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Engineering site investigations in permafrost areas
Johnston, G. H.
Ser
Tirl
N21t2
no. p34
e . a
BI,DG
2 0 3 f , {
Nerrorual ReseencH CouNcrL
CANADA
Cousgl Nnrouel DE RecHeRcFrss
BY
G. H. JOHNSTON
A N A L Y Z E D
R E P R I N T E D F R O M
P R O C E E D I N G S : P E R M A F R O S T I N T E R N A T I O N A L
C O N F E R E N C E
N O V E M B E R 1 9 6 9
P . S 7 r - 9 7 4
TECHNICAL PAPER NO. 234
OF THED I V I S I O N O F B U I L D I N G R E S E A R C H
OTTAWA
ocToBER 1966
ENGINEERING
SITE INVESTIGATIONS
IN PERMAFROST
AREAS
srgcp
PRICE IO CENTS
.36
Reprinted from the PRoCEEDINGS: PEwAFRosr INTERNATIoNAL CoNFERENCE, NAs-NRc, publication IzSz
E N G I N E E R I N G
S I T E INVESTIGATIONS
I N PERAAAFROST
A R E A S
G. H. |OHNSTON, Nattonal Research Councll, Ottawa, Canada
T h r e e m a i n f a c t o r s hinder construction in arctic and subarctic r e g i o n s : L o g i s t i c s , c l i m a t e , a n d t e r r a i n I I ] . D i f f i c u l t a c c e s s and limited transportation facilities create problems in the m o v e m e n t o f p e r s o n n e l and materials lz, s), _climate, aI-though not much more severe than in more southefly regions ( s u c h as the Canadian Prairies or the Russian Steppes), differs mainly in the duration of cold weather rather than in extremes o f t e m p e r a t u r e [], S]. The long winter wii]r almost constant d a r k n e s s r e s u l t s in d very short field or construction season. The season is restricted further by periods of bre6kup and f r e e z e u p w h e n many areas are completely isolated. perhaps the most important factor that distinguishes nqrthern areas from o t h e r r e g i o n s i s the terrain [ 6], of which perennially frgzen ground (permafrost) is the dominant feature. More than 207o of t h e l a n d a r e a o f the world (including about S0% of Canadd is u n d e r l a i n b y p e r m a f r o s t .
Areas underlain by permafrost may be subdivided in several w a y s b a s e d on the ground thermal regime (ground temperature), but northern regions are usually divided into two bread zones based on the areal and vertical extent of the permafrosti the continuous zone, where permafrost is found everywhere to c o n s i d e r a b l e d e p t h ( > I 0 0 fd, and the disccntinuous zone, where relatively thin (< 100 fd put"IElliGGiEiEEE,.l
ground are separated by thawed areas. Within the disconunu-ous zone patches of permafrost range from very sporadic (near the southern boundary of the region) to extensive (in the northern part of this zone, where frozen ground predominates). Extensive atld varied occurrence of permafrost makes it a prime consideration in any northem engineering work.
Most engineering problems are caused by thawing of peren-n i a l l y f r o z e peren-n g r o u peren-n d w h i c h coperen-ntaiperen-ns large quaperen-ntities of ice. Ice segregation in soils (or rock) ranges from coneentratrons o f m i n u t e l e n s e s to large inclusions of ice several ft thick, D i f f e r e n t forms of ice segregation occur in al] soils, even in g r a v e l and coarse sand. The most sericus difficulties, how-e\rer, are encountered with frozen fine grained soils; even w h e n m o i s t u r e ( i c e ) content of these soils is very large, ice s e g r e g a t i o n i s often difficult to discern. Thus, presence of i c e and properties of soil in frozen and thawed states are of direct concern to the engineer.
Experience with permafrost and failures attributed to its unusual properties have shown that it affects every type of engineering project, be it selection of a new townsite or erection of a single structure in an established community. E v e n though much information has been collected in recent years on the relatively unpredictable occurrence of permafrost a n d i t s p r o p e r t i e s , the need for adequate site invgsiigations c a n n o t b e o v e r e m p h a s i z e d , The form and extent of investiga, t i o n s m a y v a r y , d e p e n d i n g on particular job requiremgnts,. but certain basic procedures should be followed in acquiring the information needed for good design and construction.
