COLD REGIONS ENGINEERING
Northern Resource Development
April 4-6, 1984
SESSION ONE: CONSTRUCTION MANAGEMENT
An Organizational Model for Coordination of Government Agencies Involved in
Permitting or Land Leasing for Large Scale Resource Development Projects
C. E. Behlke
Large scale resource development, inevitably, is affected by the impacts of governmental activities related to environmental laws, government rules, or public ownership of lands or resources required for the proposed development. The elected heads of large government entities generally support new, resource related development. However, a government’s agencies may move slowly, and, in an uncoordinated manner, impose conflicting requirements on the potential developer while, perhaps, not placing the specific development project toward the top of their priorities for timely consideration.
The economics of any expenditure of developmental monies, whether for exotic new forms of transportation or for resource development, are quite time dependent. Timing uncertainties for project completion and resultant uncertainty of the time for initiation of pay-back of the development are usually the worst enemy of projects which appear otherwise economic. Uncertainties of time delays which could result from governmental activities, related to the projected development, often move otherwise economic projects into the questionable category.
This paper presents a model for governmental organization of State of Alaska agencies, utilized during the state’s involvement in the initial phases of the (now dormant) Alaska Natural Gas Transportation System. The model was a carefully considered refinement of that utilized by the state during the construction of the massive Trans-Alaska Pipeline. This paper further describes the preliminary agreements, between project sponsor and the principal government entity involved, and the executive orders, of the elected head of the governmental entity, necessary for successful utilization of the model.
The model functioned extremely well for three years prior to the development project’s being shelved for economic reasons occasioned by the dramatic shift of energy economics in 1982. Inter-agency cooperation was extremely effective in reducing uncertainties and ambiguities for the development project. The model was also quite effective in the state’s coordination with the Federal Government’s parallel or, where provided by federal laws, overriding authorities in relation to the proposed project.
The Effects of Windchill on Labour Productivity for Cold Regions Construction
D. F. Jordan, R. S. Hawley, L. P. Haldane
Norman Wells Pipe Line Project
A. R. Pick, R. H. B. Sangster, J. D. Smith
Interprovincial Pipe Line (NW) Ltd. is building a buried oil pipeline from Norman Wells in the Northwest Territories to Zama in Alberta. Construction of the pipeline will take place during 1983, 1984 and 1985. Mainline construction will take place during the winter months, with the first work commencing in December 1983.
Permafrost occurs in high percentage of the route. The area is generally described as boreal forest with part of the route characterized by rolling terrain with numerous valleys and high flat terraces. Much of the rest of the area is flat, poorly drained and dominated by black spruce forest.
This paper describes the overall project development and presents some of the significant issues related to the design and construction of the pipeline.
SESSION TWO: PILE DESIGN 1
Load Capacity of Model Piles in Frozen Ground
O. B. Andersland, M. R. M. Alwahhab
Load capacity of friction piles embedded in frozen ground is dependent on the long-term adfreeze bond strength at the pile/frozen soil interface. This bond strength is dependent on several factors including type and roughness of the pile, loading geometry, soil type, temperature, ice and mineral volume fractions, and the presence of any impurities in the ice matrix. Three components of bond strength observed in tests included ice adhesion, friction, and mechanical interaction forces involving pile surface roughness. Experimental work showed that ice adhesion was mobilized at very small displacements and that failure (start of tertiary creep) developed before full mobilization of mechanical interaction forces. An increase in surface roughness (addition of lugs to the model pile) along with larger displacement greatly increased the adfreeze bond strength and load capacity. A summary of the creep data (load versus time for a given displacement) illustrated agreement between the measured load capacity and a curve based on Vyalov’s long term strength equation. A new method for prediction of load capacity is suggested based on Vyalov’s equation using parameters from tests on representative frozen soils at temperatures and loading conditions corresponding to the field situation.
Effect of Dynamic Loads on Piles in Frozen Soils
V. R. Parameswaran
An alternating stress as small as 5% of the static stress was found to accelerate the displacement rates of piles subjected to long-term loads in frozen soils, as well as the creep rate of frozen soil samples subjected to uniaxial loading under compression. This effect essentially reduces the bearing capacity of piles in frozen soils, and has to be taken into consideration in the design of foundations in permafrost areas.
Permafrost Temperature Profiles for Design of Piles by Creep Theory
R. J. Neukirchner
Evolution of the creep theory for piles in ice or ice-rich material has provided a vital tool for designing piles to meet imposed long-term settlement limits. However, work published to date has not focussed on the process of selecting an appropriate ground temperature(s) for long-term pile performance nor on the effects of pile creep rate variations due to annual temperature cycles.
The paper demonstrates that the mean annual ground temperature profile is the appropriate vehicle to use with creep based formulas for either predicting or designing for long-term pile movements. A discussion on year round pile creep variation is presented and a proposal is made to limit the maximum pile creep rate to some value which will prevent overstressing the pile/soil interface when the warmest ground temperatures occur. A tentative value for this limit is suggested.
SESSION THREE: COLD REGION HYDROLOGY
Modelling Design Flood Hydrographs for Glaciated Basins in Alaska
R. D. Black, J. H. Humphrey, C. J. Newton
A methodology was developed for determination of design hydrographs for planning of facilities in flood hazard areas of ungauged streams draining glaciers. For the same area and rainfall, glaciated stream basins have significantly longer duration and lower peak flows than non-glaciated streams. Both peak and duration of flow for design events must have reasonable accuracy to design dam spillways and to predict scour attack on banks, levees, bridge abutments, and buried pipelines. Although some regression techniques are available for estimating peak flows, they do not provide estimates of flow duration. The regression methods are also unreliable since they were derived using short records from stream basins with large differences in glacier area, elevation, and precipitation. A hydrograph synthesis model was developed to permit more reliable hydrologic estimates of flows. Application of the model was restricted to stream basins in south and southeast Alaska with significant glacier area and no potential for jokulhlaups. Meteorologic, hydrologic, and glacier data were available for flood events in Wolverine, Gulkana, Nuka, Lemon Creek, Herbert, and Mendenhall Glacier basins. The U.S. Army Corps of Engineers HEC-1 model was calibrated to observed flood events by varying precipitation, snowmelt, and routing parameters within reasonable limits. The calibrated models were then verified by synthesizing flood events not used in the calibration process. A procedure was presented for determining design flood hydrographs for ungauged glaciated streams. Recommended precipitation, air temperature, and wind speed relationships with elevation were provided. Antecedent conditions, firn routing, englacial routing and synthetic unit hydrograph parameters were given as a function of glacier zones.
Predicting Flow Rate in an Ice Covered Stream
H. S. Santeford, G. R. Alger
Ice-Related Flood Frequency Analysis: Application of Analytical Estimates
R. Gerard, D. J. Calkins
In cold regions ice-related floods can make a significant, and often dominant, contribution to the flood population. They should therefore be considered in a flood frequency analysis. However, in many instances, historical data for this purpose is lacking. Resort must then be made to analytical estimates of ice-related flood stages. This paper describes the determination and application of such estimates for a site on the Missisquoi River near Richford, Vermont.
SESSION FOUR: EXCAVATION IN FROZEN MATERIAL
Geologic Origin and Fill Properties of the Barrow Unit Materials
A. Mahmood, M. G. Schlegel, S. C. Schrestha
Pipeline Trench Excavation in Continuous Permafrost Using a Mechanical Wheel Ditcher
D. W. Hayley, D. V. Inman, R. J. Gowan
Experimental ditching tests were conducted with the Banister 710 Arctic wheel ditcher at seven sites judged to be representative of terrain conditions along a proposed pipeline route on Melville Island. Data obtained from the test program included machine performance with various types of experimental teeth, observation of frozen soil exposed in the excavation, characteristics of the spoil pile, and behaviour of the backfilled ditches after two thaw seasons. This paper concentrates on the geotechnical factors that affect ditchability of high arctic permafrost soils and the behaviour of ice-rich spoil when it is used as backfill over a pipeline. The most significant factor affecting ditcher progress was the extent and distribution of ground ice in the soils. The effects of ground temperature were evaluated by conducting portions of the program in the fall and spring. Soil temperatures were approximately 15°C colder in the spring, resulting in a 50 percent decrease in ditching rate. Backfill performance observations have been compared with those from a previous test where excavation was accomplished using explosives and backhoe. Substantially improved backfill performance was observed with ditcher excavated soil because of more uniform gradation of the frozen chunks and the smooth, non-fractured nature of the ditch walls.
Methods for Backfilling the Utilidor - Barrow, Alaska
M. J. Kaminski
The North Slope Borough is current designing and constructing an underground utilities system to provide sewage and water services throughout the Barrow community. The system’s main design element is a buried utility corridor sized for man access, heated with circulating water, and located in permafrost with high ice content. The aggregates available and environmental conditions in Barrow have produced unique design considerations for utilidor construction. In order to achieve a stable thermal state and protect the structural integrity of the utilidor, it was necessary to develop unique construction techniques for backfilling of the system.
