• Impact Of Freeze -Thaw On Liquefaction Potential And Dynamic Properties Of Mabel Creek Silt

      Zhang, Yu (2009)
      In the early winter of 2002 (November), the Alaska Denali earthquake (Mw=-7.9) caused significant damage in partially frozen fine-grained soil and extensive liquefaction was observed in glacial fine-grained saturated soil surface deposits near Tok, Alaska. It illustrated that there was a need to evaluate the seismic response and liquefaction potential of fine-grain soil in cold regions; however, until now most of the research on the liquefaction phenomenon and seismic response were mainly about soil in non-cold regions. The seismic response and liquefaction potential of soils in cold regions, especially those of fine-grained nature, has not been studied thoroughly and therefore is not well-understood. This document presents a laboratory study on liquefaction potential and cyclic response of fine-grained soil in cold regions. As the main features of the soil in the ground of cold regions, temperature change at below freezing temperatures or near-freezing temperatures, and the seasonal climate change were evaluated on liquefaction potential, dynamic properties, and post-cyclic-loading settlement of fine-grained soils. Increasing temperatures from near freezing to the completely thawed temperature (i.e., 24�C, 5�C, 1�C, and 0.5�C) were used to thaw the frozen Mabel Creek silt to simulate temperature change on it, or the Mabel Creek silt experienced several freezing and thawing alternating processes (i.e., 1, 2, and 4 freeze-thaw cycles) to simulate seasonal climate change. Triaxial strain-controlled cyclic tests were conducted to evaluate liquefaction potential, dynamic properties, and post-cyclic-loading settlement. Based on this limited laboratory effort, results show that in most cases, temperature rise and freeze-thaw cycles can impact: (a) liquefaction potential, (b) dynamic properties and (c) post-cyclic-loading settlement of fine-grained soils. However, there was one case exception and this is decribed in the following sentence. When a fine-grained soil was conditioned in a partially frozen state, the possibility and threat of liquefaction significantly increased.
    • Biodegradation Of Petroleum And Alternative Fuel Hydrocarbons In Moderate To Cold Climate

      Horel, Agota Anna (2009)
      Microbial degradation of hydrocarbon fuels contaminating soil in the Arctic and subarctic environment is a relatively slow process. Nevertheless, due to transportation and logistical limitations in rural Alaska, biodegradation might be the best and cheapest contaminant removal option. The aim of this thesis was to investigate the environmental effects on biodegradation by naturally occurring microorganisms for some innovative hydrocarbon fuels and to determine the overall fate of hydrocarbons in soil, including degradation by fungi and bacteria, volatilization, and transport in the soil. Three major types of fuels were investigated in small scale microcosms and larger soil columns: conventional diesel as a control substance, synthetic diesel (arctic grade Syntroleum) and different types of fish oil based biodiesel. The environmental conditions investigated included different soil types (sand and gravel), different temperatures (constant 6�C, 20�C, and fluctuating between 6 and 20�C), moisture levels (from 2% to 12% GWC), fuel concentrations (from 500 to 20,000 mg fuel/kg soil) and nutrient dosages (0 or 300 mg N/kg soil). Microbial response times and growth phases were also investigated for different inoculum types. Conditions of 20�C, 300 mg N/kg soil, sand, ?4000 mg of fuel/kg soil and ?4% GWC were favorable for bioremediation, with a short lag phase lasting from one day to less than a week, and pronounced peaks of daily CO 2 production between week 2 and 3. At suboptimal conditions, all phases were extended and slow, however at low temperatures steady metabolization continued over a longer time. The relative importance of fungal and bacterial remediation varied between fuel types. Diesel fuel degradation was mainly due to bacterial activities while fish biodiesel degradation occurred largely by mycoremediation. For Syntroleum both bacterial and fungal remediation played key roles. Volatilization contributed up to 13% to overall contaminant removal. In soil columns, degradation was slower than in microcosms, due to an uneven concentration profile of contaminants, nutrients and oxygen with depth. In general, biodegradation showed promising results for soil remediation and the alternate fuel types were more biodegradable compared with conventional diesel fuel.
    • Seasonal Effects Of Frozen Soil On The Stiffness Of Bridge Piles

