Climate in Relation to Frost Action

Publisher’s version / Version de l'éditeur:

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à [email protected].

Questions? Contact the NRC Publications Archive team at

[email protected]. If you wish to email the authors directly, please see the first page of the publication for their contact information.

https://publications-cnrc.canada.ca/fra/droits

L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.

Report (National Research Council of Canada. Division of Building Research), 1955-01-01

READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.

https://nrc-publications.canada.ca/eng/copyright

NRC Publications Archive Record / Notice des Archives des publications du CNRC :

https://nrc-publications.canada.ca/eng/view/object/?id=7a0c8490-a3e4-466e-8af0-4d4abcbe7fe2 https://publications-cnrc.canada.ca/fra/voir/objet/?id=7a0c8490-a3e4-466e-8af0-4d4abcbe7fe2

NRC Publications Archive

Archives des publications du CNRC

For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.

https://doi.org/10.4224/20378348

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

Climate in Relation to Frost Action

N O T F O B P U B L I C A T I O N

N A T I O N A L HESEAHCF COL NCIL

C

Aj

iAUA C L I M A T E I N HELATION TO

FHOST

A C T I O i J C a r l B. Crawford A s s i s t a n t Research O f f i c e r A N A L Y Z E D end Donald W. Boyd C l i m a t o l o g i s t ( D B R ) ( D e p a r t m e n t of ~ r a n s ~ o r t ) T h i s paper h a s been p r e p a r e d f o r p r e s e n t a t l c n

~t

t % e t h i r t y - f o u r t h annual meeting o f t h e Highway Research Board a7161 i s slubject t o r e v i s i o n 1,efoi.e p u b l i c a t i o n

by tbc Board, Report No.

59

o f t h e D i v i s i o n o f _{B u i l d i n g Research} Ottawa J a 1 u a . r ~

1955

C l i m a t e i n R e l a t i o n t o Z'rost A c t i o n

C a r l B. Crawford and Donald W. 3oyd

I n p r a c t i c a l l y a l l of Canada and most of t h e U n i t e d S t a t e s T r o s t a c t i o n i s a problem o f major i m p o r t a n c e i n h i g h v a y and a i r p o ~ t e n z . i n e e r i n g . The t e r m " f r o s t a c t i o n " i s u s e d h e r e i n i t s b r o a d sezlse i;o i n c l u d e any d e t r i m e x l t a l e f f e c t o n e n g i l i e e r i n s iiorlcs r e s1.j.'. Ling from t h e p e n e t r a t i o n of f r o s t below t h e s u r f a c e of t h e ground.

F o r more t h a n a c e n t u r y s c i e n t i s t s and e n g i n e e r s have h s s n

c o n c e r n e d w i t h t h e d e s t r u c t i v e e f f e c t s o f f r o s t a c t i o n . The adventr. o f modern l a n d and a i y t r a n s ? o r t a t i o n h a s added ur;i:ncy t o t h s

r x c e s s a r y s o l u t i o r ~ o f t h e problem, T h i s h a s r e s u l t e d i n many i n - v e s t i g a t i o n s a r d a v o l ~ ~ r n i n o u s l i t e r a t u r e on t h e sub j e c t . F o r t u n a t e l y t h i s was s t u d i e d , a b s t r a c t e d and c o r r e l a t e d in t h e a d m i r a b l e r e v i e w n T

t h e l i t e r a t u r e on f r o s t a c t i o n by Johnson ( 1 9 5 2 ) , Development of T h e o r i e s o n F r o s t Heaving

The most s i g n i f i c a n t dcvelopments i n t h e u n d e r s t a . n d i n g o f t h e f ~ o s t a c t i o n phenomenon o c c u r r e d a b o u t t w e n t y - f i v e g e a r s ago. I.fu.2h ;;load :,sork 7r7.a.J. b e e n done e a r l i e r b u t

i t

was t h e p l l b l i s b i n g o f

T a b e r : s t r l e a t i s e on " F r o s t Keavin~;" i n 1929 t h a t i n t r o d u c e d t h e e l e ~ e i , ! t s of' t h e t h e o r i e s on f r o s t a c t i o n i - h f c h axle now w i d e l y h e l d , C o i n c i d e n t w i t h T a S e r f s wor!r was th.3 e q u a l l y i m p o r t a n t work o f Beskow lin Sweden- A l t h o u z h Beslcow had b e e n warmly r e c e i v e d i n America

d u r i n g t h e F i r 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 on S o i l Mechanics and

Founda-tion E n ~ i n e e r i n g f n 193h, h i s work. was n o t w i d e l y known i n this

~ i > ~ - ~ i l t l 1 p u n t i l O s t e r b c r g t r a n s l a t e d h i s o r a i g i i i a l p a p e r s i l l t o E n g l i s h

i n 191!

7.

Taber p o s t u l a t e d t h a t a s t e a d y p e n e t r a t i o n o f f r o s t i n t o ~ 2 e r ~ a i n t y p c s o f s o i l v o u l d r e s u l t i n t h e f o r m a t i o n of i c e l e n s e s

whisl-l would p r o d u c e 'neavin<g of t h e s u r f a c e . I n 1930 Benkelmag an6

GLmstead, o n t h e b a s i s o f l a b o r a t o r y s t u e i s s and many f i e l d o b s e r v t - Lons, placpo s e d t h a t f r e e z e - t h a v c y c l i n g 01' a i r t e m p e r a t u r e was

n e c e z s a r y f o r t h e f o r m a t i o n o f l e n s e s , A l t h o l i ~ h Taber 1 s t h e o r y a p p e a r s

t o be more w i d e l y a c c e p t e d , t h e s i g n i f i c a n c e o f f r e e z e - t h a w c y c l i n ; h a s n o t y e t b e e n s a t i s f a c t o r i l y r e s o l v e d . Recent work i n d i c a t e s t h a t t h e r e i s no l i m i t t o t h e t h i c k n e s s t o wliich a n i c e l e n s may form u n d e r a slow s t e a d y p e n e t r a t i o n of f r o s t . T h e r e i s however, some r e a s o n t o b e l i e v e t h a t c y c l i n 3 o f a i r t e m p e r a t u r e s , a common f e a t u r e of t h e w e a t h e r , c o n t r i b u t e s s i g n i f i c a n t l y t o f r o s t damage t o r o a d s ,

E m p i r i c a l R e l a t i o n s h i p s

There a r e many v a r i a b l e s which a f f e c t t h e p e n e t r a t i o n of f r o s t i n t o t h e s o i l (Crawford 1952). There a r e many a d d i t i o n a l f a c t o r s which w i l l a f f e c t t h e f r o s t damage t o subgrades (Johnson 1952). I n t h e s o l u t i o n of t h e problem, t h e r e a r e two methods of

approach i n which t h e s e v a r i a b l e s have v a s t l y d i f f e r e n t s i g n i f i c a n c e , I n fundamental i n v e s t i g a t i o n s i n t o t h e mechanics of f r o s t a c t i o n , t h e i n v e s t i g a t o r s must a t t e m p t t o c o n s i d e r a l l v a r i a b l e s . I n p r a c t i c a l i n v e s t i g a t i o n s o r i n a p p l i c a t i o n of fundamental r e s u l t s , however, t h e e n g i n e e r milst exclude minor v a r i a b l e s and a p p l y

a v e r a g e s o r s t a t i s t i c a l f a c t o r s t o t h e v a r i a b l e s of major importance. Consider, f o r example, t h e 1201e of t h e s o i l m o i s t u r e c o n t e n t , a

f a c t o r which i s obviously important and which, t o a l a r g e degree, d e t e r m i n e s t h e s e v e r i t y of f r o s t a c t i o n . I n a fundamental a n a l y s i s t h e i n v e s t i g a t o r must understand t h e p h y s i c a l s t a t e of t h e s o i l water, i t s chemical c o n t e n t , i t s r a t e of movemellt and whether i t moves a s l i q u i d o r vapour under t e m p e r a t u r e g r a d i e n t . I n a d d i t i o n t o i t s d i r e c t e f f e c t s , t h e s o i l m o i s t u r e w i l l g r e a t l y i n f l u e n c e

such v a r i a b l e s a s t h e c o e f f i c i e n t s of thermal c o n d u c t i v i t y , s p e c i f i c h e a t , r a d i a t i o n and e v a p o r a t i o n . On t h e o t h e r hand, i n a t t e m p t s t o e x p l a i n f r o s t damage i n t h e f i e l d average v a l u e s o n l y can b e

c i t e d . Because of v a r i a b i l i t y i n t h e s o i l and sampling d i f f i c u l t i e s , f u r t h e r refinement i s n o t p o s s i b l e . Furthermore, t h e u s e of p r e c i s e v a h i e s of s o i l m o i s t u r e c o n t e n t f o r computing o r p r e d i c t i n g f r o s t p e n e t r a t i o n a r e i m p r a c t i c a l because f i e l d c o n t r o l of m o i s t u r e c o n t e n t f o l l o w i n g c o n s t r l c t i o n i s g e n e r a l l y impossible.

T h i s same l i m i t a t i o n w i l l apply t o any attempt t o r e l a t e c l i m a t i c e f f e c t s w i t h f r o s t a c t i o n .

