quantify the change in the three phases. Influence of the six material parameters on the shrinkage, porosity and electrical resistivity of the solidified cement were verified. The resistivity of the cement was influenced by the one reactive model parameter that represented the direct reaction of the liquid phase with the solid phase. The fracture behavior of smart cement was also evaluated using the electrical property monitoring tools in addition to the crack mouth opening displacement (CMOD) gauge. Also, Vipulanandan failure model for material was compared with Drucker–Prager criterion and verified with experimental results. In this study, well drilling and casing installation was investigated analytically using the new shear thinning rheological model. The analytical model predictions were compared to the Newtonian model. The Newtonian model over predicted the flow velocities and shear stress by 300%. Also, the analytical solutions were verified using numerical method. The effects of eccentricity for axial flow is investigated numerically while the eccentricity effect is analyzed analytically for the vortex flow. Later on, a new kinetic model has been developed assuming that the permeability and solid content during the filter cake is changing with time, temperature and pressure using Hyperbolic Model. The new kinetic model was verified with results from of fluid loss and compared with the API model. Also pumping of cement slurry during the well installation was investigated in terms of shear stress developed at the casing and geological formation interfaces. Three physical models simulating the cemented wells (including small model, large model and field model) were tested. During the test, the pressure applied inside the casing in small and large model test and the change of resistivity in smart cement were measured and p, q model was used to correlate the casing pressure to the cement resistivity changes. The numerical model analyzed to define the stresses and displacement along and around the wellbore and verified with the stress predicted from piezoresistivity effects. The smart cement will also predict the pressure inside the well.Item Application of Cupriavidus metallidurans and Ochrobactrum intermedium for Copper and Chromium Biosorption(2013-05) Fan, Jingjing 1988-; Rodrigues, Debora F.; Rixey, William G.; Vipulanandan, CumaraswamyHeavy metals at high concentrations are toxic to the environment and living organisms. The present study aims to investigate the best conditions for the removal of CuSO4.5H2O and KCrO4 by two bacterial species: Ochrobactrum intermedium and Cupriavidus metallidurans. The minimum inhibitory concentrations of C. metallidurans and O. Intermedium were determined to be 750 and 300 ppm for Cu2+, and 100 ppm and 1000 ppm for Cr6+, respectively for each microorganism. Biosorption experiments were also performed with dead and live biomasses of C. metallidurans and O. intermedium. The results show that dead biomass presented better Cu2+ biosorption capacity than live cells. Chromium was removed more efficiently by live cells of O. intermedium than dead biomass; while C. metallidurans dead biomass biosorbed better than live biomass. The biosorption results fitted well with the Langmuir isotherm model. The main mechanism of live biomass adsorption was determined to be through carboxylic, hydroxyl, and amino functional groups.Item Aqueous-Based Processes for Enhanced Dissolution and Displacement/Removal of NAPLs(2018-08) Saladi, Krishna Rishi Vijay; Rixey, William G.; Chellam, Shankar; Nakshatrala, Kalyana Babu; Hu, Yandi; Louie, Stacey M.This dissertation addresses the aqueous-based processes associated with alcohol fuel releases and treatment of hydrocarbon impacted soils. It is comprised of two parts. In Part A, the effects of alcohols (methanol, ethanol, and isobutanol) on the aqueous solubility of benzene, toluene, m-xylene (BTX) and 1,2,4-trimethylbenzene (TMB) from a synthetic gasoline in contact with water were evaluated through equilibrium partitioning experiments. Enhancements in the aqueous solubility of aromatic hydrocarbons were measured over a wide range of aqueous concentrations (0 to ~60 vol.% alcohol). Enhancements in BTX and TMB were observed to be greater for ethanol vs. methanol on a volume fraction of alcohol in aqueous solution basis. Enhancements with isobutanol were greater than those for ethanol and methanol over the range of miscibility of isobutanol in water (0 to ~8 vol.%). Experimental enhancements were compared with predictions using activity coefficient models (UNIQUAC, 2- and 3-suffix Margules) using independently measured binary interaction parameters. In separate experiments, pore water concentrations of alcohols and aromatic hydrocarbons were measured in continuous flow column experiments to determine the pore water impacts of spills with ethanol, methanol, and isobutanol for varying alcohol content (3 %, 15 %, and 25 vol.