COLD REGIONS ENGINEERING
Proceedings of the Eighth International Conference on Cold Regions Engineering
University of Alaska
August 12-16, 1996
GEOTECHNICAL AND THERMAL CONDITIONS
Air Convection Embankments for Roadway Construction in Permafrost Zones
Douglas J. Goering
A new technique for protecting roadways from damage due to thermal degradation of underlying permafrost is investigated. The technique relies upon the use of an open graded aggregate for construction of the major portion of the embankment. Such a material allows winter-time natural convection to occur within the embankment thus increasing cooling of the embankment and permafrost foundation during winter months and preserving the permafrost layer. Both experimental and numerical investigations have been carried out in order to assess the performance of these embankments. Numerical simulations show that they can lower subgrade temperatures by 5°C or more, on an average annual basis compared to standard roadway embankments. Field measurements made in an experimental air convection embankment located near Fairbanks, Alaska have confirmed the existence of convective eddies within the embankment during periods of cold weather, as predicted by the numerical model. Temperature measurements taken below the embankment indicate that a permafrost layer began to develop beneath the embankment even though none existed prior to construction.
Performance of a Passively Refrigerated Gravel Pad Foundation in Fairbanks
Stephen Adamczak, Jr.
Foundation designs for nonthaw-stable permafrost commonly include piles or post and pad foundations designed to thermally isolate the structure from the ground surface, thereby reducing the transfer of building heat and subsequent thawing of underlying permafrost. Although these foundations are cost effective and common for many structures, they are less desirable for heavy structures or structures that are designed for high live loads. The concept of constructing structures on a passively refrigerated gravel pad has proven to be a valuable and effective foundation design alternative for foundations on nonthaw-stable permafrost.
In areas underlain by nonthaw-stable permafrost structures such as equipment maintenance buildings, equipment storage structures, and heavy masonry structures can have loads which are very difficult, or costly, to effectively support with an elevated floor. Alternative at-grade foundation designs have been successfully used. These at-grade foundation designs generally incorporate a passive or active cooling system, installed in a nonfrost-susceptible gravel pad designed to maintain stable permafrost conditions.
Light framed structures have also been successfully founded on refrigerated gravel pads. The Federal Aviation Administration (FAA) Automated Flight Service Station in Fairbanks is founded on a refrigerated gravel pad foundation. Typical slab-on-grade building designs for this structure, nonthaw-stable permafrost conditions, and the aesthetic desire to have an at-grade structure required a slab-on-grade foundation design capable of maintaining stable permafrost conditions. This structure was designed and constructed on a thermal syphon-refrigerated, insulated, gravel pad with a concrete slab-on-grade.
As with many of the foundation designs in permafrost areas, very little documented information is available on long-term permafrost foundation performance and the nature and status of the underlying permafrost. Designs are generally developed with computer models using a multitude of assumed or measured soil, structure, and climatic conditions. The data gained from the performance history of this refrigerated gravel pad provide a valuable guide and comparison for design and modelling of similar foundation systems.
Temperature instrumentation installed during construction has been monitored several times a year since construction, and offers an 8-year record of permafrost behaviour. This paper presents a summary of this foundation performance. The effects of variable climatic conditions and thermosyphon performance can be observed and quantified. Seasonal and yearly fluctuations in soil temperature are evident and depict a stable permafrost profile beneath the structure foundation. The effects of seasonal temperature and wind speed are also evident in the data collected. The data also suggest that global warming or other climatic changes could alter the performance of the foundation system. Although stable permafrost conditions have been maintained and the foundation has been stable, the performance may be subject to change under other climatic conditions.
Stress and Temperature Effects on Silt Frost Heave
Seyed M. Marandi, Douglas I. Stewart, and Terrence W. Cousens
Frost heave in fine-grained soils during freezing, and loss of strength during the subsequent thawing causes extensive damage to structures (i.e. roads, airfields, buildings, retaining walls, pipes, etc.) built in cold climates. There are several extrinsic and intrinsic factors that influence frost heave. Loading is one of the extrinsic factors which have been widely discussed by researchers in the literature. This factor (together with frost depth and water table depth) controls the depth to which frost susceptible soil must be replaced if frost heave beneath a structure is to be avoided.
This paper presents new experimental data from one-dimensional step freezing tests on an artificial silt sized soil containing no clay minerals. Surcharge stresses varying from 0 to 67 kPa, and two temperature gradients of 0.01 C°/mm and 0.04 C°/mm were used in this study (the latter temperature gradient being typical for one-dimensional frost heave tests). Increasing surcharge stress significantly reduces the heave rate at a given temperature gradient, although there was detectable segregated heave in all tests. Also, a four fold decrease in temperature gradient caused more than a four fold increase in Segregation Potential. It is suggested that for Segregation Potential to be a meaningful index, it must be measured at a standardized temperature gradient.
A Strength Sensitivity Index for Assessing Climate Warming Effects on Permafrost
The present paper attempts to quantify the sensitivity of frozen ground strength to temperature increase that may result from general climate warming, and proposes a simple strength-sensitivity index that could be used as a basis for mapping the zones of potentially stable and unstable permafrost, with the purpose of estimating the potential damage to the existing structures, and drafting the design guidelines for future projects.
Surface Modifications to Reduce Thaw Degradation of Permafrost
John P. Zarling and Jasper Rajesh
This paper reports on the evaluation of two surface modification techniques to reduce permafrost degradation below roadway embankments. Snow management on side slopes was computer modelled and field tested. Results showed a 20% increase in freezing n-factor. A second method consisted of placing quarry rock to a depth of 1.3 m on side slopes. An increase in freezing and decrease in thawing n-factors of 150%, respectively were measured. This yielded a reduction of the MASST of 8°C. The porous rock cover allows natural convection to occur during winter and provides stable layer of insulating air and solar shading during the summer.
ENVIRONMENTAL - REMEDIATION
Spray Freezing to Treat Oil Sands Tailings Pond Water
W. Gao, D.C. Sego, and Daniel W. Smith
To evaluate the potential use of spray freezing technology in removing inorganic and organic contaminants from recycled oil sands tailings pond water, a field study was carried out at the Syncrude Canada Ltd. mine site in February 1994. A plastic lined containment area was prepared to collect the spray ice.
A spray ice pile measuring 18 by 12 m in plan and 5 m high was produced after 15 hours of spraying. Various water samples and ice samples were collected. Parameters such as pH and electrical conductivity, Na+, C1- and total organic carbon (TOC) concentrations were measured on these samples.
The laboratory measurements of the ice cores showed a reduction in the average concentration of C1- of between 90.8% and 98.7% and a reduction of 97.8% in the melt water which drained downward through the spray ice mound. These reductions were based on the original concentration measured in the source water used during the spraying test. The lower reduction was measured using the ice cores retrieved in March and the greater reductions occurred in the ice core obtained in April 1994. Similar reductions were measured for the Na+ ion using the same samples. The total organic carbon (TOC) measurements on the ice core showed a reduction of between 89.3% and 98.9% while the melt water showed a reduction of 93.4%. The electrical conductivity’s of the ice cores decreased by between 91.5% and 99.1% and the conductivity of the melt water decreased by 95.7%.
The field test results demonstrated that winter spraying of the recycle water with initial flush diversion for further treatment was effective in decreasing both organic and inorganic contaminants in this industrial recycle water.
Interference by Natural Organics in Diesel Analyses
Naturally occurring organics may be reported as false positives during environmental testing, since they are often similar in molecular weight and chemical character to anthropogenic hydrocarbons. Background concentrations of diesel range organics (DRO) as high as 3,600 milligrams per kilogram (mg/kg) in soil and 0.62 milligrams per litre (mg/L) in groundwater have been reported in Alaska using EPA Method 8100 modified. In some cases, these background concentrations are above state regulatory cleanup levels for DRO.
Chromatograms for a diesel fuel sample generally show a range of hydrocarbons present between C-10 to C-24, with the highest concentrations around C-18. In contrast, chromatograms for background DRO appear to be dominated by compounds heavier than C-18, with the highest concentrations in the C-20 to C-24+ range.
There are four potential solutions to the problem of naturally occurring DRO in environmental samples. The first is to collect representative background samples from the site. Once an upper limit for the background DRO concentration is established, it could be subtracted from the reported DRO concentrations at the site to evaluate the anthropogenic diesel contribution. Another possible solution would be to focus the investigation on the overall toxicity of the DRO components reported.
It may be possible to utilize laboratory cleanup steps in conjunction with EPA Method 8100m to selectively remove the naturally occurring DRO from the sample prior to analyses. Several experiments with these techniques have shown them to be only partially effective (Brown and Whitsett, 1995).
Another approach is to evaluate and interpret the analytical results where interference by naturally occurring DRO is suspected. The DRO concentration between C-10 and C-18 can be computed, compared to the DRO concentration within that range for the fuel released, and the total anthropogenic DRO concentration estimated based on this comparison.
Modelling of Contaminant Transport in Groundwater in
Areas of Discontinuous Permafrost
Ron Johnson, Doug Kane, Larry Hinzman, Greg Light, and Ann Farris
The Water Research Center participated in a multi-year study to provide a quantitative description of the effects of discontinuous permafrost on contaminant transport in the groundwater at Fort Wainwright, Alaska. A critical part in formulating a remediation strategy is the development or adaptation of appropriate analytical and numerical models to predict the contaminant pathways. Primarily interested in the migration of contaminants dissolved in groundwater, we utilized solute transport models that incorporate both advection and dispersion and can also include the effects of retardation of the solute with respect to the local groundwater velocity. After collecting appropriate hydrologic and water quality data, we performed tracer tests to allow us to estimate several key aquifer parameters. We then performed both analytical and numerical plume modelling calculations to predict plume migration. The results show the possibility of a westward migration over a period of decades, with the permafrost distribution significantly affecting the direction of flow.
Petroleum Hydrocarbon Removal Via Volatilization and
Biodegradation at McGrath, Alaska
Paul C. Ramert and Wayne L. Eberhardt
The Alaska Department of Environmental Conservation (ADEC) has established cleanup levels for contaminated soil generated by releases and spills from fuel storage tanks (FSTs). In the process of decommissioning and replacing its current inventory of FSTs, the Federal Aviation Administration (FAA), Alaska Region, has encountered varying degrees of contaminated soil requiring treatment. This paper presents treatment results for two biocells operating at the McGrath Station; specifically, it describes biocell treatment system design and operating parameters, and tracks demonstrated hydrocarbon removal rates and trends for gasoline-range and diesel-range organics.