It

w i l l be n e c e s s a r y t o n e g l e c t completely many i m p o r t a n t f a c t o r s i n o r d e r t o o b t a i n workable

r e l a t i o n s h i p s . The d e s i g n of t h e roadway and t h e volume of t r a f f i c , i n a d d i t i o n t o c l i m a t e and s o i l t y p e , w i l l have a c o n s i d e r a b l e

i n f l u e n c e on t h e amount of damage r i h i c l ~ can be a t t r i b u t e d t o f r o s t a c t i o n b u t t h e s e two f a c t o r s a r e superimposed c o n d i t i o n s and must t h e r e f o r e be n e g l e c t e d .

Casagrande i n 1931 i l l u s t r a t e d an e m p i r i c a l r e l a t i o n s h i p between t h e cumulative degree-days of below f r e e z i n g a i r t e m p e r a t u r e s

and t h e p e n e t r a t i o n of f r o s t i n t o t h e ground. The i d e a of t h i s simple r e l a t i o n s h i p had been mentioned by Sourwine two y e a r s

e a r l i e r (Sourwine 1929). It i s based on t h e premise t h a t a r e a s o n - a b l e measure of t h e magnitude and d u r a t i o n of c o l d f o r any one day i s g i v e n by t h e number of d e g r e e s t h a t t h e mean t e m p e r a t u r e i s below f r e e z i n g ; t h e sum of' t h e s e d a i l y v a l u e s f o r t h e w i n t e r season

i s

nori c a l l e d t h e " f r e e z i n g index", Approximate v a l u e s of t h e f r e e z i n g i n d e x can be c a l c u l a t e d by u s i n g o n l y t h e monthly mea2 t e m p e r a t u r e s o r by p l o t t i n g t h e monthly meam t e m p e r a t u r e s and f i n d i n g t h e a r e a between t h e r e s u l t i n g curve and t h e f r e e z i n g l i n e . If a c c u r a t e

v a l u e s a r e needed, however,

i t

i s n e c e s s a r y t o use d a i l y mean t e m p e r a t u r e s f o r t h e computations. Many subsequent i n v e s t i g a t o r s have n o t e d a s i m i l a r c o r r e l a t i o n . A d e f i n i t e e m p i r i c a l r e l a t i o n -

s h i p h a s been e s t a b l i s h e d f o r any p a r t i c u l a r s o i l t y p e under snow f r e e c o n d i t i o n s (Shannon 1945)e Although it w i l l be r e a d i l y a d m i t t e d t h a t t h i s e m p i r i c a l r e l a t i o n s h i p i s an o v e r s i m p l i f i s a t i o n o f complex phenomena, no improvement o f t h e o r i g i n a l curve h a s y e t been p o s s i b l e o

It i s now g e n e r a l l y r e f e r r e d t o a s t h e

U.

S. Corps of Engineers "DesEgn curve" (Corps of Engineers 1947). It h a s been sugsested* t h a t t h e r a t e of accumulation of degree-days of f r e e z i n g a i r

temperatur2es w i l l have a s i g n i f i c a n t e f f e c t on f r o s t p e n e t r a t i o n b u t i n s u f f i c i e n t d a t a a r e a v a i l a b l e t o e s t a b l i s h t h i s e f f e c t . Climatic; S t u d i e s

I n 1929 P r o f e s s o r F. H, Eno p r e s e n t e d a paper t o t h e Ninth Anil~al. IL:eetiilg of t h e Highway Research Board o u t l i n i n g t h e avai-la31e c ? i m a t i c d a t a which a r e of most importance t o h i g h w a ~ e n g f n e e r s (Eno 1929). Twenty-three f i g u r e s were u s e d t o i l l u s t r a t e v a r i o u s f e a t u r e s of a i r t e m p e r a t u r e and f r e e z i n g , sunshine, wind v e l o c f t y , r e l a t i v e hi:midity, e v a p o r a t i o n and p r e c i p i t a t i o n . H e emphasized t h e a ~ p l i c a t i o n of c l i m a t o l o g i c a l d a t a t o d r a i n a g e ,

subzra.de and s u r f a c e s t a b i l i t y , c o n s t r u c t i o n o p e r a t i o n s , maintenance, snow nroblems, load r e s t r i c t i o n s and s a f e t y , T h i s paper was an

i n t r o d u c t i o n t o t h e importance of c l i m a t e i n highway e n g i n e e r i n g

b u t t w e n t y - f i v e y e a r s have passed s i n c e i t s p r e s e n t a t i o n and r e l a t i v e l y l i t t l e e f f o r t h a s been devoted t o t h e promotion of i t s i m p l i c a t i o n s .

C e r t a i n f e a t u r e s of t h e paper however were e l a b o r a t e d i n t h e d i s c u s s i o n by

J.

A , Sourwine, Senior Highvay E n g i n e e r . U.8, Bureau o f P u b l i c Roads, wlio i n t h e f o l l o w i n g y e a r (Sourwine 1 9 3 0 )

published r e s u l t s of a n exteflsive c l i m a t i c study of f r o s t o c c u r r e n c e f o r use i n hizhway d e s i g n , H i s purpose was t o e s t a b l i s h a rnethod of u s i n g r e c o r d e d weather d a t a t o determine t h e p r o b a b i l i t y of ground f r e e z i n g . H i s method i n c l u d e d t h e e f f e c t s of only t h e

i n t e n s f t y , d u r a t i o n and frequency of low a i r t e m p e r a t u r e o c c u r r e n c e s based cn p a s t r e c o r d s ,

From t h e work of Bouyoucos and P e t i t on t h e r e q u i r e d d u r a t i o n and lowering of a i r temperature t o produce f r e e z i n g i n

s o i l and a study of low t e m p e r a t u r e d u r a t i o n s from m e t e o r o l o g i c a l r e c o r d s , S o u ~ w i n e e s t a b l i s h e d 2 3 ' ~ a s t h e " c r i t i c a l i n i t i a l a i r t e m p e r a t u r e v ' f o r f r e e z i n n . of t h e ground s u r f a c e . He t h e n assumed

a

d e p t h of 3-in. a s t h e 'depth below which ground f r e e z i n g becomes a problem f o r c o n s i d e r a t i o n i n highway design". Again r e f e r r i n g t o t h e work of Bouyoucos a d P e t i t , he e s t a b l i s h e d 2 6 , k 0 ~ a s t h e

" a b s o l u t e minimum s o i l t e m p e r a t u r e c o i n c i d e n t w i t h t h e i n c e p t i o n of ground f r e e z i n g " , based on t h e r e q u i r e d super coolirlg of t h e

s o i l

and c o r r e c t e d f o r d u r a t i o n of c o l d p e r i o d a s shown by m e t e o r o l o g i c a l r e c o r d s , From t h e f i e l d o b s e r v a t i o n s of Bouyoucos, 15OF was found t o be t h e ''average minimum a i r t e m p e r a t u r e e q u i v a l e n t t o a s o i l temperature of 2 6 . i C 0 ~ a t a d e p t h o f 3-in. From t h e r e c o r d s of

s e v e r a l s t a t i o n s of t h e U, S, Weather Bureau, Sourwine analgsed a l l p e r i o d s d u r i n g which t h e a i r temperature f e l l below 2J°F ( t h e

c r i t i c a l i n i t i a l a i r tem7erature f o r ground f r e e z i n g ) and found t h a t t h e a b s o l u t e minimum t e m p e r a t u r e d u r i n g any p e r i o d was on t h e

average 1:!'1" c o l d e r t h a n t h e minirn~xn t e n i p e r a t u r e o c c u r r i n g w i t h

5

per.c,ent, frequency*. From t h i s he r e a s o n e d t h a t s i n c e 16°F i s the a i r t e m p e r a t u r e a t which ground f r e e z i n g b e g i n s a t 3-in. d e p t h ,

3°F

r e p r e s e n t s a " c r i t i c a l a b s o l u t e minimum a i r t e m p e r a t u r e " c o i n - c l d e n t , x i t h

5

p e r c e n t f r e q u e n c y of ground f r e e z i n g a t a 3-in. depth. H e t:i:.?.r: : a ~ : ~ L g a ~ e d v a l u e s of niontbly a v e r a g e d a i l y minimum temperaturae f o r f ' o u ~ sta-tTons and fourlil, by c o i n c i d e 2 c e , a c r i t i c a l . v a l u e of

2 3 O F f o r t h e "lobjest mor~thlg average of d a i l y minimum temperature1' .. "7- ; >,'*

LUI.~.~~,!L he assumed

t o

be a c r i t i c a l d e s i g n v a l u e f o r hj-ghway groimd

f r c , e z f r ~ s .

Suurwine extended l i i s i n i t i a l work t o cl s t u d y of t h e e f f e c t

o i _{i i u r ~ t i o n of' c o l d p e r i o d s . He s t u d i e d r e c o r d s over a 15-yesr}

p e r i o d f o r t h i r t y - f i v e s t a t i o n s n e a r t h e

23°F

minimum a i r t e m ? e r a t - w e

i ~ t j : ~ 3 s n ? ~ i x i determined i n each ca.:!e t h e c o l d p e r i o d d u r a t i o n i n

d s :;rae.,ho.iirs .~~lii.cl; c ~ c ; ~ . i ~ ~ > e d l 5x1

5

p e r c e n t of a l l c o l d p e r i o d s . After. sc/.:-?s:.cer:i'tjle s t u d y , a "de:T;i-.ee-hour-index" of 300 f o r

5

p e r c e n t

fraqi.l.2.:-:y vcciirrence w : ~ s c;'i.osell t o r e p r e s e n t - t h e dal.zger l i n e f o r

h'

L b ."kl,:~i..- ypo?lryfi f 3 - ~ 3 ~ i l l g * Y

Cornb,i.i~in~ t h e s e two s t u d i e s , Sourwine p l o t t e d a " c r i t f c a l

4.:.;l:le;~. T9,ine l o r hi:;hr.~ay ground f r e e z i n g t ' on a map of t h e United S t a t e s ,

. - ~ .,

~+'~;;..UPE:

1

x?lich, on tht? b a s i s of' weather r e c o r d s a l o n e , s e p a r a t e s

--*-.-- F

. ,.7q., A , ~ . ~ . ~ +; --:--- ~. rkcl.fiti~re2;: s a f e fron: hi$;h.~~:.:r*y grountl. r r e e z f i i g from t e r i a i t o r g

.~..r; :.;%x:iou s d e i ~ z e r of' highway grouni!. I'~*eezim;:,,

.