      Horazdovsky, Jacob E.; Hulsey, J. Leroy (2010)
      In the northern regions, the upper layer of soil is frozen throughout winter months. Soil stiffness can be expected to increase several orders of magnitude as it changes from thawed to frozen. Thus, pile foundation systems embedded in frozen soils are considerably stiffer during winter months when subjected to lateral loads. This thesis explores and quantifies stiffness change for 16 inch diameter steel jacketed, reinforced concrete pilings in seasonally frozen silt. Two test piles were driven 20 feet into silty soil at a site approximately 1.5 miles from Fairbanks, Alaska. Three quasi-static lateral load cyclic tests were conducted on the piles throughout the year; one in September when the soil was thawed, the other two in January and March with frost depths of 4.5 and 7.5 feet respectively. Soil temperatures ranged from thawed to -18 degrees C. The shear demand on the piles increased by over 400 percent. Depth to fixity changed from approximately 6 pile diameters (thawed) to less then 0.75 pile diameters (frozen).
    • Multi-Dimensional Frost Heave Modeling With Sp Porosity Growth Function

      Kim, Koui; Huang, Scott L. (2011)
      This dissertation presents a multi-dimensional frost-heave modeling with coupled heat transfer, moisture transfer, and mechanical analysis. A series of laboratory frost-heave tests was conducted to determine segregation potential (SP) values using the effect of cooling rate and overburden pressure in two different freezing modes. Regardless of the freezing mode, consistent SP values were obtained at the formation of the final ice lens. Continuous heave and water-intake measurements made it possible to determine the time at the formation of the final ice lens. The SP porosity growth function was developed using simulations of the growing ice lens and frozen fringe. The developed frost-heave model was verified by laboratory frost-heave tests in one dimension. The simulated temperature distribution and amount of heave were in good agreement with experimental values. The SP porosity growth function was then expanded to two dimensions to simulate the soil-pipeline interaction of an experimental buried chilled pipeline constructed in Fairbanks, Alaska in the early 2000s. A two-dimensional frost-heave simulation was conducted at the free-field area, where the influence of pipeline resistance in frozen ground was negligible. This model, which considers the effect of frozen soil creep on stress distribution due to temperature variation, analyzed the influence of stress fields on soil frost-heave susceptibility and deformation. Simulations of pipe displacement were conducted for two cases, with and without the use of the long-term creep characteristics of frozen soils. Using the long-term creep characteristics, the simulated result agreed well with the observed value, differing by only a few percentage points. However, without using long-term creep characteristics, the simulated pipe heave was approximately 75% of the observed heave because of an unrealistic stress buildup. Finally, the SP porosity growth function was expanded to predict soil-pipeline interaction around a frozen-unfrozen boundary. Temperature distribution was successfully predicted in both the pre-frozen soil and the unfrozen zones, as well as at the time when differential pipeline movement started. The developed three-dimensional frost-heave model could predict pipe movement and induced bending due to differential frost heave for a 20-year period.
    • The Hydrologic Regime At Sub-Arctic And Arctic Watersheds: Present And Projected

