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- All Subjects: Civil Engineering
- Creators: Kavazanjian, Edward
- Resource Type: Text
Description
In geotechnical engineering, measuring the unsaturated hydraulic conductivity of fine grained soils can be time consuming and tedious. The various applications that require knowledge of the unsaturated hydraulic conductivity function are great, and in geotechnical engineering, they range from modeling seepage through landfill covers to determining infiltration of water under a building slab. The unsaturated hydraulic conductivity function can be measured using various direct and indirect techniques. The instantaneous profile method has been found to be the most promising unsteady state method for measuring the unsaturated hydraulic conductivity function for fine grained soils over a wide range of suction values. The instantaneous profile method can be modified by using different techniques to measure suction and water content and also through the way water is introduced or removed from the soil profile. In this study, the instantaneous profile method was modified by creating duplicate soil samples compacted into cylindrical tubes at two different water contents. The techniques used in the duplicate method to measure the water content and matric suction included volumetric moisture probes, manual water content measurements, and filter paper tests. The experimental testing conducted in this study provided insight into determining the unsaturated hydraulic conductivity using the instantaneous profile method for a sandy clay soil and recommendations are provided for further evaluation. Overall, this study has demonstrated that the presence of cracks has no significant impact on the hydraulic behavior of soil in high suction ranges. The results of this study do not examine the behavior of cracked soil unsaturated hydraulic conductivity at low suction and at moisture contents near saturation.
ContributorsJacquemin, Sean Christopher (Author) / Zapata, Claudia (Thesis advisor) / Houston, Sandra (Committee member) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2011
Description
It is estimated that wind induced soil transports more than 500 x 106 metric tons of fugitive dust annually. Soil erosion has negative effects on human health, the productivity of farms, and the quality of surface waters. A variety of different polymer stabilizers are available on the market for fugitive dust control. Most of these polymer stabilizers are expensive synthetic polymer products. Their adverse effects and expense usually limits their use. Biopolymers provide a potential alternative to synthetic polymers. They can provide dust abatement by encapsulating soil particles and creating a binding network throughout the treated area. This research into the effectiveness of biopolymers for fugitive dust control involved three phases. Phase I included proof of concept tests. Phase II included carrying out the tests in a wind tunnel. Phase III consisted of conducting the experiments in the field. Proof of concept tests showed that biopolymers have the potential to reduce soil erosion and fugitive dust transport. Wind tunnel tests on two candidate biopolymers, xanthan and chitosan, showed that there is a proportional relationship between biopolymer application rates and threshold wind velocities. The wind tunnel tests also showed that xanthan gum is more successful in the field than chitosan. The field tests showed that xanthan gum was effective at controlling soil erosion. However, the chitosan field data was inconsistent with the xanthan data and field data on bare soil.
ContributorsAlsanad, Abdullah (Author) / Kavazanjian, Edward (Thesis advisor) / Edwards, David (Committee member) / Zapata, Claudia (Committee member) / Arizona State University (Publisher)
Created2011
Description
As a prelude to a study on the post-liquefaction properties and structure of soil, an investigation of ground freezing as an undisturbed sampling technique was conducted to investigate the ability of this sampling technique to preserve soil structure and properties. Freezing the ground is widely regarded as an appropriate technique to recover undisturbed samples of saturated cohesionless soil for laboratory testing, despite the fact that water increases in volume when frozen. The explanation generally given for the preservation of soil structure using the freezing technique was that, as long as the freezing front advanced uni-directionally, the expanding pore water is expelled ahead of the freezing front as the front advances. However, a literature review on the transition of water to ice shows that the volume of ice expands approximately nine percent after freezing, bringing into question the hypothesized mechanism and the ability of a frozen and then thawed specimen to retain the properties and structure of the soil in situ. Bench-top models were created by pluviation of sand. The soil in the model was then saturated and subsequently frozen. Freezing was accomplished using a pan filled with alcohol and dry ice placed on the surface of the sand layer to induce a unidirectional freezing front in the sample container. Coring was used to recover frozen samples from model containers. Recovered cores were then placed in a triaxial cell, thawed, and subjected to consolidated undrained loading. The stress-strain-strength behavior of the thawed cores was compared to the behavior of specimens created in a split mold by pluviation and then saturated and sheared without freezing and thawing. The laboratory testing provide insight to the impact of freezing and thawing on the properties of cohesionless soil.
