Cold regions practice and research in Canada

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Cold regions practice and research in Canada

Ser

TKL

COLD REGIONS PRACTICE AND RESEARCH I N CANADA

N21d

'*

c. 2

by C.B. Crawford and L.W. Gold

National Research

Conseil national

Council Canada

de recherches Canada

ANALYZED

l3Lm

Reprinted from

_,

_,.-*Q

.a. C 1 International Conference on Engineering and Development 1 B ' -

9

-

*'

in Northern Regions -- .

- -

_ -

--

- C r , Sapporo, Japan, Jan 3 1

-

Feb 2, 1983

Proceedings, p. 59

-

91

DBR Paper No. 1287

Division of Building Research

ABSTRACT

This paper presents information on current Canadian practice

and capability for construction in winter and in permafrost

regions, designing for frost action, construction of energy

efficient buildings, building winter roads and ice platforms,

controlling snow drifting, designing for snow loads and for

specifying avalanche defense systems.

Some current research

needs are identified and consideration is given to

international cooperation in research on cold regions

problems.

Ce document renseigne sur les m6thodes actuelles de

construction utilisses au Canada en hiver et dans les rggions

de perg6liso1, les ressources dont on dispose,

la

conception en

fonction des effets du gel, la construction de bgtiments 3 bon

rendement gnerggtique, la construction de routes d

'hiver et de

plates-formes de glace,

la- A-

v

t

s

de

neige, le calcul des

c'

la

sp6cification des mesur

6

Quelques-uns des be2

identifi6s et une ate

L

coopikation internatia

c

Hokkaido Development Engineering Center

CORD

Cold Regions Development Society

COLD REGIONS PRACTICE AND RESEARCH IN CANADA

by C. B. Crawford and L. W. Gold

Reprinted from

International Conference on Engineering and Development in Northern Regions

Sapporo, Japan, Jan 31

-

Feb 2 , 1 9 8 3 Proceedings, p. 5 9

-

91

International Conference on Engineering and Development

in Northern Regions

COLD REGIONS PRACTICE AND RESEARCH I N CANADA

C.

B. Crawford

L.

W.

Gold

Director

Associate Director

Division of Building Research

National Research Council Canada

Ottawa, Canada

SUMMARY

Most of Canada experiences freezing temperatures each year.

Cold

has been a major factor in the development of Canadian transportation

systems, construction practices, building forms and life styles. Many

of these developments have come about through experience, initiative and

enterprise rather than research.

Cold related phenomena that have

provided incentive for this work include heat loss, frost action,

permafrost, ice, snow and avalanches. The paper presents information on

current Canadian practice and capability for construction in winter and

in permafrost regions, designing for frost action, construction of

energy efficient buildings, building winter roads and ice platforms,

controlling snow drifting, designing for snow loads and for specifying

avalanche defense systems.

Factors that justify research on problems in cold regions are

briefly considered.

In southerly regions cost, energy supply, energy

conservation

and transportation have been

important

incentives.

Practice that is suitable for southern cold regions may not be directly

applicable to the North.

Many projects in the North challenge the

limits of present capability, technology and methods and provide the

motivation for much research.

The paper makes reference to two

important studies that have been carried out in Canada on research needs

for engineering in cold regions.

Some current needs are identified and

consideration is given to international cooperation and collaboration in

research on cold regions problems.

Most o f Canada experiences f r e e z i n g t m p e r a t u r e s each year. Near the A t l a n t i c Ocean t h e mean d a i l y minimum temperature i n January i s about -lO°C.

Storms w i t h heavy snow o r r a i n and h i g h winds E r e common. I n southern Quebec

and O n t a r i o t h e mean d a i l y minimum temperatures vary from about -20°C t o -lO°C. Storms are l e s s f r e q u e n t than near t h e A t l a n t i c coast and p r e c i p i t a t i o n i s l e s s ,

b u t snow g e n e r a l l y remains f o r a l o n g e r p e r i o d o f time. I n the c e n t r a l o r

P r a i r i e regions o f t h e c o u n t r y t h e mean d a i l y tgmperatures f o r January a r e i n

t h e range o f -25°C t o -20°C. Snowfall i s l o w e r than i n Eastern Canada, b u t

b l i zzards accompani ed by h i g h w i nds and 1 ow t e ~ p e r a t u r e s usual l y occur every

w i n t e r . Long p e r i o d s when temperature i s l o w g r than -20°C a r e common. I n

B r i t i s h Columbia mezn d a i l y minimum temperatures vary from b e ! w - i O ° C i n t h e

i n t e r i o r t o near 0°C on t h e P a c i f i c coast. P r g t i p i t a t i o n i s heavy, o c c u r r i n g

m a i n l y as snow i n t h e mountains and as r a i n n e z r Vancouver.

For more t h a n 50% o f t h e c o u n t r y t h e avzrage annual a i r temperature i s

s u f f i c i e n t l y low f o r t h e grocnd not t o t h a x c o c p l e t e l y i n scmzr. The

d i s t r i b u t i o n o f t h i s p e r e n n i a l l y frozen around ( p e n a f r o s t ) and i t s r e l z i i o n t o

t h e isotherms o f average annual a i r temperature a r e presented i n F i g u r e 1. I n

the d i s c o n t i n u o u s zone j u s t n o r t h o f t h e southern l i m i t o f perinafrost i t e x i s t s

as i s l a n d s , t h e i r occurrence degending on t e r r z i n , v e g e t a t i o n , and amount o f

s n o w f z l l . The t h i c k n e s s v a r i e s from l e s s than 2 meter i n t h e discontinuous zone

The foregoing indicates t h a t Canada i s subject t o the f u l l range

o f

winter conditions.

Cold has been

a

major f a c t o r in the developaent of

transportation systems, construction p r a c t i c e s , building forins and l i f e s t y l e s .

Because cold i s so much a part of the normal cycle of nature t o which Canadians

a r e accustomed, many developments have come about through experience

,

i n i t i a t i v e

and e n t e r p r i s e r a t h e r than research.

In t h i s paper i t i s not possible t o cover

a l l aspects of p r a c t i c e s t h a t have evolved because of the cold climate, nor i s

i t possible t o do j u s t i c e t.o those t h a t have been developed through research.

Instead, a few t o p i c s will i l l u s t r a t e t h e present capability of Canadians t o

l i v e and work under cold conditions.

WINTER CONSTRUCTION

Construction during winter i s now an accepted

and

normal praciice in

much of Canada

2 2 ) .

Large building p r o j e c t s continue without

interruption.

This has been achieved by overcoming t r a d i t i o n , by developing

I

knowledge concerning t h e properties of materials a t low t'mptratures, evolving

i

methods of providing protection from cold weather, and dezonstrating t h a t i t i s

I

_{uneconomic t o shut down construction during winter.}

I

_{The ideal curing temperature f o r concrete i s about 13°C.}

The lower the

i

t e n p r r z t u r e ,

t h e

locg2r i t tzkes the c s n c r e i e t o a t t z i n i t s z a t z r e strength.

P r b t x t i o n i s t h e r e f o r e essential f ~ r

placins and curing

z t

~ ? \ G S

freezing

temperatures.

Concrete t h a t i s allowed t o f r e e z e a t an e l r l y stage may be

permanently damaged by crack f o n a t i o n r e s u l t i n g from pressures caused by the

formation of i c e .

Experience

a n d

observztion have shown

t h a t

tne temperaiure o f

concrete must be kept above 0°C long enough

t o develop

z

coc2ressive strength

of

The temperature and t i m e r e q u i r e d t o develop adequate s t r e n g t h i n concrete depend on s e v e r a l f a c t o r s , i n c l u d i n g the mass and o r i g i n a l temperature of the p l a c e d m a t e r i a l , geometry o f t h e s t r u c t u r e , type o f cement and admixture, and r a t e of heat l o s s t o t h e environment. When concrete i s placed i n w i n t e r i t i s necessary t o c o n t r o l i t s temperature t o ensure a h i g h q u a l i t y product. Three common methods o f c o n t r o l a r e :

-

s u i t a b l e c o v e r i ng p l us i n s u l a t i on,

-

s u i t a b l e e n c l o s u r e p l u s i n s u l a t i o n ,

-

s u i t a b l e e n c l o s u r e p l u s supplementary heat.

