Permafrost and

Related Engineering Problems

in Alaska

GEOLOGICAL SURVEY PROFESSIONAL PAPER 678
Permafrost and

Related Engineering Problems

in Alaska

By OSCAR J. FERRIANS, JR., REUBEN KACHADOORIAN, and 

GORDON W. GREENE

GEOLOGICAL SURVEY PROFESSIONAL PAPER 678

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1969
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

Library of Congress catalog-card No. 76-602920

First printing 1969 

Second printing 1970

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price 55 cents (paper cover)
CONTENTS

Abstract- ____ 

Introduction. _ 

Permafrost- __ 

Definitions

_________________________ 1

________________________ 1

________________________ 4

________________________ 4

Origin and thermal regime _________________ 5

Areal distribution and thickness ______________ 6

Related geomorphic features ___________________ 8

Polygonal ground- ______________________ 8

Stone nets_ ___________________________ 8

Solif luction_ __________________________ 9

Thaw or thermokarst pits __________________ 12

Thaw lakes- __________________________ 12

Beaded drainage ________________________ 12

Pingos_ _ ____________________________ 12

Muck deposits _________________________ 12

Summary of geomorphic features- ____________ 14

Engineering geology-_______________________ 14

	I 'age

Engineering geology Continued

Engineering problems ____________________ 15

Thawing of permafrost ________________ 15

Frost heaving- _______________---__-- 17

Frost heaving of piles __________________ 17

Specific structure- _______________------_ 17

Railroads- _________________________ 18

Highways and roads_ __________________ 21

Airfields ____^_____________________ 28

Buildings- _ ________________________ 29

Dams ____________________________ 32

Telephone and power transmission lines ______ 33

Pipelines __________________________ 33

Utilidors __________________________ 34

Icings- ______________________________ 34

Conclusions _____________________________ 36

References cited _________________________ 37

ILLUSTRATIONS

Page

FIGURE 1. Map showing extent of permafrost zones in Northern Hemisphere ____________________________ 2

2. Map showing distribution of permafrost in Alaska- _____________________________________ 3

3. Block diagram showing where taliks can occur in relation to the active layer, suprapermafrost zone,

permafrost table, and permafrost- ______________________________________________ 4

4. Diagrammatic sketch showing the effect of surface features on the distribution of permafrost in the continuous permafrost zone_ ____________________________________________________ 6

5. Diagram showing relation of amplitude of ground-surface temperature fluctuations to amount of thawing- _ _ 6

6. Diagrammatic sketch showing the distribution of permafrost in the discontinuous permafrost zone,

Fairbanks area_ ___________________________________________________________ 7

7. Aerial photograph of coastal plain near Barrow, showing polygonal markings on ground surface caused

by underlying ice-wedge polygons ______________________________________________ 8

8. Aerial photograph showing polygonal markings on ground surface (caused by ice-wedge polygons) in the

vicinity of Meade River_ ____________________________________________________ 9

9. Photograph of ice wedge (ground ice) in permafrost exposed by placer mining near Livengood_ ________ 10

10. Aerial photograph of thermokarst mounds near Fairbanks- _________________--__----____--__ 11

11-15. Photographs of 

11. Thermokarst mounds near Fairbanks-_________________________________________ 11

12. Sorted stone circles caused by frost action in Alaska Range _ __________________________ 11

13. Large mass of ground ice in silt bluff near Fairbanks- ______________________________ 12

14. Thaw or thermokarst pit near Fairbanks ________________________________________ 13

15. Shoreline of a thaw lake about 40 miles northwest of Glennallen ________________________ 13

16. Aerial photograph of pingo in Yukon-Tanana Upland- _____________________-___--------__ 13

17. Diagram showing effect of gravel fill upon thermal regime. ________________________________ 16

18. Map showing location of transportation routes in Alaska ___________________-_-_____---_--- 19

19. Photograph of differential subsidence of roadbed along the Murphy Dome Spur of The Alaska Railroad

caused by thawing permafrost-_____________________________________ __________ 20

in
IV CONTENTS

Page

FIGURE 20. Photograph of differential subsidence of roadbed of Copper River and Northwestern Railway-_ ________ 21

21. Map of the Moody area on The Alaska Railroad showing landslides and slumps caused by thawing of

permafrost and remedial measures taken to combat them_ ______________________________ 22

22-27. Photographs of 

22. Landslide area at mile 353.5, The Alaska Railroad- _________________________________ 23

23. Polygonal ground in permafrost exposed by removal of vegetation by a highway crew_ _________ 24

24. Thawed lake sediments flowing around blade of bulldozer- ___________________________ 25

25. Gravel road near Umiat showing severe differential subsidence caused by thawing of ice-wedge

polygons in permafrost________________________________________________ 26

26. Slump block of fine-grained highway fill material near mile 113 on the Richardson Highway. _____ 27

27. Gully along edge of road caused by surface drainage thawing the permafrost in loess deposits- _ _ _ _ 28

28. Oblique aerial photograph of Chariot Site, northwestern Alaska- ____________________________ 29

29. Oblique photograph of tractor trail near Canning River, North Slope __________________________ 30

30. Photograph of frost-heaved piling of bridge ___________________________________________ 31

31. Geologic sketch of foundation conditions of frost-heaved bridge- _____________________________ 31

32-36. Photographs of 

32. Frost-heaved steel-pile bridge- ______________________________________________ 32

33. Roadhouse, mile 278.5, Richardson Highway- _____________________________________ 33

34. The schoolhouse at Glennallen ______________________________________________ 34

35. Fracture due to frost heaving of 4-inch concrete foundation of apartment house, Fairbanks- _ _ _ _ _ 35

36. Utilidor under construction at Fort Wainwright __________________________________ 35

TABLES

Page

TABLE 1. Mean annual temperature and precipitation data from representative stations in Alaska- ____________ 7

2. Common topographic features that indicate ground conditions in arctic and near arctic regions- ________ 14

3. Hypothetical example of seasonal frost penetration into silt in central Alaska and possible upward push

on 40-inch-perimeter pile (ground temperature constant) _______________________________ 17

4. Comparison of construction costs between permafrost and permafrost-free areas of the highway between

Rex and Lignite, Alaska- ____________________________________________________ 22
PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

By OSCAR J. FERRIANS, JR., REUBEN KACHADOORIAN, 

and GORDON W. GREENE

ABSTRACT

Permafrost, or perennially frozen ground, is a widespread natural phenomenon. It underlies approxinately 20 percent of the land area of the world. The 

>ermaf rost region of Alaska, which includes 85 percent 

>f the State, is characterized by a variety of perma- 

'rost-related geomorphic features including patterned 

ground, pingos, thaw lakes, beaded drainage, thaw or 

thermokarst pits, and muck deposits. Known permafrost thickness ranges from about 1,300 feet near 

Barrow in northern Alaska to less than a foot at the 

southern margin of the permafrost region. The distribution of permafrost is controlled by climatic, 

geologic, hydrologic, topographic, and botanic factors.

The extensive permafrost region of Alaska poses 

special engineering problems for the design, construction, and maintenance of all types of structures. Lack 

of knowledge about permafrost has resulted in tremendous maintenance costs and even in relocation or 

abandonment of highways, railroads, and other structures. Because of the unique geologic-environmental 

conditions that exist in permafrost areas, special 

engineering procedures should be used, not only to 

minimize disruption of the natural environment, but 

also to provide the most economical and sound methods 

for developing the natural resources of the permafrost region of Alaska.

INTRODUCTION

The recent discovery of potentially vast reserves of 

oil at Prudhoe Bay in northeastern Alaska (estimates 

range from 2 to 40 billion barrels) has focused attention on the geologic-environmental factors unique to 

the Arctic which pose special engineering problems 

for the design, construction, and maintenance of roads, 

railroads, airfields, pipelines, buildings, and other 

structures. Permafrost, or perennially frozen ground, 

is the most significant of these environmental factors.

A road and railroad from Fairbanks in interior 

Alaska to the Arctic North Slope have been proposed 

to aid in the development of the mineral wealth of

this remote and presently inaccessible region. Preparatory work is under way for the construction of an 

800-mile-long pipeline extending from the oil fields 

to Valdez, a year-round seaport. A winter road 

connecting Fairbanks with Sagwon on the Arctic 

North Slope has been completed. These major engineering activities are just a part of the overall construction effort that will take place in northern Alaska 

because of the recent oil discovery and because of 

potential future discoveries of other natural resources.

All this activity requires an understanding of the 

arctic environment, to establish sound cost-saving 

engineering procedures and to preserve the natural 

environment insofar as possible. In most areas 

where roads or buildings are constructed on permafrost, the procedures that cost the least in the long 

run are those that disturb the natural environment 

the least, and therefore, are conservation oriented. 

Generally, the initial capital investment is greater 

when correct procedures are used; however, maintenance cost is considerably less. If improper procedures 

are used, expensive maintenance cost far exceeds the 

additional expense of the initial investment, and in 

some cases, structures are damaged to the extent that 

they become unusable after just a few months or 

years. The financial losses caused by such problems 

as impassable roads, unusable airstrips, or damaged 

machinery in buildings which have settled differentially can be extremely high.

Very few people realize the geographic extent of 

permafrost or the magnitude of the problems it causes. 

Approximately 20 percent of the land area of the 

world is underlain by permafrost. Figure I shows the 

extent of the permafrost zones in the northern hemisphere where most of it occurs. In the southern 

hemisphere, the main land area underlain by permafrost is Antarctica. About 50 percent of both Canada 

and the U.S.S.R. and 85 percent of Alaska are within 

the permafrost zones (figs. 1 and 2).

To date most permafrost research has been carried 

on in the U.S.S.R.; major industrial cities have been
PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

FIGURE 1 Extent of permafrost zones in Northern Hemisphere.
INTRODUCTION

;^e

**o,

I/4V 

V^ntt^

OCEAN

r~

5j._J ALEUTIAN

1 *~

76' 178' 17»'

! West of Greenwich 

I ISLANDS O ^

"'

EXPLANATION

AREAS WITHIN PERMAFROST 

REGION

Mountainous areas, generally underlain 

by bedrock at or near the surface

Underlain by continuous permafrost

Underlain by discontinuous permafrost

Underlain by isolated masses of permafrost

Lowland areas, generally underlain by 

thick unconsolidated deposits

Underlain by thick permafrost in areas

of either fine-grained or coarseUnderlain by moderately thick to thin 

permafrost in areas of fine-grained 

deposits, and by discontinuous or isolated masses of permafrost in areas 

of coarse-grained deposits

Underlain by isolated masses of permafrost in areas of fine-grained deposits, 

and generally free of permafrost in 

areas of coarse-grained deposits

AREAS OUTSIDE OF PERMAFROST 

REGION

Generally free of permafrost, but a few 

small isolated masses of permafrost 

occur at high altitudes, and in lowland 

areas where ground insulation is high 

and ground insolation is low, especially near the border of the permafrost region

FIGURE 2. Distribution of permafrost in Alaska. Modified 

after Ferrians (1965).
PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

built in the permafrost region. This construction 

demonstrates that the deleterious effects of permafrost can be overcome, and that major development 

can take place in the arctic regions. In regard to 

the success of the Soviets, the following statement 

(Muller, 1943, p. 2) is pertinent: "It is worth noting 

that in Soviet Russia since about 1938 all government 

organizations, municipalities, and cooperative societies 

are required to make a thorough survey of permafrost 

conditions according to a prescribed plan before any 

structure may be erected in the permafrost region." 

