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- All Subjects: Bridge
- All Subjects: Geophysical engineering
- Creators: Kavazanjian, Edward
- Resource Type: Text
Description
This dissertation details an attempt to experimentally evaluate the Giroud et al. (1995) concentration factors for geomembranes loaded in tension perpendicular to a seam by laboratory measurement. Field observations of the performance of geomembrane liner systems indicates that tears occur at average strains well below the yield criteria. These observations have been attributed, in part, to localized strain concentrations in the geomembrane loaded in tension in a direction perpendicular to the seam. Giroud et al. (1995) has presented theoretical strain concentration factors for geomembrane seams loaded in tension when the seam is perpendicular to the applied tensile strain. However, these factors have never been verified. This dissertation was prepared in fulfillment of the requirements for graduation from Barrett, the Honors College at Arizona State University. The work described herein was sponsored by the National Science Foundation as a part of a larger research project entitled "NEESR: Performance Based Design of Geomembrane Liner Systems Subject to Extreme Loading." The work is motivated by geomembrane tears observed at the Chiquita Canyon landfill following the 1994 Northridge earthquake. Numerical analysis of the strains in the Chiquita Canyon landfill liner induced by the earthquake indicated that the tensile strains, were well below the yield strain of the geomembrane material. In order to explain why the membrane did fail, strain concentration factors due to bending at seams perpendicular to the load in the model proposed by Giroud et al. (1995) had to be applied to the geomembrane (Arab, 2011). Due to the localized nature of seam strain concentrations, digital image correlation (DIC) was used. The high resolution attained with DIC had a sufficient resolution to capture the localized strain concentrations. High density polyethylene (HDPE) geomembrane samples prepared by a leading geomembrane manufacturer were used in the testing described herein. The samples included both extrusion fillet and dual hot wedge fusion seams. The samples were loaded in tension in a standard triaxial test apparatus. to the seams in the samples including both extrusion fillet and dual hot wedge seams. DIC was used to capture the deformation field and strain fields were subsequently created by computer analysis.
ContributorsAndresen, Jake Austin (Author) / Kavazanjian, Edward (Thesis director) / Gutierrez, Angel (Committee member) / Civil, Environmental and Sustainable Engineering Programs (Contributor) / Barrett, The Honors College (Contributor)
Created2016-05
Description
The understanding of multiphase fluid flow in porous media is of great importance in many fields such as enhanced oil recovery, hydrology, CO2 sequestration, contaminants cleanup, and natural gas production from hydrate bearing sediments.
In this study, first, the water retention curve (WRC) and relative permeability in hydrate bearing sediments are explored to obtain fitting parameters for semi-empirical equations. Second, immiscible fluid invasion into porous media is investigated to identify fluid displacement pattern and displacement efficiency that are affected by pore size distribution and connectivity. Finally, fluid flow through granular media is studied to obtain fluid-particle interaction. This study utilizes the combined techniques of discrete element method simulation, micro-focus X-ray computed tomography (CT), pore-network model simulation algorithms for gas invasion, gas expansion, and relative permeability calculation, transparent micromodels, and water retention curve measurement equipment modified for hydrate-bearing sediments. In addition, a photoelastic disk set-up is fabricated and the image processing technique to correlate the force chain to the applied contact forces is developed.
The results show that the gas entry pressure and the capillary pressure increase with increasing hydrate saturation. Fitting parameters are suggested for different hydrate saturation conditions and morphologies. And, a new model for immiscible fluid invasion and displacement is suggested in which the boundaries of displacement patterns depend on the pore size distribution and connectivity. Finally, the fluid-particle interaction study shows that the fluid flow increases the contact forces between photoelastic disks in parallel direction with the fluid flow.
In this study, first, the water retention curve (WRC) and relative permeability in hydrate bearing sediments are explored to obtain fitting parameters for semi-empirical equations. Second, immiscible fluid invasion into porous media is investigated to identify fluid displacement pattern and displacement efficiency that are affected by pore size distribution and connectivity. Finally, fluid flow through granular media is studied to obtain fluid-particle interaction. This study utilizes the combined techniques of discrete element method simulation, micro-focus X-ray computed tomography (CT), pore-network model simulation algorithms for gas invasion, gas expansion, and relative permeability calculation, transparent micromodels, and water retention curve measurement equipment modified for hydrate-bearing sediments. In addition, a photoelastic disk set-up is fabricated and the image processing technique to correlate the force chain to the applied contact forces is developed.
The results show that the gas entry pressure and the capillary pressure increase with increasing hydrate saturation. Fitting parameters are suggested for different hydrate saturation conditions and morphologies. And, a new model for immiscible fluid invasion and displacement is suggested in which the boundaries of displacement patterns depend on the pore size distribution and connectivity. Finally, the fluid-particle interaction study shows that the fluid flow increases the contact forces between photoelastic disks in parallel direction with the fluid flow.