A Pilot-Scale Study of In Situ Hydrocarbon Remediation of
Contamination in Soil and Groundwater at Fort Wainwright, Alaska
Timothy F. Gould and Mark Wallace
The establishment and enforcement of cleanup standards for hydrocarbon-contaminated soil and groundwater has led to the rapid evolution of remedial technologies in Alaska. A pilot-scale treatability study was performed at Fort Wainwright, Alaska, to investigate the feasibility of using air injection/soil vapour extraction (AI/SVE) for remediation of contaminated soil and groundwater. The study focused on monitoring remediation rates resulting from volatilization and biodegradation in the vadose and saturated zones. Study objectives included the assessment of contaminant removal rates for each identified treatment process and the estimation of the treatment time required for site remediation. This paper summarizes the results of hydrocarbon removal rate measurements and presents a method for estimating the time required for site remediation.
Vertical Migration of Diesel into Silty Sand Subject to Cyclic Freeze-Thaw
K. W. Biggar and J. C. R. Neufeld
A laboratory experimental program was conducted on 30 cm high, wet tamped soil columns of silty sand with a layer of diesel contaminated soil placed on the surface. The soil was cyclically thawed then frozen from the upper surface to approximately half way down the column, maintaining the lower portion of the soil column in a frozen state for the duration of the test program. The results showed considerable migration of diesel into the saturated uncontaminated soil which was subjected to cyclic freezing and thawing, however, no contamination was observed in the permanently frozen soil after up to 8 freeze-thaw cycles.
Minimum Thermal Protection for Cold Weather Masonry
Charles J. Korhonen, Edel R. Cortez, and Robert D. Thomas
A study was conducted to assess ways to minimize thermal protection requirements for cold weather masonry construction. Frost damage immunity thresholds in terms of mortar moisture content and maturity were determined. Correlations of moisture content with time were developed for mortar in contact with masonry units. Guidance for when fresh mortar can be allowed to freeze, how quickly water can be withdrawn from fresh mortar by masonry units, and at what water content mortar first becomes immune to frost damage are provided. The effects of temperature and antifreeze admixtures on the strength and durability of mortar were studied.
Northern Climate Weathering Tests on Sealed Concrete
In recent years, attempts to eliminate deicing salts and moisture penetrations have been made by applying surface coatings and sealers to the concrete surface. Although use of sealers and coatings has met with varying degrees of success, it is not uncommon for them to cause earlier failure and uneven discolouration of the concrete surface, thereby degrading the aesthetics of the structure. In addition, new coating systems emerge on the market almost every day. Many engineers in cold regions continually face the challenge of selecting a proper coating system for construction projects.
Research was conducted to evaluate generic types of sealer and coating systems for use in northern climate areas. The purpose of this paper is to present the research results and methodologies. The paper will begin with a discussion of the methodologies used in the research. Accelerated weathering test in the laboratory will be illustrated first. Then, field test will be presented. Various generic sealers were put on the surface of concrete in both laboratory and highway field, and then samples were taken from the sealed concrete. The content of chloride ions in the samples was analyzed and compared.
Low Temperature Performance Rating Criteria for Lubrication Greases
Jan Lundberg and Terry T. McFadden
The development of a rational evaluation method that can be applied to greases subject to low temperature service is attempted using a two level approach. The greases are evaluated as to their expected performance based on criteria that are currently believed to be important. The actual performance of the greases is then assessed in service on a railway hauling iron ore in northern Sweden and Norway under severe conditions of low temperatures and heavy duty demands. The relevance of the expected criteria in predicting actual performance will be used to establish a weighting system for each criteria to develop an overall performance number that can be used for rational selection of greases for low temperature service.
Several methods of evaluating the performance criteria are discussed along with their advantages and drawbacks. The overall plan for developing the performance number is presented. Present progress is reported along with an estimate of future developments and their expected availability and impact on the overall plan.
Coating of Steel Structures in Cold Regions
Yuji Nakamura, Taiichi Inaba, and Akihiro Tamada
Long-term paint/coating exposure tests in an arctic climate have been carried out by NKK because very little is known about the effectiveness of corrosion prevention measures for steel structures under arctic conditions. Twenty-one types of standard and heavy coating systems are under exposure tests at Fairbanks, Alaska. This paper presents the results of a survey of the coatings after 13 years exposure. Zinc rich and epoxy/urethane coating systems have provided the most durable long-term service in the arctic climate. Chlorinated rubber and vinyl chloride resin paint films cracked and do not appear to be appropriate for arctic service.
Freeze-Thaw Durability of Concrete Cured Below 0°C Using Antifreeze Admixtures
Michael R. Mason and Herbert P. Schroeder
It has been estimated that the cost of protecting freshly placed concrete from freezing exceeds $800 million annually (Flynn, 1992). Previous research has investigated the compressive strength and rebar pull-out strength of concrete cured below 0° Centigrade which was batched by using calcium nitrite and sodium nitrite as antifreeze admixtures (Korhonen, 1991) (Wood and Schroeder, 1993) (Schroeder and Wood, 1996). Concrete prepared in this manner is called cold weather concrete. There have been no reports in the literature evaluating the freeze-thaw durability of cold weather concrete prepared with antifreeze admixtures and subjected to cyclic freeze-thaw during curing. This study investigated the compressive strength of cold weather concrete when subjected to cyclic freeze-thaw during the first 28 days of cure. Results indicate that cold weather concrete mix used in this research and subjected to cyclic freeze-thaw developed strengths in the range of 17.25 MPa.
PIPELINES AND COLD REGIONS RESEARCH
The Status of Cold Regions Research
Thomas C. Kinney, Robert C. Carlson, and Howard Thomas
A workshop on the status of research was held at the 1994 Cold Regions Engineering Specialty Conference in Edmonton, Alberta to explore how a professional society could advance the state of knowledge regarding cold regions engineering. Forty people from a wide variety of backgrounds took an active part in the discussions. Ultimately, a list of specific topics was developed, which will be used by the American Society of Civil Engineers (ASCE) Technical Council on Cold Regions Engineering (TCCRE) Research Committee and their Canadian counterparts in an attempt to promote research in cold regions.
Thermal Impact of a Buried Chilled Gas Pipeline
Lutfi Raad, Xioalin Yuan, and Dieter Weichert
The impact of a buried chilled gas pipeline is directly related to the growth of frost bulb surrounding the buried pipe. Estimation of the size and rate of growth is important to assessing potential engineering problems and choosing the appropriate solutions. Frost bulb growth calculations, however, could involve significant computation effort that requires the use of advanced numerical models for heat and moisture migration. In this paper, simple chart solutions using dimensional analysis were developed to determine the frost bulb growth. These solutions were based on results from numerical analysis that account for ground surface temperature, pipe temperature, depth of pipe embedment, and depth of permafrost boundary on the corresponding frost bulb growth around the buried pipe. Dimensional analyses were used to group the significant variables into dimensionless parameters and produce simple charts for predicting the size of frost bulb and its rate of growth.
Upheaval Buckling of a Pipeline in an Arctic Environment
T. Bartlett Quimby and Michael R. Fitzpatrick
A 10 inch (25.4 cm) diameter, 147 mile (237 km) long natural gas pipeline was installed across the North Slope of Alaska’s Brooks Range in the late 1970’s. Several sections of the pipe have been exposed at the ground surface in a 6.7 mile (10.8 km) segment on the Arctic Coastal Plain. The process appears to result from upheaval buckling of the pipeline driven by thermal expansion. Poor restraint by thawed and saturated cover soil is a major contributor to the problem.
The exposed pipe is subject to mechanical injury from vehicles on or crossing the pipeline workpad, and local strain conditions have exceeded yield strain for the pipe steel in two locations. The pipeline operator has chosen to reduce the bending stresses and rebury the pipe where this phenomenon has occurred. A maintenance program conducted each year since 1991 has resulted in excavation and reburial of 15 segments of pipeline.
This paper describes the analysis of the upheaval buckling phenomenon and the procedure used to rebury the pipeline.
Transportation of Alaska North Slope Natural Gas to Market
Donald A. Lannom, David O. Ogbe, Akanni S. Lawal, and F. Lawrence Bennett
A mathematical optimization model is developed for quantitatively evaluating the options available for transportation of North Slope natural gas. The model considers environmental factors of the North Slope, transportation infrastructure in the arctic, economic considerations, production, distribution and other regulatory constraints. Using the optimization model the optimal decision recommended is to transport conditioned gas by pipeline to a tidewater port for liquefaction and marketing to Pacific Rim countries. Two pipeline routes are considered feasible: the southern route that parallels the Trans Alaska Pipeline System (TAPS) to Valdez, Alaska, and a western route that would cross the National Petroleum Reserve in Alaska to a port either in Wainwright or Kivalina, both in Northwest Alaska. The advantages of the southern route compared to the western routes are presented.
GEOTECHNICAL - FOUNDATION AND PILES
Comparison of Static and Dynamic Test Results for Driven Steel Pipe
Piles in Highly Saline Permafrost
Kelly S. Merrill and Richard E. Riker
This paper describes evaluation, design, static and dynamic field testing, and installation of a driven steel pipe pile foundation system in highly saline permafrost. Static load tests were conducted on two test piles as part of the final design to confirm and refine preliminary pile capacities. Dynamic pile tests were conducted on four production piles during construction to confirm pile drivability without pilot holes, assess hammer and pile performance, and confirm the results of the static load tests. These dynamic tests are believed to be among the first such tests run on driven piles in permafrost. The dynamic tests provide magnitude of steel stresses in the pile and allow assessments of the pile integrity during driving, thus providing a useful tool to avoid pile damage in permafrost conditions where unaided pile driving may be feasible. Comparison of the static and dynamic test results can aid evaluation of such factors as load distribution between the toe and the shaft, distribution of shaft load, residual and full adfreeze bond strengths, and short-term versus long-term soil strength.
Driven Pile Capacities in Warm Permafrost in Komi Republic, Russia
Steven R. Thompson and Rupert G. Tart, Jr.