The purpose of this report is to present a survey of 

some of the more important aspects of permafrost 

and to create an awareness of the tremendous problems that can be caused by constructing on, or otherwise disturbing, permafrost if proper procedures are 

not used. It is hoped that the information presented 

will facilitate the development of the natural resources 

of northern Alaska and at the same time minimize 

disruption of the natural environment.

PERMAFROST

DEFINITIONS

Permafrost is defined exclusively on the basis of 

temperature. It is rock or soil material, with or without included moisture or organic matter, that has 

remained below 0° C (32° F) continuously for two or 

more years. In most areas it has remained frozen for 

many thousands of years; however, permafrost can 

be quite young in areas where very recent sediments

Surface of ground

Suprapermafrost layer (ground 

above permafrost table including taliks, if present)

Permafrost table (upper surface of permafrost)

Permafrost (perennially frozen 

ground)

have been laid down, where very recent changes in 

the location of water bodies have taken place, and 

where man has disturbed the terrain.

Permafrost may be ice free at 0° C when the water 

it contains is saline or when it contains no water at 

all. The latter is commonly referred to as dry permafrost. When permafrost contains clay, substantial 

amounts of unfrozen moisture can persist at temperatures several degrees below 0° C because of the 

depression of the freezing point by capillary forces. 

Ice in permafrost can occur as coatings, grains, veinlets, or masses, and in unconsolidated materials it 

commonly acts as a cementing agent making the mass 

of unconsolidated materials hard as a rock.

The permafrost table is the upper surface of the 

permafrost, and the ground above the permafrost 

table is called the suprapermafrost layer. The active 

layer is that part of the suprapermafrost zone that 

freezes in the winter and thaws in the summer, or 

simply, seasonally frozen ground. Because water in 

the soil tends to reduce temperature fluctuations from 

summer to winter, the summer thawing and hence 

the active layer is deeper in drier materials. Seasonal 

frost penetrates down to the permafrost table in most 

places; however, if it does not, an unfrozen zone called 

a talik remains between the bottom of the seasonal 

frost and the permafrost table. Unfrozen zones 

within and below the permafrost also are called taliks 

(fig. 3). If the thickness of permafrost is increasing, 

permafrost is said to be aggrading, and if decreasing, 

permafrost is said to be degrading.

/Active layer (seasonally frozen 

ground)

/Talik (unfrozen ground between base of active layer 

and permafrost table)

/-Talik (unfrozen 

permafrost)

'round within

Talik (unfrozen ground below 

permafrost)

FIGURE 3. Occurrence of taliks in relation to the active layer, suprapermafrost zone, permafrost table, and permafrost.
PERMAFROST

ORIGIN AND THERMAL REGIME

Permafrost forms when the mean annual air temperature is low enough to maintain a mean annual 

ground-surface temperature below 0° C (32° F). If 

climatic conditions in an area change in such a way 

as to reduce the mean surface temperature below 

0° C, the depth of winter freezing will exceed the 

depth of summer thawing and if the mean surface 

temperature remains below 0° C, a layer of frozen 

ground will be added each year to the base of the 

permafrost until the downward penetration (aggradation) of the frozen ground is balanced by the heat 

flowing upward from the earth's interior. Thus, the 

thickness to which permafrost can grow depends 

upon the mean surface temperature and the geothermal gradient. The lower the temperature and 

gradient, the greater the thickness of the permafrost. 

In this manner, permafrost, hundreds of feet thick, 

can form over a period of several thousand years.

Because the formation of permafrost depends upon 

temperature at the ground surface, the thickness and 

areal distribution of permafrost are directly affected 

by the kind and size of natural surface features 

(bodies of water, topography, drainage, and vegetation) that act as a heat source or heat sink or as 

insulation. Changes in the surface environment such 

as would be produced by a transgressing (or regressing) 

sea, or building of roads and other surface structures, 

draining of lakes, and clearing of vegetation produce 

profound changes in the permafrost (Lachenbruch, 

1957a, 1957b; Greene and others, 1960).

Although the surface of the permafrost may be 

quick to respond to surface changes, it requires 

centuries, or tens of centuries, for surface changes to 

affect the bottom of the permafrost. Therefore, the 

present thickness and distribution reflect former 

thermal environments (Lachenbruch and others, 1966).

A few examples demonstrate how these considerations can be applied to make a qualitative appraisal 

of permafrost conditions beneath various surface 

features. (For quantitative calculations see Lachenbruch and others, 1962, and references cited therein.) 

Example 1. Shallow lakes freeze completely in the 

winter; thus, they behave like the active layer of the 

nearby terrain. However, the spring warming is 

accomplished efficiently by water circulating around 

and beneath the deteriorating ice, whereas the fall 

cooling is achieved inefficiently by conduction through 

the ice. The result is that mean annual temperatures 

on shallow lake bottoms are higher than those of the 

surroundings and permafrost is thinned beneath them 

(fig. 4). Example 2. Deeper lakes (greater than 6 ft 

deep) that do not freeze completely during the winter

have mean annual bottom temperatures above freezing 

and thus are underlain by a thawed basin. The 

permafrost beneath a thawed basin is also thinned by 

upward indentation (fig. 4). If the lake is drained, 

the thawed basin refreezes and expansion of the ice 

within it creates a pingo (see p. 12). If the minimum 

horizontal dimension of a deep lake is greater than 

approximately twice the local undisturbed permafrost 

thickness, the upward indentation coalesces with the 

thawed basin to form an unfrozen "chimney" through 

the permafrost beneath the lake (fig. 4). Such 

features provide a potential year-round source of 

ground water in regions of continuous permafrost.

A river behaves like a long thin lake, and the ocean 

can be viewed as a large deep lake (fig. 4). Example 

3. Well-drained areas will generally have summer 

surface temperatures several degrees higher than 

nearby poorly drained bogs because of the thermal 

effects of the water. Inasmuch as the best drained 

areas are generally underlain by gravels and have a 

temperature anomaly, aerial infrared mapping might 

show the best locations for constructing roads and 

buildings and indicate likely sources of gravel for 

construction purposes.

In the absence of various modifying conditions 

such as those described above, the top and bottom of 

the permafrost layer tend to parallel the ground 

surface, rising under hills and lowering beneath 

valleys (fig. 4).

A gradual climatic warming during the last century 

has caused a warming of the permafrost to depths of 

several hundred feet (Lachenbruch and Brewer, 1959; 

Lachenbruch and others, 1962, 1966). Hence near 

Barrow, Alaska, the temperatures at a depth of 150 

feet (about 9.7° C) are lower than those at 50 feet 

(about -9.4° C). Below 300 feet, however, the 

temperatures increase in accordance with the anticipated geothermal gradient (Lachenbruch and others, 

1962). Near the southern limit of permafrost the 

effect of the climatic warming is to keep the permafrost very close to 0° C throughout its entire depth. 

The permafrost is, therefore, very vulnerable to deep 

thawing and often will not regenerate when active 

construction procedures are used.

It should be pointed out that in a given area the 

mean ground-surface temperature is usually higher 

than the mean air temperature, largely because the 

ground is insulated by snow during the cold winter 

but is bare during the summer.

It is important also that the fluctuations of air 

temperature from summer to winter are normally 

substantially greater than corresponding fluctuations 

at the ground surface. Typically, ground-surface
PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

Shallow 

lake

Ocean Large deep 

lake

FIGURE 4. The effect of surface features on the distribution of permafrost in the continuous permafrost zone.

After Lachenbruch (1968, p. 837).

temperatures fluctuate 20° C to 50° C seasonally, the 

smaller values occurring in wetter terrains. The 

fluctuations diminish rapidly with depth, normally by 

a factor of 10 for approximately every 20 feet. Thus 

the seasonal variation of temperature at 20 feet is a 

few degrees, at 40 feet it is a few tenths of a degree, 

and at 60 feet it is barely detectable. Seasonal 

fluctuations normally propagate into the earth at the 

rate of about 5 feet per month. Because of this lag 

the minimum temperature at 30 feet occurs in midsummer. This explains the summer freezing of some 

water wells in the subarctic.

Curve A in figure 5 shows how the change in annual 

ground-surface temperature, assumed here to be 

sinusoidal, produces thawing of the permafrost even 

though the mean annual ground-surface temperature 

is well below 0° C. The stippled area indicates the 

amount of thawing that takes place. Note that if 

either the mean annual temperature or the amplitude 

of the temperature fluctuations is increased there will 

be a greater amount of thawing. If the permafrost 

is dry, that is, without interstitial ice or water, the 

temperatures will follow curve A. However, if water 

is present the latent heat released when water freezes 

will cause the temperature to remain at the freezing 

point while this heat is dissipated as shown by curve 

B. The latent heat absorbed in the spring and libcurve A

temperature

Ground-surf ace 

temperature

FIGURE 5. Relations of amplitude of ground-surface 

temperature fluctuations to amount of thawing.

erated in the fall by moisture in the arctic layer tends 

to reduce the temperature fluctuations at the permafrost table.

AREAL DISTRIBUTION AND THICKNESS

Two broad zones of permafrost can be differentiated 

in the northern hemisphere (fig. 1) the continuous 

zone which is underlain by permafrost nearly everywhere, and the discontinuous zone which includes 

numerous permafrost-free areas. Within the discontinuous zone the extent of the permafrost-free 

areas increases progressively from north to south. 

South of the discontinuous permafrost zone, permafrost generally is absent except for a few isolated
PERMAFROST

occurrences, usually at high altitudes. The distribution 

of permafrost is largely controlled by temperature 

variations related to differences in latitude, altitude, 

and major climatic patterns.

In Alaska (fig. 2), the two broad permafrost zones 

can be subdivided into: (1) mountainous areas where 

bedrock generally is at or near the surface, and (2) 

lowland areas commonly underlain by thick unconsolidated deposits. The thickness, distribution, and 

temperature of permafrost are extremely variable in 

the mountainous areas; in the lowland areas these 

characteristics are more uniform.

From north to south, the mountainous areas can be 

further subdivided into areas underlain by continuous 

permafrost, areas underlain by discontinuous permafrost, and areas underlain by isolated masses of permafrost.

The lowland portion can also be subdivided into (a) 

a northern area (largely north of the Brooks Range) 

which is underlain by thick permafrost; (b) a central 

area (between the Brooks and Alaska Ranges but 

including the Copper River basin), which is underlain 

by moderately thick to thin permafrost in areas of 

fine-grained deposits and by discontinuous or isolated 

masses of permafrost in areas of coarse-grained deposits; and (c) a southern area (including the Bristol 

Bay area and the eastern and western margin of the 

Susitna Lowland north of Anchorage), which is underlain by numerous isolated masses of permafrost in 

areas of fine-grained deposits, and which generally is 

free of permafrost in areas of coarse-grained deposits.

