On the Construction of Snow Fences

Publisher’s version / Version de l'éditeur:

Technical Translation (National Research Council of Canada), 1963

READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.

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

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 PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.

Questions? Contact the NRC Publications Archive team at

PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.

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/10.4224/20331399

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

On the Construction of Snow Fences

Dyunin, A. K.; Komarov, A. A.

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.

NRC Publications Record / Notice d'Archives des publications de CNRC: https://nrc-publications.canada.ca/eng/view/object/?id=c71f8698-ed1b-4c50-ac2a-22d7ccf929e3 https://publications-cnrc.canada.ca/fra/voir/objet/?id=c71f8698-ed1b-4c50-ac2a-22d7ccf929e3

PREFACE

Snowdrifts can be

a

major s o u r c e of d i s r u p t i o n i n t h e o p e r a t i o n of t r a n s p o r t a t i o n s e r v i c e s and

a

g e n e r a l nuisance i n t h e normal

wintertime a c t i v i t y of e comrriunity. Such d r i f t s a r e formed whenever a wind, s t r o n g enough t o t r a n s p o r t h o r i z o n t a l l y a s i g n i f i c a n t amount of snow, encounters an o b s t a c l e which f o r c e s i t t o d e p o s i t some of t h i s snow. The u s u a l approach t a k e n i n defending an a r e a o r s t r u c - t u r e a g a i n s t s n o w d r i f t i n g has been t o l o c a t e t h e s t r u c t u r e p r o p e r l y s o t h a t t h e d r i f t problem w i l l be a minin~um and t o e r e c t o b s t a c l e s , such a s snow f e n c e s , t o c o n t r o l where t h e snow w i l l be d e p o s i t e d . The approach t a k e n i n t h e development of t h e s e defences has been l a r g e l y e m p i r i c a l . A t t e n t i o n has been d i r e c t e d p r i m a r i l y t o t h e c h a r a c t e r of t h e a i r flow with l i t t l e a t t e n t i o n b e i n g given t o t h e m a t e r i a l t r a n s p o r t e d .

In

some circumstances, i t would be an advan- t a g e t o have a more complete defence a g a i n s t s n o w d r l f t l n g than i s now a v a i l a b l e . In t h e i r a t t e m p t s t o develop t h i s defence, e n g i n e e r s a r e g i v i n g more c o n s i d e r a t i o n t o t h e t h e o r e t i c a l a s p e c t s of t h e problem and i n p a r t i c u l a r t o t h e r e l a t i o n s h i p s between t h e a i r flow and t h e snow being t r a n s p o r t e d .

It i s one of t h e r e s p o n s i b i l i t i e s of t h e Snow and I c e S e c t i o n o f t h e D i v i s i o n o f B u i l d i n g Research t o c o l l e c t and make a v a i l a b l e information r e q u i r e d f o r t h e s o l u t i o n of snow and i c e problems. The p r e s e n t paper, t r a n s l a t e d from t h e Russian, i s a c o n t r i b u t i o n t o t h e t h e o r y of s n o w d r i f t i n g . T h i s paper w i l l g i v e t o t h e r e a d e r an

a p p r e c i a t i o n of some of t h e f a c t o r s t o be considered i n t h e t h e o r e t - i c a l d e s c r i p t i o n of blo\iing snow and

i t s

d e p o s i t i o n a s s n o w d r i f t s .

The p a p e r was t r a n s l a t e d by M r . G. Belkov of t h e T r a n s l a t i o n s S e c t i o n of t h e N a t i o n a l Research Council L i b r a r y , t o whom t h e D i v i s i o n of B u i l d i n g Research wishes t o r e c o r d i t s thanks.

Ottawa R.F. Legget

NATIONAL RESEARCH COUNCIL

OF

CANADA

T e c h n i c a l T r a n s l a t i o n 1103

T i t l e : On t h e c o n s t r u c t i o n o f snow f e n c e s ( 0 k o n s t r u k t s i i snegovykh s h c h i t o v )

Authors : A . K . Dyunln and A . A . Komarov

Reference: Trudy Transportno-Energeticheskogo I n s t i t u t a , ( 4 ) : 111-118, 1954

ON TIM CONSTRUCTION OF SNO1.I FENCES

S umrnary

T h i s r e p o r t n o t e s t h e d e f e c t s of e x i s t i n g snow f e n c e s and a sound argument i s p r e s e n t e d f o r lrrlproving t h e c o n s t r u c t i o n of f e n c e s w i t h reduced d e n s i t y of t h e lower p a r t and which do n o t have t o be moved s o o f t e n .

