Browsing by Subject "Clay"

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Characterization of the swelling behavior of expansive clays using centrifuge technology
(2021-08-13) Rivas, Nicolas Alejandro; Zornberg, Jorge G.
Experimental techniques with emphasis in centrifuge testing were implemented to characterize the swelling behavior of expansive clays. This research consisted in three self-contained sections related to the study of different aspects of expansive clays. The first research component focused on the implementation of a qualitative mineralogy analysis performed using x-ray diffraction to determine the main clay minerals in an expansive soil. The analysis was performed on the clay-sized fraction of the soil and samples with preferential and random orientation were used in the analysis. Vacuum filtration was used to produce oriented samples in order to maximize the intensity of the diagnostic basal spacing of the clay minerals, and samples were subjected to different treatments to produce changes in the basal spacing or crystalline structure of the clay minerals to facilitate their identification. The second research component examined the effect of the coarse fraction on the swelling characteristics of expansive soils using a centrifuge-based approach. Vertical strains at the end of primary swelling were evaluated for different proportions of coarse fraction by volume. It was found that the magnitude of vertical strains at the end of primary swelling decreased with increasing coarse fraction. It was concluded that the swelling depended uniquely on the ratio between the volume of soil solids of the fine fraction and the volume of voids. Additionally, when correcting the initial void ratio of the specimens to account for this, the relationship between vertical strains at the end of primary swelling and initial void ratio for the soil mixtures defines a unique linear trend with the baseline material. The third research component examined the potential vertical rise at three field sites in Central Texas. Method 6048-A was applied to evaluate the PVR of three field sites using direct measurements of the swelling characteristics of soils sampled at each location. Project-specific data was generated in a relatively short time using this centrifuge-based method. The results obtained demonstrated the need for testing of project-specific samples, as a significant variation in PVR was observed in Site 2 and 3 between boring locations, while less variation between borings was found in Site 1
Clay-based materials for passive control of ozone and reaction byproducts in buildings
(2016-05) Darling, Erin Kennedy; Corsi, Richard L.; Brown Wilson, Barbara; Juenger, Maria; Novoselac, Atila; Xu, Ying
Tropospheric ozone that infiltrates buildings reacts readily with many indoor materials and compounds that are commonly detected in indoor air. These reactions lead to lower indoor ozone concentrations. However, the products of ozone reactions may be irritating or harmful to building occupants. While active technologies exist (i.e., activated carbon filtration in HVAC systems) to suppress indoor ozone concentrations, they can be costly and/or infeasible for dwellings that do not have these systems. Passive methods of ozone removal are an interest of building environment researchers. This dissertation involves (1) a review of the state of the knowledge on building materials and coatings that are intended to passively remove indoor ozone, especially clay-based materials; (2) a compilation of current data on ozone removal and reaction byproduct formation for these materials; (3) a model for ozone removal effectiveness for a selected clay-based material that is implemented in a hypothetical home; (4) a survey of the effects of a clay-based coating with and without ozone and a reactant source on human perceptions of air quality; (5) an investigation of the long-term potential for passive control of indoor ozone by two different clay-based surface coatings that were exposed to real indoor environments; and (6) development of a location-specific model to estimate the monetary benefits versus costs of indoor ozone control using passive removal materials. The above tasks were completed through ongoing reviews of the literature, experimental studies conducted in small and large environmental chambers, and in the field. Results of these studies suggest that clay or materials made from clay are a viable material for passive reduction of indoor pollution, due in part to clay’s ability to catalyze ozone. Human sensory perceptions of indoor air quality were shown to significantly improve when a clay-based plaster was present in an ozonated environment. Based on modeling efforts, effective passive removal of indoor ozone is possible for realistic indoor scenarios when clay-based materials are implemented. There is a growing number of papers that are published on the subject of clay materials and indoor environmental quality, but few that investigate the longer term impacts and performance of clay materials, especially ones that have been exposed to real indoor environments.