      Liljedahl, Anna K.; Hinzman, Larry (2011)
      The wetlands in the Arctic Coastal Plain, Northern Alaska, support a multitude of wildlife and natural resources that depend upon the abundance of water. Observations and climate model simulations show that surface air temperature over the Alaskan arctic coast has risen in recent history. Thus a growing need exists to assess how the hydrology of these arctic wetlands will respond to the warming climate. A synthesis study was conducted combining the analysis of an extensive field campaign, which includes direct measurements of all components of the water balance, with a physically-based hydrologic model forced by downscaled climate projections. Currently, these wetlands exist despite a desert-like annual precipitation and a negative net summer water balance. Although evapotranspiration is the major pathway of water loss, there are multiple non-linear controls that moderate the evapotranspiration rates. At the primary study site within the Barrow Environmental Observatory, shallow ponding of snowmelt water occurs for nearly a month at the vegetated drained thaw lake basin. Modeling studies revealed that the duration and depth of the ponding are only replicated faithfully if the rims of low-centered polygons are represented. Simple model experiments suggest that the polygon type (low- or high-centered) controls watershed-scale runoff, evapotranspiration, and near-surface soil moisture. High-centered polygons increase runoff, while reducing near-surface soil moisture and evapotranspiration. Soil drying was not projected by the end-of-the century but differential ground subsidence could potentially dominate the direct effects of climate warming resulting in a drying of the Arctic Coastal Plain wetlands. A drier surface would increase the susceptibility to fire, which currently is a major part of the Alaskan sub-arctic but not the arctic landscape. High quality pre- and postfire data were collected in the same location in central Seward Peninsula, uniquely documenting short-term soil warming and wettening following a severe tundra fire. Overall, this research concludes that arctic and sub-arctic watershed-scale hydrology is affected by changes in climate, surface cover, and microtopographic structures. It is therefore crucial to merge hydrology, permafrost, vegetation, and geomorphology models and measurements at the appropriate scales to further refine the response of the Arctic Coastal Plain wetlands to climate warming.
    • Characterizing the berthing load demand at Alaska Department of Transportation and Public Facilities Ferry Landings

      Hutchinson, Jonathan; Metzger, Andrew; Hulsey, Leroy; Dong, YongTao (2011-08)
      This report provides design guidelines and recommendations for side-berthing loads on ferry landing structures. Berthing loads on ferry berthing structures are not well understood due to a lack of information and research for ferry class vessels. The load criteria for the design of ferry berthing structures are thus often based on a number of assumptions, often leading to uneconomical or unreliable structures. The Alaska Department of Transportation (AKDOT&PF) recognizes the need for an improved information base on berthing loads from ferry class vessels, for the design and operation of future facilities within the Alaska Marine Highway System (AMHS). This study involves a one year empirical investigation into side-berthing loads at the Auke Bay ferry landing located in Juneau, Alaska. Measurements of fender displacement, approach velocity, and pile strain were used to determine berthing loads from scheduled berthings from four different vessels. Measured parameters were analyzed statistically, and used to establish distributions and design recommendations for berthing energy, force, velocity, and berthing coefficient based on reliability theory. This study provides an assessment of load criteria currently used by the AK DOT&PF Marine Department, as well as design load recommendations for both service and ultimate side-berthing loads from ferry class vessels.
    • Detecting Methane Ebullition In Winter From Alaskan Lakes Using Synthetic Aperture Radar Remote Sensing

      Engram, Melanie J.; Walter, Katey (2012)
      Methane (CH4) is a greenhouse gas with a high radiative forcing attribute, yet large uncertainties remain in constraining atmospheric CH4 sources and sinks. While freshwater lakes are known atmospheric CH4 sources, flux through ebullition (bubbling) is difficult to quantify in situ due to uneven spatial distribution and temporally irregular gas eruptions. This heterogeneous distribution of CH4 ebullition also creates error when scaling up field measurements for flux estimations. This thesis reviews estimates of CH4 contribution to the atmosphere by freshwater lakes presented in current literature and identifies knowledge gaps and the logistical difficulties in sampling CH 4 flux via ebullition (bubbling). My research investigates various imaging parameters of space-borne synthetic aperture radar (SAR) to constrain current CH4 emissions from northern lakes. In a GIS spatial analysis of lakes on the northern Seward Peninsula, Alaska, comparing field data of ebullition to SAR, I found that SAR L-band backscatter from lake ice was high from lakes with CH4 bubbles trapped by lake ice and low from lakes with low ebullition activity. The 'roughness' component of a Pauli polarimetric decomposition of quad-pol SAR showed a significant correlation with the percentage of lake ice area containing CH4 bubbles and with CH4 ebullition flux. This indicates that the mechanism of SAR scattering from ebullition bubbles trapped by lake ice is single bounce. I conclude that SAR remote sensing could improve our ability to quantify lake ebullition at larger spatial scales than field measurements alone, could offer between-lake comparison of CH 4 ebullition activity, and is a potential tool for developing regional estimations of lake-source CH4.
    • Permafrost Settlement Caused By Climate Warming In Alaska And The Estimation Of Its Damage Costs For Public Infrastructure