The Kharyaga pipeline terminal was part of the first oil field development in Russia by an American-Russian joint venture after the breakup of the Soviet Union. The terminal for the pipeline was located in Kharyaga, a small settlement in Komi Republic. The U.S. partner was responsible for engineering the terminal and developing it using appropriate U.S. technology.
Based on limited available local information, the entire terminal area was thought to be underlain by warm permafrost. Consequently, it was decided to support all structures on open-ended steel pipe piles. Because of the rushed construction program, it was necessary to conduct a limited geotechnical investigation as the piles were being delivered, and then to conduct a pile load test to determine driving depths and pile capacities. Driveability of the open ended piles in permafrost was a concern, as was the long term creep performance of the piles.
Pile capacities estimated using static formulae and wave equation analysis correlated well with full scale pile load testing. A design load versus driving depth relationship was developed for production pile driving.
This paper describes the geotechnical investigation, the pile installations, the pile load test and the analyses used to develop capacities for each of the piles.
Research Program for Reducing Frost Heave with Geosynthetic Capillary Barriers
Karen S. Henry and Earl Ellis
A research project co-sponsored by the U.S. Army Corps of Engineers, the Alaska Science and Technology Foundation, and the Alaska Department of Transportation and Public facilities to develop design criteria for geosynthetic capillary barriers is being conducted at the U.S. Army Cold Research and Engineering Laboratory. The successful use of geosynthetic capillary barriers would allow the use of a greater volume of frost-susceptible soil in roadway and airport embankments, while achieving the same or better pavement performance, resulting in great cost savings. The results of past work with granular capillary barriers in pavements to reduce frost heave provide preliminary guidance for using geosynthetic barriers.
This paper describes the experimental program to help define conditions under which geosynthetic capillary barriers will be effective. The primary variables being examined are geotextile pore size distribution and thickness, as well as rate of heat loss during freezing of soils. The response being measured is rate of frost heave. The selection process for candidate materials includes capillary rise testing and the application of geotextile filtration criteria.
Foundation Retrofit at Savoonga "A Retrospective Study"
G. Scott Crowther
In 1949 and 1950 the Presbyterian Church constructed a building at Savoonga, Alaska. Creosote-treated timber piles supported the building above grade. The piles extended 0.9 m below grade into permafrost soil. Space under the building was enclosed by skirting. So heat emitted through the building’s floor warmed its underlying air space and permafrost soil. Over the next 42 years the piles slowly settled, which caused distress to the building. The building was relevelled in 1975 and again in 1990 to adjust for the settlement.
During a building reconnaissance in 1992, a survey was performed to assess pile movement. A lack of soil stains on pile shafts above the ground surface indicates that they were not pushed upward by frost jacking. So the piles apparently settled. Piles settled most where heat was continuously emitted through the building’s floor, where runoff was ponded, and where the adjacent snow cover was thinnest. An estimated maximum end-bearing pressure of 120 kPa resulted in 0.07 to 0.34 m of pile settlement. There was up to 0.11 m of measured differential settlement over a 4.8 m distance (a 1/40 angular distortion).
The creosote-treated timber piles apparently were not pushed upward by frost jacking. It is estimated that frost jacking would have lifted the structural load plus overcome the adfreeze resistance in the permafrost soil if there had been a 50 kPa or greater adfreeze bond in the refreezing active layer. So if an adfreeze bond developed in the refreezing active layer it must have been less than 50 kPa.
In 1993 the building was retrofitted with a treated timber, spread-footing foundation. The footings are buried 0.6 m below the surface on a 0.15 m levelling course of sand and gravel fill. Footing excavations were backfilled and covered by insulation. Soil has been placed over the insulation and graded so runoff will drain around the building. Skirting was removed so air can circulate beneath the building. With these structural and site improvements, soil beneath the footings is expected to remain as permafrost. As of 1996 the new spread-footing foundation has supported the building without any noticeable movement.
Performance of a Triodetic Foundation Near Fairbanks, Alaska
Thomas C. Kinney
A Triodetic Foundation was placed under a small house which had undergone serious distress due to thawing permafrost. The manufacturer’s specifications stated that the foundation would keep the structure on a plane within a tolerance of L/360 regardless of the magnitude or pattern of differential movement caused by future frost heaving or thawing permafrost. The house was placed on the foundation in June 1994. It was about 20 cm (8 in.) out of level, but nearly on a plane. In late September the foundation was levelled. During the levelling process it was obvious that the foundation was not as rigid as anticipated, hence the next summer (1995) the foundation was tested to evaluate its rigidity. The results show differential settlements in excess of L/50 under less than the most severe surface movement conditions.
Foundations for Permafrost and Other Problem Soils
William J. Vangool
A large area of the Northern hemisphere consists of soils which are permanently frozen. The top layer or active layer is subject to seasonal freezing and thawing. When building on this ever changing upper layer differential settlement is sure to occur. All efforts relating to the selection and installation of proper building materials such as insulation, double or triple glazed windows, arctic doors, sealants, heating and ventilating systems for the building can not be relied upon unless these are free of stresses induced by differential settlement of the building.
A new concept to the approach of foundation design accepts the unreliable and ever changing bearing capacity of the soil and gives strength to the building in its entirety. The foundation and building combined become one homogenous torsionally stable entity and by means of a multiple array of bearing support points rests freely on top of the soil.
An overview of conventional foundation systems is presented as well as a discussion of the design criteria and field performance of this innovative prefabricated tubular foundation frame.
West Dock Causeway Bridge Piers
Alan B. Christopherson, T. Nottingham, J. W. Pickering, and K. W. Braun
Constructed in 1994-1995, the 262 m West Dock Causeway Breach bridge is located along the West Dock gravel causeway in the Beaufort Sea on Alaska’s north slope. The bridge was designed by Peratrovich, Nottingham & Drage, Inc. (PN&D). The bridge was constructed in response to concerns of coastal shoreline fish movement and water circulation.
The bridge is founded on three in-water ice breaking steel piers and six bents protected by two sheetpile structures. The in-water piers are designed for a horizontal ice load of 5.3 MN and a design scour of 12.2 m below the existing seabed. Recent ultimate load analyses indicate that the piers are capable of withstanding 13.3 MN ice forces. Extensive finite element analyses were performed on the steel structure. In addition, PN&D performed a full scale tension test on one spin-fin pile which showed an ultimate tensile capacity of over 5.0 MN.
The paper presents a discussion of the foundation design, design considerations for piles founded in saline permafrost, a summary of the finite element analyses of the piers, a review of the full scale pile load and driving tests, and observations for offshore design along north slope coastal areas.
ENVIRONMENTAL - REMEDIATION
Disposal of Drilling Wastes in Permafrost Prudhoe Bay, Alaska
Paul Hansen, Michael Snyder, and Per Wangstrom
Since the late 1960's, drilling wastes, mostly muds and cuttings, have been generated as a result of developing Alaska’s North Slope oil fields. These materials have been stored in above ground reserve pits formed by constructing gravel berms on the tundra next to the gravel drill pad at each drill site. The tundra and underlying permafrost, which is about 550 m thick at Prudhoe Bay, served as a pit floor.
For several years, North Slope operators have been evaluating and testing various methods for permanent disposal of these wastes. In early 1992, ARCO Alaska, Inc. evaluated burying the wastes in permafrost by conducting two pilot projects in winter. One project tested the procedures of excavating a drill site’s wastes; the other involved placing these wastes into a large excavation where they would remain permanently frozen. This paper describes the disposal facility portion of the two projects.
The East Sag Regional Disposal Facility was constructed near Drill Site 16. An ice road and ice pads were constructed to provide site access, material stockpile areas, and tundra protection. A mass excavation, about 107 m x 158 m x 12 m deep, was made using explosives and heavy equipment, then filled with about 180,000 m3 of drilling wastes from DS 3 and capped with clean material mounded above the surrounding tundra. Instrumentation was installed to measure the facility’s performance. The East Sag project was successful and demonstrated that drilling waste disposal in permafrost is feasible. The data obtained will be useful for a full-scale project.
Oxygen Supplies for Bioremediation in Tundra Soils
Daniel M. White and Robert L. Irvine
Aerobic soil microbes use oxygen as a terminal electron acceptor. Diffusion of atmospheric oxygen into tundra soil is hindered by the prevailing saturated conditions. Solid compounds that release molecular oxygen during breakdown were investigated as a source of oxygen for subsurface microbes during bioremediation of crude oil in tundra soils. Laboratory scale reactors containing tundra soil were incubated over a period of seventy-five days at 12°C. Reactors contained either sodium carbonate peroxyhydrate (Na2CO3•1.5H2O2) or calcium peroxide (CaO2) buried in the lower half of a bi-layer soil bed. Periodic measurements of soil pH and total heterotrophic organisms were used to assess the relative effectiveness of each compound. Organism concentrations reached 6.3 x 107 CFU/g dry soil and 6.3 x 106 CFU/g dry soil in reactors containing sodium carbonate peroxyhydrate and calcium peroxide, respectively. These values compared to a background value of 2.5 x 105 CFU/g dry soil. The concentration of organisms peaked after roughly 13 days of incubation in both reactors containing a peroxide. Although the organism concentrations fluctuated in these reactors, they generally remained above the background concentration during the entire 75 day incubation.
The growth of heterotrophic organisms was not appreciably stimulated further than 11 cm from the oxygen source in any of the experiments. Any application of soil phase peroxides for in situ bioremediation, therefore, should allow for a limited radius of influence. Probably the most promising application for solid phase peroxides is emplacement in landfarming boundaries to promote a biologically active barrier to contaminant migration.
Innovative Bioventing System Construction/Operation in Cold Regions
Kimberly K. Stricklan and Randall L. Mattzela
Air Force installations are wide spread in Alaska, ranging from Elmendorf Air Force Base (AFB) in Anchorage to Eielson AFB in Fairbanks to radar stations along the North Slope. The majority of these installations have environmental contamination from their 50 plus years of operations. By far the most pervasive types of contamination are from hydrocarbons. The Air Force has initiated several different cleanup technologies throughout the installations. This paper will focus on the cold regions engineering aspects of treatment technologies used at several sites. These sites include, but are not limited to, bioventing projects at Elmendorf AFB and a bioventing project at Eielson AFB.