Movable f e n c e s a r e w i d e l y used on r a i l r o a d s i n t h e S o v i e t Union and

p a r t i c u l a r l y on t h e r o a d s o f Western S i b e r i a where more t h a n 50$ of t h e t o t a l

p l a c e s s u b j e c t t o d r i f t s a r e p r o t e c t e d by them l 9

.

T h e r e f o r e t h e q u e s t i o n of Improving t h e c o n s t r u c t i o n of e x i s t i n g movable f e n c e s Is of g r e a t

importance.

Snow f e n c e s were i n v e n t e d 90 y e a r s ago by t h e Russian e n g i n e e r , V.A. T i t o v . Attempts by a number of s p e c i a l l s t s t o make improved t y p e s of f e n c e s were u n s u c c e s s f u l and t h e c o n s t r u c t i o n of s t a n d a r d f e n c e s a t t h e p r e s e n t time d o e s n o t d i f f e r e s s e n t i a l l y from t h o s e which were used i n t h e s e v e n t i e s of t h e

l a s t c e n t u r y .

One o f t h e d e f e c t s of s t a n d a r d f e n c e s ( ~ i g . 1) i s t h e i r s m a l l snow- g a t h e r i n g a b i l i t y b e f o r e t h e y a r e moved f o r t h e f i r s t time, b e i n g 25

-

30

m3/pm+ when t h e wind i s p e r p e n d i c u l a r t o t h e f e n c e . A g r e a t d e f e c t of l a t t i c e - t y p e f e n c e s Is t h a t t h e y a r e u n r e l i a b l e f o r p r o t e c t i n g r o a d s from s n o w d r i f t s . During s t r o n g wlnds t h e f e n c e s a r e f i l l e d i n d u r i n g one o r two b l i z z a r d s and

sometimes even a f t e r e e v e r a l h o u r s , which c o n s t i t u t e s a danger f o r r o a d s where c o n t i n u o u s t r a f f i c i s r e q u i r e d . The moving of f e n c e l i n e s d u r i n g a b l i z z a r d i s e x c e e d i n g l y d i f f i c u l t and sometimes i m p o s s i b l e .

The r a p i d f i l l i n g i n of t h e f e n c e i s e x p l a i n e d by t h e f a c t t h a t t h e peak of t h e s t e e p snow vrall forlned behind t h e f e n c e l i n e i s I n d i r e c t p r o x i m i t y t o t h e f e n c e ( F i g . 2 ) .

In o r d e r t o p r o l o n g t h e time t a k e n t o f i l l i n t h e fence one h a s t o "move" t h e snow w a l l away from t h e f e n c e l i n e . On t h e b a s i s of simple t h e o r e t i c a l c o n s i d e r a t i o n s one can e a s i l y f o r m u l a t e c o n d i t i o n s which would f u l f i l l t h i s requlrernent

.

F o r s o l v i n g t h e problem posed we use t h e formula found by means o f dimensional a n a l y s i s f o r d e t e r m i n i n g t h e weight of snow f l u x I n a u n i t of

T r a n s l a t o r ' s n o t e :

tirne ovel* a u n i t o f f r o n t l e n g t h o f t h e f e n c c

:*

where

Jr

-

t h e c o e f f i c i e n t whicl? is, g e n e r a l l y s p e a k i n g , v a r i a b l e . F o r average, most p r o b a b l e c o n d i t i o n s , i t can be c o n s i d e r e d c o n s t a n t and e q u a l t o

.

sec2 0 . 2 5 5 & v,

-

t h e averaged t r a n s l a t i o n a l v e l o c i t y of t h e wind a t t h e h e i g h t o f 1 m i n d s e c . v P

-

c r i t i c a l v e l o c i t y i n d s e c a t a h e i g h t of 1 m which f o r l o o s e snow blown by t h e wind i s e q u a l t o 2 . 7 1 d s e c .