A p o r t i o r ~ of t h e

.!.: e - v i f t o r ; i . : ~ s e r f 07.1s da~?.:;er accoradrng t o t e m p e r a t u r e d a t a , was

r17~1cl.ifl.ed t o bs a re;;ion of' d o u b t f u l danger due t o th.e na.l;u.re o f i t s

rdr:.i;cr ( D e c e ~ b e r

-

r"cbr2uary) r e i n f a l l , T h i s re:;ion., ~ ~ l a i n l y i r i t h e

;-,.~.:.:.th c e n t r i a l United S t a t e s , ;?.as l e s s t h ~ 3 . x ~ 2-in, of averaGe w i n t e r 1 j r e c 3 . p i t a t i o n w i t h a l o w e s t rnon-thly a v e r a g e of d a i l y minimum temp-- er.at>lre betiireen 10°F ancl 2 3 ' ~ .

T h f s r e v i e w of Soll.rwineQs t?ro~l.: i s p r e s e n t e d beca.use

i t

i s

t.i.i;j mcjst; ex-Lensive a i l a l y s i s of m a t i - : e r r e c o r d s rin rela-l;i.on t o I?r33t

a.st:,iori Icfi:,cm t o t h e a u t h o r s . The pUPpGSe of' tlie stndy rzras t o detei?i,ii.t::?,

c ~ n the & ~ 2 i s of3 tl:.et.eorological d a t a o n l y , t h e approximate southerri boundary of' 21-oba'cle hi5bua.j. T r o s t darn-age. It does n o t i n c l u d e

I.mpo:at.ant f n t r i n s i c v a r i a b l e s s11ch a s s o i l t y p e , s o i l m o i s t u r e ~orit:.e;:~t, d e n . s i t y o r s u r f a c e cover b u t , t o a d e g r e e , t h e o b j e c t i v e bras acc;o.cr:IF-

I

l s'ried and t h e approach encourages f u r t h e r s t u d y f o r r e l a t e d pur7po s e s .

Recent Clircat i c S t u d i e s

I n r e c e n t y e a r s many s t u d i e s have been made r e l a t . i n g clirnat.2

a ~ . d s e i l t e n p e r a t u r e s . From t h e s e s t - u d i e s t h e r e r e s u l t e d some general. r e l a t i o n s h i p s between c l i m a t e and f r o s t a c t i o n b u t few s p e c i f i c

s o r : r e l a t i o n s have been evolved. It was encouraging t o t h e a u t h o r s

t b . e r e i " o r e , t o r e v i e w t h e work of Lolch (1952) who, ~ a o r k i n g a . t Pirrdue U n i v e i l s i t q - , a t t e m p t e d t o cofibine t e n p e r a t u r e and p r e c i p i t a t i o n data

t o e ~ g i l : i i n v a r i s t i c n s i n t h e s e v e r i t y o f s p r i n g breakup of ron.ds.

-

.

-

-

--.. .

+

"5

r:el=cexlt a l l o w a b l e f'requency" i s a ~ i j l t r a r i l y deTined

"

t o inear, tl:&i, r.ikle;l ire c o n s i d e r f o ~ any l o c a l i t y a l l c o l d p e r i o d s s u f f i c i e n t t o cause f r e e z i n g of a v e r a g e s u r f a c e s o i l , groun8.3 f r e e z i n g below

3-in.

de?t;k: m a y O C C L I ~ one time i n 20. A frequency of' more t h a n

5

percent.

R

t i

Uslng a v e r e g e v a l u e s f o r a b o u t s e v e n t y s t a t i o n s

In

I n d i a n a , h e p l o t t e d monthly rnean t e m p e r a t u r e , t , o t a l p r e c i p i t a t i o n and n o r m a l p r e c . l p i t a t : . i ~ n I n r e l a t i o n

t o

t i m e , f o p s i x t e e n w i n t e r s e a s o n s ,

TJsin~; smooth c u r v e s t h r o u g h t h e s e monthly averazc: p o i n t s h e computed

t h e " f r e e z i n g i n d e x t t ( a r e a between a c t u a l a i r - t e m p e r a t u r e an.d 3 2 O ~ ) II

a.nd a p ~ e c i p i t a t f o n i.ndext' ( a r e z between n o r m a l and a c t u a l p r e c i p 9 . t - a t i c n dur.ing t h e 30-day p e r i o d 1;ef'ore f r e e z e - u p ) f o r e a c h w i n t e r

sea.son, Though. v a r i o u s c o m b i n a t i o ~ s of t e r n p e r a ~ u r e and p r e c i p i t s t f o r . were . t r i e d t l i e b e s t c o r r e l a t i o n between a c t u a l . s p r i ~ : ~ b r e a k u p o f

r ~ a d s a.nd w e a t h e r was f o u n d u s i n g t h e p r o d u c t o f f r e e z i n g - i n d e x and

the

:30=,day p r e c i p l - t a t i o n i n d e x a s a n i n d e x o f the s e ~ e r i t ~ y o f r o a d b ~ e a k b - p .

Dolch r e c o g n i z e d t h a t f r e e z i n g c h a r a c t e r i s t i c s a l o n e would n o t f l > d i c a t e the p o t e n t i a l s e v e r i t y of s p r i n g b r e a k u p and h i s d a t a z e r t a i n i y s u p p o r t t h i s view, (One o f t h e most s e v e r e b r e a k u p s

f o l l o w e d a x i n t e r d u r i n g which t h e f r e e z i n g inclex f o r t h e S t a t e w a s

o n l y

6

d e ~ , r e e - d a y s . ) He a l s o c o n c l u d e d , from #?is w e a t h e r d a t a , thar,

s r ~ o x f a l l a ~ d f r e e z e - t h a w c y c l e s had no b e a r i n 6 on t h e s e v e r i t y o f s p r i n g brealcup,

T h e r e a r e c e r t a i n d i s a d v a n t a g e s i n u s i n g a " p r e c i p i t a t i o r t i n d e x 7 ' such a s t h a t u s e d by Dolch. For example, t h e u s e o f d e p a r t - n c ; from normal p r e c i p i t a t i o n r e s t r i c t s a b r o a d a p p l i c a t i o n of t h e d a t a and f ~ ~ r t h e r , t h e p r e c i p i t a t i o n d u r i n g a p a r t i c ? l l a r p e r i o d rnay be

q u i t e u ~ r e i a t e d t o s o i l m o i s t u r e c o n d i t i o n s . The a v a i l a b i l i t y o f s o i l m o i s t u r e must depend n o t o n l y on p r e c i p i t a t i o n and s o i l t y p e

b:lt a l s o on t h e r e i ~ i o n a l c l i m a t e ,

I n a g e n e r a l a n a l y s i s of t h e problem, t h e e n g i n e e r c a n turj.1 t c r=l.irnatology and t o a g r i c u l t u r a l s o i l s c i e n c e f o r f u r t h e r a s s ' i s t a n z e , T h ~ r n ~ h w a i t e (194.8) has p o i n t e d o u t t h a t p r e c i p i t a t i o n

a l o n e d o e s not i n d i c a t e w h e t h e r a c l i m a t e i s m o i s t o r d r y . It nus%

a l s o b e known w h e t h e r p r e c f p i t a t i o n i s g r e a t e r o r l e s s t h a n t h e

w a t e r n e e d e d f o r e v a p o r a t i o n and t r a ~ s p i r a t i o n . Where p r e c i p i t & t i i ; x - . e x c e e d s w a t e r n e e d , t h e c l i m a t e i s m o i s t anu where i t i s l e s s i;ha~,

wa.ter n e e d , t h e c l f m a t e i s d r y .

The combined e v a p o r a t i o n f r o m t h e s o i l s u r f a c e and trans-

p i r a t i o n from p l a n t s i s t e r m e d ' L e v a p o t r a n s p i r a t i o n ' t o The amount a?

w a t e r t h a t x o u l d e v a p o r a t e a n 6 t r a n s p i r e i f i t were a v a i l a b l e i s

c a l l e d " p o t e n ~ t a l e v a ~ o t r a n s p l r a t i o ~ i " . Thornt1iwait.e p o i n t s o u t

that

e v a p o t r a n s p i r a t i o n and p r e c 5 p i t a t i o n , r e p ~ e s e n t i n g f L c w of rtioisturle t o and fronl t h e a-trnosphere r e s p e c t i v e l y , a r e e q u a l l y

i m p o r t a n t cl'irriatic f'ac t o r s . E v a p o t r a n s p i r a t i o n can 'be measured o n l y wi.t':l c o n s i d e r a b l e d i f f i c u l t y e-nd p o t e n t i a l e v a p o t r a n s p i r a t i o n nr;.s;; 'be d e t e r m i n e d e x p e r i m e n t a l l y . S i n c e t h e d e t e r m i ~ a t i o n of' p o t e n t i a l e v a p c t r a n s p i . r a . t l o ~ ? i s so d i f f ' i c u l t , i t was necossai:,g- t o estab!,isk a r e l a t i o n s h f p between p o t e n t i a l e v a p o t r a n s p i r s . t . i o n and o t h e r

clin?a-kit f a i > t o r ~ . T h i s was done by Thornttlhraite artd alt-hou:.;!..i t h e

r e l a t i o n s h i p i s e n t i r e l y e m p i r i c a l , i t h a s b e e n found t o b e s a t -

f

s f a c t o r y f o r c o m p a r a t i v e plliQpoSes. Compxted vzl.lur s can. 5 e obtai.rred from t e m p e r a t u r e r e c o r d s and l a t i t u d e .