For any northern project, information should be collected to determine: (a) Distribution of permafrosi and conditions under which it exists and (b) properties of the permafrost.
Site investigdtions in any region are usually conducted in three phases, namely: Preliminary office studies and planning, f i e l d i n v e s t i g a t i o n s , and Iaboratory and office studie$
(prepa-r a t i o n o f (prepa-r e p o (prepa-r t s ) .
Planning of each phase requlres greater attention when northern sites are considered, primarily because of permafrost but due also to the relative isolauon and general lack of knowledge of the terain. Ttris paper suggests a loglcal sequence for carrying dut site investlgations in permafrost a r e a s [ 7 ] .
" S i t e i n v e s t i g a t i o n , " a s u s e d h e r e , is limited to those phases of an over-all site evaluation which pertain to the collection of information on permafrost condltions. Except for illustrative purposes, no attempt is made to describe proce-dures which apply only to speclfic types of projects, such as railroad or road location and construction, water supply and d i s t r i b u t i o n systems, or buildings. Comments made, however, apply to aII types of engineering projects.
At least a year is generally required to complete an ade-quate engineering site investigation in permafrost areas. Some overlapping of the three phases will occur since certain por-tions of each are better conducted at different times of the y e a r . Depending on the type of project, invesugations may b e completed in much less than one year; for others, work may c o n t i n u e w e l l into a second year, but in general, a one year period is needed to assess properly all site conditions affect-i n g d e s affect-i g n and faffect-inal plannaffect-ing [81.
PRELIMINARY OFFICE STUDIES AND PLANNING
E m p h a s i s must be placed on careful planning and compilation of pertinent information prior to conducting field investigations. This preliminary work is normally carried out several months p r i o r to the field season. For most areas, the season begins in March or April. Much time and effort can be saved (and survey costs reduced) if the area has been thoroughly studied beforehand. In addition, depending on information acquired d u r i n g t h i s i n i t i a l study, some assessment can be made of foundation designs and construction techniques which might b e u s e d .
Background Information
Although meager informatlon is available for many northern r e g i o n s , d a t a o n adjacent or similar areas may provide useful information on generpl conditions which may be encountered. Of parttcular interest is a knowledge of the geology and cli-matet both are intimately connected with the formation and existence of permafrost.
Many northern areas have been geologically mapped, albeit Superficially in most instances. Reference to such maps and to published reports can provide much information of value. Most of the Arctic and sub-Arctic have been glaciated; thus, accounts of the glacial history are of specific interest wlth respect to soil and permafrost conditions. Accounts of the travels of many early explorers and geologists provide v a l u a b l e d e s c r i p t i o n s of the terrain and geomorphology [9].
Cllmate plays an important role with respect to permafrost, particularly wit}t regard to the ground thermal regime I l0]. Broad correlatlons exist between the occurrence of permafrost
and air temperature I i t , t Z] . In addition, although the north is generaUy known as an ar.id or semi-arid region, precipita-t i o n , precipita-t h r o u g h s u r f a c e d r a i n a g e , h a s a c o n s i d e r a b l e e f f e c precipita-t ' M e t e o r o b o g i c a l r e c o r d s . I I 3 ] s h o u l d a l w a y s b e e x a m i n e d a n d summarizedto evaluate local climate with respect to perma-f r o s t . X n o * l e d g e o { l o c a l c l i m a t e i s a l s o i n v a l u a b l e , o J c o u r s e , i n p l a n n i n g f l € l d o p e r a t i o n s .