Design of large diameter monopiles for offshore wind turbines in clay
(2016-08) Senanayake, Asitha Indun Madusanka Joshua; Gilbert, Robert B. (Robert Bruce), 1965-; Wang, Shin-Tower; Cox, Brady; Manuel, Lance; Murff, James D
Offshore wind power has great potential as a clean and renewable energy source that is capable of reducing our reliance on fossil fuels. The main drawback of offshore wind power is its comparatively high capital cost. One area in which this cost can be reduced is by optimizing the design of these structures. More efficient foundation designs is key in this regard. The p-y method is extensively used for the design and analysis of laterally loaded piles due to its simplicity and versatility. Matlock (1970) or the API RP 2GEO (2011) “soft” clay p-y model is the guideline of choice for normally consolidated to moderately overconsolidated clays. However, this p-y model is not yet verified for piles with very large diameters and low aspect ratios. Design of wind turbine monopiles is governed by serviceability limits such as the natural frequency of the structure and the accumulated tilt under long-term low-amplitude cyclic loads, but these guidelines have not been verified for serviceability limit state designs. The main objectives of this study were to: (a) assess the ability of the Matlock (1970) p-y model to accurately model the behavior of laterally loaded piles at both small and large displacements, (b) investigate the effect of gapping on the backside of laterally loaded piles and develop a theoretical framework to quantify its effect and predict its occurrence, (c) re-examine the derivation of lateral bearing capacity factors (N p ) used in published p-y models, (d) evaluate the effect of large numbers of small-amplitude cyclic load on the stiffness and the post-cyclic ultimate capacity of laterally loaded piles, (e) assess the ability of the Matlock (1970) p-y model to adequately account for pile diameter effects, (f) assess the ability of the Matlock (1970) p-y model to accurately predict the behavior of a pile in a variety of undrained shear strength versus depth profiles, (g) assess the ability of published p-y models to accurately predict the natural frequency of wind turbine structures. The methodology consisted of analyzing field tests, laboratory model tests (1-g and centrifuge), and numerical modeling. An extensive database of field tests and laboratory centrifuge tests was compiled. This data was then supplemented by a series of 1-g model tests in a variety of clay test beds (normally consolidated to heavily overconsolidated, kaolinite and Gulf of Mexico clay) carried out at The University of Texas at Austin and 3-d finite-elements models using Abaqus carried out by Ensoft Inc. The following conclusions were drawn from this study: (a) Matlock (1970) p-y model underestimates the lateral soil resistance on piles in normally consolidated and overconsolidated clays, regardless of pile diameter or aspect ratio, (b) the effect of gapping plays an important role in determining the pile response as it can lead to a loss of capacity and a reduction in stiffness, (c) lateral bearing capacity factors used in the Matlock (1970) model are too low, (d) the degradation in the stiffness of the pile response, when subjected to cyclic loading, was limited to approximately 30% and occurred within the first 100 cycles, (e) the method of normalizing used in the Matlock (1970) model successfully accounts for pile diameter effects, (f) estimates of the natural frequency of wind turbine structure based on the API RP 2GEO (2011) p-y model are lower than those based on the Matlock (1970) and Jeanjean (2009) p-y models.
Development of ASP formulations for reactive crude oil in high clay, high temperature reservoirs
(2012-08) Tipley, Kyle Andrew; Pope, Gary A.; Weerasooriya, Upali P.
Surfactant formulations consisting of surfactant, alkali, polymer, and electrolyte have been developed using well defined screening processes established through experimentation in labs around the world. Due to recent advances in chemical enhanced oil recovery, surfactants can be used to extend the life of mature reservoirs with increasingly diverse conditions. High temperatures, complex geochemistry, or high clay content can provide significant challenges when developing formulations for chemical flooding. Through careful selection and screening of surfactants and chemicals, oil recovery of greater than 90% can be achieved in laboratory corefloods despite these difficulties. The objective of this research was to determine the ideal surfactant formulation using a sulfate surfactant for a reservoir with high clay content at 85 ºC. Advances in our laboratory have shown sulfate surfactants to be stable under specific conditions at elevated temperature. In addition, new methods of synthesizing surfactants have yielded a vast array of structures and iterations of novel surfactants to test for EOR applicability. Experiments contained within include surfactant screening both with and without the presence of crude oil and evaluation of polymer and microemulsion viscosity. From these results, a series of corefloods were performed in Berea and reservoir corefloods that yielded oil recovery of 90% and above with low surfactant retention.