Barrow’s aggregate source is littoral deposits of well rounded gravelly sands. The size and shape of the aggregate required placement of relatively thin lifts in order to achieve adequate densities through traditional dry placement and mechanical compaction. Placement of thin multiple lifts resulted in high construction costs, and the dry aggregate allowed uncontrolled infiltration of surface water into the backfilled trench with the potential for piping and thawing of the surrounding permafrost, due to convective heat transfer. A method for backfilling with a non-frost susceptible (NFS) slurry was developed that resulted in consistently higher densities and increased resistance to water infiltration and thawing of the backfill material. This paper deals with the design parameters, laboratory tests, and construction techniques used in development of the slurry backfill alternative.
SESSION FIVE: PILE DESIGN 2
Design of Vertical and Laterally Loaded Piles in Saline Permafrost
J. F. Nixon, R. J. Neukirchner
Recent advances in the creep analysis for vertical and laterally loaded piles in permafrost, together with data on the creep of saline fine-grained soils allow the presentation of some preliminary design charts for piles in saline permafrost. The effects of salinity, rate of loading and ground temperature are discussed, and incorporated as far as possible in the analysis.
The paper demonstrates that the basic analytical procedures for predicting vertical and lateral pile displacements are currently available. It remains to incorporate the data base for creep parameters appropriate for saline soil. This data base, although preliminary, shows general trends that indicate striking increases in both vertical and lateral displacements as the soil salinity is increased. Creep displacements of horizontally or vertically loaded piles can be 10 to 100 times greater for high salinity soils, than for the equivalent fresh water soils. Charted solutions are included in the paper for soils having uniform temperature/salinity profiles.
Design for Partially Embedded Piles in Permafrost
K. J. Nyman, H. W. K. Bird
Procedures for designing single pile supports to meet the intent of governing codes must consider the buckling as well as the bending and axial behaviour of the pile. Analysis of the buckling of a cantilever pile partially embedded in frozen soil is facilitated if an equivalent buckling length can be assessed.
In this paper, a general procedure is developed to determine the equivalent buckling length of cantilever piles partially embedded in frozen soils.
Behaviour of a Buried Pipeline Under Differential Frost Heave Conditions
B. Ladanyi, G. Lemaire
This paper presents the results of observations made during the first phase of operation of a large-scale model of a chilled pipeline, buried in two different types of soils. This task was a part of a joint France-Canada project to study freezing around a refrigerated pipeline in a controlled environment facility in Caen, France. In the test facility, a 273 mm in diameter and 18 m long pipe was buried at a depth of 30 cm in an 18 m long x 8 m wide x 2 m deep pit. Along the length of the pipe, half of the pit contained a slightly frost susceptible sand and half a very frost susceptible silty soil. The pipe was refrigerated to -2°C, and the ambient chamber temperature was held slightly below zero. The pipe and the two soils were heavily instrumented to monitor thermal and moisture regime, ground heave, and pipe deformations and displacements.
This paper deals mainly with the problem of soil-pipe interaction and presents a comparison of the observed pipe behaviour with that predicted by a simple analytical model derived from the theory of lateral earth pressure on flexible piles.
SESSION SIX: THERMAL REGIME OF RIVERS
St. Lawrence River Freeze-Up Forecast
H. T. Shen, E. P. Foltyn, S. F. Daly
An important element of the ice management in northern rivers is forecasting water temperatures to predict the time of ice formation. The freeze-up forecast provides needed information for planning flow regulations and scheduling of the close of a navigation season. In this paper, the relationship between variations of air temperature and water temperature is analyzed. An analytical expression for water temperature is obtained through the solution of a simplified convection-diffusion equation. The air temperature is represented as a combination of a harmonic function and short term fluctuations. The short term fluctuations are determined from National Weather Services forecasts.
The analytical solution for water temperature provides a new insight into the effect of air temperature variation on the variation of river water temperature. Using this solution a simple freeze-up forecast procedure is developed. The procedure has been applied successfully to the upper St. Lawrence River downstream of Lake Ontario.
Field Determination of a Heat Transfer Coefficient for Open Water on a Winter River
M. D. Miles, R. F. Carlson
Thermal discharge, when released into an ice-covered river or cooling pond, causes an area of open-water that is dependent on climatic factors and the heat input. This open-water is a major source of water vapour transfer to the atmosphere for the formation of ice fog in cold regions. A heat transfer coefficient (which characterizes the rate of heat loss from the water surface based on the temperature differential between water and air) is a significant factor in determining the area of the open-water surface. This coefficient is a function of radiative, conductive and evaporative heat loss, which are in turn functions of air and water temperature, wind speed and humidity.
The heat transfer coefficient may be determined for local conditions using field measurements, or by using theoretical or empirical equations published in the literature. Once the coefficient is determined, it may be used to evaluate the effects of future changes of the thermal discharge to the river system and, in general terms, to changes in the amount of ice fog produced.
This paper describes a field method for determining the heat transfer coefficient. The method involves a heat balance approach that determines the net heat loss from the open-water surface using heat input and output components. These heat balance components are determined from measurements of the temperature and flow rate of the thermal discharge, the river flow rate, and local air temperature. Open-water areas are measured and then compared with the net heat loss to determine the heat transfer coefficient for local conditions in heat loss per unit area per unit time per temperature gradient.
We compared our results to published heat transfer coefficients determined by theoretical or empirical equations. We found that the use of these equations may not characterize local conditions sufficiently and may overestimate the amount of open-water area caused by thermal discharges.
SESSION SEVEN: TRANSPORTATION 1
Construction and Monitoring of an All-Season Airstrip in Rural Alaska
T. G. Krzewinski, T. A. Hammer, J. Brittain
This paper presents the planning, construction and post-construction monitoring of an airstrip located in a remote area of northwest Alaska approximately 100 miles north of Kotzebue and approximately 60 miles inland of the coast. After construction was completed, thermistor strings were installed at several locations along the air strip to monitor short and long term effects of the air strip on the subsurface thermal regime. A two year data base has generally confirmed predicted performance.
Passive Thermal Stabilization of the Bethel Runway - A Construction Overview
G. P. Bradley, E. Yarmak
In an effort to stop the thermal degradation of permafrost in a 60 metre (200’) portion of the paved Bethel Runway 18-36, a system of two (2) phase (liquid-gas) heat transfer devices (thermoprobes) were installed during the winter of 1982.
Two (2) rows of thermoprobes were installed perpendicular to the runway centreline by drilling each probe at a slope of 15 horizontal to 1 vertical. The lengths of the thermoprobes varied from 29 metres to 59 metres (96’ to 195’). The length of the top row of probes were installed so that they crossed the runway and penetrated into the degrading permafrost. The bottom row of thermoprobes were installed to stabilize the edge of the high embankment, thereby preventing any slope failures which could allow settlement of the top row of thermoprobes.
The drilling was accomplished by two, two-men crews working 2-10 hour shifts per day. The drill used to install the 88.9 mm (3.5") outside diameter steel pipe was track mounted. To keep the drill bit free of cuttings, compressed air was forced down through the 88.9 mm (3.5") outside diameter pipe via a 16 mm (1/2") diameter steel pipe installed inside the larger steel pipe and connected to the drill bit.
The successful installation of the passive heat transfer system in the Bethel Runway has given valuable insight for future similar projects. Drilling modifications and improvements inspired by this project will allow similar projects to be constructed in a more expedient and efficient manner.
SESSION EIGHT: PILE DESIGN 3
Subgrade Thermal Monitoring of a Modified Pile Foundation
B. W. Santana, T. C. Kinney
An attempt to stabilize differential settlement in the pile foundation of the Central Gas Injection Facilities at Prudhoe Bay, Alaska resulted in a comprehensive subgrade thermal monitoring program to be undertaken in July 1981. The subgrade below the elevated, pile-supported modules was insulated and selected piling were converted to two-phase thermosyphons in an attempt to reduce subgrade temperatures in order to control pile settlement. Monthly temperature data are available since 1982 and biweekly data are available for 1981. Spatial distribution of data collection points provides near-surface data just below the insulation and data at depths to 9 m (30 ft) in locations with various surface conditions. Observations are summarized on the change in the subgrade thermal regime due to the effects of insulation, thermosyphons, and ambient conditions.
Use of Large-Diameter Piles in the Design of Offshore Arctic Structures
D. G. Anderson, T. D. Lu, I. P. Lam, L. C. Cheang, C. F. Tsai, H. Matlock
SESSION NINE: ICE REGIME OF RIVERS
Ice Regime Reconnaissance, Yukon River, Yukon
T. Kent, R. Janoweicz, R. Gerard, L. O. Lyons
Freeze-Up Flood Stages Associated with Fluctuating Reservoir Releases
C. R. Neill, D. D. Andres
Recent studies for hydropower development in northern Canada have given much attention to the potential effects of flow regulation on the winter regime of rivers, including levels and thicknesses of ice accumulations during freeze-up and break-up. Generally, increased flows during freeze-up result in higher, thicker ice covers in early winter. Fluctuating flows may detrimentally affect the stability of ice covers, particularly in the period just after freeze-up.
Abnormally high ice-pack levels occurred at Peace River town in early January 1982, associated with a particular combination of weather conditions and fluctuating released 400 km upstream. The water levels resulting from consolidation of a fresh accumulation type of ice cover almost overtopped flood dikes that had been constructed some ten years earlier. Analysis indicates that the phenomena were associated with an unusual combination of a thin ice cover formed rapidly in late December and a succession of discharge fluctuations over the Christmas-New Year period. Using field observations of water levels and ice thicknesses, it has been possible to reconstruct an approximate history of the chain of events and to analyze the phenomena in terms of river ice mechanics.