The a n n u a l p o t e n t i a l e v a p o t r a n s ~ l r a t i o n r a n g e s fsom T L D I ~ E

t h a n 60-in. i n t h e So~:tJher*n U z l t e d S t a t e s t o l e s s t h a n 18-in. i n t h e w e s t e r n mountains; i t v a r i e s g r e z t l y :horn su~m.er t o w i n t e r , Aloxg most of t h e Canadian b o r d e r i t i s l e s s t h a n 21-in. I n

s01,:t.her.n O n t a r i o i t ra;?zes from 20 t o 20 i n . ( S a ~ i d e r s o n 1 9 5 0 ) .

The cornbir~ation of p o t e . ! ? t i a l e v n . p o t r ~ a n s p i r a t i o n ~ and a c t ' u a l ~ r ~ ~ : c i p : ~ ~ ; -

a.tl.r=:r,. P C S - U ~ ~ S i n

art

i n d e x of' s o i l !aoisti~i-*e con:!;itions which c a n b e

s t a 5 e d a s rsater s ~ i ~ b p l a s , w 2 i ; s r st;orage, o r w a t e r def i c i e c c - , .

The

f a c t t . h a . t p r a e c f p i t a t i o n v a r i e s g r e a t l y 1 1 ~ 2 t h s e a s o n :nust Ssc; .tal;el?.

i n t o accsl.-;nt. ( I n most r e g i o n s , b u t ?not a l l , t h e g r e a t e s t ~ : l ~ e c ; i - j j i t - -

a t i o n o c c c r s a u r i r ? ~ t-;z~e i ; r o ~ ~ i : ? ~ ; sensoxi. ) T o acco~.:.nt f o r tllris v a ~ i a b i l i t y , an a s s ~ ~ m p t i o n r n ~ s t ; he 17:ade r e g a r d i n g t h e sti.s,e;j;e

~ ) a ~ . . q :A C. it:/ , of

the

s o i l . It i s assumed t h a t a c e r t a i n amount of r ! u l : ~ -

f a l l car1 be s t o r e d arld any omo~:nt i n e x c e s s of t h . i s q u a n t i t y : h i 1 1 1 r u n - o f f o r he ll.sed i n ~ecEiarg5ng th e groundwater t a b l e . It i s

~>eccsgnized t h a t the xtoliage capackty w i l l v a r x w i t h s o i l -type and d i s t r * i b u t i o n of r o o t ~ y s t e ~ l s . TE~ornthwaite s t a t e s t h a t "except 3.12

a r e a s of s h a l l o w soril t h e w a t e r s t o r a g e c a p a c i t y a v a i l a b l e t o : ? . a t u ~ 3 pl.o.nts ~ r ~ i t , ? ? f i l l y deveicped root, systems v a r i e s ar.ound a rilean t h a t

i s t b e e q u i v a l e ~ ~ t of abo~.lt 1 0 c e n t i r c e t o r s o r [I. inc1.e~ of r a i n l " a l l l ' . For p u r p o s e s of i l l u s t r a t i o n two extreme c l i m a t i c c a s e s .?.re Q ~ O T A T ~ i n Fi5~;urae 2 ( f r o m Tk;orn.thwaite 1 9 4 8 ) . It i s s e e n t h a t at S a l . i s b ~ i r y ,

N.Y.

no -imt e r def i c i a r l c i e s 0ccu.r durain;; t h e a v e r a g e y e a r . A t NortY~. Rend, !n!asl!int;to.l?, ori t h e o"L1er hand, where a n n u a l r a i n f a l l i s s l i g h t l y g r e a t e r , a s e r i o u s deficiency l a s t i n g )pore t:";an f o u r rnontY's

may

be expected d u r i n g t h e a v e r a g e y e a r . It seerc.5 o b v i o u . ~ t h a t grou~.dr.rater and s o i l ~ o l s t u r e c o n d i . t i o n s a t t h e s e two l o c a t i o n s w i l l be e n t i r e l y d i f f e r e n t , F u r t l ~ e r m o r e , i t i s p r o b a b l e t h a t t l i e r e e x i s t s a r e l a t i o n s h i p between th.e cornbination of p r e - c i p i t a t i o n and p o t e n t i n l e v a p o t r a n s p l . r a t i o n and t h e s o i l moistl- re

c o n d i t . i o n s a t any l o c a t i o n .

The importance of clima+,e t o p r a a c t i c a l a s p e c t s of b u i l d l r i g r e s e a r c h l e d , i n 191+9, t o a s i n $ ~ : l a r l g u s e f u l arrange~rlent b e t t ~ e e n t h e l j i v i s i o n of Guildin;; Research of t h e Natiolial R e s e a r c J i C o ' m c i l and tine FIeteorologi.ca1 E i v i s i o n o f t h e Gepartroerlt of T r a n s p o r t . By t h i s s p e c i a l agreement t1,e f u l l time s e r v i c e s of a trainc.cl m e t e o r o l o g i s t a r e seconded t o t h e U i v i s i o n f o r co-operat i v e work on b u i l d i n g problems w h i l e rets2n.ln.g t h e a s s o c i a t i o n s and f a c i l i t i e s of t h e M e t e o r o l o g i c a l S e r v i c e . The co-author of t h l s p a p e r i s t h e

second p e r s o n t o h o l d t , h i s vniqv-e p o s i t r o n . One of t h e f i r s t j o i n t s t u d i e s was t o a n a l y s e t h e weat5er c o n d i t i o n s rdhlch accompanied an u n u s u a l s p l - i n ~ breakup of r o a d s i n t h e P r o v i n c e of A l b e r t a .

Examples of S p r i n g Breakup of Roads

( a ) C a l g a r y , A l b e r t a

During t h e s p r i n g season of 1952, r o a d s I n t h e Calgary

d i s t r i c t o f A l b e r t a s u f f e r e d unus1.1al d e t e r i o x D a t i o n w h i l e r o a d s i n t ? i ~

Edmonton area., t o t h e n o r t h , e x p e r i e n c e d a normal breakup. It i s lcnown t h a t f r o s t a c t i o n i n t h e Cal.garg area-, a r e g l o n c f s i l t y s o i l m a n t l e , i s always more s e v e r e t h a n i n t k e p r e d o m i n a n t l y c l a y s o i l s

around Edlnontoz~ b u t i n t h i s p a r t i c u l a r yo:rr t h e b r e a l ~ u p was so se- ere i r , th.e s o u S , i ? e ~ ~ p a r t of t h e p r o v i n c e ?,hat a s p e c i a l i n v e s t i g a t i o x i was t1101:ght t o be warranted. S i n c e t h e we at'..:^;^ could

b e t h e o n l y new v a r i a b l e a s s o c i a t e d w i t h t h e s e d i f f - e r e n c e s , a s t u d y of climatf.;: c o n d i t i o n s , and t h e i r clepartclre frc:a n o r m a l , was ur?.der- t a k e n ,

The most d i f f : c u l t problerfl e n c o u n t e r e d i n a n i n v e s t i g a t f o r ?

of t h i s zyype i s t h e e v a l u a t i o n of r a e l a t i v e r o a d d a m q e , b o t h f n I t s v a r i a - t i o n o v e r a wide a r e a and i n d i s p a r i t y f'rom g e a r t o y e a r . It

was p o s s i b L e t o o b t a i n o n l y d e s c r i p t i v e t e r m s , b a s e d o n e x p e r i e n c e , i n o r d e r t o d i f f e r e n t i a t e t h e d e p e e o f damage from y e a r t o y e a r . S i g n i f i c a n t l y , t h e r o a d t;r.oakup n e a r Calgaray d u r i n g t h e spr3ing o f

1952

i s t e r m e d " t h e w o r s t c n r e c o r d " . T h i s was a t t r i b u t e d , i n a g e n e r a l way, t o a c o m p a r a t i v e l y "wet c y c l e 1 ' i n t h e weath.ela whicl-1 c a u s e d a :;eneral r i s e i n ground w a t e r l e v e l s . S t u d y o f t h e raecords d o e s , I n f a c t , show t h a t t h i s was p r o b a b l y t h e c a s e ,

In

t h e c l i m a t i c i n v e s t i g a t i o l ~ s , a l a r g e v o l ~ u n e of d a t a . -,qas

a.ssem'ul.ed and a.rialysed i n a n a t t e m p t t o e s t a b l i s ' h a r e l a t i o n s h i p b e t w e e n r o a d dmage and t h e w e a t h e r , Weather r e c o r d s f o r s e v e n

e a r s a t C a l g a r y were s t u d i e d ; t h e r e s u l t s & r e sl-lawn i n T a b l e

--

1

.