The main f a c t o r i n f l u e n c i n g t h e magnitude o f t h e snow f l u x i s t h e l o n g i - t u d i n a l s u ~ f a c e v e l o c i t y of t h e wind. T h e r e f o r e t h e main c h a r a c t e r i s t i c s of a snow f e n c e ~ n u s t be c o n s i d e r e d t o be t h e curve of r e d u c t i o n i n s u r f a c e wind v e l o c i t y i n t h e a r e a where t h e f e n c e 1s e f f e c t i v e . Such a curve f o r any new c o n s t r u c t i o n o f a snow f e n c e can be o b t a i n e d frorn s i m p l e f i e l d wind measure- ments o r by u s i n g a n a p p r o p r i a t e model i n a wind t u n n e l . In a n a l y z i n g t h e s e c u r v e s one should be governed by s p e c i f i c c o n d i t i o n s . For t h e f i r s t l e t u s c o n s i d e r t h e c o n d i t i o n s r e l a t e d t o t h e a b i l i t y of t h e f e n c e t o r e s i s t b e i n g f i l l e d i n .

I f t h e f i e l d v e l o c i t y of t h e wind i n f r o n t of t h e f e n c e i s e q u a l t o w and behind t h e f e n c e t o v, i n t h e a r e a p r o t e c t e d by t h e f e n c e f o r each u n i t of time and f o r each u n i t of width of t h e f e n c e , a c c o r d i n g t o formula ( l ) , t h e f o l l o w i n g amount of snow w i l l be d e p o s i t e d ( u n d e r t h e same i n i t i a l c o n d i t i o n s ) :

I f one knows t h e e q u a t i o n o f t h e curve showing r e d u c t i o n i n wlnd v e l o c i t y v = f ( 1 ), where 1 i s a l e n g t h p l o t t e d from a n a r b i t r a r y p o i n t on t h e s u r f a c e of t h e ground p a r a l l e l t o t h e wind, one can r e a d i l y determine t h e i n c r e a s e i n t h e h e i g h t of t h e snow d e p o s l t Ah f o r a u n i t of time a t any p o i n t o f t h e a r e a p r o t e c t e d by t h e f e n c e :

where o

i s

t h e d e n s i t y of t h e snow d e p o s i t i n d m 3 .

The l o c a t i o n o f t h e maximum a c c r e t i o n o f snow o f t h e i n i t i a l snow

d e p o s i t , 1 . e . t h e l o c a t i o n of t h e peak o f t h e snow w a l l forrned a t t h e begin- n i n g o f snow d r i f t i n g ; can be determined from t h e e q u a t i o n :

*

See p a p c r by A . K . Dyunin " s o l i d f l u x o f snow-bearing a i r flow" (NRC TT-1102).

hcnc c

d7v dl=

- - . - . .

.

v - - 0 '

(3

1

Thc c a s e v - v ' = 0 corrcsponcls t o Lllc rnlni~~~unr Ah slncc- when v = v f snow t r a n s f c r i s e q u a l t o 0 accordin:-: t.o t h e d e f l n l t i o n ol' thi-! c r i . t i c n 1 v e l o c i t y v f .

A t t h e p o i n t of' t h e i i ~ a x l r n ~ l ~ l o f A l l , v s h o u l d a l w a y s b c grr:ater. t h a n v '

.

C o n s e q u e l ~ t l y ti l c s e c o n d d e r i v a t i v e o f v o v e r 1 1s e s s c 2 n t i a l l y a ncy_r,atlve v a l u e . T h e r e f o r e t h e peak o f t h e nnow naI.1 wou1.d corr.cspond t o t h e corlvcx p a r t of t h e culnvc 1 - c p r c s c n t i n y ; thc: d e c r c a s c i n v e l . o c i t y f r o m t h e p o i . n t o f i n l t i a l d e c r e a s e t o t h e p o i n t o f i t s l n f l c x i o n whlch i s l?ppro;:llnately a t a d i s t a n c e o f 2 n i c t r e s fro111 a s t a n d a r d f e n c e ( ~ l g .

3 ) .

I n f a c t t h e p e a k o f t h e snow w a l l forrirs sorlle- v h a t f u r t h e r fro111 th e f e n c c (Fri.g. 2), rlllich apparently Is e x p l a i n e d b y a

n u ~ n b e r o f o t h e r f a c t 0 r . s n o t t a k e n i n t o accourit by for1rrlula

( 3 ) .