Because climate is the major factor that controls the 

regional (and global) distribution of permafrost, the 

permafrost regions in Alaska can be characterized by 

the mean annual air temperature and precipitation

data for representative stations (table 1). Within the 

continuous permafrost zone, Barrow has the lowest 

mean annual air temperature, 10° F, whereas Anchorage, just outside of the permafrost region, has a 

mean annual air temperature of 35° F.

TABLE 1. Mean annual temperature and precipitation data 

from representative stations in Alaska

Station

[Data from U.S. Weather Bureau records]

Mean annual temperature Mean annual precipitation 

(°F) (inches)

Continuous permafrost zone

Barrow ______________ 10

Umiat ______________ 10

Bettles

Discontinuous permafrost zone 

_________ 22

Fairbanks ____________ 26

Glennallen (Gulkana) __ __ 27

Bethel ______________ 30

No permafrost 

Anchorage ____________ 35

Valdez ______________ 36

Seward ______________ 40

Juneau__ ____________ 41

19

12

12

18

15

62

69

56

The climatic control is also reflected by the thickness of permafrost which ranges from more than 1,300 

feet near Barrow to lenses less than a foot thick in the 

southernmost part of the permafrost zone.

Even though the annual precipitation is low at the 

stations within the permafrost region, ground conditions generally are wet, especially in areas underlain 

by fine-grained sediments. This poor drainage is 

caused by the impervious permafrost layer, generally 

within a few feet of the surface, and by the low

FLOOD PLAIN

SEA LEVEL -

8000 FEhT EXPLANATION

HORIZONTAL SCALE

Inferred boundary Doubtful boundary

FIGURE 6. Distribution of permafrost in the discontinuous permafrost zone, Fairbanks area. Slightly modified after

Pewe (1954, p. 326).
PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

evaporation rate at the prevailing low temperatures. 

Also, the low annual precipitation indicates that the 

snow cover is not thick.

In any area where the mean annual air temperature 

is around 0° C (32° F), the microclimate, which is 

governed largely by local features, can be critical in 

determining whether or not permafrost is present. 

For example, the mean annual air temperature 

recorded at a site underlain by unvegetated dry soils 

can be 1° or 2° warmer than a nearby site underlain 

by vegetated wet soils. Slope exposure also controls 

microclimate in mountainous or hilly areas where 

south-facing slopes may receive considerably more 

solar heat than the north-facing slopes. This is 

important in the southern margin of the permafrost 

region where south-facing slopes often are completely 

free of permafrost, whereas nearby north-facing slopes 

are underlain by thick permafrost.

Permafrost thickness also varies depending upon 

the amount of heat flowing outward from the earth's 

interior. Generally, the temperature of the earth 

increases 1° C (1.8° F) for each 100 to 200 feet of depth; 

however, locally, the near-surface temperatures can 

be relatively high.

In the discontinuous zone where the permafrost 

layer is thinner, surface features affect the distribution of permafrost in much the same way as in the 

continuous zone (fig. 4); thus lakes and rivers cause 

smaller anomalies because their temperature does not 

contrast as much with the surroundings. The distribution of permafrost in the Fairbanks area, as shown 

in figure 6, is typical of much of interior Alaska. 

Permafrost is absent under the south-facing hillslope, 

continuous under the flood plain, and absent under 

the Chena River.

RELATED GEOMORPHIC FEATURES

Permafrost and frost action produce several types 

of geomorphic features (Washburn, 1956; National 

Academy of Sciences, National Research Council, 

1966). Among these features are polygonal ground 

(ice wedges), stone nets, garlands and stripes, solifluction sheets and lobes, thaw lakes and thaw pits, 

beaded drainage, and pingos. Because these features 

are closely related to the permafrost problems a brief 

description of each is warranted.

POLYGONAL GROUND

Polygonal ground (figs. 7 and 8), which covers many 

thousands of square miles of northern Alaska is caused 

by shallow troughs which overlie a honeycomblike 

network of vertical wedge-shaped ice masses (ice 

wedges) that have joined to form polygons in the

FIGURE 7. Aerial view of coastal plain near Barrow, in northern Alaska showing polygonal markings on ground surface 

caused by underlying ice-wedge polygons. The bank along 

Elson Lagoon in foreground is being undercut by thawing of 

permafrost and by wave action. Photograph taken in August 

1958.

permafrost. Individual polygons range from 30 to a 

few hundred feet in diameter. Figure 9 shows a 

typical ice wedge. Where the surface of the ground 

is disturbed and the thermal regime upset, the ice 

wedges can melt, causing severe differential settlement of the ground surface. For example, clearing 

of the ground near Fairbanks caused ice wedges to 

melt, and large mounds were left (figs. 10 and 11.)

Polygonal ground indicates relatively fine grained 

unconsolidated sediments with the permafrost table 

near the ground surface. It also occurs in coarser 

sediments and gravels where the formation of ice 

wedges is less extensive than in the fine-grained 

sediments.

Many different hypotheses for the origin of icewedge polygons have been proposed; however, the 

thermal contraction theory first clearly described by 

Leffingwell (1915, 1919) has been generally accepted 

by most workers. A quantitative appraisal of the 

mechanics of the thermal contraction theory was 

made by Lachenbruch (1962), and he concluded that 

the theory is compatible with the thermal and mechanical properties and thermal regime of the permafrost in which the ice-wedge polygons occur.

STONE NETS

Stone nets, garlands, and stripes are extensive in 

the arctic. Frost heaving in granular soils produces 

netlike concentrations of the coarser rocks (fig. 12). 

If the area is gently sloped, the net is distorted into 

garlands by downslope movement. If the slope is
FIGURE 8. Polygonal markings on ground surface (caused by ice-wedge polygons) in the vicinity of Meade River, about 35 

miles southeast of Barrow, in northern Alaska. Photograph by U.S. Navy, July 1949.

steep, the coarse rocks lie in stripes that point downhill. Generally, in garlands and stone stripes the 

downslope flow pattern is readily apparent. Stone 

nets, garlands, and stripes indicate strong frost action 

in moderately well drained granular sediments that 

vary from silty fine gravel to boulders. These surficial materials are commonly susceptible to flowage.

SOLIFLUCTION

Solifluction sheets and lobes are masses of unconsolidated sediment that range from less than a foot 

to hundreds of feet in width. These features are 

extensive in the arctic and may cover entire valley

walls. They occur on slopes as low as 3°. Solifluction 

plays a major role in the formation of patterned 

ground. This type of patterned ground is formed by 

the gradual downslope (gravity) movement of watersaturated sediments. The surficial materials are 

especially mobile in the permafrost region because the 

active layer commonly is supersaturated with moisture. 

This condition is caused by the impermeability of the 

underlying permafrost and by the low evaporation 

rate. Downslope movements of Solifluction features 

are so rapid that a structure resting upon one will 

either be subjected to large earth pressures or will 

move passively downslope.
10 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

FIGURE 9. Ice wedge (ground ice) in permafrost exposed by placer mining near Livengood about 50 miles northwest of

Fairbanks. Photograph by T. L. Pewe, September 1949.
RELATED GEOMORPHIC FEATURES 11

FIGURE 10. Thermokarst mounds near Fairbanks. Mounds 

range from 10 to 30 feet in diameter. See figure 11 for ground 

view of mounds and explanation. Photograph by R. F. Black 

and T. L. Pewe, September 1948.

FIGURE 11. Thermokarst mounds near Fairbanks caused by 

melting of ice wedges. The resulting ground settlement 

formed deep trenches in polygonal patterns and left mounds 

in the intervening areas. The thawing was started after the 

area was cleared for agricultural purposes. Figure 10 is an 

aerial view of similar mounds. Photograph taken in June 1955.

FIGURE 12. Sorted stone circles caused by frost action, in Alaska 

Range, south-central Alaska. Photograph by T. L. Pewe, 

June 1968.
12 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

THAW OR THERMOKARST PITS

Thaw or thermokarst pits occur in areas underlain 

by permafrost containing large masses of ground ice 

(fig. 13). If the ground surface is disturbed above a 

large ice mass, such as the one shown in figure 13, the 

resultant change in the thermal regime can cause the 

ice mass to thaw; this thawing causes a thaw pit to 

form (fig. 14).

The occurrence of these pits indicates poorly drained, 

fine-grained sediments with the permafrost table near 

the surface.

THAW LAKES

Hopkins (1949, p. 119) defines a thaw lake as one 

which occupies a thaw depression; however, the 

definition includes lakes that originated in other ways 

but that have been enlarged considerably by the 

thawing and caving of their margins. The term 

"cave-in-lake," (Muller, 1943, p. 214) is used somewhat 

synonymously with "thaw lake," but the original 

definition limits its usage to lakes formed in caved-in 

depressions caused by thawing of ground ice.

Thaw lakes are common throughout the permafrost 

region and usually indicate poorly drained, finegrained, unconsolidated sediments with the permafrost table near the surface. These lakes are 

characterized by undercutting and caving along their 

margins, caused by the thawing permafrost (fig. 15). 

Trees along the shorelines that lean toward the lake 

because their root systems are being undercut are 

conspicuous indicators of thaw lakes.

Oriented lakes, a very common type of thaw lake 

in northern Alaska, cover more than 25,000 square 

miles of the arctic coastal plain (Black and Barksdale, 

1949, p. 105). They range in size from small ponds to 

more than 9 miles long and 3 miles wide. The long 

axis of these lakes is oriented in a northwesterly 

direction (ranging from 10° to 15° west of true north). 

This preferred orientation is strikingly shown on the 

topographic maps of northern Alaska.

BEADED DRAINAGE

Beaded drainage occurs in areas underlain by 

systems of ice wedges. The heat in the flowing surface water thaws the underlying ice masses (usually 

at ice-wedge intersections) forming depressions 

occupied by pools of water connected by the normally 

flowing stream. The overall appearance, when viewed 

from the air, is like a string of beads, hence the name 

"beaded drainage." Beaded drainage is a surface 

indicator of the presence of permafrost.

PINGOS

Small ice-cored conical hills called pingos are common 

in the continuous permafrost zone along the coastal

plain of northern Alaska and northwestern Canada 

(Mackay, 1966, p. 71) and in the discontinuous permafrost zone in central Alaska (Holmes and others, 

1968). Figure 16 shows a pingo of the type found in 

the forested central part of Alaska. Pingos range 

from 50 to several thousand feet in diameter, and 

from 10 to several hundred feet in height. Commonly, 

they have craters on their summits, which are occupied 

by ponds.

Pingos indicate silty sediments and the presence of 

ground water (with some hydraulic head) that is confined between the seasonal frost and permafrost 

table or is flowing in a thawed zone within the permafrost. Those in former lakebeds indicate saturated 

fine-grained sediments.