      Hong, Eunkyoung; Trainor, Sarah; Colt, Stephen; Perkins, Robert; Walsh, John (2012)
      Climate models and studies indicate that the changes in the northern latitudes will be serious and accelerated. Climate warming may impact structures in the northern latitudes through permafrost settlement affecting the performance of infrastructure and increasing costs for maintenance. The material presented is organized in three main chapters. Chapter 1 describes the motivation for the research. Chapter 2 addresses the permafrost settlement hazard in Alaska. I developed the Permafrost Settlement Hazard Index, which considered anticipated climate warming and ecological characteristics which regulate permafrost settlement. I found that the discontinuous permafrost region is at more risk due to permafrost settlement than other regions of Alaska. I also found that the correlation that the areas with high settlement hazard value have higher road maintenance costs. Chapter 3 is an estimate of damage cost caused by permafrost settlement related to climate warming in the field of public infrastructure. I concluded that climate warming may add about $106 million annually from 2010 to 2050 to annual costs for public infrastructure in Alaska. This amount of damage cost is the relative size of damage cost that is caused by climate warming. In order to understand the broader idea of adaptation methods, a case study of Alaska roads for discontinuous permafrost regions is presented in Chapter 4. Some alternative construction methods were chosen as adaptation methods. Then, the comparison of the cost effectiveness of each adaptation method was shown to identify the most economical option when the cost estimation includes the effect of the additional permafrost settlement caused by climate warming. I concluded that pre-thaw method was the most cost effective method. I also recommended Air-Cooled Embankment on a condition that coarse rocks are available to create a convection cell. Chapter 5 summarizes the research and indicates possibilities for future research directions. I employed an interdisciplinary approach combining engineering knowledge with environmental impact assessments, utilizing economic tools in estimating damage costs, and analyzing the cost effectiveness of adaptation options to climate induced permafrost settlement. Nevertheless, this interdisciplinary analysis was not intended as a civil engineer design but intended for these economic estimates.
    • Winter Precipitation Depths Across The North Slope Of Alaska Simulated From The Weather Research And Forcasting Model And Snowtran-3D

      Byam, Sarah Jean; Cherry, Jessica E.; Toniolo, Horacio; Kane, Douglas (2012)
      Accurately predicting snow distribution and blowing snow conditions in the Arctic is critical to the design of ice road construction and maintenance as well as for predicting water supplies and runoff during snowmelt, estimating the cost of snow removal, and forecasting tundra travel conditions. A current atmospheric model used by both the operational weather prediction and research communities is the Weather Research and Forecasting model. However, the built-in snow schemes in the model neglect redistribution of snow via wind, one of the key processes in snow pack evolution. This study will involve three parts: (1) diagnostic of the differences in the current snow schemes of the model, (2) evaluation of the model's snow schemes as compared to observational data, and (3) asynchronous coupling of the SnowTran-3D to model predictions using a simple algorithm. The approach provides a simple method for the prediction of snow distribution, improving the realism of current snow distribution models, and will be easily employable for both operational and research applications.
    • Modeling Biosorption Of Cadmium, Zinc And Lead Onto Native And Immobilized Citrus Peels In Batch And Fixed Bed Reactors