Risk Assessment of Vapours in Cold Regions
Robert A. Perkins
The effects of cold environmental temperatures on the toxicity of inhaled vapours is explored by means of a literature search in order to determine what physiological parameters may be different in cold regions, followed by input of those physiological parameters into a physiologically-based pharmacokinetic model (PBPK) for vapour inhalation. The literature search provided sufficient quantitative information for estimates regarding increased ventilation rate and blood flow distribution during two types of cold temperature metabolic compensation, shivering and non-shivering thermogenesis. That information was input into a PBPK model for styrene, ether, ethanol, and methanol. The model indicated that the hydrophobic ether yields little increase in total systemic exposure at the higher ventilation rate. Styrene, ethanol and methanol had increased systemic exposure but the increase was not linear because of altered blood flow to the liver. In general, more vapours are absorbed in cold climates than in temperate climates. Qualitative data recovered from the literature indicated that liver function is disrupted in the cold, including shifts in enzymes and decreases in anti-oxidants. Oxygen free radical production is increased, with concomitant increases in lipid peroxidation. The conclusion is that vapours may be more toxic in colder than warmer climates, but the quantitative data for risk assessment is lacking.
BUILDINGS AND UTILITIES
Moisture Conditions and Control in Buildings in Fairbanks, Alaska
Fairbanks, Alaska has a very dry climate. With less than twelve inches of moisture (snow and rain) per year, the large interior land mass which surrounds Fairbanks would be sandy desert but for the low average temperature. Maintenance of the recommended level of 25% to 60% relative humidity in buildings in Fairbanks is complicated by: 1) the dryness of fresh air used for ventilation, especially after the cold winter air is heated to room temperature; 2) limitations of materials for use in the construction of functional thermal and vapour envelopes; 3) knowledge of, and incentives for, the correct installation of those materials by workmen, and 4) knowledge of, and incentives for, the planning, design and maintenance of building components necessary for containment of the appropriate relative humidity.
Included is a limited sampling of relative humidity in both commercial and residential buildings near Fairbanks, Alaska. Relative humidity levels in commercial buildings was found to be generally low. Residential levels are higher but mold and fungus problems are frequent. Details of some construction problems with thermal and vapour envelopes for commercial buildings are reviewed. Some suggestions are also offered for control of relative humidity in residence buildings.
Thermal and Vapour Performance of Insulated Assemblies
Axel R. Carlson
There is no question that increasing thermal values of insulation and eliminating air leaks has reduced energy requirements of buildings. However, the improper selection and placement of the insulation, vapour barrier and lack of ventilation has resulted in costly legal action to repair condensation-related maintenance problems. Unfortunately, condensation problems do not become apparent for 5 to 10 years after construction, long after the one year warranty is null and void.
Field experience and dew point studies indicate that moisture diffusing through the inner skin will condense near the outer skin and continue to build up as ice as the temperature gradient of the insulated cavity drops below the dew point and freezing. Accumulation of condensation and ice will be much greater in northern climates such as Alaska, Canada, Maine, Minnesota, Montana, North Dakota, etc., due to longer periods of freezing temperatures and higher vapour pressures. The freeze period varies in different parts of the country. It occurs 8 months at Prudhoe Bay, AK; 7 months at Fairbanks, AK; 5 months at Anchorage, AK and Duluth, MN; 4 months at Portland, MA; and less than a month at Portland, OR and Seattle, WA. As it often does, the winter temperatures may suddenly rise above freezing, which will allow the ice to melt and stain the floor or wall.
For example, the inadvertent placement of an impermeable exterior insulated and finish system (EIFS) panels on the outer face of an insulated stud wall led to costly condensation problems at the Butrovich Building, University of Alaska, Fairbanks, Alaska. Even though there was a polyethylene vapour retarder under the drywall, sufficient water vapour diffused into the wall and froze near the inner face of EIFS panels. The build up of moisture caused the fasteners to corrode. The resultant build up of ice caused some of the panels to protrude from the wall. Further, the inner face of some of the metal panels began to rust through, which allowed condensate to soak into the honey comb paper "insulated" core. This reduced the thermal value of the core. The panels were declared a safety hazard and were removed. The panels have been replaced.
ASTM symposiums indicate that EIFS walls are encountering serious moisture problems across United States and Canada. Dew point studies indicate that the thermal R-value of EIFS panels placed on the outside of insulated walls and other retrofitted assemblies should be 3 to 5 times greater than the interior insulated frame wall, depending on local outdoor temperatures. Further, the EIFS panels should be provided with some type of natural venting that will allow excess moisture to drain or evaporate and ice to sublimate.
A computer spreadsheet will be presented that simulates dew point conditions of insulated building assemblies. It will assist designers and builders in the proper selection and placement of the vapour retarder, insulation, and ventilation of the exterior skin. This necessitates the computation and tabulation of temperature gradients, dew point temperatures, vapour pressures, absolute humidities and relative humidities at various structural components of the insulated assemblies, particularly near the outer skin.
Snow Guards for Metal Roofs
Wayne Tobiasson, James Buska, and Alan Greatorex
Sliding snow and ice can damage property, kill people and overload lower roofs. In valleys, moving snow can roll the standing seams onto their side, violating the waterproofing seals within them.
Snow guards are used to hold snow on roofs. Some are attached mechanically while others are adhered to the metal roofing. One of the more successful adhesives requires weeks of above-freezing weather to cure properly and thus cannot be installed successfully during the colder portion of the year. Normal "hardware store" silicone was moderately successful as a snow guard adhesive. Plastic and aluminum angle snow guards with a peel-and-stick butyl tape did not survive even one mild winter.
Set screws are used to attach several commercially available snow guards to the standing seams of metal roofing. They fit some seams well, others, poorly. Self-tapping and self-drilling screws have been used with some success when installed with care. Stainless steel structural blind rivets performed well for us for two winters, but pulled out the third winter when heavier snow loads were present on the roofs.
Some damage to snow guards appears to be caused by workers using them for support when moving about on the roof. Improved design guidelines, standards and performance criteria are needed for snow guards on metal roofs.
Cold Weather Testing of Outdoor Gas-Fired Heaters
Debendra K. Das
Beginning with the winter of 1990, several outdoor gas-fired heaters ranging in rating from 43,950 W (150,000 Btu/hr) to 11,720 W (40,000 Btu/hr) underwent testing in Fairbanks, Alaska. The manufacturer had experienced field problems with similar units in cold climates. The objectives of the testing program were the following: 1) instrument these units with an adequate number of thermocouples and record temperatures at critical locations of the units, 2) document their performance and identify signs of frosting at air intake louvers and at the inducer fan, 3) monitor the performance of the electronic circuit board that activates gas valves, blowers and other controls as the ambient temperature goes down in the winter months, and 4) record through photographs the problems encountered and any malfunction as the ambient temperature dips to subarctic levels.
This paper presents details of the test setup for heaters, instrumentation and the data acquisition system and the measured temperature distribution in a number of heaters, tested during the past five years. Several problems encountered are described. A number of fix kits designed to be added on to these units to prevent the recurrence of these problems are explained. Cold start-up tests conducted at -40°C (-40°F) and their outcome will be discussed.
Although this testing was primarily designed to evaluate the cold weather performance of one manufacturer’s products, similar test setups, instrumentation and data acquisition systems can be adapted for other types of units. Therefore, engineers can evaluate and enhance the performance of small and large scale industrial heaters with minimal modification of the method described in this paper. The same technique can be extended to testing the performance of other furnaces with the objective of improving their performance at any ambient temperature.
Utilities and Systems for the New U.S. South Pole Station,
Amundsen-Scott Station, Antarctica
Steven Theno and Dick Armstrong
The U.S. has occupied the geographic South Pole continuously since 1956 with the Amundsen-Scott Station. The planning and design for a third generation station is currently underway. This paper reviews the primary utility systems serving the existing facilities and discusses the systems proposed for the new station.
Cold-Related Electric Power System Considerations
John D. Aspnes and James W. Cote
This tutorial paper describes cold-related electrical power system problems and suggests potential solutions, based upon a review of relevant literature and discussions with electric utility and utility equipment engineers located in several high-latitude countries. Although not directly attributable to cold climates, electric power quality and geomagnetically-induced current effects are also concerns of high-latitude electric power system designers and operators, and are discussed.
GEOTECHNICAL - SOIL PROPERTIES
Iron (II) Armine Complex Soil Stabilization
David A. Hemstreet and Ted S. Vinson
The vertical displacement of soil resulting from frost heave can cause significant damage to foundations and roads. Also detrimental is the related problem of instability due to the presence of excess water when the segregated ice in the soil mass thaws. A laboratory testing program was conducted to verify the suitability of an iron (II) amine complex compound (ACC) to serve as a stabilizer for roadway embankment soils against frost heave and thaw weakening. Specifically, the frost heave and thaw weakening response of a soil from Homer, Alaska, was monitored with concentrations of ACC varying from 0.0 to 3.0%. The frost heave was evaluated with the segregation potential concept, and the thaw weakening was evaluated with a measurement of resilient modulus. It was observed that the addition of small amounts of ACC greatly reduced the segregation potential of the test soil. After one freeze-thaw cycle, a slight increase in the resilient modulus of the test soil was observed with the addition of small quantities of ACC.
CPT in Cold Regions Engineering: A Logging and Design Tool
Richard Fortier, Branko Ladanyi, and Michel Allard
The Cone Penetration Test (CPT) has been used as a logging tool in cold regions engineering to define the spatial distribution of permafrost and degree of ice bonding in soil. It is also a useful design tool for determining the in situ creep parameters of frozen soils. The creep settlement and bearing capacity of permafrost under a deep circular load can be predicted from an appropriate procedure and an interpretation based on the model of an expanding spherical cavity in a viscoelastic-plastic medium.
During the thaw period of 1992, a field investigation was performed in a permafrost mound at Kangiqsualujjuaq, Northern Quebec, to evaluate the performance of the cone penetration test as a logging and design tool. The influence of the physical properties of permafrost on the point resistance was also studied as a function of the core penetration rate. The frozen soil layer between 0.75 and 2.10 m in depth subject to the largest temperature variation was investigated. The point resistance profile of this layer was determined weekly over a two-month period from 8 series of four load-controlled CPTs. The physical properties of permafrost were also measured on core samples recovered from drill holes close to each series.
