• Experimental Study Of Adsorbed Cation Effects On The Frost Susceptibility Of Natural Soils

      Darrow, Margaret Marie; Huang, Scott; Shur, Yuri (2007)
      Frost heaving is ubiquitous throughout cold regions, causing damage to building foundations, roads, airfields, railways, utilities, and pipelines. Out of the voluminous body of research conducted over the last 80 years, few studies investigated the mineral surface effects on frost heaving. These previous studies were conducted nearly 50 years ago with rudimentary equipment and on homogeneous and artificial soils that have limited applicability to actual field conditions. The purpose of the research presented here is to investigate the adsorbed cation effects on the frost susceptibility of natural soils through experimental testing. A comprehensive suite of laboratory experiments was conducted on five natural heterogeneous soils, including the preparation of divalent and monovalent cation-treated samples. Experimental testing included measurements of engineering index properties, chemical properties, clay content and mineralogy, soil-moisture characteristic curves, unfrozen water content, zeta potential, and frost heave testing. Frost heave tests were conducted using a state-of-the-art laboratory system that demonstrates high repeatability. Soil-moisture characteristic---soil freezing characteristic (SMC-SFC) relations were developed for the five natural soils over an unprecedented range of measurements and using a new approach, which can be related to the Clausius-Clapeyron equation. The SMC-SFC relations yield a new variable, eta, which describes the water retention properties of soil at increasing matric potentials and decreasing temperatures. The five untreated soils demonstrated significantly different frost heave ratios, ranging from 0.7 percent to 49.2 percent. Statistical analysis indicates that the frost susceptibility of the five untreated soils is most dependent on adsorbed cations, eta, amount of microaggregates smaller than 2 mum, and clay content. For the entire body of untreated and cation-treated samples, statistical analysis indicates that the frost susceptibility is most dependent on adsorbed cations, unfrozen water content, and amount of smectite, kaolinite, and chlorite present in the soil. The results from each cation treatment indicate that the frost susceptibility of (1) Ca2+-saturated soil is most dependent on zeta potential and unfrozen water content; (2) Mg2+-saturated soil is most dependent on zeta potential and amount of chlorite; and (3) Na +-saturated soil is most dependent on zeta potential, unfrozen water content, and amount of chlorite.
    • Gis-Based Approaches To Slope Stability Analysis And Earthquake -Induced Landslide Hazard Zonation

      Luo, Huayang; Zhou, Wendy (2006)
      This dissertation presents newly developed GIS-based deterministic and probabilistic approaches for slope stability analysis and earthquake-induced landslide hazard zonation. The described approaches combine numerical slope stability analysis with GIS spatial analysis to evaluate earthquake-induced slope failures, both shallow and deep-seated. The study has four major research components. The first component is a GIS-based procedure which was developed based on one-, two-, and three-dimensional (1D, 2D, and 3D) deterministic approaches to slope stability analysis and landslide hazard zonation. Slope stability methods in the GIS-based procedure included the infinite slope model, the block sliding model, the ordinary method of slices, the Bishop simplified method, and the Hovland's column method. The second component focuses on causative factors analysis of earthquake-induced landslide hazards. This component also discusses the determination of peak ground acceleration for slope stability analysis. The third component consists of an evaluation of the topographic effect of ground motion and the seismic response in the Balsamo Ridge area in Nueva San Salvador. The fourth component is concerned with the regional and site-specific landslide hazard zonation, using newly developed models for landslide hazard assessment in Nueva San Salvador. The slope stability and landslide susceptibility were mapped in terms of slope stability index (factor of safety, critical acceleration, Newmark displacement, failure probability, and reliability index). The landslides triggered by an earthquake on January 13, 2001 in El Salvador provide a setting for the calibration of results from GIS-based approaches. The procedures developed in this research proved to be feasible and cost-effective for slope stability analysis and earthquake-induced landslide hazard zonation.
    • 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.
    • Improved Membrane Filtration For Water And Wastewater Using Air Sparging And Backflushing

      Psoch, Christian (2005)
      The goal of this research was to investigate methods and techniques that enhance mass transfer through the membranes. Two general types of fluids were investigated: synthetic wastewater treated in a membrane bioreactor (MBR) and natural and simulated river water. For both fluids, a wide range of solid concentrations (up to 18 g/L) were tested. The membranes investigated were all tubular modules at pilot scale between 0.75 and 1.20 m length, with tubular diameters of 5.5--6.3 mm, 0.2 mum pore size, and membrane surface areas of 0.036--0.1 m2. For flux enhancement, two techniques were applied: air sparging (AS), and backflushing (BF). Both techniques were compared with the sponge ball cleaning method. The experimental temperature ranged between 10 and 30�C, cross-flow velocities (CFV) ranged between 0.5 and 5.2 m/s, and transmembrane pressure (TMP) ranged between 30 and 350 kPa. Research results showed, that AS was able to enhance the conventional flux over weeks to months up to factor of 4.5 for river water and a factor of 3 for wastewater. At modest CFV of 1.5--2 m/s, AS was as successful as BF. If higher CFV (up to 5.2 m/s) were supplied for BF, this technique could enhance the wastewater flux by factor 4.5. The supply of AS and BF combined was superior to the single application even at moderate CFV. The major finding of this research was that cake thickness on the membrane surface was decreased by AS, contrary to research by other authors. AS can be used as substitute aeration in MBRs, without impairing the degradation performance. The combination of AS and BF generated the least filter cake, but the lowest fouling was observed for AS. An empirical equation was proposed to calculate the viscosity in a sidestream MBR depending on reactor temperature and mixed liquor suspended solids (MLSS).
    • 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.
    • 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.
    • 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.
    • 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).
    • 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.
    • 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.
    • 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.