One o f t h e e a r l i e s t recorded uses o f an enclosure i n Canada was f o r a p r o j e c t i n Montreal i n 1928, b u t o n l y a f t e r 1945 d i d t h i s method o f p r o t e c t i o n become common. Enclosures may be c o n s t r u c t e d o f p l a s t i c sheet, t a r p a u l i n , plywood o r b u i l d i n g board.

The t e c h n o l o ~ y fo r p l a c i n g c o n c r e t e i n w i n t e r i s now w e l l developed and a p a r t o f r e g u l a r p r a c t i c e . It has been sum,arized r e c e n t l y i n a pub1 i c a t i o n prepared under t h e auspices o f t h e Canadian Committee on B u i l d i n g

~ e s e a r c h ( 3 ) .

Masonry c o n s t r u c t i o n ( b r i c k w o r k ) can a l s o be c z r r i e d o u t y e a r round. Masons o f t e n work w i t h o u t p r o t e c t i o n n e a t

0°C

u s i n g techniques t h a t i n c l u d e w a n mortar and d r y masonry u n i t s . Heated e n c l o s u r l s a r e used a t lower temperatures.

AS w i t h c o n c r e t e , i t i s a b s o l u t e l y e s s e n i i a l t o prevent f r e e z i n g u n t i l adequzte s t r e n g t h has developed. S t r u c t u r a l s t e e l may be e r z c t e d i n a l l b u t t h e most severe weather. Enclosures can be a t t a c h e d t o the framework t o p r o v i d e s h e l t e r

Working i n w i n t e r r e q u i r e s c a r e f u l p l a n n i n g , proper equi pment, experience and c i i p a b l e s u p e r v i s i o n . The d e c i s i o n t o do so f o r a p a r t i c u l a r c o n s t r u c t i o n p r o j e c t i s now p r i m a r i l y one o f economics. I n maki.ng t h i s d e c i s i o r one must t a k e i n t o account n o t o n l y t h e additional c o s t o f p r o t e c t i o n b u t a l s o t h e savings t h a t r e s u l t from u n i n t e r r u p t e d schedules, reduced c o n s t r u c t i o n time and g r e a t e r c o n t r o l o v e r t h e c o n d i t i o n s o f work such as p l a c i n g , f i n i s h i n g and c u r i n g o f c o n c r e t e .

FROST ACTION

One o f t h e m a j o r problems i n c o l d r e c i o n s i s damage due t o f r e e z i n g . This occurs p r i m a r i l y because o f w a t e r i n porous m a t e r i a l s . As p o i n t e d o u t f o r concrete and masonry, f r e e z i n g o f w a t e r w i t h i n such m a t e r i a l s nay cause c r a c k i n g

if t h e r e i s n o t s u f f i c i e n t s t r e n g t h t o w i t h s t a n d i t . One o f t h e most common problems i s t h e h e a v i n g o f s o i l due t o f o r m a t i o n o f i c e 1 enses through a process c a l l e d f r o s t a c t i o n ( 4 ) .

The e f f e c t s o f f r o s t a c t i o n a r e widespread and have been s t u d i e d f o r many years i n most c o l d r e g i o n s o f t h e world. They must be g i v e n c a r e f u l c o n s i d e r a t i o n i n t h e p r o v i s i o n o f w a t e r and sewage s e r v i c e s , c o n s t r u c t i o n of foundations, and i n t h e d e s i s n and use o f unkzated b u i l d i n g s , c o l d s t o r a g e ? l a n t s and i c e r i n k s . Thres c s n d i i i o n s must be s a t i s f i e d f o r f r o s t 8 c t i o n t o cccur: t h e s o i l o r o t h s r porous n s i e r i a l must be " f r o s t - s u s c e ? t f b l e , " water must be present, and f r e e z i n g must occur. When t 5 e t h r e e c o n d i t i o n s are s a t i s f i e d the e f f e c t can be v e r y s e r i o g s . Heaving pressures o f over 1800 kPa have been measured, a seven-storey r e i n f o r c e d c o n c r e t e frame b u i l d i n g has been observed t o heave more t h a n 50 mrn, and ground heaving as h i g h as 60 cn has Seen r e p o r t e d .

Experience and l a b o r a t o r y t e s t i n g have now l a r g e l y d e f i n e d t h e i m p o r t a n t c h a r a c t e r i s t i c s o f f r o s t - s u s c e p t i b l e m a t e r i a l s and t h e s t e p s t h a t should be taken t o p r e v e n t f r o s t a c t i o n .

A c o r r e l a t i o n has been found between t h e d e p t h o f f r o s t p e n e t r a t i o n and a measure o f c o l d c a l l e d t h e F r e e z i n g Index. The F r e e z i n g Index. i s t h e

accumulation o f degree days o f f r e e z i n g f o r a g i v e n w i n t e r ( i f t h e d a i l y mean temperature i s -4"C, t h i s w i l l add t o t h e i n d e x 4 C degree-days). F i g u r e 2 p r e s e n t s t h e f r e e z i n g i n d e x map f o r Canada. The i n d e x v a r i e s f r o m l e s s t h a n 55 C degree-days i n s o u t h e r n B r i t i s h Columbi a t o 4150 C degree-days i n n o r t h e r n Manitoba and Quebec t o 7750 C degree-days i n t h e H i g h A r c t i c .

The normal method o f p r e v e n t i n g f r o s t a c t i o n damage t o f o u n d a t i o n s and m u n i c i p a l s e r v i c e s i s t o p l a c e them b e l o w t h e expected d e p t h o f f r e e z i n g o f t h e ground. Most c i t i e s and towns i n Canada now have good r e c o r d s o f t h i s depth.

I n some cases i t i s more economical t o r e p l a c e f r o s t s u s c e p t i b l e s o i l s w i t h c o a r s e r m a t e r i a l s . I n a l l cases s t e p s a r e t a k e n , i f p o s s i b l e , t o p r o v i d e good d r z i n a g c and t h e r e b y m i n i a i i z e t h e s u p p l y o f w a t e r ( s S 6 ) .

Another method o f p r e v e n t i n g damaging f r o s t a c t i o n i s t n r o u g h t h e use o f i n s u l a t i o n . T h i s has been a p p l i e d , f o r example, f o r roadways and f o u n d a t i o n s . There i s now a good c a p a b i l i t y f o r c a l c u l a t i n g ground t e m p e r a t u r e s f o r v e r y ~ e n s r a l boundary c o n d i t i o o s u s i n g t h e c o s p u t e r ( 7 ) . T h i s 21 lows g r e a t e r

f l e x i b i l i t y i n c h o o s i n g t h e most ecanoniical s o l u t i o n d u r i n g t h e d e s i g n s:?.ge o f

a p r o j e c t . Such c a l c u l a t i o n s a r e p a r t i c u l a r l y i m p o r t a n t f o r s t r u c t u r e s such as c o l d s t o r a g e p l a n t s and s k a t i n g r i n k s t h a t s u b j e c t t h e ground t o b e l o w - f r e e z i n g t e m p e r a t u r e s . f o r l o n g p e r i o d s o f t i m e ( 8 ) .

I m p r o p e r l y made c o n c r e t e and b r i c k can s u f f e r s e r i o u s f r o s t damage i f n o t p r o t e c t e d f r o m w a t e r . Technology e x i s t s f o r t h e making o f h i g h l y f r o s t - r e s i s t a n t c o n c r e t e ( 3 ) and f o r d e t e r m i n i n g and c o n t r o l 1 i ng t h e f r o s t

s u s c e p t i b i l i t y of masonry u n i t s . P r o b a b l y t h e b e s t p r o t e c t i o n i s t o have adequate d r a i n a g e and b a r r i e r s t o e n s u r e t h a t w a t e r w i l l n o t r e a c h o r s t a y i n c o n t a c t w i t h m a t e r i a l s t h a t can s u f f e r damage from f r o s t a c t i o n .