SESSION TEN: FOUNDATION DESIGN
Errors Associated with Calculating Freezing Index Values from Monthly Average Temperatures
W. M. Haas
Foundation Stabilization of an On Grade Structure
J. D. Gill
SESSION ELEVEN: THERMAL ANALYSIS
Analysis of Thermopile Design Using Computer Modelling Techniques
M. D. Teubner, T. L. Foreman, B. Stuckert
Two-Dimensional Simulation of Freezing and Thawing in Soils
H. P. Thomas, R. G. Tart, Jr.
Phase change produces some of the most dramatic volume and strength change effects on soils in cold regions. Numerical solution techniques provide powerful tools for analysis of real-world heat flow problems. In our engineering practice, we have found a two-dimensional finite-element computer program called "DOT" (Determination of Temperature) to be particularly useful. Capabilities of the program include an ability to handle transient as well as steady-state problems, arbitrary geometries, inhomogeneous materials and non-uniform initial temperature distributions. Example applications of the DOT program described in the paper include calculation of thawing around a warm pipeline in permafrost, thawing around warm oil wells in permafrost (including the influence of a convection surface), and frost penetration as a result of placement of gravel fill in shallow seawater on the arctic coast. Limited data are presented comparing predicted and measured thaw for one of the examples.
SESSION TWELVE: WATER SUPPLY 1
Design of River Intakes for Cold Climates
J. Hodgson, J. Slater
Seawater Intake Design Considerations for an Arctic Environment
J. M. Colonell, W. S. Lifton
Major design problems for seawater intakes on the Alaska Beaufort Sea coast include the need to deal with ice formation and ice forces for 8-9 months of the year. Intakes to be placed in shallow coastal waters must also be designed to resist effects of storm surge, wave forces, and sedimentation. These conditions combine to pose a high risk of entrapping fish and marine mammals that enter the intake area or the intake itself. Because these creatures (especially anadromous fish) form much of the subsistence base of native peoples of the Arctic, they are of prime importance as natural resources. Thus, the intake facility must be designed to exert minimal impact upon those organisms, while also providing a water supply of specified quality and reliability.
SESSION THIRTEEN: WATER SUPPLY 2
Health Aspects in Town Planning and Housing in Greenland
G. P. Rosendahl
The public health of Greenland population has improved considerably during the past 30 years. The main reason is the effective combating of the diseases and the change of the physical surroundings first of all of the housing. But it is difficult to distinguish the importance of development of housing from other reasons.
The tuberculosis which was the most frequent cause of death has been controlled. The infant mortality has dropped and the average age of the population has been doubled. This progress of public health is especially due to the better conditions of housing.
Because of economical reasons one had to build dwellings in a concentrated way on house areas and has chosen primarily to build blocks of flats and semi-detached houses. The number of patients with air passage diseases or with gastric infections were reduced drastically as people moved into the new houses with central heating and bath.
The house rent is rather high because it is based upon the very high construction costs in Greenland. Only by considerable subsidisation - up to 80% - it has been possible to provide healthy and proper houses for a population who’s occupation primarily comes from living resources.
Pangnirtung Water Supply Study
T. W. Lumsden, K. Siu
Pangnirtung is a community of almost 1,000 persons situated close to the Arctic Circle on Baffin Island. Water is obtained from a nearby stream during the warmer months and from an existing storage reservoir during the winter. Lack of capacity and operational problems with the existing reservoir have dictated the need for major improvements to the water supply system. This paper describes the existing situation and the evaluation of alternatives that was carried out to arrive at the most cost-effective solution to the upgrading and expansion of the water supply system.
Design and Performance of Earthworks Water Reservoirs in the Northwest Territories
L. B. Smith, A. Shevkenek, R. Milburn
Earthworks water reservoirs have been constructed by the Government of the Northwest Territories in eight communities to date, and it is anticipated that similar reservoirs will be constructed in a number of other northern communities in the future.
The design of these earthworks reservoirs accounted for a number of conditions which are unique to northern regions. These conditions include: the presence of ice rich permafrost; severe and extended winters; thick ice formations; high winds; a short construction season; limited availability of heavy construction equipment; and the logistical problems arising from the remote locations of many of the sites.
This paper outlines the major considerations involved in the design and construction of the existing earthworks reservoirs, with particular emphasis on those aspects which are unique to cold regions. The paper evaluates the performance of the existing reservoirs and identifies areas where reservoir design could be improved.
SESSION FOURTEEN: OFFSHORE DEVELOPMENTS
Construction Monitoring of Beaufort Sea Exploration Islands
R. G. Tart, J. M. Colonell
More than ten gravel islands have been constructed for use as exploratory drilling platforms in the Alaskan Beaufort Sea during the last five years In U.S. federal waters, the Minerals Management Service of the Department of Interior requires platform verification for all islands. Verification consists of two phases: first, adequacy of the design is evaluated and, second, construction of the island is monitored to ensure construction in accordance with its design. Described herein are observations, measurements, and instrumentation used to monitor the construction and performance of these offshore platforms. Design concerns are reviewed, including foundation stability, island stability and the environmental forces which could affect island integrity. The role of different construction alternatives is also considered with focus on uncertainties resulting from either summer or winter construction. Procedures are also recommended for monitoring the construction of gravel islands.
SESSION FIFTEEN: ENGINEERING GEOLOGY
Arctic Route Characterization: The Thaw Settlement Evaluation
C. L. Vita
Rockslides in the Canadian Arctic Archipelago
S. G. Evans
This paper reports aerial photo observations on five large rockslides in the Canadian Arctic Archipelago. Four large rockslides, involving Proterozoic gneisses, and which vary in volume between 5 x 106 m3 and 40 x 106 m3, are described from fiord slopes in the Hall Peninsula, Baffin Island. The rockslide at Cape Hotham, Cornwallis Island, which involves Paleozoic carbonates, is also discussed.
Since the movements have occurred along fiord margins and steep coasts, the potential hazard of waves generated by rockslide debris entering the sea assumes considerable importance in the planning of resource development and the siting of shoreline facilities in some areas of the Arctic Archipelago.
Nelchina Slide - Case Study
H. P. Thomas, E. G. Johnson
Geotechnical problems have posed frequent challenges for highway designers and builders in Alaska. The Glenn Highway, west of Glennallen, passes through an area of discontinuous permafrost consisting of glacial till overlying a heavily sheared and fractured claystone (Matanuska Formation). In 1972, a project was undertaken to straighten a 2 km section of the highway at the crossing of the Little Nelchina River (Milepost 137). The realignment involved construction of sidehill and through cuts in conjunction with embankment fills approaching a new bridge. Excavation from the cuts and embankment materials consisted of claystone on the east side of the bridge and frozen silty glacial till on the west side.
Not long after construction, failures occurred in the east cut slopes and a claystone waste berm started to erode. On the west side, the high embankment fill began to move laterally and the highway pavement began to break-up. Repair efforts comprising slope flattening and subsurface drainage were undertaken at the site starting in 1976. However, these efforts were only partially successful. Soon after the 1976 project, subsurface movements developed below the eroding waste berm on the east side which included part of the roadway.
In late 1982, a comprehensive study of the overall problem was undertaken. In this study, the influence of fill material used, presence of muskeg beneath some of the fills, strength loss of claystone foundation materials, presence of permafrost subsoils, and the strong influence of groundwater flow and its seasonal cycle were primary factors identified. Based on this identification, including a geologic and geotechnical field investigative program, a set of promising and innovative stabilization measures were developed and recommended. The success of these measures will be determined by continued monitoring of the area.
SESSION SIXTEEN: WATER SUPPLY 3
Alternate Proposal for Circulating Water Distribution Systems in Rural Alaska
J. T. Collins, E. Jacobsen
In parts of Alaska where water supply is limited and permafrost exits, heating and circulating water in insulated distribution piping is commonly practiced to prevent freezing. The successful design of a cost-effective recirculating water distribution system depends on providing adequate pipe insulation and on minimizing pumping costs.
A new, dual main distribution system, named the Tu-pipe system, is presented here that offers substantial benefits over various existing systems. Existing systems lack control over flow rates in the house service loops; the Tu-pipe system offers a visual meter readout of the actual flow rate, and a throttling valve to adjust that flow, in the house service loops. For home and property owners, the system provides the benefit of having the water main in the street right-of-way.
The best advantage introduced is a lower operating cost. The initial capital cost is offset when a substantial savings is realized in areas where power costs are high and other systems are not viable.
Sewer/Water Service Connections for Barrow Utilities System
R. W. Martin III, J. F. Sahlfeld
During the past three years, the North Slope Borough has been designing and constructing an underground utilities system which will provide sewer and water services for the City of Barrow Alaska. The portions of the utilities system which are subject to the greatest variety of loading conditions are the service connections to the individual buildings. This paper deals with the design and construction of the service laterals which run from the mainlines to the building being served. A typical service connection consists of a gravity sewer line and circulating water lines contained in an insulated conduit ("utiliduct") with insulated boxes, accessible from the surface, installed whenever fittings are required. The transition from the below ground utiliducts to the building connection point is made with a steel structure which has been designed to resist frost jacking and thermal expansion/contraction forces. The paper covers the theoretical design of the piping systems, restraints, utiliducts, insulated boxes and backfill materials, as well as descriptions of the construction process with emphasis on the problems encountered during construction and their solutions.