% alcohol) fuels. Visualization studies were also conducted to examine how the non-aqueous phase liquid (NAPL) sources are generated from these spills and how the alcohols are released for these different fuels. Observed enhancements in hydrocarbon pore water concentrations were consistent with the equilibrium partitioning measurements. Alcohol pore water concentrations for higher fuel contents for methanol and ethanol fuels were characterized by an increase in mass transfer limitations that was also indicated by the visualization studies. Maximum pore water alcohol concentrations for the high alcohol content isobutanol spills were limited by the solubility of isobutanol in water. In Part B, a bench scale physico-chemical aqueous-based separation technique was developed to treat hydrocarbon impacted soils. The primary objective of Part B was the removal of residual NAPL from soils to environmentally acceptable levels either as a single treatment process or as a preliminary step in a treatment train.Item Aquifer Experiments for Characterizing NAPL Sources and Dissolved Plumes following Releases of Ethanol-Blended Fuels(2020-05) Wang, Yifei; Rixey, William G.; Alvarez, Pedro J. J.; Louie, Stacey M.; Shaffer, Devin L.; Vipulanandan, CumaraswamyThis research investigated impacts of releases to the subsurface of ethanol-blended fuels. The overall purpose was to study the evolution of a dissolved plume and non-aqueous phase liquid (NAPL) that is formed/displaced for different fuel ethanol contents in order to develop an understanding of how ethanol fuel contents affect the release, transport, and transformation of ethanol as well as hydrocarbon impacts on water quality. In the first part of the research, low (E25) and high (E85) ethanol fuel blends were released in the unsaturated zone of a pilot-scale aquifer. Pore water concentrations were monitored in the unsaturated zone, in the saturated zone, and in the effluent following the releases. The second part of the research involved smaller-scale studies of ethanol fuel releases in 2D physical model continuous flow cell experiments to better quantify and understand ethanol recovery and the extent of transformation from the large-scale releases of these fuels. These experiments allowed for the visualization of the transport of ethanol in the pore water and the formation of NAPL from the fuel releases. Evaluation of the impacts of these ethanol fuel releases has shown: 1) retention of ethanol in the unsaturated zone for releases containing high ethanol content due to buoyancy, 2) for low ethanol content fuels a fraction of the ethanol was released slowly, controlled by diffusion from the NAPL source, and 3) more rapid source depletion (for high ethanol content) of the more soluble hydrocarbon components in the fuel due to lower NAPL saturation. This research is useful for assessing the extent and persistence of groundwater impacts for realistic spills or leaks of fuels containing ethanol. The results of this research not only apply to ethanol but are also relevant to other alcohols being considered as alternative fuels.Item Assessment of Hydropower Development Impacts on Hydrological Balance and Inundation Dynamics Change of the Lower Mekong River Basin(2022-12-14) Do, Son; Lee, Hyongki; Glennie, Craig L.; Milillo, Pietro; Xie, SuruiDue to rising energy demands and attempts to reduce fossil-fuel dependence, hydropower development has rapidly expanded all around the globe. Once a pristine watershed, the Mekong River basin (MRB) is seeing an unprecedented boom of dams and reservoirs becoming operational or being planned for the near future. Despite their benefits for renewable energy production, hydropower dams and reservoirs can negatively impact the region’s fisheries and agriculture activities. A satellite-based and robust framework that combined Forecasting Inundation Extents using REOF analysis (FIER), Hydrological Predictions for the Environment (HYPE) model, and the Integrated Reservoir Operation Scheme (IROS) is proposed to assess the long-term impact of hydropower development on hydrological balance and inundation dynamics for the Lower Mekong River basin (LMB). Dam-induced alterations, which were the most drastic during the most recent decade, were found to decrease the decadal-average wet season’s water level by up to 3% and increase water level by up to 12% during the dry season. The existence of dams also reduced annual flood occurrence by up to 11 days and altered the inundated area by up to 13% increase and 10% decrease during the dry season and wet season respectively. As a large number of future planning dams are planned for the MRB, we strive to develop the framework as an assessment tool to help local decision makers and water managers investigate the hydrological impacts of hydropower development and maintain the water-food-energy balance in the region.Item Autogenic Processes on Supercritical Submarine Fans(2015-05) Hamilton, Paul; Strom, Kyle B.; Wang, Keh-Han; Dupré, William R.; Wellner, Julia S.; Hoyal, DavidSubmarine fans are large landforms typically built on the continental slope and abyssal plain. They are a amalgamation of depositional lobes emplaced over time through avulsion cycles. These type of intermediate scale processes, particularly related to the hydraulic and sediment transport properties, are poorly understood and understudied. This research experimentally explores supercritical submarine avulsion cycles primarily from a hydraulic