• A Targeted Approach to High-Volume Fly Ash Concrete Pavement (Phase I)

      Du, Sen; Shi, Xianming (2018-12)
      Unlike the conventional method of admixing nanomaterials directly in fresh concrete mixture, a more targeted approach was explored. Specifically, nanomaterials were used to improve the interface between coarse aggregate and cement paste, by coating the coarse aggregate with cement paste that contained graphene oxide or nanosilica. Using coated coarse aggregates, the mechanical and transport properties of high-volume fly ash (HVFA) concrete were tested to evaluate the effect of nanomaterial coating on the interface transition zone of concrete. The compressive and splitting strengths of HVFA concrete at 3, 7, 14, and 28 days and the water sorptivity and chloride migration coefficient at 28 days were studied. Results show that nanomaterial-coated coarse aggregate can improve the transport properties of HVFA concrete by reducing permeability. However, no improvement was seen in the compressive and splitting strengths when incorporating coated coarse aggregate, compared with direct mixing of nanomaterials in fresh concrete. Resistance to freezing/thawing cycles and scanning electron microscope/energy dispersive X-ray spectroscopy of concrete samples were also investigated to obtain a more comprehensive and mechanistic understanding of nanomaterial coating.
    • TEST College of Engineering & Mines 9/25/17

      CHISUM (2017-09)
      TEST College of Engineering & Mines 9/25/17
    • TEST College of Liberal Arts 9/25/17

      CHISUM (2017-09)
      TEST College of Liberal Arts 9/25/17
    • TEST College of Natural Sciences and Mathematics 9/25/17

      CHISUM (2017-09)
      TEST College of Natural Sciences and Mathematics 9/25/17
    • TEST Master's Projects 9/25/17

      CHISUM (2017-09)
      TEST Master's Projects 9/25/17
    • Testing and analysis of a ground source heat pump in Interior Alaska

      Garber-Slaght, Robbin; Das, Debendra K.; Marsik, Tomas; Lin, Chuen-Sen (2019-08)
      Ground source heat pumps (GSHPs) can be an efficient heating and cooling system in much of the world. However, their ability to work in extreme cold climates is not well studied. In a heating-dominated cold climate, the heat extracted from the soil is not actively replaced in the summer because there is very little space cooling. A ground source heat pump was installed at the Cold Climate Housing Research Center (CCHRC) in Fairbanks, Alaska with the intent to collect data on its performance and effects on the soil for at least ten years. Analysis shows GSHPs are viable in the Fairbanks climate; however, their performance may degrade over time. According to two previous finite element models, the CCHRC heat pump seems to reach equilibrium in the soil at a COP of about 2.5 in five to seven years. Data from the first four heating seasons of the ground source heat pump at CCHRC is evaluated. The efficiency of the heat pump degraded from an average coefficient of performance (COP) of 3.7 to a mediocre 2.8 over the first four heating seasons. Nanofluids are potential heat transfer fluids that could be used to enhance the heat transfer in the ground heat exchanger. Improved heat transfer could lower installation costs by making the ground heat exchanger smaller. A theoretical analysis of adding nanoparticles to the fluid in the ground heat exchanger is conducted. Two nanofluids are evaluated to verify improved heat transfer and potential performance of the heat pump system. Data from the CCHRC heat pump system has also been used to analyze a 2-dimensional finite element model of the system's interaction with the soil. A model based on the first four years of data is developed using Temp/W software evaluates the ground heat exchanger for a thirty-year period. This model finds that the ground heat exchanger does not lower the ground temperature in the long term.
    • Testing of syntroleum fuels in diesel power plants suitable for Alaska

      Telang, Aseem Uday (2005-05)
      Sulfur free synthetic diesel fuels can be produced using Gas to Liquid (GTL) technology, and may prove useful as a substitute for conventional diesel fuels when oil reserves are depleted. These fuels also should produce lower emissions, as the sulfur content is near zero. However, this fuel has significantly different combustion properties than conventional diesel fuels, and may require injection timing adjustments to burn cleanly. This paper presents a comparison of the exhaust emissions from synthetic diesel fuels, manufactured by the Syntroleum Corporation, and conventional diesel fuel. Documented emissions are the total hydrocarbons, carbon monoxide and oxides of nitrogen. Effects of injection timing on exhaust emission and brake specific fuel consumption (BSFC) are also discussed.
    • Tests and analysis of geogrids as base-reinforcing materials