ContributorsKatapa, Kanyembo (Author) / Kavazanjian, Edward (Thesis advisor) / Houston, Sandra (Committee member) / Zapata, Claudia (Committee member) / Arizona State University (Publisher)
Created2011
Description
Due to the lack of understanding of soil thermal behavior, rules-of-thumb and generalized procedures are typically used to guide building professionals in the design of ground coupled heat pump systems. This is especially true when sizing the ground heat exchanger (GHE) loop. Unfortunately, these generalized procedures often encourage building engineers to adopt a conservative design approach resulting in the gross over-sizing of the GHE, thus drastically increasing their installation cost. This conservative design approach is particularly prevalent for buildings located in hot and arid climates, where the soils are often granular and where the water table tends to exist deep below the soil surface. These adverse soil conditions reduce the heat dissipation efficiency of the GHE and have hindered the adoption of ground coupled heat pump systems in such climates. During cooling mode operation, heat is extracted from the building and rejected into the ground via the GHE. Prolonged heat dissipation into the ground can result in a coupled flow of both heat and moisture, causing the moisture to migrate away from the GHE piping. This coupled flow phenomenon causes the soil near the GHE to dry out and results in the degradation of the GHE heat dissipation capacity. Although relatively simple techniques of backfilling the GHE have been used in practice to mitigate such coupled effects, methods of improving the thermal behavior of the backfill region around the GHE, especially in horizontal systems, have not been extensively studied. This thesis presents an experimental study of heat dissipation from a horizontal GHE, buried in two backfill materials: (1) dry sand, and (2) wax-sand composite mixture. The HYDRUS software was then used to numerically model the temperature profiles associated with the aforementioned backfill conditions, and the influence of the contact resistance at the GHE-backfill interface was studied. The modeling strategy developed in HYDRUS was proven to be adequate in predicting the thermal performance of GHE buried in dry sand. However, when predicting the GHE heat dissipation in the wax-sand backfill, significant discrepancies between model prediction and experimental results still exist even after calibrating the model by including a term for the contact resistance. Overall, the thermal properties of the backfill were determined to be a key determinant of the GHE heat dissipation capacity. In particular, the wax-sand backfill was estimated to dissipate 50-60% more heat than dry sand backfill.
ContributorsDAngelo, Kurtis (Author) / Reddy, T Agami (Thesis advisor) / Bryan, Harvey (Committee member) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2012
Description
The influence of temperature on soil engineering properties is a major concern in the design of engineering systems such as radioactive waste disposal barriers, ground source heat pump systems and pavement structures. In particular, moisture redistribution under pavement systems might lead to changes in unbound material stiffness that will affect pavement performance. Accurate measurement of thermal effects on unsaturated soil hydraulic properties may lead to reduction in design and construction costs. This thesis presents preliminary results of an experimental study aimed at determining the effect of temperature on the soil water characteristic curve (SWCC) and the unsaturated hydraulic conductivity function (kunsat). Pressure plate devices with volume change control were used to determine the SWCC and the instantaneous profile method was used to obtain the kunsat function. These properties were measured on two fine-grained materials subjected to controlled temperatures of 5oC, 25oC and 40oC. The results were used to perform a sensitivity analysis of the effect of temperature changes on the prediction of moisture movement under a covered area. In addition, two more simulations were performed where changes in hydraulic properties were done in a stepwise fashion. The findings were compared to field measured water content data obtained on the subgrade material of the FAA William Hughes test facility located in Atlantic City. Results indicated that temperature affects the unsaturated hydraulic properties of the two soils used in the study. For the DuPont soil, a soil with high plasticity, it was found that the water retention was higher at low temperatures for suction levels lower than about 10,000 kPa; while the kunsat functions at the three temperatures were not significantly different. For the County soil, a material with medium plasticity, it was found that it holds around 10% more degree of saturation at 5°C than that at 40°C for suction levels higher than about 1,000 kPa; while the hydraulic conductivity at 40°C was at least one order of magnitude higher than that at 5°C, for suction levels higher than 1,000 kPa. These properties were used to perform two types of numerical analyses: a sensitivity analysis and stepwise analysis. Absolute differences between predicted and field measured data were considered to be acceptable, ranging from 4.5% to 9% for all simulations. Overall results show an improvement in predictions when non-isothermal conditions were used over the predictions obtained with isothermal conditions.
ContributorsLu, Yutong (Author) / Zapata, Claudia E (Thesis advisor) / Kavazanjian, Edward (Committee member) / Houston, Sandra L. (Committee member) / Arizona State University (Publisher)
Created2015
Description
Design and mitigation of infrastructure on expansive soils requires an understanding of unsaturated soil mechanics and consideration of two stress variables (net normal stress and matric suction). Although numerous breakthroughs have allowed geotechnical engineers to study expansive soil response to varying suction-based stress scenarios (i.e. partial wetting), such studies are not practical on typical projects due to the difficulties and duration needed for equilibration associated with the necessary laboratory testing. The current practice encompasses saturated “conventional” soil mechanics testing, with the implementation of numerous empirical correlations and approximations to obtain an estimate of true field response. However, it has been observed that full wetting rarely occurs in the field, leading to an over-conservatism within a given design when partial wetting conditions are ignored. Many researchers have sought to improve ways of estimation of soil heave/shrinkage through intense studies of the suction-based response of reconstituted clay soils. However, the natural behavior of an undisturbed clay soil sample tends to differ significantly from a remolded sample of the same material.