'Freeze-thaw

e g c l e s " were b a s e d or.~ d a i l y mean t e m p e r a t u r e s ; e a c h f i g u r e i g d i c a t e s t h e number o f t i m e s d u r i n g t h e w i n t e r t h a t t h e mean temperature f e l l below and r o s e above t h s f r e e z f n g p o i n t .

!I

The f r e e z i n p ; i n d s x " was c:;mputed u s i n g m o n t h l y nlean !;emperat-es,

T h i s p r o c e d u r e i s an a p p r o s i m a t f on, a d e q u a t e f o r compar'atfve p u r p c s e s

b u t r e s u l t i n ; i n nn i n d e x which i s u s u a l l y low.,

111 +;he c o r r e l a t i o n of rouci darnage t o w e a t h e r i t was c ~ n - - s i d e r e d d e s i r a t l e t o r e i ' i n e t,lie i n d e x which was o r i g i n a t e d by DoEch, A c c o r d i n g l y t h e "30-day P i > e c i p i t a t i o n I n d e x " i n c l u d e s a c t u a l t o t a l p r e c i p i t a t i o n which o c c u r r e d d u r i n g t h e 30-day p e r i o d S e f o r e f r e e z e - up r a + , h e r t h n n " d e p a r t u r e f r o r t ~ nomnal" b a s e d on g r r ~ p h i e a l a r i a l y s i s . The t ' ~ o l c l l Breakup Index", r e p o r t e d

i n

t h l s p u p c r , i s t h e p r o d u c t o f t h e " F r e e x i ~ f r I n d e x " and t h e "30-day P ~ e c i p i t a t f o n I n d e x q r a s c u t l i r i e d above. V a l u e s of " s o i l m o i s t u r e s t o r a g e " werau computed u s i n g Thor*nthwniteq s t h e o r i e s , " t h e v a l u e i 2 e p r e s e n t s storzige ic

i n z h e s a t the t i m s o f f r e e z e - - u p . The "Modified Irldex" i s t h c

p r o d u c t of' f r e e z i n g i n d e x onci s o i l r n o i s t u r e s t o r b a g e , I n t h e o p i n f o n o t t h e a u t h o r s t h i s i n d e x p r o v i d e s a more a c c u r a t e e v a l u a t i c _ $ of s o i

l

m o i s t u r e c o r r i i t i o n s tharr i s p o s s i b l e usfn:; p r a e c i p P t a t i o n d a t a a l o n e . F o r a corqa1>5son r ) f t h e w i n t e r 02' 1151-s2 w i t h t h a t of o t h e r y e 3 r s , ~ e f e r e n c s may be made t o T a b l e I, h r i n g t h i s p a r t - i c u l a r w i n t - e r , t h e

-,

:curarenee o f i'reeze-thaw c y c l e s was norrfial. The f r e e z i n g i n d e x a s j u s t s l f g l i t l g above nopmal bur; t l ~ c P r e o z e - up occurr.sd a b o u t one -lonth e a r l i e l a t h a n u s u a l . The r q n t si,:nif'ical:t v a r i a t i o - . 1 s occui3red i n t h e p r e c i p i t a k i o n which p r e c e d e d f r e e z e .-dp and i n t h e s o i l r n o i s t u r e s t o r a g e . P r e c i p i t a t i o n d u r i n , + t h e 30-day p e r i o d b e i o r e f r e e z e - u p was a b o u t t h r e e t i m e s t h e a v e r e g z arlli s c i l m o i s t ~ ~ r e s t o r a g e was a b o u t f i v e t i m e s t h e a v e r a g e . I-ieferenc2 t o

showing s o i l m o i s t l ~ r e c o n d i t i o n s a t Calgal>y i'roni to

s u n p o r t s t h e g e n e r a l o p i r i i o n t h a t t h e C a l z a r y w e s w a s e x ~ e r i e n c i n g a "wet s y c l e t ' ,

T'h.2. s d i a g r a m i l l u s t r a t e s +,he v a r i a t + i o r l o f s o 1 1 mof s t u r e

s t o r a g e on a monthly b a s i s . Tklp b a r g r a p h s o f s u r p l u s find d e f i c i e n c y may b e c o n s i d e r e d as f i c t i t i o u s v a l u e s . T h e s u r p l u s q u a n t i . t i e s ,

r e s u l t i n g from i n t e n s i v e r a i n f a l l when s t o r a g e i s c o m p l e t e ,

arc

assumed t o run-cff' o r p e r c o l a t e t o t h e ~ ; r o u n d ~ ; k t e r table and ths

d e f f clt q u a n t i t i . ~ s r e p r e s e n r ;?o+;e4? t i a l eva,?otr.alisp i m t i o n w'r;ich wc;uld o c c u r i f ~ a t e r were a v a i l a b l e . Ne'i-ther of t h e s e qual-,?.it f e s

a r e t e a k e n I n t o a c c o u n t i n t h e c o m p u t a t i o n of s o l 1 m o i s t u r e sto13age, Urrfors~xnatePy,

i t

w a s p o s s i b l e t o o b t a f n cornpara.trs~e

o p i n i o n s c f t h e " s s v e r i t g of r o a d oreakl;lpPP Tor t h e l a s t f o u l S C ; . ~ U , C ~ L ~

o n l y . The 12r>ealLup i n d i c e s f o r t h r e e of t h e s e y e a r s a r e i n t h e

a p p r o p r i a t e c r d e r . The i n d i c e s f o r the w f l l t e r of

1952-53,

however, I n d f s a t 5 2 1i:;ht b r e a k u p wherl

i n

f a c t i t was worse t h a n normal,

S i g n i f i z a n t l y , t h e f r e e z i n g i n d e x f o r t h i s y e a r was o n l y a b o u t o n e - h a l f t h e a v e r a g e ; i t w a s p r o b a b l y t h e m i l d e s t w i n t e r on r e c o r d . F u r t h e r comments o n t h i s f e a t u r e w i l l b e made late:i.

A s t u d y of w e a t h e r r e c o r d s f o r Edmonton d u r i n g t h i s same p e r i ~ d r e v e a l e d t h a t t h e f r e z z i n g i n d e x and p r e c i p i t a t i o n b e f o r e f r s e t e - u p were v e r y c l o s e t o normal. I n f a c t , t l i e r e c o r d s show t,hat Edmonton t e m p e r a t u r e s and p r e c i p i t a t i o n v a r y mum l e s s f ~ o m y e a r kc

y e a r t h a n a t C a l g a r y , T h i s c l i m a t i c f e a t u r e , t o g e t h e r with t,he g r e a t d i f f e r e r l c e I n s o i l t y p e , p r e v i o u s l y r n e n + , i o ~ e d , res111t s i n g r e a t l y d i l ' f e r e n t a v e r a g e b r e a k u p c o n d i t i o n s , It I s n o t e d i n a p r i v a t e c o ~ ~ u n i a t i o n from Dean

H.

M. Hardy o f t h e U n i v e r s i t y o f A l b e r t a t h a t " t h e e f f e c t o f f r o s t a c t i o n f s usiraLly much s l o w e r i n becoming a p p a r e n t a s damage t o pavements t h a n 5s t h e c a s e irL

t h e C s l < ? a r y a r e a .

In

t h e Edmonton a r e a , damage t o pavements r n q s t i l l bt. r l e v e l o 7 i n g a s l a t e a s J u l y by subs-base f a f l u r e w h i l e i n c o ~ t r a s t , i n t h e C a l g a r y a r e a , pavement f a i l u r e o c c u r s a l m o s t w i t h -

i n h o u r s a f t e r t h e breakup". An e x t e n s i v e s u r v e y o f C a l g a r y s t r e e t s ( H a r d y , 1 9 5 0 ) showed t h a t f r o s t darnage occuru3ecl o n l y where i c e

s s g r e g a t i o n t o o k p l a c e w i t h i n s d e p t h of

1 8

o r 20 i n , o f khc s u r f a c r e . H e d e s i g ~ o f t h e s e s t r e e t s u s i n g a m e c h a n i c a l l y s t a b f l f zed ~ i t - - r - ~ g r a v e l b a s e 21! t o

36

i n , t h i c l r h a s p r o v e d a a e q l ~ a t ~ e , even d u r l n r t h e s p r t n g cf

195'2.

( b ) Ottawa, O n t a r i o Observations of r o a d b r e a k u p i n C a r l e t o n C c u n t y , n e a r Ottowa, O n t a p i o , d u r i n g t h e p a s t trso sprSng s e a s o n s l - ~ ~ v e shc;wn t h e r e m a r i i a b l e e f f e c t o f c l i m h t i c v a r 3 a t i o n on f r o s t dal?age. D - u r i ~ 2 t h e s p r l n c ; of

195'2-53,

t h e c o u n t y e x p e r i e n c e d a n ~ ~ r ~ u s u a l l y s e v q r e d e t e r i o r a t i o n c f i t s r o a d system, The f'ollowin,.r; year7 ciarnage >:as c o n f i n e d t o a few i s o l a t e d f r o s t b o i l s .

F i n u r e

<

shows t v u i c a l road c o n d i t i o n s a-t swo P o s u ions

-A'- " A

d u r i n g

r i 9

t w r , c:@rSn;; s e a s o ? l s . F i g u q e s(a) shows 3 n3sctforl of zboad

t h a t was b a r e l y v a s s a b l e on A p r i l Z 9 m e - f e d d r ~ " s c=cr.llew.

i z

tiad beer^ . o o l r ~ ~ ! l . e t & l ~ c l o s e d t o - t r a f f i c . The sar~ir! r b ~ t , - c i 1.2 S ~ ~ C : ~ \ T T I ir

F i g u r e " k ) o r ~ e y e a r late13 on A p r i l 1, 19Sil. A;thc~l %b4 - L C ' *;I? ange

remal.ned i n good c o n d i t i o n . F ~ ~ L I T I S

S ( C )

S ~ C . ~ . T S a similar p i e c e of

r o a d t ! l a t

was

irripassab1.e on ~ E k l 2 ?