      Fu, Xuemin (1998)
      A quantitative assessment of geogrids as base reinforcing material in paved roads is clearly necessary when a design is needed and decisions are to be made as a consequence. Two full scale single wheel load tests were conducted to determine the performance of geogrids as base reinforcing materials in paved roads. These two full scale tests were set up with different base thicknesses, material properties, loading conditions and geogrids. Load, speed, and direction of a test cart were controlled with a computer. Although many types of instruments were installed, measurements of vertical deformation of the pavement surface proved to be the most useful. The Traffic Benefit Ratio (TBR), defined as the ratio of the life of a reinforced section to the life of a similar unreinforced section, was used as a primary design parameter. Comparisons between reinforced and unreinforced bases are presented. The parameters used for comparison were permanent vertical deformation, number of repetitions to failure, tire load, and thickness of base course. Test results showed that the maximum TBR for a Tensar BR2 geogrid was 10. This TBR was obtained at a design deformation of 1.0 inch with 2 inches of asphalt over 10 inches of base over a CBR 3 clay subgrade. TBR's for other conditions ranged between 1 and 10. A design reference chart is presented for using Tensar BR1 and BR2 Geogrids.
    • The effects of scale and spatial heterogeneities on diffusion in volcanic breccias and basalts: Amchitka, Alaska

      Benning, Jennifer Lyn; Barnes, David; Kelley, John; Perkins, Robert; Schnabel, William (2008-12)
      Aqueous phase diffusion of molecules in fractured crystalline rock can play a dominant role in the fate and transport of contaminants, particularly if advective flows are very slow. The importance of the role of diffusion, typically a very slow process, also becomes an important mechanism to consider if the contaminants are long-lived in the subsurface, and thus their fate and transport must be considered over very long time-scales. Owing to the inherently heterogeneous nature of the subsurface, quantification of diffusive transport in the subsurface is extremely complex. The main objective of this study was to investigate the effects of the inherent heterogeneities of the subsurface on the diffusive transport of radionuclides, with a focus on the former underground nuclear test site at Amchitka Island, Alaska. Commonly, the through-diffusion experiment is utilized to estimate transport parameters, the diffusivity and the effective porosity, for porous media samples. The available methods of mathematically deriving these parameters from these experiments are generally known to be subjective and unreliable. Thus, one phase of this study applied the results of through- diffusion experiments to investigate the applicability of the available solution methods to derive these parameters. The results indicated that a semi-analytical solution provided the most reliable parameter estimations. This knowledge was then applied to studies designed to understand the impacts of scale and spatial heterogeneities on diffusion at the study site. Multiple Amchitka Island core samples, both from the same and from various geologic layers, in varying sizes were analyzed in the laboratory via tracer-based and electrical methods, to quantify the diffusive properties and the effects of heterogeneities for Amchitka Island. The studies indicated that the transport properties for Amchitka Island are widely varying, by orders of magnitude, and are indicative of a geologically layered subsurface system; these results are extremely important for the long-term modeling of the fate and transport of radionuclides at Amchitka Island. Finally, in light of these studies, the question of long-term stewardship for the Amchitka Island test site was investigated and recommendations were provided, with the goal of providing an improved plan for the long-term monitoring and management of the site.
    • 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.
    • The Influence Of Soil Cryostructure On The Creep And Long Term Strength Properties Of Frozen Soils

      Bray, Matthew Thomas (2008)
      The time dependent mechanical properties of ice-rich frozen soils were studied in relation to their cryostructure. The CRREL permafrost tunnel was the primary source of the studied ice-rich soils. Mapping of the permafrost geology of the main adit of the CRREL permafrost tunnel was performed and reinterpreted in the context of a cryofacial approach. The cryofacial approach in based on the concept that cryostructure is dependent on how a soil was deposited and subsequently frozen. Three main soil cryostructures were determined to represent the main aspects of the permafrost geology. Soils with micro-lenticular cryostructure represent the original ice-rich syngenetic permafrost formed during the Pleistocene. Reworked sediment due to fluvial-thermal erosion resulted in soils with massive cryostructure and soils with reticulate-chaotic cryostructure. Ice bodies within the tunnel include syngenetic wedge ice and secondary thermokarst cave ice deposits. A testing program for determining the time dependent mechanical properties, including the creep and long term strength characteristics of permafrost in relation to soil cryostructure, was performed. Undisturbed frozen soils include silty soil containing micro-lenticular, reticulate-chaotic, and massive cryostructure. Remolded silt from the tunnel was used to create artificial samples with massive cryostructure for comparison to the undisturbed frozen soils. In addition to frozen silt, undisturbed ice facies were tested. These included syngenetic wedge ice, Matanuska basal glacial ice, and Matanuska glacial ice. Testing methods include uniaxial constant stress creep (CSC) tests and uniaxial relaxation tests. It was shown that soil cryostructure and ice facies influences the creep and long term strength properties of frozen soils. It was shown that remolded soils provide non-conservative creep and long term strength estimates when extrapolated to undisturbed frozen soils. Minimum strain rate flow laws show that at low stresses, undisturbed soils creep at a faster rate than remolded soils. At high stresses, frozen soils creep at a faster rate than ice. It was also shown that the unfrozen water content influences the mechanical properties of frozen soils and that the unfrozen water content is influenced by soil cryostructure. Through cryostructure, the permafrost geology is related to the time dependent mechanical properties of frozen soils.
    • The mechanics of diamond core drilling of rocks