Water Supply and Waste Disposal on Permanent Snow Fields
S. C. Reed, J. Bouzoun, W. Tobiasson
This paper will summarize procedures and techniques for providing a water supply and for safe wastewater disposal at stations and camps on permanent snow fields. These range from temporary and transient field operations to large scale, permanently occupied facilities.
SESSION SEVENTEEN: ICEBERG STUDIES
Numerical Analysis of Impact of Small Icebergs on Semi-submersibles
D. D. Curtis, A. B. Cammaert, T. T. Wong, W. Bobby
Icebergs pose a major threat to offshore oil production in the Hibernia field. Bergy bits (visualized as the size of a small cottage) may drift or be propelled by waves into an exploratory drilling vessel. Bergy bits are especially troublesome because they may not be detected during storm conditions yet they could inflict considerable damage to a semi-submersible.
The iceberg/semi-submersible collision model considers three global and two local degrees-of-freedom for both objects. A force-penetration curve is specified for the iceberg and semi-submersible at the collision point, thus the equations of motion may be solved throughout time with the collision force computed by the program.
The local force-penetration relations for the iceberg are determined using the principle of conservation of energy assuming a crushing failure mode. The local force-penetration curves for the semi-submersible depend on the impact point. Impact-susceptible members include columns, bracings and pontoons.
The interaction model was used in a parametric analysis which considered variations in iceberg mass, force-penetration curve (impact point) and iceberg velocity. The parametric analysis revealed that the semi-submersible receives considerable damage before anchor pullout occurs.
Iceberg Impact Forces on Gravity Platforms
A. S. J. Swamidas, M. Arockiasamy
The paper presents an analytical procedure for computing the forces exerted on a gravity platform by the central/non-central impact of a large iceberg. The mathematical modelling of the impact incorporates a seventh boundary degree-of-freedom (at the impact interface) in the equation of motion of the floating iceberg. Both linear/non-linear behaviour is modelled for the seventh degree-of-freedom. Numerical results are given for central/non-central impacts of two sizes of icebergs, one a 5,000,000 t and the other a 12,000,000 t mass iceberg, drifting with velocities of 1.0 and 0.5 m/s. The maximum impact force exerted is about 6.0% of the weight of the iceberg. Non-central impacts cause larger impact forces.
Iceberg Stability and Draft Changes
N. Grande, Ch. Guillaud
Icebergs originate in the West Greenland glaciers and drift down the coast of Labrador. In their transit, they cross major shipping lanes as well as numerous offshore drilling sites, thereby posing a constant and unpredictable threat to ships, bottom installations and undersea cables.
In the past, it was assumed that icebergs with drafts in excess of the maximum bathymetric depth would be stranded until such time as the iceberg lost enough mass, by means of ablation to allow it to float clear. However, with the use of the side scan sonar, scour marks have been found in bathymetric "valleys".
For an iceberg to scour in water deeper than its draft at the time it crossed the bathymetric rise, something must have caused the iceberg to change its orientation in the water to a new stable position with increased draft. This paper will analyze the problem, determine the methods by which such a phenomena may occur, and quantify the draft changes that may be expected.
A computer model was developed to analyze the stability and energy conditions of a floating body. This model was used to determine the possible stable conditions as well as the energy needed to rotate an iceberg from one stable position to another. Four basic iceberg shapes (tabular, wedge, pyramid and drydock) and two draft change mechanisms (interaction with the sea bottom and calving) were analyzed. The method described in this paper may be applied to any site with relative ease.
SESSION EIGHTEEN: MATERIALS STUDIES
The Control of Frost Action in Unbound Materials
R. J. Kettle, E. Y. McCabe
This paper is concerned with the role of mechanical stabilization in controlling frost susceptibility. This has been assessed in terms of the heave, developed over a 250 hour period, of cylindrical specimens subjected to the Transport and Road Research Laboratory frost heave test. The basic soil matrix consisted of a highly susceptible mixture of sand and ground chalk. Three types of coarse particle - slag, basalt, limestone - were used as the stabilizing agent, and these were each subdivided into two particle groups - 20 to 3.35 mm and 37.5 to 20 mm.
The introduction of up to 50 percent of the selected coarse aggregates produced various non-frost susceptible mixtures. The influence of the coarse aggregate was very dependent on aggregate type, with aggregate size being less influential. The data has been examined to assess the role of these coarser particles in the freezing process including the effects of their individual characteristics. This clearly demonstrated the possibility of using a mechanical stabilization to control frost susceptibility and this was supported by the results of additional tests on natural soil. Heaving pressures are also reported and are examined in relation to frost the amount of aggregate added, nature of the aggregate and particle size. The addition of coarse aggregate to the matrix is shown to reduce the measured having pressures.
Geotextiles Used to Reinforce Roads Over Voids
T. C. Kinney, R. D. Abbott
The beneficial effects of geotextiles used to reinforce roads over soft subgrades have been well documented. A theoretical model is presented which demonstrates that currently available and economical geotextiles are capable of supporting roads of about one metre thick over voids in excess of two metres wide. There are many unanswered questions that must be resolved before the concept becomes routinely used. Full scale field tests are underway to help evaluate the most critical unknowns.
Analysis of Plain and Reinforced Frozen Soil Structures
S. Soo, R. K. Wen, O. B. Andersland
Plain and reinforced frozen sand beams were loaded incrementally in pure bending at -6°C and -10°C. For plain beams, the deflection rate (during secondary creep) showed a linear relationship with applied load on a log-log scale while experimental results of beams reinforced with a single 4.76 mm diameter steel bar showed a bilinear relationship. The observed deflection behaviour was a result of the combined effects of creep in tension, compression, and adfreeze bond.
Two-dimensional finite element models were developed to analyze frozen soil structures in multi-axial stress states. A weighting procedure which evaluates "effective creep parameters" for those in tension and compression was proposed to circumvent the difficulty arising from different material properties in tension and compression. For reinforced frozen soil members, bond behaviour between the reinforcement and soil was modelled by certain bond interface elements with non-linear properties inferred from experiments.
SESSION NINETEEN: WASTEWATER TREATMENT 1
Waterproofing and Heat Trace Provisions for Pre-Insulated Polyethylene Piping Systems
B. J. Corwin
The increased use of pre-insulated polyethylene piping systems as a solution for Arctic piping systems has created the need for more detailed design for specific project applications. Especially in permafrost environments or other areas where high water tables may be expected. Since the insulation is used as a protection mechanism to ensure against pipeline freezing or permafrost degradation, waterproof protection of the insulation and components is vital to overall system performance.
Another area deserving more detailed attention during design is the heat trace system which is used to ensure against freezing or to thaw a frozen pipeline. The designer must consider many factors in selection of the system to satisfy the particular needs of a specific project.
This paper reviews current trends in waterproofing and heat trace provisions for pre-insulated polyethylene piping systems and recommends design considerations and a few possible solutions for design of these important aspects of the overall piping system.
Temperature Effects on Onsite Wastewater Treatment and Disposal Systems
This paper reviews briefly temperature effects on aerobic and anaerobic biological processes relevant to onsite systems. It presents a summary of earlier studies related to temperature conditions in septic tanks and related systems. Summary temperature and performance data on a septic tank and tile field system, near Ottawa are presented in this paper with an analysis of the influence of temperature.
The investigation conducted near Ottawa on the efficiency of an experimental tile system did not show any specific trend between soil temperatures (depth dependent) and efficiency. It was however observed that generally periods of higher air and soil temperature (June to October) showed better efficiencies of treatment for most of the parameters studied.
Swedish Field Experiences with Chemical Precipitation in Stabilization Ponds
Swedish sewage treatment plant history shows a development towards compact plants. For smaller communities with big changes in flow and temperature, the compact plants offer several problems. Yearly studies of chemical precipitation in stabilization ponds have demonstrated an overall reduction of organic matter (as COD) with about 75% to a level of somewhat below 100 mg O2/l, and a reduction of total phosphorous with 90% to a level of about 0.7 mg P/l. These values were reached under ordinary operation of the plants and no optimization efforts have been made. All wastewater have been treated (no overflows).
Precipitation with slaked lime has given a good bacterial reduction (E.Coli, 44°C) at the high pH-values obtained.
Two tracer studies (Rhodamine B) have demonstrated the appearance of strong short-circuiting flows in ponds systems and the inserting of simple walls is recommended to avoid an at least hygienic risk. Sludge collection in ponds can be carried out by a dredger or by emptying the pond and using an excavator. Both ways have been successfully tried in full scale in Sweden. Dewatering the ponds sludge by natural freezing is an excellent process, as the time for collecting sludge can be chosen almost arbitrarily during a year. The lack of dimensioning rules is rather obvious, especially with respect to the experiences of detention times presented here. With a possible efficiency of about 10%, stereotyped demands for area are insufficient.