A c o m p l e t e f o l i o o f p e f t i n e n t m a p s , g e o l o g i c . t o p o g r a p h i c , a n d h y d r o l o g i c ( i f a v a i l a b l e ) , c o v e r i n g t h e a r e a s t o b e i n v e s t i -gated, will provide further informatlon and will also be useful f o r r e c o r d i n g f i e l d o b s e r v a t i o n s . S c a l e s o f I : 5 0 , 0 0 0 o r l a r g e r a r e m o s t u s e f u l b u t m a p s o f s m a l l e r s c a l e s h o u l d n o t b e d i s
-regarded. Most of northern North America has been mapped
to some degree and maps are generally available through the F e d e r a l G o v e r n m e n t s o f C a n a d a a n d t h e U . S . A .
An important source of information, often neglected, is con-t a c con-t w i con-t h a g e n c i e s , f i r m s . o r i n d i v i d u a l s w h o w o r k o r h a v e w o r k e d i n t h e a r e a s u n d e r i n v e s t i g a t i o n . I n m a n y c a s e s u s e f u l
site information is available from those with exploratory, de-v e l o p m e n t , o r c o n s t r u c t i o n e x p e r i e n c e i l l t h e a r e a ( e . g . , m i n i n g c o m p a n i e s , t r a p p e r s , a n d p r o s p e c t o r s ) . C o n t a c t w i t h s u c h people can be made prior to and during the field exploration. Observations on performance of existing structures are also m o s t v a l u a b l e .
Airphoto Studles
Airphotos provide the most valuable aid for preliminary planning
and site evaluation Ira]. eirptroto coverage, to various
scales, is now readily available for most northern regions' The airphoto serves as a mapi the surface features on this map (together with a knowledge of the geologic and climatic history of the areJ. when properly interpreted, can yield a wealth of i n f o r m a t i o n o n s u b s u r f a c e c o n d i t i o n s I t s , t 0 ] ' s o i l t y p e s a n d permafrost conditions are indicated by or can be inferred from
relief, vegetation, and drainage characteristics. Color tones
on photographs provide further clues. Detrimental permafrost
areas can be identified and delineated by recognizing phe-nomena such as soil polygons and patterned ground forms resultlng from frost action I l7] . Ice-wedge polygons may
vary in diameter fiom l5 to 500 ft. Pingos, thermokarst lakes,
"drunken forests,'r or ground subsldence caused by thawing of
large buried ice masses, solifluction lobes or terraces, frost
mounds, hummocks, and mud boils can all be readily identi-fied; when seen on an alrphoto, they indicate potenually unsuitable foundation conditions.
The topographic posiuon of a locality is perhaps the most important feature related to permafrost that can be recognized on an airphoto; this assists greatly in predicting permafrost conditions slnce detrimental permafrost conditions generally
occur in certain topographic situauons. For example, many
of the phenomena Just mentioned are associated with low-lying a r e a s , s u c h a s c o a s t a l p l a i n s a n d s t r e a m v a l l e y s o r d e p r e s -s i o n -s i n u p l a n d a r e a -s .
Dense forest growth' particularly in the discontinuous permafrost zone, may mask ground surfac-e features on an
air-p h o t o . Certain vegetation associations Itg-Zt] a r e c l o s e l y
related to subsurface conditions and permafrost occurrence and, therefore, when considered together with topographic
position, sQil'texture, and drainage, can serye as fairly
reliable indicators.
In general, the surface drainage pattern is little altered
by permafrost. Local drainage patt€rns and characteristics
(e.g. , "beaded" or "button" streams) seen on airphotos do,
however. provide useful clues. The thawing effect of water'
either still gr running; on the occurrence and termal reglme of permafrost ls great because of its heat storage capacity
and powers of erosion. Slumped lake banks and polygonal
surface features disintegrated by running water are evidence of this effect.
Most surface features associated with permafrost are the resulf of a complex relationship of many factors such as cli-mate, geology, freezing and thawlng, relief, and drainage
[22]. Much depends on the experience of the airphoto
ttreader"
and his ability to analyze and lnterpret what he 3 7 2
sees. Even though permafrost and general terraln conditions
can be predicted fairly reliably from airphotos, it is still n e c e s s a r y t o v i s i t s e l e c t e d a r e a s w h i c h h a v e b e e n s u b d i v i d e d o n t h e b a s i s o f s i m i l a r t e r r a i n c h a r a c t e r i s t i c s ( e . g . . r e l l e f , drainage, and vegetatiorJ in order to verify the interpreted c o n d i t i o n s l z s , z q ) .