The point resistance was strongly dependent on the temperature, pore water salinity, unfrozen water content and ice content of the frozen soil, and penetration rate. The CPTs results were also interpreted using the spherical cavity expansion model in terms of reference strength and creep exponent for a given strain rate. This interpretation was used to predict the strength of similar frozen soils measured with triaxial compression tests. A good agreement was noted between the measured strengths and the strengths predicted from the CPTs for comparable conditions. The CPT is a useful tool in cold regions engineering to quickly investigate permafrost behaviour and to predict the creep settlement and bearing capacity of permafrost.
Soil Thermal Properties for the Design of Underground Structures in Cold Regions
J. E. Steinmanis, Deepak Parmar, H. S. Radhakrishna, and A. S. Judge
A reliable method of measuring soil thermal resistivity using the thermal probe is presented. A field and laboratory survey of 100 Canadian soils was used to compile a thermal properties database. The soils were grouped according to the Unified Soil Classification System (modified) and the thermal dryout curve (thermal resistivity versus moisture content) envelopes defined. Although the thermal dryout curve for a given soil may be placed within a specified envelope, its exact shape and position are determined by other parameters (i.e. dry density, organics, mineral composition, particle shape, fines content, etc.) and their complex inter-relationship. The influence of ambient temperature on the thermal resistivity was investigated. For wet soils above 0°C, resistivity decreases as temperature increases; at 0°C there is a dramatic reduction (20 to 40%) in the resistivity; below 0°C resistivity decreases as temperature decreases.
Behaviour of a Sand in Frozen and Unfrozen States
Christopher W. Swan
This paper presents the results of high-pressure triaxial compression tests on dense Manchester Fine Sand (MFS) in both frozen and unfrozen states. Frozen sand specimens consisted of pre-formed and consolidated-then-frozen specimens. Unfrozen, isotropically-consolidated undrained (CIUC) or drained (CIDC) tests were also performed. Special testing procedures allowed accurate measurement of specimen load-deformation behaviour from small (0.001%) to very large (20%) axial strains.
In general, frozen MFS tests exhibited substantially higher moduli, upper yield stresses and peak strengths than unfrozen tests performed under similar conditions. In addition, the modulus and upper yield stress for unfrozen MFS is strongly dependent on the effective confining pressure (s’c) while the modulus and upper yield stress for frozen MFS is independent of s’c. The post upper yield stress-strain behaviour (ea greater than »2%) is strongly affected by the level of confinement for both frozen and unfrozen tests.
ENVIRONMENTAL - WATER AND WASTEWATER
Occurrence and Significance of Cryptosporidium parvum and Giardia lamblia
in Surface Waters on Alaska’s North Slope
Michael R. Pollen, Cindy L. Christian, Craig D. Nordgren, and Johathan D. Pollen
This paper describes the results of a 1995 water quality sampling program in 10 water sources used by Native villages across Alaska’s Arctic Coastal Plain, conducted by Northern Testing Laboratories, Inc. (NTL) of Fairbanks, Alaska. The focus is on the parasitic protozoans Giardia lamblia and Cryptosporidium parvum. Giardia is currently one of the definitive organisms in the Surface Water Treatment Rule, incorporated into the State of Alaska Drinking Water Regulations (18 AAC 80, May, 1994). At least one or both of these microorganisms were detected in each of the ten water sources during one or more rounds of sampling. Overall, eight of the sources had Giardia lamblia and eight had Cryptosporidium ssp. This is a significant treatment concern for rural Alaskan villages.
Wastewater Treatment Facility Aeration Project
Gary L. Eddy
In September 1992, the Nome Joint Utility System (NJUS) took ownership of a two celled sewage lagoon. The Wastewater Treatment Facility (WTF) was designed as a sludge holding facility and primary sewage treatment for the City of Nome.
During the first year of operation the WTF did not meet the Discharge Permit requirements of the Alaska Department of Environmental Conservation (ADEC). The City of Nome is permitted to discharge sewage below 120 mg/l BOD5 and 120 mg/l Total Suspended Solids. In the summer of 1993, the WTF created a major odour problem from spring break-up to freeze-up. The City of Nome directed the NJUS to fix the problem of non-compliance with ADEC and the odour problem.
In the spring of 1994, the Wastewater Treatment Facility Aeration Project was designed and constructed by NJUS. The new Aeration Project went into service on November 7, 1994. NJUS has been in compliance with ADEC permit requirements and the Aeration Project is performing as designed.
The abstract will outline the initial design, basis of design and construction of the WTF aeration project. Operating characteristics and results of the WTF will be presented prior to aeration and after aeration equipment was installed. Recommendations and conclusions are given.
Case History of a Lined Wastewater Treatment Lagoon Failure
Kelly S. Merrill and Matt Stephl
This paper describes the failure of a lined wastewater treatment lagoon in a south central Alaska community. Its objective is to provide valuable insights regarding key design and performance issues for all designers of such facilities in cold region areas. The treatment plant, including a lined aerated lagoon, was placed into service in 1982. The 114 million-litre (30 million gallon) lagoon was lined with 1.1 millimetre (45 mil) reinforced chlorinated polyethylene (CPER). The lagoon liner system failed in August 1991, allowing sewage effluent to escape into the ground. The failure included development of large bubbles below the liner, rupturing of air piping, and formation of large tears in the liner. This paper describes evaluation of the most likely failure mechanisms and development of a repair scheme for the lagoon that minimizes the potential for these failure mechanisms to reoccur. Possible failure mechanisms include gas formation below the liner, development of air pockets below the liner from fluctuating groundwater levels, liner damage by abrasion from concrete anchor blocks, liner damage from oversize bedding material, liner damage by wind-driven ice, and other factors. Design features of the new liner system, including liner type, are described. The remedial design included a two-cell lagoon that would allow one cell to be drawn down for maintenance and repair without putting the entire lagoon out of service.
Cold Temperature Nutrient Removal from Wastewater
Jan A. Oleszkiewicz and Shahnaz Danesh
In the process of biological removal of nutrients (N and P) from wastewater, low temperatures affect primarily the rates of nitrification reactions. Biological phosphorus removal (BPR) is less influenced by low temperature and if the source of short chain volatile acids (SCVFA) is readily available, the process would be efficient at wastewater temperatures below 5°C. Sidestream production of SCVFA from primary sludge, however is required in continuous flow processes. Prefermentation of the whole wastewater may be necessary to enhance BPR for smaller plants utilizing the sequencing batch reactor (SBR) concept.
Remote Monitoring and Technical Support for Drinking Water Systems
in Remote Communities
Daniel W. Smith, Stephen J. Stanley, and Dennis S. Prince
Successful operation of drinking water facilities requires monitoring of water quality parameters to provide the information necessary for process control. The drinking water quality reporting required by authorities in Alberta for small communities involves the analysis of one sample per day. For most small communities this is the extent of their entire sampling regime. It is questionable whether a single sample per day is adequate to provide the required information for the operator to achieve control of the treatment process and assess overall drinking water quality. Small remote communities have another complicating factor in that the operators are more isolated from technical support. A possible solution to these difficulties is remote water quality monitoring which will essentially provide continuous monitoring and technical support to help resolve problem situations.
Presented are the results of continuous remote monitoring of turbidity and free chlorine from the treated water sampling point of three water treatment facilities. The results indicated that finished water quality parameters varied considerably and were not adequately represented by daily samples. The data demonstrate that there was difficulty in meeting guidelines due to this variability.
Meeting drinking water quality standards can be difficult for communities. Operators of remote water treatment plants must be given the appropriate tools and support if they are going to meet the challenges of water quality that they face. The use of on-line instruments is one of the most effective ways to monitor water quality for process control and information collected can be monitored remotely to provide the operator with informed technical support to meet water quality challenges.
Demonstrating Brine Water Wells and Toilets for Deering, Alaska
Robert H. Lundell
Eight saline water wells were drilled within the Alaska Native community of Deering for use as toilet flushing water. The wells successfully located a brine water source below permafrost ranging in depth from 30 to 91 feet (9.1 to 27.7 m). Pumps were set in four of the wells and plumbing installed to provide the brine water to toilets in three homes and the community building. The systems have now successfully operated for 18 months.
Drinking Water Quality in Small Northern Communities
Daniel W. Smith, Stephen J. Stanley, and Dennis S. Prince
The heightened public awareness of environmental issues has brought with it increased public concern with drinking water quality. All communities are faced with meeting higher water quality standards with aging facilities and limits to fiscal resources, but it is the smallest communities that face the greatest challenge.
Presented is an evaluation of drinking water quality for the communities in the Alberta portion of the Peace and Athabasca River Basins. There are roughly 180 drinking water facilities in the region with roughly 105 surface water facilities and 75 groundwater facilities. The evaluation was based on existing data obtained from Alberta Environmental Protection (AEP) and data and information collected during site visits to 38 communities. The existing data included AEP’s treated water survey results which had 460 samples from 85 locations in the basins and 72,000 microbial samples taken at all locations in the basins over a seven year period from 1988 to 1995. The information gathered from the site visits included analyses of grab samples of raw, treated and distributed drinking water for trihalomethanes (THMs), microbial parameters and other routine drinking water quality parameters.
The evaluation of the drinking water quality indicated that generally small facilities produced a lower quality drinking water than larger facilities and there was a strong argument that some small facilities were having difficulty meeting Canadian drinking water quality guidelines with regard to microbial standards. The data also indicated that several facilities would not meet the THM standard of 100 ug/L.
It should be noted that the findings for the Peace and Athabasca River Basins area are not unique, data from the rest of the province showed a similar situation with small communities producing poorer drinking water than large communities. Similar findings have also been reported in the United States. These findings highlight difficulty many small facilities have in producing an acceptable quality of water.
Three-Dimensional Simulation of River Ice Jams
Mark A. Hopkins, Steven F. Daly, and James H. Lever
A three-dimensional discrete element model coupled with a one-dimensional depth-averaged usteady hydraulic model is used to simulate river ice jam formation. Ice runs are arrested by an ice control structure consisting of cylinders spaced across a channel. This type of structure is typically constructed in small, relatively steep rivers to cause temporary ice jams in areas where flooding is not a problem, to protect downstream areas where recurrent flooding is a serious problem. The three-dimensional discrete element simulation consists of several thousand floes. Each floe is a flat circular disk with arbitrary diameter and thickness. Feedback between ice floes and water is through water drag on floes and partial blockage of the channel by floes. The simulations begin by releasing a large concentration of ice floes upstream of the structure at the flow velocity. As the ice floes move downstream, collisions between neighbouring floes and collisions between floes and the channel bottom and ice control structure are explicitly modelled. An ice jam is initiated by arching of floes between the control structures. The momentum of colliding floes and water drag cause the jam to thicken. The arrival of additional ice causes the jam to progress upstream. Concurrently, the ice forces on the structure are determined.