SESSION TWENTY: FROZEN MATERIALS BEHAVIOUR 1
Confining Pressure Influence on the Strength of Frozen Saline Sand
D. C. Sego, D. Chernenko
The results of a study into the influence of confining pressure and salinity on the strength of frozen sand confirm a dramatic drop in the strength of frozen sand with increasing soil salinity. The angle of shearing resistance is independent of soil salinity between 0.2 and 0.8%, while the cohesion is linearly dependent on the salinity. The study indicate, that, in the long-term frozen saline sand at a temperature of -7°C may not achieve much strength increase when the soil salinity is higher than 0.2%.
The Role of Ice Content in the Strength of Frozen Saline Coarse Grained Soils
B. J. A. Stuckert, L. J. Mahar
The strength of frozen soils is strongly dependent upon the ice content of the soil. In saline soils, the volumetric ice content is governed by the initial pore-fluid salinity for a specific temperature. In addition to the volumetric ice content, the distribution of the ice in the pores, and its temperature, play a critical role in defining the strength of the frozen materials.
A series of tests were performed on a uniform sand using a range of pore-fluid salinities (0 to 38 g/l) over a range of a temperatures (-2.0°C to -20°C). The effects of temperature and salinity are discussed and a generalized view of the role of ice content is developed based on a simplistic ice growth model. The measured strengths are accurately predicted over a wide range of temperatures and initial salinities. Based on a limited testing program, the effect of gradational characteristics on the ice growth, and hence the strength is discussed. Predictions using the model are compared against data available in the literature.
Engineering Behaviour of a Sand Containing Gas Hydrates
D. C. Sego, R. J. Wittebolle
A laboratory testing facility has been established in which sand samples with gas hydrates can be prepared and the mechanical behaviour of the samples studied. The samples have been prepared using Freon 12 as the hydrate former. The testing was conducted in a modified triaxial cell in which the load platens had been modified to contain sonic transducers. This allowed P wave velocities to be monitored before triaxial compression testing. The velocities were measured over a range of temperatures. Little temperature dependence of the P wave velocity was observed below 0°C, while, above 0°C the P wave velocity decreased significantly due to the presence of unfrozen water. The triaxial compressional test data indicates that, with proper sample preparation and testing technique, the hydrate bonded sand behaved in a manner similar to ice bonded sand.
SESSION TWENTY-ONE: TRANSPORTATION 2
Snow Roads for Pipeline Installation on the Arctic Pilot Project
K. M. Adam, R. F. Piotrowski, J. M. Collins, B. T. Silver
Snow access roads and work pads will be required on Melville Island in the high Arctic to support construction of a natural gas pipeline for the Arctic Pilot Project. Both structures are essential to protect the terrain from scuffing and wear that could lead to slumping and erosion on a scale large enough to threaten the integrity of the pipeline.
One key problem of using snow as a construction material in an arctic setting is finding enough snow. Another problem is that snow on Melville proved to be of a hard, dry, cohesionless type that does not set up and compact as does snow in sub-arctic regions.
To overcome the problem of limited snow deposition, the use of light-weight polyethylene snow fencing proved to be the solution. From research on snow compaction problems, it was possible to theorize that snow in the high Arctic could be compacted to form high-density snow roads capable of handling conventional large trucks at highway speeds and normal tire pressures.
IDE researched, designed, manufactured, and shop-tested two unique prototype pieces of equipment: one, for constructing a high-density snow pavement, and the other for patching of the pavement surface.
Cement Stabilization for Road Construction in Cold Regions
T. S. Vinson, J. P. Mahoney, M. J. Kaminski
In recognition of the need to better define the potential to use cement for stabilization of roadway materials in cold regions a laboratory and field program was conducted. Specifically, the cement requirements to stabilize roadway materials from Barrow, Alaska, were investigated in the laboratory at molding and curing temperatures of 0 to 20°C (32 and 68°F). Both Type I (general purpose or normal) and Type III (high early strength) cements were employed in the program. The laboratory test results indicate that the cement requirements for the material were for all practical purposes independent of the molding and curing temperature and cement type. Following the laboratory program, a 30 x 7 m (100 x 24 ft.) cement stabilized Field Test Section was constructed in Barrow, Alaska, September 1982. The wind velocity on the day of construction was 32 km/hr (20 mph) and the temperature was 0°C (32°F). The compacted mixture was covered with insulating blankets and allowed to cure for seven days after which time the blankets were removed. In June 1983, the Field Test Section was evaluated by measuring Benkelman Beam deflections under the design loading condition (a fully loaded "DJB" dump truck). The deflections measured indicated the roadway materials, cured over the winter months, were performing satisfactorily. A condition survey of the Field Test Section was conducted in October 1983, after traffic had been allowed on the Test Section for over one year. The survey indicated the Test Section was performing well with the only failures at the extreme edges of the shoulder.
Airport Pavement Overlays in Cold Regions
K. O. Anderson, H. Heimark
Numerous airports have been built within the past 30 years or so in the area under jurisdiction of the Western Region of Transport Canada. Many of these have asphalt pavement surfaces that have had or will require rehabilitation due primarily to roughness developed under the severe climatic conditions experienced in these regions. A description of pavement condition evaluation techniques used to establish the need for rehabilitation and construction history records on some projects is presented.
This paper is based on a runway overlay research project undertaken to study methods of asphaltic pavement rehabilitation with a view to minimizing reconstruction problems and costs, and extending the life expectancy of overlays. The scope of the work included a review of current literature regarding methods and materials for pavement improvement as well as several case histories of runways overlaid since 1980. A major part of the work involved a runway overlay project in 1983 at Yellowknife, NWT.
Problems encountered with overlays placed on badly cracked pavements include relatively large amounts of reflective cracking shortly after construction as well as during placement of the overlay. The joint sealing compound used to fill the cracks of the old pavement sometimes causes slippage and roughness to appear in the newly placed overlay. Several types of pre-overlay preparation have been used to alleviate some of these problems. These types have included cold-milling, heater scarification and selective crack treatment. A test section using a non-woven polyester type geotextile was placed on the Yellowknife project.
Conclusions based on experience gained on recent overlays and the 1983 runway overlay project are given.
SESSION TWENTY-TWO: WASTEWATER TREATMENT 2
RBC Treatment of Dilute Wastewater
P. W. Given
A pilot scale study was undertaken in Whitehorse, Yukon to investigate the treatability of dilute, cold wastewater with a rotating biological contactor (RBC). Dilute wastewater is generated at a number of northern communities because of water bleeding practices which are often required for utility system freeze prevention.
The raw wastewater was dilute and cold with total BOD typically less than 50 mg/L, filtered BOD less than 20 mg/L, suspended solids less than 40 mg/L, and temperature less than 8°C. The test RBC unit was very effective in treating this wastewater, providing removals in excess of 85% for the indicated strength parameters. However, very low organic loading rates (less than 2 g/BOD/m²•d) were required to enable this effective treatment.
Other major study conclusions were that:
Measures to reduce or eliminate water bleeding (and wastewater dilution) should therefore be considered as one means of improving wastewater treatment with RBCs.
RBC Wastewater Treatment in Arctic Resource Camps
R. J. Forese, K. R. Heuchert
During the past several years, with increased activity in Arctic regions, a growing need has developed for the efficient treatment of waste streams from relocatable camps in these areas.
A relatively recent development in sewage treatment processes, the rotating biological contactor (RBC), has been proven a viable process for the treatment of camp wastewaters. At present, there are approximately twenty-five RBC package plants located in resource camps in the Arctic regions of Canada and the United States.
This paper will primarily deal with camp wastewater characteristics, RBC plant design considerations, development of the package plant concept, and typical system layouts for common sizes of relocatable camps.
Also, actual operating experience of RBC camp package plants will be discussed, including problems associated with the treatment of camp wastes.
Rotating Biological Contactor Treatment Efficiency at Low Temperatures
D. J. L. Forgie
The rotating biological contactor (RBC) is a relatively simple and reliable means of providing good to high quality secondary wastewater treatment. This paper investigates the effect of low temperatures (<10°C) on RBC treatment efficiency.
While it is agreed that decreasing temperatures will decrease treatment efficiency, the exact nature of this decrease is not conclusive. RBC manufacturers use empirically developed temperature correction factors, a ‘ s, to significantly increase the RBC media area for low temperature (5°C to 13°C) applications. Use of the well known Van’t Hoff-Arrhenius and Streeter-Phelps models (which use a temperature activity coefficient, q) have been reported, but both the nature of the theory and the q ’s reported in the literature lead to a questioning of the validity of these models. At least one group of authors, Wu et al (1983), have developed empirical RBC efficiency models which are a function of loading, number of stages and temperature.
In an attempt to clarify this situation, 3 stage, 6.75 m², bench scale RBC units were operated under three steady-state flow conditions, treating a moderately high strength wastewater (BOD5 @ 400 mg/L) at nominal liquid temperatures of 15°C, 10°C, 5°C and 1°C. Results indicate that the effect of temperature on RBC treatment efficiency increases with decreasing temperature and that using the Streeter-Phelps model with a single, constant q is not valid. As an alternative, an empirical model of the effect of temperature was developed from the experimental data. For comparison purposes q’s were also calculated and reported for narrow 4°C to 5°C bands over the 1°C to 15°C range. Given proper loadings, RBC’s are shown to be capable of achieving good (>80%) removals even at extremely low temperatures (<5°C).
