雪氷チーム

Snow and Ice Research Team

吹き払い柵の防雪機能に関する研究
Study on the Snow Control Performance of Blower Snow Fences
北海道内の道路では、吹雪による視程障害が多く発生しており、この対策として防雪柵等の整備が行われてきました。吹き払い柵は、２車線道路向けに開発された路側設置型の防雪柵で、基本的に用地取得が不要なため、視程障害への対策に多く用いられています。
しかし、積雪や吹きだまりにより下部間隙が埋まった場合には防雪機能が大幅に低下することが指摘されており、防雪機能については定量的に明らかとはなっていません。このため、寒地土木研究所では、吹き払い柵の防雪機能の定量化に向けて、実物大フィールド実験や風洞実験を行っています。
Snow fences and other snow control facilities have been developed and installed in Hokkaido, where blowing-snow-induced visibility hindrance often occurs on roads. A blower
snow fence is a snow fence that was developed for installation along two-lane roads. It has frequently been employed to mitigate poor visibility, because installation is basicallypossible on the existing right-of-way without extra land acquisition. However, it has been pointed out that when the bottom gap at the base of the fence is buried by snowdrift orother snow cover, the snow control performance greatly decreases. Quantitative clarification of the fence’s snow control performance has not been done. The Civil Engineering
Research Institute for Cold Region has been conducting full-scale field experiments and wind tunnel experiments on blower snow fences to quantify its snow control performance.

吹き払い柵の特徴

実物大フィールド実験●傾斜した複数の防雪板により構成され、下部に高さ１m程度の隙間(下部間隙)を持つ防雪柵です。

石狩吹雪実験場内の設置した実物の吹き払い柵を用い、積雪の深さが防雪機能に与える影響を調査しています。
これまでの調査により、積雪が少ない場合には下部間隙から吹き出す強風(現地の風速の約1.8倍程度)により吹き払い効果を発揮しますが、積雪が深くなるに従い、防雪機能が低下することが判りました。積雪の多い地域への適用には注意が必要です。

Full-scale field experiment●下部間隙から吹き出す強風で路上の雪を吹き払います。
●路側に設置可能なため広く普及しています。
- The blower snow fence is a snow control fence made up of multiple slanted
snowbreak fins with about 1 m of bottom gap between the lowest part of thestructure and the ground surface.
- Strong winds blowing through the bottom gap blow snow off the road.
- Such fences are widely used because they can be installed at the immediateroadside.
吹き払い柵の防雪機能のイメージ

Diagram of how a blower snow fence controls snow
下部間隙
Bottom gap

吹き払い柵
Blower snow fence

The influence of snow depth on snow control performance has
been investigated at the Ishikari Blowing Snow Test Field byusing full-scale blower snow fences. Surveys and otherinvestigations revealed that the blower snow fence is effectivein blowing the snow off the road when the snow depth is low
and the wind that blows through the bottom gap of the fence isfast (i.e., about 1.8 times faster than wind measured at open
areas of the subject location); however, the snow control
performance decreases with increases in snow depth. Careshould be taken when considering the application of blower
snow fences in areas with deep snow cover.
Snow depth measuring
equipment

Wind velocity surveyof the subject area
吹き払い領域
Target area for snow control

Full-scale field experiment

風下側1.5m地点

積雪深計

現地の風速調査

風向Wind direction▲実物大フィールド実験

風向風速計

Wind direction indicator,
anemometer

風y=1.751x

1550

基準点

Control point

Wind tunnel experiment
実物大フィールド実験の場合、現地の気象条件により観測する機会が限られます。
より多様な条件での防雪機能を調べるため、風洞実験による調査を行っています。これまでの調査により、下部間隙の閉塞が50％までの場合、十分な防雪機能を確保できるものの、80％以上閉塞した場合には、風に逆流を生じるため、防雪機能が低下することが判りました。
三次元トラバース装置
3D traversing unit

1.5m

道路Road▲現地の風速と柵風下側の風速の比較

Comparison of wind velocity at an open space
vs. that immediately leeward of the fence

軸流送風機
Axial fan

風速比Wind speed ratio

Wind direction indicator,
anemometer
1.5m

Wind

風向風速計

0.5m

風2.5

Blower snow fence

3.3m

Snowdrift created when the bottom gap
is blocked

風洞実験

吹き払い柵 L=49m

1.0m

Blower snow fence▲下部間隙閉塞時の吹きだまり

柵高 Fence height▲吹き払い柵51015

基準点風速 (m/s)
Wind velocity at the control point

柵風下側の風速(積雪深 : 27cm)

柵風下側の風速調査

Wind velocity survey
at the leeward sideof the fence

高さ Height
0.5m
1.5m

1001.5m

Wind

1.5 m leeward of the fence

20風速 (m/s)
Wind velocity

Characteristics of the blower snow fenceWind velocity at the leeward of the fence(snow depth: 27 cm)
高さ Height
0.5m
1.5m

2.0

吹き払い効果あり

1.5
視程障害緩和効果あり

Effective in blowing away the snow

1.0 Effective in mitigating
visibility hindrance

0.50.0050100

基準点積雪深 (cm)Snow depth at the control point

150▲積雪深と柵風下側の風速比の関係

Relationship between the snow depth and the windspeed ratio immediately leeward of the fence

フィルター
FilterFor full-scale field experiments, chances for整流網observation are limited; they depend on theTurbulence-reducing
screens
weather conditions of the location. Wind tunnel
開放・回流切換部Open/closed circuit
experiments have been conducted toswitching section
逆流域
測定胴 Test section
Area of adverse wind
investigate the snow control performance of（W1200×H1200×L9000）
these fences under more varied conditions than
風速調整装置Windvelocity
those possible in field experiments.
control device
The investigations revealed that it is possible to
模型雪供給装置
空気圧縮機
Model snow
secure sufficient snow control performance whenCompressor
supply device
the bottom gap has a blockage of up to 50%; however,▲下部間隙閉塞率を変化させた▲柵風下側の気流分布(閉塞率100%の例)
Distribution of air currents immediately leeward of the fence▲風洞実験装置
when the bottom gap blockage equals or exceeds
風洞実験(閉塞率100%の例)(blockage rate of 100%)
Wind tunnel experiment apparatus
Wind tunnel experiment with80%, the snow control performance of the fence
various rates of bottom gap
decreases because of adverse winds.
blockage (blockage rate of 100%)

安全・快適

北の道Safe, pleasant driving on Northern Roads

独立行政法人土木研究所 寒地土木研究所

Incorporated Administrative Agency Public Works Research Institute Civil Engineering Research Institute for Cold Region