Now showing items 396-415 of 924

• #### The formation of pore ice in coarse grained soils

Understanding the formation of pore ice in coarse grained soils is important to geotechnical and geo-environmental projects such as the construction of roads, airstrips and gravel foundations as well as the treatment of contaminated soils in the arctic, sub-arctic, alpine and northern regions. The amount of pore ice present controls the strength characteristics of the soils as well as the flow of fluid through the soil. Tests have been conducted to qualify the impact of gradation, temperature, compaction and initial moisture content on the formation of pore ice in coarse grained soils. The purpose of this study was to prepare a conceptual model of the freezing mechanism in coarse grained soils and to qualify the parameters that influence the ice formation. Results from this study indicate that the presence of fine grained particles in a coarse grained soil greatly impact the depth at which the pore space initially becomes saturated with ice. A conceptual model was developed and its application is shown with regards to the process of thaw weakening in roads and the creation of preferential flow paths in permeable reactive barriers.
• #### Fortran IV program for processing geochemical sediment data, 34 p.

A general computer program has been written to process geochemical data resulting from the analysis of up to 34 trace elements per sample. This program will: 1. Produce a table for direct inclusion in formalreports. The table contains the map number and field number of the geochemical samples, the corresponding elemental values and a table giving descriptive data about the sample. Prior to printing, the samples are arranged according to map number for easy correspondence between the table of values and to the geochemical map. 2. Compute the average value for each element, normally and lognormally. 3. Compute the standard deviation for each element, normally and lognormally. 4. Compute the threshold value for each element, normally and lognormally. 5. Compute the anomalous concentrations for each element, normally and lognormally. 6. Draw lognormal, or standard histograms for each element. All geochemical samples taken by the Alaska Division of Mines and Geology during the summer of 1968 and 1969 were processed by this program or a modification of the program. The program can be modified to enable production of automatic maps and tables of anomalous samples.
• #### Fortran IV trent-surface program for the IBM 360 model 40 computer

A Fortran IV trend surface program with polynomial contouring and residual plotting has been adapted to the University of Alaska IBM 360 Model 40 Computer. The program will compute equations of polynomials of the first through sixth degree, measures of the goodness of fit of the surfaces, tabulate original data, x y coordinates and corresponding residuals for each surface; contour each polynomial, and plot original values and residuals for each surface computed.
• #### Fourth annual conference Alaskan placer mining

An abridged format of papers, presentations and addresses given during the conference held on March 30-31, 1982, compiled and edited by: Bruce W. Campbell, John J. DiMarchi, and Ernest N. Wolff.
• #### Fracture and shakedown of pavements under repeated traffic loads

Under repeated external loads, engineering structures or objects may fail by large plastic deformation or fatigue. Shakedown will occur when the accumulation of plastic deformation ceases under repeated loads; the response of the system is then purely elastic. Fatigue and shakedown have been individually studied for decades and no attempt has been made to couple these two mechanisms in the mechanics analysis. In this study, an attempt is made to couple shakedown and fatigue in pavement mechanics analysis using numerical simulation. The study covers three main areas: fatigue, static shakedown, and kinematic shakedown analysis. A numerical approach to fatigue analysis is proposed based on elastic-plastic fracture mechanics. The amount of the crack growth during each load cycle is determined by using the J-integral curve and $\rm R\sb{-}curve.$ Crack propagation is simulated by shifting the $\rm R\sb{-}curve$ along the crack growth direction. Fatigue life is predicted based on numerically estabiished fatigue equation. The numerical results indicate that the algorithm can be applied to fatigue analyses of different materials. A numerical algorithm based on the finite element method coupled with the nonlinear programming is proposed in static shakedown analysis. In this algorithm, both the inequality and equality constraints are included in the pseudo-objective function. These constraints are normalized by the material yield stress and the reference load, respectively. A multidirectional search algorithm is used in the optimization process. The influence of finite element mesh on shakedown loads is investigated. An algorithm that utilizes eigen-mode to construct the arbitrary admissible plastic deformation path is proposed in kinematic shakedown analysis. This algorithm converts the shakedown theorem into a convex optimization problem and can be solved by using a multidirectional search algorithm. Fatigue behavior of a two-layer full-depth pavement system of asphalt concrete is analyzed using the proposed numerical algorithm. Fatigue crack growth rate is estimated and fatigue life is predicted for the system. Shakedown analyses are also carried out for the same pavement system. The comparison between the shakedown load and the fatigue failure load with respect to the same crack length indicates that the shakedown dominates the response of the pavement system under traffic load.
• #### FRAM based low power systems for low duty cycle applications