      Chatterjee, Abhijit; Schiewer, Silke; Barnes, Dave; Johnson, Ron; Tainor, Tom (2012)
      Biosorption, i.e., the passive uptake of pollutants (heavy metals, dyes) from aqueous phase by biosorbents, obtained cheaply from natural sources or industrial/agricultural waste, can be a cost-effective alternative to conventional metal removal methods. Conventional methods such as chemical precipitation, membrane filtration or ion exchange are not suitable to treat large volumes of dilute discharge, such as mining effluent. This study is a continuation of previous research utilizing citrus peels for metal removal in batch reactors. Since fixed bed reactors feature better mass transfer and are typically used in water or waste water treatment using ion-exchange resins, this thesis focuses on packed bed columns. A number of fixed bed experiments were conducted by varying Cd inlet concentration (5-15 mg/L), bed height (24-75 cm) and flow rate (2-15.5 ml/min). Breakthrough and saturation uptake ranged between 14-29 mg/g and 42-45 mg/g respectively. An empty bed contact time of 10 minutes was required for optimum column operation. Breakthrough curves were described by mathematical models, whereby three popular models were shown to be mathematically identical. Citrus peels were immobilized within an alginate matrix to produce uniform granules with higher uptake capacity than raw peels. All breakthrough curves of native and immobilized peels were predicted using external and intra-particle mass transfer resistances from correlations and batch experiments, respectively. Several analogous mathematical models were identified; other frequently used models were shown to be the approximate derivatives of a single parent model. To determine the influence of competing metals, batch and fixed bed experiments were conducted in different binary combinations of Pb, Cd, Zn and Ca. Equilibrium data were analyzed by applying competitive, uncompetitive and partially competitive models. In column applications, high affinity Pb replaced previously bound Zn and Cd in Pb-Zn and Pb-Cd systems, respectively. However, the Cd-Zn system did not show any overshoot. Calcium, which is weakly bound, did not affect target metal binding as much as other metals. Saturated columns were desorbed with 0.1 N nitric acid to recover the metal, achieving concentration factors of 34-129. Finally, 5 g of citrus peels purified 5.40 L mining wastewater.
    • Structural health monitoring of Klehini River bridge

      Xiao, Feng (2012-08)
      The objective of the research is to improve the safety of bridge structures in the state of Alaska through implementation of innovative structural health monitoring (SHM) technologies. The idea is to evaluate structural integrity and serviceability, and to provide reliable information for changing structural response, etc. of monitored bridges. Based on the finite element model's moving load analysis, modal analysis results and field inspection, this study was used to establish a bridge SHM system for a particular bridge including a preferred sensor layout, system integrator and instrumentation suitable for Alaska's remote locations with harsh weather. A variety of sensors were proposed to measure and monitor structural and environmental conditions to assist in the evaluation of the performance of the Klehini River Bridge. This system is able to provide more reliable information on the real structural health condition. It can be used to improve safe performance of this bridge. As a new safety and management tool, this SHM system will complement traditional bridge inspection methods. Implementation of an effective monitoring system will likely result in a reduction in inspection manpower, early detection of deterioration/damage, development of optimum inspection cycle and repair schedules before deterioration/damage grows to a condition where major repairs are required.
    • Investigation of thermal regimes of lakes used for water supply and examination of drinking water system in Kotzebue, Alaska

      Bendlova, Tereza; Arp, Christopher D.; Duffy, Lawrence K.; Schnabel, William E.; Barnes, David L. (2012-08)
      Many villages in Arctic Alaska rely on lakes for water supply, such as the Alaskan City of Kotzebue, and these lakes may be sensitive to climate variability and change, particularly thermal regimes and corresponding effects on water quality. Thus, I initiated a study of water supply lakes in Kotzebue to collect data for developing a model to hindcast summer thermal regimes. Surface (Tws) and bed (Twb) temperature data collected from two water supply lakes and two control lakes from June 22nd-August 28th 2011 showed a similar pattern in relation to air temperature (Ta) and solar radiation with more frequent stratification in the deeper lakes. The average Tws for all lakes during this period was 14.5°C, which was 3.4°C higher than Ta for the same period. I modeled Tws from 1985 to 2010 using Ta, and theoretical clear-sky solar radiation (TCSR) to analyze interannual variability, trends, and provide a baseline dataset. Similar to patterns in Ta for this period, I found no trend in mean Tws for the main lake used for water supply (Devil's Lake), but considerable variation ranging from 12.2°C in 2000 to 19.2°C in 2004. My analysis suggests that 44% of years during this 25 year period maximum daily Tws surpassed 20°C for at least one day. This hindcasted dataset can provide water supply managers in Kotzebue and other Arctic villages with a record of past conditions and a model for how lakes may respond to future climate change and variability that could impact water quality.
    • Initial Permafrost Engineering Research In Alaska