Dynamics of River Ice Jam Release
Hung Tao Shen and Shunan Lu
Field observations have indicated the probability of violent ice runs with extremely high water velocities and rapid water level rises following the release of major ice jams. A complete quantitative description of such an event does not exist due to the difficulties in collecting data on water and ice movements in the field. In this paper, an analytical formulation for ice jam release is presented. A two-dimensional numerical model is developed and used to provide a better understanding on the dynamics of ice jam release.
Evaluation of Flow Resistance in Ice-Covered Channels
Florin Braileanu, Robert Ettema, and James Wuebben
Considerable debate surrounds the evaluation of boundary roughness and, thereby, flow resistance in ice-covered channels. The debate revolves around how to characterize and combine the influences, on flow resistance, of bed and ice-cover roughnesses. The highly variable nature of boundary roughness and the empirical framework of all resistance relationships amplify the debate. The present paper addresses the debate and suggests it is time to move on from the customary use resistance equations (for example, the Sabaneev equation) based on Manning coefficients.
A New, Low-Cost Ice Control Structure Part 1: Concept Development
James H. Lever, G. Gooch, and A. Tuthill
Communities located on small, northern rivers can experience severe breakup ice jams. While flood damages may be significant locally, they are often too low to justify conventional flood-control structure. Environmental concerns also tend to render these structures unattractive. We have developed a new, low-cost structure to control breakup ice jams on small rivers. It consists of massive sloped blocks, partially buried in riprap, placed across the river adjacent to a natural floodplain. The blocks will arrest a breakup ice run and form a stable, partially grounded ice jam. Trees or boulders on the floodplain retain ice pieces in the river channel while allowing flow to bypass the structure. Large gaps between blocks allow easy fish and canoe passage. Part 1 of this paper describes the development of this concept, and Part 2 describes its full-scale performance.
A New, Low-Cost Ice Control Structure Part 2: Construction and Performance
James H. Lever, G. Gooch, and C. Clark
Hardwick, Vermont, on the Lamoille River, has experienced 10 ice-jam floods in the past 30 years, yet damages are insufficient to justify conventional flood-control measures. We constructed a new ice-control structure (ICS) in Hardwick, in partnership with the Town and the Federal Emergency Management Agency, to assess its potential to control breakup ice jams. It consists of four massive, slope-faced granite blocks, spaced across a 27 m wide river section adjacent to a treed floodplain, and cost $100,000, exclusive of land and design costs. We instrumented the site with pressure transducers and a video camera to record the performance of the new structure. The ICS experienced two mild breakup events during its first year of operation and held an ice jam for several hours during the more severe one. No flooding occurred downstream during these events. The field performance of the structure was similar to hydraulic model results for cases of thin, weak ice.
TRANSPORTATION - MANAGEMENT
Shakwak Highway Project - Construction Challenges
Robin Walsh, Donaldson MacLeod, and Dennis Cook
The Shakwak project in the northwestern Yukon involves the reconstruction of over 500 kilometres of highways located in the discontinuous permafrost zone.
As permafrost at this latitude is easily de-stabilized by construction activities, the road design incorporates a number of features aimed at mitigating permafrost related degradation.
This paper details some of the solutions implemented to address road embankment stabilization, cut slope stabilization, disposal of waste earth, reclamation, culvert settlements, and road surfacing. Observations are provided on the effectiveness of the reconstruction completed to date on the northerly part of the project from the White River (km 1,880) to the Yukon/Alaska border (km 1,966) which traverses extensive sections of thaw unstable permafrost.
Field Observations of Instrumented Highway Sections with Different Frost Protections
J. M. Konrad, G. Dore, and M. Roy
With freezing indices ranging from 800 to over 2,000 °C•day and frost penetration reaching up to 3 metres under pavement surface, frost action has always been a major concern for pavement engineers in the province of Québec (Canada). This paper presents alternative techniques to protect pavement against the detrimental effects of frost action. Field observations over the first freeze-thaw cycle of highway sections insulated respectively with saw dust, a sand/tire chips mixture and extruded polystyrene are presented. The instrumentation consisted of heave gauges, thermistors, TDR probes, piezometers. Falling Weight Deflectometer tests were also performed in fall to determine the mechanical characteristics of each test section. The data suggest that the test section insulated with saw dust performed well and had the best cost-performance ratio. The test section with styrofoam also performed well. The sand/tire chips layer did not prevent the frost from penetrating into the frost-susceptible subgrade. The field results of the control section were analyzed with FROST1D using the segregation potential. Predictions and observations were agreed well confirming the relevance of the SP-based approach for frost heave prediction in the field.
Vehicle Traction Performance Comparison for Alaska Winter Seasons
J. John Lu
Snow and ice conditions have been considered the main factors that contribute to reduced vehicle traction forces and potential traffic accidents during winter seasons. To increase vehicle’s traction forces on snow and icy surfaces, studded and non-studded winter tires have been used in cold regions. However, the use of studded tires causes significant pavement damage, such accelerated pavement rutting and pavement marking damage. Since the spring 1994, the Alaska Department of Transportation and Public Facilities has requested the Transportation Research Center at the University of Alaska Fairbanks to conduct several research studies related to vehicle traction performance on snow and icy surfaces in Alaska. The study summarized in this paper concentrated on the following aspects:
To evaluate these performances, field tests were conducted in the test sites on travelling roadways and parking lots. The ice surfaces were made by the fire department of Fairbanks International Airport using a water truck. The main traction performance measurements included: stopping distances, the maximum stopping G-forces (acceleration forces), the time necessary to reach a certain speed, and the maximum starting G-forces. This paper summarizes the study and presents research results.
Studded Tire Research in Norway, Finland and Sweden
Eric Johnson, Tony Barter, and David Sterley
In June of 1995, engineers for the Alaska Department of Transportation and Public Facilities journeyed to Norway, Sweden and Finland to investigate Scandinavian research into reducing the effects of studded tires on pavements. Many northern tier states in the United States have banned studded tires; since the 1970's, little research has been done in North America. The road administrations, road institutes, and tire manufacturers of Norway, Sweden and Finland have continued to do extensive research on studded tires. To solve the problem of stud damage to pavements the three countries researched stud design, tire traction, driver behaviour, aggregates, asphalt concrete, and asphalt mix designs. The solution to studded tire wear involved a three pronged approach. First, the countries legislated the use of lightweight studs: studs that weigh less than 1.1 grams. The core of the stud is tungsten carbide steel, but the lightweight sleeve is either plastic or aluminum oxide. This stud reduced pavement wear rates by 50 percent. Second, they used a Stone Mastic Asphalt (SMA) concrete mix for surface courses. This mix contains up to 70 percent coarse aggregate. The use of SMA can reduce pavement wear rates from 25 to 50 percent. Third, they found hard durable aggregates that resist studded tire wear better than aggregates from local material sources. They developed tests such as the Ball Mill Test, SRK Test and the Point Load Test. Their research showed that the commonly used wear and degradation tests do not correlate to pavement wear due to studded tires. The harder aggregates that resist studded tire wear are fine grained metamorphic and volcanic rocks and make up only 2 to 4 percent of the rock in Scandinavia. They have hauled this rock up to 300 kilometres for a wearing course. The use of these harder aggregates can reduce wear rates by a factor of three to five compared to using local aggregates.
GEOTECHNICAL - EMBANKMENTS
Strengthening Railroad Roadbed Bases Constructed on Icy Permafrost Soils
V. G. Kondratjev
Deformations of roadbeds on permafrost soils are due to permafrost degradation in the roadbed base. The principal measures used to ensure roadbed stability on weak bases or those subsiding under thawing usually are the following: making a reserve by the embankment width and height, placing the roadbed on the ballast, constructing forms, filing the embankment with rock, and cutting out ice-saturated bed soils and replacing them with a draining material compacted layer-by-layer, among others. These measures are essentially of a passive or reactive nature; they are aimed primarily at overcoming the consequences of existing permafrost degradation, they require expensive road construction and maintenance, and they do not solve the problem by ensuring roadbed stability on very icy permafrost.
A group of specialist working together have developed several methods of strengthening roadbed bases on very icy permafrost soils. These are based on adjusting the ratio of cooling and warming factors to reduce the average annual soil temperature and to preserve the original soils’ permanently frozen state. These methods include preventive removal of very icy masses (ice lenses) from a permanently frozen base, then refilling the cavities formed with a high consistency soil. Other proactive alternatives include:
In order to test the technological concepts described above for their efficiency in operating conditions, Mosguiprotrans has designed and is now constructing pilot experimental roadbed sections on the Berkakit-Tommot-Yakutsk Railway. The Baikal-Amur Railway has also started using some of these techniques, particularly snow cleaning.
Permafrost Formation and Aggradation in a 23 m High
Homogeneous Dyke: A Case-Study
J. M. Konrad and R. Ladet
In northern Quebec, where the average freezing index is 3,500°C•$day, permafrost conditions within an homogeneous earth-structure were noticed after several years of operation. Temperature evolution during one freeze-thaw cycle were automatically monitored during 1994-1995 as well as deformations of the downstream face and pore pressures at various locations. Permafrost conditions between 4 and 6 m below the crest and between 2 and 8 m in the downstream shoulder were observed in 1994-1995, i.e. after 12 years of operation. However, in the downstream toe area only a thin permafrost layer was detected owing to snow conditions and possibly advective heat flow from seepage through the drain. The average temperature of the permafrost zone was about -0.2°C. Downstream slope movements are induced by in situ pore expansion as the active layer freezes, leading thus to a solifluction deformation process. Finally, it appears that the horizontal drain remains operative despite the presence of permafrost.