SESSION TWENTY-THREE: GROUND THAWING
Surface Modifications for Thawing of Permafrost
D. C. Esch
In preparation for various types of construction, mining, or farming activities in permafrost terrain, some initial thawing and consolidation of near-surface permafrost soils may be beneficial. Current scientific data indicate that a major climatic warming trend is now commencing as a result of man-induced increases in atmospheric carbon dioxide. Engineers should be aware that the future presence and thermal stability of permafrost cannot be assured, and thawing in advance of construction may be the best long-range alternative. Various components of the surface energy balance are analyzed to determine how to increase the solar heat gain of a soil surface during thawing periods. Six field test plots were constructed in 1980 with different combinations of vegetation stripping, gravel pad placement, surface darkening with asphalt, and clear polyethylene film coverings, to intensify the thawing of permafrost silt soils. Results of four years of observations on these plots are presented and discussed. By stripping the vegetation, an increase of 2.0 m in thaw depth was reached after 4 years. The addition of an asphalt coated gravel pad covered by a clear polyethylene film to create a greenhouse effect, resulted in an increase to 3.0 m in the 4 year thaw depth. The benefits, and drawbacks are discussed for each surface modification, and possible improvements are suggested.
Hess Creek Thermal Erosion Test Site: Frozen Cut Slope Surface Treatments
J. W. Rooney, A. C. Condo
Reliability Based Assessment of Thaw-Consolidation Problems
S. Banerjee, B. Datta
A methodology for the analysis of uncertainties and their incorporation in the prediction of the normalized dimensionless pore-pressure ratio V(z, t) for thaw-consolidation of frozen soils is presented. The linear-first order approximation of the statistical parameters results in the assessment of explicit reliability of predicting V(z, t) for specified design conditions. The reliability measure is developed as an alternative to the arbitrary safety-factor approach and to facilitate probability based design and analysis with explicit reliability measures.
SESSION TWENTY-FOUR: TRANSPORTATION 3
Freezing Degree-Days and Frost Penetration Under Roads: A Field Study
W. M. Haas, L. H. Winters
Synthetic Insulation in Arctic Roadway Embankments
M. E. Olson
Using synthetic insulation in roadway embankments is a recent development. In the Arctic it is used to prevent permafrost degradation and settlements. Criteria for choosing an insulation material are thermal properties, limits on moisture absorption and compressive strength at a preset deformation. Field and laboratory experimental results indicate that extruded polystyrene has a combination of properties that makes it more acceptable than other types of insulation. Over the years, extruded polystyrene has become the de facto standard for synthetically insulated roadway embankments.
Sand Specifications for Roadway Ice Control
The Alaska Department of Transportation and Public Facilities, Research Section, has tested several winter maintenance sands to determine which are best suited to reduce skid resistance. It was found that coal ash provided the best skid reduction properties. Concrete sand was superior to the normally used State maintenance sand. Fractured particles proved superior to rounded aggregate.
Windshield breakage is a major consideration in the selection of the maximum particle size. Tests showed that windshields could be damaged by particles as small as 6.4 mm travelling at a velocity of 48 km/hr. Rounded particles were found to do more damage than sharp aggregate.
SESSION TWENTY-FIVE: STRUCTURES
Design of Steel Plates to Resist Transverse Ice Loads
K. P. Ratzlaff, D. J. L. Kennedy
The economic design of steel caissons, for drilling and production platforms in the Arctic Ocean, formed from steel plates and supported by a rectangular grid of stiffeners, beams and girders, requires that the full strength of the plates be mobilized to withstand extreme ice forces.
An extensive literature search has not revealed that satisfactory solutions exist for the load-deflection response of transversely loaded flat plates beyond the elastic limit when taking into account both flexural and membrane action. Experimental data available in the inelastic range of behaviour are also limited.
By considering various limiting simplified behavioural modes for the load-deflection response of uniformly loaded flat plates of zero aspect ratio, possible load-deflection domains are established. The limiting responses investigated are: elastic-inelastic flexural action, elastic membrane action, inelastic membrane action with increased stiffness resulting from increased Poisson’s ratio in the inelastic range, elastic flexural membrane action, and action of a fully yielded cross-section in flexure gradually giving away to a fully yielded cross-section in tension. Within the domain so established, a load-deflection behaviour is proposed that is in reasonable agreement with the results of limited test data available. The results of a finite element analysis using the ANIDA computer program are also in reasonable agreement with the proposed analysis.
A comprehensive experimental program on transversely loaded plates with well defined material properties and boundary conditions is required. It is essential to establish the load-deflection response in the region where full inelastic membrane behaviour dominates.
Application of Ice Engineering to Bridge Design Standards
C. J. Montgomery, R. Gerard, W. J. Huiskamp, R. W. Kornelsen
Over the past decade, several advances have been made in the field of ice engineering. This paper represents an attempt to incorporate these advances into the ice load provisions contained in CSA Standard S6, Design of Highway Bridges. Suggested revisions to the Standard include modifications to the current formula for evaluating the dynamic ice force for crushing, the addition of a formula for predicting the force on inclined piers and addition of a procedure for reducing the magnitude of ice forces on small streams that cannot carry large ice floes. Specific design recommendations are also suggested for the evaluation of transverse forces, pressures from ice jams and vertical forces from ice adhesion. In addition, comments are made on the application of future research to the Standard.
SESSION TWENTY-SIX: FROZEN MATERIALS BEHAVIOUR 2
Thaw Strain of Laboratory Compacted Frozen Gravel
T. C. Kinney, K. A. Troost
Many foundation failures have been attributed to the settlement of fill material which was compacted while frozen. Frozen material frequently looks dry and forms what appears to be a dense mass using normal compaction procedures. Upon thawing however, it becomes obvious that the material was not dense and settlements on the order of 5 to 20 percent of the fill height are observed. This paper presents the results of a series of laboratory tests where frozen sandy gravel was compacted in a large mold using several different compaction techniques. The samples were then thawed, saturated, and subjected to dynamic loading, and the settlement was recorded. At compaction water contents of over about 4 percent it was not possible to achieve even minimum density, and at a compaction water content of 2% extreme compactive effort was necessary to obtain a material that would settle less than 2% of its height upon thawing. The inability of a material to be compacted appears to increase with increasing water content, smaller grain size and colder temperature.
Modelling the Resilient Behaviour of Frozen Soils Using Unfrozen Water Content
D. M. Cole
A layer of unfrozen water exists between the soil particle surface and the solid ice phase in a frozen soil at temperatures of practical concern. This layer owes its existence to the effect of field forces associated with the soil particle surfaces. Its thickness depends on factors such as temperature, solute concentration and specific surface area. Additional unfrozen water occurs within the polycrystalline pore ice as well.
The thickness of the unfrozen water layer strongly affects the mechanical behaviour of the soil-ice interface and, hence, the gross mechanical properties of the frozen soil. The total unfrozen water content is particularly useful since it reflects the contributions from a number of sources to the unfrozen water layer thickness. As a consequence, the unfrozen water content provides an excellent means for expressing mechanical properties in terms of such variables as temperature, salinity and specific surface area.
The mechanical property of interest in the present work is to resilient modulus, defined as the peak stress divided by the recoverable axial strain in a repeated load triaxial test. It is extremely sensitive to temperature just below the melting point, dropping nearly two orders of magnitude as the material thaws completely.
During the course of the resilient modulus testing, unfrozen water content data became available for the test soils. Upon analysis, it was apparent that the increase in unfrozen water with temperature was closely associated with the soil’s increased resilient deformation as temperature increased. Efforts to empirically model the temperature dependence of the resilient modulus in terms of the unfrozen water content proved successful and the results form the subject matter of this paper.
A Probe for Measuring Both Thermal Conductivity and Water Content of Soils
T. H. W. Baker, L. E. Goodrich
A two-pronged metal probe has been developed at the Division of Building Research, National Research Council of Canada, to simultaneously measure the thermal conductivity and volumetric water content of soils in the laboratory and in the field. Thermal conductivity is measured by using one prong as a transient line heat source probe. Using both prongs as a parallel transmission line, the apparent dielectric constant of the soil is determined by the time-domain reflectometry technique. Volumetric water content is related to the apparent dielectric constant by an empirical relationship valid for most soils. This paper describes the construction and use of the probe and presents some preliminary results obtained in the laboratory and in the field.
SESSION TWENTY-SEVEN: WASTEWATER TREATMENT 3
Cold Climate Septage Management
T. Tilsworth, G. V. Jones, J. M. Hargesheimer
Septage, the waste sludge resulting from septic tanks, has in recent times become a recognized but difficult waste to process. It is estimated that some 20 million septic tanks serve about 80 million people in the United States. A great deal of attention has been devoted to the design, construction and operation of septic tanks themselves and properly so. However, it is equally important to realize that unless the septage is periodically removed from the tank, the system will indeed be doomed to failure. Only during the past decade has septage received the attention it deserves.
This article reports on studies and research conducted by the University of Alaska and the City of Fairbanks, Alaska. Included are definitions, characterization studies, treatability evaluations, and recommendations for alternative processing.