perspective. To do so, a new methodology was developed that is capable of measuring the layer-averaged hydraulic variables of developing density currents. This methodology was applied to a series of submarine fan experiments to quantify hydraulic and sediment transport properties. The ability to calculate these properties is imperative toward understanding the intrinsic processes that give rise to autogenic avulsion. Fans developed over time through repeated avulsion consisting of channel incision and basinward extension, cessation of channel extension and mouth bar formation, bar aggradation and hydraulic jump initiation, and upstream propagation of the channel-to-lobe transition. The transition from erosion or bypass in the channels to deposition in an expanded-flow region downstream of the channels was most related to deceleration rather than dilution, and a choked-flow condition appeared to cause hydraulic jump initiation. Each avulsion cycle was responsible for an associated lobe deposit. Since hydraulic jumps were common during avulsion cycles, they were used to predict the maximum thickness of the lobe deposits as a function of the upstream flow depth and Froude number. The classic sequent-depth ratio equation was roughly representative of the data trend from the submarine fan experiments. The lobes emplaced by discrete avulsion cycles stacked up over time to form the overall fan. Though each cycle contained elements of both basinward extension and upstream backfilling, the fans showed net progradation at a long-term rate that can be representatively modeled using a mass balance approach based on sediment supply and equilibrium fan slope. Lastly, the properties of these subaqueous avulsion cycles were compared to similar cycles from alluvial fan experiments. Both systems have supercritical-to-subcritical transition at the channel-to-lobe transition region and detain substantial sediment there. Overall, these two systems appear mechanistically similar.Item Bacteria and Virus Control by Electrochemical Coagulation and Microfiltration(2014-05) Tanneru, Charan Tej; Chellam, Shankar; Rixey, William G.; Rimer, Jeffrey D.; Conrad, Jacinta C.; Baltus, Ruth E.Bench-scale experiments were performed to evaluate microorganism control by electrochemical coagulation and membrane microfiltration. Natural organic matter (NOM) present in natural waters appears to reduce the effectiveness of iron electrocoagulation pretreatment to microfiltration for MS2 virus control by complexing ferrous ions generated at the sacrificial anode during electrolysis. This inhibits (i) Fe2+ oxidation, precipitation, and virus destabilization and (ii) virus inactivation through reactive oxygen species intermediates or by direct interactions with Fe2+ ions. In contrast, higher reductions in MS2 virus concentrations were obtained when aluminum was electrochemically added to surface water. Sweep flocculation was the primary virus destabilization mechanism with secondary contributions from charge neutralization. Direct evidence for virus enmeshment in flocs was provided by two independent methods: quantitative elution using beef extract at elevated pH and quantitating fluorescence from labeled viruses. Monotonically increasing adhesion force between viruses immobilized on AFM tips and floc surfaces with increasing electrocoagulant dosage was measured by atomic force microscopy, which was accompanied by decreasing magnitude of the zeta potential (→ 0) and increasing NOM removal. Hence, virus uptake mechanisms also include charge neutralization and hydrophobic interactions with NOM on floc surfaces. Evidence for virus inactivation was also obtained during iron and aluminum electrocoagulation of synthetic water spiked with viruses. Free chlorine was produced during aluminum electrolysis of saline solutions via oxidation of chloride ions, which inactivated MS2 viruses. Capsid protein modifications probed using Fourier transform infrared spectroscopy (FTIR) revealed significant oxidative modification in amide I and II (1700-1500 cm-1) region. Evidence for genome damage was obtained using quantitative real time polymerase chain reaction (q-RT-PCR). Hence, alterations of capsid proteins and loss of genome structural integrity both contributed to inactivation. Separate experiments were performed to examine the rejection of spherical silica colloids and viruses as well as capsule-shaped bacteria by clean microfiltration membranes. Modeling efforts (performed by Prof. Ruth Baltus’ group at Clarkson University) focused on incorporating the convective hindrance factor for a capsule shaped particle in a cylindrical pore into predictions of the rejection coefficient. Short-term MF experiments were performed at the University of Houston to measure rejection of three Gram negative bacteria, two spherical viruses, and several spherical silica particles by a number of track-etched membranes with near cylindrical pore geometry in a stirred cell before the onset of fouling. Experimental rejections of spherical viruses, and particulate silica and several rod-shaped Gram negative bacteria with aspect ratio from 2 to 5 by clean track-etched membranes were in general agreement with theoretical predictions.