Planqlng
Careful planning for field operations is essential if the work is
to proceed efficiently and economically' Movement of
person-nel and equipment into and about the areas under investigation is affected greatly by difficult access and lack of
transporta-tion at certain times of the year. Special care is required in
planning for prorects such as road location surveys which
cover Iarge areas and varying types of terrain' Every detail
m u s t b e c a r e f u l l y t h o u g h t o u t b e c a u s e t h e f i e l d s e a s o n i s
short and supply lines are usually long and difficult' Good
c o m m u n i c a t i o n s a r e e s s e n t i a l .
Personnel selection is very important. An experienced civil
engineer should supervise and coordinate all activities' Most
surveys require a glacial geologist preferably with training in geomorpholoqy, a soils engineer, and,/or civil engineer assited
by technicians' AII should be well qualified and very familiar
with permaftost. Depending on the objectives and scope of the
t h e p r o j e c t , o t h e r s p e c i a l i s t s m a y b e r e q u i r e d , e ' g ' , a b o t a n i s t
and a hydrologist' If local labor is not available' additional
assistance will have to be brought in.
T h e s u c c e s s o f t h e i n v e s t i g a t i o n w i l l d e p e n d l a r g e l y o n t h e degree to which the work has been preplanned and on the knowledge of the area which the field workers have acquired b e f o r e e n t e r i n g t h e s e c o n d p h a s e , i . e . , t h e f i e l d i n v e s t i g a t i o n '
FIELD INVESTIGATIONS
Field investiqations are usually carried out in two stages: An
explatory survey is conducted over wide areas to assess general site conditions and factors which influence permafrost and to select sites for detailed examinationi and detaiied
investigations are conducted at selected sites to gather
detailed information on permafrost conditions relevant to the design of structures and construction techniques to be used'
Exploratory Survey
Potential sites or routes selected by preliminary office studies, primarily through the use of airphotos, are examined during
this stage. These areas are evaluated for their suitability in
all seasons. Geological studies include bedrock control and
the glacial history (with which permafrost is closely associ-ated) of the over-all area with more detailed examinations at s p e c l f i c l o c a t i o n s .
A terrain reconnaissance is made to map topographic features including relief, drainage, and vegetation patterns
and characteristlcs. Areas of patterned ground and permafrost
phenomena are delineated. locations of "icings" are noted'
Lake and stream ice tlicknesses and snow accumulation
patterns and depth are observed. Transit and tape and level
surveys are made to establish horizontal and vertical control for the area. Field sketches or plans are prepared on which
all terrain information can be recorded. Data can also be
noted on airphotos or topographical maps already available' Determinatton of the distribution of permafrost is the most
important aspect of thb exploratory survey. Selected areas
are examined by borings. test pits, and probings to check predictions and to determine abtual subsurfape conditions' Distribution of permafrost, its areal and vertical extent, and factors which appear to control its existence such as drainage (surface and subsurface), vegetation (type and thickness of moss cover), and topographic position are very important, particularly along the southern fringe of the permafrost region'
The depth to which seasonal freezing and thawing penetrates (active layed and the rate at which these processes take place, the depth to the permafrost table, the presence of taliks (unfrozen zones) within permafrost, and the movement of
sub-surface water are algo factors that must be determined. Types o f i c e s e g r e g a t i o n and various materials with which they are a s s o c i a t e d m u s t b e k n o w n a n d d e l i n e a t e d .
S a m p l e s o f p e r e n n i a l l y f r o z e n matertals can be obtained in s e v e r a l w a y s [ 25J, Naturally occurring exposures and hand boring methods will provide general information for relatively s h a l l o w d e p t h s . T e s t p i t s a n d c o r e d r i l l i n g p r o v i d e d e t a i l e d i n f o r m a t i o n o n s o i l s a n d i c e s e g r e g a t i o n t o g r e a t e r d e p t h s .