Hence i t f o l l o w s t h a t w i t h a rnoi>c g e n t l e s l o p e o f t h e c u r v e r e p r e s e n t l n g d e c r e a s e i n wind v e l o c i t y , t h c wal.1 forins f a r t h e r fro^,^ t h e f e n c e . T h l s i s t h e funclarrlental c o n d i t i o n i n d e s i g n i n g snow f e n c e s t h a t w i l l n o t b e f i l l e d i n .

The s e c o n d c o n d i t i o n I n v o l v e s t h e g r e a t e s t p o s s i b l e d e c r e a s e I n wind v e l o c i t y beyond t h e f e n c e . L e t v i n fo:c'l;lula ( 2 ) corlrespond t o t h e p o i n t of maximum d e c r e a s e I n v e l o c i t y . L e t u s dc!terniSne t h e v a l u e o f v f r o i : ~ t h e c o n d i t i o n of rriaxirnum i n i t i a l snow d e p o s i t i o n , dAQ

-

= - 3+ ( v - v f ) ?

=

0 dv h e n c e v - - - Vmln=v'

.

The u p p e r l i r n i t o f t h e mininlurn possible v e l o c i t y i s , d e f i n e d by what p e r c e n t a g e o f snow t r a n s f e r i l e d beyond t h e l i r ~ ~ i t s of' !,he zone a f f c c t e d by t l z c

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

.

U::ually i n engineering calculations

e r r o r s of t h e o r d e r o f

57:

a r e n e g l e c t e d . Thus i f one c o n s i d e r s a snow f e n c c t h a t d e c r e a s e s snow f l u x by at l e a s t t h e f a c t o r o f 2 0 t o b e e f f i c i e n t , t o d e f i n e t h e u p p e r limit o f vrcin VE h a v e t h e i r l e q u a l i t y f o l l o w i n g f'ror,l fopmula

h e n c e

A s s u n i n g

vmin a t v a r i o u s v a l u e s o f wind v e l o c i t y w . T a b l e I g i v e s t h e p a t i o o f

-

I'J

Assume t h a t t h e a v e r a g e vlilin <

0 . 5 w.

Cor,~billing t h i s c o n d i t i o n '11th t h e one o b t a i n e d e a r l i e r vjLlin = v ' , we w i l l have f o r t h e d e f i n i t i o n o f thc. n ~ i n l r n u ~ i ~ v e l o c i t y o f t h e s u r f a c e wind beyond t h e f e n c e t h r f o l l o v i i n g Inequality

T h i s i s t h e second c o n d i t i o n i n d c s l g n i n g an c f f l c l c n t snow f e n c e . I n t h i s paper we w i l l 1 - e s t r i c t t h e cliscussion t o t h c s e two c o n d i t i o n s which a r c colru,ion t o a l l t y p c s of f e n c e s . A s can bc s e e n from P i g .

3 ,

i n u s i n g normal s t a n d a r d f e n c e s o n l y t h e second c o n d i t i o n i s observed, and v _min i s e q u a l t o 30

-

35:;

of t h e f i e l d v c l o c l t y , 1 . e . c o n s i d e r a b l y l c s s t h a n

0.5

w .

Tllc cullve of t h c s u r f a c e v e l o c i t i e s r i s e s s h a r p l y a t t h e f e n c e l i n e and

a s

a r e s u l t t h e peak o f t h e i n i t i a l snow d e p o s i t i o n i s Loo c l o s e t o t h e f e n c e and t h e f e n c e Is q u i c l t l y f i l l e d i n ( s e e Fie;. 2 ) .

J h t e l * e s t i n g s u g g e s t i o n s p u b l i s h e d r e c e n t l y by t h e Snow C o n t r o l

Laboratory of TsNII MPS and by

P.I.

S a r s a t s k i l c h , r e s e a r c h worlcer a t DorNII ( r e f . 1 , 2 , 6 ) i n d i c a t e a way o f nrecting t h e second c o n d i t i o n .