Ferro-Electric Random Access Memory (FRAM) is a leap forward in non-volatile data storage technology for embedded systems. It allows for persistent storage without any power consumption, fulfilling the same role as flash memory. FRAM, however, provides several major advantages over flash memory, which can be leveraged to substantially reduce sleep current in a device. In applications where most of the time is spent sleeping these reductions can have a large impact on the average current. With careful design sleep currents as low as 72 nA have been demonstrated. A lower current consumption allows for more flexibility in deploying the device; smaller batteries or alternative power sources can be considered, and operating life can be extended. FRAM is not appropriate for every situation and there are some considerations to obtain the maximum benefit from its use. An MSP430FR2311 microcontroller is used to measure the performance of the FRAM and how to structure a program to achieve the lowest power consumption. Clock speed and instruction caching in particular have a large effect on the power consumption and tests are performed to quantify their effect. Two case studies are considered, a feedback control system and a data logger. Both cases involve large amounts of data writes and allow for the effects of the FRAM to be easily observed. Expected battery life is determined for each case when the sample rate is varied, suggesting that average operating current for the two solutions will nearly converge when the sampling period exceeds 1000 s. For sampling periods on the order of one second operating current can be reduced from 15.4 μA to 730 nA by utilizing FRAM in lieu of flash.
• #### A Framework for Life Cycle Sustainability Assessment of Road Salt Used in Winter Maintenance Operations

It is important to assess from a holistic perspective the sustainability of road salt widely used in winter road maintenance (WRM) operations. The importance becomes increasingly apparent in light of competing priorities faced by roadway agencies, the need for collaborative decision-making, and growing concerns over the risks that road salt poses for motor vehicles, transportation infrastructure, and the natural environment. This project introduces the concept of Life Cycle Sustainability Assessment (LCSA), which combines Life Cycle Costing, Environmental Life Cycle Assessment, and Social Life Cycle Assessment. The combination captures the features of three pillars in sustainability: economic development, environmental preservation, and social progress. With this framework, it is possible to enable more informed and balanced decisions by considering the entire life cycle of road salt and accounting for the indirect impacts of applying road salt for snow and ice control. This project proposes a LCSA framework of road salt, which examines the three branches of LCSA, their relationships in the integrated framework, and the complexities and caveats in the LCSA. While this framework is a first step in the right direction, we envision that it will be improved and enriched by continued research and may serve as a template for the LCSA of other WRM products, technologies, and practices.
• #### Freeze-Thaw Durability and Long-Term Performance Evaluation of Shotcrete in Cold Regions

This study’s aim was to evaluate the freeze-thaw durability of shotcrete in cold regions and predict its long-term performance. One benchmark mix design from the WSDOT was chosen to prepare samples for performance evaluation. Shotcrete specimens were conditioned in accordance with ASTM C666. The long-term freeze-thaw performance after certain cycles was evaluated using the dynamic modulus of elasticity test (ASTM C215), fracture energy test (RILEM 50-FMC), and X-ray CT microstructure imaging analysis. Probabilistic damage analysis was conducted to establish the relation between the durability life and the damage parameter for different probabilities of reliability using the three-parameter Weibull distribution model. The fracture energy test was found to be a more sensitive test method than the dynamic modulus of elasticity for screening material deterioration over time and for capturing accumulative material damage caused by rapid freeze-thaw action, because of smaller durability factors (degradation ratios) obtained from the fracture energy test. X-ray CT imaging analysis is capable of detecting microcracks that form and pore evolution in the aggregate and interface transition zone of conditioned samples. Moreover, the continuum damage mechanic-based model shows potential in predicting long-term material degradation and the service life of shotcrete.
• #### Froth flotation characterization and processing plant design for the platiniferous and auriferous marine sediments of Southwestern Alaska