Geotechnical Study and Remediation Design for Coal Mine Spoil
Instability in Discontinuous Permafrost - A Case Study
Andrew J. Hardy, Patrick G. Corser, and Daniel C. Graham
The cost effective remediation of an active landslide of coal mine spoils at Usibelli Coal Mine (UCM) near Healy, Alaska presented several geotechnical challenges. The slide currently encompasses approximately 37 hectares and has an estimated slide volume of approximately 4,000,000 cubic metres. The slide mass has a well documented history of seasonal movement with velocities as high as 13 cm/day. Despite these constraints, a stabilization method to address Poker Flats outslope conditions has been proposed. Primary tasks include the construction of surface water diversions, buttressing at the toe of the spoils, regrading of the headscarp areas, installation of nested piezometers with data collectors, and revegetation. Long term plans include the construction of a full toe drain and contingency plans for upgrading the buttress in subsequent years.
Full-Scale Test Studies on Prevention of Frost Damage for Retaining Wall
Reinforced with Geotextile
Lun Chen, Guangxin Li, and Wenfeng Huang
In the Hetao Irrigation Area, Inner Mongolia Autonomous Region, China, canal irrigation has a very important effect on the agriculture. The climate is very cold and dry in winter. The problem of frost action damage is widespread in hydraulic construction in the area. This paper presents full-scale test studies on prevention of frost damage for a 2 m high retaining wall reinforced with geotextile. The facing panel was made up of reinforced light precast concrete slab. The horizontal displacement of the facing panel, the strain of geotextile, and the soil temperature and moisture content were measured during the winter of 1993-1994 (the Frost Index FI=837°C day). Steel wires were used to measure geotextile strains in the retaining wall under winter conditions. The test results indicated that the displacement of the facing panel comprises of horizontal frost heave and unfrozen-soil compressive deformation of backfill. In the 0-0.3 m range near the facing panel frost heave occurred. In about the 0.3-0.9 m range from the facing panel the soil was compressed before freezing and heaved after freezing. Outside that zone the soil was compressed. The horizontal frost heave of backfill was 15-30 mm, while the horizontal displacement of the facing panel measured only 6 mm because the frost heave was partially counteracted by the compressive deformation of back unfrozen soil. Near the facing panel, the frozen soil formed a thick solid mass with great rigidity and strength and was approximately equivalent to a pseudo gravity retaining wall which resisted the frost heaving action of back soil.
Dam Construction in Northern Environment: A Numerical Study
Mu Shen and J.M. Konrad
The concept of design and construction of an earth dam with a permanently frozen core as a seepage barrier is not new for permafrost areas. This paper describes thermal analysis simulating various construction scenarios in order to obtain the initial temperature distribution within the earthfill dam as a function of design variables, such as climate, rate of fill placement, thickness of earth lift, placement temperature and ground temperature. The study showed that lift thickness and climate were the most important factors controlling temperature distribution in the core.
Predicting the Level of Frost Penetration into Landfill Covers
Horace K. Moo-Young, Jr., Thomas F. Zimmie, and Morris H. Morgan III
Freezing and thawing cycles may deteriorate the permeability of the liner or cap. One dimensional freezing tests are conducted in the laboratory using a frost measurement system to determine the temperature and time required to freeze slabs of paper sludge and clay used as landfill covers. Freezing of the material did occur, since soil resistivity increased steadily as the temperature decreased.
The temperature distributions within the one dimensional slab containing paper sludge and clay are compared to predictions based on a steady state solution for a thin plate. The temperature distribution within the one dimensional slab containing the paper sludge (solid-water mixture) undergoing freezing is compared to predictions based on a one dimensional heat condition model for a semi-infinite slab.
ENVIRONMENTAL - MANAGEMENT
Incorporation and Rejection of Alum Sludge Flocs by an Advancing Freezing Front
Philip J. Parker, Anthony G. Collins, and John P. Dempsey
Although freezing dramatically alters alum sludge flocs such that they dewater more readily, a fundamental understanding of this phenomenon is needed before widespread application is possible. In an attempt to do this, the ice/water interface in alum sludge was investigated using a microscope-mounted freezing stage. Using a 10x objective, the interaction of sludge flocs with the advancing interface was watched in detail. The dependence of floc behaviour on freezing rates, or interface velocities, were noted. Also, available models on particle/interface interaction were assessed.
Solid Waste Management in Rural Alaska
Henriette Molberg Hansen and Howard P. Thomas
Implementation of modern solid waste management practices in rural Alaska is problematic for a variety of reasons including the remoteness, lack of transportation, the severe climate, frequent lack of funding, limited opportunities for recycling, and presence of bears, to name a few. Cultural factors also enter into the picture.
As part of a Master’s Degree Program in International Technology Planning offered by the University of Aalborg in Aalborg, Denmark, a study was conducted in 1993-1994 of solid waste management in villages in the interior region of Alaska. Field work for the study was conducted by the first author and a fellow student during August 1993 as part of a traineeship which was provided under the direction of the second author.
Because of logistical constraints, the study had to concentrate primarily on villages on Alaska’s limited road system. Villages visited included Copper Center, Northway, Minto, Manley Hot Springs and Nenana. Available information was reviewed in advance of the visits and interviews were arranged and conducted with village elders, Alaska Department of Environmental Conservation staff and others. The Athabascan village of Minto was subsequently selected for further in-depth study as being uniquely representative of solid waste management problems in many Alaskan villages.
The paper describes the Interior Alaska setting, the waste stream and the regulatory background. It then goes on to describe waste sources, waste collection and waste disposal practices. Several engineering solutions are noted including ways of meeting current Federal Subtitle D requirements. However, obstacles loom large in terms of the climate, frequent lack of local government, lack of funding and cultural factors. The paper concludes with some comparisons between villages and regions and some comments on "appropriate technology."
Municipal Solid Waste Characterization in a Cold Remote Region
Abigail A. Ogbe and Christina Behr-Andres
A Municipal Solid Waste (MSW) characterization study was conducted in Fairbanks from May 1995 to April 1996. This study involved sampling, sorting and weighing the individual components of the waste stream. The sorted unprocessed MSW was analyzed using standard test methods of the American Society for Testing and Materials (ASTM). Properties such as bulk density, thermal characteristics (moisture content, non-combustible and combustible fractions), and gross calorific value (by oxygen bomb calorimetry) of each waste component was determined. Results show notable differences between Fairbanks waste generation and national averages that provide insight into the unique domestic and commercial waste-generating activities in a cold, remote region. Valuable data from the characterization study will be used to set waste management goals and track progress toward achieving those goals, that will yield economic benefits and increase landfill life in Fairbanks, Alaska.
Automobile Emissions Under Arctic Conditions Using Unleaded and
10 Percent Ethanol Admixed Gasolines
Robert J. Andres, Joseph D. Goldbach, and Frank L. Williams
During the winter 1994-1995 season, chassis dynamometer tests were conducted to assess the effect of different fuel types on automobile emissions under arctic conditions. Tests and measurements were conducted according to standard Environmental Protection Agency guidelines as cited in 40 CFR 86. The fuels chosen were regular unleaded gasoline and the same fuel with a 10 percent substitution by volume of ethanol (E-10). Ten vehicles, statistically representative of the Fairbanks automobile fleet, were tested at ambient temperatures of 20°F and 0°F. Chemical species monitored in tailpipe emissions included carbon monoxide (CO), carbon dioxide (CO2), oxides of nitrogen (NOx), and total hydrocarbons (THC).
The use of E-10, in replacement of unleaded gasoline, significantly decreased the emissions of CO and THC at 20°F. Reductions in CO emissions concentrations were not as pronounced at 0°F. Nox emissions increased with E-10 use, especially at 0°F. CO2 emissions concentrations did not significantly change with fuel type. These emission results are generally consistent with the physical and chemical principles that underlie E-10 use.
Air Quality at a Zinc/Lead Mine in Arctic Alaska
Charlotte MacCay and Jack Coutts
Cominco Alaska, is one of the largest zinc/lead mines in North America. The ore body is mined as an open pit. The ore is blasted and hauled to the nearby mill complex. At the mill, the ore is crushed and milled to a fine powder, then metal sulfides are concentrated in flotation cells. Floats from the cells are dewatered in filter presses. The filter cake is the metal concentrate.
The mine’s air quality dust problems were primarily associated with calm conditions, especially when associated with cold temperatures. Located in a closed valley, air movement at times is minimal, making the mine site particularly susceptible to cold air inversions. These conditions sometimes led to elevated levels of total suspended particulate (TSP) and air-borne lead.
Exposed ore, tracking of concentrates out of the loading facility, and resuspension of ore and concentrate dust from the road surfaces were felt to be the primary contributors to fugitive dust. To better control the fugitive dust, the company totally enclosed all crushed ore, reconfigured truck loading to minimize tracking potential, and employed more rigorous methods of dust control on road surfaces. The air-borne lead and TSP levels were reduced by more than 50%, but still exceeded the national ambient air quality standard (NAAQS) for lead in the winter quarter during cold, stagnant air conditions.
Part of the reason for fugitive dust and lead exceedances was the close proximity of the mine site to the ambient air boundary, which was originally set at the worker housing unit instead of at the property boundary. A reassessment of this situation which considered: the 24 hour on-call status of employees, a blood lead study of employees, and public access into the mine site resulted in redefining the ambient air boundary. With the ambient air boundary now set at the property boundary, as is consistent with other permitted facilities in Alaska, all NAAQS are now met.
The cooperative effort of the State of Alaska and Cominco Alaska, Inc. led to both a reduction in air pollutants and a workable solution for mine operations.
Life Cycle Cost Analysis of a Storburn Propane Combustion Toilet
Paul Ritz and Herbert P. Schroeder
Sanitary waste disposal problems in rural Alaska contribute to the high incidence of endemic enteric and other diseases experienced by people living in rural communities. These diseases include hepatitis, impetigo and others. More than 20,000 Alaskans use honeybuckets. It is widely accepted that the use of honeybuckets as a means of disposing of sanitary waste contributes to the disease problem. Mitigation of the problem is focused on finding more sanitary means of disposing of sanitary wastes. The long term goal of the Indian Health Service (IHS) is to install piped water and sewer in each community. An analysis of the cost data at the Public Health Service (PHS) indicates that a sanitary sewer line averages $60,000/household in rural Alaska. Interim measures have been developed to reduce human contact with the wastes. These measures include derivatives of honeybucket systems, community haul systems, and others. One possible disposal technique is incineration of the waste within each residence by using combustion toilets. Combustion toilets eliminate handling of sanitary wastes. This project involved the testing of a Storburn Combustion toilet. The Storburn toilet incinerates waste at 300°C using propane. Testing included monitoring of the exhaust stack temperature during combustion. Based on a five year useful life, tests indicate that for three adults, the toilet can be operated for $1,756 annually.