The Snob! C o n t r o l Laboratory of TSNII suggested r a i s i n g a normal f e n c e by a h e i g h t of 0 . 5 m above t h e s u r f a c e of t h e ground. T h i s measure g r e a t l y i n c r e a s e s t h e ~ c l n e t l c energy of t h e s u r f a c e s t r a t u m o f wind d i r e c t l y beyond t h e f e n c e and c o t ~ s e q u e n t l y r e s u l t s i n f l a t t e n i n g of t h e c u r v e of r e d u c t i o n i n v e l o c i t y . On t h e b a s i s of e x p e r i m e n t s i n p l a c i n g models of e l e v a t e d f e n c e s i n a w i n d t u n n e l a t t h e Transport-Power I n s t i t u t e o f t h e West S i b e r i a n F i l i a l o f t h e Academy of S c i e n c e s i t h a s been e s t a b l i s h e d t h a t t h c second c o n d i t i o n i s s a t i s f i e d i f t h e f e n c e i s r a i s e d by n o t nlor'e t h a n

0 . 5

m.

Thus t h e sugges- t i o n o f TsNII f u l l y c o r r e s p o n d s w i t h t h e c o n d i t i o n s o f d e s i g n i n g snow f e n c e s which e x p l a i n s t h e good r e s u l t s of f i e l d experiments ( 2 )

Experimental o b s e r v a t i o n s c a r r i e d o u t by u s on t h e Toii~sk R a i l r o a d showed t h a t t h e reconuriendations of TsNII J u s t i f i t . d themselves c o m p l e t e l y . However, t h e e l e v a t i o n o f t h e f e n c e h a s an e f f e c t o n l y up t o t h e time of t h e f i r s t movetilent o f t h e f e n c e a f t e r which i t i s talcen o f f t h e p o s t s and s u b s e q u e n t l y o p e r a t e s a s

a

s t a n d a r d f c n c e . To r e t a i n t h e e f f e c t of a n e l e v a t e d f e n c e I n a h e a v i l y d r i f t i n g r e g i o n can o n l y be done w i t h h i g h p o s t s vrhich would p e r m i t a g r a d u a l l i f t i n g of t h e f e n c e a s i t i s b e i n g f i l l e d i n , always l e a v i n g an open space underneath

.

From t h e same c o n s i d e r a t i o n s one can a l t e r t h e c o n s t r u c t i o n of t h e f e n c e by d e c r e a s i n g t h e d e n s i t y of i t s lower p a r t .

T h i s was t h e approach t a k e n by engineel- P . I . S a r a t s k i k h who s u g g e s t e d a f e n c e f o r p r o t e c t i n g automobile r o a d s w i t h h o r i z o n t a l s l a t s and v a r i a b l e d e n s i t y which I n c r e a s e s w i t h h e i g h t . But t h i s type of f c n c e h a s n o t been widely used because It i s n o t s t a b l e and f r e q u e n t l y t h e h o r i z o n t a l s l a t s

b r e a k p a r t i c u l a r s l y t h e lovrer s l a t s , when t h e y a r c b e i n g removed from t h e

( 4 )

snow

.

!1e s u g g e s t a d i f f e r e n t c o n s t r u c t i o n o f f c n c c w i t h v e r t i c a l s l a t s and d e c r e a s e d d e n s i t y of t h e lower p a r t ( p i g . [I).

The suggested f e n c e d i f f e r s frorn t h e s t a n d a r d i n t h a t e v e r y second

v e r t i c a l s l a t i s c u t off _{i n t h e middle ancl t h e lower ends a r e f a s t e n e d t o two}

a d d i t i o n a l h o r i z o n t a l s l a t s 1 m i n l e n g t h .

Models of such f e n c e s were t e s t e d i n wind t u n n e l s and

i t

was e s t a b l i s h e d t h a t t h e c u r v e r e p r e s e n t i n g t h e d e c r e a s e i n v e l o c i t y h a s a more g e n t l e s l o p e i n comparison w i t h t h e curve f o r a s t a n d a r d f e n c e . Here t h e minimur;~ s u r f a c e v e l o c i t y beyond t h e f e n c e does n o t cxcced

45

-

48%

of t h e open f i e l d

v e l o c i t y ( ~ i g .

3 ) ,

1 . e . i n e q u a l i t y ( 4 ) i s f u l f i l l e d .