The Impact of Raw Wastewater Discharge to Alert Inlet
J. A. Heroux
Located at 82.3N 62.0W, Canadian Forces Station Alert is the most northern permanent settlement in North America.
The wastewater produced by the 250 annual residents is currently discharged, without any form of treatment, into a small lagoon, open to the Arctic Ocean. The goal of this ongoing project is to evaluate such aspects as water quality, benthos sediments, plankton, fisheries, organic matter biodegradability relative to the ecosystem concerned.
The present paper discusses the first phase of the project. A characterization of the wastewater demonstrated that, to a certain extent, it could be classified as domestic sewage. This indicated that it was easily biodegradable and that few toxic effects could be expected from its discharge.
A physical study of the receiving body of water was also undertaken. Water samples were obtained throughout the lagoon and evaluated for physical, chemical and biological characteristics. Benthos and sediment samples showed the dispersion pattern of the wastewater and its effect on the bottom biota. A dye tracer study confirmed the trends shown by the distribution of the water quality.
This preliminary work tends to demonstrate that the impact of the wastes in Alert Inlet is relatively small and even somewhat beneficial to micro-ecosystems of the bay.
Diffusion Model Application to Sewage Effluent Criteria
J. Penel, D. W. Smith, G. Putz
A numerical transverse mixing model was applied to study the mixing of the Whitehorse sewage lagoons effluent within the Yukon River.
Transverse mixing was simulated downstream of the outfall at various water discharges for open water and ice cover conditions.
Municipal wastewater management guidelines in the Yukon Territory established two sets of water quality requirements: 1) an effluent quality requirement and 2) a receiving water standard outside of an initial mixing zone which is defined as a volume of water extending some distance downstream from the point of discharge.
The diffusion model was applied to the Whitehorse wastewater. The mixing results were compared with the draft license water quality requirements associated with the two most critical parameters of this study, namely the maximum permissible faecal coliform count, and the maximum permissible ammonia concentration related to fish toxicity. The environmental impact of a potential relaxation in requirements relating to fish toxicity were also evaluated. The transverse mixing model was shown to be a powerful and flexible tool for assisting in sizing a cost effective treatment facility.
SESSION TWENTY-EIGHT: BUILDING DESIGN
Building Air Exchange in Cold Regions
S. H. Kailing
The largest single building energy load in most northern buildings is heating of ventilating air. Construction of tighter buildings to minimize this load has sometimes resulted in serious indoor air pollution. An adequate means of measuring air exchange rates is needed in order for real progress to be made in this area.
This paper describes recent efforts by the Alaska Department of Transportation and Public Facilities to measure air exchange rates in a number of public and private buildings. Results of a baseline study performed during the winter of 1982-83 on seven Fairbanks buildings are discussed. The paper concludes that there is too much uncertainty in the SF6 tracer decay method. The Brookhaven National Laboratories method is recommended for further evaluation.
Heat Loss Factors for Building Foundation Insulation Systems
J. P. Zarling, W. A. Braley
Steady-state and non steady-state finite element analyses of the heat loss occurring from basement and slab-on-grade constructions have been performed. The amount of rigid foam insulation was varied on the perimeter of the walls and slab to determine the effectiveness of various insulation configurations. Annual heat loss per linear foot of wall or slab are reported for both Anchorage and Fairbanks, Alaska weather conditions and soil types using these various insulation configurations.
SESSION TWENTY-NINE: ICE ENGINEERING
Evaluation of Ice Bridges in the Vicinity of Fort Chipewyan, Alberta
R. A. Harrington, A. W. Lipsett
Northern communities are often faced with difficulties of accessibility by overland transportation. One such isolated community is Fort Chipewyan, Alberta, which is located on the north shore of Lake Athabasca in northeastern Alberta. Vehicular traffic can only reach the town during the winter months, so the residents depend heavily on delivery of supplies by means of a winter road which crosses three ice bridges. Difficulties in completion of one of these ice bridges led to an investigation of alternate routes for the winter road in order to reduce the number of ice crossings to only one and to enable earlier operation of the winter road. The results of this study include an assessment of loading and velocity criteria applied to ice bridges and an analysis of synoptic ice formation patterns on the candidate rivers considered for possible crossings. Field observations of ice formation patterns, water quality assessment and ice bridge loadings are described. Ice generation and formation patterns were found to differ significantly between some of the sites under consideration. The study concluded that relocation of the winter road was not feasible because the single crossing alternative would have to be located on a river which forms an ice cover later than the existing sites and is also subject to formation of open leads.
Long-Term Bearing Capacity of Ice Fields
A. M. Vinogradov
The long-term bearing capacity of ice fields subjected to static and quasi-static loading conditions is estimated on the basis of the structure-foundation interaction analysis. Two models of the foundation are considered, the Winkler model and the continuous solid medium. The time and temperature-dependent effects are treated using the concept of thermorheologically simple behaviour of linearly viscoelastic materials. The problem is solved by means of a modified version of the quasi-elastic method which reduces the viscoelastic interaction analysis to a sequence of identical elastic problems. Numerical examples provide an illustration of the developed solution technique.
Streamwise and Transverse Ice Loads on a Circular Load Pile
W. J. Huiskamp
Reactions of a circular load pile in both the streamwise and transverse directions to ice loads on a small stream in Alberta have been recorded. Ice loads were calculated by a dynamic interaction model between ice and load pile.
The dynamic model predicted much lower ice loads than a previously used static equation, indicating that ice-induced resonance in the load pile affects measured reactions. Data from the two strongest ice runs in 1974 and 1982 showed a maximum ice force of 824 kN. Transverse loads as large as 29 percent of maximum streamwise loads were recorded. Compressive ice strengths ranging from 212 to 964 kPa were calculated and these were similar to values found at another field location.
Ice Forces on Inclined Model Bridge Piers
F. D. Haynes, D. S. Sodhi
SESSION THIRTY: GENERAL TOPICS
Classification of Peats for Geotechnical Engineering Purposes
A. L. Burwash, W. R. Wiesner
This paper proposes a comprehensive classification system for peats that will be useful in geotechnical engineering applications. The system is styled similar to the Unified Soil Classification System which has been established primarily for inorganic soils. Examples showing how the system can be used are given.
Riverbank Erosion at Newtok, Alaska
L. A. Rundquist, J. K. Hearn, J. M. Colonell
The north bank of the Ninglick River in western Alaska is eroding at an average rate of 6 to 27 m/yr. The bank erosion is caused by the combined action of heat, waves, and currents. Because of the severity and nature of the erosion problem at Newtok, the protection required is extensive and expensive. By anticipating their problem well in advance, however, the residents of Newtok can approach the solution using less expensive methods designed to slow rather than stop the erosion. Decreasing the rate of erosion may allow the bank to stabilize naturally after several years. Based on preliminary analysis, a series of spur dikes constructed with riprap appears to be the most feasible solution.
Development and History of Helicopter Transportable Drills for Permafrost Regions
R. W. Innes
In 1969, proposals for pipeline construction from the MacKenzie River delta to northern Alberta, pointed out the need for extensive shallow geotechnical drilling in permafrost. Existing drilling equipment had not addressed the problems related to recovering high quality samples of delicate frozen soils. Consideration for environmental damage combined with the remote nature of the pipeline alignments, required that all activities be carried out with helicopter transportable equipment. The relatively high costs related to helicopter transportation imposed severe constraints on load sizes, quantities and equipment capacities. It became evident that development of a drill dedicated to operating efficiently under these restraints would be in considerable demand.
The Effects of Windchill on Labour Productivity for Cold Regions
D. F. Jordan, R. S. Hawley, L. P. Haldane
When discussing extremes in cold region construction, the difference in labour productivity rates versus temperature must certainly be included. Productivities frequently vary significantly within the same seasonal period and must be accounted for as part of the contractor’s bid as a risk factor. That risk may be reduced with better predictability of labour productivity for those workers exposed to the elements.
Productivity is a function of many elements; however, the effects of temperature are of primary importance when discussing cold region construction. By correlating wind chill factors to labour productivity, man-hour unit rates may be determined for a particular weather window. In those areas where the weather window is predictable for a given time frame, a labour productivity rate can be estimated.
Predicting Flow Rate in an Ice Covered Stream
H. S. Santeford, G. R. Algar
When an ice cover forms on an open channel, the conventional (open water) stage-discharge relationship is no longer valid. Currently, in the United States, winter flow rates are determined by cutting holes in the ice and making a conventional flow measurement using current meters. Such measurements are made on an average of one per month. Empirical techniques are then applied to provide estimates of the flow rate for periods between successive winter measurements.
In this paper a theoretically based model is developed which allows for a direct prediction of the under-ice flow rate using indicated stage, float depth of the ice, and the open water stage-discharge relationship. An example of field application is provided for illustrative purposes. The proposed model has the advantage of being: a) theoretically based, b) reproducible, and c) computer compatible. It is also shown that for the periods between measurements, considerable difference exists between the hydrographs based on the theoretical model and those obtained from the currently used empirical techniques.