G e o p h y s i c a l m e t h o d s 126, 27) to determine the depth to a n d e x t e n t o f p e r m a f r o s t h a v e h a d i n c r e a s i n g a p p l i c a t i o n . S e i s m i c r e f r a c t i o n s o u n d i n g s a p p e a r t o b e s u i t a b l e f o r d e t e r -m i n i n g t h e u p p e r I i -m i t o r d e p t h t o p e r -m a f r o s U e l e c t r i c a l r e s i s t i v i t y m e t h o d s a r e m o s t u s e f u l i n d e t e r m i n i n g the thick-n e s s o f ' p e r m a f r o s t . E x p e r i e n c e i n their use is limitecl, h o w e v e r , a n d r e l i a b i l i t y o f r e s u l t s d e p e n d s t o a great extent u p o n t h e i n t e r p r e t a t i o n .
Suitable instrumentation and observation programs (to o b t a i n d a t a f o r the designer and planned should be set up early in the exploratory stage of the field work. Meteorologi-c a l o b s e r v a t i o n s , i n Meteorologi-c l u d i n g measurement of air temperatures. precipitation (rain and snow), and wind (direction and velocity) should be made to provide information on local climate. P e r m a f r o s t i s d e f i n e d on a temperatuie basis; thus, data on the ground thermal regime is needed to describe permafrost con-d i t i o n s . G r o u n d t e m p e r a t u r e installations should be made to d e p t h s o f a t l e a s t 2 0 ft and greater if possible. Ground move-ment gages may be necessary in many cases to determine detrimental effects due to freezing and thawing of the active layer. Observations on the rate and depth of thaw under v a r i o u s t e r r a i n conditions are also essential and should be made throughout the thawing season (the maximum thaw will be observed in the late fall) by simple hand probing methods. To provide useful information, such observations should be m a d e o n a r e g u l a r daily, weekly, or monthly basisi since, in m o s t c a s e s , t h e o b s e r y a t i o n p e r i o d should cover at least six m o n t h s , t h e o b s e r v a t i o n s should be started as soon as p o s s i b l e .
Finally, the construction and performance history of similar structures in the area wiII provide much information on site c o n d i t i o n s , T h e s e sources will prove of inestimable value to the designer and should not be overlooked. Observations on existing structures 5fuguld be initiated at this stage.
Exploratory survey is the most important stage of a field i n v e s t l g a t i o n . A l t h o u g h i t s p u r p o s e j s to obtain general infor-m a t i o n o n s u r f a c e and subsurface conditions over a wide area, and it might therefore be considered rather superficial, results obtained dictate to a large extent the future of the proposed project. On the basls of the information obtained, unsuitable areas are eliminated and final sites and routes selected for more detailed examination, Design criteria and construction methods and techniques also evolve during this stage. Thus, it is a critical period of extensive and intensive examination of al] factors related to permafrost and its effect on the proposed project.
D e t a i l e d I n v e s t i g a t i o g
This phase of the field program provides the detailed informa-tion needed for final planning and design of the project. V a r i o u s c o n s t r u c t i o n methods and techniques are assessed a n d s e l e c t e d d u r i n g this stage. this work is done at sites selected during the exploratory sun/ey to supplement informa-tion already obtained. Preliminary designs may be drawn up during this stage and layout of structures at approved sites b e g u n . T h e f i e l d supervisor of this stage should be complelely familiar with the requirements of the project so that he can direct the field program along tlre right paths. C]ose coordi-nation of all operations between field and head offices is nece s sary.