During t h e w i n t e r of 1952-53 i n an e x p e r m e n t a l p o r t i o n o f t h e Tomsk R a i l r o a d o b s e r v a t i o n s were c a r r i e d o u t on t h e o p e r a t i o n of t h e f e n c e s . On a n open a r e a p e r p e n d i c u l a r t o t h e d i r e c t i o n of t h e p r e v a i l i n g wind two l i n e s of f e n c e were s e t up

-

one b e i n g a s t a n d a r d f e n c e and t h e second having reduced d e n s i t y i n t h e lower p a r t . The r e s u l t s o f o b s e r v a t i o n s a r e shown i n F i g .

5

and Table 11.

The f e n c e s were s e t up i n t h e middle of'December 1952 and were n o t moved t i l l t h e end o f w i n t e r . The wind v e l o c i t y reached 12

-

13 d s e c a t a h e i g h t of 1

m.

A s can be s e e n from F i g .

5

and T a b l e

I1

t h e volume o f snow d e p o s i t e d beyond b o t h t y p e s o f f e n c e s was a p p r o x i m a t e l y t h e same b u t t h e i r o p e r a t i o n was q u i t e d i f f e r e n t . Whereas w i t h a normal f e n c e i n January of 1953 nore t h a n a t h i r d o f t h e h e i g h t was f i l l e d i n and r e q u i r e d immediate moving o f t h e fence, t h e f e n c e w i t h t h e reduced d e n s i t y i n t h e lower p a r t was n o t f i l l e d i n by t h e end of w i n t e r . The peak o f t h e scow w a l l was more t h a n twice a s f a r from t h e f e n c e a s t h a t o f t h e s t a n d a r d f e n c e and t h e t o t a l snow d e p o s i t reached 94 m3/ pm w i t h o u t

i t

b e i n g n e c e s s a r y t o move t h e f e n c e .

In a d d i t i o n t o t h e volume of snow d e p o s i t e d and t h e manner i n which t h e f e n c e i s f i l l e d i n , t h e r e i s some i n t e r e s t a l s o i n t h e q u e s t i o n of t h e amount o f snow t r a n s f e r r e d beyond t h e l i m i t s a f f e c t e d by t h e f e n c e . S p e c i a l b l i z z a r d m e t e r i n g o b s e r v a t i o n s were c a r r i e d o u t a t a d i s t a n c e o f

17

and 27 m from t h e f e n c e lLne and

i t

was e s t a b l i s h e d t h a t t h e f l u x of snow beyond t h e f e n c e was d e c r e a s e d on t h e average by a f a c t o r of 2 0 f o r b o t h t y p e s of f e n c e s .

In o r d e r t o f i n d t h e amount o f snow t r a n s f e r r e d beyond t h e a r e a a f f e c t e d by t h e f e n c e d u r i n g t h e f o r m a t i o n o f t h e snow w a l l on March 10, 1953, a con- t r o l l i n e c o n s i s t i n g o f s t a n d a r d f e n c e was s e t up a l o n g s i d e t h e l i n e o f new f e n c e . It was found t h a t by March

25

t h e c o n t r o l f e n c e c o l l e c t e d 25 m3 o f snow p e r pm which i s a p p r o x i m a t e l y e q u a l t o t h e d i f f e r e n c e between t h e snow d e p o s i t i o n on March 25 and Iwlarch 10 behind t h e e x p e r i m e n t a l snow f e n c e l i n e s . Consequently t h e amount o f snow t r a n s f e r r e d beyond t h e zone a f f e c t e d by t h e f e n c e d i d n o t v a r y e s s e n t i a l l y towards t h e end o f w i n t e r by comparison w i t h t h e i n i t i a l p e r i o d o f o p e r a t i o n o f t h e f e n c e .

The f e n c e d e s i g n w i t 1 1 decreased d e n s i t y I n t h e lower p a r t and c o n s i s t i n g of v e r t i c a l s l a t s

i s

~ t ~ u c h s t r o n g e r and nlore s t a b l e than t h a t suggested by P . I . Sarsatskilch, however t h e y a r e n o t a 3 s t r o n g i n t h e i r r e s i s t a n c e t o bend- i n g alone; t h e v e r t i c a l p l a n e a s t h e s t a n d a r d f c n c e . Let us deterinine t h e rrlaxl~rlum wind v e l o c i t i e o a t t h c s u r f a c e a t which one can use t h e new type of fence without reinfoi-cement

.