The purpose of this study was to characterize, and investigate the beneficiation of, the platiniferous and auriferous marine sediments of Southwestern Alaska, located near Platinum, Alaska. The majority of placer gold particles are contained in the 50 x 150 mesh size fraction, while the platinum is finer, residing in the 100 x 200 mesh size fraction. Liberated placer gold and placer platinum group metals (PGM) particles are visible to the naked eye and readily observed under a binocular microscope. Preliminary, qualitative microprobe analysis of PGM grains from the flotation concentrate showed grains of nearly pure iridium, isoferroplatinum and Pt-Rh-Ir-Fe-S-As mineralogy. Froth flotation showed that placer gold responded very well to all the collectors used, with gold recoveries of 82.7-99.8%. Flotation of platinum responded well to only potassium amyl xanthate, with a recovery of 80.4%. Results of low intensity magnetic separation showed that virtually all the liberated gold and platinum reported to the non magnetic product. A flowsheet, with estimated capital and operating costs, was developed to process 1500 tph of marine placer feed. Annualized costs per ton to process marine sediments were estimated to be $2.40 to$3.72 depending upon plant availability, 90% to 50%, respectively.

• #### Fuel Cell Power Plants in Rural Alaska

On the basis of fuel efficiency alone, the methanol fueled phosphoric acid fuel cell (PAFC) is a very attractive replacement for the diesel electric generator, especially in the bush regions of Alaska. However, because of the transportation costs for liquid fuel to the bush combined with the lower heating value of methanol, the PAFC looses this advantage and produces electricity that in some instances is more costly than the diesel generator. Although the PAFC is at the highest state of development of all fuel cell power plants, it is still not a commercially mature technology. The present cost of a PAFC power plant is on the order of ten times the price of an equivalent diesel electric generator. There is also no large body of published, long term data on fuel cells of any type larger than 1 kw from which an accurate assessment of reliability, maintenance and operating costs can be made. Considering this and the lack of electrical production cost advantage, the evaluation of the methanol fueled PAFC for buch applications should be suspended until more operational data is made public and units are commercially available.
• #### Fuel penetration rates in frozen and unfrozen soils: Bethel, Alaska

Alaska fuel-storage facilities are required by law to provide secondary containment for their largest tank-volume. Secondary containment commonly includes berms, catchment basins and ditches. Fuel-penetration rates on site soils are needed to predict potential fuel-penetration depths. Field and lab tests quantified fuel-penetration rates for three site soils in Bethel, Alaska. In-situ tests following ASTM D 5093-90 allowed measurement of fuel infiltration rates using a falling-head permeameter allowed quantification of hydraulic conductivities, permeabilities and infiltration rates in frozen and unfrozen soils prepared at various moisture contents. Unfrozen samples were tested at room temperature, 19.8-24.0C̊ (67.6-75.2F̊). Fuel-penetration rates were similar regardless of moisture contents. Tests for frozen samples occurred at -4C̊ (25F̊). Fuel-penetration rates decreased as ice-saturation increased. The permeant used for each test was a Diesel #2/Jet A-50 fuel mixture (heating fuel) consisting of predominately Jet A-50.
• #### Gaseous emissions from herding agent-mediated in-situ burning for Arctic oil spills