19.5'3 b u t

q u i k e s a t l . s f a c t o r , y

during t h e s p r i ~ l g of'

iqsl.i.

(F'i.t';i~.i~e z(d)), T h i s rand !-:ad 5 e e n treated

1,~it.h a b u ~ t . 3n.c;

f t .

of p i t - r u n Z I ? ~ J . V - ~ ~ f , > l _ l c ~ . c i n s t h e spr5.1~:; b r e a k u p

o f 1.953 but i~ shci~an. a s a tj.pi.c:nl. ~ : 3 ! ? . 1 ; ~ : i ~ t ~ ~ S ; W C C ~ t h e ~ F J O seasc.n.g.

T a b l e 2 s h o w s wea.t.-.?e~ d a t a for2 0t;i;ai.r~. s i m i l a r t;c> t,k.r~s?

s'iz~.rgi-1 p2.e-cr5.c.:~ sl-o. f ' o ~ C c".J g a r y .

1%

;.qc.!s a?;airL 1 : ~ s ; r i b l e t,o o & t a i r l

a s s e s s r i ~ : . : : l t cf _{r o a d b r e r l r u p Ju:~Fr_;, o.i-lly .the l a s t Tour y e a r s . DL--''} L~ ~ n g

. t h i s 1 : s r i o d ~ ' Y ~ ~ ~ ~ ~ E . - ~ , ! I E I . ~ ~ I 7 y c l e s eye ~ b c ; u . t n.oranal. Free.zin6.l; j : ~ l d i c ~ s

wzre j-,.ea_:. .!lorrfi.s.l 5xr.eyt; c:!urr!lg 1952-75:3 L J ~ ~ c F ~ Trrjas t h e .mi;.cles-5 :rf:.t;ext on r c . c o r d . Bot'i-i Gr:eal.r~~p i r x i i o e s i n d i c a t e a v e r y t , e d r o a d 'oreakcip du.:rin;i: t l i e

~-~:,~.ir:c

o f 1 9 5 1 en:i t h e ~ i ~ o d i f i e d i n d & x i r i d i c a t e s a

n e g l i g i ' c l e b r e a k u p durinli; t h e s p r i n g of 1952, an.d a bad 'breakup i n

195.3.

To t h f s e x t e n t th.e i n d e x i s a s a t . i s f 4 a c t o r y g u i d e . But t!::e

P n d i c a s fn.tiroate a br;d r o a 6 b_ret:.jrup durir,g t h e s p r i n g 01'

1954

v~heli

Ln

f a c t !jreakup was l i g h t . A more d e t a i l e d a n a l y s i s nT' weati-:er. d a t a i l : i u s t , r a t e s 6.t l e a s t pg.r+t o f t h e r e a s o i l f o r the ~ v a i ~ y i r l s ~ : . s s -

f u l r l e s c of t'rLe i n 6 3 ce s.

F i g u r e

6

s h o i ~ s s o i l m o i s t u r e c o n d i t i o n s a5 O t t a - u s

( accordli-it;

t o t , l ~ e Thornthwaf t e c r i t e r 5 o n ) from 1950 t o 1951;.

Heferer(ce t o F i g u r e

6

a ~ d T a b l e 2 w i l l show t h a t t h e s o i l m o i s t u r e s t o r s g e %,;as f u l l and t h a t a s i g n i f i c a n t sury,l.i:.:: e x i s t e d d.cr.ing

f r e c x e - u p i n 19SC-51 and 1~;-$2-53, t h e y e a r b s o f bad l~r~ealcuy;. L)u?<,-.lg 1.951-52 t h e r e was no s u r p l u s and o n l y abo-dt o n e - h a l f i n . o f s t o r a g e d u r i n g f r e e z e - u p . AltE-Lo~l.~h t h e f r e e z i n g i n d e x was a b o u t 1 0 p e r ; e r ~ . t above t h e a v e r a g e , no r o a d breakup o c c u r r e d . During 1 9 5 3 a w s t w

d e f i c i e n c y e x i s t e d u n t i l September l C t h arlci s t o r a g e d i d n o t b ~ i l d up a p p r e c i a ' l ~ l y u n t i l December. A s u r p l u s w a s ilot o b t e i n e d i ~ - n t l . l a f t e r f'resze-up. These ~ b s e r v a t ~ i o n s i n d i c a t e

z.

s ~ P s t a n t i a l 3 i f ' P e r e n . c . ~ : in water a v a i l a b i l i t y d u - r i n ~ th.e P a l l s e a s o n s whfc?~. p r e c e d e d t , h e . . _re.ic~irkably u;f'f e r e n t s p r i n g s e a s o n s .

The a v s i l a b i l . i t y of' w a t e r and its v a r i i a t i o n S.s n o t 5;el.l

u n d e y s t o o d . T h e r e i s no q v . e s t l . o n b ~ t t h a t i n rriost r e c - y i c n s

_Q

i t is

d e p e n d e n t on c l i n a t i c v a r i a t i o n b u t lnuch c o r r l e l a t % o n i s n e c a s s a q j t o 9 s t s b l i s ' n the r e l a t i c ~ s h i p between c l i m a t e and g r o u n d w a t e r tabll.s,

Measurement of grounilbaat. er 7-evels n e a r t h e B u l l d i n g He sear2.i-i Centraa

5.n Otta-ija show v a l u e s which are p1.obably t y p i c a l of Cl1.e r c + ~ ; l o n . A t the t i m e o f f r ~ e e z e - u p i n 1952, t h e gro.undrzrater t a b l s w L s l e s s t'csn one f t . 'below t h e s u r f a c e ; i i 2 1 9 5 3 i t w a s about

6

Tt,. b e l . 0 5 ~

t h e s u r f a c e . Alt1.1011g!3. G.O otl:ep a c t u a l r e c o r d s n.re available; t h e

Wates Re s o i . ~ r c e s D i v i s i o r : of' the G e o l o g i c a l Survey o f Canada co;lf i . ~ . ~ n s this t r e n d t h r o u g h o u t t h e Ottawa a r e a .

The a c c u m u l a t i o n a.nd d e c r e a s e of freezfng t , e n i p e r a t u r s s d..l.ring 1952-53 and 1953-5i: w i n t e r s e a s o n s i s csrapai-cd i ~ f ti: tl-ic norrrial i n Fi;;ure 7. It w i l l h e c c t i c e d . t l m t t h e ~ ~ : l . n t ~ e r o f

LS_S2-53,

a l t h c u g h mTld, exhibited no unx sl.lal f e a t u r e z . Z1he i~i-rlt er; s e a s o n beg2.n a b i t l a t e , ended e a r l y , t h s degree-da.y accurriulntion. befr,g

somewhat s l o w e r -than u s u ~ l . , a. s f t . u a t i o n t h o ~ q h t - to .favour P c e l e n s f rig. The w i n t e r of 19;'3.-5!4, ow ow eve^, iqas n o s t p e c u l . i a r . It b e g a n l a t e

b u t t h e t e n p e r u t u r e d l i r i n g J a n u a r y zn;l the f i r s t two wei:irs of

3'et:ruar;~ x a s u.nusu.all'\r c o l d c a u s l n g r a p i d a c c u m u l a t i o n of' d e g r e e - d a y s

w i t h mean d a i l y t e m p e r a t u r e s nearb f r e e z i n g . S i n c e t h e groundwater

t a b l e was low, much e x c e s s water i n t h e subgrwdes p r o b a b l y escaped d u r i n g t h i s p e r i o d . The w i n t e r ended w i t h a subsequent c o l d p e r i o d and. a l a t e ~ p r i n z , with p r a c t i c a l l y no road da~nage. It i s thought t h a t t h e p e c u l i a r a i r t e m p e r a t u r e s which o z c u r ~ ? e d a f t e r mid-Febr1:ary were r e s p o i l s i h l e f o r t h e i ' z i l u r e of t h e b r e ~ . l r u p i n d i c e s t o a s s e s s t h e s i t u a t i o n adequately.

D i s c u s s i o n

I n c o n s i d e r i n g t h e g,eneral problem of f r o s t a c t i o n a s

it

a f f e c t s t h e performance and maintenance of highways, two p r c b l e n s a r e paramount

--

pavement heaving and l o s s of s t r e n g t h d u r i n g s p r i n g thaw. Obviously f r e e z i n g a i r t e m p e r a t u r e s , a f r o s t - s u s c e p t i b l e s o i l and w a t e r a r e p r e r e q u i s i t e s f o r r o a d daxage, The s o i l c a n be

e l i m i n a t e d from t h i s d i s c u s s i o n of t h e e f f e c t of c l i m a t e s i n c e , i n g e n e r a l ,

i t

i s a f f e c t e d by c l i m a t e o n l y i n t h e p e d o l o g i c a l s e n s e and so can be assumed t o remain i n t h e same p h y s i c a l and mechanical s t a t e from y e a r t o year. A i r t e m p e r a t u r e , hcwever, needs c l o s e

n i t e n t i o n . I n r e g i o n s of d o n b t f u l f r e e z i n g danger, c l i m a t i c s t u d i e s such a s t h o s e of S o ~ ~ r w i n e arBe h e l p f ~ 1 1 i n p r e d i c t i n g t h e p o s s i b l e frequency and degree of damage.