MUCK DEPOSITS

Although not actually a geomorphic feature, perennially frozen "muck" or organic-rich silt deposits are 

widespread throughout interior Alaska (figs. 7 and 16) 

and are important in permafrost areas. In the Fairbanks area, the muck deposits are composed of 

organic-rich windblown silt (loess) that has been redeposited (Pewe, 1966, p. 14). The tremendous amount 

of organic material in the deposits presumably was 

incorporated when the windblown silt was being 

transported from the hillsides to the valley bottoms 

by solifluction, sheet wash, and other gravity-type 

processes. Muck deposits can be thawed in a few 

months or years when the insulating quality of the 

surface is modified. This material liquifies when 

thawed and can create severe engineering problems.

FIGURE 13. Large mass of ground ice exposed by gold placer 

mining in silt bluff near Fairbanks. Thawing of a large ice 

mass causes severe differential settlement of the surface of 

the ground, as is shown in figure 14. Photograph taken in June 

1955.
RELATED GEOMORPHIC FEATURES 13

FIGURE 14. Thaw or thermokarst pit near Fairbanks formed 

by the thawing of a large ice mass that caused severe differential settlement of the surface of the ground. Photograph 

by T. L. Pewe, June 1948.

FIGURE 15. Shoreline of a thaw lake about 40 miles northwest 

of Glennallen in south-central Alaska. Shoreline undercut 

because of thawing of permafrost. Vegetation mat of peat 

is draped over surface of steep bank (8-12 ft high) and is 

caving into lake. Trees in foreground are leaning toward 

lake, and they too will cave into the lake as the undercutting 

progresses landward. Photograph taken in June 1960.

FIGURE 16. Pingo in Yukon-Tanana Upland, east-central 

Alaska. Light birch trees on pingo contrast with dark spruce 

trees surrounding it. Pingo is about 300 feet in diameter and 

50 feet high; water-filled crater on its summit makes it 

"donut shaped." Photograph by H. L. Foster, August 1960.
14 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

SUMMARY OF GEOMORPHIC FEATURES

Table 2 has been prepared as a quick reference to 

the descriptions and ground conditions associated 

with these common topographic features in permafrost 

areas.

ENGINEERING GEOLOGY

Construction and maintenance of structures in the 

arctic and subarctic regions underlain by permafrost 

are characterized by a wide range of problems in 

addition to those experienced elsewhere. Engineers, 

designers, and construction and maintenance personnel 

are continuously plagued by extremely severe frost 

heaving, subsidence caused by thawing permafrost, 

soil creep or solifluction, landslides, and icings. These 

processes not only present construction and maintenance problems but in the more severe cases may be 

a hazard to the users of the structures.

There are two basic methods of constructing on 

permafrost: (1) the active method and (2) the passive 

method.

The active method is used in areas where permafrost 

is thin and generally discontinuous or where it contains

a relatively small amount of ice. The object of this 

method is to thaw the permafrost, and if the thawed 

material has a satisfactory bearing strength, then 

construct in a normal manner. Sometimes the structure itself can be used to thaw the permafrost, and 

the surface brought back to grade at intervals while 

the thawing process takes place. Generally, the 

thawing of the permafrost is accomplished simply by 

clearing the vegetation, which normally insulates the 

permafrost from the heat in the air and from solar 

radiation. Heat from steam and warm water piped 

into the ground has also been used to thaw permafrost. Naturally, the active method of construction 

has limited application, because of the great thickness of permafrost throughout most of the region, 

and because of the time required for thawing the 

ground.

The passive method, which has broad application 

throughout most of the permafrost region, is used in 

areas such as the North Slope, where it is impractical 

to thaw the permafrost. The object of this method 

is to minimize disturbance of the permafrost and of 

the thermal regime. The thermal regime in an area

TABLE 2. Common topographic features that indicate ground conditions in arctic and near arctic regions

Feature and description

Polygonal ground (ice wedges) Usually indicates the presence 

of a network of ice wedges vertical wedge-shaped ice masses 

that form by the accumulation of snow, hoarfrost, and meltwater in ground cracks that form owing to contraction 

during the winter. Wedge networks are also common in wet 

tundra where no surface expression occurs. (Subject to extreme differential settlement when surface disturbed)

Stone nets, garlands, and stripes Frost heaving in granular 

soils produces netlike concentrations of the coarser rocks 

present. If the area is gently sloped, the net is distorted 

into garlands by downslope movement. If the slope is steep, 

the coarse rocks lie in stripes that point down hill.

Solifluction sheets and lobes Sheets or lobe-shaped masses of 

unconsolidated sediment that range from less than a foot to 

hundreds of feet in width that may cover entire valley walls; 

found on slopes that vary from steep to less than 3°.

Thaw lakes and thaw pits Surface depressions form when local 

melting of permafrost decreases the volume of ice-rich sediments. Water accumulates in the depressions and may 

accelerate melting of the permafrost. Often form impassible 

bogs.

Beaded drainage Short, often straight minor streams that 

join pools or small lakes. Streams follow the tops of melted 

ice wedges, and pools develop where melting of permafrost 

has been more extensive.

Pingos Small ice-cored circular or elliptical hills that occur in 

tundra and forested parts of the continuous and discontinuous 

permafrost areas. They often lie at the juncture of southand southeast-facing slopes and valley floors, and in former 

lakebeds.

Associated ground conditions

Typically indicates relatively fine grained unconsolidated sediments with permafrost table near the ground surface; also 

known from coarser sediments and gravels where wedge ice 

is less extensive.

Indicate strong frost action in moderate well-drained granular 

sediments that vary from silty fine gravel to boulders. Surficial material commonly susceptible to flowage.

Indicate an unstable mantle of poorly drained, often saturated 

sediment that is moving downslope largely by seasonal frost 

heaving. On steeper slopes they often indicate bedrock near 

the surface, and on gentle slopes, a shallow permafrost table.

Usually indicate poorly drained, fine-grained unconsolidated 

sediments (fine sand to clay) with permafrost table near the 

surface.

Indicate a permafrost area with silt-rich sediments or peat 

overlying buried ice wedges.

Indicate silty sediments derived from the slope or valley, and 

ground water with some hydraulic head that is confined between the seasonal frost and permafrost table or is flowing 

in a thawed zone within the permafrost. Those in former 

lakebeds indicate saturated fine-grained sediments.
ENGINEERING GEOLOGY 15

in a natural undisturbed state is normally in quasiequilibrium with all the environmental factors, but 

in many areas this state of equilibrium is very sensitive. The simple passage of a tracked vehicle that 

destroys the vegetation mat is enough to upset the 

delicate balance and to cause the top of the permafrost layer to thaw. This thawing can cause differential settlement of the surface of the ground, drainage 

problems, and severe frost action. Once the equilibrium 

is upset, the whole process can feed on itself and be 

practically impossible to reverse. However, if a 

structure is founded on permafrost that remains 

frozen, the frozen ground provides rocklike bearing 

strength. In special cases it may be practical to keep 

the permafrost intact by using a refrigeration system. 

Engineering problems in permafrost nearly always 

are associated with the active layer (the layer that 

freezes and thaws annually) and the active layerpermafrost interface (permafrost table). Changes in 

the surface environment, either natural or man made, 

produce thermal changes in this zone that can have 

serious effects upon engineering works and structures.

ENGINEERING PROBLEMS

The engineering problems associated with permafrost are not similar in every type of rock or sediment. 

For example, bedrock that contains ice in its fractures 

will present few, if any, construction or maintenance 

problems. Well-drained coarse-grained sediments 

such as glacial outwash gravel, although below 0° C, 

may not contain any ice. Here again few, if any, 

construction problems will arise. If water is saline, 

it will remain in the liquid state even if its temperature is below 0° C. The problems associated with 

this condition are different from those associated 

with permafrost containing moisture in the frozen 

state.

Major engineering problems arise where permafrost 

occurs in poorly drained fine-grained sediments. In 

such sediments there are generally large amounts of 

ice, and when the thermal regime is disrupted the 

ice begins to melt. The thawing produces excessive 

wetting and undesired plasticity of the fine-grained 

sediments and renders them unstable. This instability 

can result in settling, caving, and subsidence of the 

ground surface, and in many cases, in flowage of the 

sediments either laterally or downslope.

During the winter months the active layer freezes 

downward from the ground surface to the permafrost table. In the fine-grained material, formation 

of this ice results in frost heaving.

Thawing of permafrost and the heaving and subsidence caused by frost action are responsible for the

major engineering problems in the subarctic and 

arctic regions. The following discussion on the thawing of permafrost, the freezing of the active layer, 

and frost action on ground surface and on piles is 

presented to prevent repetition of engineering problems. Many of the problems are common to most, if 

not all, of the structures discussed.

Thawing of Permafrost

In the past it was engineering practice to remove 

the protective vegetation cover during construction; 

thus some of the insulating effect was lost. As soon 

as the delicate thermal equilibrium is disrupted, 

permafrost starts to thaw. The result of this thawing is to lower the permafrost table underneath the 

fill and to make the active layer thicker. The thicker 

active layer collects larger quantities of moisture, 

and consequently during the winter greater heaving 

of the ground surface occurs when the moisture 

freezes. On the other hand, during the summer, the 

active layer thaws and the sediments lose their 

strength causing subsidence, flowage of sediments, 

and landslides if the structure is on a slope.

With few exceptions, structures in the arctic require 

some sort of pad or fill. The nature and thickness of 

the fill particularly the thickness are the controlling 

factors. Figure 17 shows the effects of the pad or fill 

upon the temperature fluctuations, depth to the 

permafrost table, and thickness of the active layer. 

The result of too little fill is shown in figure 17A In 

this example the insulating effects of the fill plus the 

compacted active layer is less than the insulating 

effect before construction. The result is thawing 

permafrost and an increase in the thickness of the 

active layer.

Figure YIB shows what will happen if the insulating effects of the fill and the compacted layer is 

greater than the original active layer. In this case, 

the permafrost table is raised because the amplitude 

of the seasonal temperature variation is smaller.

The procedures for calculating the appropriate 

thickness of gravel fill for various climates and 

materials are explained in detail by Lachenbruch 

(1959). When the calculated thickness of fill becomes 

so great as to be impractical, alternative procedures 

are necessary, such as using insulating materials 

under the fill.

Although the ice in the sediments is responsible for 

the heaving, it does give the sediments strength 

during the winter. However, when the ice melts 

during the summer, this strength no longer exists and 

the results may be damaging. If a structure is constructed during the winter, the ice-rich sediments will
16 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

0 Q

0 ° ° o " Gravel fill

o ^ v - Q

o o o

0 0 O

0 a a O - 0

Original ground/§urface ° 0_o ° c 0 a _u o o

~ " "~o o 5

Compacted active layer

 Post fill 

permafrost 

X table

 v.' permafrost '. .:' : '.;'. ; .' '

Thawed permafrost v :/.:.;.-.^.' ;';.; :."-y.: :/.:.

.A. Effect on permafrost table if insulating of fill plus compacted active layer is less than the insulating effects of 

original active layer.

 :'-':^^'-^:.^-:^SV^^-:\-:^^::H-'::^\: :^

B. Effect on permafrost table if insulating effect of fill and active layer is greater than the insulating effect of the 

original active layer.