      Wang, Zhengwen W. (1995)
      In an attempt to study the mechanics of diamond core drilling in rocks, an investigation on rock drillability was conducted at the University of Alaska Fairbanks. A series of drilling and coring tests was conducted on six types of rock using several different diamond bits. Factors involved in a diamond coring and drilling process such as weight-on-bit, rotational speed, and rock type were identified and the effects of those parameters were experimentally evaluated based on the penetration rate, applied torque, and specific energy. Statistical techniques were used to design the drilling tests and to develop drilling models. Fundamentals of rock failure mechanics in relation to rock drilling were reviewed. Several existing rock drilling models were also examined with the data from this study. Results indicated that all of the three drilling parameters, i.e., the penetration rate, applied torque, and specific energy, were significantly affected by the weight-on-bit and rock type. The penetration rate of a bit was also affected by the rotational speed. The effects of the rotational speed on the applied torque and specific energy, however, were found to be insignificant. It was also found that the theoretical models can be used to predict the maximum effective weight-on-bit and penetration rate. Among the four theoretical models examined, the elastic model predicted the most accurate penetration rate. The maximum effective weights-on-bit predicted by the plastic model and the two fracture models, however, were close to each other and in agreement with the experimental observation. Statistical models developed in this study were used to predict the penetration rate in the Rock Drilling under the Greenland Ice Sheet project. The variation between the predicted value and the actual value was less than 10%.
    • The Physical Dynamics Of Patterned Ground In The Northern Foothills Of The Brooks Range, Alaska

      Overduin, Pier Paul; Kane, Douglas L. (2005)
      Periglacial landforms, called patterned ground, change the vegetation, microtopography and organic content of the surface soil horizons. Because they are uniquely products of the periglacial environment, changes in that environment affect their distribution and activity. As surface features, they mitigate heat and mass transfer processes between the land and atmosphere. For environmental change detection, the state of the soil and active layer must be monitored across temporal and spatial scales that include these features. It is suggested here that changes in the state of the active layer due to the abrupt spatial changes in surface soil character lead to changes in the distribution of soil components, soil bulk thermal properties and the thermal and hydrological fluxes result. The determination of soil volumetric moisture content using the relative dielectric permittivity of the soil is extended to include live and dead low-density feathermoss. High temporal resolution monitoring of the thermal conductivity of mineral and organic soil horizons over multiple annual cycles is introduced, along with a new method for analyzing the results of transient heat pulse sensor measurements. These results are applied to studies of frost boils and soil stripes in the northern foothills of the Brooks Range in Alaska. Active layer ice dynamics determine the thermal properties of the frozen soil in the frost boil pedon. Annual heaving and subsiding of the ground surface reflects these changes in ice content and can be used to estimate active layer ice content as a function of depth. These estimates correlate with bulk soil thermal diffusivity, inferred as a function of depth from temperature data. Differences in soil thermal diffusivity determine thaw depth differences between frost boil and tundra, and between wet and dry soil stripes. For the latter, deeper subsurface flow through the high organic content wet stripes is delayed until mid-summer; when it does occur, it has a large component normal to the hillslope as a consequence of differential heave. Dynamics in these periglacial landforms can be identified from surface features, highlighting the potential for scaling up their net effect using remote sensing techniques.
    • Theoretical And Experimental Analysis Of Two-Phase Closed Thermosyphons