Observations begun during the exploratory survey (including depth of thaw in disturbed and undisturbed areas and ground temperature measurements) are continued and expanded. More detailed records of subsurface conditions at actual construc-t i o n s i construc-t e s a r e r e q u i r e d in selecconstruc-ting foundaconstruc-tion designs [28). In pafiicular the ground thermal regime should be critically
analyzed, and the form and extent of ice segregation in the u n d e r l y i n g m a t e r i a l s s h o u l d b e n o t e d l n a e t a i l [ 2 5 ] .
Test pits have particular application to site exploration ln a r e a s c o v e r e d w i t h d e p o s i t s o f s t o n y t i l l s o r g r a v e l . A m a j o r advantage of this method is that it permits the frozen soil and the ice segregation to be examined in the undisturbed condi-tion, They can be excavated at any time of year to depths of 20 to 30 ft by compressed-air or gasoline-engine jackhammers. Core-drilling methods to obtain undisturbed frozen samples are widely used for investigations to depths of 20 ft or greater. Although corase grained soils have been successfully sampled using special refrigeration equipment and techniques I Zg] , drilling methods are most applicable in fine grained soils. Good cores of undisturbed material can be sampled for mois-ture (ice) content and unlt weight determinations and for identification and classification of soils encountered. Some testing may be done at the site, but many samples are shipped out in plastic containers (to reduce welght and thus transpor-tation costs) for laboratory analysis. Although refrigerated methods can be used to ship samples, itjs difficult to pre-serve specimens in the frozen state and therefore photographic techniques have been developed to provide a pennanent record.
At this stage actual test installations at the site can be made and construction procedures can be developed. For instance, if pile foundations are under consideration, field s t u d i e s m i g h t i n c i u d e a n e v a l u a t i o n o f p i l e - p l a c i n g t e c h n i q u e s and pile-load and pull-out tests to determine adfreezing strengths, Test fills might be constructed for road and air-strip design purposes. Bearing capacity tests of frozen soll might also be included. Although it takes time to accumulate useful results, much valuable information can be obtained at this stage, particularly for large construction programs which m a y t a k e several years to complete, e.9., roads, railrcads, and townsite developments. Some construction may be started during this early period but it will be generally Iimited to such activities as site preparation and opening of bortow pits. In these cases it is useful to obsenre methods of excavating and the handllng and placing of flrozen and thawed materials.
Detailed terrain conditions are accurately and specifically described and delineated, Topographic maps, with contour intervals of from 2 to 5 ft are required to portray surface con-figurations and conditions. Subsurface information including soil and permafrost conditions at or along finally selected sites and routes are shown on plans, and sections or logs and are described by test results and written reports.
During both the exploratory and detailed surveys, informa-tion collected in the field is sent back to the head office for evaluation with respect to the project as a whole. Although over-all direction of the field work may come from there, many decisions as to the course of the work must be made by the field supewisor. Various phases of each type oI suryey
may overlap or be carried on at the same time and in conJunc-tion with each other. Nothing should be overlooked or omitted during these stages so that final planning and design may pro-ceed without delay. It may not be possible to obtain missing or forgotten information until the following year.
FINAL STUDIES AND PREPARATION OF REPORTS
This phase of site investigation consists primarily of office studies directed torivard presentatlon of all site informatlon needed for the planning and design of engineering structures. Evaluation of laboratory test results of the physicomechanical properties of the materials encountered at construction sites are of prime importance for foundation design and selection of construction procedures and techniques, Preparation of de-tailed maps and drawings showing terrain conditions at appro-priate scales is necessary for final route selection and proper siting of structures. The designer and planner is dependent wholly on information ln the final reports and recommendations o f f i e l d w o r k e r s . E m p h a s i s must be placed upon preparation of thorough and detailed reports.
Some thought should be given to continuing and expanding observations begun during field investigations. Observations.
such as ground temperatures, depth of thaw in undlsturbed and disturbed locations, and effects of and changes in drainage patterns (both surface and subsurface, though not always of immediate value) will provide useful information for future projects in the area. Studies should be continued by instru-mentation and observation of the perfoimance of various structures and their effects on permafrost conditions. Such studies will provide valuable information for future work of s i m i l a r nature.