In this study, laboratory techniques for the determination of soil suction were evaluated, a methodology for determination of the in-situ matric suction of a soil specimen was explored, and the mechanical response to changes in matric suction of natural clay specimens were measured. Suction-controlled laboratory oedometer devices were used to impose partial wetting conditions, similar to those experienced in a natural setting. The undisturbed natural soils tested in the study were obtained from Denver, CO and San Antonio, TX.
Key differences between the soil water characteristic curves of the undisturbed specimen test compared to the conventional reconstituted specimen test are highlighted. The Perko et al. (2000) and the PTI (2008) methods for estimating the relationship between volume and changes in matric suction (i.e. suction compression index) were evaluated by comparison to the directly measured values. Lastly, the directly measured partial wetting swell strain was compared to the fully saturated, one-dimensional, oedometer test (ASTM D4546) and the Surrogate Path Method (Singhal, 2010) to evaluate the estimation of partial wetting heave.
In this study, laboratory techniques for the determination of soil suction were evaluated, a methodology for determination of the in-situ matric suction of a soil specimen was explored, and the mechanical response to changes in matric suction of natural clay specimens were measured. Suction-controlled laboratory oedometer devices were used to impose partial wetting conditions, similar to those experienced in a natural setting. The undisturbed natural soils tested in the study were obtained from Denver, CO and San Antonio, TX.
Key differences between the soil water characteristic curves of the undisturbed specimen test compared to the conventional reconstituted specimen test are highlighted. The Perko et al. (2000) and the PTI (2008) methods for estimating the relationship between volume and changes in matric suction (i.e. suction compression index) were evaluated by comparison to the directly measured values. Lastly, the directly measured partial wetting swell strain was compared to the fully saturated, one-dimensional, oedometer test (ASTM D4546) and the Surrogate Path Method (Singhal, 2010) to evaluate the estimation of partial wetting heave.
ContributorsOlaiz, Austin Hunter (Author) / Houston, Sandra (Thesis advisor) / Zapata, Claudia (Committee member) / Kavazanjian, Edward (Committee member) / Arizona State University (Publisher)
Created2017
Description
The public has expressed a growing desire for more sustainable and green technologies to be implemented in society. Bio-cementation is a method of soil improvement that satisfies this demand for sustainable and green technology. Bio-cementation can be performed by using microbes or free enzymes which precipitate carbonate within the treated soil. These methods are referred to as microbial induced carbonate precipitation (MICP) and enzyme induced carbonate precipitation (EICP). The precipitation of carbonate is the formation of crystalline minerals that fill the void spaces within a body of soil.
This thesis investigates the application of EICP in a soil collected from the Arizona State University Polytechnic campus. The surficial soil in the region is known to be a clayey sand. Both EICP and MICP have their limitations in soils consisting of a significant percentage of fines. Fine-grained soils have a greater surface area which requires the precipitation of a greater amount of carbonate to increase the soil’s strength. EICP was chosen due to not requiring any living organisms during the application, having a faster reaction rate and size constraints.
To determine the effectiveness of EICP as a method of improving a soil with a significant amount of fines, multiple comparisons were made: 1) The soil’s strength was analyzed on its own, untreated; 2) The soil was treated with EICP to determine if bio-cementation can strengthen the soil; 3) The soil had sand added to reduce the fines content and was treated with EICP to determine how the fines percentage effects the strength of a soil when treated with EICP.
While the EICP treatment increased the strength of the soil by over 3-fold, the strength was still relatively low when compared to results of other case studies treating sandy soils. More research could be done with triaxial testing due to the samples of the Polytechnic soil’s strength coming from capillarity.
This thesis investigates the application of EICP in a soil collected from the Arizona State University Polytechnic campus. The surficial soil in the region is known to be a clayey sand. Both EICP and MICP have their limitations in soils consisting of a significant percentage of fines. Fine-grained soils have a greater surface area which requires the precipitation of a greater amount of carbonate to increase the soil’s strength. EICP was chosen due to not requiring any living organisms during the application, having a faster reaction rate and size constraints.