      Xu, Jianfeng; Goering, Douglas J. (2008)
      This work presents an analytical and numerical model of a long inclined two-phase closed thermosyphon, known as a hairpin thermosyphon, which is representative of a new configuration for thermosyphons used in arctic applications. A laboratory experiment and a full scale road experiment along with associated modeling are described in detail. The laboratory experiment studies the condensation heat transfer performance of carbon dioxide inside the thermosyphon condenser under conditions of limited heat flux. The operating condition is not far from the critical point for carbon dioxide, which has a significant impact on the condensation heat transfer. An experimental correlation is developed to predict the carbon dioxide condensation heat transfer performance under these specific conditions. The full scale road experiment studies the overall performance of hairpin thermosyphons under actual field conditions. The model is a quasi one-dimensional formulation based on two-dimensional two-phase flow simulations at each cross section. The proposed model is useful for predicting steady state system operating characteristics such as pressure, temperature, liquid film thickness, mass flow rate, heat flow rate, etc., at local positions as well as over the entire system. The comparison of the modeling predictions with both laboratory and field experiments showed a strong correlation between modeling predictions and experimental results.
    • Thermal analysis and cold start performance of automotive emission systems

      Kumar, Sumit (2002-08)
      Automotive exhaust emission regulations are becoming stricter due to increasing awareness of the hazardous effects of exhaust emissions. The main challenge to comply with the EPA regulations is to reduce the emissions during cold start, because catalytic converters are ineffective until they reach a 'light-off' temperature - the temperature at which the converter starts reducing 50 % of emissions. A thermal model of a catalytic converter is presented which reduces the light-off time and significantly reduces the concentration of exhaust gas emissions. This thesis describes a numerical model of the catalytic converter, which is used to predict catalytic converter performance during cold-starts. Simulations were carried out using a finite element software - Abaqus, to study the catalytic converter performance at various temperatures. After analyzing thermal models for both - uniform heat distribution and cost effectiveness, a heat source of 90 W was chosen for a three-heater configuration (30 W each) to pre-heat the converter. A reduction in the concentration of emissions by a factor of 4 to 6 were recorded as a result of vehicle simulation with this thermally designed catalytic converter. ADVISOR (Advanced Vehicle Simulator), a vehicle simulator, was used to calculate 'engine-out emissions.'
    • Thermal analysis on permafrost subsidence on the North Slope of Alaska

      Agrawal, Neha Dinesh; Patil, Shirish; Chen, Gang; Dandekar, Abhijit; Bray, Matthew (2015-11)
      One of the major problems associated with the oil fields on the North Slope of Alaska is thawing permafrost around producing oil wells. In these wells, the heat from the producing well fluid gradually thaws the permafrost. This thawing in turn destroys the bond between the permafrost and the casing and causes instability that results in permafrost subsidence which further causes subsidence of the soil surrounding the wellbore and, subjects the casing to high mechanical stresses. The above problem has been addressed by several engineers, and several preventive measures, such as controlling the subsidence by refrigeration or by insulation of the wellbore, have been analyzed. Understanding the thermal behavior of the permafrost is imperative to analyzing permafrost subsidence and providing preventative measures. The current project focuses on building a scaled-down axi-symmetric model in FLAC 7.0 that will help us understand the thermal behavior (i.e., the heat input to the permafrost interval due to hydrocarbon production) and temperature distributions that result in permafrost subsidence. The numerical analysis estimated the thaw influence of steam injection used for heavy oil recovery and its effect on the area around the wellbore for 10 years. The developed model was compared with Smith and Clegg (1971) axi-symmetric model and COMSOL model and correlations of thaw radius and wellbore temperatures were obtained for different types of soils. Heat transfer mitigation techniques were also attempted which are discussed in the report further.
    • Thermal and fluid dynamic analysis of gas-to-liquids transportation through Trans Alaska Pipeline System

      Nerella, Sirisha (2002-08)
      Gas-to-liquids (GTL) technology involves the conversion of natural gas to liquid hydrocarbons. In this study, theoretical studies have been presented to determine the feasibility of transporting GTL products through the Trans-Alaska Pipeline System (TAPS). To successfully transport GTL through TAPS, heat loss along the route must be carefully determined. This study presents heat transfer and fluid dynamic calculations to evaluate this feasibility. Because of heat loss, the fluid temperature decreases in the direction of flow and this affects the fluid properties, which in turn influence convection coefficient and pumping power requirements. The temperature and heat loss distribution along the pipeline at different locations have been calculated. Fairly good agreement with measured oil temperatures is observed. The powers required to pump crude oil and GTL individually, against various losses have been calculated. Two GTL transportation modes have been considered; one as a pure stream of GTL and the second as a commingled mixture with crude oil. These results show that the pumping power and heat loss for GTL are less than that of the crude oil for the same volumetric flow rate. Therefore, GTL can be transported through TAPS using existing equipment at pump stations.
    • Thermal Properties of Metal Stud Walls

      Zarling, John P.; Braley, W. Alan; Strandberg, James S.; Bell, Scott V. (1984-07)