If a crude oil spill were to occur in partially ice-covered waters, many of the response tactics typically utilized in either open water or completely ice-covered conditions would become inefficient. In such situations, in-situ burning (ISB) can prove to be an efficient response tool; herding agent application is one available approach to thicken an oil slick. This study assessed the impacts on air quality following ISB tests on crude oil, in combination with herding agents, in partially ice-infested waters. The research focused on measuring downwind concentrations of respirable particulate matter (PM₂.₅) and seven different combustion gasses (CO, CO₂, NO, NO₂, NOx, SO₂, and VOCs) during five ISB events, with sampling instruments placed in-plume and 6-12 m away from the source area. The study also investigated if the utilized herding agent was detectable in the airborne plume. Findings include: 1) Concentrations of particulate matter (<2.5μm in diameter), SO₂, and CO were found to significantly (P <0.01) exceed various exposure limits and air quality standards, while the remaining compounds measured were significantly (P <0.01) below established exposure limits. Also, downwind, in the smoke plume, measured concentrations of SO₂, NOx, and total VOCs were higher than found in previous studies. It should be noted that instrument and methods not specifically approved by the U.S. Environmental Protection Agency, Occupational Safety and Health Administration, and the National Institute for Occupational Safety and Health were utilized during this study; 2) GC/MS analysis of aerosol samples collected utilizing a flow meter and carbon sorbent tubes in the smoke plume; the Siltech OP-40 silicone based functional group of the applied herding agent was not detected in the collected samples analyzed using GC/MS. Future research should include additional scalability studies where the concentrations of particulate matter and various combustion gasses are compared to modeled concentrations using computer software. Additional research is also needed to find a cost-effective method to decrease the amount of particulate matter during an in-situ burn. It is also recommended that guidance specific for conducting in-situ burns of crude oil or refined petroleum products in the Arctic is written and published by regulatory agencies, so the industry can rapidly make plans and propose such tactics if an incident did occur where mechanical or other non-mechanical response tactics are not feasible.
• #### Geochemical-geophysical investigations, Fairbanks district

Trace element distribution in a subarctic valley in the Cleary Hill area of the Fairbanks gold district has been studied. Zinc and arsenic have been found excellent pathfinder elements for auriferous deposits. Methods of analysis for copper, lead, zinc, molybdenum, silver and arsenic as well as heavy metals are discussed. The University of Alaska method #2 has been improved, Terrain, slope, and frozen ground have little effect upon the distribution of trace elements associated with the Cleary H i l l vein. A new method for the determination of zinc using dilute acid is proposed. Analysis of geochemical data by trend surface procedures proved effective for localization of anomalies.
• #### Geodatabase development and GIS based analysis for resource assessment of placer platinum in the offshore region of Goodnews Bay, Alaska

Goodnews Bay, southwest Alaska, is known for extensive Pt reserves that have their source in the neighboring Red Mountain. The reserves potentially extend offshore into the Bering Sea. This study aims at developing a geodatabase to integrate all offshore platinum related data collected by researchers and agencies in the past, with the intent to identify data gaps. Based on these data gaps 49 new areas were sampled for Pt and geophysical data were collected in summer 2005. Spatial distribution map for offshore Pt was created using a new Multiple Regression Pattern Recognition Technique (MRPRT) that gave an R²=0.76, a significant improvement from standard GIS based geospatial techniques. Four potential Pt exploration areas were delineated, including one area where drowned ultramafics and buried alluvial channels co-occur. Coastal currents influenced the surficial platinum accumulations, and no clear relation between Pt distribution and sand bars in the far offshore could be established.
• #### A geohydrologic analysis of an upland-bedrock aquifer system: applications to interior Alaska

Ester Dome, an upland-dome bedrock aquifer system, located nearby Fairbanks, Alaska, was studied to identify important geohydrologic processes occurring in Interior upland aquifer systems. The ground-water dynamics at Ester Dome are complex due to the fractured nature of the aquifer system. The geology at Ester Dome consists of metamorphic and igneous rocks. Valley bottom deposits include gravels and loess. The flow pattern of the dome aquifer system is radial. Ground-water flows from a central high elevation recharge area and discharges into lakes, streams, and wetlands in the valley bottoms. The primary form of recharge to the bedrock aquifer is from spring snowmelt. Snow water equivalent and snow depth increases with elevation. Ground-water levels were observed at fifty sites on Ester Dome for two years. Water levels in wells at high elevations or locations with no silt or permafrost coverage show seasonal fluctuations. However, ground-water levels in the valley bottoms show little seasonal fluctuations, except wells that penetrate gravel deposits and have no overburden. A ground-water flow model was developed to aid in the understanding of these geohydrologic processes. The ground-water flow model shows recharge and bedrock hydraulic conductivity as the most sensitive parameters.
• #### Geologic description and reservoir modeling of a Jurassic aged, low permeability, light oil reservoir, northern coastal plain, Alaska