To determine the effectiveness of EICP as a method of improving a soil with a significant amount of fines, multiple comparisons were made: 1) The soil’s strength was analyzed on its own, untreated; 2) The soil was treated with EICP to determine if bio-cementation can strengthen the soil; 3) The soil had sand added to reduce the fines content and was treated with EICP to determine how the fines percentage effects the strength of a soil when treated with EICP.
While the EICP treatment increased the strength of the soil by over 3-fold, the strength was still relatively low when compared to results of other case studies treating sandy soils. More research could be done with triaxial testing due to the samples of the Polytechnic soil’s strength coming from capillarity.
ContributorsRoss, Johnathan (Author) / Kavazanjian, Edward (Thesis advisor) / Zapata, Claudia (Committee member) / Hamdan, Nasser (Committee member) / Arizona State University (Publisher)
Created2018
Description
This thesis was prepared by Tyler Maynard and Hayley Monroe, who are students at Arizona State University studying to complete their B.S.E.s in Civil Engineering and Construction Engineering, respectively. Both students are members of Barrett, the Honors College, at Arizona State University, and have prepared the following document for the purpose of completing their undergraduate honors thesis. The early sections of this document comprise a general, introductory overview of earthquakes and liquefaction as a phenomenon resulting from earthquakes. In the latter sections, this document analyzes the relationship between the furthest hypocentral distance to observed liquefaction and the earthquake magnitude published in 2006 by Wang, Wong, Dreger, and Manga. This research was conducted to gain a greater understanding of the factors influencing liquefaction and to compare the existing relationship between the maximum distance for liquefaction and earthquake magnitude to updated earthquake data compiled for the purpose of this report. As part of this research, 38 different earthquake events from the Geotechnical Extreme Events Reconnaissance (GEER) Association with liquefaction data were examined. Information regarding earthquake depth, distance to the furthest liquefaction event (epicentral and hypocentral), and earthquake magnitude (Mw) from recent earthquake events (1989 to 2016) was compared to the previously established relationship of liquefaction occurrence distance to moment magnitude. The purpose of this comparison was to determine if recent events still comply with the established relationship. From this comparison, it was determined that the established relationship still generally holds true for the large magnitude earthquakes (magnitude 7.5 or above) that were considered herein (with only 2.6% falling above the furthest expected liquefaction distance). However, this relationship may be too conservative for recent, low magnitude earthquake events; those events examined below magnitude 6.3 did not approach established range of furthest expected liquefaction distance. The overestimation of furthest hypocentral distance to liquefaction at low magnitudes suggest the empirical relationship may need to be adjusted to more accurately capture recent events, as reported by GEER.
ContributorsMonroe, Hayley (Co-author) / Maynard, Tyler (Co-author) / Kavazanjian, Edward (Thesis director) / Houston, Sandra (Committee member) / Civil, Environmental and Sustainable Engineering Program (Contributor) / Construction Engineering (Contributor) / Barrett, The Honors College (Contributor)
Created2017-12
Description
The dissimilatory reduction of nitrate, or denitrification, offers the potential of a sustainable, cost effective method for the non-disruptive mitigation of earthquake-induced soil liquefaction. Worldwide, trillions of dollars of infrastructure are at risk for liquefaction damage in earthquake prone regions. However, most techniques for remediating liquefiable soils are either not applicable to sites near existing infrastructure, or are prohibitively expensive. Recently, laboratory studies have shown the potential for biogeotechnical soil improvement techniques such as microbially induced carbonate precipitation (MICP) to mitigate liquefaction potential in a non-disruptive manner. Multiple microbial processes have been identified for MICP, but only two have been extensively studied. Ureolysis, the most commonly studied process for MICP, has been shown to quickly and efficiently induce carbonate precipitation on particle surfaces and at particle contacts to improve the stiffness, strength, and dilatant behavior of liquefiable soils. However, ureolysis also produces copious amounts of ammonium, a potentially toxic byproduct. The second process studied for MICP, denitrification, has been shown to precipitate carbonate, and hence improve soil properties, much more slowly than ureolysis. However, the byproducts of denitrification, nitrogen and carbon dioxide gas, are non-toxic, and present the added benefit of rapidly desaturating the treated soil. Small amounts of desaturation have been shown to increase the cyclic resistance, and hence the liquefaction resistance, of liquefiable soils. So, denitrification offers the potential to mitigate liquefaction as a two-stage process, with desaturation providing short term mitigation, and MICP providing long term liquefaction resistance. This study presents the results of soil testing, stoichiometric modeling, and microbial ecology characterization to better characterize the potential use of denitrification as a two-stage process for liquefaction mitigation.
ContributorsO'Donnell, Sean (Author) / Kavazanjian, Edward (Thesis advisor) / Rittmann, Bruce (Committee member) / Houston, Sandra (Committee member) / Arizona State University (Publisher)
Created2016
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