Many investigations have been made at various northern locations. Unfortunately, experience gained and conditions encountered are seldom recorded. There is a great and imme-diate need for such information to increase our knowledge of permafrost and the conditions under which it exists, All engaged in northern work are urged to record their observa-tions for the general benefit.
REFERENCES
t t ] n . F . L e g g e t , H . B . D i c k e n s . " B u i l d i n g i n N o r t h e r n C a n a d a , " N a t l . R e s . C o u n . D i v , B l d g . R e s . , T e c h , P a p e r N o . 6 2 , 1 9 5 9 .
t Z ) P . D . B a i r d . ' r T r a n s p o r t a t i o n , " Geography of the N o r t h l a n d s , Kimble and Good, ed., Am. Geog, Soc., Spec. P u b , N o . 3 2 , J o h n W i l e y , 1 9 5 5 , p p . I 8 7 - 2 0 9 ,
[ 3 ] K . B . w o o d s , R . F , L e g g e t . "Transportatronand E c o n o m i c P o t e n t i a l ln the Arctic,', &Mg9g!., 1 9 6 0 , p p . 4 3 5 - 4 5 8 .
t a ] n . A , T t r o m p s o n . "TemperatureNormals Averages, and Extremes in the Yukon Territory and the Northwest Territory," A r c t i c , V o l . 1 5 , I 9 6 2 , p p , 3 0 8 - 3 1 2 .
L5J R. W. fue. Climate of the Canadian Arctic Archipelago. D e p t . T r a n s p o r t , Meteorological Div., Forn 9002, Toronto. 1 9 5 1 .
[e] U. Dunbar, K. R. Greenway. Arctic Canada from the } ! 1 . , D e p t ' N a t l . D e f e n c e , D e f e n c e R e s . B d . , O t t a w a , 1 9 5 6 .
L7J N. I. Saltykov. "Methods of Englneering Geocryological InvesUgations, "
V. A. Obruchev Inst. Geocryology, Acad. Sci. U 1 9 5 9 , P t . 2 , p p . 2 9 8 - 3 4 7 .
Ig] S. Muller. Permafrost or Permanently Frozen Ground and Related Engineerlng Problems, U. S. Army, Office Ch of Engs., S p e c . R e p t . , S t r a t e g i c E n g r . S t u d y N o . 6 2 , f 9 4 5 .
t g l S . d e K . L e f f i n g w e l l . " T h e C a n n i n g R i v e r R e g i o n , N o r t h e r n A l a s k a , " U . S . G e o l . S u r v e y , P r o f . P a p e r I 0 9 , 1 9 1 9 .
[ro] n. F.
Lesset@.r*u-frost Investigations in Canada," Proc. Ist Intl. Symp. Arctic 9 e o . l o g y , Y o l . 2 , 1 9 6 1 , p p . 9 5 6 - 9 6 9 .
L t I J R , J. E. Brown. r r T h e Distribution of Permafrost and Its Relation to Air Temperature in Canada and the U. S. S. R. , " A r c t i c , V o l " 1 3 , 1 9 6 0 , p p . 1 6 3 - 1 7 7 .
I17f rf . A. Ttrompson. "Freezing and Thawing Indices in N o r t h e r n C a n a d a , " P r o c . I s t C a n . C o n f . 4ermafrost. Natl. R e s . C o u n ' C a n a d a , T e c h . M e m . N o . 7 6 , 1 9 6 3 , p p . 1 8 - 3 6 . [13] CUmaUc Summaries for Selected Meteorological Stations
in Canada, Dept. Transport, Meteorological Branch. Vol. I, 1 9 4 7 , a n d A d d e n d u m to V o l . l , 1 9 5 4 .
Ita] n. E. Frost. "Aerial Photography inArctic and Subarctic E n g i n s e r i n g , " J. Air Transport Div., Am. Soc. Civil Engrs., V o l . 8 6 , 1 9 6 0 , p p . 2 7 - 5 6 .