Hydrothermal activity
(2009-03) Barker, Daniel S.
Identifying and mapping clay-rich intervals in the Fayetteville Shale : influence of clay on natural gas production intervals
(2013-12) Roberts, Forrest Daniel; Tinker, Scott W. (Scott Wheeler); Fisher, W. L. (William Lawrence), 1932-
The Fayetteville Shale is composed dominantly of clay, carbonate, and siliciclastic minerals. A variety of facies have been described by other workers and in this study, defined by mineral content, biota, fabric, and texture. Because the Fayetteville Shale is one of the top shale-gas producing plays in the U.S., an inquiry into key drivers of good-quality production is worthwhile. In particular, a hypothesis that intervals of high clay content should be avoided as production targets is investigated in this study. A high level of separation between wire-line log neutron porosity (NPHI) and density porosity (DPHI) in the Fayetteville Shale is observed in contrast to the wire-line log responses from the Barnett and Haynesville Shales. Clay minerals have a significant effect on NPHI, which in turn affects separation between NPHI and DPHI (PHISEP). X-Ray Diffraction (XRD) clay data was available for three wells, and efforts to correlate XRD results to PHISEP led to establishing NPHI as a reasonable proxy for clay. Using NPHI as a proxy it was possible to pick clay-rich intervals, map them across the study area, and to determine net clay in the Fayetteville Shale. Maps of net clay-rich intervals were compared to a map of production, but revealed no obvious correlation. Stratigraphic cross-sections showing the clay-rich intervals revealed a clay-poor interval in the upper part of the lower Fayetteville. This interval is the primary target for horizontal well completion. It is bounded above and below by more clay-rich intervals. Establishing the clay-rich intervals via porosity log separation (PHISEP) is one tool to help determine possible stratigraphic zones of gas production and can lead to a better understanding of intervals in which to expect production.
Impacts of a clay plaster on actual and perceived indoor air quality
(2011-08) Darling, Erin Kennedy; Corsi, Richard L.; Ying, Xu
Passive removal materials (PRMs) are building materials or furnishings that can effectively control indoor pollution without substantial formation of chemical byproducts and without energy penalty. To assess clay wall plaster as an effective PRM for improving air quality by controlling ozone, perceived air quality (PAQ) was determined in the presence of eight combinations of an emitting and reactive pollutant source (new carpet), clay plaster applied to gypsum wallboard, and chamber air with and without ozone. A panel of 18 to 23 human subjects assessed air quality in twin 30 m3 chambers using a continuous acceptability scale. Air samples were collected immediately prior to panel assessment to quantify concentrations of C5 to C10 saturated n-aldehydes and two aromatic aldehydes that are commonly produced by reaction of ozone with carpet. Perceived Air Quality was most acceptable and concentrations of aldehydes were lowest when only clay plaster or both clay plaster and carpet were present in the chambers without ozone. The least acceptable PAQ and the highest concentrations of aldehydes were observed when carpet and ozone were present together; addition of clay plaster for this condition improved PAQ and considerably decreased aldehyde concentrations. Ozone deposition and byproduct emissions of the clay wall plaster were also assessed using 48 liter stainless steel chambers. Clay plaster applied to gypsum wallboard that had been exposed in a test house (UTest House) for one year effectively removed 88% of the ozone, and emitted high aldehyde concentrations when exposed to high purity air that did not increase when the material was exposed to ozone. The outcome of these experiments leads to speculation that the clay plaster adsorbed contaminants in the test house and then re-emitted them upon exposure to clean air in the small chambers.
Nanocomposites of poly(acrylonitrile-butadiene-styrene) and montmorillonite clay: dispersion and mechanical properties
(2005) Stretz, Holly Ann; Paul, Donald R.