      Cysewski, Margaret Hope; Shur, Yuri (2013)
      Past permafrost engineering research and projects can aid modern permafrost engineering. The knowledge base of lessons learned among engineers is important, especially between generations of engineers, so history does not repeat itself Uncovering the history of permafrost engineering, and its compilation, summarization, and analysis, is beneficial for the Alaskan engineering community. This master's thesis is devoted to the early years of permafrost engineering in Alaska with projects carried out from the Gold Rush era to shortly after WWII. The projects include: thawing technology developed by gold miners, Alaska Highway road design and construction with its influence, and early comprehensive research by the Permafrost Division of the U.S. Army Corps of Engineers' St. Paul District, particularly the development of the test site, the Fairbanks Research Area, along Farmers Loop Road. Each of these projects has been successfully adapted to modern practices, laying the foundation of permafrost engineering.
    • An assessment of suspended sediment transport in Arctic Alaskan rivers

      Lamb, Erica K.; Toniolo, Horacio; Schnabel, William; Kane, Douglas (2013-05)
      Provided here is an initial assessment of suspended sediment transport in several rivers on the North Slope of Alaska. This study was divided into two parts: the Umiat project, which involved the Chandler, Anaktuvuk and Itkillik Rivers, and the NPR-A study, which considered Prince, Seabee and Fish Creeks, as well as a brief look at the lkpikpuk River, Otuk Creek, Judy Creek and the Ublutuoch River. Methods used included depth-integrated suspended sediment samples, grab samples, automatic pump-style samplers, discharge measurements, bed sediment grain size analysis and the inclusion of a variety of meteorological measurements from other projects. With slightly less than two years of data collection from May 2011 to September 2012, an initial analysis was completed. Suspended sediment rating curves developed for the Anaktuvuk and Chandler Rivers over the two-year study period revealed a strong correlation between suspended sediment concentration (SSC) and discharge. The most data was collected for the Anaktuvuk and Chandler Rivers; on these rivers, suspended sediment discharge was also analyzed, showing that over 90% of suspended sediment transport occurred during the spring melt period in 2011. Spring melt was not measured in 2012, so analysis was only completed for 2011.
    • Evaluating short rotation poplar biomass on an experimental land-fill cap near Anchorage, Alaska

      Byrd, Amanda G. (2013-05)
      Biomass energy has enjoyed a resurgence of scientific interest recently. Indeed, biomass may have the potential to replace diesel fuel as the primary source of heating in some parts of Alaska. In addition to forest biomass, short rotation crops have been considered as a sustainable source of woody biomass, and a potential sink for carbon sequestration. In this study, Populus balsamifera was evaluated as a short rotation crop for use as an energy source in Southcentral Alaska. Growth and yield rates were measured on an established P. balsamifera stand under a two-year rotation, yielding an annual biomass production of 5,530 kg/ha/yr. A fertilizer application study was conducted and demonstrated no effect on growth. Energy content of P. balsamifera measured 19,684 kJ/Kg, with a total energy yield of 217,715 MJ/ha after two years. Carbon sequestered below ground was estimated at least 5,338 kg/ha. Biomass may not be carbon neutral, but the carbon emitted from burning biomass is at least partially renewable. With use in high-efficiency boilers, there is potential for biomass to offset costs, and even save money by displacing diesel heating fuel.
    • Permafrost geosystem assessment at the Beaver Creek Road experimental site (Alaska Highway, Yukon, Canada)

      Stephani, Eva; Shur, Yuri; Fortier, Daniel; Kanevskiy, Mikhail; Connor, Billy (2013-05)
      An experimental site testing a range of engineering techniques for mitigating permafrost degradation along the Alaska Highway has been established in 2008 at Beaver Creek (Yukon, Canada). Based on the hypothesis that permafrost has a distinctive sensitivity to climate and terrain conditions at a local scale, a geosystem approach, which considers a set of components (e.g. permafrost, embankment, vegetation, hydrology and hydrogeology) and accounts for dynamics within a system, was applied to obtain a better understanding of local permafrost conditions and changes within the system. Therefore, this assessment, for ultimately measuring performance of the mitigation techniques, integrated the permafrost conditions, in terms of cryostratigraphic units and soil properties, with local climate, natural terrain and embankment conditions. The author, who participated in the site establishment, its baseline investigations and monitoring programs, presents here the baseline geosystem studies at the Beaver Creek Road Experimental Site with an emphasis on permafrost.
    • Characterization and implementation of stress dependent resilient modulus of asphalt treated base for flexible pavement design