Mean 

annual 

temperature

Summer TIME Winter 

C. Effects of cases A and B on amplitude of seasonal temperature variation at original permafrost table.

FIGURE 17. Diagram showing effect of gravel fill upon thermal regime.
ENGINEERING GEOLOGY 17

not fail, but when the ice thaws, the structure will be 

damaged by subsidence or by flowage of sediments 

from beneath the structure. Highways become impassable during the summer, whereas during the 

winter they are considered to be relatively highspeed roads.

Frost Heaving

Frost heaving has long been known as a major 

destructive factor to structures. Although the frostheaving mechanism is complex, the major factors 

controlling it are ground-surface temperatures, surface condition of the soil, and characteristics of the 

soil. Soil properties include structure, permeability, 

thermal properties, physical and chemical properties, 

and moisture content. Of these factors, the most 

important are the moisture content and texture of 

the sediments.

The nature of the ice in the active layer, as well 

as the thickness of the layer, has an important effect 

on the amount of frost heaving. In relatively coarse 

grained sediment with a low water content the ice 

acts as a binder and does not produce much heaving. 

If coarse sand is interbedded with silt and the water 

content is not high, ice forms as layers in the silt and 

as a binder in the coarse sand. In this case, thin ice 

lenses are formed and moderate heaving results. If 

the sediments are silt and fine sand and the water 

content is high, large masses of segregated ice will 

form and maximum frost heaving will occur.

Frost heaving is a major problem in the arctic and 

subarctic primarily because most of the low-lying 

areas are covered by fine-grained surface materials 

which are poorly drained.

Frost Heaving of Piles

The use of piles for support of structures is as common in the arctic region as it is in the lower latitudes. 

The problems, however, are quite different. In the 

warmer climates, the chief problem with the use of 

piles is to obtain sufficient bearing strength. In arctic 

regions, the chief problem is to keep the piles in the 

ground. Frost action heaves them up, and any structure placed upon the piles is also displaced upward, 

usually differentially.

The force that tends to displace the piles upward is 

generated in the freezing active layer and is a function of the adfreezing strength between the pile and 

the active layer, the depth to which the pile has been 

driven in the active layer, and the perimeter of the 

pile. The forces acting downward are the load upon 

the pile, the weight of the pile, and the forces produced in the unfrozen active layer and in the permafrost. The force in the unfrozen active zone is the

skin-friction bond between the pile and unfrozen 

ground over the lateral surface of the pile. The force 

in permafrost is equal to the tangential adfreezing 

strength between the pile and the frozen ground 

distributed over the pile length and the lateral surface of the pile.

The upward-acting forces become greater as the 

active layer freezes, therefore the thicker the active 

layer the greater the upward forces. The downwardacting forces in permafrost depend on how deeply the 

piles penetrate it. If the thermal regime is disrupted 

and the permafrost starts to thaw, the downward 

force of the permafrost becomes less and the upward 

force of the active layer becomes greater. Conversely 

if the permafrost table rises from its original position, 

the downward force of permafrost becomes greater 

after an initial upthrusting.

Pewe and Paige (1963, p. 364) give a hypothetical 

example of seasonal frost penetration (freezing of 

active layer) into silt and show the possible upward 

forces on a 40-inch-perimeter pile. Their data are reproduced in this report as table 3. Note that the upward force becomes greater as the frozen layer 

becomes thicker at a rate of about 21,600 pounds per 

foot. It should be stated that Pewe and Paige had 

to make the assumption that the texture of the silt 

and the water content was the same throughout the 

4V2-foot zone. These two factors definitely influence 

the bond between the frozen active layer and the 

pile, and therefore the tangential adfreezing strength. 

The general discussion of thawing permafrost, the 

freezing active layers, and frost heaving of piles given 

above applies to all the descriptions of individual 

structures that follow. The problems are common to 

all structures in the arctic.

TABLE 3. Hypothetical exa mple of seasonal frost penetration into 

silt in central Alaska and possible upward push on 40-inchperimeter pile (ground temperature constant)

Date

November 1 

December 1 

January 1 _ _ 

February 1 _. 

March 1 __ _ . April 1__ __

[After Pewe and Paige, 1963, p. 364]

Depth of frost

penetration

(feet)

1

2

3

4

4V2

Maximum force

pushing upward

(pounds)

21,600

32,400

43,200

64,800

86,400

97,200

SPECIFIC STRUCTURES

The problems associated with permafrost and frost 

action affect structures in numerous ways. Therefore, a brief description of the engineering problems 

associated with these effects is presented in the following pages.
18 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

Railroads

Railroad engineers prefer to keep grades under 2 

percent (2 ft of vertical for every 100 ft of horizontal 

distance). Unfortunately this requires th^ the roadbed be placed in low-lying terrain which is usually 

underlain by poorly drained fine-grained sediments 

containing permafrost. Therefore, construction 

problems arise, and expensive maintenance problems 

develop.

The Alaska Railroad, which runs from Seward (mile 

0) to Fairbanks at mile 470.3 (fig. 18), was started 

about 1910 by a private company, The Alaska Central, 

and was completed in 1923 by The Engineering Commission.

Railroad personnel encountered many construction 

problems because of thawing permafrost. A minimum 

of fill and ballast was placed on the right-of-way, 

causing areas underlain by ice-rich permafrost to 

chaw. When the thawing occurred the fine-grained 

sediments lost their strength and the sediments either 

subsided or flowed from underneath the roadway.

The roadway of The Alaska Railroad is underlain 

locally by ice-rich permafrost where sediments are 

fine grained and poorly drained between Broad Pass 

(mile 304.5) and Dunbar (mile 431.6) and almost continuously from Dunbar to Fairbanks, where the railroad follows the valtey of Goldstream. The maintenance from Dunbar to Happy (mile 463.0) amounts to 

about $200,000 per year (T. C. Fugelstad, The Alaska 

Railroad, personal commun.) because of the need to 

install shims beneath the rails and replace ties damaged by frost heaving during the winter. Locally, 

slower than usual train speeds (slow-orders) are in 

effect during the winter with a consequent loss to 

The Alaska Railroad.

When winter has passed and summer arrives, The 

Alaska Railroad has other permafrost problems. In 

summer the active layer and eventually the underlying permafrost starts to thaw. When this happens 

the track subsides, usually differentially (fig. 19).

If the subsidence is not corrected yearly and the 

track not brought to grade, the track would look like 

the roadbed shown in figure 20. The railroad which 

ran from McCarthy to Cordova (fig. 18) was constructed in 1911 to carry copper ore to the port of 

Cordova. The railroad was abandoned in 1938, and 

much of its roadbed is now being incorporated into 

the Copper River Highway.

During the summer The Alaska Railroad places 

great quantities of gravel in the sink holes caused by 

thawing permafrost in order to maintain grade. Line

changes and ditching are also required in order to 

control permafrost problems. About $177,500 is spent 

annually to correct the effect of the thawing.

At Moody, a point on The Alaska Railroad where it 

follows the Nenana Canyon through the Alaska 

Range toward McKinley Park, the roadbed is underlain by fine silt and clay that was deposited in an 

ancient glacial lake. The temperature of permafrost 

here is close to 0 C, and when the railroad was constructed the thermal equilibrium was disrupted and 

the permafrost started to thaw. Over the years this 

thawing has required numerous line changes and 

remedial measures. Figure 21 shows some of the landslides that have occurred. Figure 22 is a photograph 

of the landslide area near mile 353.5. Piles were 

driven immediately downslope from the rails in order 

to prevent the tracks from sliding into the canyon. The 

pebbles, cobbles, and boulders shown in the photograph are from the gravel which overlies the lake 

silts and clays. Vertical displacements at the Moody 

slide have been as much as 4 feet in one day. During 

the period when landsliding is expected, the track is 

patrolled in advance of all trains. Remedial measures 

to combat the landsliding vary from year to year. 

During the summer of 1967, over $400,000 was spent 

to realine the track and bring it to grade.

Many bridges on The Alaska Railroad are also 

affected annually by frost heaving and require 

maintenance. Time does not permit a discussion of 

all the structures, and therefore only two bridges are 

described one supported by piles and the other by a 

concrete pier.

The bridge at mile 458.4, in Goldstream valley, is 71 

feet long and supported by six bents of wooden piles. 

Pewe and Paige (1963, p. 380-383) present a detailed 

description of this structure. A summary of their 

description of the bridge and its history follows.

The bridge, which was constructed in 1917, is underlain by perennially frozen silt. The permafrost table 

on September 20,1954, was 11 or 12 feet below the 

ground surface at the ends of the bridge and 13 feet 

deep under the creek.

This wooden-pile bridge has had a continual history 

of frost heaving and was affected more than any 

other wood-pile bridge on The Alaska Railroad. The 

earliest record of pile history was in 1923 at which 

time all the piles were replaced. The new piles were 

sunk to depths ranging from 12 to 23 feet, the greatest penetration being at the end bents. During the 

winter of 1952-53, Pewe and Paige report that the 

center of the bridge was heaved 14 inches a dis-
172 C

ENGINEERING GEOLOGY

164° 156°

19

140°

OF ALA SKA

500 MILES

I

EXPLANATION

Abandoned railroad 

Winter road

Highway 

Abandoned highway 

FIGURE 18. Location of transportation routes in Alaska.

Existing route of The Alaska Railroad, 

showing station house

Proposed route of The Alaska Railroad, 

showing mile posts. Alternate routes 

are indicated by numbers
20 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

FIGURE 19. Differential subsidence caused by thawing permafrost along the Murphy Dome Spur of the Alaska Railroad. 

Roadbed is in Goldstream valley and is underlain by silt. Photograph by T. L. Pewe, June 1954.

placement great enough to decouple railroad cars. 

The Alaska Railroad cut off the top of the piles and 

brought the rails back to grade a common practice 

in this area.

Frost heaving continued in the winter of 1953-54, 

and by February 1954 the bridge had heaved 9 inches. 

In the latter part of February the piles were again 

replaced, most of the piles being sunk deeply in 

permafrost. Frost heaving was not evident during 

the winter of 1954-55. However, during the winter 

of 1955-56, frost heaving again occurred and by 

February 3,1956, the bridge had been heaved 3 inches 

at bent III, and by the end of the winter it had risen 

to 5 inches. Pewe and Paige's record stops in 1956. 

However, Bruce E. Cannon of The Alaska Railroad 

stated that heaving of the bridge is of only minor 

consequence at this time (personal commun., 1969).

The explanation for this sequence of events is as 

follows: The piles were driven into steam-thawed 

holes and emplaced deep in the thawed permafrost. 

The permafrost then started to refreeze and must 

have completely refrozen during the winter of 1955-

56. The first winter after the piles were placed 

(1954-55) the only forces heaving the piles upward 

were those of the active zone. Apparently these 

forces were not very strong. The second winter 

(1955-56), when as much as 5 inches of heaving occurred, the permafrost must have contained more 

moisture than when the piles were placed. When this 

additional moisture froze, it expanded and added to 

the upward force of the active layer. This upward 

force acted only in the winter of 1955-56, because by 

the end of that winter the permafrost had refrozen to 

its original position.