Polymer/montmorillonite clay (MMT) nanocomposites have produced significant commercial interest due to the excellent balance of properties, but the issues controlling proper clay dispersion are poorly understood. Current studies examine the effects of polymer and organoclay structure on properties of melt-processed poly(styrene-coacrylonitrile) (SAN)/MMT, where SAN models the more complex ABS/MMT composites used in computer housings. Initially we examined the effects of organoclay surfactant structure on filler dispersion and composite mechanical properties. The composite which exhibited the highest modulus and greatest particle viii aspect ratio (~50) was produced from an organoclay with the lowest molecular weight surfactant. Swelling of the MMT particles, measured by x-ray diffraction, was more strongly related to reduced surfactant molecular weight than surfactant functionality. The composite moduli were compared to Halpin-Tsai theoretical predictions from TEM-based aspect ratios. Given a range of surfactant structures, we then explored the appropriateness of the SAN matrix as a model for ABS. Electron microscopy showed that clay particles in ABS/MMT composites reside in the SAN matrix phase, accumulating at rubber particle surface. Modulus enhancement patterns were the same for a given organoclay, but reinforcement in ABS was lower due to poor orientation of particles at the rubber surface. Interactions between the polymer and silicate surface were probed by varying the SAN copolymer composition, accounting for variations in matrix modulus and melt viscosity. TEM-based image analysis coupled with Mori-Tanaka composite theory gave predictions which fit experimental moduli better than Halpin-Tsai. Higher acrylonitrile content lead to increased reinforcement in the 0-58 weight % acrylonitrile range. TEM-based specific particle densities reached ~8 particles/μm2 compared to well-exfoliated nylon 6 composites at 100 particles/μm2. Improvements in exfoliation were also noted for higher screw rpm. ix Based on enhancement in exfoliation for polyolefin-g-maleic anydride composites, the effect of maleic anhydride in SMA-based nanocomposites was studied. These materials produced the same properties on a weight percent basis as SAN-based nanocomposites, but particle densities remained lower than for polyolefin-g-MA mixtures. This behavior is explained by repulsive interactions between styrene and the alkyl tail of the surfactant, suggesting that polar surfactant tails could lead to improved exfoliation in styrene copolymer-based/montmorillonite nanocomposites.
Performance of drag embedment anchors dragged through remolded clay and loaded at various horizontal orientations
(2009-12) Lynk, John Michael; Gilbert, Robert B. (Robert Bruce), 1965-; El Mohtar, Chadi
Drag embedment anchors (DEAs, or anchors) are used as foundations to secure mobile offshore drilling units (MODUs) in soft clay soils on the sea floor. In 2004 and 2005, Hurricanes Ivan, Katrina, and Rita caused the mooring failures of 17 mobile offshore drilling units moored with anchors. Since then, a great deal of research has been conducted regarding anchor performance and reliability. This report provides an overview of anchor research and industry practice to date, and discusses the results of two research experiments to assess anchor performance. One experiment investigated the effect that embedding anchors in the same soil path several times had on bearing force. The second experiment investigated what effect changing the direction of the horizontal load vector relative to the anchor shank had on embedded anchor bearing force. The results of these experiments suggest that remolding clay may have an effect on anchor bearing force capacity, and that repeatable results are obtainable when testing the effect of changing the direction of applied horizontal load.
A reconnaissance report on the geology of the oil and gas fields of Wichita and Clay counties, Texas
(University of Texas at Austin, 1912-09-08) Udden, Johan August
Reconstructive-memory process
(2012-05) Shin, Yun Koung; Mutchler, Leslie; Goodman, Mark
This graduate report is a description of my artistic development through the graduate program at the University of Texas at Austin. It records my development and growth as an artist in relationship to the concepts, materials, and processes I have been investigating and exploring in the past three years. The graduate report focuses on three important concerns to which I’ve been dedicated. First, materials are imperative to my work. I physically collect and use my father’s ordinary objects and transform them with raw materials, such as clay, flour, honey, chocolate, beeswax, and petroleum jelly. The decision of choosing raw materials is based on my personal and cultural experiences. I am particularly interested in exploiting raw materials because I believe these raw materials can trigger a particular memory, place, or relationship that I want to preserve and remember. Second, my process of making involves ritualistic aspects with repetitive acts. I believe that everyday practices are a way of reconstructing relationships and remembering home. I am interested in embracing emotional attributes that may be simple activities: spraying a piece daily to keep it wet or sewing a personal object until it is impossible to sew. Finally, through the relationship among the objects, repeated actions, and an anticipation that evokes magical power and charged energy, I methodically transform objects. I do this to celebrate emotions and to preserve not only these personal objects but also my memories of home.