ContributorsMahabadi, Nariman (Author) / Jang, Jaewon (Thesis advisor) / Zapata, Claudia (Committee member) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2016
Description
Laboratory testing was conducted to quantify strain concentrations adjacent to seams and scratches in high density polyethylene (HDPE) geomembranes. The tensile strain profile of remnants meeting the ASTM criteria for wide-width tensile testing from samples of field seams recovered for construction quality assurance testing was evaluated using digital image correlation (DIC). Strains adjacent to scratches on laboratory prepared samples loaded in tension were also measured using DIC. The tensile strain in the zone adjacent to a seam and the tensile strain adjacent to a scratch were compared to the tensile strains calculated using theoretical strain concentration factors. The relationship between the maximum tensile strain adjacent to a seam and the global nominal strain in the sample was quantified for textured and smooth geomembranes of common thicknesses. Using statistical analysis of the data, bounds were developed for the allowable nominal tensile strain expected to induce maximum tensile strains adjacent to the seam less than or equal to the typical yield strain of HDPE geomembranes, at several confidence levels. Where nominal strain is the global or average strain applied to the sample and maximum strain is the largest tensile strain induced in the sample.
The reduction in the nominal yield strain due to a scratch in a HDPE geomembrane was also quantified. The yield strain was approximately the same as predicted using theoretical strain concentration factors. The difference in the average measured maximum strains adjacent to the seams of textured and smooth HDPE geomembranes was found to be statistically insignificant. However, maximum strains adjacent to extrusion welded seams were somewhat greater than adjacent to fusion welded seams for nominal strains on the order of 3% to 4%. The results of the testing program suggest that the nominal tensile strain should be limited to 4% around dual hot wedge seams and 3% around extrusion fillet seams to avoid maximum strains equal to 11%, a typical yield strain for HDPE geomembranes.
The reduction in the nominal yield strain due to a scratch in a HDPE geomembrane was also quantified. The yield strain was approximately the same as predicted using theoretical strain concentration factors. The difference in the average measured maximum strains adjacent to the seams of textured and smooth HDPE geomembranes was found to be statistically insignificant. However, maximum strains adjacent to extrusion welded seams were somewhat greater than adjacent to fusion welded seams for nominal strains on the order of 3% to 4%. The results of the testing program suggest that the nominal tensile strain should be limited to 4% around dual hot wedge seams and 3% around extrusion fillet seams to avoid maximum strains equal to 11%, a typical yield strain for HDPE geomembranes.
ContributorsAndresen, Jake (Author) / Kavazanjian, Edward (Thesis advisor) / Houston, Sandra (Committee member) / Zapata, Claudia (Committee member) / Arizona State University (Publisher)
Created2017
Description
This report analyzed the dynamic response of a long, linear elastic concrete bridge subject to spatially varying ground displacements as well as consistent ground displacements. Specifically, the study investigated the bridge’s response to consistent ground displacements at all supports (U-NW), ground displacements with wave passage effects and no soil profile variability (U-WP), and ground displacements with both wave passage effects and soil profile variability (V-WP). Time-history ground displacements were taken from recordings of the Loma Prieta, Duzce, and Chuetsu earthquakes. The two horizontal components of each earthquake time-history displacement record were applied to the bridge supports in the transverse and longitudinal directions. It was found that considering wave passage effects without soil profile variability, as compared with consistent ground displacements, significantly reduced the peak total energy of the system, as well as decreasing the maximum relative longitudinal displacements. The maximum relative transverse displacements were not significantly changed in the same case. It was also found that including both wave passage effects and soil profile variability (V-WP) generally resulted in larger maximum transverse relative displacements, across all earthquake time-histories tested. Similarly, it was found that using consistent ground displacements (U-NW) generally resulted in larger maximum longitudinal relative displacements, as well as larger peak total energy values.
ContributorsSeawright, Jordan Michael (Author) / Hjelmstad, Keith (Thesis advisor) / Rajan, Subramaniam D. (Committee member) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2019
Description
Bridge scour at piers is a major problem for design and for maintaining old infrastructure. The current methods require their own upkeep and there may be better ways to mitigate scour. I looked to the mangrove forests of coastal environments for inspiration and have developed a 2D model to test the efficacy of placing a mangrove-root inspired system to mitigate scour. My model tests the hydrodynamics of the root systems, but there are additional benefits that can be used as bioinspiration in the future (altering the surrounding chemistry and mechanical properties of the soil).Adding a mangrove inspired minipile system to bridge piers changes scour parameters within my 2D COMSOL models. For the volume of material added, the minipiles compare favorably to larger sacrificial piles as they reduce A_wcz and 〖τ'〗_max by similar (or even better) amounts. These two parameters are indicators of scour in the field. Within the minipile experiments, it is more beneficial to place them upstream of the main bridge pier as their own ‘mangrove forest.’ The value of A_wcz and 〖τ'〗_max for complex 2D models of scour is unclear and physical experiments need to be performed. The model geometry is based on the dimensions of the experimental flume to be used in future studies and the model results have not yet been verified through experiments and field trials. Scale effects may be present which cannot be accounted for in the 2D models. Therefore future work should be conducted to test ‘mangrove forest’ minipile systems in 3D space, in flume experiments, and in field trials.
ContributorsEnns, Andrew Carl (Author) / van Paassen, Leon (Thesis advisor) / Tao, Junliang (Thesis advisor) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2021