Geologic Origin and Fill Properties of the Barrow Unit Materials
A. Mahmood, M. G. Schlegel, S. C. Shrestha
The North Slope of Alaska has experienced oil-related development, and general civil and utilities upgrading during the last decade. Granular materials suitable for foundation pads, road subgrades and utility backfills have been sought extensively and found with mixed success. Known data on the occurrence and index properties of granular materials in the western part of the North Slope, south of Barrow, Alaska, are summarized in the paper. The Gubik formation, and specifically its Barrow Unit, are the sources of granular materials in the area. These materials are generally rounded to sub-rounded sands containing some gravel.
Properties of the granular materials within the Barrow Unit have been investigated for the various potential uses, such as pad construction, road development and utility trench backfills. These materials are found in nature with an ice/moisture content of 3 to over 20 percent. The materials have been used at the natural moisture contents as well as after special processing such as heated drying.
A laboratory investigation was performed to evaluate fill placement characteristics of the granular materials. Compaction curves for thawed and frozen conditions were compared. The influence of placement methods (impact compaction, vibration and rodding), placement moisture content and compaction temperature (below and above freezing) on the laboratory thaw strain behaviour is presented.
Ice Regime Reconnaissance, Yukon River, Yukon
R. Gerard, T. Kent, R. Janowicz, R. O. Lyons
Aerial reconnaissance of the ice regime over some 800 km of the Yukon River, from Lake Laberge to the U.S.-Yukon border, was carried out over two years. The paper describes the nature and rate of freeze-up and break-up progression observed in the two years, and the number and distribution of polynas in mid winter. The latter were found to be closely related to the presence of islands. Freeze-up progressed reasonably steadily over the whole reach after initial lodgement occurred some 700 km downstream of Lake Laberge. Break-up had a totally different character in the two halves of the reach: downstream it was rapid and dynamic; upstream it was slow and thermal. It is concluded that field observations are still essential to develop an understanding of the ice regime of a river reach.
Errors in Freezing Index Values Calculated from Monthly Average Temperatures
W. M. Haas
The calculation of freezing index values from average monthly temperatures is attractive because it takes much less effort compared to calculating from daily maximum and minimum temperatures. However, there are errors involved in this method. To evaluate the magnitude of these errors, a study was made of the autumn change-over months for 29 successive winters for several weather stations in Michigan. The results indicate that errors as large as 97 degree-days C (175 degree-days F) may occur in the autumn change-over month, and that a trend between magnitude of error and seasonal freezing index is suggested.
Foundation Stabilization of an On Grade Structure
J. D. Gill
As the development of oil and gas production in Arctic regions progresses, numerous facilities were constructed to support exploration and operations. No area in North America exemplifies this more than the Prudhoe Bay area in Alaska. Although virtually all the developments took place in recent years when the techniques of dealing with permafrost have been well established, there have still been recurring problems with thawing of the permafrost and the associated settlement of the structures.
In most instances large camps, production facilities, and other buildings are founded on piles with or without passive refrigeration to induce a constant state of frozen ground around the pile. In many instances, air circulation below the structure allows the natural thermal regime to remain as undisturbed as possible thereby preventing thaw. However, a number of structures do not lend themselves to this construction technique due to either practical considerations or the excess cost of constructing them in this manner. Such structures are aircraft maintenance facilities and warehouses. Usually the return on the investment in such structures and the need for large open spaces preclude the use of pile support except on the outer walls. In the past techniques have been developed for keeping the subgrade frozen under such buildings. Ducted foundations with either blowers or utilizing convective air flow have been used successfully to keep buildings stable.
An interesting example of restabilizing an existing building at the Deadhorse, Alaska airport is presented in this paper. The building, an aircraft maintenance facility, was initially constructed utilizing an elaborate duct system to maintain the underlying pad and permafrost in a frozen state. After some years of operation, the system was rendered inoperative due to frozen water in the ducts and was subsequently disconnected. The building was constructed on a 5-foot pad of gravel and had a layer of insulation below it to reduce heat flow from the building into the pad. During the following years the combination of high internal temperatures and the lack of an operating active refrigeration system caused thawing at the permafrost below the pad and settlement of the structure resulted.
Upon examination it was determined that rather than restoring the original system to use by modifying it to accept direct flow-through cooling, it was advisable to install a passive cooling system and eliminate the long-term maintenance costs of the ducted system. The passive thermal probe installation was designed to be installed in the existing ducts below the insulation layer. The probes were then slurried in place and refreezing of the pad induced utilizing the new passive system.
Extensive temperature monitoring probes existed in the original gravel pad which provided data of the thermal state in the pad. New, deeper thermistor strings were installed in the pad, the subsoil, and the underlying permafrost to monitor the extent of the thawed zone and the freeze back rate. The data is compared to other similar installations in the Prudhoe Bay area.
Analysis of Thermal Pile Design Using Computer Modelling Techniques
M. D. Teubner, T. L. Foreman, B. Stuckert
A numerical model has been developed to aid in the thermal analysis of the design of structures in Arctic and sub-arctic regions. The model uses two-dimensional finite elements to simulate heat transfer through a vertical cross-section. A simple and effective technique, similar to that described by Rolph and Bathe (1982), is employed to simulate freezing and thawing. The model has been modified to simulate thermal pile operation in the modelled region. An analysis of mitigative design measures proposed for a building experiencing thaw consolidation has been selected to illustrate the application of the model. Several simulations were conducted: 1) characterize the existing thermal regime beneath the building in the absence of a detailed historical record and soil property data, 2) determine the sensitivity of the thermal regime to various thermal properties of the soil and boundary conditions, and 3) evaluate the effectiveness of a proposed mitigative design.
Design of River Intakes in Cold Climates
J. E. Hodgson, J. R. Slater
Municipalities and industrial installations in cold climates often rely on rivers for their source of water. These rivers usually experience ice cover conditions for a significant portion of the year. Each spring ice runs and, occasionally, ice jam conditions occur. These events are potential hazards to any structure that is located in or near the river. Rivers in cold climates require the consideration of these and other ice-related factors in the process of designing an intake.
This paper addresses the relevant considerations for the design of a river intake in a cold climate. Material discussed will cover freeze-up and break-up observation and analysis, maximum ice thickness calculations, water level estimate for low and high flow conditions, and field measurements that can be made to assist in developing parameters for design purposes. How these are applied for intake and pumphouse design will be demonstrated drawing on the experience of the writers on four recent projects located in northern Alberta.
Hess Creek Thermal Erosion Test Site: Frozen Cut Slope Surface Treatments
J. W. Rooney, A. C. Condo
The effect of thermal erosion on the thawing of ice-rich permafrost soil received considerable attention during both pre-construction and construction of the Trans-Alaska Pipeline System. Potential consequences of thermal erosion, including ground surface subsidence, downslope movement and redeposition of thawed slope material, headward erosion and severe gullying were considered and addressed during both the design and construction phases of the project.
Several methods of slope treatment were proposed in the design to reduce the potential impact of thermal erosion on cut slopes in ice-rich soils traversed by the pipeline. In 1973 Alyeska Pipeline Service Company constructed the Hess Creek Thermal Erosion Site to provide a study area for evaluating the performance of slope treatments being considered. The site was located between stations 1061+00 and 1065+00 on the Livengood to Yukon River segment of the Dalton Highway. Four treated cut slope test sections and one untreated cut slope section were constructed and both an instrument trailer and weather station were installed at the site.
The cut slope test sections, covered with insulative and/or reflective materials, were monitored over the summer and fall periods of 1973 and 1974. While significant sloughing of the treated slopes occurred, the urea formaldehyde foam and, to a lessor extent, the excelsior blanket, appeared to be effective in limiting short-term thermal erosion. The Urea formaldehyde foam, in the placed configuration, could not support vegetation except at crack openings, while significant vegetation was generated in the excelsior blanket sections and the untreated section.
The slope treatments evaluated were primarily anticipated to be utilized for retarding ground thawing rates and limiting initial thermal erosion and consequent soil redeposition potential at more critical or sensitive ice rich ground locations along the pipeline route. Only limited success was obtained and variations of these proposed treatments were occasionally utilized during construction.
Freezing Degree-Days and Frost Penetration Under Roads: A Field Study
W. M. Haas, L. H. Winters
Correlations were made between frost penetration under Michigan highways and the square root of accumulated freezing degree-days. Frost penetration was determined from methylene blue frost tubes which were read several times during the season. The data base includes readings from frost tubes located in the western half of Michigan’s Upper Peninsula, for seven successive winter seasons. The degree-day values corresponding to the frost depths were based on temperature records from sixteen weather stations in or adjacent to the study area. For analysis, the data were grouped according to Unified Soil Classification, pedological classification and AASHTO classification of the subgrade soils.
While the data refer to a specific geographic area, the results will be of interest to cold regions engineers for estimating the frost depths to be expected under roads with differing subgrade soils. The degree of variability associated with each correlation will be of value in estimating the risk of error in predicting frost depths for water supply protection as well as for designing frost resistant roads, airfields, and parking lots.
Ice Forces on Inclined Model Bridge Piers
F. D. Haynes, D. S. Sodhi
Tests have been conducted to measure ice forces on model inclined bridge piers. The angle of inclination ranged from 81° to 45° from the downstream horizontal. Other test variables were ice velocity, ice thickness and ice flexural strength. The model piers were also inverted to bend ice downward. The paper describes the measured ice forces and the modes of observed ice failure.