In

c o l d e r rc:;ions, t h e r a t e of a c c ~ u n u l a t i o n of f r e e z i n g t e m p e r a t u r e s probably h a s g r e a t e f f e c t or: t h e d e p t h of f ' r o s t p e n e t r a t i ~ n and on t h e d e g r e e of i c e l e n s i n s I n

t h e s o i l . Consequently, i t a f f e c t s t h e amount of heave anti t h e p o t e n t i a l l o s s of s t r e n g t h d u r i n g breakup. The r a t e a t wh2ch t h e

f r o s t " l e a v e s t h e ground" must a l s o be of prime importance i n so f a r a s l o s s of s t r e n g t h i s concerned, A r a p i d thaw i s i n v a r i a b l y f o l ~ l o w e ~ ! by s e v e r e breakup, due t o t h e quick r e l e a s e of l a r g e amounts of water w i t h i n t h e upper p a r t of t h e s o i l which cannot escape

q u i c k l y , due t o t h e f r o z e n l a y e r s below. The q u a n t i t y of water r e l e a s e d d u r i n g breakup i s of course dependent on t h e amount of heaving and t o some e x t e n t on c o i n c l d e n t r a i n f a l l ,

Although i n t h i s study t h e freezinp; i n d e x i s i n c o r p o r c t e d i n t h e i n d i c e s of road breakup,

i t

i s e v i d e n t t h a t f a c t o r s o t h e r t h a n c o l d weather a r e extremely important i n causing r o a d f a i l u r e s d u r i n g s p r i n g thaw, e x c e p t i n rey;ions where t h e f r e e z i n g i n d e x i s o c c a s i o n a l l y e q u a l t o zero. It i s submitted t h a t t w o f e a t u r e s I n p a r t i c u l a r ~ r e a t l y i n f l u e n c e d thTs n o t a b l e d i l ' f e r e n c e i n breakup,

These two f e a t ~ r e s a r e a v a i l a b i l i t y of water and

--

r a t e of accumulat%on and d e c r e a s e of degree-days of f r e e z i n g . The d a t a quoted s u p p o r t

t h i s view. Dolch c i t e d c a s e s o f s e v e r e breakup

follow in^

v e r y m i l d w i n t e r s . A t b o t h Celgary and Ottawa f o l l o w i n g t h e e x c e p t i o n a l l y

m i l d w i n t e r of 1952-53, a "worse t h a n normal" road breakup occurr%ed. T h e r e f o r e a wide c o l l e c t i o n of c a s e h i s t o r i e s must b e made i f t-hs

f u l l e f f e c t o f a i r tempr:rature i s t o r:e understood.

The l a s t and p r o b a b l y most important v a r i a b l e i s water. It i s a much more complex v a r i a b l e t h a n temperabure s i n c e i t c c c u r s i n t h r e e phases and i t comes i n v a r i a b l e amounts, t h e u c i l i z a t i ~ n of which depends l a r g e l y oil season, c l i m a t e , d r a i n a g e , v k g e t a t i o n , ard s o i l type. Since t h e a v a i l a t r i l i t y of water a f f e c t s t h e degree of f r o s t l e n s i n g , t h e p o s i t i o n of t h e groundwater t a b l e i s importans. The g r o u n ~ l t r a t e r ta b l e i n t u r n depends on t h e above v a r i a b l e s . R

study of' Thgrnthwaite 1 s methods of d e a l i n g w i t h water u t i l i z a t i o n

h o w e v e r s n d c a n n o t , t h e r e f o r e b e e x p e c t e d to _{f i t o h e s e p u r p o s e s}

e x a c t l y . It j.s an a p p r o x i m a t i o n b a s e d on. averages. The assruned

s o i l m o i s t u r e s t o r a g e w i l l o b v i o u s l g v a r y 2 r e a . f l y d e p e n 6 i n g orL

s o i l t y p e . The degrJee o f c l o u d i n e s s and o t h e r v a r i a b l e s w i l ? . s f f a c t , t h e r e s u l t . N e v e r t h e l e s s , t h i s method i s

an

a t t e m p $ -to a s s e s s t h e a v a i l a b i l - 1 . t ~ o f i ~ a - t s r f o r p u r p o s e s o t h e r t h a r < vegt.'taLion and i t i s o n l y t i l i a e x c e s s w a t e r whi.cb. c a n c o n t r i b u t e t o f r o s t a c t i o n . As p r e v i o i n s l y m e n t i o n e d , t h e p r o b l e r ~ o f a s s e s s i n g r c h d b r e a k u p i s d j - f f i c u l t . A d j e c t i v e s ,

as

u s e d i n t h i s r e p o r t , ape, nct a d e q u a % e . Perba!)s a b r e a k u p c l a s s i f ' i c a t i a r i {:;an u e d ? v e l o p e d w h i c h

would alicta nlr3re d i r e s t c n r a p a r i soils w i t h weatb.er.. Other* p o s s i b l e

11

m e t h o d s o f evaluzitioi-1 i r l c l - ~ l d e p l a t e bearipia~;" tests, t h e C O S % of

r e p a i r s o r a com'cilnation of' m i l e s and c i u r a t i o n , o f r o a d b r e a k u p .

P l a t e b e a r i n ; ; t e s t ; ; a r e expej~sTve a n d t h e r e f o r e n o t made e x t e n s i v e l y b u t

i t

Tias heen. su:~ls;ested b y D r . N. W. McLaod t ' k a t t h i s t y p e o f

e v a l u a t i o n mag b e s t b e c a r r i e d o u t 7.1.sing t h e Beirkelman

Beam

Pavement.-. D e f l e c t i o n I n d i c a t , c r , Recent. t e s t s w i t h t h i s i.nstrul-cl~,nt (Carey

1954)

h a v e shown rmi.ch p r o n i s e i r ~ this ~ e g a r d .

h

examp1.e o f r ~ a d l-jr;eal;up e v a l u a t i o n b s s e d o n pavemen.?, m a i n t e n a n c e c o s t s b a s I..:een g i v e n by

O t i s (19-r,;2),

hut.

i.i? t h e c s . s e of t h e C a r a l e t o n Count.g s t u . d y +;his m e t h o d

w a s q u i t e u n r e l i a b l e , C o n c l u s i o n s

T h i s p a p e r i s an a t t e m p t t;o drahi 8 . t t e r ; t i o n t o ti?e n e c e s a i . ? : . ~

o f s t u d y i n g c l i m a t e i n c o n L l e c t i o n w i t h a n o r a c o m p l e t e ? r r ~ d e ~ ' ~ t n o d i n g o f f r o s t a c t i . o n i n s o i l s , Due t o t h e f a c k . t h a t a n e n t i r e gear i s

n e c e z s a r y f o r

the.

c o l l e c t i o n o f e a c h p i e c e of' evidence, r e l a . t i v e l y l i t t l e f ' i e ' i d d a t . a h a v e b e e n p r e s e n t e d . The f o l l o w i n g t e n t a t i v e c o n z l u s f o n : : n?a~g, h.owever., b e s t a t e d : :

L ) Ma:-iy- i r q c r t a n t v a r i z ~ ~ l e s whi.e'c affect f r o s t ; a.ct,ior:: niust, b?

n e ? . i s c t e d i n f i e l d s t ~ i j i e s b u t m u s t bcje c o j l s i d o r e d 2.71 fcl;fL--

ament.ul i n v o s t i g a t , i o n s ;

2 ) The effect or, f r o s t a c t i o z c f freeze-%'haw. z,ycli!y; 3::.

:it?

t

3m-,,erati.ires i s not. adec;~l;at b l y l r i ~ c ~ g n tjut 5.t h p p a a r s

;o

kl:i;:3

l i t t l e e f f e c t 011 -road. b ~ e a k u p ;

3 )

It i s i n c o r r l e c t (based o n

Sourwinets

w c r k )

tc

u s e va;-5aticri.s a b o v e an3 b e l o w

3 2 ' ~

a s a.i? i n d i c a t , i o n . of' f.'reezi.ng a:ld

thawin;; o f t h e s o i l . ; [I-) It i s ? o s s i b l e t o e s t a ' ~ l i s l i th e r e l a t i - v e d s ~ g e r o f gr.ound. f r e e z i n g o n t h e k a s i s o f weatheza r e c o r d s , "

5)

R e : ? i o n a l c l i m a t e caj-;.not b e a s s e s s e d o n t h e b a s i s o f ~ r e c ~ i p i t a t i o r l a n d t e ~ n p e r a t u r e o n l y , b u t m u s t a 1 . s ~ f n c l - u d e 3 c o ~ s i d e r a t i o n o f e v a p o ~ > a . t i o n f r o m

the

s a r f a c e a ~ d t r a n s p i r a t i o n froni v e g e t . a - t i o ~ g

6

) T h e r e p r o b a b l y e x i s t s a :If ~ e c t r o l a t i o l i s i i i ; , 'c etweelr. , ; Y D I J . ~ L ~ ~ -

wat.er t a b l e and t h e colnbii~ed ef'f e c t o f p ~ c ~ . L p 4 t ; a i : , io:.: e - v ~ . p o l - a t f o n and z r a n s p i r a a t i o n g

7 )