The railroad bridge spanning Riley Creek at mile 

347.4 near McKinley Park is a 570-foot steel-viaduct 

structure supported by concrete piers and concrete 

abutments. At the request of The Alaska Railroad 

the bridge site was examined by Reuben Kachadoorian 

in 1957 to determine the cause of differential heaving 

of the bridge. In some places the heaving was as 

much as 5 inches. The piers rest upon sandy stream 

gravels, which generally are not susceptible to very 

severe frost action. However, the permafrost table
ENGINEERING GEOLOGY 21

beneath the bridge was irregular and varied from a 

position lower than the pier bottoms beneath the piers 

to positions higher than the pier bottoms between the 

piers. This position varied because the concrete in 

the piers had a much higher thermal conductivity 

than the snow or water which surrounded the pier 

during the winter. Therefore, heat was drawn off 

from the ground by the piers and ice formed beneath 

the piers. As the ice grew, additional water was 

drawn from the unfrozen area around and beneath 

the piers until a sufficient amount of ice formed to 

heave the piers. After this explanation was given, 

The Alaska Railroad took remedial measures, and the 

effect of frost action upon the Riley Creek bridge was 

minimized.

Highways and Roads

There are over 2,000 miles of primary and secondary 

roads in Alaska; the majority are subjected to frost 

action and are underlain by permafrost. The recent 

discovery of petroleum north of the Brooks Range at 

Prudhoe Bay will no doubt stimulate a great deal of 

highway construction in the area, and all highways

will be underlain by permafrost and subject to 

heaving from frost action. If constructed improperly, 

the roads will require costly maintenance or even 

abandonment.

A highway constructed during the winter months 

may lead the builder into false security. If, for example, the vegetation cover were removed and the 

roadbed smoothed with heavy equipment, winter use of 

the highway would not generate any problems of thawing, and any frost heaving of the roadway would be 

minor.

Bogs, swamps, or other such areas are perfectly 

capable of supporting traffic during the winter 

months when they are frozen to a depth of 2 feet or 

more. Since they are level, they actually invite 

construction.

In order not to disrupt the thermal equilibrium in 

permafrost areas, more fill is necessary in the roadbed. The amount of this extra fill is variable under 

different geological conditions, but it is always a 

major cost factor. For example, highway contsruction costs in areas underlain by permafrost are substantially higher than in areas free of permafrost.

FIGURE 20. Differential subsidence of roadbed of Copper River and Northwestern Railway near Strelna, 75 miles northeast 

of Valdez. The thermal equilibrium of the fine-grained sediments underlying the roadbed was disrupted during construction and the permafrost started to thaw. Maintenance and use of the railroad was discontinued in 1938. Subsidence as 

well as lateral displacement, however, has continued. Photograph by L. A. Yehle, September 1960.
22 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

EXPLANATION

New drainage structure 

CMP=Corrugated metal pipe

APPROXIMATE SCALE

FIGURE 21. Map of the Moody area on The Alaska Railroad showing landslides and slumps caused by thawing of permafrost 

and remedial measures taken to combat them. Map prepared by The Alaska Railroad, 1967.

Mr. R. D. Shumway, Alaska Department of Highways, 

supplied the authors with an analysis of costs of the 

highway between Rex and Lignite in central Alaska 

north of the Alaska Range. His results are shown 

in table 4. One can see that the cost of borrow 

material in permafrost areas was about 1% times as 

much as in permafrost-free areas; the costs of general excavation and of pit stripping were about twice 

as much.

TABLE 4. Comparison of construction costs, per cubic yard, between permafrost and permafrost-free areas of the highway 

between Rex and Lignite, Alaska

Borrow material ___________ $0.509 $0.749

General excavation _________ .464 .967

Pit stripping _____________ .164 .370

Many of the highways in Alaska were originally 

pioneer or "tote" roads constructed chiefly by removing the vegetation and adding fill. Figure 23 

shows the character of the ground surface in July 

immediately after the removal of the insulating 

vegetation. The permafrost was exposed in the hope 

that the sun would thaw it sufficiently by late 

summer so that fill could be placed upon the thawed 

sediments. By September the ice in and around the 

polygons had thawed to a depth of at least 4 feet; 

this thawing resulted in differential subsidence of the 

ground surface. In addition, the silt had lost all its 

bearing strength and was nothing more than a 

quagmire; consequently, the site was abandoned and 

the location of the road was moved.

The thermal disturbances created by a roadway 

have been studied in detail along the Richardson, 

Glenn, and Tok Highways near Glennallen, Alaska 

(Greene and others, 1960). Here the permafrost is 

relatively thin (50-150 ft thick) and mean annual 

temperatures below the undisturbed ground surface 

are rarely lower than 2° C. Thus conditions favor 

extensive thawing when the surface is disturbed. It
ENGINEERING GEOLOGY 23

was found that beneath the roadway the amplitude 

of seasonal temperature fluctuations was two to three 

times that found in the nearby undisturbed ground. 

Furthermore, the ground beneath the roadway was 

more sensitive to random climatic variations from 

year to year. A change of only 4° C in the mean 

annual air temperature over a 2-year period caused a 

2.5° C change in the mean annual temperature at 

depths of 5 to 10 feet beneath the roadway and a 

change of less than 1° C at similar depths in undisturbed ground nearby. The increased amplitude of 

seasonal temperature variations together with the 

greater sensitivity to an increase in the mean surface 

temperature caused a trough of thawed ground to 

form beneath the roadway. Water from thawed 

permafrost drained along the trough until it was 

trapped in a basin or escaped by exterior drainage. 

Settling of the roadway followed. Heaving resulted 

where the melt water was trapped and later refrozen. 

In subsequent years freezing and thawing of the 

active layer was accelerated where the melt water

** ._ *2 '**- '" " r'"i% ,1^., ^M&-.*,i*i.>**t£^

had drained away because of the absence of latent 

heat. Therefore, thawing in colder years reached 

depths previously attained only in warm years.

During the summer of 1954, the Alaska Road Commission (now Alaska Department of Highways) exposed permafrost in lake silts 2 miles north of Paxson. 

The ice-rich lake sediments started to thaw and 

actually flowed (fig. 24).

In many places the thickness of the fill used by the 

road crews is insufficient to prevent the thawing of 

the permafrost under the roadbed. An excellent example of one such place is shown in figure 25. The 

photograph shows the remains of a road from the 

Umiat Airstrip to several drilling sites in the area; it 

was constructed about 1950 and abandoned around 

1953. The road is underlain by fine-grained sediments 

containing ice-wedge polygons. The breaks across 

the roadway are due to the melting of the ice wedges. 

Such conditions will occur again if the potential 

effects of thawing permafrost are not considered 

during highway planning and construction.

FIGURE 22. Landslide area at mile 353.5, The Alaska Railroad. Note the tops of piles immediately downslope from he rails

to prevent displacement of the tracks.
24 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

FIGURE 23. Initial location of part of the Denali Highway near the Susitna River, interior Alaska. Construction crew is removing the insulating vegetation to expose polygonal ground in permafrost. Sediments are windblown sand and silt 

overlying silty glacial till. The dark areas outlining the polygons overlie ice wedges as much as 12 inches wide. Photograph taken in July 1953.

The location of a highway on a slope underlain by 

unconsolidated materials always presents problems. 

One must bear in mind that the highway is in a delistate of equilibrium, and that any change, not necessarily to the highway itself, may generate a slump or 

landslide in the structure.

Nichols and Yehle (1961, p. 25) describe such a slump 

and slide in the Richardson Highway roadbed at 

Simpson Hill near mile 113. This particular section 

of the highway crosses a small gully in a long sidehill 

cut. A thick fill was used to cross the gully. In the 

spring of 1954, a new telephone line upslope from, and 

parallel to, the road was constructed. During the 

construction, a wide swath of the insulating vegetation cover was stripped off. Rapid thawing of the 

permafrost during the summer resulted, releasing 

moisture to saturate the fill downslope. This increased 

moisture caused some small slumps in the fill. Early

in September 1954, in order to bring the road back to 

grade, fill material was obtained from upslope and 

downslope of the roadway. Overnight, a 15-foot-wide 

section of the road slid downslope 10 feet (fig. 26). 

The slide was repaired with large amounts of silt 

excavated along the cut. Almost a year later, the 

same part of the road again slid 10 feet after attempts 

had been made to level minor slumps by the addition 

of a small amount of fill. Black layers above the 

culvert in the scarp of the landslide (fig. 26) are 

asphalt, representing layers of paving laid during the 

settlement or subsidence of the fill.

In nonpermafrost areas any fill or pad, whether it 

be for a railroad, highway, airstrip, or any other 

structure, requires adequate drainage along its margins. Improper drainage may saturate the fill and 

cause slumping^ or water may flow along the margins 

of the fill and cause erosion. In permafrost areas
ENGINEERING GEOLOGY 25

improper drainage causes additional problems. If 

the fill is allowed to saturate, it is much more susceptible to frost heaving and solifluction. In addition, 

water flowing alongside the fill may melt the permafrost and cause thawing and subsequent collapse. The 

results of inadequate drainage along the Sheep Creek 

road northwest of Fairbanks are shown in figure 27. 

Rainwater runoff, which should have been channeled 

away from the highway, was allowed to flow along 

the side. The water thawed the permafrost and the 

edge of the roadway collapsed as much as 8 feet. 

Thawing by flowing water does not occur only at the 

edge of the road but may also develop on the roadway itself.

Roads in permafrost areas that are built on the 

vegetation, without fill, quickly become useless. In

addition they may do irreparable damage to the environment. For example, at a camp in northwestern 

Alaska (fig. 28) trails over the tundra were made by a 

tracked vehicle called a "weasel." The trail from the 

camp to the upper right of figure 28 climbs to the top 

of a ridge. The constant use of weasels on this trail 

compacted and destroyed the protective vegetation, 

causing the underlying permafrost (about 1 ft below 

the surface) to thaw. This thawing was accelerated 

by runoff from rainfall, and by 1962 the gullies in the 

road were as much as 15 feet deep. In the area adjacent to the campsite the vegetation cover was completely destroyed, the underlying permafrost thawed, 

and quagmire areas formed.

The removal of the vegetation cover during winter 

highway construction will eventually create problems.

FIGURE 24. Thawed lake sediments flowing around blade of bulldozer. Ice-rich permafrost in the lake silts was exposed in a 

cut during the construction of the Richardson Highway 2 miles north of Paxson. Photograph by T. L. Pewe, June 1954.
26 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

L

FIGURE 25. Gravel road near the Umiat showing severe differential subsidence caused by thawing of ice-wedge polygons in

permafrost. Photograph taken in August 1958.

The winter road from Livengood on the Yukon River 

to Sagwon on the Arctic North Slope was constructed 

in the winter of 1968-69. By the end of the summer, 

it is almost certain that thawing will have advanced 

to the extent that the once high-speed road will be 

impassable in places. It will either require fill to 

bring the road up to grade or rerouting for use 

during the coming winter.

Figure 29 is a photograph of a tractor trail constructed on the north slope near Canning River during

the winter of 1967-68. The trail was built by bulldozing off the vegetation cover. The small ponds in 

the abandoned trail formed during the summer of 

1968. These ponds will continue to grow deeper and 

wider as the permafrost thaws.