For c a l c u l a t i n g t h c normal f o r c e component of t h e wind we used t h e formula of A . A . B o g o r o d e t s b i l ( 3 ) , whlch t a k e s i n t o account t h e shock e f f e c t of t h e wind,

where k

-

c o e f f i c i e n t o f t h e d e n s i t y o f t h e f e n c e contour which i n o u r c a s e was taken t o be 0.5 f o r t h e upper h a l f of t h e fence and 0.25 f o r t h e

lower h a l f ;

F

-

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

i t s

o u t e r contour; p

-

mass d e n s i t y o f t h e a i r

0.37

kc; aec2

m4

when T = -lO°C and a t i m s p h e r i c p r e s s u r e i s 750 nun;

v

-

mean vrlnd v e l o c i t y whlch t o r e t a i n a s a f e t y f a c t o r w e assumed t o be e q u a l a l o n g t h e e n t i r e contour and b e i n g e q u a l t o t h e mean v e l o c i t y a t t h e h e i g h t of 1

m.

The r e s i s t a n c e moment of t h e fence i s

where n i s t h e number of lower v e r t i c a l s l a t s , b and h a r e t h e width and t h i c k n e s s of t h e s l a t s .

The moment arms a r e determined from t h e l o c a t i o n of c e n t r e s of g r a v i t y &f t h e upper and lower h a l v e s of t h e fence ( 1 . 5 n and

0.5

m )

without tak1n.g i n t o account t h e depth t o which t h e fence i s i n r ~ ~ e r s e d i n t h e snow.

Let us assuine n =

7,

b = 0.07 m and h = 0.015 rill.

Then t h e rnaximur~~ normal bending s t r e s s f o r t h e lower p a r t of each v e r t i - c a l s l a t running t h e f u l l h e i g h t of t h e f c n c e v ~ i l l be

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

Consequently a fence with reduced d e n s i t y I n t h e lower p a r t i s weaker than a s t a n d a r d fence by

33%.

The maximuni p e r r n l s s i b l e wind ve l o c i t y w i th t h e p e r r n i s s i b l e bending s t r e s s f o r p i n e of 120 kp/cni2 i s ,

For a s t a n d a r d f e n c e i t i s

When t h e wind v e l o c i t y i s g r e a t e r t h a n 11 nJsec t h e f e n c e s must b e

e i t h e r r e i n f o r c e d by d i a g o n a l members, a s we d i d i n t h e e x p e r i m e n t a l s e c t i o n , o r s t r e n g t h e n e d by a t t a c h i n g two a d d i t i o n a l s l a t s t o t h e two o u t e r v e r t i c a l s l a t s up t o 2/3 o f t h e i r h e i g h t .

I n

t h e w i n t e r of 1953-54 two methocls o f snow c o n t r o l u s i n g t h e new t y p e of f e n c e w i l l be t e s t e d on a p o r t i o n of t h e Toniskls r a i l r o a d :

1. Movement o f t h e f e n c e when i t h a s been f i l l e d i n up t o t h e t o p o f t h e snow w a l l and u s i n g

a

r e i n f o r c e d c o n s t r u c t i o n .

2. R a i s i n g t h e f e n c e on p o s t s a s t h e snow w a l l grows. In t h i s c a s e a d d i t i o n a l r e i n f o r c e m e n t of t h e f e n c e w i l l n o t b e r e q u i r e d .

During t h e t e s t i t i s i n t e n d e d a l s o t o e s t a b l i s h t h e b e s t d i s t a n c e of t h e f e n c e from t h e road b e i n g p r o t e c t e d and t o e l u c i d a t e t h e f u n c t i o n o f t h e new f e n c e when t h e wind i s blowing a t a n a n g l e .

R e s u l t s

The s u g g e s t i o n of t h e All-Union Research I n s t i t u t e of R a i l r o a d T r a n s p o r t and t h e Transport-Power I n s t i t u t e o f t h e West S i b e r i a n F i l i a l o f t h e Academy of S c i e n c e s USSR f o r improving t h e o p e r a t i o n of snow f e n c e s g r e a t l y d e c r e a s e s t h e number of t i m e s t h e f e n c e has t o be moved i n a r e a s s u b j e c t t o e x t e n s i v e d r i f t i n g .