A s e r i o u s p r o b l e m i n some a r e a s i s t h e d e t e r i o r a t i o n o f c o n c r e t e b r i d g e decks and p a r k i n g g a r a g e s ( 9 , l 0 ) . It i s now r e c o g n i z e d as due t o t h e more

severe f r o s t a c t i o n c o n d i t i o n s imposed by t h e use o f s a l t f o r snow removal and i c e c o n t r o l on r o a d s u r f a c e s . It i s a g g r a v a t e d by t h e c o r r o s i v e a c t i o n o f t h e chemicals on t h e r e i n f o r c i n g s t e e l . Damage can be g r e a t l y reduced by use o f epoxy-coated s t e e l and l o w water-cement r a t i o c o n c r e t e , w a t e r p r o o f i n g , and good drainage. The p r o b l e m i s d i f f i c u l t , e x p e n s i v e t o s o l v e , and t h e s u b j e c t o f much

c u r r e n t research.

The mechanism o f f r o s t a c t i o n has n o t y e t been f u l l y e x p l a i n e d and

I

research c o n t i n u e s . I n a d d i t i o n , c o n s i d e r a b l e e f f o r t i s b e i n g devoted b y

1

_{r e s e a r c h groups t o t h e development o f models and computer programs t h a t w i l l}

I

i

p r e d i c t n o t o n l y t h e t e m p e r a t u r e chanpes b u t a l s o t h e amount o f heave f o r g i v e n

I

boundary c o n d i t i o n s . Such programs c o u l d be u s e f u l l y a p p l i e d i n t h e d e s i g n o f

I

f o u n d a t i o n s

,

w n i c i p a l s e r v i c e s and co:d gas p i p e 1 i n e r .

ENERGY EFFICIENT BUILDINGS

The development o f t h e techno1 ogy f o r c o n s t r u c t i o n o f energy e f f i c i e n t

O r low energy b u i l d i n g s has Seen a h i ~ h p r i o r i t y s i n c e t h e p r i c e o f energy began

t o i n c r e a s e r a p i d l y . The approach t h a t i s t z k e n depends on t h e t y p e o f

b u i l d i n g , b u t t h e r e a r e s e v e r a l measures o f c o n t r o l l i n g t h e r a t e o f h e a t l o s s t h a t a r e common i o a l l .

The v a l u e o f p l a c i n g i n s u l a t i o n i n e x t e r i o r w a l l s t o reduce t h e r a t e o f heat l o s s was demonstrated by researchers b e f o r e 1930. I n s u l a t i o n , however, caused t h e o u t s i d e o f t h e w a l l t o be a p p r e c i a b l y c o l d e r than t h e i n s i d e .

Condensation t h a t formed a t times on t h e c o l d e r s u r f a c e caused d e t e r i o r a t i o n of t h e w a l l m a t e r i a l s and o t h e r damage. It was found t h a t t h i s c o u l d be c o n t r o l l e d by p l a c i n g a vapour b a r r i e r on t h e warn s i d e o f t h e w a l l and making p r o v i s i o n

f o r t h e escape o f w a t e r vapour on t h e c o l d s i d e - Use o f double glazed windows became standard i n a l l b u t t h e warmest r e g i o n s o f Canada. Caulking and weather s t r i p p i n g were found necessary t o reduce a i r leakage. By t h e 1960's t h e

techno1 o g f o r b u i l d i n g c o m f o r t a b l e b u i l d i n g s t h a t c o u l d be heated economical l y i n w i n t e r was w e l l e s t a b l i s h e d .

The e n e r g c r i s i s has changed t h i s . Increase i n t h e c o s t of energy and t h e need t o reduce o i l consumption has r e s u l t e d .in major research programs d i r e c t e d t o r e d u c i n g f u r t h e r t h e energy requirements of b u i l d i n g s and t o

developing a1 t e r n a t i v e e n e r v sources. For l a r g e b u i l d i n g s a t t e n t i o n i s b e i n g given, f o r example, t c o p t i m i z i n g t h e d e s i g n and performance o f the h e a t i n g and v e n t i l a t i o n systems, r e d u c i n g the e n e r g consumption o f l i g h t i n g , improving t h e a i r t i g h t n e s s o f e x t e r i o r w a l l s , and d e v e l o p i n g methods o f s t o r i n g heat d u r i n g warm p e r i o d s f o r use d u r i n g c o l d ones. E n e r g measures have b e ~ n

re oared

f o r

cse on a v o l u n t a r y b a s i s ( l 1 ) . They hz.:~ hzc! a s i 9 n i f i c a n t i z p a r t on the Gesian and o p e r a t i o n o f b u i l d i n g s . Huch a t t z n t i o n i s a l s o b2ing g i v e n t o

developing t h e c a p a b i l i t y t o analyse t h e energy requirements and performance o f a b u i l d i n g by computer(12). This i n c l u d e s compi 1 i n g weather and c l i m a t e

Very s i g n i f i c a n t advances have been made i n the development o f "low energy" homes(13). These have been a s s o c i a t z d w i t h wood frame c o n s t r u c t i o n t h a t i s t y p i c a l o f houses i n Canada. Techniques have been developed f o r

-

c o n s t r u c t i n g w a l l s 30 cm t h i c k o r more w i t h i n s u l a t i o n r a t i n g s i n excess o f

ti ha/&

6

m.

Such t h i c k n e s s e s are p r o b a b l y g r ~ a t e r t h a n a r e econoinical l y j u s t i f i e d except f o r v e r y c o l d r e g i o n s . ~ r i ? l e - o r even quadrupl e-gl azed

windows a r e used and s p e c i a l a t t e n t i o n i s g i v e n t o p r o v i d i n g an " a i r b a r r i e r " t o reduce a i r leakage. V e n t i l a t i o n must be p r o v i d e d f o r such t i g h t houses i n o r d e r t o keep t h e h u m i d i t y a t a reasonable l e v e l , remove odours o f cooking, smoking, etc., and m a i n t a i n good a i r q u a l i t y . T h i s , i n t u r n , has brought about t h e need f o r heat exchangers t o recover t h e h e a t from t h e a i r t h a t

i s

exhausted.

I n t r o d u c i n g enemy-conserving measures has brought problems t h a t were under reasonable c o n t r o l f o r i h e c o n s t r u c t i o n p r a c t i c e o f t h e 1960's. Making b u i l d i n g s more a i r t i g h t p o t e n t i a l l y aggravates problems caused by rnoi s t u r e i n t h e i n t e r i o r and w i t h i n w a l l and o t h e r spaces o f t h e e x t e r i o r envelope. It has a l s o made t h e q u e s t i o n o f a i r q u a l i t y a p r i o r i t y issue. Research i s under way t o e s t a b l i s h t h e t e c h n o l o g , c o n s t r u c t i o n p r z c t i c e and methods o f h e a r i n g t h a t a r e a p p r o p r i a t e f o r t h e new c o n d i t i o n s . Research and development i s i n progress on h i g h e f f i c i e n c y gas h e a t e r s , h e a t pumps uszd a l o n e o r i n combination w i t h c t h e r h e a t sources, e l e c t r i c a l h e a t i n g s y s t e c s , wind-powlred gen?rators, and s o l a r h e a t i n g systezts.

NORTHERN CONSTRUCTION

For most Canadians c o l d r e g i o n s a r e i d e n t i f i e d w i t h the Sarth. A r e c e n t study d e f i n e d c o l d r e g i o n s as t h a t area n o r t k o f t h e southsrn l i z i i t o f t h e

temperatures i n w i n t e r a r e n o t t o o d i f f e r e n t f r o m t h o s e i n t h e c e n t r a l p a r t o f t h e c o u n t r y , b u t t h e p e r i o d o f c o l d i s l o n g e r and t h e r e i s l i t t l e o r no

sun1 i g h t . P o p u l a t i o n d e n s i t i e s a r e l o w , s e t t l e m e n t s a r e remote, m a t e r i a l s may

be d i f f i c u l t t o o b t a i n and t r a n s p o r t a t i o n c o s t s a r e high.