      Li, Peng; 鹏 李; Liu, Juanyu; Connor, William; Zhang, Xiang; Shur, Yuri; Saboundjian, Stephan (2013-08)
      Asphalt treated base (ATB) is the most commonly used type of stabilized material in pavements because of material availability and relatively low cost in Alaska. The treatment enhances the material's properties to overcome deficiencies in some marginal materials. Resilient modulus (MR) of these materials is an essential pavement design input. Currently, in the Alaska Flexible Pavement Design (AKFPD) Manual, MRS of ATBs were back calculated using testing results of falling weight deflectometer (FWD). There is a need for an accurate laboratory characterization of these materials. In this study, the MRS of hot asphalt treated base (HATB), emulsifed asphalt treated base (EATB), foamed asphalt treated base (FATB), and a mixture of reclaimed asphalt pavement (RAP) and D-1 aggregate at a 50: 50 ratio (RAP 50:50) were measured using repeated triaxial tests. D-1 granular materials used for base course construction were collected from three regions in Alaska. HATB specimens were compacted using Superpave gyratory compactor and three binder contents were used: 2.5%, 3.5% and 4.5%. EATB and FATB specimens were compacted according to ASTM D1557 and three residual binder contents were used: 1.5%, 2.5% and 3.5%. RAP 50:50 was also compacted according to ASTM D1557 and no additional additives were added. MR was measured at three temperatures (i.e. -10°C, 0°C, 20°C for HATB, EATB and FATB; -10°C, -2°C, 20°C for RAP 50:50). The stress-dependent property of MR was successfully characterized by the modified universal soil model, in which the MR was expressed as a function of bulk stress (θ) and octahedral shear stress (τoct). Generally, MR increased with an increase of θ and decreased with an increase of τoct. Stress-dependent patterns of each type of ATB were analyzed and discussed. Predictive equations for MR were developed for all types of ATBs investigated in this study. The equations were based on the modified universal soil model. The material properties (i.e. binder content and percentage fracture surface), temperature and the interactions among them were incorporated into equations. The developed predictive equations had very high coefficient of determination (R²). The R² s of equations HATB_10, EATB_10, FATB_10 and RAP_9, in which the influencing factors and second order interactions among factors were included, were all greater than 99%. These equations can be also used to estimate nonlinear elastic constants of ATBs in the modified universal soil model (i.e. k₁, k₂ and k₃). The stress dependent property of MR was incorporated into pavement structural analysis using the finite element method (FEM) program Abaqus through user defined material that was programmed in the user subroutine. Comparisons were made between pavement responses obtained from nonlinear FEM and traditional linear elastic layered system. The representative MR of ATBs were determined and recommended based on the equivalent critical pavement response of the typical Alaska flexible pavement structure. Predictive equations were developed to estimate the critical pavement responses. The equations were developed through regression analyses using a database generated from 16,848 nonlinear pavement FEM analyses, which covered a variety of pavement structure combinations. These nonlinear pavement analyses were implemented through the function of a parametric study provided in Abaqus FEM package. In total 9 independent variables were included, which were the thickness of the surface course, base course, and subbase, moduli of HMA, subbase and subgrade, and nonlinear elastic constants of ATB (i.e. k₁ k₂ k₃) in the MR model. The interactions among these variables were also included. The R²s of predictive equations were at least 0.9725. The predictive equations can be used for routine pavement analysis and design purposes.
    • Response of pile-guided floats subjected to dynamic loading