I tS] n. E. Frost. "Interpretation of Permafrost Features from Airphotographs, " EE!lg!!gig$, U. S. NAS-NRC, H i g h w a y R e s . M . , S p e c . R e p t . N o . 2 , 1 9 5 2 , p p . 2 2 3 - 2 4 6 . I t O ] O . J. Belcher. "Determlnationof SoiI Conditions bi Aerial Photographic Analysis," @
M e c h a n i c s F o u n d a t i o n E n g . , R o t t e r d a m . 1 9 4 8 , V o l . I , p p . 3 I 3 - 3 2 1 .
I t z ] a . L . W a s h b u m . " C l a s s i f i c a t i o n o f P a t t e r n e d G r o u n d a n d R e v i e w o f S u g g e s t e d O r i g i n s , " G e o l . S o c . A m . B u l l , , V o l . 6 7 , I 9 5 6 , p p . 8 2 3 - 8 6 6 .
I t a ] H , P . H a n s e n . "Postglacial Forests in the Yukon T e r r i t o r y a n d A l a s k a , " A m . J . S c i . , V o l . 2 5 1 , f 9 5 3 , p p . 5 0 5 - 5 4 2 .
I tS] l. Hustich. "The Boreal Limits of Conifers, " 4!g!']!g, V o I . 6 , 1 9 5 3 , p p . I 4 9 - 1 6 2 .
I Z O ] U . E . B r i t t o n . "Vegetation of the Arctic Tundra," Arctic Bio.l. , BioI. Colloquium, ed. H. P: Hansen, Oregon s t a t e c o l l . , 1 9 5 7 , p p . 2 6 - 6 r .
I z t ] n . J. E. Brown. * ' E f f e c t s of Vegetation of Permafrost." i n t h i s v o l u m e ,
L z z l f . B . W o o d s , J. E. Hittle, R. E. Frost, "Correlation Between Permafrost and Soils as Indicated by Aerial Photo-graphs, " !roc. , 2nd Internl. C Me*._ a"d P o u n d a t i o n E n g . , R o t t e r d a m , V o l . l , 1 9 4 8 , p p . 3 2 1 - 3 2 4 . L 2 3 J G . H , Johnston, R' I. E. Brown. D. N' Pickersglll. Permafrost Investigations at Thompson, Manitobd- Terrain S t u d i e s , N a t l . R e s . C o u n ' C a n a d a , D i v . B I d g . R e s . , T e c h . P a p e r N o . 1 5 8 , I 9 6 3 .
Lzel n, C. Sager. "Aeriai Analysis of Permanently Frozen G r o u n d , " P h o t o g r a m m e t r i c - E l S ! , V o l . I 7 , 1 9 5 6 , p p ' 1 2 3 ' 1 3 2 .
t z s l c . H . I o h n s t o * @ ,
N a t I . R e s . C o u n . C a n a d a , D i v . B l d g . R e s . , T e c h . P a p e r N o . 1 5 5 .
I Z o ] g . R. Joesting. "Geophysical Exploration in Alaska," A r c t i c , Y o L . 7 , r 9 5 4 , p p . 1 6 5 - r 7 5 .
lnTn. Roethlisberger. "The Applicability of Seismic Refrac-tion Soundings in Permafrost near Thule, Greenland," Tech.' R e p t . N o . 8 r , U . S . A r m y C R R E L , 1 9 6 I .
mT L. A. Nees, A. |ohnson. "Preliminary Foundation Ex-ploration in Arctic Regions." Symp. Surface and Subsurface R e c o n n a i s s a n c e , A S T M , S p e c . T e c h . P u b l . N o . l 2 Z , 1 9 5 1 , p p . 2 8 - 3 9 .
[ Z g ] V t . J. Hvorslev, T. B. Goode. "Core Drilling in
Frozen
Univ.
Ground, "
This paper from the Division of Building Research, National R e s e a r c h C o u n c i l , C a n a d a , i s p u b l i s h e d w i t h t h e a p p r o v a l o f the Director of the Division'
M i n n . , M i n n e a p o l i s ,