The t e r m p e r m a f r o s t r e f e r s t o any m a t e r i a l

-

whether sand, g r a v e l , s i 1 t ,

c l a y , p e a t o r b e d r o c k

-

t h a t i s a t a t e m p e r a t u r e o f l e s s t h a n

0°C

f o r more t h a n one y e a r . I t s o c c u r r e n c e depends n o t o n l y on c l i m a t e b u t a l s o on t h e n a t u r e o f t h e t e r r a i n , i n c l u d i n g s u r f a c e c o n d i t i o n s and t h e r m a l p r o p e r t i e s o f t h e ground. P r e d i c t i o n o f i t s d i s t r i b u t i o n , t h i c k n e s s , t e m p e r a t u r e , i c e c o n t e n t and o t h e r p r o p e r t i e s i s d i f f i c u l t because o f t h e complex i n t e r a c t i o n o f t h e f a c t o r s t h a t a f f e c t i t , such as a i r t e m p e r a t u r e , v e g e t a t i o n , s u r f a c e r e 1 i e i , d r a i n a g e , snow

c o v e r and t y p e o f s o i l . Development o f knowledge c o n c e r n i n g t h e r e l a t i o n s

between t h e s e f a c t o r s and t h e p e m a f r o s t c o n c i t i ons i s i m p o r t ~ n t fo r e n g i n e e r i n g

a c t i v i t y .

A t t h e s u r f a c e o f p e r m a f r o s t t h e r e i s a l a y e r o f s o i l o r rock, c a l l e d

t h e a c t i v e l a y e r , t h a t thaws e v e r y summer. I t s t h i c k n e s s nay v a r y from one'or

more metres i n t h e d i s c o n t i n u o u s zone t o o n l y a few c e n t i ~ e t r e s i n t h e High

A r c t i c . The t h i c k n e s s a l s o v a r i e s l o c a l l y degending on f a c t o r s such as

v e g e t a t i o n , s u r f a c e r e 1 i e f , ground t h e r m a l p r ~ p e r t i e s and drainage. Permafrost

normai l y h3s r o c k - 1 i k e qua1 i t i e s . T h i s c h a r ~ i t e r i s t i c f o r ~ r a n u : a r m a t e r i a l s i s

-

-

due t o t h e c e m e n t i n g a c t i o n o f t h e i c e . It i s n o t uncoracn f o r ;:ne-grained

s 0 i 1

,

such as c l a y s and s i l t s

,

and p o o r l y d r a i n e d sands and g r a v e l s , t o have i c e

c o n t e n t s s e v e r a l t i m e s l a r g e r t h a n t h e e q u i l i b r i u m water c o n t e n t i n t h e thawed

c o n d i t i o n . I n g e n e r a l

,

t h e s t r e n g t h o f p e n z f r o s t i n c r e a s g s w i t h i n c r e z s i n g i c e

c o n t e n t and d e c r e a s i n g t e m p e r a t u r e . F r o z e n sznds t h a t a r e w e l l czmented by i c e

Permafrost i s s e n s i t i v e t o changes i n t h e thermal c o n d i t i o n s a t the

surface. Disturbance o f an area due t o v e h i c l e t r a f f i c o r c l e a r i n g f o r a

s t r u c t u r e may r e s u l t i n g r e a t l y increased t h i c k n e s s o f t h e a c t i v e l a y e r o r

complete thawing o f t h e ground. S o i l s w i t h h i g h i c e c o n t e n t may l o s e s t r e n g t h

t o such an e x t e n t t h a t they cannot support even l i g h t loads. Experience has

shown t h a t i f p e r m a f r o s t w i t h s i g n i f i c a n t i c e c o n t e n t i s t o support loads

s u c c e s s f u l l y i t must be k e p t i n the f r o z e n s t z t e .

Much knowledge now e x i s t s on how t o b u i l d i n permafrost regions, and

has r e c e n t l y been summarized i n two comprehensive books(15,16). The f i r s t

step i s c a r e f u l s e l e c t i o n o f t r a f f i c r o u t e s and b u i l d i n g s i t e s i n order t o avoid

t o t h e g r e a t e s t p o s s i b l e e x t e n t i c e r i c h ground. Research i s i n progress t o

develop methods of, d e l i n e a t i n g permafrost and d e t e r m i n i n g i c e contents

economically u s i n g remote sensing methods. Mzny p r o j e c t s r e l y , however, on t h e

t r a d i t i o n a l method o f d r i 11 i ng and sampl i ng.

Permafrost can pose s e r i o u s p r o b l ems f o r c o n s t r u c t i o n , a1 though i t can be neglected when s t r u c t u r e s a r e b u i l t on w e l i - d r a i n e d g r a n u l a r s o i l s o r rock. For these c o n d i t i o n s c o n v e n t i o n a l d e s i g n and c o n s t r u c t i o n methods are p o s s i b l e .

For s o i l s o f s i g n i f i c a n t i c e c o n t e n t , t h e f r o z z n c o n d i t i o n can be preserved

by

c o n s t r u c t i n g on a g r a n u l a r , w e l l - d r a i n e d

fill

o f s u f f i c i e n t thickness; by u s i n g

a v e n t i l a t e d f i l l o r i n s u l a t i o n ; o r by p i a c i n a t h e s t r u c t u r e on p i l e s . I n t h e

l a t t e r case i t i s necessary t o keep t h e space j e n e a t h the s t r u c t u r e open i n w i n t e r so t h a t t h e ground can cool and remain frozen.

I

I f

t h e s o i l s c o n t a i n excessive i c e and i t i s n o t p o s s i b l e t o preserve

the frozen c o n d i t i o n , i t may be ccnvenient t o thaw and c o n s o l i d z t ? t h e ground

before c o n s t r u c t i o n begins. For some s i c u a t i c n s i t may be economical t o remove

t h e p e r m a f r o s t c o m p l e t e l y and r e p l a c e i t w i t h w e l l - d r a i n e d g r a n u l a r m a t e r i a l . I n o t h e r cases i t may be necessary t o t a k e i n t o account a n t i c i p a t e d s e t t l e m e n t d u r i n g thawing, f o r example, b y u s i n g f l e x i b l e f o u n d a t i o n s o r a d j u s t a b l e

supports.

Methods have now been developed f o r d e t e r m i n i n g a n a l y t i c a l l y o r w i t h t h e computer t h e amount o f p r o t e c t i o n t h a t must be p r o v i d e d by g r a n u l a r f i l l s ,

i n s u l a t i o n , o r v e n t i 1 a t i o n t o keep t h e p e r m a f r o s t from thawing. The p a r t i c u l a r method t h a t i s chosen w i l l be d e t e r m i n e d by c c s t and i s a f f e c t e d by f a c t o r s such as t y p e of s t r u c t u r e , t e m p e r a t u r e o f t h e ground, t y p e o f s o i l and a v a i i a b i l i t y o f g r a n u l a r m a t e r i a1 s.

Probably t h e most d i f f i c u l t s t r u c t u r e s t o b u i l d and m a i n t a i n on permafrost a r e highways and p i p e l i n e s , f o r i t i s u s u a l l y i m p o s s i b l e t o a v o i d i c e - r i c h ground and s e v e r e d i s t u r b a n c e d u r i n g c o n s t r u c t i o n . Careful a t t e n t i o n must be g i v e n t o d r a i n a g e . No m a j o r p i p e l i n e s have been c o n s t r u c t e d i n t h e n o r t h o f Canada, b u t s e v e r a l roads have been b u i l t o v e r permafrost.

Care must

b e

t a k e n t o a v o i d t h e e f f e c t s o f f r o s t a c t i o n i n t h e a c t i v e l a y e r . l l i s l a y e r o f t e n c o n s i s t s o f f r o s t s u s c e p t i b l e s o i l s w i t h h i g h w a t e r c o n t e n t because o f p o o r d r a i n a g e . D i f f e r e n t i a l h e a v i n g d u r i n g r e f r e e z i n g can be p a r t i c u l a r l y damaging t o f o u n d z t i o n s and m u n i c i p a l s e r v i c e s . M t h e p r ~ s e n t t i n e r e s z z r c h i s i n p r s s r e s s on t h e s t r ? n g r h and t i e f o r n a t i o n p r o p e r t i e s o f f r o z e n s o i l s , t h e s;:ndaraization o f methods f o r measuring t h e s e p r o p e r t i e s , development o f a r c i i o n a l f r o z e n ground

t e c h n i q u e s f o r m e a s u r i n g t h e p r o p e r t i e s o f p e m a f r o s t i n s i tu . O b s e r v a t i o n s a r e b e i n g made on t h e p e r f o r m a n c e o f p i l e - s u p p o r t e d s t r u c t u r e s , highway f i l l s ,

b r i d g e f o u n d a t i o n s , a m a j o r a i r s t r i p , and i n s u l a t e d highway s e c t i o n s . W o ~ k i s c o n t i n u i n g on t h e d e t e r m i n a t i o n o f t h e d i s t r i b u t i o n o f p e r m a f r o s t , i t s d e p t h and t e m p e r a t u r e , and f a c t o r s t h a t c o n t r o l i t s o c c u r r e n c e and d e g r a d a t i o n . Research i s c a r r i e d o u t b y s e v e r a l o r g a n i z a t i o n s b o t h i n t h e l a b o r a t o r y and i n t h e

f i e l d .