      Quan, Zhili; 权致力; Chen, Gang; Metzger, Andrew; Hulsey, Leroy (2013-12)
      Pile-guided floats can be a desirable alternative to stationary berthing structures. Both floats and guide piles are subjected to time varying (dynamic) forces such as wind-generated waves and impacts from vessels. There is little design information available concerning the dynamic load environment to which the floats will be subjected. So far, the most widely acceptable method used in offshore structure design is the Kinetic Energy Method (KEM). It is a simplified method that is based on the conservation of energy. This approach is straightforward and easy to implement. However, in spite of its simplicity and straightforwardness, the method lacks accuracy. The intent of this project is to develop a rational basis for estimating the dynamic response of floating pile-guided structures, providing necessary insight into design requirements of the guide-piles. In this study, the Dynamic Analysis Method (DAM) will be used to model the dynamic responses of the system. MATLAB codes are written to help calculate the analytic and numerical values obtained from the dynamic models. For the purpose of validation, results from the two systems should be compared to a comprehensive dynamic analysis model created with the ANSYS AQWA Software.
    • A review of oil spill history and management on the North Slope of Alaska

      Davila, Amanda (2013-12)
      Alaska has an abundance of natural resources including oil, natural gas and coal. It is critical to minimize the occurrence of oil spills to ensure protection of Alaska's people and the environment. The objective of this project is twofold. One is to provide a quantification of the number of spills on the North Slope (NS) as well as the number of contaminated sites that are generated, describe the regulatory requirements for the Arctic zone, and discuss cleanup methods. Second is to describe the ADEC regulations as they pertain to terrestrial oil spills. The region of study begins north of Alyeska's Pump Station 4 at the Dalton Highway milepost 270, TAPS 144, north to the Beaufort Sea, encompassing all oil related operations. This review excludes spills at villages (not related to oil field operations), and releases to the atmosphere (e.g., halon, propane). Additionally, spills at formally used defense sites (FUDS) and long range radar sites are also excluded from this study. Spills that result in long term monitoring and cleanup are managed as contaminated sites. The data reveals that the majority of contaminated sites have been cleaned up with no institutional controls in place. The number of spills on the North Slope is consistent with activity. The time during the peak oil is when there are a higher number of spills. Over time, as the oil production and activity decline, so do the number of spills with a few exceptions. The decline in oil production has limited activity and growth on the NS.
    • Assessment of contaminant concentrations and transport pathways in rural Alaska communities' solid waste and wastewater sites

      Mutter, Edda Andrea; Schnabel, William; Barnes, David; Duddleston, Khrys; Duffy, Lawrence; Hagedorn, Birgit (2014-05)
      Waste management practices currently employed in many rural Alaska communities are potentially contributing to human and environmental health impacts, and this problem may be exacerbated with the anticipated warming climate. For rural communities, factors that contribute to insufficient waste management practices include climate and environmental conditions, limitation of federal and state capital funding for construction, and the continuing financial burden associated with providing adequate operations and maintenance. As a response, federal regulatory exemptions are granted for construction and design of solid waste sites and limited state regulations are in place for wastewater discharge criteria. Due to the absence of proper site assessment and monitoring, very little is known about the fate and transport of point source pollutants arising from these wastewater and solid waste sites. Moreover, these fate and transport processes may be susceptible to changes resulting from human activity or a warming climate. Thus, this knowledge gap associated with waste-related pollutants in rural Alaska could obscure potential threats to human and environmental health by concealing impacts to freshwater systems. This research was intended to achieve a better understanding of rural Alaska waste leachate compositions by evaluating contaminant prevalence and diversity, quantifying contaminant concentration levels, and evaluating their potential migration into nearby freshwater systems. Over the course of three years, waste sites at five rural Alaska communities were sampled and tested for heavy metals, organic constituents, and microbial indicator organisms. The purpose of the analysis was to evaluate the impact of waste sites on soil, surface, and subsurface waters in the vicinity of the sites. The resulting findings are assembled into three chapters describing 1) the assessment of heavy metal leachate in rural Alaska solid waste sites, 2) the identification of new emerging organic pollutants in rural Alaska waste sites, and 3) the partitioning and transport behavior of pathogen indicator organisms in cold regions. The research outcome of E.coli and Enterococcus sp. were observed in waste impacted water and soil samples, heavy metal migration into nearby freshwaters, and pharmaceuticals, phthalates, and benzotriazole in waste impacted water samples. The research findings highlight the need to apply state regulations to remove potentially hazardous components from rural Alaska wastewater and municipal solid waste streams. Additionally, there is a need to establish effective solid waste and wastewater leachate monitoring and assessment strategies for active and closed rural Alaska waste sites.