The f e n c e recommended by t h e Transport-Power I n s t i t u t e p r o v i d e s some economy i n m a t e r i a l and makes i t p o s s i b l e t o u s e lumber m i l l waste p r o d u c t s e x t e n s i v e l y .

The u s e of f e n c e s w i t h iniproved snow c o n t r o l p r o p e r t i e s can reduce t h e t o t a l expense o f snow c o n t r o l and a l s o f a c i l i t a t e c o n t i n u o u s o p e r a t i o n of r a i l r o a d s through t h e w i n t e r , which i s p a r t i c u l a r l y i m p o r t a n t f o r r a i l r o a d s of t h e Ural and West S i b e r i a n r e g i o n s .

1. Antonov,

F.I.

Nadezhnaya s n c g o z a s h c h i t a

-

osnova s n e g o b o r l b y ( ~ e l i a b l e snow f e n c i n i s t h e b a s i s o f snow c o n t r o l . ) . Z h e l e z n o d o r o z h n y i T r a n s p o r t , fi10)

,

1350.

2. Antonov, F. I . , Pi-yadko, V . S . and M c l l n i k , I . M . B o r t b a s o snezhnymi

zanosanii na zl~elcznodorozhnom t r a n s p o r t e ( ~ornba t t i n g snow c l r i f ts i n r a i l r o a d transpo1.t )

.

Trudy T3NIIy ( 5 9 ) , 1951.

3 .

B o g o r o d e t s l c l l , A . A . Vetrovye n a g r u z k i na moste (Wind l o a d s on b r i d g e s ) , 1946.

4 . B y a l o b z h e s k i i , G.V. P u t 1 povysheniya ekononiichnosti s n e g o z a s h c h l t n y k h y s t r o i s t v (Ways o f making snow f e n c e s more e c o n o m i c a l ) .

S t r o i t e l ' s t v o Dorog, ( I ) , 1950.

5 .

D a n o v s k i i , L.M. S n e g o z a s h c h i t n y e z a b o r y na dorogakh Zapadnoi S i b i r i (Snow f e n c e s on West S i b e r i a n r o a d s ) , 1950.

6 .

S a r s a t s k i k h , P.I. Za r a t s l o n a l l n u y u s n e o z a s h c h i t u

o or

s e n s i b l e snow c o n t r o l ) . S t r o l t e l l s t v o Dorog, (27, 1947.

7.

M e l l n i k ,

D.M.

Ozakonakh p e r e n o s a s n e g a i i k h l s p o l t z o v a n i y a

v

s n e g o b o r t b e (On laws g o v e r n i n g snow t r a n s f e r and t h e i r a p p l i c a t i o n t o snow

c o n t r o l ) . Tekhnika Zheleznykh Dorog, ( l l ) , 1952.

T a b l e I Average

1

0.495 Open f i e l d v e l o c i t y

w

nJsec a t t h e h e i & t of 1 rn 1 0 'min w 0.539

Type o f f e n c c

S t a n d a r d

With r e d u c e d d e n s i t y i n

lower p a r t

V o l u~.ic- oi' snow c l c \ ~ ) o n i t a t f ' c n c e s i n rn3/prn

on t,ii(: f o l 1 owing c i a t c s 'i'ranof'er o f f c n c b r e q u i r e d Fig. 1 I\i'orJl;la 1 f e n c e Wind d i r e c t i o n

-

--

\.

--

I--.\-. _ _ - r s m ~ C e m ~t 12 e 4 o 4 s rr 18 20 14 71 JL I I D 4 r M R II r n A Fig. '2 Snow d e p o s i t i o n a t a n o r ~ i a l f e n c e

/uo L o c a t i o n o f c e o c c 1 0 8 d 4 ~ # 2 4 6 8 N 1 2 / 1 / 6 I B 2 4 n i ~ l 8 n ~ e from fence ds f a c f d r o f t h e i r height F i g . :j

C u r v e s s h o w i n g wind v e l o c i t i e s from wind t u n n e l d a t a a n d anernor~~e t e r rr~easurcrnen t s

Fig.

4

F e n c e w i t h reduced d e n s i t y

Wind A i r c c f i o h

!,E

-

Snow d e p o s i t a t fences w i t h reduced d e n s i t y i n t h e lower p a r t