The objectives of the study include the analysis of the geologic description and reservoir modeling of a Jurassic aged, low permeability, light oil reservoir on the northern coastal plain of Alaska. The methodology of the study was to use a reservoir simulation model to evaluate the performance and cumulative recovery of the reservoir under primary depletion and a water injection process. Results of the simulation showed a primary recovery of 15.9 %OOIP of oil by solution gas drive. The results of thee simulation by a water displacement process showed that 41.9 %OOIP oil could be recovered with a production of 38.5 %HCPV of the injected water. This study has an application in determining estimates of the design paramaters for surface facilities required for the development of the field.
• #### Geological modeling and reservoir simulation of Umiat: a large shallow oil accumulation

Current high oil price and availability of new technologies allow re-evaluation of oil resources previously considered uneconomic. Umiat oil field is one such resource: a unique, shallow (275-1055 feet), low-pressure (200-400 psi) reservoir within the permafrost zone located north of the Arctic Circle, 80 miles west of Trans Alaska Pipeline System (TAPS) with an estimated 1.5 billion barrel of oil-in-place. This thesis presents a reservoir model that incorporates recently identified permeability anisotropy patterns within the Cretaceous Nanushuk sandstone reservoir to evaluate various potential mechanisms such as horizontal wells and immiscible gas injections. The simulation model focuses on the Lower Grandstand which is identified as a better reservoir rock. The reservoir temperature is assumed at 26 OF and gas is injected at the same temperature to maintain equilibrium with the permafrost and prevent any well integrity problems. An optimum horizontal well length of 1500 ft was found and applied for all simulation cases. The simulation results show that with 50 years of lean gas injection, recovery factors for the base case and case of 600 psi injection pressures are 12% and 15%, respectively, keeping all other parameters constant.
• #### Geology and Geochemistry of the Ship Creek and Monashka Creek reservoirs, Southcentral Alaska

Graywacke from the Ship Creek watershed, dissolves incongruently in distilled water. The dissolution appears to follow a first-order rate law which in integrated form is: k = -2.303/t log No-Q/No where No is the concentration in ppm of Ca, Mg, Na or K in the graywacke, Q is the total quantity of these ions leached in time t(days), k is the rate constant in days-1. Experimentally derived rate constants for the dissolution of graywacke in distilled water at 5oC are log k+2CA, -4.128 day-1; log k+2Mg, -6.174 day-1; log k+Na, -5.800 day-1; and log k+K, -5.249 day-1. The above constants are for 40 to +100 mesh graywacke. A surface area correction term must be inserted in the above equation if it is applied to a different size fraction. Using the above equation and rate constants, the chemical composition of a water in contact with graywacke was calculated. With the exception of magnesium, the agreement between the calculated composition and that of Ship Creek water was good. Assuming that the groundwater in the Ship Creek watershed contacts about 1.5X104cm2 graywacke per liter, 120 to 360 days are required at 5oC to produce the concentration of ions observed in Ship Creek. Release of exchangeable H+ from the soil mat to the reservoir water will not significant1y lower the pH of the water. Leaching of heavy metals from sulfides contained in the bedrock of the two watersheds does not pose a water quality hazard. Lineaments in the bedrock at Monashka Creek may provide channels through which water may seep from the reservoir. These are not expected to pose a problem in retaining water in the reservoir, but they may result in small, new springs down grade from the reservoir.