I11 n o r t h e r r i r e g i o n s . ~ l l e r e a n n u a l f ' r e e z k i ~ ~ ~ a l w a y s c c c i l r s ,

a.

t h e s l o p e o f t h e f r e e z i x g i ~ z d e x c.urve p r o ~ a b - i y :;as X ~ I ~ , P

e f f e c - t t h a n the absolu4cre v a l u e o f t h e index o n frcsc

damage t o raoads; and

8 )

R e c e n t t h e o r i e s r e l a t i n g p-rec l p i t a t i c f n ai?ci x a t e r u t i l i za..i.ion. show much p ~ o m i s e f o r t h e e-valua!;ion o f s u b s r e . d e nc!is-bu~r-

I n

t h e g e n e r a l a p p r o a c h t o u n d e r s t e n d i n g f r o s t .:tction t h e phenomena must b e s t u d i e d

i n

t h e l a b o r a t o r y a s w e l l a s by s t u d i e s i n t h e f i e l d . Problems s u c h a s t h e r o l e of moisture move.l:l,silt and t h e c r i t e r i a f o r f r o s t SI, s c e p t i b l e s o i l s r e i y i r e i ' ~ m d a m e n t ; > l s t u d i e s ,

Even i f t h e s e phenomena were c o m p l e t e l y u n d e r s t o c ~ d , 1-iighwa.y e n g i n e s r s would s t i l l b e b a f f l e d by t h e w e a t h e r . It i s an a c c e p t e d f a c t ?;hat p a v e ~ ? l e z ~ t s c a n b e d e s i s u e d agaill-st f r o s t a.ctio:l i n sny c l r l n a t e but

f o r minimum d e s i g n f o r a l l c l a s s e s of roadway a n o r e c o m p l e t e

e v a l u a t i o n i s n e c e s s a r y . F o r t h i s e v a l u a t i o n , r.~'nat h a p p e n s i n t h e f i e l d must b e u n d e r s t o o d a n d , f o r t h i s , c o n s i d e r a t i o n of c l i m a t e i s

a b s o l u t e l y e s s e n t i a l , With s u c h

ax!

u n d e r s t a n d i n g , it c a n b e !.:.oped t h a t a c c u r a t e f ' o r e c a s t i n g of t h e a m o t ~ n t o f h e a v e , t h e (luration 2nd

t h e d e g r e e of s p r i n g b r e a k u p and t h u s impToved r o a d - m y d e s i g n . i . . ; - i l l

f o l l o w .

Acknowledgements

I n a d d i t i o n t o t h e i r a s s o c i a t e s , t h e a u t h o r s c r a t e f u l l y acknowledge t h e a s s i s t a n c e o f Dean R. M. Hardy, U n i v e r s i t y of A l b e r t a ,

i n

a s s e s s i n g t h e r o a d damage

i n

A l b e r t a and o f N r . Alex

J.

Graham, C a r l e t o n County E n g i n e e r , f o r h i s c o m p l e t e a ~ s i s ' c a r i c e i n t h e s t u d i e s o f t h e Ottawa a r e a . S p e c i a l a p p r e c i s c i o n i s due t o Mr. R o o e r t F. L e g g e t , whose p e r s o n a l i n t e r e s t i n c l i m a t e and b u i l d i n ? prompted t h i s s t u d y . T h i s p a p e r i s p r e s e n t e d w i t ; ; t h e a y p r o v a l of M r . Andrew Thonson, C o n t r o l l e r of t h e M e t e o l - o l o y i c a l D i v i s i o n , Department o f T r a n s p o r t , and M r . R. P. L e g z e t , D i r e c t o r , D 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 , N a t i o n a l R e s e a r c h C o u n c i l . B i b l i o g r a p h y B e l c h e r

,

D,

J.

-

"Subgrade S o i l ~ e m p e r a t u r e s t \ P ~ r o c e e ( l i n g s , Purdue C o n f e r e n c e o n S o i l Mechanics and i t s a ~ p l i c a t i o n s , Purdue U n i v e r s r i t y , pp

474-l+82,

September, 194.0. Benkelman, A,C. and O l r s t e a : l , P r a n k R ,

-

"A n e x Theory o f F r o s t Heaving". P r o c e e d i n g s , Hizhway R e s e a r c h Board, Vol. 11 pp 1 5 2 - 1 6 5 , 1931.

Carey, W.N.

-

" ~ e n k e l r n a n Seam Pavement

-

D e f l e c t i o n I n d i c a t o r " , Highway R e s e a r c h A b s t r a c t s , Vol.

23,

No.

8,

pp

1-4,

Septe:r.ber, 1954.

C a s a g r a n d e , A

-

" D i s c i i s s i o n o n F r o s t tleavin,;". P r o c e e d i n g s ,

Highway R e s e a r c h Bocrd, Vol. 11, pp l!i8-l72, 1931. C o r p s of E n g i n e e r s

-

l t ~ e p o r t on F r o s t I n v e s t i ~ a t i o n !-941C-131j.3",

New England D i v i s i o n , Corps of E ~ : < i n e e r s , B o s t o n , Mass. A p r i l 19!!7,

Crawforri, C a r l

B.

-

o oil

T e m p ~ r : ~ t u r ~ s

-

A Rq-; e v o f P i ~ b L i . s ; ~ e d

Recor*dsl*. Symnosiirm or, F'rw s t Act isr- i n S o i l r .

Hishrpra 3osearc1-1 Board S p e c i a l Heport, N o . 2 ,

pp 17-$1. 19!:2,

Dolch, M.L.

-

"A S u r - ~ e ; ~ o f ?dint e r Wcs_t.her

-

I n d j - a n a , 193[;-,19S1". P r e l i m i n a r y R e ~ g r t , PurCue University,

i i l

p a g e s , September 19-52,

Eno, F.H.

-

"The I n f l u e n c e of C l i m a t e on t h e B u i l d i n g Maintenance and Use o f Roads i n t h e United. ~ . t a t e s " . P r o c e e d i n g s , Highway R e s e a r c h Board, Vol. 9 , p p 216-223, 1924. Hardy, R,M.

-

" ~ o n s t r u c t i o n Problems i n S i l t y ? o i l s n , The

E n g i n e e r i n s J o u r ~ ~ a l , Vol. 33, No. 9, py) 7'75-779s September 1950.

Johnson, A.W.

-

" F r o s t A c t i o n i n Roads and A i r f i e l d s

-

A Fiaview o f t h e ~ i t e r a t ~ l r e ~ ' , Highiray R e s e a r c h Board, Special

R e p o r t No. 1, 287 p a 2 e s , 1952.

Leg.?et, R.F. and Crawford, C.B.

-

" S o i l T e m p e r a t u r e s i n

Water

Works

P r a c t i c e " . J o u r n a l of t h e American Water Works

A s s o c i a t i o n , Vol.

1;-4,

No. 1 0 , pp 923-9399 Cctobea*? 1952. Beskow, G.

-

11 S o i l F r e e z i n g and F r o s t Heaving wLth S p e c i a l

A p p l i c a t i o n t o Roads and

ailr roads".

Swedish

G e o l o g i c a l S o c i e t y , S e r i e s C , 110. 3 7 s s 1 9 3 5 w i t h a s p e c i a l supplement f o r t h e E n g l i sll. t r a r l s l n t i o n of'

p r o g r e s s f r o m

1935

t o 1911.6. l d o r t h w e s t e r n U n i v e ~ s i t g T e c h n o l o g i c a l I n s t i t u t e , Novemt)er 1947, ( T r a n s l a t e d by J.0. ~ s t e r b e r g )

O t i s , P a u l S.

-

h he

N a t u r e and E x t e n t o f Darnase t o New Hampshire Highways f r o m F r o s t ~ c t i o n " . Symposium on F r o s t A c t i o n i n S o i l s . Higliway R e s e a r c h Board S p e c i a l R e p o r t No, 2, pp 268-274, 1952. S a n d e r s o n , Marie

-

" M o i s t u r e E i e l a t i o n s h i p s i n S o u t h e r n ~ n t a r f o ' ~ . S c i e n t i f i c A g r i c u l t u r e , Vol. 3 0 , pp 235-255, June 1950. Shannon, W.L.

-

" P r e d i c t i o n o f F r o s t ~ e n e t r a t i o n " , J o u r n a l , New England Water Works A s s o c i a t i o n , Vol. 5 9 ,

No.

4,

pp 356-363, December 19115.

Sourwl le, J.A.

-

i is cuss ion

o n t h e I n f l u e n c e o f C l i m a t e on t h e B u i l d i n g , Maintenance and Use o f Roads i n t h e U n i t e d s t a t e s " . P r o c e e d i n g s , Highway R e s e a r c h

Board, Vol

9 ,

pp 243-248, 1929,

So~xrwine, J.A.

-

"A Method of A n a l y s i s of Data o n F r o s t O c c u r r e v ~ c e f o r Use i n Highway ~ e s i g n " . P u b l i c Roads, V o l . 11,

No.

3,

pp 51-60, May, 1930.

T a b e r , S.

-

" F r o s t Heaving1'. J o u r n a l of Geology,, Vol. 37,

No.

5,

pp 428-461, J u l y

-

August, 1929.

T h o r n t h w a i t e , C. W.

-

"An Approach Toiqard a R a t i o n a l C l a s s i f

f

c a t i o n o f ~ l i m a t e " . The G e o g r ~ a p h i c a l Heview, Vol.

38,

No. 1, pp 55-911-, 1948.

TABLE

I

( V F \ C . Q r - D

o

o

m

o

D J a S.\ CP F