Frost heaving of highway bridges is as severe as 

that of bridges on The Alaska Railroad. The same 

mechanism applies to both, whether the piles are of 

wood or of steel. Two examples of frost action on 

bridges one with wood piles whose ends were heaved
ENGINEERING GEOLOGY 27

FIGURE 26. Slump block of fine-grained highway fill material at Simpson Hill, near mile 113 on the Richardson Highway. 

Centerline of road formerly lay over exposed part of sheared culvert. Note bulldozer tracks on slump block surface, which 

are a continuation of those at road level on right side of photograph. Photograph by D. R. Nichols, September 1955.
28 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

and the other with steel piles whose center was 

heaved are shown in figures 30 and 31. The pattern 

of heaving damage depends largely upon the amount 

and distribution of water in the foundation material. 

Pewe and Paige (1963) present an explanation for 

the heaving of the ends of the bridge shown in 

figure 31.

Figure 32 is a photograph of a steel-pile bridge on 

the Kougarok Highway in the Seward Peninsula. 

This highway extended from Nome to the mining 

camp of Taylor, but is now maintained only to about 

mile 84. The steel piles driven into fine-grained saturated sediment heaved because of frost action. 

Yearly frost heaving of the piles has completely destroyed the structure. Center heaving of this bridge,

in contrast to the end heaving of the bridges shown 

in figures 30 and 31, was caused by the complete 

freezing of the flowing water and the underlying 

sediments during the winter. The underlying sediments at the point of maximum heaving of the piles 

contain a much higher moisture content than those 

elsewhere underneath the structure. The bridge at 

the outlet of Clearwater Lake (fig. 30) did not heave 

near the center of the structure because the flowing 

water and underlying sediments did not freeze.

Airfields

The gravel pad on an airstrip has the same effect 

on permafrost as the gravels fills on railroad and 

highway beds. Frost action or heaving also occurs on

FIGURE 27. Old Sheep Creek Road northwest of Fairbanks. Gully along edge of road was caused when the surface drainage 

thawed the permafrost in the underlying loess deposits. Photograph by T. L. Pewe, summer 1955.
ENGINEERING GEOLOGY 29

FIGURE 28. Oblique aerial photograph of Chariot Site, northwestern Alaska. Dark area to the left of camp was caused by the 

heavy equipment that moved over the terrain while the barges were being unloaded. Trails were caused by tracked vehicles. Photograph by R. H. Campbell, summer 1960.

airstrips, but generally does not present a major engineering problem. However, this does not necessarily mean that frost heaving should be ignored; it 

should be taken into consideration in determining the 

location of the airstrip and the design of the drainage 

system around the airfield.

For years the paved runways at Northway, Alaska, 

have been affected by thawing permafrost. The runways are underlain by fine silts and sand with local 

areas of ice-rich permafrost. At Gulkana, Alaska, 

where the airstrip also is paved, the runways are 

underlain by ice-rich clayey lacustrine silts. Because 

of differential subsidence the east-west runway at 

Gulkana has been condemned. At Umiat, the airstrip was constructed by placing a small gravel pad 

upon fine-grained sediments containing ice-rich permafrost. The runway was not paved. By 1952 the 

runway had subsided differentially to the extent that 

it had to be resurfaced with additional gravel (J. C. 

Reed, personal commun., 1969).

Buildings

A building has a different effect on the thermal 

regime of the underlying permafrost than does a road, 

a runway, or an open storage area. There have been 

many studies made of the influence of a building on 

the thermal regime of permafrost, including one by 

Lachenbruch (1957a). Lachenbruch's paper presents 

a basic formula for determining the thermal disturbance caused by a heated building as well as other 

important thermal problems caused by permafrost. 

For example, the geothermal disturbance caused by 

bodies of water and by highway and railroad fills can 

be analyzed by his theory. Brewer (1958) collected 

data beneath a heated building 40 feet by 100 feet at 

Barrow, Alaska, which showed that the temperature 

rose about 5V£° C at a depth of 20 feet. Based on 

Lachenbruch's formula, the temperature would rise 

about 6° C.

Some of the heated buildings at Barrow settled 

differentially as much as 20 inches in 3 to 4 years
30 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

FIGURE 29. Oblique photograph of tractor trail near Canning River, North Slope. Note small ponds due to thawing permafrost 

in roadway. Photograph by Averill Thayer, Bureau of Sport Fisheries and Wildlife, August 1968.

(Brewer, 1958). When the buildings were no longer 

heated the thawed ground beneath the structures refroze, and in some instances as much as 1 foot of frost 

heaving occurred within a year.

Figure 33 is a view of a roadhouse on the Richardson 

Highway. The building, constructed in 1951, subsided the most near the front of the center section 

where the furnace was located. The porch did not 

subside as much as the center of the building because 

it was unheated. The building had to be razed in 1965.

The problem of averting settlement of heated 

buildings in permafrost areas has received a great 

deal of attention. The most promising method of

solving the problem is to build the structure above 

ground with large air holes in the foundation. This 

allows the cold winter air to circulate beneath the 

floor of the building, counteracting the effects of the 

heat. Figure 34 is a photograph of a schoolhouse on 

a concrete foundation at Glennallen, Alaska. The 

air vents through the foundation are opened during 

the winter and closed during the summer. The jacks 

are used to keep the structure level because of differential subsidence in the ice-rich sediments that 

underlie the building.

Frost heaving of buildings is a common occurrence 

in arctic and subarctic environments. If piles are
ENGINEERING GEOLOGY 31

FIGURE 30. Frost-heaved piling of bridge spanning outlet of Clearwater Lake, 8 miles southeast of Big Delta. Piles are of

wood. Photograph by M. F. Meiser, August 1951.

After! L Pewe. 1951 10 0 10 20 FEET 

I______I_____I_____I 

HORIZONTAL AND VERTICAL SCALE

FIGURE 31. Geologic sketch of foundation conditions of frostheaved bridge, 8 miles southeast of Big Delta. Compare 

with figure 30. After Pewe and Paige (1963, p. 349).
32 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

FIGURE 32. Frost-heaved steel-pile bridge spanning North Fork at about mile 120 on the Kougarok Highway, Seward Peninsuk.

Photograph by G. D. Eberlein, summer 1955.

improperly emplaced, frost heaving is as damaging to 

buildings as it is to highway and railroad bridges. 

Buildings resting upon concrete foundations may be 

heaved beyond the yielding point of the concrete. 

Figure 35 shows the results of frost action upon the 

foundation for an apartment house in Fairbanks. The 

foundation was laid during the late summer of 1953 

and left exposed during the winter of 1953-54. The 

underlying flood-plain silts were saturated and during 

the winter sufficient ice formed to heave and rupture 

the structure.

Power and heating plants produce large amounts 

of heat which, if improperly insulated, may thaw the 

underlying permafrost. Therefore, these structures 

require special attention in location, design, and construction.

Aircraft hangers usually cover a large ground area 

and require heating. Because the underlying sediments vary, permafrost will thaw differentially, 

causing an uneven settlement of the floor.

Dams

Dams constructed on bedrock present no major 

permafrost or frost-heaving problems. However, if 

the structure is placed on sediments containing icerich permafrost, the impounded water will initiate 

thawing of the underlying permafrost. The dam will 

then settle differentially and will crack. Also, water 

may seep or be piped beneath the dam, eventually 

eroding the support for the structure; thus, a careful 

study of the nature of the reservoir section of the 

damsite should be made to determine whether the 

dam is founded in bedrock or sediments. Any frozen 

sediments under the impounded body of water will 

thaw, and will result in slumping and landsliding.
ENGINEERING GEOLOGY

Telephone and Power Transmission Lines

Telephone lines and powerlines carried on wood 

poles present major problems, because of frost 

heaving. Telephone and power poles are much more 

severely heaved than the bridge piles because the 

poles have a much less load and usually are not deeply 

emplaced in permafrost. Service and construction 

roads along the telephone lines and powerlines cause 

additional problems by melting the underlying permafrost. Eventually the roads become impassable and 

rerouting is necessary.

Large steel transmission lines requiring more than 

one foundation may heave differentially during the 

winter and settle differentially during the summer. 

These massive, usually high, structures are sensitive 

to differential displacement and may require continued 

maintenance in permafrost regions.

Pipelines

The construction of pipelines in an arctic environment is, at best, a major undertaking. If the pipeline 

is placed underground, the vegetation cover overlying 

the permafrost is destroyed, disrupting the thermal 

regime. This disruption can cause differential settlement of the pipeline, and, since it is underground, the 

settlement may not be noticed until the pipeline has 

been ruptured. If the line carries a warm fluid, it 

will thaw the permafrost and cause differential 

subsidence which could cause the structure to lose 

support.

Pipelines on the surface or on a supporting structure 

are subjected to frost heaving during the winter and 

subsidence during the summer. This action will be 

especially strong if the line passes over fine-grained 

sediment or over a bog or swamp. Other areas to be 

avoided are solif luction lobes where slow gravitational 

flowage of masses of surficial material occurs. These 

masses move downslope during the summer months 

after the active layer is thawed. If a pipeline were 

placed in or on these solifluction lobes, it probably 

would be damaged by the downslope movement. 

Therefore, such areas should be recognized and 

avoided. Another place to be avoided is the bottom 

of a stream channel, where winter ice on the stream 

might damage the pipeline.

In areas where the permafrost contains ice wedges, 

severe damage to an above-ground pipeline will occur 

if the ice wedges are allowed to thaw. The effects of

FIGURE 33. Roadhouse, mile 278.5, Richardson Highway. The structure is distorted because of thawing of the underlying 

ice-rich permafrost in fine-grained silts and sands. Photograph by T. L. Pewe, May 29,1962.
34 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

. *:iv ' -fS~'-^^S^'. ->lt

^.-^ -; ,~ e^^^'^^t^^^^vr H^-^9^ v - - -* ^ j .^ ^^%^^^j^f *,-, , - .,-.- J^ * " * "~ *****' sr-*?p'^r^r ^--^ -- -.* **»* .^7" ,,.- -_ "- ^»« ^JBT-^ -«^J ^

^^^ '-*' -ti *^ ~ , « <* * <! '' :"'>^:^'*i^K^ ..I?*., vsfc "r, t. i

"J^ ifc

 j£^ < >4; * *£ 'VJ^r * J-- ^ ri ^-

«r "

 ^*'--

i %..

WL,- *',V«ita. j

i S*%

_, i>, ? % " -ft &Hi£3i- ' -

 ._ TTT-' i .'^

FIGURE 34. View of the schoolhouse at Glennallen. Air vents, which are open, allow cold air to enter crawlway in winter to 

counteract heat from building. The vents are closed during the summer. Jacks are used to counteract any differential 

settlement. Photograph by T. L. Pewe, May 1954.

therefore, many utilidors are damaged by subsidence 

and frost heaving.

Above-ground utilidors are constructed in areas 

where the active layer normally freezes down to the 

permafrost table. These above-ground structures 

will be subjected to the same engineering problems 

as above-ground pipelines.