HYDROLOGY AND ICE MECHANICS
A Unified Viscoplastic Model for the Inelastic Behaviour of Ice
Jonah H. Lee and Michel Aubertin
A physically-based constitutive model is presented for the ductile and semi-brittle region of polycrystalline ice. The capability of the model in dealing with complicated behaviour of ice is first described. Constants of the model are then estimated from existing experimental data. Results for creep for the ductile and semi-brittle regions predicted from the model are then compared with the experiments. Important future experiments needed to further develop the model are then described.
Wortley’s Winter Wanderings: A Narrative
C. Allen Wortley
The paper consists of excerpts and passages from a longer unpublished 1993 manuscript entitled "Wortley’s Winter Wanderings: Reminiscences of an Iceman Who Cameth and Wenteth in the Great Lakes . . . narrative report to the University of Wisconsin Sea Grant Institute and others who may have wondered what I have been doing. ." Copies of the complete manuscript are available from the author. This paper describes some of my activities and observations over a period of 16 winters in the US and Canadian Great Lakes small-craft harbours.
Using Spaceborne Imaging Radar to Identify Lake Water Resources
on the Alaskan North Slope
Martin O. Jeffries, Kim Morris, and G. E. Liston
Spaceborne synthetic aperture radar (SAR) images are used to identify and differentiate between lakes that freeze completely to the bottom and those that do not in two areas of the North Slope in N.W. Alaska. At Barrow, on the coast of the Arctic Ocean, 60% of the lakes freeze completely to the bottom in mid-January alone and by the end of winter 77% of the lakes are completely frozen to the bottom. In contrast, 100 km to the south in the "B" Lake region, only 23% of the lakes freeze completely to the bottom and there is no sudden freezing of many lakes as occurs at Barrow. A physically based, numerical model is used to simulate ice growth on the lakes. The simulated maximum ice thickness is 2.2 m. Any lake where some part of the ice cover does not freeze to the bottom thus has some water >2.2 m deep. For those lakes where the ice cover froze completely at some time in the winter, the simulated ice growth curve provides the ice thickness at the time each lake froze completely to the bottom and thus maximum water depth. At Barrow, 60% of the lakes are up to 1.4 m/1.5 m deep and 25% are >2.2 m deep. At the "B" Lakes, 75% of the lakes are >2.2 m deep. Thus, there is a considerable contrast in lake depth and water availability between the Barrow and the "B" Lakes regions. This method is simple to implement, and the SAR data are relatively inexpensive and have sufficient spatial and temporal coverage; thus it could be used to determine lake depth and water availability on the entire North Slope and in other polar and sub-polar areas where shallow lakes are common.
TRANSPORTATION - PAVEMENTS
Design and Construction for Asphalt Pavements in Permafrost Areas:
Case Study of Qinghai-Tibet Highway
Li Ningyuan and Ralph Haas
Paving in cold climate, particularly in permafrost areas, requires special technical and engineering considerations. This is because under such conditions not only the properties of asphalt concrete at low temperature but also thaw settlement and frost heaving distresses have to be considered in pavement design, construction and maintenance. This paper first presents a general description of the Qinghai-Tibet Plateau Highway, which is the highest highway in the world in terms of elevation. It then discusses the main factors causing pavement surface distresses such as thaw settlement and frost heaving of the pavements in this permafrost region, and finally presents a practical assessment of asphalt pavement design, construction, maintenance and performance prediction. The case study includes: variation analysis of the upper boundary of the permafrost table movement under seasonally changeable environmental conditions, discussion of pavement distresses based on the observed data and field experiments taken from the case study, and evaluation of some empirical methods used for the determination of pavement thaw settlement and frost heaving in this particular permafrost area.
An Open Graded Base to Reduce Thaw Weakening in Flexible Pavements
Maureen A. Kestler
Open Graded Bases (OGB) and Rapid Draining Material (RDM) to promote horizontal drainage of water from pavement systems have not been used extensively in the United States until recently. Drainage layers are now required beneath most Army and Air Force pavements, whether rigid or flexible. To assess the effectiveness of an OGB within a flexible pavement in areas of seasonal freezing and to ultimately evaluate the optimum OGB location within a pavement structure, three test sections with an OGB layer at different depths within the pavement structure were constructed on a USDA Forest Service Road in Berlin, NH. The sections were monitored for surface and subsurface temperature, moisture content, frost heave, pavement stiffness, and meltwater (water introduced by freeze-thaw cycles) collected in the drainage layer. Compilation of field data from these sections constitutes the first in a series of steps to determine the optimum location within a pavement system (in areas of seasonal frost) for OGB placement. This paper discusses drainage test section design, construction, instrumentation, observations to date, and overall strategy for determining the optimal OGB location.
Pavement Design Applying Allowable Frost Heave
Frost heaving of roads is one of the reasons causing pavement damage in cold regions. In this paper, an approach to the design of pavement structures on frost-susceptible subgrades is presented. The frost susceptibility is described by segregation potential of the freezing subgrade. Design charts are presented both for mineral embankments and for insulated embankments. The thickness of the non frost-susceptible pavement structure or the necessary thermal resistance of the frost insulation can be determined as a function of the desired frost heave level and freezing index of the location at two degrees of frost susceptibility (segregation potential) of the subgrade. This design approach has been applied in the design of streets and car-parks in Finland from the late 80's.
Environmental-Induced Longitudinal Cracking in Cold Regions Pavements
Robert L. Scher
In cold regions, the orientation and timing of movements along longitudinal pavement cracks are direct functions of two general conditions; seasonal frost action and/or thaw-unstable permafrost foundations. Each category can be characterized by different crack patterns, magnitudes and rates of movement, and boundary processes. Understanding these differences are prerequisites to designing economical new embankments or repairs. Simplified models are presented to qualify the potential boundary processes causing longitudinal cracks in cold regions. A limited review of techniques for mitigating this type cracking is also provided.
Concrete Pavements in Tunnels
Josten S. Berg and Per M. Noss
In 1979 the field research project "Economical Concrete Pavements" was started. This main project was administrated by the Norwegian Road Research Laboratory and during the following years it involved several projects throughout the country. The goal with the project was to get reliable information in order to determine where and how to use concrete road pavements.
The concrete pavement in the 500 metres long Saetre tunnel in the City of Bergen, Norway was part of the entire project, which this paper will present, comparing and emphasizing the concrete slab variables versus the pavement wear and tear after 12 years of use.
The Saetre tunnel pavement consisted of 11 variable concrete sections cast on a 50 mm insulation board or directly on a prepared base course of rocks. The subgrade of rocks was the same throughout the entire road-tunnel. Other slab variables were the concrete thickness and the slabs were reinforced or not reinforced.
The main project was terminated in 1987, however, the Saetre Tunnel Research Project continued until the final registration was completed in the summer of 1991.
During the project period the pavement conditions were registered several times. Each time the pavement rutting, cracks, broken slab corners, peelings and asphalt repairs were registered. For measuring pavement ruttings, reference brassbolts were initially cast into the pavement shoulders and in the centreline for every cross-sections to be registered. Thus the pavement ruttings of the various slab construction could be compared for every year measured as well as the ruttings throughout the years. Some sections of the slabs had to be repaved during the research period, other sections were repaired with asphalt pavement materials. When the project started in 1979 the ADT was about 3,500. That increased to almost 9,000 in 1991. At the same period the ADT heavy trucks with an axel load of 8 to 10 tons more than doubled to 12% at the project termination in 1991.
In addition, a nearby tunnel only 200 metres farther north of the Saetre tunnel was constructed and paved with asphalt concrete in 1979. This tunnel has exactly the same traffic load and the same climatic condition as the Saetre tunnel. During the first project years the pavement conditions were registered at this tunnel too. The results were compared to the concrete pavements in the Saetre tunnel. It was repaved twice and since the first repavement in 1985 no registration has been performed in that tunnel.
Results from the pavement registration and comparison between the various slab variables will be presented. Of particular interest is the registrations of the slabs with an insulation board versus comparable slabs without any insulation.
The conclusions of this full scale test project are based on the pavement condition of the final registration in 1991 and the entire life span of the pavement of 12 years.
Pavement Distress Caused by Deep Heave in Anchorage, Alaska
Rupert G. Tart, Jr., Mark R. Musial, and Michael E. Krueger
In 1989 the authors of this paper were asked by the Municipality of Anchorage, Alaska (MOA) to conduct a study to determine why some of the recently completed pavements in the Municipality were showing signs of significant distress and cracking. Later in 1992, a follow up study was conducted. Since that time many of the original recommendations have been implemented by the Municipality and the results of these implementations have been monitored. This paper will summarize the findings of the two studies and will report on the performance of some of the pavements which have incorporated the recommendations presented in the two reports.
Minimizing Costs of Northern Highways by Using BST
Donaldson R. MacLeod and Robin Walsh
Bituminous Surface Treatments (BSTs) have been used in Northwestern British Columbia and the Yukon for the past 15 years. The area is characterized by remote locations with a harsh climate, bog and fen complexes and permafrost.
BST uses range from a form of dust palliative on very low volume roads to an affordable alternative to asphalt concrete on mainline highway systems which have traffic volumes of up to 1,000 AADT. Many of these roads have a high percentage of trucks associated with primary resource development.
There are differences between the management of BSTs and conventional pavements. In contrast to pavement overlays, overlays of BST surfaces do not restore the surface condition to that of a newly constructed BST because of the BST overlay’s inability to correct distresses such as rutting and minor distortions. Consequently ride smoothness is not maximized unless other measures are taken.
The development of regression and Markov modelling techniques for BST performance makes possible a comparison of different road surfacing options on a life cycle cost basis taking into account capital, maintenance and user costs. Such cost analyses of BST relative to dust treated gravel and conventional asphalt concrete surfaces indicate that it is a suitable surfacing alternative for northern roads.