WINTER ROADS AND I C E PLATFORMS

The c o l d o f w i n t e r p e r m i t s work t o be c a r r i e d o u t i n areas t h a t cannot be reached e a s i l y i n surruner by a e r o p l a n e s o r v ~ h i c l e s . Frozen ground, snow and i c e p r o v i d e t h e means b y w h i c h roads and a i r s t r i p s can be b u i l t t o b r i n g

m a t e r i a l i n o r o u t o f such p l a c e s .

The t e c h n o l o g y f o r b u i l d i n g w i n t e r r o a d s i s now w e l l

e s t a b l i s h e d ( l 7 ) and more advanced t h a n i s u s u a l l y r e q u i r e d i n p r a c t i c e .

Simple t e c h n i q u e s o f compaction, perhaps augmenied by f l o o d i n g w i t h w a t e r , a r e adequate f o r roads t h a t can be used t o remove wood f r o m f o r e s t s o r t r a n s p o r t goods t o remote s i t e s . More s o p h i s t i c a t e d methods have been developed, b u t t h e y a r e n o t economical f o r g e n e r a l use.

I c e c o v e r s have

ions

p r o v i d e d a means

cf

c r o s s i n g l z k e s and r i v e r s i n w i n t e r . They a r e now used r o u t i n e l y as b r i d g e s f o r normal highway t r a f f i c , as p l a t f o r m s f o r a c t i v i t y such as e r e c t i n g b r i d g e s o r d r i l l i n g , and as a i r s t r i p s f o r c a r g o - c a r r i e r s and o t h e r a i r c r a f t . Lzkes and r i v e r s a r e o f t e n used as t h e l o c a t i o n f o r w i n i e r r o a d s i n o r d e r t o reduce t k 2 amount o f p r e ? a r z t o r y work r ~ q u i r e d , p a r t i c u l a r l y i n wooded and h i l l y r e g i o n s .

The d e s i g n o f i c e c r o s s i n g s and p l a t f o r m s i s e s s e n t i a l l y e m p i r i c a l . Observations o f f a i l u r e s and o f t h e s u c c e s s f u l use o f i c e covers have p r o v i d e d t h e b a s i s f o r d e t e r m i n i n g t h e t h i c k n e s s o f i c e necessary t o c a r r y a g i v e n l o a d

w i t h reasonable s a f e t y ( 1 8 ) . Theory has p r o v i d e d a framework i n which t o

analyse these o b s e r v a t i o n s and t o f o r m a l i z e t h e d e s i g n process. Manuals have

been produced f o r t h e use o f i c e covers by a i r c r a f t and s u r f a c e v e h i c l e s ( l 9 , 2 0 ) .

I c e covers a r e n o r m a l l y a t a temperature c l o s e t o t h e i r m e l t i n g p o i n t . The v a r i a t i o n s o f n a t u r e i n t r o d u c e i n t o them inhomogeneities such as cracks,

u n f r o z e n l a y e r s , and t h i n s p o t s due t o warm c u r r e n t s . Temperature changes and

wind can induce i n t e r n a l s t r e s s . These e f f e c t s a r e 1 a r g e l y u n p r e d i c t a b l e and

t h e r e f o r e g r e a t c a r e must be t a k e n i n c o n s t r u c t i n g i c e crossings and p l a t f o r m s , i n m o n i t o r i n g t h e i r c o n d i t i o n d u r i n g use, and i n c o n t r o l l i n g the l o a d s and

t r a f f i c p l a c e d on them. Records o f f a i l u r e s i n d i c a t e t h a t most occur because of

l a r g e l y u n c o n t r o l l a b l e f a c t o r s such as t h i n s p o t s , cracks, and t h e m a l s t r e s s . One o f t h e g r e a t e s t e n g i n e e r i n g achievements i n t h e H i g h A r c t i c has been t h e c o n s t r u c t i o n of l a r g e i c e p l a t f o r m s f o r s u p p o r t i n g d r i l l i n g

operations(21). Loads have been i n excess o f 1600 m e t r i c tonnes. The

t h i c k n e s s of i c e r e q u i r e d t o c a r r y such l o a d s i s o b t a i n e d by w e l l d2veloped

f l o o d i n g procedures. The c r i t e r i o n used t o ensure s z f e p e r f o r ~ a n c e i s t h a t t h e

maximum d e f l e c t i o n und2r t h e l o a d must n o t exceed t h e t h i c k n e s s o f i c e above t h e

n a t u r a l water l e v e l f o r t h e unloaded c o n d i t i o n . T h e o r e t i c a l c a l c u l a t i o n s and

l a b o r a t o r y s t u d i e s have shown t h a t i f t h i s c o n d i t i o n i s maintained, t h e s t r e s s e s

I c e p l a t f o r m s f o r d r i l l i n g must be l o c a t e d i n l a n d - f a s t i c e so t h a t they

w i l l not move t o o much d u r i n g use, D r i l l i n g has been c a r r i e d out i n waters up

t o 400 m deep. The t i m e taken t o prepare t h e p l a t f o r m and m e l t i n g i n s p r i n g

l i m i t t h e i r p e r i o d o f use t o about t h r e e months.

OFFSHORE STRUCTURES

Great a t t e n t i o n i s b e i n g given t o t h e development o f o f f s h o r e s t r u c t u r e s

f o r petroleum e x p l o r a t i o n and p r o d u c t i o n . The d e s i g n and performance o f such

s t r u c t u r e s has now been r e 1 a t i v e l y we1 1 e s t a b l i s h e d f o r non-ice-affected waters. For both the A t l a n t i c and A r c t i c Ocean r e g i o n s o f Canada c o n s i d e r a i i o n must be given t o e f f e c t s o f i c e .

Icebergs a r e a major problem i n t h e arezs now being explored i n t h e

A t l a n t i c . The o n l y p o s s i b l e a c t i o n f o r i c e b e r g s i s avoidance. This can be

accomplished e i t h e r by moving t h e d r i l l i n g p l a t f o r m s o r by towing t h e iceberg. Considerable work has been done on d e t e c t i n g and t r a c k i n g icebergs and on e s t a b l i s h i n g t h e procedures and c o n d i t i o n s f o r towing.

1

Ice c o n d i t i o n s i n t h e A r c t i c are q u i t e d i f f e r e n t . Offshore s t r u c t u r e s

i n the A r c t i c Ocean w i l l be surrounded by c o n t i n u o u s l z n d - f a s t i c e o r the moving

A r c t i c pack. To date, b u i l t - u p i s l a n d s o f granti:ar m a z e r i a l have been used

s u c c e s s f u l l y i n t h e Beaufort Sea i n r e l a t i v e l y s h a l l o w water near shore. The

shore c o n s t r a i n s the i c e cover so t h a t i t does n a t move much r e l a t i v e t o t h e

i s l a n d once i t has reached a t h i c k n e s s of about LO

cm.

S a t i s f a c t o r y methods of

Drilling a c t i v i t y now extends out t o a mean water depth of about 20 m ,

which i s near the l i m i t

o f

the land f a s t i c e condition.

The f i r s t island t o be

exposed t o the moving Arctic pack was constructed in 1981.

I t consisted of a n

underwater berm on which were placed l a r g e concrete caissons

t o

form an

octagonal s t r u c t u r e extending about

5

m

above the water surface.

The development of offshore s t r u c t u r e s has been guided by analytical

studies and model s t u d i e s in the laboratory.

Design c r i t e r i a f o r conditions

imposed by ice covers can only be properly established and demonstrated

t o

be

c o r r e c t , however, by prototypes of a s i z e comparable t o those t h a t will be used

in practice.

