Defence Work at Baird Avalanche, Canadian Pacific Railway, Mountain Subdivision, Mile 97.4

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Publisher’s version / Version de l'éditeur:

Technical Note (National Research Council of Canada. Division of Building Research), 1959-12-01

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Defence Work at Baird Avalanche, Canadian Pacific Railway, Mountain Subdivision, Mile 97.4

Schaerer, P. A.

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DIVISION OF BUILDING RESEARCH

NATIONAL RESEARCH COUNCIL OF CANADA

TEClHIN II CAlL

NOTJE

INo.

f82

NOT FOR PUBLICATION FOR INTERNAL USE

-,-P=R=EP:-<A;.:.:.R:,.=E=D,---=-F=O:..>..R A.It\. Joplin, Division Engineer, C.P.R., Revelstoke, B.C.

SUBJECT

PREPARED BY P. Soheerer CHECKED BY LWG APPROVED BY RFL

DATEDeoember

1959

e.

Defence Work at Baird Avalanche, Canadian Pacifio

Railway, Mountain SUbdivislon,llile

97.4.

In the summer of

1959,

Mr.

A.F. Joplin, C.P.R. Division

Engineer at Revelstoke, suggested that earth mouads should be

con-structed for avalanche defence in the path of Baird Avalanche. He

asked the author of this note for advice on the location and size

of the mounds. The location was studied in the tield at the end of

Ootober

1959

and a project for earth mounds was designed.

Action of earth mounds

Earth mounds are braking structures, acting as obstacles in

the avalanche path. The mounds slow down the avalanches, caUSing'

them 1;'ost'op either 'betwe'en themoundsorimmedlate'iybeyond them •.

ThebestJ.octtlon eff mounds is on a 'flat section of the avalanohe

path, where the avalanche w111 probably have a low speed.

The majority of the avalanches in the Baird Avalanche path

stop on the 10ng creek'--ran above the ra 1lway grade. Large

avalanches, however; do not stop completely but slide over the high

and steeply cut bank down to the railway traok. The snow masses'

covering the traok are frequently large enough to hold up tht rail

traffic. Earth mounds, plaoed at the lower end of the fan, ｾｯｵｬ､

retain most of the avalanche snow that is now deposited on the track.

In general, earth mounds are suitable for slopes with an

inclination of less truln 20 degrees. On mountain sides steeper than

20 degrees, the mounds require long slopes in order to be high

enough. In such cases the avalanche may have a speed too high to

be effeotively reduoed by the obstaoles.

The slope angle at the Baird Avalanche is 21 degrees at the

location of the mounds, and

23

degrees on the slope above the

mounds. ｾｮ spite of this high slope angle, the oonstruction

or

the

mounds is1

reoommended for the following reasons:

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---·e

2

-1) Most of the avalanohes to be stopped are of heavy wet

snow and the snow masses are rather small; even small mounds have a good effeot on this kind of avalanohe.

2) The avalanohe ｦｾ is long, therefore the majority of the

a-valanohes will have been slowed down oODs-iderably by the time they

reaoh the mounds. Only small obstaoles are therefore required to

bring them to a full stop.

The proposed mounds will not retain eve?"'! ,,-val nohe. There

are fast avalanohes of dry snow that will not be stopped completely

between the mounds, but the mounds wou1.d retain 11 gI-eat deal of the

snow and the snow deposit on the railway traok should be rather small.

Construction of the mounds

Figure I shows the location of the mounds and a oroBs-section

of the proposed mounds along the original ground line. The best

method for building the mounds will be by bulldozer. A special

aooess road will have to be built from the railway track to the looation of the mounds.

The height of the mounds (12 feet,

15

feet,

20

feet) Is

measured in vertioa1 direotion from the original ground level to

the top of the mO\Uld. The soil should be exoavated around the

mounds and on the uphill side for the oonstruotion of the fll1.

The final height of the mounds will therefore be higher. The slope

on the uphill faoe is 2:1. A steeper slope has a ｢･ｾ･ｲ stopping

effect on the avalanohes, but 2:1 is the maximum slope that oan be

built by bulldozers. The slope on the downhill faoe has an ngle

of repose of approximately

1 1/4:1.

A new cpeek bed must be built

between the moundso The growth

ot

_{plants (grass, brush) on the}

mounds should be promoted, in order to proteot the mounds from erosion.

750

cu. yd.

1800

cu. yd.

3300 au.

yd.

5850

cu. yd.

The estimated earth quantities are:

3

mounds 12 feet high at

250

cu. yd.

4

mounds

15

feet high at

450

cu. yd.

3 mounds 20 feet high at 1100 eu. yd.

Total

It is estimated that with a bulldozer Caterpillar

D7,

approximately 120 hours would be required for the oonstruotion of

the mounds. The oonstruotion of the access road is not inoluded in

this estimate6

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3

-Future ｯ｢ｳ･ｲｶ｡ｾｩｯｮｳ and adjustments

During the winter of

1959/1960

the avalanohe survey orew tram

ｾｨ･ｄ･ｾｲｴｭ･ｮｴ of Publio Works will observe the looation and depth

of the avalanches. The observations will indicate whether the

designed mounds would have been effeotive during that ｷｩｮｴ･ｲｾ Any

ohanges to the design of the mound defence network based on the

1959-60

observations can be made in the spring of ＱＹＶＰｾ

After the mounds are oompleted, experienoe may show that the

course of the avalanohes haa ohanged. It might happen that the

mounds stop several avalanches during a winter and sno piles up on

the mounds. Later avalanohes would then be diverted to the side of

this snow pile and might reach the railway on either side of the

present patho More mounds would have to be built to either side if

this unf vourable effeot were observed.

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---OT"fAWA DIVISION OF BUiLDING RESEARCH. NATIONAL RESEARCH COUNCIL CANA

4 MOUNDS, 15 FE ET

HIGHER THAN ORIG.

-0 GROUND

3 MOUNDS, 12 F:EE!

HJl;HER-H-t-Aj\J- OR IG GROUND

3 MOUNDS, 20 FEET

HIGHER THAN ORIG.

GROUND

-

_I{) <Xl -o ｾ I" :: 100' POPL AR TREE

WITH RED FLAG

PLAN OF EARTH MOUNDS

I

-24--I

TO GLAC IE R

==========================-TO REVELSTOKE RAILWAY

DEFENSE WORK BAIRD AVALANCHE

CPR MOUNTAIN SUBDIVISION MILE 97·4

DR.t>,WING No. BR 2020 85' ＨｪｾｔｅＺｎｾｖＮ 2615 SCALE BY P. SCHAERER 110' M'PHOV[[' 60' I":: 50'

TEC HNICAL NOTE CROSS SECTION X-X

DRAWN M M B.