ICINGS

In arctic and subarctic regions, water which reaches 

the surface in the winter from a river or spring may 

freeze in successive sheets, until the ice covers a large 

area. These sheetlike masses are termed "icings." 

Icings are usually small seldom larger than a few 

acres. However, some as large as 48,000 to 54,000

thawing ice wedges has already been described in the 

the discussion of highways.

Construction and service roads for pipelines present 

the same problems as those built along powerlines 

and telephone lines.

Utilidors

Utilidors are used extensively in arctic and subarctic regions to carry utilities such as water, steam, 

gas, sewerlines, powerlines, and telephone lines. 

Figure 36 is a picture of a utilidor under construction 

near Fairbanks. An ideal location for an underground 

utilidor is an area underlain by well-drained ice-free 

materials that extend to depths of at least 15 feet. 

However, ideal locations are not always available, and,
ENGINEERING GEOLOGY 35

FIGURE 35. Fracture due to frost heaving of 4-inch concrete foundation of an apartment house in Fairbanks. Photograph by

T. L. Pewe, June 1954.

FIGURE 36. Utilidor under construction at Fort Wainwright near Fairbanks, Alaska. Photograph by T. L. Pewe, July 1947.
36 PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA

acres are found on the Mony River valley in Siberia. 

Icings as much as 30 feet deep, % mile wide, and 1 

mile long were noted in the John River valley south 

of Anaktuvuk Pass by T. C. Fugelstad of The Alaska 

Railroad during early 1969.

A study of icings on the Glenn, Richardson, and 

Alaska Highways of the Alaska Highway system 

indicated that they were quite extensive and usually 

occurred at road cuts (Williams, 1953). The maximum 

icings were about 5 feet thick and originated at seeps 

or springs. The Alaska Railroad is also plagued with 

winter icings. These are more damaging and require 

more maintenance than those on highways; the ice on 

the railroads has to be removed to expose the rails, 

whereas on highways icings need only to be leveled. 

Winter icing increases the maintenance costs, for it 

necessitates extra labor, special equipment, and 

special techniques to combat the growing ice mass. 

Countermeasures to reduce icing, such as the construction of larger culverts to divert the source of the 

icings, also increase construction costs.

Icings cause extensive damage to bridges through 

diversion of streamflow and burial of the structure. 

For example, river icings engulfed the bridge spanning 

the Chistochina River 26 miles west of Slana, Alaska. 

On February 15,1950, the ice was 6 feet below the 

bridge deck but had overflowed the west approach; it 

was necessary to reroute the traffic across the river 

ice (Williams, 1953).

Structures built on slopes may be filled with ice 

during the winter if icing conditions are suitable. 

Poorly insulated, heated buildings keep the underlying ground from freezing. If water with a hydraulic head is trapped between the frozen ground and the 

permafrost table, it may flow upward into the house. 

In some places, houses have been filled very rapidly 

by water that froze and filled the house with ice.

CONCLUSIONS

Construction and maintenance of structures underlain by permafrost pose a wide range of problems. 

Engineers, designers, and construction and maintenance personnel are continuously plagued by severe 

frost heaving of structures, subsidence due to melting 

ground ice, soil creep or solifluction, landslides, and 

icings related to the presence of permafrost.

Some guidelines that can be followed to minimize 

the adverse effects of permafrost and frost action 

upon structures are summarized below.

1. Wherever possible, locate structures on coarsegrained materials. Avoid fine-grained, poorly drained, 

ice-rich sediments, since they are subject to much

greater frost-heaving and, if the permafrost is thawed, 

to greater differential settlement.

2. Insofar as possible, make any gravel pad 

whether it be for a roadway, railroad grade, building 

site, airstrip, or drilling site sufficiently thick to 

prevent permafrost from thawing.

3. Provide ample and proper drainage around 

any structure to prevent the thawing of permafrost 

and to minimize frost action and icings.

4. For heated buildings, whenever possible provide space for circulating air between the surface of 

the ground and the floor to minimize the transfer of 

heat into the ground.

5. Avoid the disruption or destruction of the 

vegetation overlying permafrost by using such techniques as end-dumping. Restrict tracked vehicles, 

trucks, and other heavy equipment to roads and do 

not permit them on the tundra or vegetation where 

they will destroy its insulating quality and cause the 

permafrost to thaw.

6. Minimize frost heaving of supporting piles by 

providing the best possible drainage or by anchoring 

them securely in permafrost if feasible.

7. Avoid borrow sits upslope or downslope 

from structures. Thawing of the sites may cause 

drainage problems or damaging slumps and land 

slides.

8. Where parallel linear structures such as pipelines, roads, or telephone lines follow the contours 

of the slope, minimize disruption of the vegetation so 

that slumping along one structure will not damage 

the other.

9. Consider the following problems when pipelines are laid across creeks or rivers: a) If the pipeline 

crosses the creek or river underground, it may be 

damaged by the slumping of huge blocks of permafrost undercut at the banks, or it may be exposed by 

erosion and damaged by boulders, ice, or other debris 

during flood stage, b) Pipelines placed on the surface 

of a flood plain may be subject to inundation and possible damage by ice and floating debris.

10. Avoid construction in areas with natural icings 

whenever possible, or if such areas must be utilized, 

provide diversionary drainage.

The guidelines given above cannot be successfully 

applied without a thorough understanding of the 

thermal and mechanical problems unique to permafrost regions. Engineering procedures based on such 

an understanding should permit optimum utilization 

of the resources in the far north at a minimum overall cost and with a minimum disruption of the natural 

environment.
PERMAFROST AND RELATED ENGINEERING PROBLEMS IN ALASKA 37

REFERENCES CITED

Black, R. F., and Barksdale, W. L., 1949, Oriented lakes of northern Alaska: Jour. Geology, v. 57, no. 2, p. 105-118. 

Brewer, M. C., 1958, Some results of geothermal investigations

of permafrost in northern Alaska: Am. Geophys. Union

Trans., v. 39, no. 1, p. 19-26. 

Ferrians, O. J., Jr., 1965, Permafrost map of Alaska: U.S. Geol.

Survey Misc. Geol. Inv. Map 1-445, scale 1:2,500,000. 

Greene, G. W., Lachenbruch, A. H., and Brewer, M. C., 1960,

Some thermal effects of a roadway on permafrost, in Short

papers in the geological sciences: U.S. Geol. Survey Prof.

Paper 400-B, p. B141-B144. 

Holmes, G. W., Hopkins, D. M., and Foster, H. L., 1968, Pingos

in central Alaska: U.S. Geol. Survey Bull. 1241-H, 40 p. 

Hopkins, D. M., 1949, Thaw lakes and thaw sinks in the Imuruk

Lake area, Seward Peninsula, Alaska: Jour. Geology, v. 57,

no. 2, p. 119-131. 

Lachenbruch, A. H., 1957a, Three-dimensional heat conduction

in permafrost beneath heated buildings: U.S. Geol. Survey

Bull. 1052-B, p. 51-69. 

______1957b, Thermal effects of the ocean on permafrost:

Geol. Soc. America Bull., v. 68, no. 11, p. 1515-1529. 

_______1959, Periodic heat flow in a stratified medium with

application to permafrost problems: U.S. Geol. Survey Bull. 

1083-A, p. 1-36. 

___1962, Mechanics of thermal contraction cracks and icewedge polygons in permafrost: Geol. Soc. America Spec. 

Paper 70, 69 p.

J968, Permafrost, in Fairbridge, R. W., ed., The encyclopedia of geomorphology: New York, Reinhold Publishing 

Corp., p. 833-839.

Lachenbruch, A. H., and Brewer, M. C., 1959, Dissipation of the 

temperature effect of drilling a well in Arctic Alaska: U.S. 

Geol. Survey Bull. 1083-C, p. 73-109.

Lachenbruch, A. H., Brewer, M. C., Greene, G. W., and Marshall, 

B. V., 1962, Temperature in permafrost, in TemperatureIts measurement and control in science and industry: New 

York, Reinhold Publishing Corp., v. 3, pt. 1, p. 791-803.

Lachenbruch, A. H., Greene, G. W., and Marshall, B. V., 1966, 

Permafrost and the geothermal regimes, Chap. 10, Wilimovsky, N. J., and Wolfe, J. N., eds., in Environment of the Cape 

Thompson region, Alaska: U.S. Atomic Energy Comm. Rept 

PNE-481, p. 149-163.

Leffingwell, E. de K., 1915, Ground-ice wedges The dominant 

form of ground ice on the north coast of Alaska: Jour. 

Geology, v. 23, p. 635-654.

_____1919, The Canning River region, northern Alaska: U.S. 

Geol. Survey Prof. Paper 109, 251 p.

Mackay, J. R., 1966, Pingos in Canada, in Permafrost International Conference, Lafayette, Ind., 1963, Proceedings: Natl. 

Research Council Pub. 1287, p. 71-76.

Muller, S. W., 1943, Permafrost or permanently frozen ground 

and related engineering problems: U.S. Army, Office Chief 

of Engineers, Military Intelligence Div. Strategic Eng. 

Study 62, 231 p. Also 1947, Ann Arbor, Mich., Edwards 

Bros.

National Academy of Sciences National Research Council, 1966, 

International Conference on Permafrost, Lafayette, Ind., 

1963, Proceedings: Natl. Research Council Pub. 1287, 536 p. 

(Includes over 100 papers covering many aspects of permafrost research, as well as engineering and construction 

solutions for problems of building in permafrost areas.)

Nichols, D. R., and Yehle, L. A., 1961, Highway construction 

and maintenance problems in permafrost regions, in 

Symposium on geology as applied to highway engineering, 

12th Ann., 1961: Tennessee Univ. Eng. Expt. Sta. Bull. 24, 

p. 19-29.

Pewe, T. L., 1954, Effect of permafrost on cultivated fields, Fairbanks area, Alaska: U.S. Geol. Survey Bull. 989-F, p. 315-351.

_______1966, Ice wedges in Alaska Classification, distribution, and climatic significance, in Permafrost International 

Conference, Lafayette, Ind., 1963, Proceedings: Natl. Research Council Pub. 1287, p. 76-81.

Pewe, T. L., and Paige, R. A., 1963, Frost heaving of piles with 

an example from the Fairbanks area, Alaska: U.S. Geol. 

Survey Bull. 1111-1, p. 333-407. x

U.S. Weather Bureau, 1943, Climatic atlas for Alaska: U.S. Air 

Force Weather Div. Rept. 444, 229 p.; suppl., 72 p.

______1958, Climatic summary of Alaska Supplement for 

1922 through 1952, no. 11-43: 39 p.

______1950-68, Climatological data, Alaska: U.S. Weather

Bur., v. 36-54. 

Washburn, A. L., 1956, Classification of patterned ground and

review of suggested origins: Geol. Soc. America Bull., v.

67, no. 7, p. 823-865. 

Williams, J. R., 1953, Icings in Alaska, 1949-50: U.S. Geol. Survey

in cooperation with Engineer Intelligence Div., Office

Chief Engineers, U.S. Army, Eng. Notes 32, 23 p.

O