Building such s t r u c t u r e s in r e a l i s t i c ice conditions i s expensive

and will be done only i f there i s a resource development or other need t h a t

j u s t i f i e s the expenditure.

For the caisson-protected island constructed in

1981

i t was possible t o conduct not only an extensive ice force measurement

program

b u t

t o

use the island f o r exploratory d r i l l ing as we1 1 .

This project

has provided considerable information concerning the nature of the interaction

t h a t w i 11 occur between s t r u c t u r e s and the moving Arctic pack i c e .

I t will

give useful guidance f o r the design and operation of future systems. Through

such a c t i v i t y the l i m i t s f o r s a f e operations in the h o s t i l e environment of the

Arctic seas will gradually be defined.

SNOW

DRIFTING

Drifting snow cannot

b e

avoided-in most regions of Cznada.

I t s e f f e c t s

can range from being of

no

consequenc? t o conpletely stcpping a i l travel or

access.

Snow accumulated in d r i f t s can be

a

useful source

of

water or may

a g g r a v a t e d r a i n a g e a n d g r o u n d s u r f a c e c o n d i t i o n s b e c a u s e o f t h e l o n g e r t i m e

i t

t a k e s t o m e l t i n s p r i n g .

I f d r i f t i n g snow

i s

e x c x t e d t o be a p r o b l e m ,

c o n s i d e r a t i o n s h o u l d b e g i v e n a t t h e d e s i g n s t a g e o f a p r o j e c t t o m i n i m i z i n g i t s

e f f e c t s ( 2 2 ) .

D r i f t s a r e f o r m e d f r o m f a l l i n g snow o r e r o s i o n o f d e p o s i t e d snow when

w i n d s p e e d s e x c e e d a b o u t 13 km.h-l.

The a m o u n t o f snow c a r r i e d by t h e wind

d e p e n d s upon t h e w i n d s p e e d , r a t e o f s n o w f a l l , e n d d i s t a n c e o f o p e n a r e a upwind.

Snow may b e d e p o s i t e d when t h e w i n d s p e e d

i s r e e u c e d o r i t s d i r e c t i o n c h a n g e d .

Snow d r i f t i n g c a n b e i n f l u e n c e d , t h e r e f o r e , by t h e s h a p e and o r i e n t a t i o n o f a

b u i l d i n g and by t h e u s e o f f e n c e s o r o t h e r m e a n s t o c h a n g e t h e s p e e d and

d i r e c t i o n o f t h e a i r f l ow.

E x p e r i e n c e a n d r e s e a r c h h a v e e s t a b l i s h e d t h e p r i n c i p l e s t o b e f o l l o w e d

t o m i n i m i z e t h e e f f e c t s o f snow.

I t

i s

n o t a l w a y s p o s s i b l e , h o w e v e r , t o f o l l o w

t h e m i n p r a c t i c e b e c a u s e o f t h e v a r i a b i l i t y o f t h e c o n d i t i o n s a s s o c i a t e d w i t h

d r i f t i n g snow a n d t h e l i m i t a t i o n s i m p o s e d by g r o u n d s u r f a c e c o n d i t i o n s a n d

e x i s t i n g s t r u c t u r e s .

A

m o s t i m p o r t a n t s t e p i n p l a n n i n g

i s t o e s t a b l i s h t h e

d i r e c t i o n o f t h e m a i n d r i f t - p r o d u c i n g w i n d s .

? s o l a t e d b u i l d i n g s s h o u l d b e

o r i e n t e d s o t h a t t h e i r l o n g d i r e c t i o n i s t h e s a n e .

Groups o f b u i l d i n g s s h o u l d

'be p l a c e d i n rows w i t h t h e i r l o n g d i r e c t i o n p z r a l l e l t o t h a t o f t h e

d r i

f

t - p r o d u c i n g w i n d s .

Roads a n d b u i

1

d i n g e n t r a n c e s s h o u l d b e a 1 ong t h e

1

o n g

s i d e o f t h e b u i l d i n g s i n c e t h i s a r e a h a s t h e

rea ate st

p r o b a b i l i t y o f b e i n g f r e e

o f snow.

I n some s i t u a t i o n s

i t

n a y b e z p p r o o r i a t e t o p l a c e t h e s t r u c t u r e on

p i l e s and a l l o w t h e snow t o p a s s t h r o u g n t h e s p e n a r e a u n d z r n ~ a t h , a m e t h o d

t h a t

i s

common i n t h e A r c t i c w h e r e snow d r i f t i n g c E n b e s e r i o u s .

Snow d r i f t i n g can be reduced by t h e u s e of b a r r i e r s and by minimizing

t h e p l a c e s where

i t

c a n a c c u m u l a t e .

The b a s i s f o r t h e d e s i g n o f snow f e n c e s

i s

now well e s t a b l i s h e d .

What

i s r e q u i r e d i s t h e a b i l i t y t o r e c o g n i z e where t h e y

can be used i n p r a c t i c e and t o d e m o n s t r a t e t h e i r e f f e c t i v e n e s s .

E x p e r i e n c e i n

t h e c o n s t r u c t i o n and m a i n t e n a n c e o f r o a d s h a s shown how t h e e f f e c t s o f snow can

be minimized by p r o p e r o r i e n t a t i o n , e l e v a t i o n of t h e s u r f a c e above t h e

s u r r o u n d i n g t e r r a i n , and d e s i g n and p l a c e m e n t o f road c u t s and f i l l s s o t h a t

t h e y do n o t a c t a s snow t r a p s . When p o s s i b l e , b u i l d i n g s , a c c e s s r o a d s and

p a r k i n g a r e a s s h o u l d be l o c a t e d a t t h e t o p o f exposed h i l l s . E l e v a t i n g a road 1

t o 2 m above t h e s u r r o u n d i n g ground and a v o i d i n g d e p r e s s i o n s , c u t s , and t h e l e e

s i d e of h i l l s can g r e a t l y r e d u c e snow p r o b l e m .

In complex s i t u a t i o n s where

i r r e g u l a r c o n d i t i o n s a r e p r e s e n t , u s e f u l g u i d a n c e can be o b t a i n e d from model

t e s t s i n a wind t u n n e l o r w a t e r flume.

Snow removal

i s a m a j o r e x p e n s e f o r most r e g i o n s of Canada.

The

e f f i c i e n c y o f snow plows f o r r o a d s d e p e n d s on t h e s h a p e o f t h e b l a d e and t h e

speed of plowing.

T h e r e a r e , however, e c o n o a i c and s a f e t y f a c t o r s t h a t l i m i t

t h e e f f i c i e n c y of snow removal.

I t

i s

done o n l y when r e q u i r e d 2nd u s u a l l y does

n o t j u s t i f y e x p e n d i t u r e on equipment d e d i c a t g d s o l e l y t o i t . Snow plows a r e

d e s i g n e d s o t h a t t h e y can be mounted on t r u c k s t h a t can be used f o r o t h e r

p u r p o s e s when n o t needed f o r snow removal.

Speed o f plowing i s d e t e r m i n e d by

t h e c a p a b i l i t y of t h e v e h i c l e , v i s i b i l i t y , 2nd s a f e t y .

In r e s i d z n t i a l a r e a s , i n

p a r t i c u l a r , s p e e d must u s u a l l y be k e p t lower t h a n i s r e q u i r e d f o r p r o p e r c z s t i n g

of t h e snow.

Snow b l o w e r s a l s o a r e d e s i g n e d t o be mounted on m u l t i - p u r p o s e

v e h i c l e s .

When i t i s n e c e s s a r y t o t r a n s p o r t snow t o o t h e r l o c a t i o n s , t h i s i s

done p r i m a r i l y w i t h t r u c k s t h a t a r e n o r m a l l y used f o r h a u l i n g s a n d , g r a v e l

and o t h e r m a t e r i a l s . P r o b a b l y t h e g r e a t e s t savings i n snow removal can be o b t a i n e d n o t by i m p r o v i n g t h e e f f i c i e n c y and e f f e c t i v e n e s s o f t h e equipment b u t by p r o p e r and c a r e f u l management and c o n t r o l o f t h e a c t i v i t y ( 2 3 ) . Work i s r e q u i r e d t o d e f i n e more c l e a r l y t h e procedures and equipment t h a t should be used f o r g i v e n snow c o n d i t i o n s . T h i s i s p a r t i c u l a r l y t r u e f o r t h e use o f s a l t and sand i n p o s s i b l e c o m b i n a t i o n w i t h p l o w i n g and snow-melting systems f o r t h e c o n t r o l o f i c y c o n d i t i o n s ( 2 4 9 25).

SNON LOADS

Snow a c c u m u l a t i o n on t h e r o o f s o f b u i l d i n g s can cause c o l l a p s e , water and i c e damage, and snow s l i d e s . The s i z e o f t h e snow l o a d depends on s e v e r a l

f a c t o r s , i n c l u d i n g amount and t y p e o f s n o w f a l l , wind, temperature h i s t o r y , amount of sunshine, exposure, h e a t l o s s from t h e b u i l d i n g , and n a t u r e o f t h e s u r r o u n d i n g environment (26,27). Because o f t h e l a r g e v a r i a t i o n i n c l i m a t e i n Canada, snow l o a d s v a r y g r e a t l y and must be considered on a r e g i o n a l and l o c a l b a s i s . I n t h e A t l a n t i c and P a c i f i c Coast areas t h e r e a r e f r e q u e n t thaws c h a r a c t e r i z e d by snow a c c u m u l a t i o n s of s h o r t d u r a t i o n , o f t e n produced by one o r two snowstoms. The mountainous r e g i o n s have t h e g r e a t e s t snow depth and t h i s u s u a l l y l a s t s a l l w i n t e r . The c e n t r a l P r a i r i e r e g i o n and t h e N o r t h a r e

c h a r a c t e r i z e d by r e l a t i v l y l o w s n o w f a l l and f r e q u e n t winds, w i t h d r i f t i n g .

O n t a r i o and Quebec, f o r m i n g t h e C e n t r a l r e g i o n , have v a r y i n g winds and s n c w f a l l , and s u f f i c i e n t l y c o l d weather t o a l l o w snow t o accumulate f o r extended p e r i c d s o f time.

The amount o f snow t h a t accumulates on t h e ground d u r i n g a w i n t e r i s t h e b a s i s used f o r e s t i m a t i n g snow l o a d s . Table I p r e s e n t s values f o r some

Canadian towns and c i t i e s . These loads were determined from measurements of snow depth over many years.

Roof loads are equal t o ground loads o n l y if t h e r o o f i s completely p r o t e c t e d from t h e wind, if t h e r e i s no m e l t i n g and t h e r o o f slope i s n o t so steep as t o cause t h e snow t o s l i d e o f f . Observations have been made over t h e y e a r s t o show how these l o a d s should be m o d i f i e d t o t a k e i n t o account such

f a c t o r s as exposure t o wind, r o o f l e v e l o b s t r u c t i o n s , and t h e slope and shape of t h e roof. Factors r e c e i v i n g a t t e n t i o n a t p r e s e n t are t h e e f f e c t s of m u l t i - l e v e l r o o f s and o f surrounding b u i l d i n g s .

Snow l o a d requirements a r e s p e c i f i e d i n t h e National B u i l d i n g Code o f Canada, a document t h a t must be f o l l o w e d f o r t h e c o n s t r u c t i o n o f most b u i l d i n g s i n t h e country(28). These requirements a r e i n a c o n t i n u i n g s t a t e o f

devel opment and t h e i r a p p l i c a t i o n r e q u i r e s c a r e f u l , judgement. F o r roofs of more complicated shape i t may be necessary t o augment t h e i n f o r m a t i o n i n t h e Code w i t h a d d i t i o n a l sources o f i n f o r m a t i o n , wind t u n n e l o r water flume s t u d i e s , and

f i e l d observations i n o r d e r t o e s t a b l i s h t h e expected l o a d and i t s d i s t r i b u t i o n .

AVALANCHES

Avalanches pose problems p r i m a r i l y i n t h e mountainous regions of Canada, b u t damaging snow s l i d e s can occur i n o t h e r areas. Takinq steps t o prevent

them

i s c o s t l y and j u s t i f i e d o n l y i f t h e r e i s a l a r g e p o o u l a t i o n a r expensive

f a c i l i t i e s a t r i s k . This i s r a r e l y t h e case i n Canada. P r a c t i c e and research, t h e r e f o r e , i s focused on p r e d i c t i n g and m i n i m i z i n g the r i s k and on defence systems a g a i n s t moving snow.

The f i r s t s t e p i n a r e g i o n i n which work

i s

t o be c a r r i e d out o r

b u i l d i n g s a r e t o be b u i l t t h a t may be a f f e c t e d by avalanches i s t o i d e n t i f y and map t h e i r paths and t h e p r o b a b l e maximum e x t e n t of t h e i r motion. This should be

accompanied, i f p o s s i b l e , by c o r r e l a t i o n s between the c h a r a c t e r i s t i c s o f any avalanches t h a t may occur (e.g., s i z e , speed, mass and run o u t d i s t a n c e ) , t h e t e r r a i n (e.g., slope, l o c a t i o n and s i z e o f accumulation area) and t h e weather

(e-g., snowfall amounts and r a t e s , wind, temperature). Roads and b u i l d i n g s should be l o c a t e d t o a v o i d o r minimize t h e avalanche hazard.

For those cases where hazard cannot be e l i m i n a t e d , d e c i s i o n s must be made concerning t h e need f o r and t y p e o f defence. Defence methods i n c l u d e sheds t o c a r r y t h e snow over roads o r r a i l w a y s , d e f l e c t o r s , dams and d i v e r t i n g

channels. Explosives o r gun f i r e can be used t o t r i g g e r avalanches before they reach a dangerous s i z e . People can be evacuated and highways closed d u r i n g dangerous p e r i o d s . The t y p e o f defence method o r combination o f methods chosen w i l l depend on c o s t and t h e n a t u r e o f t h e p r o j e c t ( 2 9 ) .

The n a t u r e o f t h e avalanche hazard i s s t r o n g l y determined by r e g i o n a l and l o c a l f a c t o r s ,

If

t h e chosen avalanche defence system depends o n . a c t i o n taken i n a n t i c i p a t i o n of o r a t t h e t i m e of danger, i t i s e s s e n t i a l t h a t t h e r e be a c o n t i n u i n g program of o b s e r v a t i o n of weather and snow c o n d i t i o n s . The

i n f o r m a t i o n o b t a i n e d p r o v i d e s t h e b a s i s f o r e s t i m a t i n g and p r e d i c t i n g t h e avalanche hazard and subsequent a c t i o n . Work i s i n progress i n several c c u n t r i e s on i m p r o v i n g t h e c a p a b i l i t y t o e v a l u a t e avalanche hzzzrd 2nd on

developing t h e knowledge r e q u i r e d f o r t h e c h o i c e and design o f avalanche defence systems.

RESEARCH NEEDS

I n addressing t h i s s u b j e c t t h e r e must be a c l e a r understanding o f what i s meant by c o l d regions. It has been d e f i n e d f o r t h i s conference as t h e area n o r t h o f 40 degrees l a t i t u d e . That i n c l u d e s a l l o f Canada. Most Canadion>, however, do n o t c o n s i d e r t h e p l a c e i n which they l i v e as a " c o l d region" w i t h respect t o e n g i n e e r i n g and development work. That term i s u s u a l l y a p p l i e d only t o t h e n o r t h e r n p a r t o f t h e c o u n t r y , t h e area most a f f e c t e d by long periods o f c o l d and permafrost.

Using t h e broader d e f i n i t i o n and addressing f i r s t the southern, more populated r e g i o n , i t can be s t a t e d i n general t h a t a r e l a t i v e l y good c a p a b i l i t y e x i s t s f o r c a r r y i n g o u t work i n w i n t e r and f o r p r o v i d i n g p r o t e c t i o n against the e f f e c t s o f cold. I n d o i n g so, however, c o s t p e n a l t i e s must be paid. It i s these c o s t s t h a t p r o v i d e t h e p r i n c i p a l m o t i v a t i o n f o r research t o improve

performance i n c o l d weather r a t h e r t h a n any l a c k o f knowledge, means o r a b i l i t y t o do a p a r t i c u l a r task. One e x c e p t i o n i s t h e r e c e n t requirement t o reduce consumption o f o i l . Major s u b j e c t s c u r r e n t l y r e c e i v i n g a t t e n t i o n i n response t o government p o l i c y a r e energy supply, energy c o n s e r v a t i o n and t r a n s p o r t a t i o n .

The d r i v e t o reduce energy use and f i n d a1 t e r n a t i v e s f o r o i l i s causing s i g n i f i c a n t changes i n d e s i g n and c o n s t r u c t i o n p r a c t i c e f o r b u i l d i n g s . For l a r g e b u i l d i n g s , r e s e a r c h i s under way t o reduce heat l o s s and t o develop

more e f f i c i e n t h e a t i n g and environmental c o n t r o l systems. Considerable a t t e n t i o n i s b e i n g g i v e n t o t h e use o f t h e computer f o r m o n i t o r i n g and c o n t r o l 1 in g h e a t i n g and a i r c o n d i t i o n i n g . A c h a l lenge f o r c o n s t r u c t i o n

p r a c t i c e i s t o develop and improve methods f o r achieving the thermal resistance, a i r t i g h t n e s s , m o i s t u r e c o n t r o l and a i r qua1 i t y s p e c i f i e d by owner, a r c h i t e c t and designer.

The d r i v e f o r more a i r t i g h t

,

energy e f f i c i e n t b u i l d i n g s has aggravated the problem of a i r q u a l i t y . For l i v i n g spaces i t i s a subject about which l i t t l e i s known. Several p o l l u t i n g sources can e x i s t i n homes, i n c l u d i n g c i g a r e t t e smoking, cooking, h e a t i n g systems, n a t u r a l sources o f radon gas and gases g i v e n o f f by b u i l d i n g m a t e r i a l s and f u r n i s h i n g s . There i s evidence t h a t such p o l l u t a n t s can a f f e c t t h e occupants and even make a space uninhabitable.

It w i l l be a major t a s k t o i d e n t i f y c l e a r l y the r i s k s t o h e a l t h t h a t they cause and t o e s t a b l i s h a l l o w a b l e l e v e l s o f c o n c e n t r a t i o n and methods by which these l e v e l s can be m o n i t o r e d and maintained.

An i m p o r t a n t requirement f o r c o l d regions i s a dependable h e a t i n g

system. Most h e a t i n g systems i n Canada r e q u i r e e l e c t r i c i t y , and t h i s imposes a r i s k t o continuous o p e r a t i o n t h a t i s independent o f the system i t s e l f . Very "low energy" homes r e q u i r e so l i t t l e heat t h a t c u r r e n t f u e l burning systems are n o t s u i t a b l e f o r them. There w i l l be a growing need f o r small h e a t i n g u n i t s t h a t a r e independent o f t h e e l e c t r i c a l supply o r have an a p p r o p r i a t e back-up system.

F r o s t a c t i o n i s a major cause o f damage t o roads and imposes severe l i m i t a t i o n s on t h e speed a t which t r a i n s can t r a v e l . E f f o i t s t o remove o r minimize these e f f e c t s w i l l continue. The performance of ecpipment i n c o l d weather i s another i m p o r t a n t problem. A major c o l d room has been constructed by t h e N a t i o n a l Research Council Canada t o p e r m i t study o f the e f f e c t s o f c o l d on v e h i c l e s , r a i l w a y c a r s , and 1 ocomotives.

W i t h i n t h e p a s t f i v e years t h e r e have been two major reviews o f research

needs f o r e n g i n e e r i n g i n t h e North. The f i r s i was a j o i n t U.S. -Canada study

t h a t concluded w i t h a workshop addressing t h e needs o f c i v i l

e n g i n e e r i n g ( 3 0 ) . The second was a study undertaken by the National Research

Counci 1 Canada of research and development f o r engineering i n c o l d

regions(14). The r e p o r t s o f these s t u d i e s summarize i n d e t a i l problems t o

be solved and research t o be c a r r i e d out. Many o f t h e i r f i n d i n g s a l s o apply t o

t h e south, p a r t i c u l a r l y t o t h e c e n t r a l P r a i r i e region.

The Northern C i v i 1 Engineering Research ~ o r k s h o ~ ( 3 ~ ) considered

problems and research a s s o c i a t e d w i t h i c e and snow, frozen ground, hydro1 ogy

,

t h e environment, m u n i c i p a l f a c i l i t i e s , t r a n s p o r t a t i o n and resource development. I t s o b j e c t i v e s were t o :

-

survey t h e s t a t e - o f - t h e - a r t f o r each t o p i c ,

-

assess p r o s p e c t i v e developments i n t h e North t h a i depend on c i v i l

engineering,

-

assess t h e s t a t u s o f c u r r e n t and p r o s p e c t i v e research programs i n

Canadian and

U.S.

u n i v e r s i t i e s and government research centres,

-

p r o v i d e a g u i d e and r a t i o n a l e f o r research needs i n n o r t h e r n c i v i l

e n g i n e e r i n g d u r i n g t h e n e x t decade and recommend p r i o r i t i e s and s t r a t e g i e s ,

-

e v a l u a t e c u r r e n t f a c i l i t i e s f o r t r a n s f e r o f i n f o r n a t i c n ,

-

e v a l u a t e c u r r e n t appl i c a t i o n o f knowledge.

The study c a r r i e d out by t h e N a t i o n a l Research C o u n c i l ( I 4 )

considered f i v e broad s u b j e c t s : n o r t h e r n settlements, resource development,

major e n g i n e e r i n g works, oceans engineering, and t r a n s p o r t a t i o n and c o m u n i c a t i o n s .

I t s o b j e c t i v e s were t o :

-

_{e s t a b l i s h t h e needs o f i n d u s t r y and government f o r research and}

development i n support o f e n g i n e e r i n g i n c o l d regions;

-

determine Canadian c a p a b i l i t i e s f o r t h i s work;

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i d e n t i f y d e f i c i e n c i e s and recommend how they can be overcome. I n f o r m a t i o n was obtained p r i m a r i l y through seminars t h a t brought

t o g e t h e r i n d i v i d u a l s d i r e c t l y concerned w i t h engineering i n t h e North o r those who c o u l d p r o v i d e complementary o r s u p p o r t i n g services. A d d i t i o n a l i n f o m a t i o n was o b t a i n e d through i n t e r v i e w s and w r i t t e n submissions t h a t formed t h e basis

f o r d i s c u s s i o n a t t h e seminars. Two major submissions on research and

development needs were prepared, one f o r c i v i l engineering and t h e o t h e r f o r ocean engineering(31,32) ; and an i n v e n t o r y was made o f Canadian capabi

1

i t i e s and f a c i l i t i e s ( 3 3 ) .

There was c o n s i d e r a b l e agreement between t h e two studies. Both c l e a r l y i d e n t i f i e d t h e need t o e s t a b l i s h t h e e n g i n e e r i n g p r a c t i c e t h a t i s a p p r o p r i a t e f o r permafrost regions. P a r t i c u l a r emphasis was placed on: t h e d e s i r a b i l i t y o f s t u d i e s of-performance o f s t r u c t u r e s as an e f f e c t i v e way t o d e f i n e b o t h good and bad p r a c t i c e , problems t h a t need a t t e n t i on, p o s s i b l e s o l u t i o n s , and necessary research.

P r a c t i c e t h a t i s s u i t a b l e f o r southern c o n d i t i o n s cannot be d i r e c t l y a p p l i e d i n t h e North. Vany p r o j e c t s have challenggd and w i l l c o n t i n u e t o c h a l i e n g e t h e l i m i t s o f p r e s e n t c a p a b i l i t y , technology and methods. Kew

t e c h n o l o g i e s and e n g i n e e r i n g methods must be developed f o r work b o t h on and o f f shore. Such needs p r o v i d e t h e m o t i v a t i o n f o r much o f t h e n o r t h e r n " c o l d

r e g i o n s " research b e i n g c a r r i e d o u t a t t h e p r e s e n t time. Some o f t h e needs i d s n t i f i e d by t h e two s t u d i e s a r e presented i n Appendix 1.